Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 221042
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
442 AM MDT Sun Apr 22 2018

.DISCUSSION...(Today Through Saturday)
Issued at 414 AM MDT Sun Apr 22 2018

Upper level analysis has closed low over southeastern Kansas with
ridge axis over Minnesota. Zonal flow across the Pacific Northwest
is pushing a weak upper trof across the northern Plains at the
moment. Skies are mainly clear across the area. At the surface,
high pressure is located across Minnesota, and a weak low and cold
front extend from eastern Montana into central Wyoming.
Temperatures at 4am are in the mid 30s to mid 40s, and winds are
generally out of the south at 10 to 20 mph.

Weak upper ridging will hold on for today, and will allow for
mild and dry conditions to continue. Under mostly sunny skies,
winds will be light and variable, and highs will be in the 60s.
Skies will remain mostly clear overnight, with temperatures
falling into the 30s and 40s.

Strong shortwave will cross the Pacific Northwest late Sunday
night and approach the northern Plains on Monday. Models are
in decent agreement on this system, but there are still some
distinct differences. The GFS is still the outlier in its more
northerly storm track; the Canadian, ECMWF, and NAM show the 700
mb low sliding through northeastern WY and southwestern SD, into
Nebraska. Therefore, highest amounts of forecast QPF remain from
the Black Hills area and north. As usual, the NAM has the most
intense solution of these models, showing quite a bit of snow for
the northern Hills. Current forecast shows a blend of the other
models with QPF amounts ranging from half an inch up to 0.85
inches for the northern half of the CWA. Temperatures will fall
off Monday night for rain to change to snow across western and
northern areas. 1 to 3 inches will be possible across northeast
WY and northwest SD, and up to 6 inches in the northern Hills,
where upslope enhancement will be a factor. Strong pressure rises
will occur over the region late Monday, resulting in gusty
northwesterly winds, mainly in the evening and overnight. Models
still agree on a slower exit of this system, showing precip
lingering into Tuesday morning.

Cool air will linger into Tuesday, with below average highs
expected. The rest of the week will be generally mild and dry,
although another cold front will bring breezy winds and cooler
temperatures for Thursday. Warm and dry conditions are expected
for Friday into next weekend.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1031 PM MDT Sat Apr 21 2018

Localized MVFR/IFR cigs remain possible overnight across portions
of the Black Hills. Elsewhere, VFR conditions are expected through
the TAF period. Winds over northeast WY/northwest SD will shift to
northwesterly overnight as a weak boundary crosses the area.
However, winds will generally become easterly/southeasterly on
Sunday in advance of our next disturbance.

&&

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

$$

DISCUSSION...15
AVIATION...Sherburn


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