Subj : DAY1SVR: Day 1 Convective Outlook Amend 1 To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 22 2024 22:04:43 ACUS01 KWNS 222204 SWODY1 SPC AC 222202 Day 1 Convective Outlook AMEND 1 NWS Storm Prediction Center Norman OK 0502 PM CDT Mon Jul 22 2024 Valid 222155Z - 231200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NORTH DAKOTA AND NORTHWEST MINNESOTA...THE DESERT SOUTHWEST...AND THE MID-ATLANTIC/EASTERN NORTH CAROLINA... AMENDED FOR ADDITION OF HAIL/WIND PROBABILITIES IN NORTH DAKOTA AND NORTHWEST MINNESOTA ....SUMMARY... Isolated severe thunderstorms remain possible this afternoon and early evening over portions of North Dakota and northwest Minnesota, the mid-Atlantic region, as well as western Arizona to the lower Colorado River Valley. ....North Dakota/Northwest Minnesota... Isolated strong to severe thunderstorms are ongoing along a weak boundary/low-level confluence axis across parts of northeast ND and northwest MN. A few instances of large hail have already occurred. The presence of moderate to locally strong instability, along with marginally favorable deep-layer shear with modestly strengthening northwesterly winds at mid/upper levels, should support a continued threat for isolated severe hail and strong to damaging winds as this activity spreads slowly southward across ND and northwest MN late this afternoon and early evening. 5% severe hail/wind probabilities have been included with this amendment to account for this potential. See Mesoscale Discussion 1695 for additional details on the short-term severe threat across this region. ....Previous Discussions... ....20Z Discussion... Aside from minor line adjustments to affect recent/local trends, no appreciable changes appear to be needed, with respect to the ongoing forecast. Prior reasoning continues to reflect expectations regarding convective/severe risk through the end of the period. ....1630Z Discussion... ....Mid-Atlantic states... A narrow ribbon of slightly enhanced southwesterly 500-mb flow will remain across NC/Delmarva to the southeast of a broad/weak mid-level trough centered over the Great Lakes southwestward through the Ozarks. Although large-scale forcing will be modest, a seasonably moist airmass (14-16 g/kg lowest 100-mb mean mixing ratios per 12 UTC area raobs) will gradually destabilize through the mid afternoon. Midday visible satellite imagery shows the initial stages of a building cumulus field across the Carolinas northward into eastern VA. Widely scattered to scattered thunderstorms are forecast to develop this afternoon within the moderately unstable airmass. Some strengthening in south-southwesterly 850-mb flow is progged by models later this afternoon into the early evening. A few of the stronger storms may pose a localized risk for damaging gusts (45-60 mph). If a transient supercell can develop (primarily 21-01z), a brief tornado is possible. This activity will likely diminish by mid-late evening owing to nocturnal stabilization. ....Western AZ/lower CO River Valley... Widely scattered thunderstorms are forecast to develop later this afternoon/evening as surface temperatures soar into the 100s. Although flow will be weak due to proximity to the mid- to upper-level ridge, large surface temperature-dewpoint depressions (around 50 deg F) will favor evaporative cooled downdrafts with the more robust thunderstorm cores. A few severe gusts (60-70 mph) are possible before this activity wanes by mid evening. ....Southeast New England... Model guidance indicates increased shower/thunderstorm potential late tonight (08-12 UTC) as a strengthening LLJ shifts northeastward from the Mid-Atlantic coast to near the continental shelf/deep Atlantic waters off the southeast New England coast. The latest models generally indicate meager to no surface-based buoyancy penetrating the coast, thus precluding low-severe probabilities this outlook update. ...Gleason.. 07/22/2024 $$ = = = 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) .