792 
FXUS63 KUNR 181705
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1005 AM MST Mon Nov 18 2019

.UPDATE...
Issued at 900 AM MST Mon Nov 18 2019

With sustained winds of at least 30 mph and wind gusts over 45 mph
ongoing across portions of the wrn SD plains, opted to bump up 
start time of wind advisory to now. Strongest sustained winds and
gusts should shift eastward through the morning and afternoon as 
low-level speed max moves into cntrl SD. Rest of the forecast 
remains on track.

&&

.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 SD 
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 CONUS.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1005 AM MST Mon Nov 18 2019

VFR conditions should continue through the TAF period. Breezy NW
winds with occasional strong gusts of 40-45 kt across the wrn SD
plains will continue through approximately 21-22z before 
diminishing. 

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 4 PM MST /5 PM CST/ this afternoon for 
     SDZ001-002-012>014-025-026-030>032-043-044-046-047-049-072-
     073.

WY...None.
&&

$$

Update...Sherburn
DISCUSSION...10
AVIATION...Sherburn