AWUS01 KWNH 111956
FFGMPD
MTZ000-IDZ000-ORZ000-120155-

Mesoscale Precipitation Discussion 0989
NWS Weather Prediction Center College Park MD
355 PM EDT Wed Sep 11 2024

Areas affected...portions of Idaho and western Montana

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

Valid 111955Z - 120155Z

Summary...Scattered thunderstorms continue to expand in coverage
across the Intermountain West.  Atmospheric profiles are
supportive of localized areas of training/repeating and rainfall
totals exceeding 1 inch.  Localized flash flood potential is
expected - especially near low-lying areas and burn scars.

Discussion...Over the past 1-2 hours, convection has deepened
along north-south-oriented axes 1) along the Oregon/Idaho border
region near Boise and 2) along the Idaho/Montana border near
SMN/Salmon, ID.  These corridors of convection happen to be
collocated with moist axes (peak PW values in the 0.7-0.9 inch
range per SPC mesonanalyses) and are forced by ascent associated
with a strong mid-level low centered over western Washington
State.  The storms are also oriented parallel to southerly
mid-level steering flow that - while fostering appreciable storm
motions of 20-30 knots - were enabling localized training of cells
and rain rates in the 0.2 inch/hr range at times.

While rain rates are relatively low currently, models suggest that
the ongoing regime should result in a continued expansion of
convective coverage northward into more of northern Idaho/western
Montana through the afternoon.  This expansion and continued cell
training could result in a few spots of rain rates exceeding 0.5
inch/hr at times. A number of burn scars are noted per the WRH
Hazards Viewer that could enhanced localized runoff and cause
flash flooding.  The flash flood threat should continue to ramp up
through the afternoon hours, and persist beyond 02Z or so.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-OZOrhYC2dRqTDnDl7-iFnSsXki38YLrb00HN7wfV_KcmeN2GWo4pvFhqxmJYaYNXnHN=
_j9aKliNrjm8k7c4VDr2-co$  for graphic product...

ATTN...WFO...BOI...MSO...OTX...PDT...PIH...TFX...

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

LAT...LON   48941481 48781317 47951282 46761255 45591246=20
            44721285 43971401 43781586 44031730 44981705=20
            46441679 48111665 48861604=20

=3D =3D =3D
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