Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Aug 25 2023 16:05:06

AWUS01 KWNH 251605
FFGMPD
KSZ000-NEZ000-COZ000-WYZ000-252100-

Mesoscale Precipitation Discussion 0975
NWS Weather Prediction Center College Park MD
1204 PM EDT Fri Aug 25 2023

Areas affected...central High Plains

Concerning...Heavy rainfall...Flash flooding likely

Valid 251601Z - 252100Z

SUMMARY...Areas of flash flooding are expected to become more
numerous across portions of the central High Plains into the early
afternoon. Rainfall rates of 1-2 in/hr will be possible.

DISCUSSION...1530Z regional radar imagery showed areas of
stratiform rain with embedded thunderstorms extending from
southeastern WY into the NE Panhandle and northeastern CO.
MRMS-derived rainfall rates have peaked in the 1-2 in/hr range
with the slower moving stronger cores in the area over the past
few hours. The region is located in an upslope flow environment
behind a cold front and north of a 850-700 mb low located along
the CO/KS border. 15 to 30 kt northeasterly to east-northeasterly
winds in the 850-700 mb layer to the north of the low were
supporting an upslope flow environment within a weakly unstable
but very moist environment. 15Z SPC mesoanalysis data showed 1.1
to 1.4 inch precipitable water values along the tri-state region
of WY/CO/NE, standardized anomalies of +2 to +3 via the GFS for
late August. Flow in the upper levels was also modestly diffluent,
helping to support lift over the region.

The biggest change expected over the next few hours is the
increase of instability with daytime heating. While instability is
expected to remain weak within areas of dense cloud cover and
ongoing rainfall, areas to the south and east will become
increasingly unstable this afternoon with MLCAPE expanding into
the 500-1000 J/kg range, potentially supporting a few isolated
cells, capable of 1-2 in/hr rainfall rates. Farther back to the
west, upslope flow will remain fairly steady as the 850-700 mb low
drifts slowly east, continuing slow moving cores of heavy rain
with embedded thunder across portions of the Front Range and
potential for 1-2 in/hr rates. Despite dry antecedent conditions,
these rates are expected to overwhelm area FFG that is largely 1-2
inches in an hour. Localized totals of 2-3 inches will be possible
by 21Z.

Otto

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!636912wUl6KaxVNkBn1i6AE8ADf9hQfi5zGWnHqCEMFmde4VaYXDfuZugBTNvXGdENLq=
N_npWrZJbbBkKx1T69UmIA0$  for graphic product...

ATTN...WFO...BOU...CYS...GLD...LBF...

ATTN...RFC...ABRFC...CBRFC...MBRFC...NWC...

LAT...LON   42420492 42310430 42090364 41760297 41600230=20
            41270153 41010050 40430029 39980044 39520180=20
            39210309 39190544 39980600 41010594 41820577=20
            42400582=20

=3D =3D =3D
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