WW 0627 Status Updates
STATUS FOR WATCH 0627 HAS NOT BEEN ISSUED YET Read more

No Mesoscale Discussions are in effect as of Fri Aug 16 13:47:01 UTC 2024.

No watches are valid as of Fri Aug 16 13:47:01 UTC 2024.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Fri Aug 16 2024 Valid 161300Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR MUCH OF KANSAS INTO NORTHERN OKLAHOMA AND INTO NORTHWEST ARKANSAS AND FAR SOUTHWEST MISSOURI... ...SUMMARY... Scattered severe thunderstorms are possible for much of Kansas into northern Oklahoma and into northwest Arkansas. Large to very large hail and severe gusts are the expected hazards with the stronger thunderstorms. ...Central/Southern Plains Region... A surface front will become draped from the Ozarks westward into KS and arcing into the north-central High Plains by mid afternoon. With this region largely in between a mid-level anticyclone over NM and an upper low over the Upper Midwest, a subtle impulse in water-vapor imagery over the central High Plains is forecast to gradually move east across KS today. Models show an instability axis paralleling the frontal zone where the combination of deep-layer shear/buoyancy will be greatest. It is within the Slight Risk where the potential for organized storms, including supercells and eventually severe clusters/line segments appear to be most probable. However, given the relatively modest forcing, it is not entirely clear how storm clusters evolve except for the peak storm intensity/coverage to generally focus late this afternoon into the evening. This activity will likely continue to move east-southeast into richer moisture in the northeast OK vicinity and yield a risk for severe gusts potentially into tonight. Farther southwest into western OK and adjacent parts of TX, a hot and deeply mixed boundary layer will feature very steep 0-3 km lapse rates by late afternoon. Isolated to scattered storms are indicated in model guidance. Severe gusts associated with evaporatively cooled downdrafts appear to be the primary hazard before this activity weakens by mid evening. ...KY/TN Valley/Mid South... Scattered showers/thunderstorm ongoing this morning across parts of TN/KY will continue east through the morning. Heating ahead of this activity will act to destabilize a moist airmass with additional development forecast on trailing outflow. Isolated to widely scattered damaging gusts are possible with the more intense storms once the boundary layer sufficiently destabilizes. Some recent model guidance indicates a focused mesoscale corridor for wind potential may evolve across the TN Valley but uncertainty is relatively high for this scenario. ...Southern Great Lakes vicinity... Water-vapor imagery this morning shows a leading mid-level vorticity maximum moving east across northern IN/southern Lower MI. Weak instability immediately downstream of this impulse (250 J/kg MUCAPE per the Detroit 12 UTC raob) and an associated cloud shield will likely limited storm intensity until stronger heating can occur. Upstream of the aforementioned disturbance, another mid-level shortwave is forecast to rotate east-southeastward from MN towards Lake Michigan through the early evening. Heating ahead of this impulse will yield at least weak to moderate buoyancy by early afternoon. Isolated strong/severe thunderstorms are expected to develop immediately ahead of the upper low. Hail/wind are possible with storms that evolve along this corridor of stronger instability. ..Smith/Mosier.. 08/16/2024 Read more

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Fri Aug 16 2024 Valid 161300Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR MUCH OF KANSAS INTO NORTHERN OKLAHOMA AND INTO NORTHWEST ARKANSAS AND FAR SOUTHWEST MISSOURI... ...SUMMARY... Scattered severe thunderstorms are possible for much of Kansas into northern Oklahoma and into northwest Arkansas. Large to very large hail and severe gusts are the expected hazards with the stronger thunderstorms. ...Central/Southern Plains Region... A surface front will become draped from the Ozarks westward into KS and arcing into the north-central High Plains by mid afternoon. With this region largely in between a mid-level anticyclone over NM and an upper low over the Upper Midwest, a subtle impulse in water-vapor imagery over the central High Plains is forecast to gradually move east across KS today. Models show an instability axis paralleling the frontal zone where the combination of deep-layer shear/buoyancy will be greatest. It is within the Slight Risk where the potential for organized storms, including supercells and eventually severe clusters/line segments appear to be most probable. However, given the relatively modest forcing, it is not entirely clear how storm clusters evolve except for the peak storm intensity/coverage to generally focus late this afternoon into the evening. This activity will likely continue to move east-southeast into richer moisture in the northeast OK vicinity and yield a risk for severe gusts potentially into tonight. Farther southwest into western OK and adjacent parts of TX, a hot and deeply mixed boundary layer will feature very steep 0-3 km lapse rates by late afternoon. Isolated to scattered storms are indicated in model guidance. Severe gusts associated with evaporatively cooled downdrafts appear to be the primary hazard before this activity weakens by mid evening. ...KY/TN Valley/Mid South... Scattered showers/thunderstorm ongoing this morning across parts of TN/KY will continue east through the morning. Heating ahead of this activity will act to destabilize a moist airmass with additional development forecast on trailing outflow. Isolated to widely scattered damaging gusts are possible with the more intense storms once the boundary layer sufficiently destabilizes. Some recent model guidance indicates a focused mesoscale corridor for wind potential may evolve across the TN Valley but uncertainty is relatively high for this scenario. ...Southern Great Lakes vicinity... Water-vapor imagery this morning shows a leading mid-level vorticity maximum moving east across northern IN/southern Lower MI. Weak instability immediately downstream of this impulse (250 J/kg MUCAPE per the Detroit 12 UTC raob) and an associated cloud shield will likely limited storm intensity until stronger heating can occur. Upstream of the aforementioned disturbance, another mid-level shortwave is forecast to rotate east-southeastward from MN towards Lake Michigan through the early evening. Heating ahead of this impulse will yield at least weak to moderate buoyancy by early afternoon. Isolated strong/severe thunderstorms are expected to develop immediately ahead of the upper low. Hail/wind are possible with storms that evolve along this corridor of stronger instability. ..Smith/Mosier.. 08/16/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0344 AM CDT Fri Aug 16 2024 Valid 191200Z - 241200Z ...DISCUSSION... ...Monday/Day 4 to Wednesday/Day 6... An upper-level ridge is forecast to remain over the High Plains from early to mid week, as an upper-level trough moves slowly eastward across the eastern U.S. Surface high pressure, associated with the trough is forecast to move from the middle to upper Mississippi Valley on Monday to the middle and upper Atlantic Seaboard by Wednesday. Due to this high, the airmass across much of the eastern third of the U.S. will likely become drier and less unstable from Monday to Wednesday, making conditions less favorable for severe storms. Further to the west, a south-to-north corridor of moderate instability is forecast to develop each day, remaining in a similar position across the central and northern Plains. Thunderstorms will be possible each afternoon and evening to the east of the ridge near the axis of instability. It appears that deep-layer shear will be relatively weak near instability axis, which will favor less storm organization. Still, a marginal severe threat will be possible due to the strong instability. ...Thursday/Day 7 and Friday/Day 8... The upper-level ridge in the north-central U.S. is forecast to move eastward from the northern Plains on Thursday into the western Great Lakes region by Friday. An axis of moderate to strong instability is forecast to remain over the central and northern Plains. Thunderstorms that form each afternoon close the instability axis will have a chance be severe. Although there is a lot of uncertainty this far out in the forecast cycle, the subsidence and weaker deep-layer shear associated with the upper-level ridge, should negatively impact severe potential. However, instability could be strong enough for a marginal severe threat, mainly during the afternoon and evening on Thursday and Friday. Read more

MD 1918 CONCERNING SEVERE THUNDERSTORM WATCH 626... FOR CENTRAL IL...FAR NORTHWEST IN...EXTREME NORTHEAST MO
Mesoscale Discussion 1918 NWS Storm Prediction Center Norman OK 0119 AM CDT Fri Aug 16 2024 Areas affected...Central IL...Far Northwest IN...Extreme Northeast MO Concerning...Severe Thunderstorm Watch 626... Valid 160619Z - 160815Z The severe weather threat for Severe Thunderstorm Watch 626 continues. SUMMARY...The threat for damaging wind gusts continues from far northeast Missouri across central Illinois into far northwest Indiana. DISCUSSION...Thunderstorm coverage within the convective cluster ongoing across central IL has expanded southwestward along the outflow into more of west-central IL and far northeast MO over the past hour. The airmass downstream of this new development is moist and buoyant, as evidenced by the more discrete storms currently developing ahead of the line over central IL. As such, the general expectation is for this newer development to persist, and perhaps even strengthen, as it continues eastward over the next few hours. Primary risk would be damaging gusts with any bowing line segments. Farther north, the portion of the line moving across northeast IL continues to move eastward at about 40 kt. Buoyancy decreases notably from northeast IL into northern IN, and the general expectation is for this portion of the line to gradually weaken. Even so, localized damaging gusts will remain possible, particularly over the next hour or so. ..Mosier.. 08/16/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...IND...LOT...ILX...LSX...DVN... LAT...LON 40419131 41488875 41498746 40998712 40298713 39378813 39159039 39589214 40419131 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0213 AM CDT Fri Aug 16 2024 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE MID-ATLANTIC AND CAROLINAS WEST-SOUTHWESTWARD INTO THE SOUTHEAST...AND ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... A marginal severe threat is expected on Sunday from the Mid-Atlantic and Carolinas west-southwestward into much of the Southeast. A marginal severe threat will also be possible across parts of the central and northern High Plains. ...Mid-Atlantic/Carolinas/Southeast... An upper-level trough is forecast to move eastward into the southern and central Appalachians on Sunday. At the surface, an associated cold front is forecast to advance eastward into the Atlantic Coastal Plains, and southeastward into the southeastern states. Ahead of the front, surface dewpoints are expected to be in the 70s F, which will contribute to moderate instability across a broad area by afternoon. Isolated to scattered thunderstorms are expected to form near the boundary. Some convection may also develop southeastward into the moist airmass. Although the upper-level trough will likely provide some support for convective development, the area ahead of the trough from the Mid-Atlantic southeastward into the eastern Gulf Coast states is forecast to have marginal deep-layer shear for severe storms. A few isolated severe gusts will be possible near and after peak heating, mainly as low-level lapse rates become steep in the late afternoon. Further west into the lower Mississippi Valley, moderate instability is expected to develop by afternoon. Mid-level flow behind the trough will be northwesterly. This will result in stronger deep-layer shear, which should be sufficient for an isolated severe threat. The main uncertainty on Sunday in the lower Mississippi Valley is how instability will be distributed by afternoon. Some model solutions suggest that a cluster of storms will develop early in the day, which could negatively impact instability across parts of the region. Areas that can avoid this negative impact could have potential for severe wind gusts and hail during the afternoon. ...Central and Northern High Plains. An upper-level ridge is forecast to remain over the High Plains on Sunday. Beneath the ridge, a somewhat moist airmass should be in place with surface dewpoints mostly in the 50s and 60s F. As surface temperature warm on Sunday, isolated thunderstorm development will be possible across much of the central High Plains. Forecast soundings Sunday afternoon from eastern Colorado northward into western South Dakota have steep low-level lapse rates and moderate deep-layer shear. This suggest an isolated severe threat will be possible. However, subsidence associated with the ridge will negatively impact convective development, and any severe threat should remain marginal. ..Broyles.. 08/16/2024 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0213 AM CDT Fri Aug 16 2024 Valid 181200Z - 191200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE MID-ATLANTIC AND CAROLINAS WEST-SOUTHWESTWARD INTO THE SOUTHEAST...AND ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... A marginal severe threat is expected on Sunday from the Mid-Atlantic and Carolinas west-southwestward into much of the Southeast. A marginal severe threat will also be possible across parts of the central and northern High Plains. ...Mid-Atlantic/Carolinas/Southeast... An upper-level trough is forecast to move eastward into the southern and central Appalachians on Sunday. At the surface, an associated cold front is forecast to advance eastward into the Atlantic Coastal Plains, and southeastward into the southeastern states. Ahead of the front, surface dewpoints are expected to be in the 70s F, which will contribute to moderate instability across a broad area by afternoon. Isolated to scattered thunderstorms are expected to form near the boundary. Some convection may also develop southeastward into the moist airmass. Although the upper-level trough will likely provide some support for convective development, the area ahead of the trough from the Mid-Atlantic southeastward into the eastern Gulf Coast states is forecast to have marginal deep-layer shear for severe storms. A few isolated severe gusts will be possible near and after peak heating, mainly as low-level lapse rates become steep in the late afternoon. Further west into the lower Mississippi Valley, moderate instability is expected to develop by afternoon. Mid-level flow behind the trough will be northwesterly. This will result in stronger deep-layer shear, which should be sufficient for an isolated severe threat. The main uncertainty on Sunday in the lower Mississippi Valley is how instability will be distributed by afternoon. Some model solutions suggest that a cluster of storms will develop early in the day, which could negatively impact instability across parts of the region. Areas that can avoid this negative impact could have potential for severe wind gusts and hail during the afternoon. ...Central and Northern High Plains. An upper-level ridge is forecast to remain over the High Plains on Sunday. Beneath the ridge, a somewhat moist airmass should be in place with surface dewpoints mostly in the 50s and 60s F. As surface temperature warm on Sunday, isolated thunderstorm development will be possible across much of the central High Plains. Forecast soundings Sunday afternoon from eastern Colorado northward into western South Dakota have steep low-level lapse rates and moderate deep-layer shear. This suggest an isolated severe threat will be possible. However, subsidence associated with the ridge will negatively impact convective development, and any severe threat should remain marginal. ..Broyles.. 08/16/2024 Read more

WW 0626 Status Updates
STATUS REPORT ON WW 626 SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 NW SPI TO 40 NE BMI. FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1918 ..MOSIER..08/16/24 ATTN...WFO...DVN...ILX...LOT... STATUS REPORT FOR WS 626 SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS ILC039-107-113-125-160840- IL . ILLINOIS COUNTIES INCLUDED ARE DE WITT LOGAN MCLEAN MASON THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES. Read more

WW 626 SEVERE TSTM IL 160210Z - 160800Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 626 NWS Storm Prediction Center Norman OK 910 PM CDT Thu Aug 15 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of North-central and northwestern Illinois * Effective this Thursday night and Friday morning from 910 PM until 300 AM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph possible Scattered large hail events to 1.5 inches in diameter possible SUMMARY...Clusters of thunderstorms may organize to severe levels as they move eastward over the Mississippi River from IA, and into a favorably moist and unstable air mass. Damaging gusts are the main concern, with isolated large hail also possible. The severe thunderstorm watch area is approximately along and 70 statute miles east and west of a line from 35 miles south of Peoria IL to 55 miles north of Peoria IL. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU6). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Severe Thunderstorm Watch means conditions are favorable for severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. Severe thunderstorms can and occasionally do produce tornadoes. && OTHER WATCH INFORMATION...CONTINUE...WW 623...WW 624...WW 625... AVIATION...A few severe thunderstorms with hail surface and aloft to 1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 27025. ...Edwards Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0132 AM CDT Fri Aug 16 2024 Valid 171200Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHEASTERN OREGON AND NORTHERN NEVADA... ...CRITICAL FIRE WEATHER AREA FOR SOUTHWESTERN NEVADA AND PORTIONS OF CALIFORNIA... ...Synopsis... On Saturday, a mid-level shortwave trough is forecast to approach the northern California and Oregon coasts, with a fairly strong mid-level jet of 60-70 kts forecast to move northward from the San Francisco Bay area into southeastern Oregon. This trough and associated jet streak will bring critical fire-weather conditions across portions of southeastern Oregon and northern Nevada, as well as southwestern Nevada and the White/Inyo mountains of California. ...Dry/Windy... Two primary areas for critical fire-weather conditions are anticipated -- one over portions of northern Nevada and southern Oregon, and the other over southwestern Nevada and the White/Inyo mountain ranges of California. The strongest winds will likely be beneath the strongest flow of the mid-level jet streak and near the surface low in Oregon, forecast to be as high as 20-25 MPH with gusts up to 35 MPH possible. These winds will overlap with relative humidity values of 10-15% and ERC fuels near the 90th annual percentile. Some recent wetting rainfall has occurred over south-central Oregon, though modestly dry/windy conditions on Friday should result in at least some drying of fuels before Saturday. In southwestern Nevada and portions of the White/Inyo mountains in California, sustained winds of 20-25 MPH and relative humidity values of 10-15% will overspread fuels at or exceeding the 95th annual percentile, resulting in critical fire-weather conditions. Modifications to these areas may be needed with updated fuels and meteorological guidance. ..Halbert/Squitieri.. 08/16/2024 ...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 0132 AM CDT Fri Aug 16 2024 Valid 171200Z - 181200Z ...CRITICAL FIRE WEATHER AREA FOR SOUTHEASTERN OREGON AND NORTHERN NEVADA... ...CRITICAL FIRE WEATHER AREA FOR SOUTHWESTERN NEVADA AND PORTIONS OF CALIFORNIA... ...Synopsis... On Saturday, a mid-level shortwave trough is forecast to approach the northern California and Oregon coasts, with a fairly strong mid-level jet of 60-70 kts forecast to move northward from the San Francisco Bay area into southeastern Oregon. This trough and associated jet streak will bring critical fire-weather conditions across portions of southeastern Oregon and northern Nevada, as well as southwestern Nevada and the White/Inyo mountains of California. ...Dry/Windy... Two primary areas for critical fire-weather conditions are anticipated -- one over portions of northern Nevada and southern Oregon, and the other over southwestern Nevada and the White/Inyo mountain ranges of California. The strongest winds will likely be beneath the strongest flow of the mid-level jet streak and near the surface low in Oregon, forecast to be as high as 20-25 MPH with gusts up to 35 MPH possible. These winds will overlap with relative humidity values of 10-15% and ERC fuels near the 90th annual percentile. Some recent wetting rainfall has occurred over south-central Oregon, though modestly dry/windy conditions on Friday should result in at least some drying of fuels before Saturday. In southwestern Nevada and portions of the White/Inyo mountains in California, sustained winds of 20-25 MPH and relative humidity values of 10-15% will overspread fuels at or exceeding the 95th annual percentile, resulting in critical fire-weather conditions. Modifications to these areas may be needed with updated fuels and meteorological guidance. ..Halbert/Squitieri.. 08/16/2024 ...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 0103 AM CDT Fri Aug 16 2024 Valid 161200Z - 171200Z ...Synopsis... Broad, west-southwesterly mid-level flow will overspread portions of California and northern Nevada today, with a modest jet streak (with 40-45 kt winds) progressing east across the northern Great Basin. As this weak jet moves east, elevated fire-weather conditions are expected across portions of California and Nevada. ...Dry/Windy... South of this mid-level jet and north of a mid-level ridge centered over portions of Arizona and New Mexico, deep boundary layer mixing will result in dry and windy conditions across portions of California, Nevada, and Utah. Surface winds of 20-25 MPH and relative humidity values of 5-10% are expected, though will only overlap narrowly with a belt of receptive fuels across portions of Nevada and California. With winds and relative humidity being supportive of wildfire spread, but only modest fuel receptiveness, highlights have been limited to elevated conditions at this time. Recent wetting rainfall in eastern Nevada and western Utah will limit wildfire potential in these areas, though additional drying of fuels is expected given the dry/windy conditions. ...Dry Thunderstorms... The potential for some dry thunderstorms exists across portions of northern Wyoming and southeastern Montana. However, recent wetting rainfall and fuels guidance suggests there is minimal risk for wildfire spread and lightning-based ignitions at this time. ..Halbert/Squitieri.. 08/16/2024 ...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 0103 AM CDT Fri Aug 16 2024 Valid 161200Z - 171200Z ...Synopsis... Broad, west-southwesterly mid-level flow will overspread portions of California and northern Nevada today, with a modest jet streak (with 40-45 kt winds) progressing east across the northern Great Basin. As this weak jet moves east, elevated fire-weather conditions are expected across portions of California and Nevada. ...Dry/Windy... South of this mid-level jet and north of a mid-level ridge centered over portions of Arizona and New Mexico, deep boundary layer mixing will result in dry and windy conditions across portions of California, Nevada, and Utah. Surface winds of 20-25 MPH and relative humidity values of 5-10% are expected, though will only overlap narrowly with a belt of receptive fuels across portions of Nevada and California. With winds and relative humidity being supportive of wildfire spread, but only modest fuel receptiveness, highlights have been limited to elevated conditions at this time. Recent wetting rainfall in eastern Nevada and western Utah will limit wildfire potential in these areas, though additional drying of fuels is expected given the dry/windy conditions. ...Dry Thunderstorms... The potential for some dry thunderstorms exists across portions of northern Wyoming and southeastern Montana. However, recent wetting rainfall and fuels guidance suggests there is minimal risk for wildfire spread and lightning-based ignitions at this time. ..Halbert/Squitieri.. 08/16/2024 ...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 0100 AM CDT Fri Aug 16 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE OZARKS NORTHEASTWARD TO THE UPPER OHIO VALLEY...AND IN PARTS OF THE PACIFIC NORTHWEST... ...SUMMARY... Marginally severe thunderstorms will be possible on Saturday afternoon and evening from the Ozarks and lower Mississippi northeastward into the upper Ohio Valley. Isolated severe storms may also occur across parts of the Pacific Northwest. ...Ozarks/Lower Mississippi Valley... Northwest mid-level flow will remain today from the mid Missouri Valley into the mid Mississippi Valley. At the surface, a moist airmass will be located from the Ozarks into the mid Mississippi Valley. Moderate instability is expected to develop throughout this moist airass by afternoon. As temperatures warm during the day, scattered thunderstorms will be possible across a broad area from the Ohio and Tennessee Valley eastward into the Appalachians. Model forecasts in the Ozarks by afternoon increase MLCAPE into the 1000 to 2000 J/kg range, and show moderate deep-layer shear in most areas. This should be enough for a marginal severe threat during the late afternoon and early evening. Although supercells will be possible, line segments may also develop. Hail and strong gusty winds will be possible with supercells. Severe wind gusts will be the primary threat with line segments. ...Ohio and Tennessee Valleys/Southern and Central Appalachians... An upper-level low will move across the Great Lakes on Saturday, as southwest mid-level flow remains in place from the Ohio and Tennessee Valleys into the Appalachians. Moderate instability is expected to develop by early this afternoon along an axis of maximized low-level moisture from middle Tennessee northeastward into southern and eastern Ohio. Isolated to scattered thunderstorms will likely develop during the afternoon throughout this moist airmass. RAP forecast soundings in the early afternoon from middle Tennessee to southern Ohio show moderate deep-layer shear across much of the region. This could support an isolated severe threat with cells that develop in areas with the strongest instability. However, low to mid-level lapse rates and large-scale ascent are forecast to be relatively weak suggesting that any severe threat will remain marginal. ...Pacific Northwest... An upper-level low will remain in the far eastern Pacific. Ahead of this feature, mid-level flow will be southwesterly across much of the northwestern U.S. At the surface, a moist airmass is forecast to be in place across western Oregon and western Washington. As surface temperatures warm, a narrow corridor of moderate instability is expected to develop near the moist axis, with storms forming during the afternoon. In addition to the instability, model forecasts suggest that 0-6 km shear will be in the 45 to 55 knot range. This, combined with steep mid-level lapse rates may support an isolated severe threat. Cells that form within this area of moderate instability, could obtain a marginal severe threat with hail and severe gusts possible. ..Broyles.. 08/16/2024 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Fri Aug 16 2024 Valid 171200Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE OZARKS NORTHEASTWARD TO THE UPPER OHIO VALLEY...AND IN PARTS OF THE PACIFIC NORTHWEST... ...SUMMARY... Marginally severe thunderstorms will be possible on Saturday afternoon and evening from the Ozarks and lower Mississippi northeastward into the upper Ohio Valley. Isolated severe storms may also occur across parts of the Pacific Northwest. ...Ozarks/Lower Mississippi Valley... Northwest mid-level flow will remain today from the mid Missouri Valley into the mid Mississippi Valley. At the surface, a moist airmass will be located from the Ozarks into the mid Mississippi Valley. Moderate instability is expected to develop throughout this moist airass by afternoon. As temperatures warm during the day, scattered thunderstorms will be possible across a broad area from the Ohio and Tennessee Valley eastward into the Appalachians. Model forecasts in the Ozarks by afternoon increase MLCAPE into the 1000 to 2000 J/kg range, and show moderate deep-layer shear in most areas. This should be enough for a marginal severe threat during the late afternoon and early evening. Although supercells will be possible, line segments may also develop. Hail and strong gusty winds will be possible with supercells. Severe wind gusts will be the primary threat with line segments. ...Ohio and Tennessee Valleys/Southern and Central Appalachians... An upper-level low will move across the Great Lakes on Saturday, as southwest mid-level flow remains in place from the Ohio and Tennessee Valleys into the Appalachians. Moderate instability is expected to develop by early this afternoon along an axis of maximized low-level moisture from middle Tennessee northeastward into southern and eastern Ohio. Isolated to scattered thunderstorms will likely develop during the afternoon throughout this moist airmass. RAP forecast soundings in the early afternoon from middle Tennessee to southern Ohio show moderate deep-layer shear across much of the region. This could support an isolated severe threat with cells that develop in areas with the strongest instability. However, low to mid-level lapse rates and large-scale ascent are forecast to be relatively weak suggesting that any severe threat will remain marginal. ...Pacific Northwest... An upper-level low will remain in the far eastern Pacific. Ahead of this feature, mid-level flow will be southwesterly across much of the northwestern U.S. At the surface, a moist airmass is forecast to be in place across western Oregon and western Washington. As surface temperatures warm, a narrow corridor of moderate instability is expected to develop near the moist axis, with storms forming during the afternoon. In addition to the instability, model forecasts suggest that 0-6 km shear will be in the 45 to 55 knot range. This, combined with steep mid-level lapse rates may support an isolated severe threat. Cells that form within this area of moderate instability, could obtain a marginal severe threat with hail and severe gusts possible. ..Broyles.. 08/16/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1246 AM CDT Fri Aug 16 2024 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS INTO THE OZARKS OF NORTHWEST ARKANSAS... ...SUMMARY... Isolated-scattered severe thunderstorms are expected across portions of the central and southern Plains, extending into northwest Arkansas. Less concentrated severe is possible across the Midwest into the Tennessee Valley. ...Central/Southern Plains Region... MS Valley trough is forecast to shift into the upper Great Lakes/Midwest region by late afternoon while a dominant upper anticyclone will hold across the southern Rockies. This lead trough will result in a pronounced surface front arcing across the Ozarks-southern KS-northeast CO/NE Panhandle at peak heating. Additionally, there is some indication that a weak short-wave trough may top the southern Rockies ridge and turn southeast along this frontal zone during the latter half of the period. Latest model guidance suggests very strong surface heating will lead to steep 0-3km lapse rates across the central High Plains into northern OK. Forecast soundings depict convective temperatures being breached by 22-23z as surface readings rise through the upper 90s/100F. This boundary should serve as the focus for robust convection shortly after peak heating. Additionally, any storms that develop should grow upscale during the evening as the LLJ is expected to increase across the TX Panhandle into southeast KS in response to the ridge-topping short wave. Initial storm mode may be high based, but potentially supercellular in nature. However, convection should gradually expand in areal coverage and storm mergers are expected along a favorable corridor of low-level warm advection. As a result, one or more MCSs should evolve which will propagate southeast along the front toward the Ozarks during the overnight hours. Severe gusts and very large hail could be noted across the Plains before MCS maturation. ...Midwest/TN Valley... Scattered robust convection is currently ongoing ahead of the MS Valley trough, notably across IL into southern MO. This activity will propagate downstream ahead of the progressive trough and likely be ongoing at the start of the day1 period, especially across the lower OH Valley along the nose of a veered LLJ. Remnants of this convection should propagate southeast across middle TN as the LLJ weakens. With 500mb flow forecast to strengthen there is some concern this activity could advance further into the northern Gulf States than currently anticipated. Some organization is also possible which may necessitate higher severe probabilities. However, nature/extent of the early-day MCS remains a bit too uncertain to warrant more than MRGL at this time. A narrow corridor of stronger boundary-layer heating is expected across eastern IA/northwest IL into extreme southern WI by mid day. This should aid buoyancy and isolated strong/severe thunderstorms are expected to develop immediately ahead of the upper low. Hail/wind are possible with storms that evolve along this corridor of stronger instability. ..Darrow/Halbert.. 08/16/2024 Read more

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1246 AM CDT Fri Aug 16 2024 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL/SOUTHERN PLAINS INTO THE OZARKS OF NORTHWEST ARKANSAS... ...SUMMARY... Isolated-scattered severe thunderstorms are expected across portions of the central and southern Plains, extending into northwest Arkansas. Less concentrated severe is possible across the Midwest into the Tennessee Valley. ...Central/Southern Plains Region... MS Valley trough is forecast to shift into the upper Great Lakes/Midwest region by late afternoon while a dominant upper anticyclone will hold across the southern Rockies. This lead trough will result in a pronounced surface front arcing across the Ozarks-southern KS-northeast CO/NE Panhandle at peak heating. Additionally, there is some indication that a weak short-wave trough may top the southern Rockies ridge and turn southeast along this frontal zone during the latter half of the period. Latest model guidance suggests very strong surface heating will lead to steep 0-3km lapse rates across the central High Plains into northern OK. Forecast soundings depict convective temperatures being breached by 22-23z as surface readings rise through the upper 90s/100F. This boundary should serve as the focus for robust convection shortly after peak heating. Additionally, any storms that develop should grow upscale during the evening as the LLJ is expected to increase across the TX Panhandle into southeast KS in response to the ridge-topping short wave. Initial storm mode may be high based, but potentially supercellular in nature. However, convection should gradually expand in areal coverage and storm mergers are expected along a favorable corridor of low-level warm advection. As a result, one or more MCSs should evolve which will propagate southeast along the front toward the Ozarks during the overnight hours. Severe gusts and very large hail could be noted across the Plains before MCS maturation. ...Midwest/TN Valley... Scattered robust convection is currently ongoing ahead of the MS Valley trough, notably across IL into southern MO. This activity will propagate downstream ahead of the progressive trough and likely be ongoing at the start of the day1 period, especially across the lower OH Valley along the nose of a veered LLJ. Remnants of this convection should propagate southeast across middle TN as the LLJ weakens. With 500mb flow forecast to strengthen there is some concern this activity could advance further into the northern Gulf States than currently anticipated. Some organization is also possible which may necessitate higher severe probabilities. However, nature/extent of the early-day MCS remains a bit too uncertain to warrant more than MRGL at this time. A narrow corridor of stronger boundary-layer heating is expected across eastern IA/northwest IL into extreme southern WI by mid day. This should aid buoyancy and isolated strong/severe thunderstorms are expected to develop immediately ahead of the upper low. Hail/wind are possible with storms that evolve along this corridor of stronger instability. ..Darrow/Halbert.. 08/16/2024 Read more

MD 1916 CONCERNING SEVERE THUNDERSTORM WATCH 626... FOR NORTHERN ILLINOIS
Mesoscale Discussion 1916 NWS Storm Prediction Center Norman OK 1134 PM CDT Thu Aug 15 2024 Areas affected...northern Illinois Concerning...Severe Thunderstorm Watch 626... Valid 160434Z - 160600Z The severe weather threat for Severe Thunderstorm Watch 626 continues. SUMMARY...Risk for gusty/damaging outflow winds continues across portions of northern Illinois. DISCUSSION...Latest radar loop shows a bowing cluster of strong/severe storms moving eastward across portions of northern Illinois at around 40 kt. The strongest convection is crossing Stark and Peoria counties at this time, and will affect Marshall and Woodford Counties shortly. The storms are currently moving through the axis of instability (1500 to 2000 J/kg mixed-layer CAPE per RAP-based objective analysis), and as such, should maintain intensity over the next 1 to 2 hours before eventually encountering a more stable/increasingly capped airmass beginning just west of the Indiana border. Until then, local gusts in excess of 50 kt will remain possible. ..Goss.. 08/16/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...LOT...ILX...LSX...DVN... LAT...LON 40179131 40838999 41218998 41378849 40338831 39878863 40179131 Read more