Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 211808
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1208 PM MDT Tue Mar 21 2017

.UPDATE...
Issued at 605 AM MDT Tue Mar 21 2017

Snow continues to decrease in coverage and intensity across
northeast Wyoming and northwest South Dakota. Forecast updated to drop
winter weather advisory.

&&

.SHORT TERM...(Today Through Wednesday Night)
Issued at 315 AM MDT Tue Mar 21 2017

Current surface map places 1038mb high across southern
Saskatchewan/Manitoba into the Dakotas. Upper level shortwave
crossing the western South Dakota bringing area of precipitation
from southeast Montana into western South Dakota. Predominately
snow across far northeast Wyoming and northwest South Dakota, with
rain across southwest and south central South Dakota. Bulk of rain/snow
will end this morning as shortwave moves into eastern South
Dakota. However, moist east-southeast upslope boundary layer may
support some very light precipitation into this afternoon around
east side of the Black Hills.

Scanning DOT webcams, snowfall having a hard time accumulating on
roads. With lack of current snowfall reports, will leave headlines
in place for at least a few hours.

Upper level ridge builds across the northern plains tonight with
warm front pushing through western South Dakota. Area of
isentropic lift will bring some light precipitation. Forecast
soundings support a mix of rain/freezing rain/snow.

.LONG TERM...(Thursday Through Monday)
Issued at 315 AM MDT Tue Mar 21 2017

Medium range models in decent agreement Thursday/Friday with upper
low closing off over the central Rockies and moving into the
central plains. This puts forecast area south of Interstate 90 on
northern edge of precipitation. Thermal profiles support mainly
rain. Black Hills marginally cold enough for snow Friday while
south central South Dakota could transition to snow late
Friday/Friday night.

Active pattern continues into early next week with several upper trofs
moving across the Rockies into the plains.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1206 PM MDT Tue Mar 21 2017

Widespread IFR/local LIFR conditions will continue over western SD
through this evening with some improvement late, and especially
Wednesday morning. Areas of -FZDZ/FZFG/BR will be present. Later
tonight, some -FZRASN are expected over western SD. Areas IFR
conditions due to stratus/BR over northeast WY will slowly improve
this evening with rapid improvement overnight.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

Update...7
SHORT TERM...7
LONG TERM...7
AVIATION...Helgeson



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