Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 221637

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1037 AM MDT Sun May 22 2022

.DISCUSSION...(Today Through Saturday)
Issued at 200 AM MDT Sun May 22 2022

Broad upper trough remains across much of NOAM, with anomalously
cold air over much of the northern CONUS. The next mid level
impulse is advecting across the Pac NW and into the northern
Rockies and will approach the region today. Mostly sunny skies and
warmer temps on track today, although clouds will begin to
increase west-east this afternoon. Very dry air will remain in
place today and even SE return flow wont make too much progress
in increasing LL moisture. However, residual cold pool aloft will
support diurnal instability over the northern BH this afternoon,
with enough CAPE to support a shower or even a TS this afternoon.
With a later arrival time of the next impulse and very dry
profiles, have trimmed pops this afternoon to just the northern
BH. Compact but strong impulse will move into the region tonight,
and support increasing chances for rain, esp across sw-scentral
SD. Sharp cut off in precip expected with this system to the NW
with dry air limiting northward progression. If precip does
materialize in the BH, some snow would be expected, with light
accums possible. Upper impulse will slowly push east Monday with
steady rain expected across scentral SD. Low clouds and rain is
expected to remain over the SE third, limiting temps there to just
40s and 50s for highs. Further NW, sfc trough combined with
increased LL moisture will support sct afternoon shra/TS, with
terrain driven shra possible over the BH if enough insolation is
present. Things will dry out Monday night with mostly clear skies
and cool temps supporting areas of frost once again. Lingering
unstable cyclonic flow aloft with SE upslope flow will support
diurnal shra/ts Tues afternoon over the western third to half.
Seasonably cool temps will continue with highs in the 60s. A ridge
of high pressure will then build over the Rockies and push east
toward the later half of the week, supporting much warmer and
mainly dry weather. Still looks like 70s and 80s can be expected
for highs after Wed, warmest Friday when a sfc trough moves
through the region with the thermal ridge. However, the ECMWF has
continued its trend keeping the bulk of warm air SW of the FA,
given the advection of a backdoor cool front into the region Thur
night. Cooler and unsettled conds looks to return this weekend
into next week.


.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1033 AM MDT Sun May 22 2022

VFR conditions expected to prevail through this evening. After
midnight, MVFR conditions in rain showers will move in from the
southwest. Northern portions of the area will remain VFR through
the period.




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