Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Nov 22 2023 01:04:15 FOUS30 KWBC 220104 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 759 PM EST Tue Nov 21 2023 Day 1 Valid 01Z Wed Nov 22 2023 - 12Z Wed Nov 22 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF THE SOUTHEAST TO THE MID-ATLANTIC AND FAR SOUTHERN NEW ENGLAND... ....01Z Update... The latest GOES-E IR/WV satellite imagery in conjunction with radar shows a widespread area of moderate to heavy rain impacting many areas of the interior of the Southeast and into the Mid-Atlantic region with an emphasis on the Blue Ridge and Piedmont as a strong deep layer warm conveyor belt and associated atmospheric river of moisture from the subtropics surges up along the Eastern Seaboard out ahead of a deep layer trough advancing east across the OH/TN Valleys. There is an axis of relatively strong convection over parts of the Southeast currently involving GA/SC with some relatively warm-topped QLCS signatures noted, and this is where there is the pooling of stronger warm-sector instability along with greater shear profiles. The low-level jet which is already on the order of 50 to 60 kts out of the south-southwest may actually strengthen a bit more overnight over the Piedmont areas and the I-95 corridor of the Mid-Atlantic region as strong upper-level jet forcing/dynamics ride up just inland of the East Coast. Models solutions including the 18Z HREF and recent runs of the HRRR continue to suggest a wave of low pressure developing along the warm front overnight as the warm sector attempts to get into the I-95 corridor from central/northern VA through central/southern MD and into southeast PA/NJ. This front along with the pooling of at least modest elevated instability and strong low-level convergence/moisture transport should favor a southwest/northeast axis of heavy rainfall along with likelihood of a low-topped convective line that will produce a period of intense rainfall rates that may approach or locally exceed 1"/hour. This will impact the Washington D.C./Baltimore metropolitan areas up through Philadelphia going through 06Z, and may get into the New York City metropolitan area later in the night going through 12Z. Changes to the previous forecast include extending the Marginal Risk area into far southeast NY, Long Island, and adjacent areas of far southern New England, with much of the I-95 corridor from central VA northeastward into far southern New England likely to see 1 to 2 inches of additional rain overnight with locally heavier amounts not out of the question where some brief training of cells occur. Farther south over the Carolinas and GA, the aforementioned convection will advance off to the east gradually with time as a cold front approaches from the west and will be capable of producing some 1 to 2 inch amounts with spotty heavier totals given the presence of greater instability and somewhat heavier rainfall rates. However, for all of the areas of the Mid-Atlantic and Southeast, the antecedent conditions are very dry, and so any excessive rainfall threat will continue to generally be with respect to urban runoff concerns with some low-end flooding possible overnight before the rains begin to taper off early Wednesday morning. Orrison Day 2 Valid 12Z Wed Nov 22 2023 - 12Z Thu Nov 23 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley/Kleebauer Day 3 Valid 12Z Thu Nov 23 2023 - 12Z Fri Nov 24 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Hurley/Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7Ew_fa-du-7VzvlMgpV6yPq4v-7NvEDEKDzbr4FTjDTt= bKDMvZAaGd0AXi4gwHUWqKSc7T99B1pCfZbwcq2hUA_-lMk$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7Ew_fa-du-7VzvlMgpV6yPq4v-7NvEDEKDzbr4FTjDTt= bKDMvZAaGd0AXi4gwHUWqKSc7T99B1pCfZbwcq2hudCx3-c$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7Ew_fa-du-7VzvlMgpV6yPq4v-7NvEDEKDzbr4FTjDTt= bKDMvZAaGd0AXi4gwHUWqKSc7T99B1pCfZbwcq2hIBuWgJk$=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) .