Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 230517

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1017 PM MST Thu Feb 22 2018

.DISCUSSION...(This Evening Through Thursday)
Issued at 247 PM MST Thu Feb 22 2018

Deep upper trough is persisting across the western CONUS, with
southwesterly flow over the central Rockies through the northern
Plains and upper Midwest. Broad surface low pressure is deepening
across the central Plains into central South Dakota. KUDX radar
shows snow moving into central South Dakota over the last few hours.
Snow will continue to fall tonight mainly over south central SD
where anywhere from 1 to 4 inches of accumulation are expected. It
still looks like the higher snowfall amounts will be limited to
Tripp County. Will continue with the Winter Weather Advisory for
Tripp until 9 PM CST. Snow will quickly end by mid to late evening.
Lows tonight will drop to around 5 below to 10 above zero. Surface
high pressure and weak upper ridging will build in for Friday. Dry
weather is expected with highs similar to today. The western upper
trough will slide eastward Saturday with a surface low strengthening
near Kansas/Nebraska. Wrap around precip will move into the region,
but mostly stay south and east of the CWA. South central South
Dakota will likely see another round of accumulating snow. Right now
it appears to be another 1 to 3 inches total late Friday night into
Saturday. Generally dry weather is then expected through Sunday and
Monday. Highs will be in the upper 20s into the 30s. Right now
models are indicating some light snow possible Tuesday or Wednesday
as a shortwave trough pushes through.


.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 1017 PM MST Thu Feb 22 2018

In the wake of this evening`s light snow, MVFR/IFR cigs have
developed across portions of the SD plains, particularly along and
east of a line from KD07 to KIEN. These are expected to drift
southeastward out of our area by 10z, allowing VFR conditions to
prevail area-wide through Friday afternoon.

Conditions will begin to deteriorate from south to north across
eastern WY/western NE late in the TAF period as snow overspreads
the region. Associated lowered cigs/vsbys could reach the southern
Black Hills, and potentially even approach our TAF sites, by 06z
tomorrow evening. For now, however, expecting VFR conditions to
prevail through the TAF period at KRAP/KGCC.




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