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
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