Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 281728
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1028 AM MST Mon Nov 28 2016

.UPDATE...
Issued at 1022 AM MST Mon Nov 28 2016

Band of pcpn currently expanding southwest across nwrn through
scntrl SD late this morning, and is a bit quicker than expected so
have raised pops for these areas today into this evening. Latest
model data showing a bit more snow accumulation potential across
Mellette and Todd counties so have expanded the winter weather
advisory into that area, while also beginning the advisory at 00z
(instead of 06z) given the quicker progression of the pcpn band.

&&

.SHORT TERM...(Today Through Tuesday Night)
Issued at 245 AM MST Mon Nov 28 2016

Current surface map places 976mb low near KATY with 14mb pressure
gradient across the forecast area. Area of snow slowly backing
into northwest South Dakota. Models in decent agreement...keeping
the vertically stacked low over southeast North Dakota/northeast
South Dakota through early Tuesday, then slipping into southern
Minnesota. Trowal wraps back into western South Dakota late today
and remains across the forecast area into Tuesday night. Moist low
level flow with steep lapse rates will result in upslope enhanced
snowfall across the northern Black Hills and Bear Lodge Mountains,
with the heaviest snowfall rates later tonight into Tuesday. Will
also see some upslope enhancement across the northern portions of
northeast Wyoming and along the Pine Ridge in southwest South
Dakota.

Duration of upslope for northern Black Hill along with mean low
level flow should result in snowfall amounts around 12 inches for
the Four Corners/Sundance/Deadwood area, with locally higher
amounts around the O`Neil pass area. The I-90 corridor from
Spearfish to Sturgis will also see 6 to 8 inches, with snowfall
amounts dropping off significantly from Sturgis to Rapid City.
Rapid City will be in area of downslope flow and will see an inch
or less. Snowfall amounts on the plains will be variable based on
terrain. The biggest issue on the plains of western South Dakota
will be the wind. Already had wind gust to 61 mph here at the
office, with 40-50 mph gusts on the plains north and east of the
Rapid City. Upgraded northwest South Dakota to winter storm
warning for combination of snow and winds. While conditions may
technically reach blizzard criteria, not expecting the impact of
significant snowfall and/or drifting that would shut things down.
Also went with winter weather advisory down to the Nebraska border
instead of the wind advisory due to the snowfall accumulation/wind
combination. Conditions begin improving from west to east Tuesday
night.

.LONG TERM...(Wednesday Through Sunday)
Issued at 245 AM MST Mon Nov 28 2016

Storm system will finally move away from the region on
Wednesday, with decreasing chances for snow over eastern portions of
the cwa. Breezy to windy conditions can be expected on Wednesday
over the SD plains, before winds finally diminish Wednesday evening.

Mainly dry weather is expected for the rest of the week and the
weekend as the next west coast system dives south over the western
states late in the week and should remain south of the region into
the weekend. Weaker northern stream energy could bring a few snow
showers at times from Thursday through the weekend, mainly over the
northern Black Hills area. Temperatures will be near or slightly
below average late this week, with a slight warming trend over the
weekend.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Tuesday Morning)
Issued At 440 AM MST Mon Nov 28 2016

MVFR/IFR conditions generally northeast of a line from 2WX to ICR
this morning, with areas of light snow. These conditions will
slowly move south and west across the rest of the forecast area
this afternoon and tonight, with areas of LIFR conditions
developing over northwest SD into the northern Black Hills and far
northeast WY as snow increases. General VFR conditions are likely
to remain across the southern Black Hills and far southwest SD
through much of tonight. Strong northwesterly winds can be
expected across much of the plains today, decreasing a bit
tonight. The strongest winds will be in the Rapid City area, where
a few gusts to around 50 kts are expected today.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Storm Warning from 5 PM this afternoon to 5 AM MST
     Wednesday for SDZ001-012-024-025-028-072.

     Winter Weather Advisory from 5 PM this afternoon to 5 AM MST
     Wednesday for SDZ013-030>032-042>044-073.

     Winter Weather Advisory from 6 PM this evening to 7 PM CST
     Tuesday for SDZ046-047.

     Wind Advisory until 5 PM MST this afternoon for SDZ001-012-013-
     030>032-072-073.

     Winter Storm Warning until 5 AM MST Wednesday for SDZ002-014.

     Wind Advisory until 11 PM MST Tuesday for SDZ026-074.

WY...Winter Storm Warning from 5 PM this afternoon to 5 AM MST
     Wednesday for WYZ057-071.

     Winter Weather Advisory from 8 PM this evening to 11 PM MST
     Tuesday for WYZ054-056.

&&

$$

Update...Johnson
SHORT TERM...7
LONG TERM...26
AVIATION...26



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