Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jan 17 2025 06:36:21 FOUS30 KWBC 170635 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 135 AM EST Fri Jan 17 2025 Day 1 Valid 12Z Fri Jan 17 2025 - 12Z Sat Jan 18 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. The latest CAM guidance suite has some signals for heavy rainfall in the vicinity of the Florida Keys along a quasi-stationary frontal boundary during the day Friday, and the model consensus is for most of this convection to remain over the Florida Straits and the western Bahamas. Although some of these cells may affect coastal areas of South Florida, the coverage and rainfall rates are low enough to preclude any risk areas at this time. Hamrick Day 2 Valid 12Z Sat Jan 18 2025 - 12Z Sun Jan 19 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Chenard Day 3 Valid 12Z Sun Jan 19 2025 - 12Z Mon Jan 20 2025 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS FAR SOUTHERN GEORGIA INTO NORTH FLORIDA... 1930z Update: Forecast still looks on track. Not seeing anything in the 12z guidance to suggest any changes are needed to the inherited Marginal risk at this time. Chenard ....Previous Discussion... PW values expected to rise to 2 to 2.5 standard deviations above the mean Saturday into early Sunday along and ahead of the arctic frontal boundary pushing across the northeast Gulf into the Southeast and North Florida. The axis of strong low level west south westerly flow along and ahead of the arctic front will slow for a period late Saturday into early Sunday as mid level height falls dive into the base of the broad vortex across eastern North America. This will support potential for training of precip areas along and just to the south of the arctic front across far southern Georgia into North Florida. The non NCEP models...EC..CMC...CMC GEM and UKMET...are showing a more organized axis of heavy rainfall potential than the GFS and NAM. WPC qpf is leaning more toward the non-NCEP guidance given the anomalous PW values and potential for a period of training. The expected axis of heavy rains is forecast across regions that have seen increases in relative soil moisture over the past week from recent heavy rains that have stretched from the central Gulf Coast into the FL Panhandle and North Florida. Still, FFG values remain high, with the forecast additional rainfall amounts of 1-2" likely only resulting in isolated runoff issues. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!57SZna1d5qkF_PWNc2WNsI3p7M9UBM_nDcedLm0ja9dW= atKbyaYvPtikqsVkD2B7GuKMhtMLQonTpbP3pQ0-qxPJZ6c$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!57SZna1d5qkF_PWNc2WNsI3p7M9UBM_nDcedLm0ja9dW= atKbyaYvPtikqsVkD2B7GuKMhtMLQonTpbP3pQ0-bxibYiU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!57SZna1d5qkF_PWNc2WNsI3p7M9UBM_nDcedLm0ja9dW= atKbyaYvPtikqsVkD2B7GuKMhtMLQonTpbP3pQ0-6dC7ruA$=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) .