Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Aug 25 2024 21:03:21

AWUS01 KWNH 252103
FFGMPD
COZ000-NMZ000-WYZ000-AZZ000-UTZ000-260200-

Mesoscale Precipitation Discussion 0927
NWS Weather Prediction Center College Park MD
502 PM EDT Sun Aug 25 2024

Areas affected...Four Corners...Eastern UT... Western
CO...Southwest WY...

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

Valid 252100Z - 260200Z

SUMMARY...Narrow but potentially repeating lines of thunderstorms
pose localized spots of 1-2" totals and possible flash flooding
conditions in rugged terrain.

DISCUSSION...GOES-E EIR shows increasing coverage and cooling of
thunderstorm tops across the Four Corners into E UT and SW CO,
generally coincident with banded temperature features in the WV
channels.  Strong height-falls from 1.5-2 std. dev. closed low in
the Great Basin is further tightened by sheared/elongated
shortwave features along the northwest edge of the strong Southern
Plains ridge.  As such, fairly deep unidirectional flow exists
across the area with above average (about 1.5 std. dev) of
moisture through depth.   Tds are in to the low 50s in the
valleys/Canyonlands and but mid 40s Tds exist through 700mb along
the UT/CO boarder and result in .75 to 1" total PWat values for
thunderstorms.=20

Steepening lapse rates aloft, support those enhanced CAPE values
of 1000 to very spotty maxima of 2000 J/kg to support these
stronger thunderstorms.  Moisture flux at cloud base is 15-20kts
generally confluent, so isallobaric influences may support
enhanced directional convergence with the stronger cells.  Some
cells are nearing -60C showing consistent vigor.  Favorable right
jet entrance to the 90kt south to north jet across central UT will
provide solid divergence and allow for maintenance or even slight
upscale growth to clusters over the next few hours.  However, that
stronger flow is limiting cell residency but sub-hourly totals of
..25-.5" in less than 30 minutes is still problematic for steeper
terrain; but more likely flash flooding will require repeating
cells.  At this time, upstream flow is strong and the cold front
appears to be crossing through the Wasatch/central spine of UT as
Tds are starting to drop into the 30s west of the terrain.  This
sharpening with solid 15-20kts of 850-700mb LLJ inflow ahead of
the cold front will allow for back-building environment through
the evening.  Limited difference between propagation vectors and
mean cell motions will provide above average potential for
repeating cells with capability of 1-2" totals in these narrow
lines.   As such, scattered incidents of flash flooding will
remain possible through the evening hours. across the area.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8_py1AwBrurmjxg7cDiyn7OI92L7XtNqA3FUMLpA0sQK2B9EQOswVPrsYz1_IMOSf74Q=
NVIbxvAoENy5cWfusdmtvc8$  for graphic product...

ATTN...WFO...ABQ...BOU...CYS...FGZ...GJT...RIW...SLC...

ATTN...RFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON   42260875 42150782 41720709 40960651 39920659=20
            38900693 37890738 36000859 36140977 37331023=20
            37901071 38841044 39891061 40751072 41781015=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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