Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 130902
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
302 AM MDT Wed Sep 13 2017

.DISCUSSION...(Today Through Tuesday)
Issued at 235 AM MDT Wed Sep 13 2017

Water vapor shows upper wave responsible for yesterdays storms
across eastern SD. Upstream trof is working into the Pacific
Northwest with disturbed southwest flow extending into the
Northern Rockies. Associated cold front at the surface is pushing
into northern MT.

Another very warm day expected today with thermal ridge overhead.
Afternoon heating combined with approaching upper level energy
embedded in the southwest flow aloft will lead to more
thunderstorm development, especially from the Black Hills
northward near and to the north of a developing surface low. As
with yesterday, heavy rainfall a possibility with precipitable
waters up to 150% of normal. Gusty winds and small hail also a
possibility, but overall severe threat is low.

Cold front will then work through tonight, with thunderstorm
activity shifting east of the region by morning.

Cooler air will continue to flow into the Northern Plains the next
few days as upper trof pushes into the Northern Rockies by the
beginning of the weekend. Precipitation chances will increase
significantly, especially in the Thursday and Friday time frame as
strong wave is ejected northeastward around the upper trof,
bringing in some much needed widespread rains to much of the cwfa.

Drier and warmer weather then expected to return by the end of the
weekend into early next week as upper ridge rebounds through the
Plains.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 235 AM MDT Wed Sep 13 2017

Outside of MVFR visibilities in smoke mainly across northeast WY,
VFR conditions expected through period. Isolated to scattered
TSRA will develop over the region Wednesday afternoon with local
MVFR conditions.

&&

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

$$

DISCUSSION...Johnson
AVIATION...15



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