Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Nov 21 2022 00:56:36 FOUS30 KWBC 210056 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 755 PM EST Sun Nov 20 2022 Day 1 Valid 01Z Mon Nov 21 2022 - 12Z Mon Nov 21 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG A PORTION OF THE URBAN CORRIDOR IN SOUTH FLORIDA... 0100 UTC Update -- Isolated flash flood threat continues along the southern Gold Coast, south of Pompano Beach, near the stationary front draped over the Keys where the onshore/northeasterly low-level flow continues to maintain cell training early this evening. Thermodynamic environment remains favorable -- with PWs near 2" and MUCAPEs ~500 J/kg -- however as the evening progresses there is a decided southward progression of both, along with the heavier rainfall rates (hourly rates of 1.5-2.0"). Marginal Risk will continue for a few more hours, with the threat of flash flooding shifting south of Miami as per the thermodynamic trends and latest (18Z) HREF exceedance probabilities. For further details, please refer to the latest mesoscale precipitation discussion or MPD #1127. Hurley Day 2 Valid 12Z Mon Nov 21 2022 - 12Z Tue Nov 22 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG THE CENTRAL FLORIDA ATLANTIC COAST... 21Z update... The latest guidance has continued with the northward shift up the eastern coastline of Florida although still favors the higher QPF to be in the vicinity of Melbourne with areal averages of 1 to 3 inches. The Marginal Risk was further trimmed from the south to reflect the latest WPC QPF and model trends. Campbell There has been a shift in the numerical guidance to focus the better QPF a bit northward of the previous runs. As a result, trimmed some of the southern-most extent of the on-going Marginal Risk area as yesterday's Day 3 ERO moves into today's Day 2 ERO.=20 The overall pattern still shows an area of precipitable water values approaching 2 inches making their way northward from the Florida Strait on Monday morning that progresses northward during the late morning and afternoon so convection capable of producing some localized downpours remains a possibility. The expectation is that convection that develops across the southern portion of the Marginal Risk area will be more driven by instability while the support of upper level jet will start to aid the deep layer lift farther north. Either way.....there could be sufficiently high rainfall rates to be problematic in the urban areas. Bann Day 3 Valid 12Z Tue Nov 22 2022 - 12Z Wed Nov 23 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL EXTENDING NORTHWARD FROM THE CENTRAL FLORIDA PENINSULA INTO COASTAL GEORGIA ALONG THE I-95 CORRIDOR... 21Z update... The latest WPC forecast has the QPF mostly offshore but also focused over Brevard and Volusia Counties along the eastern coastline while the previous forecast and model guidance covered more of the coastline from Melbourne northward to McIntosh County, Georgia. With this shift the Marginal Risk area was trimmed out of Georgia and extended further south in to Brevard County Florida. The Melbourne metro area looks to have the best potential for the highest QPF for this period. Campbell The potential for locally heavy to excessive rainfall will spread northward from portions of the central Florida peninsula into northeast Florida and a small portion of Georgia along the I-95 corridor on Tuesday. The models still show deep moisture moving northward...in part due to the approach of a southern stream shortwave. Even though the shortwave will be weakening and becoming absorbed by broad-scale synoptic trough, it puts a divergence maximum at jet level over parts of southern Georgia.=20 Between that and onshore flow of an airmass with precipitable water values in the 1.75 inches and 2 inches...some convection that makes its way inland could produce 1 to 3 inches of rain in an hour or two. That is generally within the 1- and 3-hourly flash flood guidance...although impervious surfaces in urbanized areas could result in flooding due to run off or flooding in regions of poor drainage. Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!6TGIbfVuJHCMj0ZyGkrBhMBIh0AtTyKwfXd7BN_lYmcT= nCWFv37hPf8opRV98r7GthnD19UGXIxSUpNC-rVNlPpA2xk$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!6TGIbfVuJHCMj0ZyGkrBhMBIh0AtTyKwfXd7BN_lYmcT= nCWFv37hPf8opRV98r7GthnD19UGXIxSUpNC-rVNf_DP3GE$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!6TGIbfVuJHCMj0ZyGkrBhMBIh0AtTyKwfXd7BN_lYmcT= nCWFv37hPf8opRV98r7GthnD19UGXIxSUpNC-rVN0Ifxl9A$=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) .