Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Aug 27 2023 08:22:13 FOUS30 KWBC 270822 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 421 AM EDT Sun Aug 27 2023 Day 1 Valid 12Z Sun Aug 27 2023 - 12Z Mon Aug 28 2023 ....A SLIGHT RISK OF EXCESSIVE RAINFALL IS IN EFFECT ACROSS PORTIONS OF THE SOUTHEAST, LOWER MID ATLANTIC, AND THE TENNESSEE VALLEY... ....Parts of the Southeast into the Lower Mid Atlantic Region... Synoptic setup remains favorable across the Carolinas into southern Virginia down into northeast Georgia. Enhancement of an upper jet over the northern Mid Atlantic and Northeast will provide increasing ascent across the area mentioned above. Anomalously moist environment centered over the Carolinas provides a footprint for enhanced rainfall risks, especially located along a stalled frontal boundary bisecting eastern NC down through central SC and GA. MLCAPE breaching 2500 J/kg will be common across much of the Lower Mid Atlantic and Southeast US providing one of the last key ingredients to the setup. 00z HREF neighborhood probability of greater than 2-3" of rainfall remains fairly robust across much of eastern NC down into northeast SC with local maxima approaching 5+" in spots. Deterministic guidance still doesn't have a perfectly defined area of where the heaviest rain will occur, but the threat is certainly there for somewhere within the coverage area to receive very high amounts of rainfall capable of locally significant flash flooding. The slight was also expanded to the west to include the western NC mountains through the SC Piedmont due to increasing signals for locally heavy rainfall mid-afternoon with 00z HREF probability of 2"/hr rainfall rates now over 25% for portions of the higher terrain. Hi-res deterministic and ensemble guidance has been consistent the past few runs of initiation over the Appalachians leading to the best chance for flooding to occur mid to late afternoon before shifting focus to the eastern half of the state(s). ....Western Tennessee into Southeast Missouri and Southwest Kentucky... A potent mid-level vorticity maxima is analyzed over Missouri this evening with a slow push to the southeast, generating scattered convection across southeast Missouri into northeast Arkansas and southern Illinois. Recent hi-res guidance trends point to a regional maximum in convective coverage and anticipated heavy rainfall rates thanks to ascent within a PW anomaly around 2 standard deviations above normal. 00z HREF probability of greater than 2"/hr of rainfall is focused over northwest Tennessee into southwest Kentucky with 24 hr totals ranging from 3-6" across guidance. The local enhancement is likely in part due to the ascent focused over a surface trough analyzed from northern Mississippi north into Kentucky. With the signal across all hi-resolution deterministic and ensemble mean(s), elected to introduce a slight for the aforementioned area to account for enhanced flash flood concerns beginning this morning, through the afternoon.=20 ....Rockies and High Plains... Scattered convection is anticipated across the Rockies down into the southern high plains of Texas this afternoon incorporated along an axis of elevated theta-e on the eastern flank of a western mid-level ridge. Marginal instability on the order of 500-1000 J/kg with greater instability over west Texas will aid in diurnally driven convection beginning after 18z. NW'ly flow will help propagate convection towards the south and east across the Front Range of CO down through eastern NM and the Caprock of TX. Locally heavy rainfall will allow for a chance of flash flooding, especially within any larger towns or cities where local FFG's are generally lower.=20 Kleebauer Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7t1gTcv_UKPzGSP6LS-kI1X6YTn3eu1l35sukWmCQw9Z= K0otcrckBFhbc9vGURTeVgce1hoTEU4OZFjZwg03u7GofLY$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7t1gTcv_UKPzGSP6LS-kI1X6YTn3eu1l35sukWmCQw9Z= K0otcrckBFhbc9vGURTeVgce1hoTEU4OZFjZwg03s0lCEQM$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7t1gTcv_UKPzGSP6LS-kI1X6YTn3eu1l35sukWmCQw9Z= K0otcrckBFhbc9vGURTeVgce1hoTEU4OZFjZwg03FJeqLL8$=20 $$ =3D =3D =3D 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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .