Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 11 2023 15:56:40 FOUS30 KWBC 111556 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 1055 AM EST Mon Dec 11 2023 Day 1 Valid 16Z Mon Dec 11 2023 - 12Z Tue Dec 12 2023 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS DOWNEAST MAINE... There is a lingering slight risk of excessive rainfall over portions of eastern Maine into the afternoon before the rainfall associated with deepening low pressure finally moves out of the area. At this point...the concern is more on the amount of rainfall in addition to what has already fallen rather than high rainfall rates. The 11/12Z run of the HREF no longer showed a probability of rainfall exceeding 1 inch per 3 hours...but the prolonged light to moderate rainfall could still yield 1 to 2 inches through early- to mid-afternoon. WPC Mesoscale Precipitation Discussion 1199 is in effect through 19Z. Bann Day 2 Valid 12Z Tue Dec 12 2023 - 12Z Wed Dec 13 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Kleebauer Day 3 Valid 12Z Wed Dec 13 2023 - 12Z Thu Dec 14 2023 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF SOUTHEAST FLORIDA... A weak mid-level impulse is forecast to pivot out of the western Caribbean with associated energy anticipated to work over the FL Straits into the southern FL Peninsula by Wednesday afternoon and evening. A persistent easterly fetch off the Atlantic will provide a guide to an anomalous moisture flux that will accompany the mid-level disturbance allowing area PWATs to soar upwards of 2-2.1", a good 2.5-3 standard deviations above normal for the time frame. Frictional convergence pattern within the confines of the southeast FL coast between West Palm Beach down to Miami will aid in a persistent convective risk as modest instability presence and ample mid-level forcing will generate a period of thunderstorms along and near the coast. This area is notorious for its lower FFG exceedance markers due to the urbanization extending between Miami up through Fort Lauderdale and West Palm. Already beginning to see some trends in global models depicting a maximum oriented along the I-95 corridor between the aforementioned areas with rates likely reaching within the 1-2"/hr variety, at least, given the forecast bufr soundings out of KMIA showing a tall, skinny CAPE environment textbook for heavy rainfall. There's potential for this to upgrade further to a SLGT in future updates, but will refrain in-case there is a shift in where the convective potential is forecast. For the time-being, this is a good setup for locally heavy rain and flash flood concerns. Kleebauer Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-sycI1mdFwsaBP6OfiPRUHftbhU2TUckP9DDN-DCClC2= ocm6bDgSyB22_dRkTG0acJH-bO1sVSA7InshDyVxcO3HfYU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-sycI1mdFwsaBP6OfiPRUHftbhU2TUckP9DDN-DCClC2= ocm6bDgSyB22_dRkTG0acJH-bO1sVSA7InshDyVxKLQacR4$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-sycI1mdFwsaBP6OfiPRUHftbhU2TUckP9DDN-DCClC2= ocm6bDgSyB22_dRkTG0acJH-bO1sVSA7InshDyVx6rYos1w$=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) .