Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat May 27 2023 23:36:37

AWUS01 KWNH 272336
FFGMPD
MTZ000-WYZ000-280400-

Mesoscale Precipitation Discussion 0361
NWS Weather Prediction Center College Park MD
736 PM EDT Sat May 27 2023

Areas affected...Eastern Montana...

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

Valid 272335Z - 280400Z

SUMMARY...Slow moving thunderstorms capable of 1.25"/hr rates pose
local flash flooding concerns.

DISCUSSION...GOES-E WV denotes mature core fairly stationary
upper-level low along the Alberta/Montana boarder near Cut Bank
with well defined baroclinic leaf and dry slot across eastern MT.
A sharp 500-300mb trough extends southward across W WY into CO
that has been providing favorable jet entrance ascent pattern for
backing low level flow out of the High Plains, directing enhanced
low level moisture across/north of the Big Horn Mtns.  The western
edge of this enhanced moisture reaches an 850-700mb FGEN zone from
the Big Horns north to a weak low denoted well in Visible cloud
lines/convection near CWVN.=20

Moisture is pooled along the boundary with Tds in the 50 and low
60s through 850mb.  Ample insolation through the afternoon has
resulted in ample unstable environment along and east of the
boundary with pockets of MLCAPE of 1000-1500.  Aloft, return flow
within the TROWAL from prior days has rotated around and sharpened
in the vicinity of the boundary resulting in 700mb RH maxima of
70-90% aiding in rainfall production for thunderstorms that have
developed along it.  Regional observations have seen totals of up
to 1" in the vicinity north of Billings, MT with other .75-1"
values dotting northward.

FFG values in the region are reduced due to above average
saturation in the upper levels of the soil with these rates/totals
generally being exceeding the 1-3hr values. MRMS Flash responses
show scattered 200-400 cfs/smi values suggestive of possible flash
flooding.  While eastward propagation is expected due to easterly
inflow/advection of unstable air to maintain thunderstorms; deep
layer flow along the 850-700mb boundary is generally parallel to
it support the potential for continued cross tracks/repeating over
the next few hours.  As such localized flash flooding is possible
to continue through this evening into the overnight period.=20=20

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9Ikgf-UvmOBgirougITole_d5UGRfD0LOFo4452LW122Nevnb2L4GJVSlbgs0IW5aCbw=
ZLc34GbiUjk4uUvfXjAZoBc$  for graphic product...

ATTN...WFO...BYZ...GGW...

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

LAT...LON   48910795 48860618 47770584 45610638 44750694=20
            45050800 45270884 45900907 46800843 47730810=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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