Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 162125

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
225 PM MST Thu Nov 16 2017

.DISCUSSION...(This Evening Through Thursday)
Issued at 148 PM MST Thu Nov 16 2017

Latest SFC analysis shows a warm front extending from a low
pressure center in central Montana to just north of the Black
Hills and then arcing to the northeast toward Faith. A very tight
sfc temperature gradient exists along the frontal boundary this
afternoon with a 29F degree difference at 2PM between Spearfish
66F, and Belle Fourche 37F. High temperatures have reached the
lower 70s on the plains of southwestern South Dakota.

Tonight, the upper ridge will continue to shift off to the east of
the forecast area as the upper trough drops southeastward toward
the northern plains. A narrow band of low and mid level
frontogenesis will support low PoPs especially late tonight across
far northwestern South Dakota and parts of northeastern Wyoming.

On Friday, the upper trough will continue to move southeastward
across the northern Plains as the main cold front crosses the
forecast area. A narrow band of moderate to strong 850-700mb
frontogenesis is forecast to cross the region rather rapidly
behind the cold front. Expect some light snow accumulations on the
plains, mainly on Friday evening, with 1 to 3 inches possible over
the northern hills.

Cooler temperatures Saturday will be replaced by warmer than
average temperatures Sunday and Monday. Then, substantial
guidance uncertainty develops for the rest of the upcoming
Thanksgiving Holiday. Consensus is for average to slightly warmer
than average temperatures with little precipitation, but
confidence is low due to a lack of run to run model consistency.


.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 148 PM MST Thu Nov 16 2017

VFR conditions are expected through the period. Low-level wind
shear will continue across the South Dakota plains through this
afternoon. Look for breezy SW winds across the western half of
the area today, especially across northeastern WY and the Black
Hills area. Winds will shift NW behind a cold front this evening,
and light rain/snow will begin moving into the CWA after
midnight, along with MVFR ceilings and visibilities.


Issued at 148 PM MST Thu Nov 16 2017

Colder air with higher relative humidity will move into the area
tonight and Friday as a cold front moves through and
precipitation chances increase.




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