Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Aug 05 2024 05:33:55 ACUS01 KWNS 050533 SWODY1 SPC AC 050532 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1232 AM CDT Mon Aug 05 2024 Valid 051200Z - 061200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN FLORIDA...SOUTHEAST GEORGIA AND COASTAL SOUTH CAROLINA...OVER PORTIONS OF THE UPPER MIDWEST...AND FROM THE UPPER OHIO VALLEY INTO THE NORTHEAST... ....SUMMARY... Severe thunderstorms are possible today and tonight from the Upper Ohio Valley into New England, across portions of the Upper Midwest, and from northern Florida into southern Georgia and southeast South Carolina. ....Synopsis... Several shortwave impulses/convectively enhanced vorticity maxima will migrate through a broad area of northwesterly upper level flow from the northern Plains to the Great Lakes. Meanwhile, an shortwave trough embedded within the Hudson Bay upper cyclone will pivot east/southeast toward the Northeast. Meanwhile, an upper shortwave trough is forecast to overspread the Pacific Northwest, resulting in enhanced westerly flow across the northern Rockies. Meanwhile, Hurricane Debbie is forecast by the National Hurricane Center to make landfall along the Florida Big Bend and move northeast into southeast GA. Otherwise, an expansive upper anticyclone will overspread much of the Great Basin/Four Corners region into the Lower MS Valley. ....IN/OH/MI into the Northeast... West/southwesterly mid/upper flow will increase through the day as the upper shortwave trough moves east across Ontario and into Quebec. While deep-layer flow will mostly be unidirectional, increasing midlevel flow will support effective shear magnitudes around 35 kt. Midlevel lapse rates will remain poor, but a moist airmass with dewpoints in the mid/upper 60s F will foster MLCAPE values around 1000-2000 J/kg. Furthermore, heating into the mid 80s to low 90s F will steepen low-level lapse rates. Forecast soundings indicate supercell wind profiles, with forecast hodographs becoming elongated/straight above around 2.5 km. This environment should support a mix of supercells and clusters capable of damaging gusts and isolated large hail. Further west across southern Lower MI, northern IN/OH and western PA, stronger instability is forecast. A couple of rounds of thunderstorms will be possible as an initial shortwave moves across the area during the morning. Convection is then expected to form during the afternoon and evening as a surface cold front sags southward across the Great Lakes. While greater instability is forecast, the stronger vertical shear will remain displaced to the northeast across New England. Furthermore, morning convection could be detrimental to afternoon storms depending how prevalent convection is and how much cloud cover lingers over the area. Nevertheless, forecast soundings indicate modestly steep midlevel lapse rates will be present along with modest vertical shear, supporting some risk of strong to severe thunderstorms capable of damaging gusts and perhaps severe hail. ....MN/IA into WI/IL... A surface low is forecast to deepen over the Mid-MO Valley during the afternoon/evening. A warm front will extend east/southeast from the low across northern IA/IL. Thunderstorms are expected to develop in a warm advection regime in the vicinity of the surface warm front. However, it remains uncertain if warm-sector convection will develop, or if convection will mostly be elevated to the cool side of the warm front. Regardless, forecast soundings indicate supercell wind profiles amid a very moist (70s F dewpoints) and unstable airmass. Elevated convection will pose a risk for large hail. If warm midlevel temps/capping can be overcome and storms develop with the warm sector, all severe hazards will be possible, including a couple of tornadoes. Initial cellular convection will likely develop into a more linear, forward-propagating mode during the evening as storms move into southern WI and northern IL. Given uncertainty regarding warm sector development, have maintained probabilities from the previous Day 2 outlook, but upgrades could become necessary if trends toward warm-sector supercell development increase. ....FL/GA/SC... The National Hurricane Center forecast has Hurricane Debbie making landfall along the FL Big Bend vicinity this morning, and becoming centered over southeast GA by Tuesday morning. Within the eastern semicircle of the tropical cyclone across northern FL/southeast GA and coastal SC, low-level SRH will be maximized within an airmass characterized by mid 70s F dewpoints. Tornado potential will accompany any deeper updrafts across this area. ....Northern Rockies... Isolated to scattered thunderstorms are expected to develop during the afternoon/evening as a weak upper shortwave trough impinging on the region brings increasing ascent and midlevel moisture to the region. Steep midlevel lapse rates will support up to around 500 J/kg MLCAPE. Around 25-35 kt effective shear magnitudes will allow for organization of deeper updrafts. Meanwhile, a deeply mixed boundary layer with inverted-v sub-cloud thermodynamic profiles will support strong outflow gusts with this activity. ...Leitman/Thornton.. 08/05/2024 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .