SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1133 AM CDT Mon Sep 09 2024 Valid 091700Z - 101200Z Minor modifications have been made to the ongoing forecast based on recent observations and model guidance. See the previous discussion for greater details. ..Wendt.. 09/09/2024 .PREV DISCUSSION... /ISSUED 0150 AM CDT Mon Sep 09 2024/ ...Synopsis... Broad trouhging over the Northwest should continue today as an embedded perturbation moves eastward over the northern Rockies. Southwesterly flow aloft is forecast to increase over much of the West as the broad trough slowly shifts east. At the surface, a cold front will move into the Rockies, bringing a cooler air mass to parts of the Northwest, but gusty winds to parts of the Cascades. A lee trough developing east of the Rockies will help support isolated dry thunderstorms over parts of WY and MT. Periods of stronger surface winds and low RH will support elevated to near-critical fire-weather conditions. ...Northwest and Great Basin.... Stronger flow aloft is expected to persist today over much of the Northwest and northern Great Basin. Surface winds should increase to 15-25 mph as momentum from aloft mixes down. Downsloping and mid-level drying should keep the air mass quite dry with diurnal RH minimums below 15% likely. Several hours of widespread elevated to near-critical fire-weather conditions are likely across the northern Sierra and Great Basin. Farther north, more moderate RH of 25-30% is expected beneath the upper trough and behind the cold front. Despite the arrival of a cooler Pacific air mass, downslope winds of 15-25 mph should overlap with dry fuels and pockets of lower RH during the day. Overlapping with recent lightning and fire activity, a few hours of elevated to near-critical conditions are possible in the lee of the Cascades as winds increase. ...Northern Rockies... Stronger westerly flow head of the embedded shortwave will aid in deepening a lee trough east of the Rockies. Westerly surface winds should strengthen in turn, supporting pockets of downslope winds of 15-25 mph across parts of MT and WY. With hot temperatures and little recent rainfall, afternoon RH values should remain quite low, generally below 20%. Increasing winds, receptive fuels, and persistent dry conditions should support several hours of elevated to near critical fire-weather conditions over parts of the northern Rockies. ...Dry Thunder... Isolated, high-based thunderstorms appear likely over parts of the Rockies (mainly WY and MT) today ahead of the shortwave trough. Weak buoyancy, and PWATs of 0.5 to 0.7 inches, atop dry and well-mixed low levels will support poor precipitation efficiency and the potential for strong outflow winds. At least isolated storms are expected over areas of receptive fuels. Thus, dry lightning ignitions are possible, especially across parts of north-central WY, where storm coverage appears greatest. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Mon Sep 09 2024 Valid 091630Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NEW YORK... ...SUMMARY... Isolated damaging winds may occur this afternoon across parts of New York. ...New York... Within large-scale upper troughing over the Northeast and eastern Canada, an embedded shortwave trough over southern Ontario and the upper Great Lakes will continue to move across the Northeast this afternoon and evening. Ascent associated with this shortwave trough and related mid-level jet is supporting isolated thunderstorms across southern Ontario and vicinity. This activity will spread east-southeastward this afternoon across parts of NY. The airmass over this region should become only weakly unstable as filtered daytime heating occurs, with poor mid-level lapse rates, persistent cloud cover, and modest low-level moisture limiting destabilization. Still, gradually increasing west-northwesterly winds at low/mid levels will foster around 25-35 kt of deep-layer shear. This should support modest thunderstorm organization, with multicells/small clusters potentially evolving along and downstream of Lake Ontario. Isolated strong to damaging winds should be the main threat with this convection as it moves across much of NY this afternoon and early evening, before eventually weakening with eastward extent with the loss of daytime heating. ...Northern/Central Rockies and High Plains... Isolated to widely scattered thunderstorms should develop this afternoon over portions of the northern/central Rockies as a weak shortwave trough continues eastward. Low-level moisture and related instability are both expected to remain rather meager into the High Plains, which should limit updraft intensities. Still, isolated strong/gusty winds may occur with this high-based activity across parts of MT/WY where low-level lapse rates can become steepened. Greater low-level moisture is present farther east into the Dakotas, along/east of a weak surface low/trough. But, increasing low/mid-level temperatures and a strong cap should generally inhibit thunderstorm development through much of the day with eastward extent across the northern/central Plains. ..Gleason/Halbert.. 09/09/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1126 AM CDT Mon Sep 09 2024 Valid 091630Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF NEW YORK... ...SUMMARY... Isolated damaging winds may occur this afternoon across parts of New York. ...New York... Within large-scale upper troughing over the Northeast and eastern Canada, an embedded shortwave trough over southern Ontario and the upper Great Lakes will continue to move across the Northeast this afternoon and evening. Ascent associated with this shortwave trough and related mid-level jet is supporting isolated thunderstorms across southern Ontario and vicinity. This activity will spread east-southeastward this afternoon across parts of NY. The airmass over this region should become only weakly unstable as filtered daytime heating occurs, with poor mid-level lapse rates, persistent cloud cover, and modest low-level moisture limiting destabilization. Still, gradually increasing west-northwesterly winds at low/mid levels will foster around 25-35 kt of deep-layer shear. This should support modest thunderstorm organization, with multicells/small clusters potentially evolving along and downstream of Lake Ontario. Isolated strong to damaging winds should be the main threat with this convection as it moves across much of NY this afternoon and early evening, before eventually weakening with eastward extent with the loss of daytime heating. ...Northern/Central Rockies and High Plains... Isolated to widely scattered thunderstorms should develop this afternoon over portions of the northern/central Rockies as a weak shortwave trough continues eastward. Low-level moisture and related instability are both expected to remain rather meager into the High Plains, which should limit updraft intensities. Still, isolated strong/gusty winds may occur with this high-based activity across parts of MT/WY where low-level lapse rates can become steepened. Greater low-level moisture is present farther east into the Dakotas, along/east of a weak surface low/trough. But, increasing low/mid-level temperatures and a strong cap should generally inhibit thunderstorm development through much of the day with eastward extent across the northern/central Plains. ..Gleason/Halbert.. 09/09/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Mon Sep 09 2024 Valid 091300Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF NEW YORK... ...SUMMARY... Isolated damaging thunderstorm gusts are possible in parts of New York. ...Synopsis... Mid/upper-level flow will become more zonal across most of the northwestern and north-central CONUS, as a series of embedded shortwave troughs penetrates/flattens antecedent ridging over the Intermountain West and central/northern Rockies. Downstream, a substantial cyclone -- initially centered near the southwestern edge of Labrador -- anchors mean troughing that extends southwestward down the Appalachians. The cyclone will eject northeastward over Labrador through the period. In its southwestern quadrant, a shortwave trough was apparent in moisture-channel imagery over northeastern ON, approaching Georgian Bay and the neck of ON. This feature should move southeastward to the upper St. Lawrence Valley, eastern Lake Ontario and western NY by 00Z, then across southern New England and offshore from the northern Mid-Atlantic Coast overnight. The 11Z surface analysis showed a weak cold front from southern QC, through a frontal-wave low over northern Lake Huron, then across northern parts of WI/MN. The low should move east-southeastward toward Lake Ontario and weaken through the day, while the cold front and associated veering wind shift cross the remainder of ON and start moving into NY. The front should cross the remainder of NY and most of New England and PA overnight. An older, quasistationary front was drawn across north-central FL westward over north-central Gulf shelf waters, then bending southwestward into the western parts of the developing tropical cyclone in the western Gulf. Potential TC 6 -- now offshore from the Mexican Gulf Coast -- is forecast by NHC to organize into a tropical storm this period. Given the forecast track, intensity and wind radii, any developing favorable sector for supercells/tornadoes will remain well out in the Gulf day-1, and not an overland tornado concern until day 3, when a risk area has been introduced northeast/east of the forecast center track. See NHC advisories on this system for latest tropical watches/warnings, and path/strength forecasts. ...NY... Widely scattered to scattered thunderstorms are expected to move southeastward to eastward across the outlook area from early afternoon into early evening. Isolated damaging gusts, and perhaps a gust or two near severe limits, may occur from the most vigorous embedded cells. This convection will be related to a compact (mesoscale) but strong field of large-scale ascent preceding the shortwave trough, related to its progressive field of DCVA, and forcing in the left-exit region of a cyclonically curved speed max in the 250-500-mb layer. The UVV field likely is manifest already by convection now over Georgian Bay and vicinity, moving toward what should become a more unstable environment over the outlook area. Deep-layer mean lapse rates likely will never get steeper than about 6.5 C/km in this setting. Still, the combination of subtle cooling aloft, weak but sufficient boundary-layer moisture, and some diurnal heating ahead of the UVV field, should deepen the buoyant layer enough to yield pockets of 500-700 J/kg MLCAPE. Weak low-level shear, and 25-30 kt effective-shear magnitudes in forecast soundings, indicate activity should be multicellular. A shallow but well-mixed subcloud layer -- containing around 7 C/km lapse rates -- will support strong downdraft accelerations in some of the cores. ..Edwards/Kerr.. 09/09/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Mon Sep 09 2024 Valid 091300Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF NEW YORK... ...SUMMARY... Isolated damaging thunderstorm gusts are possible in parts of New York. ...Synopsis... Mid/upper-level flow will become more zonal across most of the northwestern and north-central CONUS, as a series of embedded shortwave troughs penetrates/flattens antecedent ridging over the Intermountain West and central/northern Rockies. Downstream, a substantial cyclone -- initially centered near the southwestern edge of Labrador -- anchors mean troughing that extends southwestward down the Appalachians. The cyclone will eject northeastward over Labrador through the period. In its southwestern quadrant, a shortwave trough was apparent in moisture-channel imagery over northeastern ON, approaching Georgian Bay and the neck of ON. This feature should move southeastward to the upper St. Lawrence Valley, eastern Lake Ontario and western NY by 00Z, then across southern New England and offshore from the northern Mid-Atlantic Coast overnight. The 11Z surface analysis showed a weak cold front from southern QC, through a frontal-wave low over northern Lake Huron, then across northern parts of WI/MN. The low should move east-southeastward toward Lake Ontario and weaken through the day, while the cold front and associated veering wind shift cross the remainder of ON and start moving into NY. The front should cross the remainder of NY and most of New England and PA overnight. An older, quasistationary front was drawn across north-central FL westward over north-central Gulf shelf waters, then bending southwestward into the western parts of the developing tropical cyclone in the western Gulf. Potential TC 6 -- now offshore from the Mexican Gulf Coast -- is forecast by NHC to organize into a tropical storm this period. Given the forecast track, intensity and wind radii, any developing favorable sector for supercells/tornadoes will remain well out in the Gulf day-1, and not an overland tornado concern until day 3, when a risk area has been introduced northeast/east of the forecast center track. See NHC advisories on this system for latest tropical watches/warnings, and path/strength forecasts. ...NY... Widely scattered to scattered thunderstorms are expected to move southeastward to eastward across the outlook area from early afternoon into early evening. Isolated damaging gusts, and perhaps a gust or two near severe limits, may occur from the most vigorous embedded cells. This convection will be related to a compact (mesoscale) but strong field of large-scale ascent preceding the shortwave trough, related to its progressive field of DCVA, and forcing in the left-exit region of a cyclonically curved speed max in the 250-500-mb layer. The UVV field likely is manifest already by convection now over Georgian Bay and vicinity, moving toward what should become a more unstable environment over the outlook area. Deep-layer mean lapse rates likely will never get steeper than about 6.5 C/km in this setting. Still, the combination of subtle cooling aloft, weak but sufficient boundary-layer moisture, and some diurnal heating ahead of the UVV field, should deepen the buoyant layer enough to yield pockets of 500-700 J/kg MLCAPE. Weak low-level shear, and 25-30 kt effective-shear magnitudes in forecast soundings, indicate activity should be multicellular. A shallow but well-mixed subcloud layer -- containing around 7 C/km lapse rates -- will support strong downdraft accelerations in some of the cores. ..Edwards/Kerr.. 09/09/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0351 AM CDT Mon Sep 09 2024 Valid 121200Z - 171200Z ...DISCUSSION... ...Thursday/Day 4 to Saturday/Day 6... A tropical cyclone is forecast to move slowly northward through the lower to mid Mississippi Valley from Thursday to Saturday. A tornado threat will be possible to the east of the center across much of the central Gulf Coast region on Thursday. Model forecasts suggest that the tornado threat could shift northward into the Tennessee Valley on Friday. On Saturday, uncertainty is considerable concerning the location of any tropical cyclone remnants. If current solutions are reasonably close, then a tornado threat would be possible in the Southeast, potentially from the southern Appalachians into the Carolinas. ...Sunday/Day 7 and Monday/Day 8... Mid-level flow is forecast to be relatively weak across the central and eastern U.S. on Sunday and Monday. The diffuse pattern and weak deep-layer shear across most of the U.S. suggests that the severe potential will remain low. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0351 AM CDT Mon Sep 09 2024 Valid 121200Z - 171200Z ...DISCUSSION... ...Thursday/Day 4 to Saturday/Day 6... A tropical cyclone is forecast to move slowly northward through the lower to mid Mississippi Valley from Thursday to Saturday. A tornado threat will be possible to the east of the center across much of the central Gulf Coast region on Thursday. Model forecasts suggest that the tornado threat could shift northward into the Tennessee Valley on Friday. On Saturday, uncertainty is considerable concerning the location of any tropical cyclone remnants. If current solutions are reasonably close, then a tornado threat would be possible in the Southeast, potentially from the southern Appalachians into the Carolinas. ...Sunday/Day 7 and Monday/Day 8... Mid-level flow is forecast to be relatively weak across the central and eastern U.S. on Sunday and Monday. The diffuse pattern and weak deep-layer shear across most of the U.S. suggests that the severe potential will remain low. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Mon Sep 09 2024 Valid 111200Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL GULF COAST REGION.... ...SUMMARY... An isolated tornado threat is expected to develop across the central Gulf Coast Wednesday and Wednesday night. ...Central Gulf Coast... A tropical storm is forecast by the National Hurricane Center to develop across the western Gulf of Mexico today, and move north-northeastward toward the coast of Louisiana on Tuesday and Wednesday. Although uncertainty is substantial concerning landfall and intensity, the system is forecast to become a hurricane and move onshore into southwestern Louisiana early Wednesday evening. If this were to happen, an isolated tornado threat would be expected across much of the central Gulf Coast from Wednesday afternoon into the overnight period. Forecast soundings near the location of expected landfall have 0-3 km storm-relative helicity in the 300 to 500 m2/s2 range, with strong low-level shear extending eastward across much of the central Gulf Coast region. If the current scenario plays out as expected, an isolated tornado threat would develop, from near the landfall location eastward across southern Mississippi, southern Alabama into the western Florida Panhandle. The threat would continue throughout the central Gulf Coast region through late in the period, as the system moves inland into the lower Mississippi Valley. ..Broyles.. 09/09/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0223 AM CDT Mon Sep 09 2024 Valid 111200Z - 121200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL GULF COAST REGION.... ...SUMMARY... An isolated tornado threat is expected to develop across the central Gulf Coast Wednesday and Wednesday night. ...Central Gulf Coast... A tropical storm is forecast by the National Hurricane Center to develop across the western Gulf of Mexico today, and move north-northeastward toward the coast of Louisiana on Tuesday and Wednesday. Although uncertainty is substantial concerning landfall and intensity, the system is forecast to become a hurricane and move onshore into southwestern Louisiana early Wednesday evening. If this were to happen, an isolated tornado threat would be expected across much of the central Gulf Coast from Wednesday afternoon into the overnight period. Forecast soundings near the location of expected landfall have 0-3 km storm-relative helicity in the 300 to 500 m2/s2 range, with strong low-level shear extending eastward across much of the central Gulf Coast region. If the current scenario plays out as expected, an isolated tornado threat would develop, from near the landfall location eastward across southern Mississippi, southern Alabama into the western Florida Panhandle. The threat would continue throughout the central Gulf Coast region through late in the period, as the system moves inland into the lower Mississippi Valley. ..Broyles.. 09/09/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0151 AM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z ...Synopsis... Broad troughing over the Northwest is forecast to gradually intensify Tuesday as a stronger shortwave and mid-level jet approach from the eastern Pacific. Falling heights and increasing flow aloft will move inland, supporting the potential for strong surface winds and low humidity over parts of the Northwest and Great Basin. ..Great Basin... Fire weather concerns will increase on Tuesday with the approach of the strong trough/mid-level jet. Initially weak surface winds will intensify over northwest and southern Nevada to 15-25 mph as flow aloft increases. Several hours of elevated to locally critical fire-weather conditions are likely as the stronger surface winds develop with a dry air mass with RH values below 20%. Fuels are driest across parts of the northern Great Basin and ID where rainfall has been sparse. However, fuels farther south in NV and CA remain sufficiently dry, and with stronger winds, elevated to near critical conditions are likely. ...Cascades and Columbia Gorge... Increasing mid-level winds will combine with a strong onshore pressure gradient to drive 15-20 mph winds through the Gorge and the western Columbia Basin along with RH potentially near 15%. The duration of breezy and somewhat dry conditions may be somewhat limited, but elevated to briefly critical fire weather may occur on Tuesday. ..Lyons.. 09/09/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0151 AM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z ...Synopsis... Broad troughing over the Northwest is forecast to gradually intensify Tuesday as a stronger shortwave and mid-level jet approach from the eastern Pacific. Falling heights and increasing flow aloft will move inland, supporting the potential for strong surface winds and low humidity over parts of the Northwest and Great Basin. ..Great Basin... Fire weather concerns will increase on Tuesday with the approach of the strong trough/mid-level jet. Initially weak surface winds will intensify over northwest and southern Nevada to 15-25 mph as flow aloft increases. Several hours of elevated to locally critical fire-weather conditions are likely as the stronger surface winds develop with a dry air mass with RH values below 20%. Fuels are driest across parts of the northern Great Basin and ID where rainfall has been sparse. However, fuels farther south in NV and CA remain sufficiently dry, and with stronger winds, elevated to near critical conditions are likely. ...Cascades and Columbia Gorge... Increasing mid-level winds will combine with a strong onshore pressure gradient to drive 15-20 mph winds through the Gorge and the western Columbia Basin along with RH potentially near 15%. The duration of breezy and somewhat dry conditions may be somewhat limited, but elevated to briefly critical fire weather may occur on Tuesday. ..Lyons.. 09/09/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Mon Sep 09 2024 Valid 091200Z - 101200Z ...Synopsis... Broad trouhging over the Northwest should continue today as an embedded perturbation moves eastward over the northern Rockies. Southwesterly flow aloft is forecast to increase over much of the West as the broad trough slowly shifts east. At the surface, a cold front will move into the Rockies, bringing a cooler air mass to parts of the Northwest, but gusty winds to parts of the Cascades. A lee trough developing east of the Rockies will help support isolated dry thunderstorms over parts of WY and MT. Periods of stronger surface winds and low RH will support elevated to near-critical fire-weather conditions. ...Northwest and Great Basin.... Stronger flow aloft is expected to persist today over much of the Northwest and northern Great Basin. Surface winds should increase to 15-25 mph as momentum from aloft mixes down. Downsloping and mid-level drying should keep the air mass quite dry with diurnal RH minimums below 15% likely. Several hours of widespread elevated to near-critical fire-weather conditions are likely across the northern Sierra and Great Basin. Farther north, more moderate RH of 25-30% is expected beneath the upper trough and behind the cold front. Despite the arrival of a cooler Pacific air mass, downslope winds of 15-25 mph should overlap with dry fuels and pockets of lower RH during the day. Overlapping with recent lightning and fire activity, a few hours of elevated to near-critical conditions are possible in the lee of the Cascades as winds increase. ...Northern Rockies... Stronger westerly flow head of the embedded shortwave will aid in deepening a lee trough east of the Rockies. Westerly surface winds should strengthen in turn, supporting pockets of downslope winds of 15-25 mph across parts of MT and WY. With hot temperatures and little recent rainfall, afternoon RH values should remain quite low, generally below 20%. Increasing winds, receptive fuels, and persistent dry conditions should support several hours of elevated to near critical fire-weather conditions over parts of the northern Rockies. ...Dry Thunder... Isolated, high-based thunderstorms appear likely over parts of the Rockies (mainly WY and MT) today ahead of the shortwave trough. Weak buoyancy, and PWATs of 0.5 to 0.7 inches, atop dry and well-mixed low levels will support poor precipitation efficiency and the potential for strong outflow winds. At least isolated storms are expected over areas of receptive fuels. Thus, dry lightning ignitions are possible, especially across parts of north-central WY, where storm coverage appears greatest. ..Lyons.. 09/09/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0150 AM CDT Mon Sep 09 2024 Valid 091200Z - 101200Z ...Synopsis... Broad trouhging over the Northwest should continue today as an embedded perturbation moves eastward over the northern Rockies. Southwesterly flow aloft is forecast to increase over much of the West as the broad trough slowly shifts east. At the surface, a cold front will move into the Rockies, bringing a cooler air mass to parts of the Northwest, but gusty winds to parts of the Cascades. A lee trough developing east of the Rockies will help support isolated dry thunderstorms over parts of WY and MT. Periods of stronger surface winds and low RH will support elevated to near-critical fire-weather conditions. ...Northwest and Great Basin.... Stronger flow aloft is expected to persist today over much of the Northwest and northern Great Basin. Surface winds should increase to 15-25 mph as momentum from aloft mixes down. Downsloping and mid-level drying should keep the air mass quite dry with diurnal RH minimums below 15% likely. Several hours of widespread elevated to near-critical fire-weather conditions are likely across the northern Sierra and Great Basin. Farther north, more moderate RH of 25-30% is expected beneath the upper trough and behind the cold front. Despite the arrival of a cooler Pacific air mass, downslope winds of 15-25 mph should overlap with dry fuels and pockets of lower RH during the day. Overlapping with recent lightning and fire activity, a few hours of elevated to near-critical conditions are possible in the lee of the Cascades as winds increase. ...Northern Rockies... Stronger westerly flow head of the embedded shortwave will aid in deepening a lee trough east of the Rockies. Westerly surface winds should strengthen in turn, supporting pockets of downslope winds of 15-25 mph across parts of MT and WY. With hot temperatures and little recent rainfall, afternoon RH values should remain quite low, generally below 20%. Increasing winds, receptive fuels, and persistent dry conditions should support several hours of elevated to near critical fire-weather conditions over parts of the northern Rockies. ...Dry Thunder... Isolated, high-based thunderstorms appear likely over parts of the Rockies (mainly WY and MT) today ahead of the shortwave trough. Weak buoyancy, and PWATs of 0.5 to 0.7 inches, atop dry and well-mixed low levels will support poor precipitation efficiency and the potential for strong outflow winds. At least isolated storms are expected over areas of receptive fuels. Thus, dry lightning ignitions are possible, especially across parts of north-central WY, where storm coverage appears greatest. ..Lyons.. 09/09/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1242 AM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are expected to develop on Tuesday across the Gulf Coast region and from the Four Corners northward into the north-central U.S. No severe threat is expected across the U.S. Tuesday or Tuesday night. ...DISCUSSION... A shortwave ridge will move eastward across the Great Lakes region on Tuesday, as an upper-level trough develops near the West Coast. Southwesterly mid-level flow will be in place from the Intermountain West into the central and northern Rockies. Isolated to scattered thunderstorms will be possible on Tuesday in the higher terrain from the vicinity of the Four Corners northward into the northern Rockies and northeastward into the upper Mississippi Valley. Additional storms will be possible along the Gulf Coast, near the northern edge of a moist airmass. No severe threat is expected across the U.S. on Tuesday and Tuesday night. ..Broyles.. 09/09/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1242 AM CDT Mon Sep 09 2024 Valid 101200Z - 111200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms are expected to develop on Tuesday across the Gulf Coast region and from the Four Corners northward into the north-central U.S. No severe threat is expected across the U.S. Tuesday or Tuesday night. ...DISCUSSION... A shortwave ridge will move eastward across the Great Lakes region on Tuesday, as an upper-level trough develops near the West Coast. Southwesterly mid-level flow will be in place from the Intermountain West into the central and northern Rockies. Isolated to scattered thunderstorms will be possible on Tuesday in the higher terrain from the vicinity of the Four Corners northward into the northern Rockies and northeastward into the upper Mississippi Valley. Additional storms will be possible along the Gulf Coast, near the northern edge of a moist airmass. No severe threat is expected across the U.S. on Tuesday and Tuesday night. ..Broyles.. 09/09/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Mon Sep 09 2024 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE EASTERN GREAT LAKES VICINITY... ...SUMMARY... Thunderstorms will be possible today over parts of the eastern Great Lakes, along the Gulf Coast, and from the Four Corners northward into the northern Plains. Isolated storms may produce damaging wind gusts over western and central New York State. ...Synopsis... A large upper ridge will remain in place over the Central CONUS flanked by broad trouging to the west and a lingering upper low over eastern Canada. Behind the upper low, a secondary embedded shortwave trough and speed max are forecast to move south out of western Ontario and over the Great Lakes, providing adequate lift for scattered thunderstorms over parts of the Northeast. To the west, scattered thunderstorms are likely over the Great Basin into the Four Corners, with a few thunderstorms possible over the Northern Plains ahead of the western US trough. Finally, scattered thunderstorms may also develop by afternoon peak heating along the Gulf Coast into FL and near the outer bands of PTC6. ...Great Lakes vicinity... As the aforementioned mid-level speed max approaches from southern Canada, shower and thunderstorm activity should begin to increase in coverage and intensity in the vicinity of Lakes Erie/Ontario, as well as over portions of northwestern NY State by mid morning. Limited, but adequate, surface moisture (dewpoints in the mid 50s to near 60 F), combined with daytime heating, and 500 mb temps of -18 to -20C will support weak destabilization (MLCAPE 500-700 J/kg) across parts of the lower Great Lakes and Northeast. Low-topped bands or clusters of predominately multicell storms are likely, and may briefly organize owing to increasing flow aloft aiding deep-layer shear to near 30 kt. Despite the weak buoyancy, fairly steep low-level lapse rates (~7 C/km) beneath the upper low, may support a few damaging gusts and instances of small hail with the strongest storms through the afternoon. Convection should eventually outrun the more robust buoyancy and weaken to the southeast into parts of northern PA and southern New England this evening. ..Lyons.. 09/09/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Mon Sep 09 2024 Valid 091200Z - 101200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE EASTERN GREAT LAKES VICINITY... ...SUMMARY... Thunderstorms will be possible today over parts of the eastern Great Lakes, along the Gulf Coast, and from the Four Corners northward into the northern Plains. Isolated storms may produce damaging wind gusts over western and central New York State. ...Synopsis... A large upper ridge will remain in place over the Central CONUS flanked by broad trouging to the west and a lingering upper low over eastern Canada. Behind the upper low, a secondary embedded shortwave trough and speed max are forecast to move south out of western Ontario and over the Great Lakes, providing adequate lift for scattered thunderstorms over parts of the Northeast. To the west, scattered thunderstorms are likely over the Great Basin into the Four Corners, with a few thunderstorms possible over the Northern Plains ahead of the western US trough. Finally, scattered thunderstorms may also develop by afternoon peak heating along the Gulf Coast into FL and near the outer bands of PTC6. ...Great Lakes vicinity... As the aforementioned mid-level speed max approaches from southern Canada, shower and thunderstorm activity should begin to increase in coverage and intensity in the vicinity of Lakes Erie/Ontario, as well as over portions of northwestern NY State by mid morning. Limited, but adequate, surface moisture (dewpoints in the mid 50s to near 60 F), combined with daytime heating, and 500 mb temps of -18 to -20C will support weak destabilization (MLCAPE 500-700 J/kg) across parts of the lower Great Lakes and Northeast. Low-topped bands or clusters of predominately multicell storms are likely, and may briefly organize owing to increasing flow aloft aiding deep-layer shear to near 30 kt. Despite the weak buoyancy, fairly steep low-level lapse rates (~7 C/km) beneath the upper low, may support a few damaging gusts and instances of small hail with the strongest storms through the afternoon. Convection should eventually outrun the more robust buoyancy and weaken to the southeast into parts of northern PA and southern New England this evening. ..Lyons.. 09/09/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 PM CDT Sun Sep 08 2024 Valid 090100Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are unlikely through tonight. ...01z Update... Evening water vapor imagery shows a prominent mid-level ridge remains in place over much of the CONUS, with surface high pressure favoring dry and quiescent weather over much of the country. To the east of the ridge, an upper low over the Northeast and eastern Canada is slowly filling. A cold front trailing south of the low has moved mostly offshore, but was supporting scattered showers and thunderstorms in the northern Gulf of Mexico and across parts of FL. Continued offshore flow ahead of the surface high moving slowly south and east should keep much of this activity offshore or confined to the immediate coast through the next 12 hours. Storms should gradually diminish in coverage and intensity through the remainder of the evening. To the west, weak and broader troughing is ongoing over the West Coast with an embedded shortwave perturbation crossing the northern Rockies. Monsoon moisture advection ahead of theses features is supporting scattered thunderstorms across much of the Intermoutnain West, into the northern Rockies and across much of the Desert Southwest. Scattered showers and thunderstorms appear likely to persist into this evening as the weak trough shifts slowly eastward, especially across parts of ID and the Great Basin where more clustering has occurred. Storms are predominately high-based in nature, owing to steep low-level lapse rates, hot temperatures and the limited monsoon moisture. This could support an occasional dry downburst with the more robust cores, mainly over parts of southern CA. However, limited deep-layer shear and weak overall buoyancy suggests these storms are unlikely to be meaningfully organized or persistent. Thus, will continue with severe probs less than 5%. Storms should begin to decrease in coverage this evening with the loss of diurnal heating and mid-level drying. Otherwise, the severe risk appears limited across much of the country. ..Lyons.. 09/09/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 PM CDT Sun Sep 08 2024 Valid 090100Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are unlikely through tonight. ...01z Update... Evening water vapor imagery shows a prominent mid-level ridge remains in place over much of the CONUS, with surface high pressure favoring dry and quiescent weather over much of the country. To the east of the ridge, an upper low over the Northeast and eastern Canada is slowly filling. A cold front trailing south of the low has moved mostly offshore, but was supporting scattered showers and thunderstorms in the northern Gulf of Mexico and across parts of FL. Continued offshore flow ahead of the surface high moving slowly south and east should keep much of this activity offshore or confined to the immediate coast through the next 12 hours. Storms should gradually diminish in coverage and intensity through the remainder of the evening. To the west, weak and broader troughing is ongoing over the West Coast with an embedded shortwave perturbation crossing the northern Rockies. Monsoon moisture advection ahead of theses features is supporting scattered thunderstorms across much of the Intermoutnain West, into the northern Rockies and across much of the Desert Southwest. Scattered showers and thunderstorms appear likely to persist into this evening as the weak trough shifts slowly eastward, especially across parts of ID and the Great Basin where more clustering has occurred. Storms are predominately high-based in nature, owing to steep low-level lapse rates, hot temperatures and the limited monsoon moisture. This could support an occasional dry downburst with the more robust cores, mainly over parts of southern CA. However, limited deep-layer shear and weak overall buoyancy suggests these storms are unlikely to be meaningfully organized or persistent. Thus, will continue with severe probs less than 5%. Storms should begin to decrease in coverage this evening with the loss of diurnal heating and mid-level drying. Otherwise, the severe risk appears limited across much of the country. ..Lyons.. 09/09/2024 Read more

No watches are valid as of Sun Sep 8 21:44:01 UTC 2024.