Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Jan 05 2025 08:15:47 FOUS30 KWBC 050815 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 315 AM EST Sun Jan 5 2025 Day 1 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 is taking shape over the central=20 US early this morning, originating from a potent shortwave trough=20 digging through the Central Rockies over the past couple of days.=20 The trough is in the process of cutting off into an upper-low as=20 it emerges from the Rockies into the central Plains. Strong DPVA=20 in association with the trough will interact with the right-=20 entrance region of a broad phased jet structure (~140 kt jet=20 streak @ 250 mb over the Mid-Atlantic, and a smaller ~100 kt jet=20 streak near the Ozarks). A substantial low-level jet (850 mb of=20 40-60 kts) is expected to form as a result of deep cyclogenesis, stretching from the Central Gulf Coast to the Mid-South, ushering=20 in highly anomalous tropospheric moisture (for this time of year)=20 with precipitable water values nearing 1.5" (between the 90th=20 percentile and max moving average, per JAN/BNA/BMX sounding=20 climatology). Most hi-res CAMs continue to suggest localized 1-2"=20 totals in association with combined totals from scattered=20 convection in the open warm sector and the following primary squall line in association with the approaching cold front, though a=20 couple of solutions (FV3 and CMCreg) suggest localized streaks of=20 2-3" totals (from northeast LA through north/central MS into=20 northwest AL). While much of these totals may occur over a=20 relatively short period (with any flash flooding conditions more=20 likely due to storm mode and sub-hourly rates and totals of 1-2"),=20 00z HREF 40-km neighborhood probabilities for 2" exceedance over 3=20 hours barely peak at 20-30%. Therefore the progressiveness of this=20 system (and the limited window of time in the afternoon to take=20 advantage of destabilization, with SB CAPE from east TX and=20 southern LA to the Mid-South reaching 500-2000 J/kg) should largely preclude any organized flash flood threat. Have maintained the=20 inherited Marginal risk area once again, generally encompassing the expected warm sector of the system (while excluding areas farther=20 north where more impressive broad QPF exists, as this precipitation will mostly occur in the form of ice and snow). Churchill Day 2 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 3 Valid 12Z Tue Jan 07 2025 - 12Z Wed Jan 08 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!84RqmUZ4Nwmzv96X718TAEYg5cLfTMRPTa0blmhnBZF4= cgFvoLMnUGGVy-1fpuKCPdYVpSl8X7Ti08mdTNjRU8J1St0$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!84RqmUZ4Nwmzv96X718TAEYg5cLfTMRPTa0blmhnBZF4= cgFvoLMnUGGVy-1fpuKCPdYVpSl8X7Ti08mdTNjRSCPiiCI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!84RqmUZ4Nwmzv96X718TAEYg5cLfTMRPTa0blmhnBZF4= cgFvoLMnUGGVy-1fpuKCPdYVpSl8X7Ti08mdTNjRczFgNG4$=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) .