Area Forecast Discussion
Issued by NWS Rapid City, SD

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494
FXUS63 KUNR 192026
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
226 PM MDT Fri May 19 2017

.DISCUSSION...(This Evening Through Friday)
Issued at 225 PM MDT Fri May 19 2017

Deep closed low over the Rockies continues to slowly shift NE,
ejecting small impulses in the processes. Currently, the region is
under a lull of weak forcing as this morning`s wave has weakened
and exited. Just some light upslope showers is lingering with some
light rain from the next impulse affecting far SW SD. Expect
isolated to sct showers this afternoon, best chances around the
Black Hills/SW SD. Drier air will continue to wrap into the
backside of the system with the next main lobe of ascent shifting
into the central plains tonight. This will support a band of
strong FGEN centered mainly over scentral SD and east. Mainly rain
is expected at first, however thermal fields will be cold enough
for a mix or changeover to snow late, best chance into NE. Hence,
some light accums are possible across scentral SD. Rain will
linger over the far eastern zones into Sat afternoon with diurnal
instability possibly supporting sct showers over the
central/southern Black Hills in the afternoon. Cold temps will
remain with lows generally in the 30s (20s Black Hills). However,
clouds will hang on most if not all areas and will limit temp
falls below freezing on most if not all of the plains. Hence, will
not issue any freeze/frost headlines with weak radiational
cooling setup.

Upper low will slowly shift east however it will remain close
enough into early next week to support shower/ts chances Sun and
esp Monday. Phasing NW impulse will push through the region both
days, the strongest being Monday. Enough instability will be
present both days to support TS.

Deep layer ridging expected through most of the remainder of the
week. This will bring much warmer weather and dry conds to the
region. Models continue to support NW CONUS troughing by the end
of the week with chances for shra/ts returning to the forecast by
then.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1145 AM MDT Fri May 19 2017

MVFR conditions in low clouds and light rain will
gradually improve to VFR this evening, except for areas of south
central SD where chances for rain increase overnight. IFR conditions
in light snow over parts of the Black Hills will also improve this
evening.


&&

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

$$

DISCUSSION...JC
AVIATION...Pojorlie



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