Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 23 2022 01:00:49 FOUS30 KWBC 230100 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 759 PM EST Thu Dec 22 2022 Day 1 Valid 01Z Fri Dec 23 2022 - 12Z Fri Dec 23 2022 ....A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE MID ATLANTIC INTO SOUTHERN NEW YORK AND SOUTHERN NEW ENGLAND... 0100 UTC Update -- Have removed the Marginal Outlook across coastal NC, while paring the southwest portion of the other Marginal Risk area in the Mid Atlantic based on the latest observational and mesoanalysis trends (including satellite and radar). Hourly QPEs have been hard pressed to get over 0.50-0.75" given the absence of instability, therefore the flash flood threat remains isolated or marginal at best, with any rapid runoff owing, at least to some degree, to the frozen soil and/or snow cover. Hurley Day 2 Valid 12Z Fri Dec 23 2022 - 12Z Sat Dec 24 2022 ....A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF NEW ENGLAND... New England... The threat of excessive rainfall should be on-going at the start of the period given strong on-shore flow that draws deep moisture across southern and central New England near/north of a warm front extending southeastward into the western Atlantic. Farther north, p-types across the mountains of Maine are expected to start off as frozen but transition to liquid as strong low level warm air advection moves through the region. Downstream of a deep-layered low approaching from the Midwest, divergence and diffluence aloft should be plentiful across the Northeast U.S. (especially as the upper level trough axis takes on a negative tilt). Rainfall rates are expected to peak around an inch in an hour along with storm totals in the 2-4 inch range but with higher totals focused from the northern half of New Hampshire into the western half of Maine. Only minor adjustments were made to the previously-issued Slight Risk considering that problems could result from rain on the current snow pack and/or frozen ground...or additional melting of snow pack by warmer dewpoints. Urbanized/tidal flooding could be a concern during high tides time and/or in areas with poor or already full drainage routes. In terms of the marginal risk, this cycle extended the area slightly west into upstate New York, and trimmed the southern edge out of the NYC metro/Long Island accounting for latest model trends. Santorelli/Bann Day 3 Valid 12Z Sat Dec 24 2022 - 12Z Sun Dec 25 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE PACIFIC NORTHWEST... The approach of a front from the eastern North Pacific will usher another round of rain into the Pacific Northwest on Saturday. Models point to precipitable water values increasing to over an inch given on-shore flow at 850 mb of 35 kts to 45 kts during the day on Saturday. Rainfall amounts of 2 or 3 inches are shown by the models and deterministic WPC QPF across the Olympic peninsula...and much of that looks to be confined to the first 12- to 18-hours of the period before the area of precipitation pushes inland. Some modestly heavy amounts also extend southward into far northeast Oregon, so the previous shift marginal risk was extended slightly southward to account for that. Santorelli/Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-mkuoFhhuJNrgDVHS3pHJTK-X6gcs0Hl6NoxB50Q2EJE= KoO2wu1-uOjDyAF0jmIuDKSpZo3F9wr2SbcqujxRIrqz-K4$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-mkuoFhhuJNrgDVHS3pHJTK-X6gcs0Hl6NoxB50Q2EJE= KoO2wu1-uOjDyAF0jmIuDKSpZo3F9wr2SbcqujxROjX1z94$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-mkuoFhhuJNrgDVHS3pHJTK-X6gcs0Hl6NoxB50Q2EJE= KoO2wu1-uOjDyAF0jmIuDKSpZo3F9wr2SbcqujxR-6kGhMI$=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) .