Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Dec 24 2022 15:16:51

AWUS01 KWNH 241516
FFGMPD
ORZ000-WAZ000-242200-

Mesoscale Precipitation Discussion 1169
NWS Weather Prediction Center College Park MD
1016 AM EST Sat Dec 24 2022

Areas affected...western Washington State

Concerning...Heavy rainfall...Flash flooding possible

Valid 241514Z - 242200Z

Summary...Rain rates should increase over the next 2-4 hours
across the Olympic Peninsula and adjacent areas of southwestern
Washington, leading to localized excessive runoff urban/low-lying
flood potential.

Discussion...Radar and satellite imagery indicate a fairly robust
axis of precipitation over northeastern Pacific waters that should
make landfall along the western Washington coastline over the next
1-2 hours.  The axis of precipitation actually has embedded, more
robust convective elements (evidenced by recent lightning strikes
offshore) and is coincident with a marked increase in Integrated
Water Vapor Transport values (appraoching or exceeding 1000 kg/ms)
depicted by operational forecast guidance.  MRMS-estimated
rainfall rates are already in the 0.2-0.5 inch/hr range just north
of Aberdeen, WA, and as precipitation spreads inland, rates
approaching 0.75 inch/hr cannot be ruled out especially in
terrain-favored areas.

Areas of heavier rainfall should begin in earnest around 16Z or so
and persist through around 21Z or so.  Thereafter, models suggest
weakening IVT values as an approaching cold front makes it to the
coast.  The heavier rainfall should promote urban and low-lying
areal flood/flash flood potential, which could also be exacerbated
by ongoing snow melt due to increasing surface temperatures.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7S-p7A54Q_rj_zle9wZb6xO02kNhX22idbOXMpMJs9ZBXaJh4rwwGcwAevtxf0IcRHIX=
jrX3d_HQd4URWH3jR60rrWY$  for graphic product...

ATTN...WFO...PQR...SEW...

ATTN...RFC...NWRFC...NWC...

LAT...LON   48402206 48042166 47382168 46392200 45812249=20
            45892301 46132390 46352408 46682410 47442435=20
            48142478 48362461 48262334 48252268=20

=3D =3D =3D
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