Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 231057
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
457 AM MDT Mon Apr 23 2018

.DISCUSSION...(Today Through Sunday)
Issued at 354 AM MDT Mon Apr 23 2018

Upper level analysis has broad ridge over the central CONUS with
compact shortwave crossing the northern Rockies at the moment.
Skies are mostly clear across the northern Plains. At the surface,
low pressure is located across central Wyoming with stationary
boundary extending into western North Dakota. Temperatures at 4am
are in the 40s with light and variable winds.

Broad upper ridge will shift east as western shortwave trof
crosses the Rockies. Most of the area will see a nice day as
cloud cover increases from west to east with the approaching storm
system. High temperatures will range from the lower 50s across
northeast Wyoming, to the upper 60s across south central South
Dakota. Some rain showers will be possible across northeast
Wyoming by the afternoon, with some isolated Thunderstorms
possible from the southern Black Hills into southwest South Dakota
by late afternoon.

Precipitation will continue to spread across the area this evening,
as rain, with some thunderstorms possible across southwestern
South Dakota during the early evening hours. By mid evening, rain
will change to snow across northeast Wyoming and the higher Black
Hills as the mid level low draws in cooler air aloft. Cold front
will drop south through the area overnight, producing some breezy
north winds, and a good period of upslope enhanced snow across the
Bear Lodge and northern Black Hills. Looks like 2 to 4 inches of
snow are likely across the Spearfish and Sturgis foothills, and
up to 6 inches is expected across the higher Black Hills. A winter
weather advisory has been issued for these areas from this evening
through Tuesday morning. By very late tonight, pressure gradient
tightens up just east of the Black Hills, producing fairly gusty
north winds of 25 to 35 mph.

Upper level trof and mid level low shift into central South Dakota
by mid day Tuesday, with precip winding down across much of the
area. Rain and snow will persist across south central South Dakota
into Tuesday afternoon, before shifting east by Tuesday night.
Cooler air will remain across the area on Tuesday, with
temperatures only in the 40s for most locations. Clear and cool
conditions are expected Tuesday night, with lows in the 20s and
30s.

Temperatures will rebound a bit for Wednesday as a shortwave ridge
crosses the area. Another upper trof will drop through the area on
Thursday, this time with minimal precipitation. But temperatures
will cool again, and northwest winds will be breezy. Upper ridge
will finally take over for Friday into the weekend, with mainly
dry conditions and very mild temperatures.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Tuesday Morning)
Issued At 454 AM MDT Mon Apr 23 2018

Rain will spread across northeast Wyoming and far western South
Dakota today and across the rest of the area tonight. Rain will
change to snow over portions of northeastern Wyoming, the Black
Hills and northwestern South Dakota late this evening. Ceilings
will lower with the rain this afternoon, with area of MVFR
ceilings in northeast Wyoming and far western South Dakota.
IFR/local LIFR visibility expected with the snow tonight.

There is a slight chance of thunderstorms this afternoon over
parts of northeastern Wyoming and southwest South Dakota. Gusty
northwest winds will found across the area tonight, with the
strongest winds around the KRAP terminal...with gusts around
45kts.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 9 PM this evening to 9 AM MDT
     Tuesday for SDZ024-025-072.

WY...Winter Weather Advisory from 9 PM this evening to 9 AM MDT
     Tuesday for WYZ057.

&&

$$

DISCUSSION...15
AVIATION...7


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