Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Jun 04 2023 19:30:36

AWUS01 KWNH 041930
FFGMPD
MTZ000-IDZ000-NVZ000-050130-

Mesoscale Precipitation Discussion 0425
NWS Weather Prediction Center College Park MD
329 PM EDT Sun Jun 04 2023

Areas affected...Central ID...Southwest MT...Far Northern NV

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

Valid 041930Z - 050130Z

SUMMARY...Growing field of slow moving thunderstorms containing
downpours may result in flash flooding this afternoon.

DISCUSSION...A 500mb upper low dawdling over northern UT is
prompting upper level divergence over the northern Rockies and
northern Great Basin. At the same time, southeasterly flow in the
500-700mb layer originating out of the central High Plains
delivered PWATs on the order of 0.8-0.9" to the region, which is
around the 90th climatological percentile for the time of year.
Surface based heating has steadily increased SBCAPE to the tune of
500-1,000 J/kg in central ID and as far south as the ID/NV border.
Area averaged soundings from the 18Z HRRR over central ID this
afternoon show low-mid layer RH values near 80% and the available
SBCAPE as a classic skinny CAPE profile. Most notably, cloud layer
mean wind speeds are very light, generally topping out around 5
knots.

With the atmosphere growing increasingly unstable, anomalous
moisture present, and slow storm motions, slow moving
thunderstorms could contain around 1"/hr rainfall rates. Soils are
most sensitive in portions of far northern NV, the Sawtooth and
Bitterroot ranges, and southwest MT where 14-day rainfall totals
have ranged between 300-400% of normal. The 12Z HREF showed a
strong signal for 6-hr QPF > 10-yr ARIs in central ID and northern
NV this afternoon with probabilities as high as 40-60%. Given
hi-res guidance showing some ensemble support for excessive
rainfall rates in areas with sensitive soils, it is possible
thunderstorms this afternoon lead to flash flooding. Along with
the overly saturated soils, creeks and streams as well as roads
along rugged and complex terrain are also susceptible to flash
flooding this afternoon.

Mullinax

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!-hfTL_CYqXtrmQLYmfg97W560e-_kov8IbbgTHTqJ3maQ6MBxhShIHapIOSTYq6R8Gj9=
ZpuCKuhIAf36ZQ73BQFiXG8$  for graphic product...

ATTN...WFO...BOI...LKN...MSO...PIH...TFX...

ATTN...RFC...CBRFC...CNRFC...MBRFC...NWRFC...NWC...

LAT...LON   46781511 46601392 46021324 45301260 44411259=20
            43561328 43001410 42221403 41791437 41551559=20
            41741647 42541697 43281616 43881616 44641680=20
            45221656 45661624=20

=3D =3D =3D
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