Severe Storms

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0743 AM CDT Fri Jul 18 2025 Valid 181300Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF VIRGINIA/NORTH CAROLINA...AND PARTS OF CENTRAL/EASTERN NEBRASKA...SOUTHEAST SOUTH DAKOTA...SOUTHWEST MINNESOTA...AND WESTERN/CENTRAL IOWA... ...SUMMARY... Scattered severe thunderstorms with large hail, damaging winds, and a few tornadoes are possible across parts of the Corn Belt in Iowa, Minnesota, Nebraska, and South Dakota this evening into tonight. Scattered damaging winds are possible across parts of Virginia and North Carolina this afternoon. ...Virginia/North Carolina to the Mid-South... A generally west-east oriented quasi-stationary front reinforced by outflow from earlier convection should serve as a low-level forcing mechanism for thunderstorm development this afternoon from parts of VA/NC westward to the Mid-South and vicinity. A seasonably moist airmass will be present today along/south of this front, with surface dewpoints generally ranging from the upper 60s in higher elevations to mid 70s elsewhere. Even though mid-level lapse rates are expected to remain rather modest, ample daytime heating of the moist low-level airmass will contribute to sizable MLCAPE by early to mid afternoon. With a subtropical anticyclone centered off the Southeast Atlantic Coast and stronger flow aloft associated with various mid-level perturbations expected to remain over the Great Lakes/Northeast, large-scale ascent in the vicinity of the surface front will be nebulous at best. Regardless, scattered to numerous thunderstorms should develop along/near this boundary through the afternoon, while spreading generally eastward this evening. With modest mid-level westerly flow forecast, deep-layer shear appears marginal for thunderstorm organization. The greatest threat for scattered damaging winds should focus across parts of VA/NC this afternoon and early evening, where semi-organized clusters and short line segments appear possible given slightly stronger deep-layer shear. Otherwise, isolated damaging winds may occur even with less organized convection farther west towards parts of the TN Valley/Mid-South, as steepened low-level lapse rates potentially support microbursts. There does appear to be a gap in scattered convective coverage across parts of MO and vicinity, where the Marginal Risk has been removed with this update. ...South Dakota/Nebraska into Minnesota/Iowa... Elevated convection across parts of SD may continue to pose an isolated hail threat this morning, before it eventually weakens with the gradual lessening of a southerly low-level jet. A belt of strong westerly mid-level flow will remain in place over the northern tier of the CONUS from MT eastward towards the Great Lakes. Gradual low-level moistening is forecast through this evening ahead of a weak front forecast to be in place over the eastern Dakotas into western NE. Diurnal heating and modestly steepened mid-level lapse rates will contribute to moderate to strong MLCAPE across parts of NE/southeast SD into IA. But, nebulous forcing for ascent and residual capping should tend to suppress surface-based convective development across these areas for much of the day. Occasional severe hail may occur with mainly elevated convection to the north of the front in MN. A gradually strengthening southerly low-level jet this evening (mainly after 00Z) should aid in convective initiation along/near the front from central/northeast NE into southeast SD/southwest MN. Various NAM/RAP forecast soundings across this region suggest ample instability and strong deep-layer shear will be present to support supercells with attendant large hail threat initially. Low-level shear should also be strong enough for a tornado threat with these supercells, although there may be a fairly narrow spatial/temporal window for convection to remain discrete this evening. Upscale growth into a bowing cluster should occur through mid to late evening, with a threat for mainly scattered severe/damaging winds as this convection tracks into parts of IA overnight, before eventually weakening early Saturday morning. ...Great Basin into Wyoming and Far Southern Montana... Initially high-based convection should develop this afternoon across parts of the Great Basin into WY as modest ascent associated with a weak/low-amplitude mid-level impulse spreads eastward across these areas. While low-level moisture and deep-layer shear will remain limited, steepened low/mid-level lapse rates amid a very well-mixed boundary layer should support isolated severe gusts with any thunderstorms that can be sustained amid weak instability. Somewhat greater low-level moisture should be present this afternoon across parts of southern MT into northern/eastern WY, generally along/east of the Bighorn/Laramie Mountains. Isolated severe hail may occur with marginal supercells given greater instability/shear forecast across these areas. ..Gleason/Bentley.. 07/18/2025 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Fri Jul 18 2025 Valid 211200Z - 261200Z ...DISCUSSION... Medium-range guidance suggests that mid/upper ridging may remain a prominent influence across much of the central and southeastern U.S. through this period. Beneath its northern periphery, across parts of the northern Great Plains into Upper Midwest and Great Lakes/Ohio Valley, it appears that a seasonably moist boundary-layer may become characterized by moderate to strong diurnal destabilization each day. However, forcing for ascent to support convective development remains unclear, and might be largely dependent on sub-synoptic features with low predictability, particularly at this extended range. Sizable spread exists among the output concerning synoptic features within the westerlies, as well. However, there appears some signal that a short wave perturbation, emerging either from the Pacific Northwest or northwestern Canadian provinces early next week, could be accompanied by an eastward advecting plume of elevated mixed-layer air, low-level moistening and strengthening lower/mid-tropospheric wind fields across parts of the Upper Midwest/Great Lakes toward the St. Lawrence Valley/Northeast late next Wednesday into Friday. It might not be out of the question that this regime could become supportive of one or two sustained, organized clusters of storms capable of producing swaths of damaging winds and some hail. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Fri Jul 18 2025 Valid 211200Z - 261200Z ...DISCUSSION... Medium-range guidance suggests that mid/upper ridging may remain a prominent influence across much of the central and southeastern U.S. through this period. Beneath its northern periphery, across parts of the northern Great Plains into Upper Midwest and Great Lakes/Ohio Valley, it appears that a seasonably moist boundary-layer may become characterized by moderate to strong diurnal destabilization each day. However, forcing for ascent to support convective development remains unclear, and might be largely dependent on sub-synoptic features with low predictability, particularly at this extended range. Sizable spread exists among the output concerning synoptic features within the westerlies, as well. However, there appears some signal that a short wave perturbation, emerging either from the Pacific Northwest or northwestern Canadian provinces early next week, could be accompanied by an eastward advecting plume of elevated mixed-layer air, low-level moistening and strengthening lower/mid-tropospheric wind fields across parts of the Upper Midwest/Great Lakes toward the St. Lawrence Valley/Northeast late next Wednesday into Friday. It might not be out of the question that this regime could become supportive of one or two sustained, organized clusters of storms capable of producing swaths of damaging winds and some hail. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Fri Jul 18 2025 Valid 211200Z - 261200Z ...DISCUSSION... Medium-range guidance suggests that mid/upper ridging may remain a prominent influence across much of the central and southeastern U.S. through this period. Beneath its northern periphery, across parts of the northern Great Plains into Upper Midwest and Great Lakes/Ohio Valley, it appears that a seasonably moist boundary-layer may become characterized by moderate to strong diurnal destabilization each day. However, forcing for ascent to support convective development remains unclear, and might be largely dependent on sub-synoptic features with low predictability, particularly at this extended range. Sizable spread exists among the output concerning synoptic features within the westerlies, as well. However, there appears some signal that a short wave perturbation, emerging either from the Pacific Northwest or northwestern Canadian provinces early next week, could be accompanied by an eastward advecting plume of elevated mixed-layer air, low-level moistening and strengthening lower/mid-tropospheric wind fields across parts of the Upper Midwest/Great Lakes toward the St. Lawrence Valley/Northeast late next Wednesday into Friday. It might not be out of the question that this regime could become supportive of one or two sustained, organized clusters of storms capable of producing swaths of damaging winds and some hail. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Fri Jul 18 2025 Valid 211200Z - 261200Z ...DISCUSSION... Medium-range guidance suggests that mid/upper ridging may remain a prominent influence across much of the central and southeastern U.S. through this period. Beneath its northern periphery, across parts of the northern Great Plains into Upper Midwest and Great Lakes/Ohio Valley, it appears that a seasonably moist boundary-layer may become characterized by moderate to strong diurnal destabilization each day. However, forcing for ascent to support convective development remains unclear, and might be largely dependent on sub-synoptic features with low predictability, particularly at this extended range. Sizable spread exists among the output concerning synoptic features within the westerlies, as well. However, there appears some signal that a short wave perturbation, emerging either from the Pacific Northwest or northwestern Canadian provinces early next week, could be accompanied by an eastward advecting plume of elevated mixed-layer air, low-level moistening and strengthening lower/mid-tropospheric wind fields across parts of the Upper Midwest/Great Lakes toward the St. Lawrence Valley/Northeast late next Wednesday into Friday. It might not be out of the question that this regime could become supportive of one or two sustained, organized clusters of storms capable of producing swaths of damaging winds and some hail. Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0354 AM CDT Fri Jul 18 2025 Valid 211200Z - 261200Z ...DISCUSSION... Medium-range guidance suggests that mid/upper ridging may remain a prominent influence across much of the central and southeastern U.S. through this period. Beneath its northern periphery, across parts of the northern Great Plains into Upper Midwest and Great Lakes/Ohio Valley, it appears that a seasonably moist boundary-layer may become characterized by moderate to strong diurnal destabilization each day. However, forcing for ascent to support convective development remains unclear, and might be largely dependent on sub-synoptic features with low predictability, particularly at this extended range. Sizable spread exists among the output concerning synoptic features within the westerlies, as well. However, there appears some signal that a short wave perturbation, emerging either from the Pacific Northwest or northwestern Canadian provinces early next week, could be accompanied by an eastward advecting plume of elevated mixed-layer air, low-level moistening and strengthening lower/mid-tropospheric wind fields across parts of the Upper Midwest/Great Lakes toward the St. Lawrence Valley/Northeast late next Wednesday into Friday. It might not be out of the question that this regime could become supportive of one or two sustained, organized clusters of storms capable of producing swaths of damaging winds and some hail. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Jul 18 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS PARTS OF THE MID ATLANTIC INTO OHIO AND MISSOURI VALLEYS... ...SUMMARY... Scattered strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the Mid Atlantic into Ohio and Missouri Valleys Sunday into Sunday night. ...Discussion... One notable mid-level perturbation is forecast to accelerate northeastward out of the Pacific Northwest into the eastern Canadian Prairies, but another digging short wave will maintain larger-scale troughing across the Pacific Northwest through this period. Downstream, a significant mid-level perturbation emerging from the Hudson Bay vicinity is forecast to continue digging southeastward, across the St. Lawrence Valley and lower Great Lakes region into the Northeast. As this occurs, a reinforcing intrusion of cooler and drier air likely will progress southeast of the Great Lakes region through much of the northern and middle Atlantic Seaboard, while generally stalling across the lower Ohio through middle Missouri Valleys and adjacent portions of the Great Plains, beneath the northern periphery of fairly prominent mid-level ridging centered over the northern Gulf/Gulf coast vicinity. ...Northern Great Plains into Mid Atlantic... The frontal zone, and surface troughing to the lee of the Rockies, will provide potential focus for strong to severe thunderstorm development Sunday through Sunday night. This could include upscale growing clusters with potential to produce strong to severe wind gusts and some hail. However, relatively warm mid-level temperatures may tend to inhibit thunderstorm development, and the risk for severe weather, where potential instability is forecast to become strongest (including mixed-layer CAPE in excess of 2000-3000 J/kg) across parts of the middle into lower Missouri Valley. With the front also tending to become displaced to the south of the stronger westerlies in the East, and sub-synoptic perturbations likely to be a significant contributor to thunderstorm development, considerable uncertainties linger concerning the severe weather potential for this period. ..Kerr.. 07/18/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Jul 18 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS PARTS OF THE MID ATLANTIC INTO OHIO AND MISSOURI VALLEYS... ...SUMMARY... Scattered strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the Mid Atlantic into Ohio and Missouri Valleys Sunday into Sunday night. ...Discussion... One notable mid-level perturbation is forecast to accelerate northeastward out of the Pacific Northwest into the eastern Canadian Prairies, but another digging short wave will maintain larger-scale troughing across the Pacific Northwest through this period. Downstream, a significant mid-level perturbation emerging from the Hudson Bay vicinity is forecast to continue digging southeastward, across the St. Lawrence Valley and lower Great Lakes region into the Northeast. As this occurs, a reinforcing intrusion of cooler and drier air likely will progress southeast of the Great Lakes region through much of the northern and middle Atlantic Seaboard, while generally stalling across the lower Ohio through middle Missouri Valleys and adjacent portions of the Great Plains, beneath the northern periphery of fairly prominent mid-level ridging centered over the northern Gulf/Gulf coast vicinity. ...Northern Great Plains into Mid Atlantic... The frontal zone, and surface troughing to the lee of the Rockies, will provide potential focus for strong to severe thunderstorm development Sunday through Sunday night. This could include upscale growing clusters with potential to produce strong to severe wind gusts and some hail. However, relatively warm mid-level temperatures may tend to inhibit thunderstorm development, and the risk for severe weather, where potential instability is forecast to become strongest (including mixed-layer CAPE in excess of 2000-3000 J/kg) across parts of the middle into lower Missouri Valley. With the front also tending to become displaced to the south of the stronger westerlies in the East, and sub-synoptic perturbations likely to be a significant contributor to thunderstorm development, considerable uncertainties linger concerning the severe weather potential for this period. ..Kerr.. 07/18/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Jul 18 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS PARTS OF THE MID ATLANTIC INTO OHIO AND MISSOURI VALLEYS... ...SUMMARY... Scattered strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the Mid Atlantic into Ohio and Missouri Valleys Sunday into Sunday night. ...Discussion... One notable mid-level perturbation is forecast to accelerate northeastward out of the Pacific Northwest into the eastern Canadian Prairies, but another digging short wave will maintain larger-scale troughing across the Pacific Northwest through this period. Downstream, a significant mid-level perturbation emerging from the Hudson Bay vicinity is forecast to continue digging southeastward, across the St. Lawrence Valley and lower Great Lakes region into the Northeast. As this occurs, a reinforcing intrusion of cooler and drier air likely will progress southeast of the Great Lakes region through much of the northern and middle Atlantic Seaboard, while generally stalling across the lower Ohio through middle Missouri Valleys and adjacent portions of the Great Plains, beneath the northern periphery of fairly prominent mid-level ridging centered over the northern Gulf/Gulf coast vicinity. ...Northern Great Plains into Mid Atlantic... The frontal zone, and surface troughing to the lee of the Rockies, will provide potential focus for strong to severe thunderstorm development Sunday through Sunday night. This could include upscale growing clusters with potential to produce strong to severe wind gusts and some hail. However, relatively warm mid-level temperatures may tend to inhibit thunderstorm development, and the risk for severe weather, where potential instability is forecast to become strongest (including mixed-layer CAPE in excess of 2000-3000 J/kg) across parts of the middle into lower Missouri Valley. With the front also tending to become displaced to the south of the stronger westerlies in the East, and sub-synoptic perturbations likely to be a significant contributor to thunderstorm development, considerable uncertainties linger concerning the severe weather potential for this period. ..Kerr.. 07/18/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Jul 18 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS PARTS OF THE MID ATLANTIC INTO OHIO AND MISSOURI VALLEYS... ...SUMMARY... Scattered strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the Mid Atlantic into Ohio and Missouri Valleys Sunday into Sunday night. ...Discussion... One notable mid-level perturbation is forecast to accelerate northeastward out of the Pacific Northwest into the eastern Canadian Prairies, but another digging short wave will maintain larger-scale troughing across the Pacific Northwest through this period. Downstream, a significant mid-level perturbation emerging from the Hudson Bay vicinity is forecast to continue digging southeastward, across the St. Lawrence Valley and lower Great Lakes region into the Northeast. As this occurs, a reinforcing intrusion of cooler and drier air likely will progress southeast of the Great Lakes region through much of the northern and middle Atlantic Seaboard, while generally stalling across the lower Ohio through middle Missouri Valleys and adjacent portions of the Great Plains, beneath the northern periphery of fairly prominent mid-level ridging centered over the northern Gulf/Gulf coast vicinity. ...Northern Great Plains into Mid Atlantic... The frontal zone, and surface troughing to the lee of the Rockies, will provide potential focus for strong to severe thunderstorm development Sunday through Sunday night. This could include upscale growing clusters with potential to produce strong to severe wind gusts and some hail. However, relatively warm mid-level temperatures may tend to inhibit thunderstorm development, and the risk for severe weather, where potential instability is forecast to become strongest (including mixed-layer CAPE in excess of 2000-3000 J/kg) across parts of the middle into lower Missouri Valley. With the front also tending to become displaced to the south of the stronger westerlies in the East, and sub-synoptic perturbations likely to be a significant contributor to thunderstorm development, considerable uncertainties linger concerning the severe weather potential for this period. ..Kerr.. 07/18/2025 Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0222 AM CDT Fri Jul 18 2025 Valid 201200Z - 211200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SUNDAY ACROSS PARTS OF THE MID ATLANTIC INTO OHIO AND MISSOURI VALLEYS... ...SUMMARY... Scattered strong thunderstorm development may pose at least some risk for severe wind and hail across parts of the Mid Atlantic into Ohio and Missouri Valleys Sunday into Sunday night. ...Discussion... One notable mid-level perturbation is forecast to accelerate northeastward out of the Pacific Northwest into the eastern Canadian Prairies, but another digging short wave will maintain larger-scale troughing across the Pacific Northwest through this period. Downstream, a significant mid-level perturbation emerging from the Hudson Bay vicinity is forecast to continue digging southeastward, across the St. Lawrence Valley and lower Great Lakes region into the Northeast. As this occurs, a reinforcing intrusion of cooler and drier air likely will progress southeast of the Great Lakes region through much of the northern and middle Atlantic Seaboard, while generally stalling across the lower Ohio through middle Missouri Valleys and adjacent portions of the Great Plains, beneath the northern periphery of fairly prominent mid-level ridging centered over the northern Gulf/Gulf coast vicinity. ...Northern Great Plains into Mid Atlantic... The frontal zone, and surface troughing to the lee of the Rockies, will provide potential focus for strong to severe thunderstorm development Sunday through Sunday night. This could include upscale growing clusters with potential to produce strong to severe wind gusts and some hail. However, relatively warm mid-level temperatures may tend to inhibit thunderstorm development, and the risk for severe weather, where potential instability is forecast to become strongest (including mixed-layer CAPE in excess of 2000-3000 J/kg) across parts of the middle into lower Missouri Valley. With the front also tending to become displaced to the south of the stronger westerlies in the East, and sub-synoptic perturbations likely to be a significant contributor to thunderstorm development, considerable uncertainties linger concerning the severe weather potential for this period. ..Kerr.. 07/18/2025 Read more

MD 1706 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHEAST MONTANA...FAR NORTHEAST WYOMING...AND NORTHWEST SOUTH DAKOTA
Mesoscale Discussion 1706 NWS Storm Prediction Center Norman OK 0101 AM CDT Fri Jul 18 2025 Areas affected...southeast Montana...far northeast Wyoming...and northwest South Dakota Concerning...Severe potential...Watch unlikely Valid 180601Z - 180730Z Probability of Watch Issuance...20 percent SUMMARY...A few strong to isolated severe elevated supercells are possible early this morning. DISCUSSION...Earlier storm activity across Montana has mostly weakened below severe limits. However, as the nocturnal low-level jet strengthens across the northern Plains, additional storms will develop. Early radar echos across far southeast Montana and far southwest North Dakota are likely the beginning of the overnight elevated storm threat. Sampling of the low-level jet is somewhat meager, but at least some evidence of it strengthening can be seen on the KBIS VWP. Weak to moderate instability southwest of a frontal zone will support robust updraft development. Strong effective shear (50 to 60 knots) will support the potential for supercells with some hail threat (given moderately steep mid-level lapse rates from the 00Z KUNR VWP). Overall a lack of greater instability along the frontal zone (where storms are anticipated) should limit the overall threat. A few strong to isolated severe supercells with some large hail are possible, but the magnitude and areal extent should remain too low to warrant a watch. ..Bentley/Gleason.. 07/18/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR...BYZ... LAT...LON 45720540 45930464 45980405 45930296 45760157 45750149 45100065 44490111 44390281 44570437 44770504 45070537 45720540 MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN Read more

MD 1705 CONCERNING SEVERE THUNDERSTORM WATCH 522...523... FOR PARTS OF EASTERN MT INTO SOUTHWEST ND/NORTHWEST SD
Mesoscale Discussion 1705 NWS Storm Prediction Center Norman OK 1141 PM CDT Thu Jul 17 2025 Areas affected...Parts of eastern MT into southwest ND/northwest SD Concerning...Severe Thunderstorm Watch 522...523... Valid 180441Z - 180615Z The severe weather threat for Severe Thunderstorm Watch 522, 523 continues. SUMMARY...An isolated severe wind/hail threat may persist into late tonight. DISCUSSION...Earlier supercells have weakened across east-central MT late this evening, but other strong cells are approaching southeast MT. While CINH is gradually increasing across the region, MUCAPE approaching 1000 J/kg and strong deep-layer shear will continue to support some organized convection late tonight, accompanied by a threat for isolated severe wind and hail. Ongoing convection may eventually approach parts of southwest ND and northwest SD into the early overnight hours. Even if the ongoing storms continue to weaken, redevelopment of elevated convection will be possible across parts of the Dakotas within a low-level warm advection regime. The need for downstream watch issuance is very uncertain, due to the weakening trend with ongoing storms, and potentially limited severe coverage with the later elevated convection. Trends will continue to be monitored for any uptick in storm organization and intensity. ..Dean/Hart.. 07/18/2025 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...ABR...BIS...UNR...BYZ...GGW... LAT...LON 46240692 46440687 46620674 46760660 47190569 47150403 46450221 45090168 44720226 44600298 44890408 45580609 46110693 46240692 MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more

SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Fri Jul 18 2025 Valid 191200Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY INTO SATURDAY NIGHT ACROSS PARTS OF EASTERN IOWA...SOUTHERN WISCONSIN...NORTHERN AND CENTRAL ILLINOIS AND INDIANA...CENTRAL AND SOUTHERN LOWER MICHIGAN...NORTHERN AND WESTERN OHIO...PARTS OF NORTHWESTERN PENNSYLVANIA AND WESTERN NEW YORK STATE... ...SUMMARY... Strong thunderstorms, including one or two organizing clusters, are possible across southern portions of the Great Lakes region and adjacent portions of the Ohio Valley Saturday into Saturday night, with more widely scattered strong thunderstorm development across the northern Rockies into adjacent high plains. ...Discussion... Models indicate that at least some amplification to the mid/upper flow across the northern tier of the U.S. is probable during this period. It appears that this will include digging troughing across the Pacific Northwest through northern Rockies, downstream of increasingly prominent ridging building across the northeastern Pacific. Farther east, troughing is forecast to dig across and to the east of the Great Lakes, in advance of significant troughing within a separate branch of westerlies, pivoting southeast of Hudson Bay. In lower levels, the better defined remnants of an ongoing cold frontal intrusion to the lee of the Rockies, perhaps aided by stronger differential surface heating during the day Saturday, may shift east of the middle Mississippi through the lower Ohio Valley. At the same time, a reinforcing intrusion of cooler and drier air is forecast to advance across and south of the Upper Midwest and Great Lakes, probably in the wake of a weak eastward migrating surface low. ...Midwest through Great Lakes/Ohio Valley... Model depictions concerning synoptic and sub-synoptic features, including potential convective evolution remain rather varied. In general, it appears that low-level moistening ahead of the reinforcing cold front will contribute to moderate destabilization as far north as the southern Great Lakes during the day Saturday. On the southern fringe of the stronger westerlies, 30-50 kt flow in the 850-500 mb layer across southern Wisconsin and Lower Michigan into the lower Great Lakes will contribute to potential for organized convective development. This may include a couple of supercells and perhaps an upscale growing cluster. Although mid-level lapse rates may be modest, this may be accompanied by some risk for hail, in addition to strong to severe surface gusts and perhaps a tornado or two. Southwestward toward the middle Mississippi into Ohio Valleys, deep-layer mean wind fields are likely to be weaker, but shear beneath west-northwesterly mid-level flow may still support potential for organized thunderstorm development, in the presence of a seasonably moist boundary-layer becoming characterized by sizable CAPE with daytime heating. Forcing for this activity remains unclear, and probably will hinge on convectively generated or augmented perturbations migrating around the northern periphery of mid/upper ridging encompassing much of the central and southern tier of the U.S. to the east of the Rockies. ...Lee of the northern Rockies... Downstream of the digging mid/upper troughing across the Northwest, moisture return to deepening lee surface troughing is forecast to contribute to at least a narrow corridor of moderate to large mixed-layer CAPE, in the presence of steep lower/mid-tropospheric lapse rates. Veering of winds with height probably will contribute to sufficient shear for organized thunderstorm development, including supercells, as widely scattered to scattered thunderstorms develop off the higher terrain into the high plains late Saturday afternoon and evening. It is possible that severe weather probabilities could still be increased in later outlooks for this period. ..Kerr.. 07/18/2025 Read more