Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 30 2024 20:00:56 ACUS01 KWNS 302000 SWODY1 SPC AC 301959 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Tue Jul 30 2024 Valid 302000Z - 311200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE MID MO VALLEY SOUTHEASTWARD INTO THE MID MS VALLEY... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL DAKOTAS... ....SUMMARY... Severe thunderstorms are expected this afternoon through tonight across a broad area from eastern Nebraska and Iowa into parts of the Midwest, Tennessee Valley and southern Appalachians, with multiple swaths of damaging winds likely within this corridor. Severe thunderstorms are also possible across parts of the northern Plains. ....20Z Update... ....TN Valley into the southern Appalachians... Organized convective line continues to progress southeastward across central KY, with more disorganized, multicellular convection downstream across middle and eastern TN. The convective line will likely continue southeastward for at least the next several hours. Ample low-level moisture and buoyancy exists downstream, but deep-layer vertical shear decreases with southern extent as well. This weakening shear may result in a trend towards a more disorganized character, with the outflow eventually outpacing the deep updrafts. However, this may not occur until later this evening, with damaging gusts possible along the line until this weakening occurs. ....Mid MS Valley this afternoon and evening... As mentioned in recently issued MCD #1746, some re-intensification on the southern flank of the decaying convective cluster has been noted across west-central IL over the past 30 minutes or so. Additional convection has developed near the intersection of outflow boundaries across northern MO. Ample low-level moisture exists downstream across east-central MO into southern IL with dewpoints in the mid/upper 70s F. Strong buoyancy exists in this area as well, with recent mesoanalysis estimating MLCAPE over 3000 J/kg. This suggests the developing storms across central MO could intensify, with additional new development likely across central and southern MO. There is also some chance that additional development occurs along the outflow extending from central MO into west-central IL. All of these scenarios suggest that the threat for severe thunderstorms continues across the region, with damaging gusts as the primary risk. Some isolated large hail is also possible with the initial, more cellular storms. ....Central Plains/Mid MO Valley into the Mid MS Valley overnight and early Wednesday... Evening thunderstorm development still appears probable from central NE into the Mid MO Valley as a subtle, low-amplitude shortwave trough interacts with the very moist, unstable, and uncapped airmass over the region. Large to very large hail is possible with the initial development, with a trend towards an organized line thereafter. Given the continued severe potential, no changes are needed to the severe probabilities over the region. ....Northern/Central Plains... Thunderstorm development is anticipated in the next 1-2 hours across the western Dakotas. Storms are expected to intensify as they migrate east into central North and South Dakota. High cloud bases and steep low-level lapse rates will support strong downbursts. ...Mosier.. 07/30/2024 ..PREV DISCUSSION... /ISSUED 1130 AM CDT Tue Jul 30 2024/ ....Mid Missouri Valley into the Midwest/Ohio Valley/Southeast... A larger than usual amount of uncertainty remains regarding convective evolution this afternoon though tonight. Ongoing cluster in southern IA will move southeastward across the mid MS Valley into a rapidly destabilizing airmass with enhanced northwesterly winds at mid/upper-levels supporting sufficient deep-layer shear for continued updraft organization. A swath of severe/damaging winds appears likely with this cluster given the favorable parameter space. Therefore, the Enhanced Risk for damaging winds has been extended southeastward to account for the forecast evolution of this MCS. Another ongoing cluster over the lower OH Valley should also pose some threat for severe/damaging winds as it and associated outflow on its southwest flank spreads east-southeastward across KY and perhaps parts of TN the rest of this afternoon/evening. Additional robust thunderstorm development appears possible through the period in a broad corridor from central/eastern NE through the lower OH Valley and Southeast, with swaths of damaging winds likely the main threat. Details on where/when this activity will develop remain rather uncertain. But, isolated supercells may develop across central/eastern NE late this afternoon/evening in the vicinity of a surface low/lee trough. Very large hail may occur with this convection, with a greater threat for severe/damaging winds possible if this activity can grow upscale into another cluster and spread southeastward across the mid MO and mid MS Valleys this evening/overnight. ....Northern Plains... Weak mid-level height falls amid moderate to strong instability should foster to widely scattered thunderstorm development along a surface trough/dryline across parts of the Dakotas this afternoon. Moderate mid-level westerlies should support deep-layer shear around 30-35 kt, sufficient for a few organized storms, including a few supercells, capable of both large hail and damaging gusts this afternoon and evening. ....Mid-Atlantic Vicinity... A weak mid/upper-level trough and will move across the Mid-Atlantic and vicinity through this evening. Scattered thunderstorm development should continue this afternoon from VA into parts of PA. While there is some uncertainty regarding the extent of heating and destabilization due to lingering cloudiness, a couple of stronger cells/clusters may become capable of producing isolated damaging winds. ....Northeast... Weak to locally moderate instability may develop this afternoon from parts of northern New York into northern New England. While storm coverage remains uncertain, deep-layer shear and relatively cool temperatures aloft could support a couple of modestly organized thunderstorms capable of locally damaging winds, and possibly some hail. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. 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