SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1247 AM CDT Sun Sep 08 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The organized severe-thunderstorm threat is expected to be low on Sunday. ...Synopsis and Discussion... A mature mid-latitude cyclone, embedded within larger upper troughing, is forecast to progress northeastward from southern Quebec into northeastern Quebec. Another shortwave trough is expected to move through the western portion of the parent upper troughing, dropping across western Ontario and the Upper Great Lakes Sunday evening into Monday morning. Isolated thunderstorms are possible with this second wave late Sunday night into early Monday morning. Evolution of these shortwaves will help maintain troughing across much of the eastern CONUS throughout the period. Farther west, upper ridging will gradually move eastward into the Plains while a low-amplitude shortwave trough moves through the Pacific Northwest and into the northern Rockies. At the surface, expansive high pressure centered over the Mid MS Valley will dominate the sensible weather from the Mid MS and OH Valleys into much of the central and southern Plains. This should keep any low-level moisture confined to the immediate Gulf Coast and FL Peninsula. A stationary front will likely extend from a low over the far western Gulf of Mexico northeastward through northern FL. Thunderstorms are possible in the vicinity of this boundary throughout the day, with the highest coverage expected over the northern/central FL Peninsula. Abundant cloud cover will limit heating across northern/central FL Peninsula, and lapse rates will be poor. However, mid-level flow around 40 kt may support enough vertical shear for a few more persistent/organized updrafts capable of damaging gusts. Even so, severe coverage is expected to remain less than 5%. Afternoon thunderstorms are expected again from the central High Plains into parts of the central/southern Rockies, Great Basin, and Southwest. High-based character of these storms could result in a few locally strong gusts. Isolated high-based thunderstorms are also possible from the interior Pacific Northwest into the northern Rockies as a shortwave trough progresses through the region. A few strong gusts are possible with these storms as well. In both of these areas, overall severe coverage is expected to remain less than 5%. ..Mosier/Lyons.. 09/08/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1247 AM CDT Sun Sep 08 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The organized severe-thunderstorm threat is expected to be low on Sunday. ...Synopsis and Discussion... A mature mid-latitude cyclone, embedded within larger upper troughing, is forecast to progress northeastward from southern Quebec into northeastern Quebec. Another shortwave trough is expected to move through the western portion of the parent upper troughing, dropping across western Ontario and the Upper Great Lakes Sunday evening into Monday morning. Isolated thunderstorms are possible with this second wave late Sunday night into early Monday morning. Evolution of these shortwaves will help maintain troughing across much of the eastern CONUS throughout the period. Farther west, upper ridging will gradually move eastward into the Plains while a low-amplitude shortwave trough moves through the Pacific Northwest and into the northern Rockies. At the surface, expansive high pressure centered over the Mid MS Valley will dominate the sensible weather from the Mid MS and OH Valleys into much of the central and southern Plains. This should keep any low-level moisture confined to the immediate Gulf Coast and FL Peninsula. A stationary front will likely extend from a low over the far western Gulf of Mexico northeastward through northern FL. Thunderstorms are possible in the vicinity of this boundary throughout the day, with the highest coverage expected over the northern/central FL Peninsula. Abundant cloud cover will limit heating across northern/central FL Peninsula, and lapse rates will be poor. However, mid-level flow around 40 kt may support enough vertical shear for a few more persistent/organized updrafts capable of damaging gusts. Even so, severe coverage is expected to remain less than 5%. Afternoon thunderstorms are expected again from the central High Plains into parts of the central/southern Rockies, Great Basin, and Southwest. High-based character of these storms could result in a few locally strong gusts. Isolated high-based thunderstorms are also possible from the interior Pacific Northwest into the northern Rockies as a shortwave trough progresses through the region. A few strong gusts are possible with these storms as well. In both of these areas, overall severe coverage is expected to remain less than 5%. ..Mosier/Lyons.. 09/08/2024 Read more

SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0736 PM CDT Sat Sep 07 2024 Valid 080100Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today, though a few strong gusts could accompany the more robust storms across the central High Plains and Lower Colorado River Valley vicinity. ...01Z Update... ...Northeast... General thunder was removed across the region given the scant buoyancy and limited land area ahead of the cold front across southern New England. A flash or two is still possible within the more cellular activity across western NY and PA. However, coverage is expected to be less than 10%. ...Elsewhere... Isolated thunderstorms remain possible along the immediate Gulf Coast and across the FL Peninsula tonight through tomorrow morning. Isolated to widely scattered thunderstorm are expected to continue from the central High Plains/central Rockies through much of AZ and the Lower CO River Valley. Highest coverage is expected over the Lower CO River Valley. A few stronger storms capable of hail and/or damaging wind gusts in these areas, but overall coverage should remain very isolated. Lastly, isolated thunderstorms could last a few more hour across central OR and adjacent south-central WA. ..Mosier.. 09/08/2024 Read more

No watches are valid as of Sat Sep 7 21:46:02 UTC 2024.

No Mesoscale Discussions are in effect as of Sat Sep 7 21:46:02 UTC 2024.

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0324 PM CDT Sat Sep 07 2024 Valid 091200Z - 151200Z A seasonably strong trough will move into the Northwest early next week. This feature will dig into the Great Basin mid/late next week before lifting northeastward by the weekend. Fire weather concerns will be greatest within parts of the Great Basin beginning next week. Additional concerns are possible in the Plains depending on trends in model guidance and fuel receptiveness. ...Great Basin... Fire weather concerns will increase across the Great Basin on Tuesday as upper-level winds begin to increase across the Sierra. The spatial extent of stronger surface winds on Tuesday is a bit uncertain given the initially weak surface pressure pattern. Potential for critical fire weather will increase on Wednesday as the trough digs farther south and east and a deeper surface trough develops in the central/eastern Basin. Very dry conditions are possible along with winds that could exceed 20 mph, especially in southern Nevada into western Utah. ...Northwest... A few hours of elevated to near-critical conditions are possible in the lee of the Cascades as winds increase ahead of the surface front on Monday. RH may be on the marginal side, particularly with northward extent, as the influence of marine air will be on the increase. However, recent active fire behavior and ignitions from recent lightning suggest some fire weather concerns will be present with the modest increase in westerly surface winds. ...Central and Northern High Plains/Plains... As the strong trough moves into the Great Basin and eventually lifts northeastward mid/late next week, southerly winds across these regions will increase as a surface low and lee trough deepens. The typically drier GFS would suggest at least elevated fire weather conditions are possible, but there is low confidence in ensemble guidance as well as the ECMWF as to where and for how long near-critical/critical conditions may occur. Furthermore, fuels are not equally dry across all areas. In general, initial return flow cases tend to verify drier than expected and with the added potential for a tropical system to impact the central Gulf Coast into the Mid South late next week, this may further stunt moisture return northward. Trends in model guidance and fuel dryness will continue to be monitored. ...Western/central Montana... As a surface low deepens in Alberta/Saskatchewan and a lee trough extends into the central High Plains, surface winds will increase in the lee of the terrain and into parts of central Montana. Downslope winds will lead to dry afternoon conditions on Monday. Upper-level winds over the area will be only modest and fuels are only moderately dry, however. Potential for critical fire weather appears too low for highlights, though at least a few hours of elevated conditions are possible. ..Wendt.. 09/07/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0238 PM CDT Sat Sep 07 2024 Valid 072000Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today, though a few strong gusts could accompany the more robust storms. ...20Z Update... The forecast remains on track, and only minor changes were made to the outlook with this update. In particular, the General Thunder line was trimmed behind the frontal rain band and associated wind shift in the Northeast, where cool post-frontal conditions have generally depleted instability. Updrafts within this band have remained too shallow/weak for an appreciable lightning risk thus far. However, an isolated strike still cannot be ruled out, especially over portions of eastern NJ and far southeastern NY/Long Island -- where filtered boundary-layer heating has occurred amid middle 60s dewpoints. Isolated/embedded strong gusts also remain possible (earlier 44 mph gust in eastern PA), though the weak/shallow updrafts (and associated downdrafts) should continue to limit the severe risk. Elsewhere, severe potential still appears too localized and/or marginal for severe probabilities. See the previous discussion below for details. ..Weinman.. 09/07/2024 .PREV DISCUSSION... /ISSUED 1131 AM CDT Sat Sep 07 2024/ ...Northeast... A cold front will move steadily east across the northeast today, accompanied by showers and thunderstorms. Extensive cloud cover in advance of the front will tend to limit heating/destabilization, however modest MLCAPE (on the order of 250-500 J/kg) may develop from the northern Delmarva Peninsula north into southeast NY this afternoon. Ascent with an upper-level trough will continue to move east in tandem with the front, and scattered thunderstorms may develop this afternoon with some potential for locally gusty winds. Weak instability and poor low-level lapse rates should limit severe potential. ...Central High Plains... Low-level moisture will be generally modest east of a surface trough that will extend north-south across eastern portions of WY/CO this afternoon. Still, lower 50s surface dew points and steep mid-level lapse rates should contribute to MLCAPE of 750-locally near 1000 J/kg. Isolated thunderstorms may form and move southeast within a northwest mid-level flow environment late this afternoon/evening, and a deep/well-mixed boundary layer suggests some potential for localized strong wind gusts. Thunderstorm potential may extend eastward into western portions of NE/KS this evening as a low-level jet strengthens. The overall coverage of any severe potential remains too low to introduce severe probabilities. ...Interior Northwest... The potential for isolated thunderstorms, already ongoing this morning over south-central OR, will continue today as modest large-scale ascent associated with a mid-level trough overspreads inland areas of the Pacific Northwest. These storms may produce limited rainfall, exacerbating fire weather concerns. ...Lower Colorado River Valley and Vicinity... Strong heating will contribute to scattered thunderstorm development this afternoon, and 12z hi-res guidance suggests that a couple of stronger storms or small clusters may have the potential for gusty outflow winds within a hot/well-mixed boundary layer. Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0215 PM CDT Sat Sep 07 2024 Valid 091200Z - 101200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe-thunderstorm potential currently appears low on Monday. ...Synopsis... A deep mid/upper-level trough is forecast to move gradually eastward across the northeast CONUS on Monday. An embedded shortwave is expected to move through the base of the trough across the lower Great Lakes region into the Mid Atlantic/Northeast. A midlevel shortwave trough is forecast to move across the northern Rockies/High Plains, with a weaker shortwave potentially moving from the central Plains into the upper Midwest. An area of low pressure initially over the Bay of Campeche may evolve into a tropical cyclone. Isolated to scattered thunderstorms will be possible across parts of the lower Great Lakes, Intermountain West, and potentially into parts of the High Plains, though low-level moisture is expected to remain rather limited. Nocturnal elevated convection may be possible from the northern Plains into the upper Midwest, though this potential remains quite uncertain. ...Lower Great Lakes vicinity... Ascent and cooling temperatures aloft in association with the digging shortwave trough will support diurnal thunderstorm potential from the lower Great Lakes into central/northern NY. Most guidance suggests that buoyancy will remain quite limited, though gusty winds and small hail could accompany any deeper convection. The 07/12Z NAM is notably stronger with both the digging shortwave and destabilization, suggesting a threat for more-organized convection. Confidence in this more aggressive scenario is too low for probabilities at this time. ...Deep South Texas... See NHC forecasts and advisories for more information regarding possible tropical cyclone development in the Bay of Campeche. Uncertainty remains high regarding the details, but guidance generally suggests that the favored northeast quadrant of any developing cyclone will remain offshore of south TX into Tuesday morning, which would limit inland severe potential through the end of the period. ..Dean.. 09/07/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0156 PM CDT Sat Sep 07 2024 Valid 081200Z - 091200Z Minor changes were made to the ongoing dry thunderstorm area in the Northwest based on recent guidance. See the previous discussion for more details. ..Wendt.. 09/07/2024 .PREV DISCUSSION... /ISSUED 0207 AM CDT Sat Sep 07 2024/ ...Synopsis... The upper trough on the Pacific Coast is forecast to move inland Sunday while the mid-level ridge over much of the West is expected to continue retreating. A belt of stronger mid-level flow associated with the trough will gradually overspread portions of the Northwest and northern Great Basin, supporting an increase in surface winds to 15-25 mph. Aided by the increased mixing, and residual warm temperatures beneath the weakening ridge, diurnal minimum RH values below 15% are likely. Widespread elevated to near-critical fire-weather conditions are possible across the northern Sierra and Great Basin, where the dry and breezy conditions will overlap with areas of dry fuels. Farther north in the lee of the Cascades, gusty downslope and gap winds may also support brief elevated fire-weather potential as stronger flow aloft develops. However, some humidity recovery will eventually occur as marine influence will increase with time, potentially limiting the coverage and duration of fire-weather concerns. ...Dry Thunderstorms... Isolated to widely scattered thunderstorms are likely to be ongoing early in the period as the cold core of the upper trough moves inland over the Northwest. As lift from the upper trough and mid-level moisture move inland, additional storms may develop into the afternoon atop warm and dry low levels. Forecast soundings suggest mid/high-level cloud cover and some potential for smoke to limit heating and diurnal storm coverage. Still, isolated storm potential, along with dry low levels and storm motions greater than 20 kt will likely support a risk for dry thunderstorms atop receptive fuels. Confidence in dry thunderstorm coverage is greatest across portions of the northern and central Cascades, into eastern ID and far southwestern MT. Scattered thunderstorms are also possible farther across the southern Great Basin and southern CA. Displaced from the stronger flow aloft, and with access to more robust monsoon moisture, slower storm speeds and a wetter storm mode are expected. Still, a few drier lightning strikes will remain possible atop mostly receptive fuel beds. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1220 PM CDT Sat Sep 07 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The organized severe-thunderstorm threat is expected to be low on Sunday. ...Synopsis... A deep trough is forecast to move eastward across eastern Canada and the northeast CONUS on Sunday, as an embedded mid/upper-level cyclone moves across parts of Quebec, New Brunswick, and northern New England. To the west, a midlevel shortwave trough will move across the interior Northwest, to the north of a mid/upper-level ridge. A surface ridge covering much of the eastern CONUS will prevent return of richer low-level moisture from near the Gulf Coast. This will limit destabilization and organized severe potential across most of the CONUS. Thunderstorms will be possible from the Carolinas/Georgia to the immediate Gulf Coast, where richer moisture will persist near and north of a surface front. A few strong storms may develop across the central/northern FL Peninsula, where the relative best overlap of instability and modest flow aloft is currently forecast. Weak convection with sporadic lightning flashes could move across parts of the Great Lakes, in conjunction with a pocket of cold temperatures aloft. Isolated to scattered high-based convection will be possible from the central High Plains into parts of the central/southern Rockies, Great Basin, and Southwest, which may produce locally strong gusts. Some strong-gust potential could also accompany isolated storm development across the interior Northwest, in association with the shortwave trough moving across the region. ..Dean.. 09/07/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1220 PM CDT Sat Sep 07 2024 Valid 081200Z - 091200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The organized severe-thunderstorm threat is expected to be low on Sunday. ...Synopsis... A deep trough is forecast to move eastward across eastern Canada and the northeast CONUS on Sunday, as an embedded mid/upper-level cyclone moves across parts of Quebec, New Brunswick, and northern New England. To the west, a midlevel shortwave trough will move across the interior Northwest, to the north of a mid/upper-level ridge. A surface ridge covering much of the eastern CONUS will prevent return of richer low-level moisture from near the Gulf Coast. This will limit destabilization and organized severe potential across most of the CONUS. Thunderstorms will be possible from the Carolinas/Georgia to the immediate Gulf Coast, where richer moisture will persist near and north of a surface front. A few strong storms may develop across the central/northern FL Peninsula, where the relative best overlap of instability and modest flow aloft is currently forecast. Weak convection with sporadic lightning flashes could move across parts of the Great Lakes, in conjunction with a pocket of cold temperatures aloft. Isolated to scattered high-based convection will be possible from the central High Plains into parts of the central/southern Rockies, Great Basin, and Southwest, which may produce locally strong gusts. Some strong-gust potential could also accompany isolated storm development across the interior Northwest, in association with the shortwave trough moving across the region. ..Dean.. 09/07/2024 Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1131 AM CDT Sat Sep 07 2024 Valid 071630Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today, though a few strong gusts could accompany the more intense storms. ...Northeast... A cold front will move steadily east across the northeast today, accompanied by showers and thunderstorms. Extensive cloud cover in advance of the front will tend to limit heating/destabilization, however modest MLCAPE (on the order of 250-500 J/kg) may develop from the northern Delmarva Peninsula north into southeast NY this afternoon. Ascent with an upper-level trough will continue to move east in tandem with the front, and scattered thunderstorms may develop this afternoon with some potential for locally gusty winds. Weak instability and poor low-level lapse rates should limit severe potential. ...Central High Plains... Low-level moisture will be generally modest east of a surface trough that will extend north-south across eastern portions of WY/CO this afternoon. Still, lower 50s surface dew points and steep mid-level lapse rates should contribute to MLCAPE of 750-locally near 1000 J/kg. Isolated thunderstorms may form and move southeast within a northwest mid-level flow environment late this afternoon/evening, and a deep/well-mixed boundary layer suggests some potential for localized strong wind gusts. Thunderstorm potential may extend eastward into western portions of NE/KS this evening as a low-level jet strengthens. The overall coverage of any severe potential remains too low to introduce severe probabilities. ...Interior Northwest... The potential for isolated thunderstorms, already ongoing this morning over south-central OR, will continue today as modest large-scale ascent associated with a mid-level trough overspreads inland areas of the Pacific Northwest. These storms may produce limited rainfall, exacerbating fire weather concerns. ...Lower Colorado River Valley and Vicinity... Strong heating will contribute to scattered thunderstorm development this afternoon, and 12z hi-res guidance suggests that a couple of stronger storms or small clusters may have the potential for gusty outflow winds within a hot/well-mixed boundary layer. ..Bunting/Elliott.. 09/07/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1125 AM CDT Sat Sep 07 2024 Valid 071700Z - 081200Z Based on current observations and recent guidance, modest modifications were made to the dry thunderstorm area in the Northwest. The forecast is otherwise unchanged. See the previous discussion below for more details. ..Wendt.. 09/07/2024 .PREV DISCUSSION... /ISSUED 0202 AM CDT Sat Sep 07 2024/ ...Synopsis... An upper ridge over the western CONUS is forecast to slowly weaken under the influence of an approaching Pacific trough today and tonight. As ascent from the trough overspreads mid-level moisture, thunderstorms are likely across portions of the Cascades in OR and southern WA. Model and observed soundings show weak buoyancy atop hot and well-mixed boundary-layer profiles, supporting low precipitation efficiency, especially with storm motions greater than 20 kt. Hi-res model guidance suggests dry thunderstorm potential is highest across portions of the central Cascades, though more isolated and drier storms will also be possible across the northern Sierra and portions of southern CA. ...Sierra and northwest Great Basin... To the south of the main trough, moderate mid-level flow should gradually expand over parts of northern CA and the northern Great Basin. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values of 15-20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0723 AM CDT Sat Sep 07 2024 Valid 071300Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today, though a few strong gusts could accompany the most robust convection. ...Synopsis/Discussion... The mid/upper-level pattern will feature strong, progressive troughing over the Great Lakes and vicinity, and ridging from the Four Corners north-northwestward to the Canadian Rockies. The major synoptic trough over the Great Lakes is anchored by a cyclone initially centered over Lake Huron. The low should move erratically eastward to northeastward across ON to southwestern QC by the end of the period. As this occurs, strengthening cyclonic flow and height falls will overspread the Northeast, while cyclonic flow remains behind the low across the Great Lakes, Ohio Valley and central Appalachians. An associated surface cold front -- analyzed at 11Z from central NY across northwestern VA, easternmost TN, northern MS, north TX, and central NM -- should move eastward across NY to central/eastern New England by 00Z, extending southward offshore from most of the Mid- Atlantic Coast, and merging with a northeastward-moving surface cyclone now located offshore from SC. A separate surface cyclone (with mid/upper-level extension) now south of Nova Scotia will move northward, with peripheral isallobaric effects limiting convergence along the cold front for much of today. Still, a band of showers and embedded thunderstorms may organize enough to produce strong gusts for a couple hours this afternoon from the Hudson Valley region into NJ, the NYC area and western Long Island. At this time, weak lapse rates and low-level shear are still forecast, and organized severe-gust potential appears too low and conditional for an outlook. In the West, a weak binary cyclone (with two apparent centers in moisture-channel imagery) covers the coastal areas of OR and northwestern CA, as well as adjoining Pacific waters. This feature is devolving into an open-wave trough, and will continue to weaken through the period as it slowly moves inland. Associated large- scale ascent, overlapping diurnal/diabatic destabilization of higher terrain, may contribute to thunder potential (including dry thunder for fire-weather purposes) over portions of the interior Northwest. Northwest flow aloft, east of the ridge, will overlie a well- developed surface lee trough over eastern parts of CO/WY. Strong veering with height is expected, but with weak low/middle-level flow. Though ideally rich moisture will be well-removed from this region, over the Gulf, enough residual/post-frontal moisture should remain to support isolated to widely scattered, high-based thunderstorms this afternoon over eastern WY/CO, and perhaps this evening over southwestern NE near a strengthening LLJ. Forecast soundings show a deep, well-mixed subcloud layer that may support strong gusts from low-precip cells. However, with weak moisture and strong mixing leading to limited buoyancy (MLCAPE less than 800 J/kg), severe potential appears isolated at best, with unconditional areal probabilities remaining below 5% this outlook cycle. ..Edwards/Kerr.. 09/07/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0723 AM CDT Sat Sep 07 2024 Valid 071300Z - 081200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not forecast today, though a few strong gusts could accompany the most robust convection. ...Synopsis/Discussion... The mid/upper-level pattern will feature strong, progressive troughing over the Great Lakes and vicinity, and ridging from the Four Corners north-northwestward to the Canadian Rockies. The major synoptic trough over the Great Lakes is anchored by a cyclone initially centered over Lake Huron. The low should move erratically eastward to northeastward across ON to southwestern QC by the end of the period. As this occurs, strengthening cyclonic flow and height falls will overspread the Northeast, while cyclonic flow remains behind the low across the Great Lakes, Ohio Valley and central Appalachians. An associated surface cold front -- analyzed at 11Z from central NY across northwestern VA, easternmost TN, northern MS, north TX, and central NM -- should move eastward across NY to central/eastern New England by 00Z, extending southward offshore from most of the Mid- Atlantic Coast, and merging with a northeastward-moving surface cyclone now located offshore from SC. A separate surface cyclone (with mid/upper-level extension) now south of Nova Scotia will move northward, with peripheral isallobaric effects limiting convergence along the cold front for much of today. Still, a band of showers and embedded thunderstorms may organize enough to produce strong gusts for a couple hours this afternoon from the Hudson Valley region into NJ, the NYC area and western Long Island. At this time, weak lapse rates and low-level shear are still forecast, and organized severe-gust potential appears too low and conditional for an outlook. In the West, a weak binary cyclone (with two apparent centers in moisture-channel imagery) covers the coastal areas of OR and northwestern CA, as well as adjoining Pacific waters. This feature is devolving into an open-wave trough, and will continue to weaken through the period as it slowly moves inland. Associated large- scale ascent, overlapping diurnal/diabatic destabilization of higher terrain, may contribute to thunder potential (including dry thunder for fire-weather purposes) over portions of the interior Northwest. Northwest flow aloft, east of the ridge, will overlie a well- developed surface lee trough over eastern parts of CO/WY. Strong veering with height is expected, but with weak low/middle-level flow. Though ideally rich moisture will be well-removed from this region, over the Gulf, enough residual/post-frontal moisture should remain to support isolated to widely scattered, high-based thunderstorms this afternoon over eastern WY/CO, and perhaps this evening over southwestern NE near a strengthening LLJ. Forecast soundings show a deep, well-mixed subcloud layer that may support strong gusts from low-precip cells. However, with weak moisture and strong mixing leading to limited buoyancy (MLCAPE less than 800 J/kg), severe potential appears isolated at best, with unconditional areal probabilities remaining below 5% this outlook cycle. ..Edwards/Kerr.. 09/07/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Sat Sep 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... ...Tuesday/Day 4 to Thursday/Day 6... A shortwave ridge is forecast to move eastward across the Great Lakes region on Tuesday and into the Northeast on Wednesday. Another shortwave ridge is forecast to move through the north-central U.S. on Wednesday as an upper-level trough amplifies across the western U.S. Due to the presence of instability in the northern Plains, thunderstorm development will be possible each afternoon. However, large-scale ascent is expected to be limited and deep-layer shear relatively weak, suggesting that storms should remain isolated and unorganized. Additional storms will be possible near the Gulf Coast each day. ...Friday/Day 7 and Saturday/Day 8... The western U.S. upper-level trough is forecast to move through the Rockies and into the north-central states from Friday into Saturday. As the trough moves out, large-scale ascent is forecast to overspread a moist and unstable airmass in the northern and central Plains. Although some severe threat will be possible ahead of the trough, deep-layer shear is forecast to be relatively weak. This suggests that any severe threat that develops during the afternoon and evening should remain isolated. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0353 AM CDT Sat Sep 07 2024 Valid 101200Z - 151200Z ...DISCUSSION... ...Tuesday/Day 4 to Thursday/Day 6... A shortwave ridge is forecast to move eastward across the Great Lakes region on Tuesday and into the Northeast on Wednesday. Another shortwave ridge is forecast to move through the north-central U.S. on Wednesday as an upper-level trough amplifies across the western U.S. Due to the presence of instability in the northern Plains, thunderstorm development will be possible each afternoon. However, large-scale ascent is expected to be limited and deep-layer shear relatively weak, suggesting that storms should remain isolated and unorganized. Additional storms will be possible near the Gulf Coast each day. ...Friday/Day 7 and Saturday/Day 8... The western U.S. upper-level trough is forecast to move through the Rockies and into the north-central states from Friday into Saturday. As the trough moves out, large-scale ascent is forecast to overspread a moist and unstable airmass in the northern and central Plains. Although some severe threat will be possible ahead of the trough, deep-layer shear is forecast to be relatively weak. This suggests that any severe threat that develops during the afternoon and evening should remain isolated. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Sat Sep 07 2024 Valid 091200Z - 101200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Thunderstorms will be possible on Monday across parts of the lower Great Lakes, Southeast and from the Four Corners region northeastward into the north-central states. No severe thunderstorms are expected Monday or Monday night. ...DISCUSSION... An upper-level trough is forecast to move eastward across the Northeast on Monday. Isolated thunderstorms will be possible near the through in the lower Great Lakes region. Additional storms are expected to develop near the Gulf Coast along and near a front. Other storms will likely develop from the Four Corners region northeastward into the north-central states. No severe storms are expected Monday and Monday night across the U.S. ..Broyles.. 09/07/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0207 AM CDT Sat Sep 07 2024 Valid 081200Z - 091200Z ...Synopsis... The upper trough on the Pacific Coast is forecast to move inland Sunday while the mid-level ridge over much of the West is expected to continue retreating. A belt of stronger mid-level flow associated with the trough will gradually overspread portions of the Northwest and northern Great Basin, supporting an increase in surface winds to 15-25 mph. Aided by the increased mixing, and residual warm temperatures beneath the weakening ridge, diurnal minimum RH values below 15% are likely. Widespread elevated to near-critical fire-weather conditions are possible across the northern Sierra and Great Basin, where the dry and breezy conditions will overlap with areas of dry fuels. Farther north in the lee of the Cascades, gusty downslope and gap winds may also support brief elevated fire-weather potential as stronger flow aloft develops. However, some humidity recovery will eventually occur as marine influence will increase with time, potentially limiting the coverage and duration of fire-weather concerns. ...Dry Thunderstorms... Isolated to widely scattered thunderstorms are likely to be ongoing early in the period as the cold core of the upper trough moves inland over the Northwest. As lift from the upper trough and mid-level moisture move inland, additional storms may develop into the afternoon atop warm and dry low levels. Forecast soundings suggest mid/high-level cloud cover and some potential for smoke to limit heating and diurnal storm coverage. Still, isolated storm potential, along with dry low levels and storm motions greater than 20 kt will likely support a risk for dry thunderstorms atop receptive fuels. Confidence in dry thunderstorm coverage is greatest across portions of the northern and central Cascades, into eastern ID and far southwestern MT. Scattered thunderstorms are also possible farther across the southern Great Basin and southern CA. Displaced from the stronger flow aloft, and with access to more robust monsoon moisture, slower storm speeds and a wetter storm mode are expected. Still, a few drier lightning strikes will remain possible atop mostly receptive fuel beds. ..Lyons.. 09/07/2024 ...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 0202 AM CDT Sat Sep 07 2024 Valid 071200Z - 081200Z ...Synopsis... An upper ridge over the western CONUS is forecast to slowly weaken under the influence of an approaching Pacific trough today and tonight. As ascent from the trough overspreads mid-level moisture, thunderstorms are likely across portions of the Cascades in OR and southern WA. Model and observed soundings show weak buoyancy atop hot and well-mixed boundary-layer profiles, supporting low precipitation efficiency, especially with storm motions greater than 20 kt. Hi-res model guidance suggests dry thunderstorm potential is highest across portions of the central Cascades, though more isolated and drier storms will also be possible across the northern Sierra and portions of southern CA. ...Sierra and northwest Great Basin... To the south of the main trough, moderate mid-level flow should gradually expand over parts of northern CA and the northern Great Basin. Gusty winds of 15-20 mph in the lee of the Sierra are likely to overlap with afternoon RH values of 15-20%. With receptive fuels and at least a few hours of dry and breezy conditions possible, elevated fire-weather conditions are likely. ..Lyons.. 09/07/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more