Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Apr 17 2023 08:24:31 FOUS30 KWBC 170824 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 423 AM EDT Mon Apr 17 2023 Day 1 Valid 12Z Mon Apr 17 2023 - 12Z Tue Apr 18 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF ATLANTIC COASTAL SOUTHEAST FLORIDA AND MUCH OF INTERIOR NEW ENGLAND AND FAR NORTHERN NEW YORK... ....Southeast Florida... Easterly flow will stream onshore thanks to a stationary front draped over South Florida and will generate showers and thunderstorms near the Miami-Ft. Lauderdale area, an area that is very sensitive due to multiple days of excessive rainfall and local flooding. Additional rainfall over this stretch of the coastline could quickly become problematic. A Marginal Risk for excessive rainfall remains in effect for this period. ....Interior New England & Far Northern New York... A wrapped up low over Michigan and its associated cold front will continue its eastward trek through New England during this period. Highly anomalous moisture with PW values exceeding 1", which is about 3 sigma above normal, is being drawn into New England on southeasterly flow off the Atlantic ahead of the advancing front. Convection from yesterday evening persisted overnight and will continue to be fueled by this influx of moisture as the day progresses. The progressive nature of the front may be a limiting factor for high intensity rainfall rates, however the combination of the highly anomalous moisture, low FFGs (as low as 0.75 inches in an hour in some spots), and very strong forcing with a highly energetic negatively tilted trough should be enough to overcome the fast movement of the storms and low instability in isolated instances in the Marginal Risk area. Rain falling over areas of snow, will also increase the snowmelt to the local watersheds in northern New Hampshire up through western and northern Maine. With QPF trending less across portions of far southern New Hampshire and Maine, the southern bounds of the Marginal was trimmed northward. Campbell Day 2 Valid 12Z Tue Apr 18 2023 - 12Z Wed Apr 19 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 3 Valid 12Z Wed Apr 19 2023 - 12Z Thu Apr 20 2023 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE CENTRAL PLAINS TO THE UPPER MISSISSIPPI VALLEY... Return moisture from the Gulf of Mexico will be drawn northward through the central U.S. while a couple of low pressure waves over the Central Plains interact with a slow-moving frontal boundary. Locally heavy rain will be possible, especially from Kansas/Missouri northeastward to Wisconsin/Michigan where areal average QPF will range 1 to 2 inches. Much of this part of the country has lowered FFG due to recent/ongoing snowmelt and rain. There will be an elevated threat for some of the convection to produce locally heavy rainfall over these nearly saturated areas. A Marginal Risk is in effect from eastern Kansas to Wisconsin. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6zibYXlwNLl6YB2oNNrf-UQIJqy3AyBLLavITuzCtugS= t6UnnRmQg0jFOOdTM5w4YcGdaYkulDWRwIsUZC7zWdeaIN0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6zibYXlwNLl6YB2oNNrf-UQIJqy3AyBLLavITuzCtugS= t6UnnRmQg0jFOOdTM5w4YcGdaYkulDWRwIsUZC7zeIcklNk$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6zibYXlwNLl6YB2oNNrf-UQIJqy3AyBLLavITuzCtugS= t6UnnRmQg0jFOOdTM5w4YcGdaYkulDWRwIsUZC7zrLorD88$=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) .