Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 182232
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
223 PM MDT Tue Apr 18 2017

.SHORT TERM...(This Evening Through Wednesday Night)
Issued at 222 PM MDT Tue Apr 18 2017

Southwest flow has developed aloft across the western half of the
CONUS including over the northern plains ahead of a longwave trough
slowly moving onshore the Pac NW coast. A strong shortwave is
crossing the Great Basin at this time with weaker waves downstream
into WY and the CWA. Clouds have increased as the waves have moved
into the region. KUDX radar shows reflectivity aloft moving in from
northeast WY into the Black Hills area. This precip is not reaching
ground...yet...except across parts of the higher Black Hills. Precip
coverage will increase through the night across the region as the
main shortwave moves into the area late tonight. Rain will begin
across southern portions of the CWA...then slide northward Wednesday
morning into the the northeast WY plains...the Black Hills area and
SD plains east of the Hills. This band of rain will sit across the
central CWA through much of the day Wednesday before gradually
decreasing through the afternoon and evening hours. Temps will be
cold enough late tonight for rain to mix with or change to snow
across the higher Black Hills. The ECMWF/NAM/WPC/SREF are all going
with 1 to 4 inches of accumulation while the GFS is the outlier
showing about a foot of snow. Will throw out the GFS and stick with
1-4" with no need for headlines. Total QPF is expected to range from
0.75" to 1.25" across most of the CWA...with some areas possibly
seeing QPF amounts approaching 2". Temps tomorrow will be limited
with the precip and clouds cover...reaching into the 40s to low 50s.

.LONG TERM...(Thursday Through Tuesday)
Issued at 222 PM MDT Tue Apr 18 2017

A brief break from the unsettled weather can be expected on Thursday
before the next system digs southeast from the northern Rockies to
the Central Plains Thursday night and Friday. Latest model runs have
trended back farther south with the track of the system with precip
barely clipping the southwestern portions of the CWA. This solution
also decreases or eliminates snow accumulation that would have
occurred over the Black Hills. This system will exit the region
Friday night, but additional energy in active flow could bring
isolated showers across the area through Saturday. Dry and warm
weather is still anticipated for Sunday before another series of
disturbances brings chances for showers Sunday night into early next
week.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1055 AM MDT Tue Apr 18 2017

A storm system will approach from the west tonight spreading
showers into the area. TSRA possible across the south. Mainly VFR
conditions this afternoon will deteriorate tonight with widespread
MVFR CIGS developing; local LIFR/IFR conditions will occur with
the heaviest precipitation and near the Black Hills where some
snow will occur late.


&&

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

$$

SHORT TERM...13
LONG TERM...13
AVIATION...Johnson



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