Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Sep 03 2023 17:44:22

AWUS01 KWNH 031744
FFGMPD
MTZ000-WYZ000-UTZ000-IDZ000-032300-

Mesoscale Precipitation Discussion 1031
NWS Weather Prediction Center College Park MD
143 PM EDT Sun Sep 03 2023

Areas affected...Eastern ID...Northern UT...Western WY...Adj. MT

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

Valid 031745Z - 032300Z

SUMMARY...Possible localized flash flooding given multiple rounds
of intense but short-duration thunderstorms.  Spots of 1-1.5"
totals particularly near a SW to NE confluence axis, pose
localized flash flooding risk.=20

DISCUSSION...GOES-E Visible imagery is starting to depict a few
pockets of unstable air starting to convect across portions of E
ID where upslope/moisture flux convergence is maximized.  Fairly
clear skies across the area of concern will support solid
insolation and further increase instability over the coming hours.
 CIRA LPW denotes above normal moisture has increased across N UT
into E ID along 15-20kts of southerly flow in the 850-500 layer
with total values nearing 1.25" across the lowest elevations where
sfc Tds are in the 60s.  Modest lapse rates will allow for
instability to rise from the 500-1000 J/kg toward 1500-2000 J/kg
(highest over N UT).  As such, thunderstorms should have solid
moisture flux to support efficient rainfall production for quick
bursts of .5-1" in sub-hourly totals (as suggested by 15min HRRR
rainfall totals).=20=20

Approach of the upper-level cyclonic jet streak across NV becomes
short-wave ridging across the area resulting in high diffluence
and therefore strong divergence aloft across E ID, slowly sliding
across into W WY.  This is aiding the 15-20kts of low-level flow,
while also veering in response increaseing for boundary layer to
700mb deep layer convergence across SE ID into Yellowstone NP.=20
GOES Visible denotes this in the cloud pattern which also
intersects with an effective pre-frontal boundary from central to
northeast NV.  This veering increases with height and should
support some potential for multiple bands of convection to repeat
through the area of concern.  As such, .5" totals through one to
three bands...suggest spots of 1-2" totals locally.  As such,
localized incidents of flash flooding are possible this afternoon.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8zwwW-PcHjGgVtstfLCi3saN6MSMf7zr5nTpreFQDvBbonCaNL8-rav7t558tVmIWAiI=
VRI4koWWhX8l4a3M5bzoDPk$  for graphic product...

ATTN...WFO...BOI...PIH...RIW...SLC...TFX...

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

LAT...LON   44941094 44431025 42900992 41421068 40441228=20
            40121385 41911392 42191422 42661447 43231435=20
            43841341 44171279 44811195=20

=3D =3D =3D
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