Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Aug 03 2023 18:27:08

AWUS01 KWNH 031827
FFGMPD
SDZ000-NDZ000-MTZ000-040000-

Mesoscale Precipitation Discussion 0849
NWS Weather Prediction Center College Park MD
226 PM EDT Thu Aug 03 2023

Areas affected...Eastern MT...Southwest ND...Northwest SD...

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

Valid 031825Z - 040000Z

SUMMARY...Very slow moving or stationary thunderstorms with solid
moisture flux convergence pose widely scattered intense rainfall
and totals over 3"+ possible.

DISCUSSION...GOES-E 10.3um EIR loop depict a few stronger
thunderstorms breaking through the cirrus canopy along the
northeastern side of the large scale cyclone dominating the
northern Intermountain West centered over SW WY.  A secondary
700-500mb vorticity center is placed across E MT, along the
interface of the deeper layer warm conveyor belt where moisture is
surging north-northwestward.   RAP analysis denotes strong
moisture flux convergence along/under this 5H vorticity center
along a SSW to NNE 850 and 700mb inverted trof.  This is supported
by strengthening VWP out of UDX generally aligned with the core of
the 850-700mb CIRA LPW across W SD into MT.  So 15-20kts of
850-700mb flow has solid speed reduction at this inverted trof
with 1.5" Total PWats reaching the area.=20

18z Surface obs denote the area is also becoming increasingly
unstable with mid to upper 80s over low to mid 60s Tds with modest
lapse rates to support 1500-2000 J/kg of MLCAPE to support the
vigorous updrafts.  Broad left entrance region to the 3H jet over
the Dakotas will support favorable divergence/outflow aloft to
maintain thunderstorms...though deep layer steering is veered to
have very slow cell motions through depth at 0-5kts from
800-300mb, but generally westward.  However, combined with
inflow/flux convergence from the SSE, propagation vectors of
5-10kts is likely to negate westward motions.=20

Given total moisture of 1.25-1.5", strong convergence; rates of
1.75"/hr are likely mixed with some hail given warm cloud depth
only to 10-11Kft.  With slow cell motions and enough bulk shear up
to 20-25kts, suggest some tilting to reduce rainfall/hail to
collapse updrafts allowing for modest longevity in the near term.
As such widely scattered totals of 2-3" are likely and may result
in widely scattered incidents of flash flooding.   Recent Visible
imagery loops suggest further expansion of scattered thunderstorms
into W ND and NW SD may occur over the next few hours.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_QxTubBhqZPZ0QwB-uezIJRKy6kqraAeo-dmK_CvJzR4z9hIp-Lqs5jacc1tu7Yu7rGl=
cQzCDYxfqr-Ggg5dvwkqaiw$  for graphic product...

ATTN...WFO...ABR...BIS...BYZ...GGW...UNR...

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

LAT...LON   47860407 47440276 46660178 45510165 44740229=20
            44940380 45200460 45360541 45680617 46290641=20
            46910636 47540591 47740540=20

=3D =3D =3D
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