Mesoscale Discussion 1575

Issued

Aug 21, 2021, 2:33 PM MDT (20:33 UTC)

Expired

Aug 21, 2021, 4:30 PM MDT

In force

117 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch unlikely

Chance of a watch

20%

The Salt Lake City radar (KMTX), 88 km from the middle of the area, began a volume at 20:34 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

957 
ACUS11 KWNS 212033
SWOMCD
SPC MCD 212033 
WYZ000-MTZ000-IDZ000-UTZ000-NVZ000-212230-

Mesoscale Discussion 1575
NWS Storm Prediction Center Norman OK
0333 PM CDT Sat Aug 21 2021

Areas affected...portions of the Intermoutnain West

Concerning...Severe potential...Watch unlikely 

Valid 212033Z - 212230Z

Probability of Watch Issuance...20 percent

SUMMARY...Scattered thunderstorm development ongoing across portions
of NV, ID, UT and WY will continue through this evening with a risk
for hail and damaging wind gusts with the strongest storms.

DISCUSSION...As of 2030 UTC, Regional WV imagery showed a
well-developed mid-level low across the northeastern US. Forecast to
move east this afternoon and evening, ascent from the low will
continue to slowly overspread much of the central Rockies and Great
Basin where a cold front lies from southwestern Wyoming into
northeastern Nevada. Radar and satellite trends show weak convection
has emerged across the area with additional development likely over
the next several hours. Driven by steep mid-level lapse rates
beneath the cold pocket aloft, RAP soundings indicate around 500
J/kg of MLCAPE is present. A mid-level speed max of 40-50 kt around
the base of the trough will support moderately strong shear profiles
supportive of organized multicells and perhaps weak supercells.
While buoyancy will be limited, low-level inverted v profiles will
support strong downdrafts with the potential for damaging wind
gusts. Cooling 500 mb temperatures (-12 to -14 C) will also support
the risk of hail, especially with the stronger cells. 

Hi-res guidance and observational trends suggest the greatest risk
for organized severe potential may be associated with storms
currently developing near the cold front from eastern NV, into
northern UT and western WY. Here, greater lift and buoyancy in
proximity to the front may contribute to stronger convection and
better potential for organization. Convective trends will be
monitored, but uncertainty on the longevity of any organized severe
threat suggests a watch is unlikely.

..Lyons/Guyer.. 08/21/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...RIW...TFX...SLC...PIH...BOI...LKN...

LAT...LON   40091347 39801430 39661559 40111589 41581476 43111341
            43981261 44721193 44961132 44871075 44271011 43181001
            42291030 41801065 41381114 40651231 40431276 40091347

Mesoscale Discussions in Idaho, 2021Mesoscale Discussions in Utah, 2021Mesoscale Discussions in Wyoming, 2021Every mesoscale discussion in 2021

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.