928
AWUS01 KWNH 121641
FFGMPD
WYZ000-UTZ000-NVZ000-122240-

Mesoscale Precipitation Discussion 0869
NWS Weather Prediction Center College Park MD
1241 PM EDT Mon Aug 12 2024

Areas affected...Much of Utah...East-central Nevada...Southwest
Wyoming...

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

Valid 121640Z - 122240Z

SUMMARY...Stronger than normal FGEN and moisture flux with deeper
steering capable of repeating thunderstorms poses potential for
scattered flash flooding incident(s) this afternoon.

DISCUSSION...GOES-E Visible imagery has seen a narrow banded
feature of weak convective elements across central UT with
favorable orientation for training, while not currently an issue,
it denotes potential this early in the morning for the environment
given dynamic set-up and orientation.   GOES-E WV shows classic-T
shape of mid to upper-level flow regime noting a old elongated but
still strong shortwave feature across the Lower Colorado River
Valley with some northerly stretching coming into SW UT; favorable
anti-cyclonically arched feature across south-central to northeast
UT shows the southern stream return flow of the monsoon, while a
second polar band of enhanced cirrus
denoting broad scale ascent in the favorable ridged entrance to
the broad jet across Northeast NV before becoming more flat across
western WY, where an exiting stronger mid-level shortwave is
analyzed.   As such, there is ample broad scale ascent across the
UT at this time, stretching into peak early morning period.

CIRA LPW denotes favorable channels of 850-700mb flow up the
Colorado River Valley into W UT, while 700-500mb layer notes a
similar slug in that regime, but also what appears to be a
cyclonically curled moisture pocket across eastern NV.  Enhanced
700mb Tds of 5-8C are analyzed across N Lincoln and White Pine
county.  RAP surface analysis aided the detection of a surface
effective dry line across south-central NV north toward the
UT/ID/NV corner where mid to upper 50s (isolated low 60s) Td
rapidly decreases into the 30s and even mid 20s through central
NV.  FGEN/theta-E gradient alignment is very strong for the
Intermountain west.   As such total depth TPW is well over .75"
across much of the area with 1" through the lower valleys across
the NV/UT border and into the Salt Flats of NW UT.

Currently, instability continues to build with the increasing
insolation across the eastern NV enhanced moisture field with
1000-1500 J/kg still generally capped, though an isolated cell has
begun the deeper convective process.  This activity is expected to
grow in coverage given the favorable DPVA across the central UT
terrain but also back across E NV into NW UT with the stronger
FGEN/UL Jet ascent pattern.  Modest 20-25kts of moisture flux
through the Colorado Valley into cloud bases around 800-700mb,
should allow for rates of 1-1.5"/hr.  Deep layer steering from SW
to NNE (slowly converging on the eastern side due steering ridge)
will increase potential for repeating.  As such a spot or two up
to 2-2.5" is possible through 22z, though a greater coverage of
1-2" spots are probable resulting in scattered incidents of flash
flooding through early evening.

Gallina

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...GJT...LKN...RIW...SLC...VEF...

ATTN...RFC...CBRFC...CNRFC...NWC...

LAT...LON   41961078 41750986 41150927 39870916 39200998
            38571073 37751121 37101171 37051259 37081340
            37701354 38091394 37801472 37901529 38371564
            39251518 40661370 41781193