Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 180525

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1025 PM MST Fri Feb 17 2017

.SHORT TERM...(This Evening Through Saturday Night)
Issued at 215 PM MST Fri Feb 17 2017

Current surface map places trof across the eastern Dakotas.
Breezy, sunny and mild conditions across the forecast area. Clear
skies continue into tonight as shortwave ridge builds aloft.
Increasing pressure falls late tonight will result in gusty
southwest winds across portions of northeast Wyoming into the
Black Hills overnight. Another warm day across the area for
Saturday, with the warmest temperatures in downslope flow for
northern/eastern foothills.

.LONG TERM...(Sunday Through Friday)
Issued at 215 PM MST Fri Feb 17 2017

Upper level ridge shifts east on Sunday. Boundary layer to 850mb
temperatures support highs in 60s to lower 70s. Sharp upper trof
crosses the area Sunday night and Monday. Strong lift and steep
mid level lapse rates will bring widespread showers. Thermal
profiles and SREF precipitation type support rain for most of the
plains. Portions of northeast Wyoming into northwest South Dakota
may see a rain/snow mix Sunday night, while a few inches of snow
may accumulate in the higher elevations of the Black Hills. Dry
with mild temperatures Tuesday and Wednesday.

GFS/ECMWF/GEM coming into better agreement for storm system
Thursday into Friday. Surface low track and strength from GEFS
members starting to converge, taking low on favorable track for
widespread precipitation across the forecast area. Some
differences between GFS/ECMWF/GEM with thermal profiles Thursday.
ECMWF supports snow most of the day for western South Dakota,
while GEM keeps temperatures warm enough for rain much of the day.
GEFS members range 850mb temperatures range from -5C to +5C
Thursday morning with cooling temperatures through the day.
Confidence increasing for some heavy snowfall across the forecast
area. However, still enough variability in storm track, timing,
and thermal profiles to get too specific with snowfall amounts for
any one location. As an example, GEFS members show snowfall for
Rapid City ranging from an inch to more than a foot.


.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1021 PM MST Fri Feb 17 2017

VFR conditions are expected through the forecast period, except
perhaps over northeast WY through 12z with local MVFR CIGS south
of KGCC. Gusty southerly winds will develop across northeast
Wyoming and the Black Hills overnight and continue into Saturday




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