Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 16 2023 18:03:50 AWUS01 KWNH 161803 FFGMPD FLZ000-170000- Mesoscale Precipitation Discussion 0193 NWS Weather Prediction Center College Park MD 203 PM EDT Sun Apr 16 2023 Areas affected...Southeast Florida Concerning...Heavy rainfall...Flash flooding possible Valid 161802Z - 170000Z Summary...Showers and thunderstorms will develop this afternoon and then move slowly across the southern Florida Peninsula. Rainfall rates of more than 2"/hr are likely at times, which could result in areas of 3-5 inches of rain. Flash flooding is possible. Discussion...The GOES-E visible satellite imagery this afternoon shows cumulus bubbling up along multiple boundaries moving into the southern Florida Peninsula. The deepest Cu right now is developing ahead of an outflow boundary which has raced eastward from an MCS over the Gulf of Mexico, and this will continue to sink southeast into the evening. Also evident are slowly building Cu on the westward advancing sea breeze along the Gold and Treasures Coasts. Between these two boundaries, the environment is becoming increasingly favorable for heavy rain producing convection noted by SPC RAP analyzed SBCAPE of 3000-4000 J/kg and PWs of around 1.6 inches, around the 90th-percentile according to the SPC sounding climatology, driven by SW 850mb winds of 15 kts. As the afternoon progresses, the thermodynamic environment will become increasingly supportive to heavy rain. At the same time, ascent through convergence along the surface boundaries and modest PVA as a weak shortwave shifts northeast from the Gulf of Mexico combines with subtle diffluence in the RRQ of a weak poleward arcing upper jet streak over Florida. This should result in scattered showers and thunderstorms, generally focused along the surface boundaries, then expanding in the presence of 30 kts of 0-6km bulk shear and through collisions of the boundaries and convective cells. Mean cloud layer winds (850-300mb) should remain consistently from the SW at 15-20 kts, but as boundaries merge the Corfidi vectors could fall to less than 5 kts, still from the SW, suggesting an increasing potential for slow moving or even backbuilding storms. With the favorable thermodynamics allowing for rain rates in excess of 2"/hr according to HREF probabilities, this will likely result in some areas receiving 3-5" of rainfall by this evening. While there is some uncertainty among the high-res models as to where the heaviest rain axis may develop, HREF probabilities indicate the greatest potential will be across the SE urban corridor where the storms may slow the most due to the sea breeze/outflow collision. Rainfall rates in excess of 2"/hr could yield isolated flash flooding in any urban area. However, the Southeast Peninsula of FL, especially along the coast from Homestead through West Palm Beach, has received more than 600% of normal rainfall in the past week. This is reflected by 40cm soils that are saturated above the 98th-percentile, and is still resulting in standing water in some areas according to WFO MFL. Flash flooding is possible anywhere a slow moving storm can linger, but would be most problematic should a storm impact these excessively saturated areas this afternoon. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_24fquZaImFcsnQ5CjOhpelgVeHnHH0Aek0DG-1LND7U8_6h87ZtnpAjVUPdeOIcZVBA= VEPME8WwF5wTbNExDUzU2jA$ for graphic product... ATTN...WFO...MFL...MLB...TBW... ATTN...RFC...SERFC...NWC... LAT...LON 28778069 28478052 28068044 27658025 27198007=20 26787998 26457998 26038003 25668027 25518038=20 25518062 25598080 25788092 26138097 26598097=20 27078097 27678108 27938128 28238133 28618110=20 28748096=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) .