Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 240537

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1037 PM MST Fri Feb 23 2018

.DISCUSSION...(This Evening Through Friday)
Issued at 125 PM MST Fri Feb 23 2018

A large upper trough stretches across the central and
western CONUS, with southwest flow over the CWA. Satellite shows
mostly clear skies over western SD and northeastern WY. At the
surface, high pressure sits over SD. Winds across the CWA are 5-10
mph, and temperatures are in the single digits and teens, with some
20s and 30s in the Hills. Smoke from Black Hills pile burning
continues to linger around the Rapid City area under the inversion.

Snow will begin spreading across the area tonight as the initial
wave associated with the upper trough crosses the northern plains.
Most of the snow will be across eastern SD on Saturday, where there
will be better moisture and forcing. South central SD may see a
couple inches of snow by Saturday evening, with lesser amounts
farther west. Secondary impulse will move through Sunday, but mostly
dry weather is expected, except for the possibility of a few upslope
snow showers over the northern Hills.

Mainly dry conditions are expected next week under somewhat zonal
flow. Models are showing a low pressure system developing over
southern CA early in the week, but most of the energy associated
with this system should stay south of the CWA. Temperatures will
remain slightly below average this weekend into next week, with
highs in the 30s.


.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1037 PM MST Fri Feb 23 2018

MVFR cigs/vsbys are overspreading portions of northeastern WY and
southwestern SD this evening as an area of snowfall approaches from
the south. For now, snow has been sparse across our area, remaining
south of a KGCC to KECS line in WY. Models have consistently kept this
snowfall south of KGCC, so have maintained VFR conditions in the TAF.
However, it is plausible KGCC cigs could briefly drop to MVFR prior
to 09z before recovering thereafter. The western batch of snowfall
across WY should dissipate as more widespread snow develops over the
NE panhandle and southwestern SD.

MVFR/IFR cigs will gradually spread northward and eastward overnight,
primarily along and east of a line from KIEN to KD07. Given very dry
conditions sampled in the 00z radiosonde launch from Rapid City, it
is unlikely snow will develop as far west as KRAP. However, will see
gradually lowering cigs (though still VFR) at KRAP tonight through
early Saturday before conditions improve. MVFR/IFR cigs/vsbys will
shift eastward over the SD Plains tomorrow afternoon before VFR
conditions prevail area-wide after 00z.




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