Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Dec 11 2023 08:11:05 FOUS30 KWBC 110810 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 309 AM EST Mon Dec 11 2023 Day 1 Valid 12Z Mon Dec 11 2023 - 12Z Tue Dec 12 2023 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS DOWNEAST MAINE... Surface low across New England will continue to push northeast while intensifying steadily through its life cycle. A strong LLJ on the eastern flank of the surface reflection will maintain a steady stream of deep layer moisture into portions of ME, especially for locations east of the I-95 corridor from Bangor on north and east. Models have shifted the heaviest rainfall of the period from previous forecasts as the surface low and attendant frontal boundary have translated further eastward over the past succession of model runs. This places the heaviest precip over mainly Downeast ME where some minor snowpack coupled with rainfall over the past 12-18 hours will exacerbate the flooding potential within the confines of the areas mentioned above. The limiting factor in higher risk potential will be the lack of rates due to limited convective development, as well as forward propagation of the precip field as it comes through later this morning, exiting by the afternoon hours. 00z HREF neighborhood probabilities for at least 1"/3-hrs is pretty high (70-90%) encompassing the outlined area. That's pretty much where the potential ends as the 2"/3-hrs probabilities dwindle to a lowly 10%. If the pattern didn't yield appreciable rainfall prior to this period, this would likely be a MRGL, but to maintain some continuity from previous forecast issuance with the pattern still producing heavy rainfall, have kept the SLGT but brought in the bounds of both it and the MRGL risk area to adjust for the latest trends. Flash flooding concerns will remain localized. Kleebauer 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!_sr4CVLRPvdlN8OAFbwb0kY7McrgS8aETttOc3Fa2D3f= DbDVmmJ6Pe2xRsZJthWf-D2ycQBxcczVFeW0ta6x9GAfpCo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_sr4CVLRPvdlN8OAFbwb0kY7McrgS8aETttOc3Fa2D3f= DbDVmmJ6Pe2xRsZJthWf-D2ycQBxcczVFeW0ta6xK52yJqY$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_sr4CVLRPvdlN8OAFbwb0kY7McrgS8aETttOc3Fa2D3f= DbDVmmJ6Pe2xRsZJthWf-D2ycQBxcczVFeW0ta6xNrn7oCU$=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) .