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fxus63 kunr 180918 
afdunr

Area forecast discussion for western South Dakota and northeastern Wyoming
National Weather Service Rapid City South Dakota
218 am MST Mon Nov 18 2019

Discussion...(today through sunday)
issued at 152 am MST Mon Nov 18 2019

Scattered showers early this morning will exit the forecast area
to the east over the next few hours, leading to a dry and mostly
sunny day today as synoptic scale subsidence develop behind the
departing shortwave.

The main forecast problem for today concerns the potential for
very windy conditions to develop on the plains of western South
Dakota. 850mb wind speeds increase to 45-50kts over western South Dakota
this morning and then decrease to 35-40kts this afternoon. There
remains some question if the cold advection and resultant mixing
will be strong enough to Transfer some of that momentum aloft to
the surface. Due to the strong 850mb winds, the potential exists
for winds to reach Wind Advisory criteria, so have issued wind
headlines for much of the western South Dakota plains from late
this morning into this afternoon. The wind should decrease later
in the afternoon as the cold advection aloft is replaced by weak
warm advection as an upper ridge moves in from the west. The upper
ridge will keep mild temperatures over the region through Tuesday.

As the ridge shifts off to the east on Tuesday night, an upper
trough will approach from the west and a cold front will move
through at the surface. Low level cold advection combined with a
moist boundary layer and prolonged weak lift will support chances
for a wintry mix of precipitation on Wednesday, with freezing
drizzle possible before an increase in mid-level moisture and
lift brings increasing chances for snow. The splitting nature of
the system will support limited snow amounts, with the best chance
for light snow accumulation over the far southern parts of the
forecast area.

After a couple of cool days on Wednesday and Thursday, dry and
slightly warmer weather will return on Friday, and will continue
through the weekend.

Model ensembles are indicating cooler weather will return next
week as the pattern adjusts and the mean western noam ridge breaks
down, allowing the jet stream to settle southward over the Continental U.S..

&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 152 am MST Mon Nov 18 2019

Scattered showers will move across the area tonight with local
MVFR conditions. Lowest conditions will be across the Black Hills
with some brief period of IFR conditions. Gusty northwest winds
will develop overnight and continue into Monday afternoon.

&&

Unr watches/warnings/advisories...
South Dakota...Wind Advisory from 11 am MST /noon CST/ this morning to 4 PM MST
/5 PM CST/ this afternoon for sdz001-002-012>014-025-026-
030>032-043-044-046-047-049-072-073.

Wyoming...none.
&&

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