Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 28 2025 19:28:29 ACUS03 KWNS 281927 SWODY3 SPC AC 281926 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 PM CDT Mon Jul 28 2025 Valid 301200Z - 311200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN/CENTRAL HIGH PLAINS...ACROSS THE MID-MISSISSIPPI VALLEY...AND OVER PORTIONS OF THE NORTHEAST... ....SUMMARY... Severe thunderstorms are possible in the Mid-Missouri/Mississippi Valley vicinity, parts of the Mid-Atlantic/southern New England, and the northern/central High Plains on Wednesday. ....Synopsis... A belt of enhanced mid/upper westerly flow on the southern periphery of the eastern Canada upper cyclone will overlap portions of the Great Lakes to the Northeast. A surface cold front is forecast to move south/southeast across portions of OK/TX into the Ohio Valley and Northeast on Wednesday. Ahead of the front, a seasonally moist airmass will be in place. The corridor of greatest instability will reside from the Ozarks to the Ohio Valley and into the northern Mid-Atlantic, coincident with stronger boundary layer moisture and stronger heating. The better boundary layer moisture/instability corridor will remain displaced to the south of the stronger mid/upper flow. Nevertheless, a few corridors of strong to severe thunderstorm potential appear possible. ....Lower-MO/Mid-MS Valley vicinity... A decaying MCS from the Day 2/Tuesday period may be located over IA. Associated outflow and any MCV could move across parts of the Mid-MS Valley and become a focus for more organized storm development within the modestly sheared environment. This scenario is uncertain and depends on how convection develops late in the Day 2 period into early Day 3/Wednesday. Any storms that develop will do so within a very moist (70s dewpoints) and strongly unstable airmass. A risk for damaging/severe gusts would accompany this activity. ....Northeast... A moist boundary layer will be in place ahead of the south/southeast moving cold front. Midlevel lapse rates will be weak, limiting stronger destabilization. The corridor of greatest instability will likely remain confined to the northern Mid-Atlantic vicinity with more modest moisture/instability with northward extent into ME. Nevertheless, stronger vertical shear will reside across the region. Vertically veering wind profiles and effective shear values greater than 40 kt suggest supercells may be possible, though shear profiles are forecast to remain weak through 1-2 km. Where strong heating occurs and allows for steep low-level lapse rates, strong/locally damaging gusts may occur. ....Northern/Central High Plains... Easterly low-level flow will maintain modest boundary layer moisture (mid 50s to low 60s dewpoints) across the region beneath steep midlevel lapse rates. This will support development of moderate instability during the afternoon within the upslope flow regime. Initial thunderstorms will develop over higher terrain and generally migrate east. While low-level flow through around 2-3 km will remain very weak, vertically veering wind profiles and rapidly increasing westerlies above 500 mb will support effective shear magnitudes around 25-35 kt, allowing for some storm organization. Isolated hail and gusty winds will be possible with these storms. ....Oregon... A weak upper shortwave trough is forecast to move across OR during the afternoon or evening. Sufficient midlevel moisture will be present amid steep midlevel lapse rates to support isolated thunderstorm development associated with this feature. MLCAPE values to around 500-1000 J/kg over a relatively confined area near the Cascades will be possible. Low to midlevel flow will remain weak, with increasing winds above 3 km, resulting in sufficient effective shear magnitudes for a couple of briefly organized cells. Inverted-v sub-cloud thermodynamic profiles could support sporadic strong gusts. A Marginal risk (level 1 of 5) could be needed at some point in the coming day if confidence increases in storm timing and coverage. ...Leitman.. 07/28/2025 $$ = = = 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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .