Area Forecast Discussion
Issued by NWS Rapid City, SD

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531
FXUS63 KUNR 291713
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1113 AM MDT Mon May 29 2017

.DISCUSSION...(Today Through Sunday)
Issued at 224 AM MDT Mon May 29 2017

Closed low over southern Canada will slowly shift east through
Tues, with sfc ridging expected over the Northern Plains. This
will support dry weather and a slow warming as the western NOAM
ridge slowly shifts east per Pac NW troughing. Forecast models are
trending toward keeping the bulk of mean troughing across
southern Canada later this week although a stronger impulse will
eject out of the Pac NW trough in the Fri time period, bringing
the best chance for precip to the FA in the period (although
certainly not widespread).

Dry weather can be expected through Tues and most places Wed,
with a slow warming trend under shortwave ridging. Today will be
the coolest day of the week as the influence of the retreating
closed low persist, along with breezy NW winds (strongest today).
Dry air in place will allow temps to fall into the 30s at some
places on the plains both tonight and Tues night. Weak impulse
will pass through the region later Wed with convection possibly
developing over the BH in the afternoon. This will all hinge on
the amount of ll moisture in place per return flow and the degree
of capping aloft, which looks moderate. Mean CAPE solutions are
progged around 1000-1500 J/KG from the BH SE, so if TS do develop,
isolated severe TS would be possible. Convection chances will
shift east across the se third Wed night with a LLJ and elevated
instability. Otherwise, forecast models continue to vary on exact
details per the evolution/progression of upper level flow toward
the weekend given blocking potential over much of Canada. Friday
continues to be progged as the best day for precip chances given
strong consensus for an advecting shortwave trough with decent
moisture and resulting CAPE. This system will support a weak cold
front into the region for the weekend, knocking temps back down a
few degrees.

&&

.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...None.
WY...None.
&&

$$

DISCUSSION...JC
AVIATION...15



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