####018002813#### AWUS01 KWNH 151842 FFGMPD FLZ000-160000- Mesoscale Precipitation Discussion 0063 NWS Weather Prediction Center College Park MD 240 PM EDT Sun Mar 15 2026 Areas affected...South FL Concerning...Heavy rainfall...Flash flooding possible Valid 151840Z - 160000Z SUMMARY...Slow-moving clusters of showers and thunderstorms with extreme rainfall rates may cause flash flooding going through early this evening. This could include some urban impacts. DISCUSSION...The latest GOES-E IR satellite imagery along with radar shows slow-moving clusters of very heavy showers and thunderstorms impacting portions of Miami-Dade and Collier Counties. This convection is focusing within a moist and unstable environment characterized by MLCAPE values of 1500 to 2500 J/kg and PWs of 1.5 to 1.7 inches. Some modest shear is in place with as much as 20 to 30 kts of effective bulk shear. Much of the activity recently though is tending to get its focus along the presence of multiple mesoscale boundaries including outflow and sea-breeze boundaries where there is small-scale convergence working with the favorable thermodynamic environment. Some modestly divergent flow aloft is noted also given proximity of a weak shortwave west of the FL Straits and Cuba. This modest deep layer ascent coupled with colliding surface boundaries should tend to keep the convective threat maintained going into the evening hours before sufficient levels of instability exhaustion occurs to promote a weakening trend of the convection. Already parts of the FL Everglades in Miami-Dade County have seen over 5 inches of rain, with much of the activity staying away from the urban areas. However, over the next few hours there will still be a threat locally for some of these stronger thunderstorms and heavier rainfall rates to impact the more populated areas of southern FL which in this case will extend to the the southwest coast including areas from Ft. Myers down through Naples. The southeast coast of FL meanwhile from Miami down to Homestead will still need to closely watch some of these slow-moving cells. Rainfall rates of 2 to 4 inches/hour and storm totals locally exceeding 5 inches are expected where any cells become anchored. Earlier runs of the HRRR and RRFS were suggesting this near parts of southwest FL in particular. As such, some areas of flash flooding will be possible given the very high rainfall rates and totals which may include some urban impacts. Orrison ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...KEY...MFL...TBW... ATTN...RFC...ALR...NWC... LAT...LON 27018174 26468098 26118014 25657992 25178031 25298104 26088186 26738218 ####018000671#### PENA01 KWNH 151200 @UHPISF000CN MPDSUM@V2.0@0101700060@12150326@@0NMCGPHMPD:p@!' `' ` @ & B7)p&PNAM02@@ ,}~~~}}|{z{@@,@@,@@L0063 @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 03/15/2026 1841Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @####018000671#### PENA01 KWNH 151200 @UHPISF000CN MPDSUM@V2.0@0101700060@12150326@@0NMCGPHMPD:p@!' `' ` @ & B7)p&PNAM02@@ ,}~~~}}|{z{@@,@@,@@L0063 @@d&MESOSCALE DISCUSSION SUMMARY GRAPHIC @@d& OF ALL VALID MESOSCALE DISCUSSIONS AT @@d& TIME OF PRODUCT CREATION:@@d& ISSUED 03/15/2026 1845Z @@ dNOAA/NWS/NCEP@@d WEATHER PREDICTION CENTER @@d FOR COLOR VERSION SEE: @@d WWW.WPC.NCEP.NOAA.GOV @