WW 662 SEVERE TSTM IA MN WI LS 291935Z - 300200Z
URGENT - IMMEDIATE BROADCAST REQUESTED Severe Thunderstorm Watch Number 662 NWS Storm Prediction Center Norman OK 235 PM CDT Thu Aug 29 2024 The NWS Storm Prediction Center has issued a * Severe Thunderstorm Watch for portions of Northwest Iowa Minnesota Western and Northwest Wisconsin Lake Superior * Effective this Thursday afternoon and evening from 235 PM until 900 PM CDT. * Primary threats include... Scattered damaging wind gusts to 70 mph likely Scattered large hail and isolated very large hail events to 2 inches in diameter possible A tornado or two possible SUMMARY...Storms will continue to intensify and move east-northeastward across the region through late afternoon and early evening. Damaging winds and isolated large hail are expected to be the most common hazards, although some tornado threat may also exist near a warm front. The severe thunderstorm watch area is approximately along and 65 statute miles east and west of a line from 45 miles northwest of Ely MN to 35 miles southwest of Fairmont MN. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU2). 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. && AVIATION...A few severe thunderstorms with hail surface and aloft to 2 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 550. Mean storm motion vector 24030. ...Guyer Read more

SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0353 PM CDT Thu Aug 29 2024 Valid 311200Z - 061200Z ...Day 3/Saturday - Isolated Dry Thunderstorms... A large-scale ridge will remain in place across much of the West, while a midlevel low and related height falls begin to impinge on the Pacific Northwest. Given gradually increasing midlevel moisture along the Cascades, and terrain-driven ascent, an isolated thunderstorm cannot be entirely ruled out. However, confidence in this scenario is too low for Isolated Dry Thunderstorm probabilities at this time. Farther south, the northern periphery of a deeper moisture plume will phase with ample diurnal heating and orographic ascent over the higher terrain across portions of southern NV into southwest UT. This will promote isolated dry thunderstorms atop modestly receptive fuels during the afternoon/early evening. ...Days 4-5/Sunday-Monday - Isolated Dry Thunderstorms... The above-mentioned midlevel low will advance east-northeastward across northern CA/southwest OR on Day 4/Sunday, and continue east-northeastward across OR into ID on Day 5/Monday. Isolated dry thunderstorms will be possible across south/central OR on Day 4/Sunday, with increasing potential into the overnight hours -- as midlevel moisture/instability increases ahead of the midlevel low. Thereafter, the risk of mixed dry/wet thunderstorms will continue spreading/expanding eastward across eastern OR into ID -- in tandem with the midlevel low/trough. While fuel receptiveness across the region is uncertain, several days of boundary-layer drying (beneath the large-scale ridge) preceding this thunderstorm event will pose at least some risk of lightning-induced ignitions. Thunderstorm potential will continue across the northern Rockies on Day 6/Tuesday, though gradually increasing moisture and precipitation cast uncertainty on the overall fire-weather risk -- precluding Isolated Dry Thunderstorm probabilities. ..Weinman.. 08/29/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more

MD 2030 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN NEBRASKA INTO WESTERN IOWA
Mesoscale Discussion 2030 NWS Storm Prediction Center Norman OK 0235 PM CDT Thu Aug 29 2024 Areas affected...Eastern Nebraska into western Iowa Concerning...Severe potential...Watch unlikely Valid 291935Z - 292130Z Probability of Watch Issuance...20 percent SUMMARY...Storm coverage along the cold front should continue to increase in eastern Nebraska and eventually western Iowa. The slow push eastward of storms and potential for outflow does increase uncertainty in how organized the damaging wind threat will be. Trends will be monitored, but a watch is not expected currently. DISCUSSION...Convection has developed along the cold front in south-central Nebraska. Additional storms are likely to develop along the boundary through the afternoon given the destabilization (particularly southeast Nebraska) evident on visible satellite. With shear vectors roughly parallel to the front, storm mode should be decidedly linear. It is possible for a supercell or two to be embedded in the line, especially with northern extent. The main hazard should be damaging winds with isolated large hail more conditional on a discrete storm mode. In northwest Iowa and south-central Nebraska, outflow from convection is evident on KFSD/KUEX radar imagery. With similar potential for outflow pushing away from storms and the frontal motion continuing to the east, there is some chance many storms will be slightly elevated in nature and for corridors of greater wind damage potential to be dependent on mesoscale outflow surges. ..Wendt/Guyer.. 08/29/2024 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DMX...FSD...OAX...GID... LAT...LON 40109890 40549876 42149800 42319785 42559754 42649631 42499533 41939512 40319637 40069746 40069806 40109890 Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Thu Aug 29 2024 Valid 292000Z - 301200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF MINNESOTA AND WESTERN WISCONSIN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE UPPER MIDWEST AS WELL AS THE MID ATLANTIC.... ...SUMMARY... Severe thunderstorms are expected this afternoon and evening over portions of the Upper Midwest, with a threat for tornadoes, damaging winds, and sporadic large hail, especially across parts of Minnesota into western Wisconsin. Other severe storms are expected across the central Plains and Mid-Atlantic/Carolinas. ...20z Update... Minimal changes were made to the prior outlook. Thunder probabilities have been lowered across western parts of the central Plains behind the cold front. An isolated severe storm will be possible ahead of the front from the central Plains southward into the southern High Plains. Moderate buoyancy is supporting a fair amount of convection with some potential for damaging outflow winds or marginally severe hail. However, weaker deep-layer shear and modest large-scale ascent should keep the threat minimal prior to frontal passage later tonight. Across parts of the upper MS Valley and Midwest will maintain the Level 2/3 Slight/Enhanced as is. Scattered storms are ongoing and expected to increase in coverage through the afternoon and into this evening. Increasing deep-layer shear and partial heating ahead of the bands of storms near the cold front should allow for more robust/organized storms to gradually develop through the remainder of the afternoon. With the expected convective coverage, storm mode is trending toward more linear solutions, though moderate deep-layer shear and strong low-level turning with height may support a few embedded or semi-discrete supercell structures. Damaging winds are the primary threat, but occasional large hail and a couple of tornadoes are possible, especially near the warm front with any of the more persistent rotating features. Across the central Appalachians and Mid Atlantic, no changes were made to the severe risk area. The predominate hazard remains a few multi-cell clusters capable of damaging wind gusts. Convection ongoing over the higher terrain in western VA/PA and WV should gradually expand eastward, with some potential for consolidating outflow. See the prior outlook for more information. ..Lyons.. 08/29/2024 .PREV DISCUSSION... /ISSUED 1147 AM CDT Thu Aug 29 2024/ ...Upper Midwest/Central Plains... Have upgraded portions of central/eastern Minnesota into western Wisconsin to Enhanced Risk for a perceived greater aggregate severe risk, highlighted by a transition to an increased damaging wind potential by evening. An upper-level trough will continue generally east-northeastward from southern Saskatchewan toward Manitoba and eventually far northwest Ontario late tonight, with southern-peripheral height falls and moderately strong southwesterly winds aloft as far south as the far eastern Dakotas and Minnesota into Wisconsin. Scattered thunderstorm development is expected by mid-afternoon along the front from northern Minnesota south-southwestward into southwest Minnesota and the central Plains including eastern/southern Nebraska into northwest Kansas. The most severe-favorable ingredients are expected across central/southern Minnesota, where 2500-3500 J/kg MLCAPE will coincide with 30-40 kt effective shear. Some initial supercells can be expected with large hail. Tornado potential should be maximized across central Minnesota and possibly far western Wisconsin in vicinity of a weak surface wave/warm front-related triple point, where low-level moisture/SRH will be maximized, somewhat analogous to the South Dakota/North Dakota border vicinity yesterday late afternoon and early evening. Storms should otherwise steadily grow upscale by early evening, with storm mergers leading to quasi-linear segments and possible bows with an increased damaging wind potential across Iowa, and especially eastern Minnesota into western Wisconsin. ...Carolinas/Mid-Atlantic including parts Virginia/Pennsylvania... Scattered multicell thunderstorms are expected to form this afternoon, offering isolated damaging wind gusts and marginally severe hail. This activity will develop in a plume of rich low-level moisture, with lower-elevation surface dewpoints in the upper 60s to low 70s F. That, along with diurnal heating offsetting modest mid-level lapse rates, should support MLCAPE in the 2000-3000 J/kg range. Read more

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Thu Aug 29 2024 Valid 292000Z - 301200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF MINNESOTA AND WESTERN WISCONSIN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE UPPER MIDWEST AS WELL AS THE MID ATLANTIC.... ...SUMMARY... Severe thunderstorms are expected this afternoon and evening over portions of the Upper Midwest, with a threat for tornadoes, damaging winds, and sporadic large hail, especially across parts of Minnesota into western Wisconsin. Other severe storms are expected across the central Plains and Mid-Atlantic/Carolinas. ...20z Update... Minimal changes were made to the prior outlook. Thunder probabilities have been lowered across western parts of the central Plains behind the cold front. An isolated severe storm will be possible ahead of the front from the central Plains southward into the southern High Plains. Moderate buoyancy is supporting a fair amount of convection with some potential for damaging outflow winds or marginally severe hail. However, weaker deep-layer shear and modest large-scale ascent should keep the threat minimal prior to frontal passage later tonight. Across parts of the upper MS Valley and Midwest will maintain the Level 2/3 Slight/Enhanced as is. Scattered storms are ongoing and expected to increase in coverage through the afternoon and into this evening. Increasing deep-layer shear and partial heating ahead of the bands of storms near the cold front should allow for more robust/organized storms to gradually develop through the remainder of the afternoon. With the expected convective coverage, storm mode is trending toward more linear solutions, though moderate deep-layer shear and strong low-level turning with height may support a few embedded or semi-discrete supercell structures. Damaging winds are the primary threat, but occasional large hail and a couple of tornadoes are possible, especially near the warm front with any of the more persistent rotating features. Across the central Appalachians and Mid Atlantic, no changes were made to the severe risk area. The predominate hazard remains a few multi-cell clusters capable of damaging wind gusts. Convection ongoing over the higher terrain in western VA/PA and WV should gradually expand eastward, with some potential for consolidating outflow. See the prior outlook for more information. ..Lyons.. 08/29/2024 .PREV DISCUSSION... /ISSUED 1147 AM CDT Thu Aug 29 2024/ ...Upper Midwest/Central Plains... Have upgraded portions of central/eastern Minnesota into western Wisconsin to Enhanced Risk for a perceived greater aggregate severe risk, highlighted by a transition to an increased damaging wind potential by evening. An upper-level trough will continue generally east-northeastward from southern Saskatchewan toward Manitoba and eventually far northwest Ontario late tonight, with southern-peripheral height falls and moderately strong southwesterly winds aloft as far south as the far eastern Dakotas and Minnesota into Wisconsin. Scattered thunderstorm development is expected by mid-afternoon along the front from northern Minnesota south-southwestward into southwest Minnesota and the central Plains including eastern/southern Nebraska into northwest Kansas. The most severe-favorable ingredients are expected across central/southern Minnesota, where 2500-3500 J/kg MLCAPE will coincide with 30-40 kt effective shear. Some initial supercells can be expected with large hail. Tornado potential should be maximized across central Minnesota and possibly far western Wisconsin in vicinity of a weak surface wave/warm front-related triple point, where low-level moisture/SRH will be maximized, somewhat analogous to the South Dakota/North Dakota border vicinity yesterday late afternoon and early evening. Storms should otherwise steadily grow upscale by early evening, with storm mergers leading to quasi-linear segments and possible bows with an increased damaging wind potential across Iowa, and especially eastern Minnesota into western Wisconsin. ...Carolinas/Mid-Atlantic including parts Virginia/Pennsylvania... Scattered multicell thunderstorms are expected to form this afternoon, offering isolated damaging wind gusts and marginally severe hail. This activity will develop in a plume of rich low-level moisture, with lower-elevation surface dewpoints in the upper 60s to low 70s F. That, along with diurnal heating offsetting modest mid-level lapse rates, should support MLCAPE in the 2000-3000 J/kg range. Read more

WW 0663 Status Updates
STATUS FOR WATCH 0663 HAS NOT BEEN ISSUED YET Read more

WW 0662 Status Updates
STATUS FOR WATCH 0662 HAS NOT BEEN ISSUED YET Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Thu Aug 29 2024 Valid 311200Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST AND UPPER OHIO VALLEY... ...SUMMARY... Isolated severe risk may evolve across portions of the northeast/central Appalachians/Upper Ohio Valley area Saturday. ...Synopsis... A relatively deep upper-level trough is forecast to remain in place from eastern Canada into the Great Lakes and Northeast on Saturday. Within the large-scale trough, a weak shortwave may move through parts of the lower Great Lakes/upper Ohio Valley, while a stronger upstream shortwave will move toward the upper Great Lakes region. A cold front is expected to move eastward across parts of the Northeast and Ohio Valley. A stronger cold front will move through parts of the northern Plains and upper Great Lakes, in association with the southeastward-moving shortwave trough. ...Parts of the upper Ohio Valley into the Northeast... Scattered thunderstorms are forecast to develop Saturday along/ahead of the front across parts of NY/PA into the upper Ohio Valley region. There will be some displacement of stronger flow/shear to the north with stronger instability to the south, but the environment will likely become at least marginally supportive of organized convection across the region during the afternoon. A few stronger cells and/or small clusters may evolve with time and pose a threat of locally damaging wind and perhaps some isolated hail. ...Upper Great Lakes vicinity... Considerable uncertainty remains regarding the extent of destabilization near the strong front that is forecast to move southeastward across the upper Great Lakes region. However, favorable ascent attendant to the shortwave trough may aid in at least isolated convective development along the front during the afternoon/evening. Strengthening low/midlevel flow could support some severe threat with any deeper convection, though this potential remains uncertain and will be dependent on the magnitude of prefrontal destabilization. ..Dean.. 08/29/2024 Read more

SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Thu Aug 29 2024 Valid 311200Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST AND UPPER OHIO VALLEY... ...SUMMARY... Isolated severe risk may evolve across portions of the northeast/central Appalachians/Upper Ohio Valley area Saturday. ...Synopsis... A relatively deep upper-level trough is forecast to remain in place from eastern Canada into the Great Lakes and Northeast on Saturday. Within the large-scale trough, a weak shortwave may move through parts of the lower Great Lakes/upper Ohio Valley, while a stronger upstream shortwave will move toward the upper Great Lakes region. A cold front is expected to move eastward across parts of the Northeast and Ohio Valley. A stronger cold front will move through parts of the northern Plains and upper Great Lakes, in association with the southeastward-moving shortwave trough. ...Parts of the upper Ohio Valley into the Northeast... Scattered thunderstorms are forecast to develop Saturday along/ahead of the front across parts of NY/PA into the upper Ohio Valley region. There will be some displacement of stronger flow/shear to the north with stronger instability to the south, but the environment will likely become at least marginally supportive of organized convection across the region during the afternoon. A few stronger cells and/or small clusters may evolve with time and pose a threat of locally damaging wind and perhaps some isolated hail. ...Upper Great Lakes vicinity... Considerable uncertainty remains regarding the extent of destabilization near the strong front that is forecast to move southeastward across the upper Great Lakes region. However, favorable ascent attendant to the shortwave trough may aid in at least isolated convective development along the front during the afternoon/evening. Strengthening low/midlevel flow could support some severe threat with any deeper convection, though this potential remains uncertain and will be dependent on the magnitude of prefrontal destabilization. ..Dean.. 08/29/2024 Read more

SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1229 PM CDT Thu Aug 29 2024 Valid 301200Z - 311200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR EASTERN LOWER MICHIGAN... ...SUMMARY... Scattered strong to severe storms are possible across eastern lower Michigan on Friday, with more isolated strong/severe storms into parts of the Midwest, and also across parts of the Carolinas and Virginia into northeast Georgia. ...Synopsis... The southern portion of an relatively deep upper-level trough will move across the Upper Midwest and Great Lakes region on Friday, with the strongest part of this trough and related mid/upper-level flow expected to remain north of the international border. A cold front trailing from a deep surface low near Hudson Bay will move across parts of the Great Lakes, Midwest, mid/upper MS Valley, and south-central Great Plains. ...Parts of lower MI and OH into IN/IL/MO... Diurnal heating and relatively rich moisture will support moderate to locally strong destabilization along/ahead of the cold front during the afternoon. Scattered thunderstorm development will be possible across a broad region from lower MI and OH into the Midwest and parts of the Plains. Stronger deep-layer flow/shear will be generally displaced to the north of the front, though modest west/southwesterly flow could support isolated strong storms capable of locally damaging gusts and possibly hail. Within the broader region of isolated severe potential, a somewhat more favorable environment will be possible in the vicinity of eastern lower MI, where relatively greater low/midlevel flow (generally 20-30 kt at 850 mb and 30-40 kt at 700 mb) is forecast within the prefrontal environment. A few more-organized clusters or line segments appear possible in this area, with an attendant damaging-wind threat. A 15% wind area has been added where confidence is currently highest in the overlap of greater storm coverage and somewhat stronger flow. ...NC/VA into the southern ... Scattered thunderstorms are expected Friday afternoon across much NC and southern VA into the southern Blue Ridge vicinity, within a moist and unstable environment. Development will tend to be focused near the sea breeze, any remnant outflow boundary from D1/Thursday convection, and across the higher terrain. Deep-layer shear is expected to remain weak, which will tend to limit storm organization. However, the favorable thermodynamic profile will support a threat of locally damaging outflow winds. ..Dean.. 08/29/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1151 AM CDT Thu Aug 29 2024 Valid 301200Z - 311200Z ...NO CRITICAL AREAS... The previous forecast (see below) remains on track, and no changes were needed with this update. ..Weinman.. 08/29/2024 .PREV DISCUSSION... /ISSUED 0147 AM CDT Thu Aug 29 2024/ ...Synopsis... An upper-level ridge will remain in place across the West tomorrow (Friday) with the strongest midlevel flow confined along the Canadian border. A cold front will continue sagging southward over the middle of the country with surface high pressure building into the central Plains. While warm and dry conditions over much of the West will promote drying/curing of fuels, the large-scale pattern is not favorable strong surface winds. Some high-based thunderstorms are possible across Arizona during the afternoon hours, but fuels appear to be unreceptive, precluding the need for dry thunderstorm highlights. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1147 AM CDT Thu Aug 29 2024 Valid 291630Z - 301200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF MINNESOTA AND WESTERN WISCONSIN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-ATLANTIC REGION... ...SUMMARY... Severe thunderstorms are expected this afternoon and evening over portions of the Upper Midwest, with a threat for tornadoes, damaging winds, and sporadic large hail, especially across parts of Minnesota into western Wisconsin. Other severe storms are expected across the central Plains and Mid-Atlantic/Carolinas. ...Upper Midwest/Central Plains... Have upgraded portions of central/eastern Minnesota into western Wisconsin to Enhanced Risk for a perceived greater aggregate severe risk, highlighted by a transition to an increased damaging wind potential by evening. An upper-level trough will continue generally east-northeastward from southern Saskatchewan toward Manitoba and eventually far northwest Ontario late tonight, with southern-peripheral height falls and moderately strong southwesterly winds aloft as far south as the far eastern Dakotas and Minnesota into Wisconsin. Scattered thunderstorm development is expected by mid-afternoon along the front from northern Minnesota south-southwestward into southwest Minnesota and the central Plains including eastern/southern Nebraska into northwest Kansas. The most severe-favorable ingredients are expected across central/southern Minnesota, where 2500-3500 J/kg MLCAPE will coincide with 30-40 kt effective shear. Some initial supercells can be expected with large hail. Tornado potential should be maximized across central Minnesota and possibly far western Wisconsin in vicinity of a weak surface wave/warm front-related triple point, where low-level moisture/SRH will be maximized, somewhat analogous to the South Dakota/North Dakota border vicinity yesterday late afternoon and early evening. Storms should otherwise steadily grow upscale by early evening, with storm mergers leading to quasi-linear segments and possible bows with an increased damaging wind potential across Iowa, and especially eastern Minnesota into western Wisconsin. ...Carolinas/Mid-Atlantic including parts Virginia/Pennsylvania... Scattered multicell thunderstorms are expected to form this afternoon, offering isolated damaging wind gusts and marginally severe hail. This activity will develop in a plume of rich low-level moisture, with lower-elevation surface dewpoints in the upper 60s to low 70s F. That, along with diurnal heating offsetting modest mid-level lapse rates, should support MLCAPE in the 2000-3000 J/kg range. ..Guyer/Jewell.. 08/29/2024 Read more

SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1149 AM CDT Thu Aug 29 2024 Valid 291700Z - 301200Z ...NO CRITICAL AREAS... No changes were made to the outlook. For details, see the previous discussion below. ..Weinman.. 08/29/2024 .PREV DISCUSSION... /ISSUED 0145 AM CDT Thu Aug 29 2024/ ...Synopsis... An upper-level low will move eastward across southern Canada today while an upper-level ridge builds over the western CONUS. At the surface, a cold front will move southeastward across the northern and central Plains as high pressure settles over the northern Intermountain West. While afternoon RH values below 20% will be widespread across the West, the pattern is not favorable for strong sustained surface wind speeds, limiting the overall fire weather threat today. ...Please see www.spc.noaa.gov/fire for graphic product... Read more

No watches are valid as of Thu Aug 29 14:04:01 UTC 2024.

No Mesoscale Discussions are in effect as of Thu Aug 29 14:04:01 UTC 2024.

SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0749 AM CDT Thu Aug 29 2024 Valid 291300Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE UPPER MISSISSIPPI VALLEY REGION... ...SUMMARY... Severe thunderstorms are most probable this afternoon and evening over portions of the upper Mississippi Valley region, with a threat for tornadoes, damaging to severe gusts, and sporadic large hail. ...Synopsis... The mid/upper-level pattern will be characterized by a progressive belt of westerlies across the northern tier of states, and messy area of ridging across the south-central/southeastern CONUS, suffused with numerous small vorticity maxima and a few slow-moving MCVs. In that northern stream, a strong shortwave trough -- with embedded closed cyclone now located over extreme southern SK -- will move eastward to southern MB and the Dakotas by 00Z. The trough should deamplify overnight and eject northeastward to northwesternmost ON by 12Z, while a positively tilted trailing portion of the trough lingers across parts of WI/IA/NE/KS. Farther east, a weak perturbation -- evident in moisture-channel imagery from just north of Lake Huron in ON to astern Lake Superior -- will weaken gradually and move southeastward across the remainder of ON to NY and New England by the end of the period. An even weaker shortwave trough -- initially extending from central OH across southern IN -- should move slowly southeastward into the central Appalachians. At the surface, 11Z analysis showed a triple-point low over northeastern SD, with a warm front southeastward over southwestern MN and northern IA, becoming quasistationary to a weak cold front over central IL, southern IN, central OH, central PA , and NJ. The eastern part of the front should drift southward over the Mid- Atlantic through the period, while the western part proceeds northeastward across MN/WI as a warm front. A cold front was drawn from the low southwestward over west-central NE and east-central CO. By 00Z, the cold front should reach northern/central MN, northwestern IA, eastern NE, north-central/southwestern KS, and parts of southeastern CO/northeastern NM. By 12Z, the front should extend across parts of Lake Superior, WI, northern/western MO, southeastern KS, northern/western OK, northwest TX, and southeastern NM. ...Upper Mississippi Valley to central Plains... Scattered thunderstorms should develop along/ahead of the surface cold front -- earliest (around midday) where deep-layer lift is strongest over northern/central MN, then later where stronger capping, weaker upper support, but stronger heating will be present from around the Missouri Valley southwestward. All severe hazards will be possible with greatest vertical shear supporting a threat of supercells in MN and perhaps northern IA for the first few hours of the convective cycle. If supercells can remain discrete/mature long enough before the quasi-linear evolution occurs, tornado potential could be relatively maximized over central MN where the overlap of large buoyancy, low LCL and greatest SRH is forecast. Activity overall should evolve into a line of numerous thunderstorms by late afternoon and evening, with severe gusts and marginal hail becoming the dominant concerns. Convection should weaken over eastern and southern parts of the "marginal area tonight, while moving into a less-unstable, larger-CINH airmass from WI to southern KS. Although the main mid/upper cyclone/trough will be pivoting northeastward over Canada, the southeastern rim of associated height falls and mass response will pass across the "slight risk" outlook area. This should back the near-surface flow ahead of the front enough to enlarge low-level hodographs and shear vectors, and to strengthen effective-shear magnitudes into the 30-40-kt range (decreasing southward over IA). A deep troposphere, rich boundary- layer moisture with dewpoints commonly in the upper 60s to low 70s F, and steep low-level lapse rates, should support MLCAPE commonly in the 2500-3500 J/kg range, and locally nearing 5000 J/kg, within the northward-narrowing warm sector, over IA/MN part of the outlook. Farther southwest, buoyancy will weaken due to somewhat less moisture content and greater boundary-layer mixing. ...VA/NC to southern PA... Scattered multicell thunderstorms are expected to form this afternoon along and south of the front over the outlook area, offering isolated gusts near severe limits and marginally severe hail. This activity will develop in a plume of rich low-level moisture, with lower-elevation surface dewpoints in the upper 60s to low 70s F. That, along with diurnal heating offsetting modest midlevel lapse rates, should support MLCAPE in the 2000-3000 J/kg range. Weak deep-layer flow/shear should keep activity relatively disorganized, with pulse severe possible. ..Edwards/Bentley.. 08/29/2024 Read more

Day 4-8 Outlook
Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Thu Aug 29 2024 Valid 011200Z - 061200Z ...DISCUSSION... Medium-range/global models are in reasonably good agreement with respect to synoptic-scale features across the U.S. through about Day 6/Tuesday. Late in the period, models begin deviating with respect to their handling of an upper low, which through the first half of the period is progged to be moving in a slow, anticyclonic arc around northern fringes of a western and central U.S. ridge. As this feature crests the ridge, moving across the northern Intermountain region Day 7/Wednesday, model solutions begin to diverge with respect to progression of the system, with divergence continuing through Day8. Therefore, while some severe risk may accompany the advance of this feature toward/into the north-central U.S. late in the period, uncertainty precludes any further assessment of this potential. Meanwhile early in the period, an upper trough will shift across the northeastern quarter of the country Day 4/Sunday. An associated cold front is progged to advance across the Northeast/Mid-Atlantic region, but with preceding low-level moisture likely already swept off the New England Coast by a prior frontal passage. As such, it appears that only a limited potential for stronger storms will exist along trailing portions of the front farther south (from the Mid-Atlantic vicinity westward into the Tennessee Valley area) with stronger flow aloft remaining farther to the north. Days 5-6 and beyond, the front will continue sagging southward across the Southeast and Gulf Coast States, as a Canadian surface high settles southeastward into the Plains/Great Lakes/Midwest. While convection can be expected near and south of this boundary, stronger flow aloft will remain well north of this region, thus precluding organized severe potential. Read more

SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Thu Aug 29 2024 Valid 311200Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST AND UPPER OHIO VALLEY... ...SUMMARY... Local/limited severe risk may evolve across portions of the northeast/central Appalachians/Upper Ohio Valley area Saturday. ...Synopsis... As an upper trough shifts slowly eastward across eastern Canada and the Great Lakes region, an embedded/short-wave trough within the broader cyclonic flow field is progged to shift quickly southeastward out of central Canada and into the Upper Great Lakes region. At the surface, a weakening cold front, initially stretching from the Lower Great Lakes area across the Midwest, will make gradual southeastward progress across the Appalachians. Meanwhile, a stronger/reinforcing front -- associated with the aforementioned short-wave trough -- is forecast to shift southeastward out of Canada across the north-central U.S. during the first half of the period. Overnight, the front is progged to continue a rapid advance eastward across the Upper Great Lakes, and southward into the central Plains. ...Parts of the Upper Ohio Valley and Northeast... As the initial/weakening cold front crosses the Lower Great Lakes/Appalachians and Ohio Valley region, showers and thunderstorms are expected to increase through the afternoon in the vicinity of the frontal zone. Stronger flow aloft will remain limited to areas from Pennsylvania northward -- where instability should remain weak. Meanwhile, though more substantial instability is expected across areas farther south/southwest, weaker shear should limit convective intensity. As a result, the overall severe risk appears likely to remain marginal/isolated as a result, and therefore will introduce only 5% probability/MRGL risk -- from the New York/Pennsylvania vicinity to Ohio/West Virginia/northern and western Virginia -- at this time. Marginal hail and locally strong wind gusts will be possible, mainly during the afternoon and early evening hours. ..Goss.. 08/29/2024 Read more

SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 0147 AM CDT Thu Aug 29 2024 Valid 301200Z - 311200Z ...NO CRITICAL AREAS... ...Synopsis... An upper-level ridge will remain in place across the West tomorrow (Friday) with the strongest midlevel flow confined along the Canadian border. A cold front will continue sagging southward over the middle of the country with surface high pressure building into the central Plains. While warm and dry conditions over much of the West will promote drying/curing of fuels, the large-scale pattern is not favorable strong surface winds. Some high-based thunderstorms are possible across Arizona during the afternoon hours, but fuels appear to be unreceptive, precluding the need for dry thunderstorm highlights. ..Jirak.. 08/29/2024 ...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 0145 AM CDT Thu Aug 29 2024 Valid 291200Z - 301200Z ...NO CRITICAL AREAS... ...Synopsis... An upper-level low will move eastward across southern Canada today while an upper-level ridge builds over the western CONUS. At the surface, a cold front will move southeastward across the northern and central Plains as high pressure settles over the northern Intermountain West. While afternoon RH values below 20% will be widespread across the West, the pattern is not favorable for strong sustained surface wind speeds, limiting the overall fire weather threat today. ..Jirak.. 08/29/2024 ...Please see www.spc.noaa.gov/fire for graphic product... Read more