Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 04 2025 12:01:06 AWUS01 KWNH 041201 FFGMPD FLZ000-041800- Mesoscale Precipitation Discussion 0359 NWS Weather Prediction Center College Park MD 800 AM EDT Wed Jun 04 2025 Areas affected...southwestern FL Concerning...Heavy rainfall...Flash flooding possible Valid 041200Z - 041800Z Summary...Showers and thunderstorms are increasing in coverage and intensity offshore, and should start moving ashore shortly.=20 Hourly rain amounts to 3" with local amounts to 5" are possible, which would be problematic in urban areas. Discussion...An upper level low is noted in water vapor imagery in the northeast Gulf, south of Apalachicola. An area of scattered thunderstorms have formed offshore southwest FL which is slowly broadening and intensifying, while an outflow from overnight convection is approaching the convection's southeastern flank. As of this discussion's sending, hourly rain estimates are in the 0.5-1" range to the northwest of Captiva. The synoptic surface wind field is light out to the east to southeast, while flow at 850 hPa is south to southwest at 20-25 kts per VAD wind profiles and RAP forecasts, bringing effective bulk shear to 25 kts.=20 Precipitable water values are around 2". ML CAPE values have been slowly rising along the immediate coast per SPC mesoanalyses, where skies are mostly clear as of this discussion's sending. For the moment, CIN is present inland. Offshore ML CAPE values are 1000-1500 J/kg. Some additional increase in instability is expected before the showers and thunderstorms move inland. Should the convection continue increasing in coverage, which is implied by a modest increase in the Galvez-Davison index to 30 in the 15-18z time frame and recent radar trends, this would force the instability gradient to remain rather coastal. Given the effective bulk shear, some level of convective organization is anticipated, which should help with increasing hourly rain amounts if convection gets anchored to a coastal instability gradient, short periods of cell training, or cell collisions/mergers occur. The mesoscale guidance has isolated to widely scattered signals for 3-5" totals between Sarasota and Naples. Given the ingredients present, hourly rain amounts to 3" with local totals to 5" are possible, which would be most problematic in urban areas. Roth ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6DINYzn1E7d2wePx8FxKTNkWYNzrdSHt4yIEfi96RSP9R_Cu5DWebzj9vbSO_6kh70_2= _2U72Y7eygf1e3oz7HegB_o$ for graphic product... ATTN...WFO...MFL...TBW... ATTN...RFC...ALR...NWC... LAT...LON 28028238 27048159 26028146 25848180 26258210=20 27838286=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) .