Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Dec 17 2024 22:51:19 AWUS01 KWNH 172250 FFGMPD FLZ000-180400- Mesoscale Precipitation Discussion 1178 NWS Weather Prediction Center College Park MD 550 PM EST Tue Dec 17 2024 Areas affected...east coast of FL Concerning...Heavy rainfall...Flash flooding possible Valid 172248Z - 180400Z SUMMARY...Localized flash/urban flooding will be possible along the eastern FL Peninsula over the next few hours. Slow cell movement and/or training will be capable of 1 to 3 in/hr rainfall rates which may generate isolated excess runoff within the urban corridor. DISCUSSION...Radar imagery from KMLB and infrared satellite imagery through 2230Z showed scattered thunderstorms occurring along the east coast of FL between Cape Canaveral and Port Saint Lucie, streaming in from the east following the mean low to mid-level easterly flow between 10-20 kt. Surface dewpoints in the lower 70s have contributed to anomalous mid-December moisture with precipitable water values between 1.5 and 1.8 inches (90th percentile) with 1500-2000 J/kg MLCAPE observed on the 22Z SPC mesoanalysis. Cells were located just north of a weak mid-upper level vorticity max observed on water vapor imagery over south-central FL, along a persistent west-east convergence axis seen in fading visible imagery offshore of the east coast. Mean easterly winds in the low to mid-levels have supported repeating cells with short-term training, with observed rainfall rates of 1-2 in/hr near Vero Beach. While recent cloud top cooling on satellite imagery has appeared to migrate generally just offshore, redevelopment and westward translation of heavy rain looks to continue a short-term urban/flash flood threat from southern Brevard County into St. Lucie County along the coast where an additional 2-4 inches will be possible on a highly localized basis through ~01Z. Indications are that these cells will weaken after 00Z as boundary layer stabilization occurs with nocturnal cooling, with cells shifting more offshore or perhaps dissipating. While the HRRR hasn't been doing well with the ongoing placement of cells, there are indications in recent HRRR guidance that the activity could refocus a bit farther south sometime in the 00-03Z time frame. Similar potential for slow movement and/or training will exist is development does get going farther south later tonight. Any areas of flash flooding are expected to remain localized with potential for a quick 2-4 inches over the next few hours. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5Q_aGikNvzafCzBZkLacufk8V7gRB8rgpd-NiBBSPYDk2FeZhieib_YkAuz--L98hVCe= yJGOyht5Bs8lDtVQwfvAzcU$ for graphic product... ATTN...WFO...MFL...MLB... ATTN...RFC...SERFC...NWC... LAT...LON 28308046 27768008 26657985 26118002 26178029=20 26258043 26628045 27058049 27558065 28018077=20 =20=20=20=20=20=20=20=20=20=20=20=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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .