Area Forecast Discussion
Issued by NWS Rapid City, SD

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290
FXUS63 KUNR 261719
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1119 AM MDT Thu Apr 26 2018

.DISCUSSION...(Today Through Wednesday)
Issued at 339 AM MDT Thu Apr 26 2018

Upper level analysis at 3am has trof axis moving through the
Dakotas with sharp ridge across the western CONUS. Some cloud
cover and very light sprinkles associated with the trof, but bulk
of activity is pushing south of the area quickly. At the surface,
cold front has pushed through most of the forecast area with
breezy north winds and temperatures mainly in the 40s. High
pressure is located across the northern Rockies.

Upper trof continues to shift south and east quickly today, with
skies clearing out early. Pressure gradient relaxes today, but
good mixing will keep breezy northwest winds in place into the
afternoon. High temperatures will be about 10 to 15 degrees cooler
today, in the 50s to lower 60s. High pressure settles across the
are tonight with atmosphere decoupling and winds subsiding. Low
temperatures will be cool, in the 30s for most locations.

Western upper ridge shifts east across the Rockies on Friday with
clear skies and mild temperatures returning. Highs will be in the
upper 60s to lower 70s with lows in the 30s and 40s.

Upper ridge builds into the northern Plains for the weekend, with
sunny skies and very warm temperatures expected. Saturday will see
highs in the 70s, and Sunday could see a few locations in the
lower 80s. Breezy southerly winds are also expected across the
area for the weekend. Upper ridge shifts east of the area late on
Sunday with a large upper low moving into the Pacific Northwest.
This will turn the upper flow pattern to the southwest across the
Northern Plains, and bring increasing chances for showers and
thunderstorms to the area late Sunday into early next week.

As the upper low moves further east Monday and Tuesday, a cold
front will pass through the region and bring a gradual cooldown to
near or slightly below average temperatures for Tuesday and
Wednesday. Latest models have the upper low weakening and lifting
northeast through the Northern Plains. This should produce a daily
chance of showers and storms for the Northern Plains area for
much of next week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1118 AM MDT Thu Apr 26 2018

Mainly VFR conditions expected through the period. Breezy
northwest winds are expected this afternoon.

&&

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

$$

DISCUSSION...15
AVIATION...10



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