Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Oct 11 2024 20:24:08 FOUS30 KWBC 112023 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 423 PM EDT Fri Oct 11 2024 Day 1 Valid 16Z Fri Oct 11 2024 - 12Z Sat Oct 12 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Easterly low level flow will bring showery conditions to the central and southeast Atlantic coast of FL from this afternoon into tonight. 12Z soundings showed precipitable water values at or below 1.5 inches that resulted in limited instability. That...combined with a relative lack of organization shown currently on satellite or in the short-range hi-resolution guidance...suggests that rainfall rates or totals are not likely to reach levels of concern for flash flooding. Thus we will continue to carry no risk area in the ERO. Bann Day 2 Valid 12Z Sat Oct 12 2024 - 12Z Sun Oct 13 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE UPPER FLORIDA KEYS INTO THE SOUTHEAST FLORIDA URBAN CORRIDOR... Moisture and instability return northward into southern Florida=20=20 Saturday into Saturday night, with PWs increasing towards 2.25" and CAPE over 1000 j/kg. Meanwhile a weak wave moving into the eastern Gulf of Mexico may result in an uptick in low level flow and=20 convergence. Thus expect we should gradually see an uptick in=20 convective coverage this weekend over the Keys into south FL. The overall synoptic pattern still looks to favor slow moving=20 convective cells along and near the coastal convergence axis give=20 easterly low level flow and westerly upper level winds. Timing=20 remains a bit uncertain. Even though the better convective=20 coverage may end up more over the Keys this period (where flash=20 flooding is harder to come by) the 12Z suite of model guidance=20 still suggests the increasing moisture and instability poses at=20 least a conditional threat of localized flash flooding Saturday=20 into Saturday night into the more urban areas of southeast FL. If=20 deep convection does indeed develop then urban flash flooding is=20 possible from the upper Keys into southeast FL. Bann Day 3 Valid 12Z Sun Oct 13 2024 - 12Z Mon Oct 14 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE UPPER FLORIDA KEYS INTO THE SOUTHEAST FLORIDA URBAN CORRIDOR... The risk on day 3 is a continuation of the threat on day 2 over Southeast Florida. The overall thermodynamic ingredients remain=20 the same, however there is a chance that forcing will be stronger=20 by Sunday. Still some timing and positional differences amongst the guidance, but the general consensus is for a weak wave to move=20 across FL Sunday, which should both result in a subtle uptick in=20 mid/upper forcing and locally enhance lower level convergence. The 12Z suite pf numerical guidance still pointed to a somewhat greater chance of loosely organized convective clusters Sunday=20 into Sunday night...and with wind fields still supporting slow=20 moving cells...the risk of isolated urban flash flooding is still possible but not enough to upgrade beyond a Marginal risk area at this point. Will continue to monitor trends. Chenard Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5hEkMRa5bhPK841B2oZyQV0xlOc1_68fAmFzMaMvl5__= AOwn4s5XPxSzDjPtRROdPu1XHl2RkgwYxYFzFHqbkn5Y1jU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5hEkMRa5bhPK841B2oZyQV0xlOc1_68fAmFzMaMvl5__= AOwn4s5XPxSzDjPtRROdPu1XHl2RkgwYxYFzFHqbNSHZKVk$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5hEkMRa5bhPK841B2oZyQV0xlOc1_68fAmFzMaMvl5__= AOwn4s5XPxSzDjPtRROdPu1XHl2RkgwYxYFzFHqbk1k4AbU$=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) .