Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 271028
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
428 AM MDT Thu Apr 27 2017

.DISCUSSION...(Today Through Wednesday)
Issued at 358 AM MDT Thu Apr 27 2017

Upper level analysis has large trof across the central CONUS with
weak shortwave ridge embedded in the larger trof. Skies are mostly
cloudy across the Northern Plains with the exception of a sliver
of clear skies across the western Dakotas into central Nebraska.
At the surface, Canadian high pressure resides across the Dakotas,
with low pressure centered across central Wyoming. Temperatures at
4am are in the 20s to lower 30s, and winds are light and variable.

Today...The next spring storm system will begin to impact western
portions of the area, with chances for rain and snow increasing
across northeast WY into southwest SD this morning. Most of the
pcpn should be in the form of rain later in the day as slightly
milder air pushes in. Highs will be in the 40s and lower 50s,
warmest over eastern areas where there will be more sun.

Tonight...Latest model consensus still showing potent system
shifting into eastern Wyoming and spreading into southwestern
South Dakota early this evening. Rain will quickly change over to
snow across northeast WY and the Black Hills this evening as
temperatures cool. With high pressure over the central Dakotas,
most of the precip should be confined to the Black Hills area and
west. Snowfall amounts look to be on the lighter side on the
eastern fringes, with around 1 to 3 inches across the Black Hills.
A little more snow is expected south and west of the Black Hills,
with accumulations up to 6 inches across parts of far western Fall
River County, Weston County, and areas west of Gillette. However,
across southern Campbell County where the heaviest pcpn is
forecast, 6 to 8 inches of snow is possible, especially across
the higher elevations. A Winter Storm Warning has been issued for
southern Campbell County through Friday afternoon, with Winter
Weather Advisories posted for northern Campbell, Weston, and Fall
River Counties. Pcpn will dissipate and shift south of the area
Friday night as system moves into the Central Plains. Lows tonight
will be in the 20s to lower 30s.

The weekend looks mainly dry, but remaining cool, as large trof
lingers over the region. Will see temperatures possibly
approaching average early next week, but unsettled weather will
return for at least the first half of the week. Active northwest
flow on the back side of the trough will bring several
disturbances across the area, with daily chances for showers in
most areas. The bulk of the activity should come during the
afternoon and evening hours.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 1128 PM MDT Wed Apr 26 2017

Skies have cleared out across the terminal locations...with sat
pix showing widely sct mvfr clouds still lingering. temp/dwpt
spreads of 5 degrees or less and fcst winds of less than 5kts
still provide confidence in some fog development between 09z and
12z this morning...and latest MOS guidance is now picking up on
that. Approaching system will keep general VFR cigs in the KGCC
terminal through remainder of the day...with -shra moving in aft
28/00z. KRAP will also see a general increase in VFR cigs through
the day but any pcpn should hold off until aft 28/00z.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 6 PM this evening to 6 PM MDT
     Friday for SDZ041.

WY...Winter Storm Warning from 6 PM this evening to 6 PM MDT Friday
     for WYZ055.

     Winter Weather Advisory from 6 PM this evening to 6 PM MDT
     Friday for WYZ054-058.

&&

$$

DISCUSSION...15
AVIATION...Hintz


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