Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Aug 01 2025 01:18:46

AWUS01 KWNH 010115
FFGMPD
MTZ000-IDZ000-ORZ000-WAZ000-010600-

Mesoscale Precipitation Discussion 0838
NWS Weather Prediction Center College Park MD
913 PM EDT Thu Jul 31 2025

Areas affected...Portions of the Pacific Northwest

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

Valid 010112Z - 010600Z

SUMMARY...Numerous showers and thunderstorms across northeastern
Washington, northern Idaho, and far western Montana are producing
local rainfall rates of up to 2 inches per hour. Flash flooding is
possible where storms move over flood-sensitive areas.

DISCUSSION... A northwestward moving upper level disturbance has
moved into a moisture-rich environment in place across the Pacific
Northwest, with PWATs around 1 inch. This is above the 90th
percentile compared to climatology for this time of year. The
combination of the disturbance moving parallel to the terrain of
the highlighted area...favoring upslope flow...as well as the
favorable divergence region impacting that same area has allowed
the storms to consistently grow upscale through the afternoon
hours. Further, a stationary front across Montana is also acting
as a focal point for additional convective development. A lack of
any strong steering flow and the terrain are both favoring the
storms remaining largely stationary as they gradually merge into
clusters. Further, the abundance of burn scars from recent years
in this area will further locally enhance the potential for flash
flooding. SPC Mesoanalysis shows instability values across the
Pacific Northwest to as high as 2,000 J/kg, but with widespread
values over 1,000 J/kg. The storms should have no trouble
persisting well into the evening hours.

HiRes guidance is quite mixed about the storm potential in this
area. This is largely due to many of them not handling the
convection that is widespread across the region well right now.
For those that have at least some semblance of how the convection
has evolved thus-far, such as the HRRR, it suggests the storms
begin to dissipate along the Canadian border, but persist for
several more hours from northeastern Oregon into western Montana.

Wegman

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6gfmR7et1drF9fMUhGO6zU-pt-oi_1MzsyqjtDgKs3sGQklktuQzawZBoETDS4aGyck5=
EJbPNG0yJF5SjBFqyE-DpuY$  for graphic product...

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

ATTN...RFC...KRF...PTR...NWC...

LAT...LON   49021708 49011612 48511526 47981447 48101399=20
            47691320 47061162 46701145 46121216 45801284=20
            45421426 43671548 43641640 44371692 44481754=20
            45241836 46381824 46521756 46951709 47631692=20
            48321729 48941760=20

=3D =3D =3D
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