Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 180852

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
252 AM MDT Wed Oct 18 2017

.DISCUSSION...(Today Through Tuesday)
Issued at 249 AM MDT Wed Oct 18 2017

Canadian upper trough is flattening the upper ridge as
it moves eastward, pushing clouds into the region. The associated
surface trough is draped over the northern plains, with the cold
front currently moving through MT and western ND. Winds across the
CWA are generally westerly 10-15 kts, and temperatures at 2 AM are
still in the 50s, with even some 60s and 70s across the northeastern

The cold front will quickly cross the Dakotas this morning,
producing gusty northwesterly winds across the SD plains. Winds will
weaken this afternoon. Dry weather will continue, and highs today
will be in the 60s to lower 70s.

Upper ridge will rebuild for the end of the week, and southwesterly
flow will help temperatures reach the 70s and 80s. The next upper
trough will move into the region Friday night, bringing chances for
light rain/snow showers into Saturday. Some instability across south
central SD may allow for a few thunderstorms there. Saturday will be
breezy with highs cooling to the 50s and lower 60s. Sunday will be a
little warmer, but the models have flip-flopped on precip chances:
now the ECMWF shows a secondary wave producing a few showers Sunday
night, while the GFS keeps the wave to the north. Nonetheless, both
models agree on another large ridge building over the western CONUS
for next week.


.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 1024 PM MDT Tue Oct 17 2017

VFR conditions will continue tonight and on Wednesday. Areas of
LLWS are expected over far northeastern Wyoming from 06Z-10Z and
over much of western and central South Dakota from 07Z-13Z tonight
into Wednesday morning.


Issued At 249 AM MDT Wed Oct 18 2017

Minimum relative humidity values will reach 15 to
25% today. Although breezy winds are expected across the western SD
plains this morning, winds are expected to diminish this afternoon
by the time RH dips near 15%. Therefore, will not issue headlines
for today. However, min RH less than 15% and gusty southwesterly
winds across parts of northeastern WY on Thursday may result in
critical fire weather conditions. Have issued a Fire Weather Watch
for Campbell County for Thursday afternoon.


WY...Fire Weather Watch Thursday afternoon for WYZ259-297.



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