Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Jan 04 2025 08:15:42 FOUS30 KWBC 040815 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 315 AM EST Sat Jan 4 2025 Day 1 Valid 12Z Sat Jan 04 2025 - 12Z Sun Jan 05 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Churchill Day 2 Valid 12Z Sun Jan 05 2025 - 12Z Mon Jan 06 2025 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHEAST AND CENTRAL GULF COAST... An impressive deep layer cyclone will develop over the central US=20 into Day 2, originating from a potent shortwave trough currently digging into the Four Corners region. The trough is expected to cut-off into an upper-low as it emerges into the central/southern Plains with strong DPVA interacts with the right-entrance region=20 of a broad phased jet structure (~130 kt jet streak @ 250 mb over=20 the Mid-Atlantic, and a smaller ~100 kt jet streak near the Ozarks). A substantial low-level jet (850 mb of 40-60 kts) is expected to=20 form as a result of deep cyclogenesis, ushering in highly=20 anomalous tropospheric moisture (for this time of year) with=20 precipitable water values nearing 1.5" (near the 90th percentile to max moving average, per JAN/BNA/BMX sounding climatology). While=20 downscaled global guidance (GFS/ECMWF) continues to suggest only=20 localized 1-2" totals, the impressive dynamics of this system=20 (along with the anomalous moisture) suggest the potential for this=20 guidance to locally be exceeded (as the 00z FV3 suggests, but=20 additional CAMs should better capture the even with the upcoming=20 12z runs). That said, both the progressive nature of the system and the limited window of time in the afternoon to take advantage of=20 destabilization (with SB CAPE from east TX and southern LA to the=20 Mid-South reaches 500-2000 J/kg) are expected limit localized=20 totals to the 2-3" range (with as much as 1-2" in an hour with the=20 main line of convection). Have maintained the inherited Marginal=20 risk area for much of the Southeast (with some additional expansion towards the southwest, where instability will be most abundant)=20 generally encompassing the expected warm sector of the system=20 (while excluding areas farther north where more impressive broad=20 QPF exists, as this precipitation will mostly occur in the form of=20 ice and snow). Churchill Day 3 Valid 12Z Mon Jan 06 2025 - 12Z Tue Jan 07 2025 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Churchill Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7nNuCHAENyvNhV1u_YzDLgTWfP1U_TFLG7djL7-cmjmQ= ZkMSfT0hQfVAZdYtjDoAiLY63C-2GEJjX7QmFltd3l8ITBE$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7nNuCHAENyvNhV1u_YzDLgTWfP1U_TFLG7djL7-cmjmQ= ZkMSfT0hQfVAZdYtjDoAiLY63C-2GEJjX7QmFltd9OIFqxA$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7nNuCHAENyvNhV1u_YzDLgTWfP1U_TFLG7djL7-cmjmQ= ZkMSfT0hQfVAZdYtjDoAiLY63C-2GEJjX7QmFltdSSgPNhY$=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) .