Area Forecast Discussion
Issued by NWS Rapid City, SD

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633
FXUS63 KUNR 291936
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
136 PM MDT Mon May 29 2017

.DISCUSSION...(This Evening Through Monday)
Issued at 134 PM MDT Mon May 29 2017

19z surface analysis had low over central ON with upper low
spinning just north of Lake Superior. Cyclonic flow assisting
cellular CU field over eastern half of CWA. Quiet weather.

Tonight, upper low moves northeast as upper ridge builds over the
Rockies. 1024mb surface high centered over southern SK with ridge
axis through the CWA. Clearing skies and light winds will allow
upstream Td/s in the 30s to be realized for overnight lows over much
of the CWA. Frost looks like a good bet on the northwest SD plains,
so will hoist headlines. Few low-lying spots might even drop 0C, but
not widespread or low enough for freeze warning. These minimums
are lower than guidance.

Tuesday, upper ridge and subsidence bring a pleasant day to the area
with temperatures near guidance.

Wednesday, upper ridge moves toward the plains and weaken with a weak
shortwave forecast to move through during peak heating. Decent return
flow is expected as surface high moves into the OH valley. 1-2KJ/kg
MLCAPE forecast in a narrow tongue from the Black Hills into NE
with 15-20m/s 0-6km bulk shear. If a shortwave actually moves through,
25-50 MLCIN combined with terrain should pop TS. Supercells would
be possible with very slow movement, possibly bring a few severe
reports. Temperatures will be noticeably warmer.

Thursday, upper ridge overhead with convection likely limited to the
Black Hills if any. Temperatures will be summer-like.

Friday through Monday, mostly progressive split flow will bring a
series of disturbances through the CWA with convection possible each
day. Friday will be slightly above normal.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1111 AM MDT Mon May 29 2017

VFR conditions are expected through Tuesday morning. Northwest winds
will be breezy this afternoon, diminishing by early evening.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Frost Advisory from 2 AM to 8 AM MDT Tuesday for SDZ001-002-
     012>014-031-073.

WY...None.
&&

$$

DISCUSSION...Helgeson
AVIATION...15



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