Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Oct 12 2023 15:16:25 AWUS01 KWNH 121516 FFGMPD FLZ000-GAZ000-122100- Mesoscale Precipitation Discussion 1145 NWS Weather Prediction Center College Park MD 1115 AM EDT Thu Oct 12 2023 Areas affected...Northern Florida Peninsula... Adj. Far SE Georgia... Concerning...Heavy rainfall...Flash flooding possible Valid 121515Z - 122100Z SUMMARY...Potential for a spot or two of low-end inundation flooding remains along/south of stationary front as the system clears the northern FL peninsula this afternoon. Additional 2-3" are possible over areas recently affected by 1-3" in the last day or so. DISCUSSION...15z surface analysis combined with RADAR and GOES-E satellite suite depicts a surface wave in the eastern FL panhandle with a roll cloud extending southward indicating the cold front sweeping eastward fairly quickly. A pre-frontal convergence trof is more effectively acting as the front providing enhanced convergence and new thunderstorm activity across the far NE Gulf toward the intersection of the draped stationary front just south of the GA/FL line. Solid southerly to south-southwesterly flow along/ahead of the convergence trof continues to isentropically ascend in proximity to the stationary front though angle is less than ideal, the ascent slope is steep enough to provide scattered to numerous shallow showers and thunderstorms along the length toward the Atlantic. Highly anomalous moisture and localized sounding show nearly saturated profile with over 2.5" of total PWat through the column. Being mostly moist adiabatic has not provided much instability, especially near the front; CAPE to 1000 J/kg has been increasing but clearing skies has supported warming grounds south of the front increasing SBCAPES to over 3000 J/kg.=20 As such, activity is expected to increase as the effective boundary sweeps through. Deep warm cloud layer should allow for any deeper thunderstorms to be highly efficient, though even shallower showers have been capable of 1-1.5"/hr. As a result there is a mixed signal potential for excessive rainfall with at least a low-end risk for localized flash/rapid inundation flooding, especially in proximity to urban centers over the late morning through the afternoon as the cold front clears.=20 As such, there is a dual risk... near the front, training profile with more dense, but less efficient rainfall rates may total to 2-3" over the next few hours. As the front slowly sags south, the training should remain along/south of I-10 but crossing areas that have been well above normal over the last 7 days but still only seen 1-3" in the last 24hr. Soils may have longer to be overwhelmed, but still the potential for a larger areal coverage of low-end flooding will remain. Further south from Levy/Dixie across Marion to Flagler county, higher rainfall totals over the last 24hrs of 3-5", to isolated 6" have further saturated this area. The potential for the stationary front is sag south enough to train across this area is much less likely than the cold front pressing through before then. However, stronger convergence along the pre-frontal trough MAY trigger a few more isolated but much stronger/deeper updrafts capable of very intense rates (and possible severe wx, see SPC and local NWS Forecast Office for more details). Given the available moisture, updraft strength may result in rates in excess of 2-3"/hr but only for 30-60 minutes. HRRR 15 min rain totals of 1.25-1.5 have been forecast generally in line with this more intense rate. Combined with the higher ground saturation it cannot be fully ruled out that one or two isolated flash flooding incidents remain possible across this axis as well. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4GE5Vnq1GJ8IiTEVTc77-fRSAP7NRR9fdiXqNd3b3rLC_xOM8u7sic-lA0ru9MceCYWX= SO5yGxs5O7tC1i2qbZ1rF_k$ for graphic product... ATTN...WFO...JAX...MLB...TBW... ATTN...RFC...SERFC...NWC... LAT...LON 30898139 30338132 29798118 29208095 28988117=20 28818189 28718259 28978283 29228302 29928284=20 30408311 30828209=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) .