Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Feb 13 2024 07:30:42

FOUS30 KWBC 130730
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
229 AM EST Tue Feb 13 2024

Day 1
Valid 12Z Tue Feb 13 2024 - 12Z Wed Feb 14 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.=20=20
=20
Roth


Day 2
Valid 12Z Wed Feb 14 2024 - 12Z Thu Feb 15 2024

....A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF
SOUTHWEST OREGON & NORTHWEST CALIFORNIA...

Portions of coastal OR and northwest CA...=20
As a cyclone in the Pacific swings north a bit astride of the
Pacific Northwest coastline, low-level inflow of up to 50 kts out
of the south to southwest and precipitable water values of 0.75-1"
impact portions of southwest OR as well as west-central and
northwest CA.  With time, small bubbles of 250 J/kg of MU CAPE
(per 00z NAM forecasts) are expected to move near the region.=20
QPF-wise, since this time yesterday, the non-NAM and non-Canadian
Regional guidance has trended upward in amounts.  Given the above,
hourly rain totals of 0.5"+ are more probable, and the 00z HREF
now shows a 40%+ chance of occurring by 15/00z, which would be of
most concern in burn scars.  This led to a new Marginal Risk area
for the region.

Roth


Day 3
Valid 12Z Thu Feb 15 2024 - 12Z Fri Feb 16 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.


Portions of OR & CA...
Precipitable water values are on the decline this period as the
flow across the region switches from onshore to offshore.  The
precipitation forecast from the model guidance, outside the 00z
Canadian Regional in western WA and OR, was nothing to write home
about.  Given the above, the Marginal Risk was removed in this
update.


Lower Rio Grande Valley of Southern TX...
Moist inflow surges into the region from the western Gulf of
Mexico as a warm front moves into the region late Thursday night
into early Friday morning.  Precipitable water values rise into
the 1.75-2" range.  Temperatures at 700 hPa don't seem especially
warm, generally below 3C, which implies minimal, if any, mid-level
capping.  However, instability appears meager, with bubbles of
250+ J/kg of MU CAPE per NAM forecasts, and appears to be
outrunning the boundary/QPF into northern TX which won't aid
precipitation production.  Guidance QPF is modest, with the 00z
GFS and the 00z NAM the most bullish, though their amounts are
under 3".  For the most part, precipitation anomalies as far back
as 90 days are below average in this area.  Given the above,
believe the risk for flash flooding is less than 5 percent.=20
Should the guidance become wetter or the timing speed up somewhat,
a Marginal Risk could be considered on later forecast cycles.

Roth


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!9U56qmIg9B-m716fIXXd_8Hgla4mx6NPHc1QAgEQuk4a=
ul5YRXop5csMTuTijFO5D8KwBmcWXxq7vP2nuMY3W0N-Rlg$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!9U56qmIg9B-m716fIXXd_8Hgla4mx6NPHc1QAgEQuk4a=
ul5YRXop5csMTuTijFO5D8KwBmcWXxq7vP2nuMY3aClSeBw$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!9U56qmIg9B-m716fIXXd_8Hgla4mx6NPHc1QAgEQuk4a=
ul5YRXop5csMTuTijFO5D8KwBmcWXxq7vP2nuMY3D0Bnn04$=20


$$



=3D =3D =3D
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