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
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