Area Forecast Discussion
Issued by NWS Rapid City, SD

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630
FXUS63 KUNR 222319
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
519 PM MDT Sun Oct 22 2017

.DISCUSSION...(This Evening Through Sunday)
Issued at 255 PM MDT Sun Oct 22 2017

Current surface analysis shows low pressure over southeast SK,
with lee-side trough extending southeast across eastern MT and
into the Black Hills area. Canadian cold front extends across
central and western MT. Upper level analysis shows fast near
zonal flow from the Pacific NW to the Northern Plains. Skies are
variably cloudy, with the most clouds over northeast WY to
northwest SD. Temps are in the mid 60s and lower 70s across the
plains, 60s over the Black Hills. Winds are westerly in general,
breezy to windy over portions of northeast WY and northwest SD.

Cooler weather will return for the first part of the week as the
cold front slides through the forecast area tonight. Shortwave
energy with the front will bring isolated to scattered rain showers,
mainly over northeast WY, the Black Hills, and northwest SD during
the evening hours. A tight pressure gradient will develop between
the passing front and high pressure over the Pacific NW. This will
result in windy conditions for Monday. The strongest winds look to
generally be across northwest SD, where some gusts near 60 mph are
likely in the afternoon. However, gusty northwesterly winds can be
expected elsewhere across the plains as well. High wind warnings and
wind advisories have been issued for much of the western and south
central SD plains for Monday. Highs will be in the 50s and lower 60s
across much of the area, with 40s over the higher Black Hills.
Tuesday looks to be slightly warmer for most areas, with highs close
to average.

A brief warmup to above average temperatures can be expected on
Wednesday, ahead of the next cold front. Highs will be in the 70s
across the plains. Medium range models in agreement that the next
front will be stronger than the last couple, with much colder air
settling into the area for late week. Highs will only be in the 30s
and 40s on Thursday and Friday. The best chances for rain/snow
showers will be with the frontal passage later Wednesday night into
Thursday. An upper low is progged to pass north and eventually east
of the area at the end of the week and could bring a few rain/snow
showers at times in some areas, though many areas will likely remain
dry. Strong north-northwest winds are also looking increasingly
likely for Thursday behind the front.

The forecast for next weekend looks cool and mainly dry at this
point. We should see at least a slight warming trend through the
weekend, likely to at least near average on Sunday, though this will
ultimately depend on how quickly the upper level system exits the
region.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Monday Evening)
Issued At 516 PM MDT Sun Oct 22 2017

VFR conditions expected through the period. A cold front will
move through the area tonight bringing gusty northwest winds and
scattered SHRA/ISOLD TS. Wind gusts to 50 knots are possible with
the SHRA over NW SD. Some low level wind shear may occur ahead of
the front. Very windy conds expected most places Monday with gusts
over 50 knots expected on the NW SD plains.

&&

.FIRE WEATHER...
Issued At 255 PM MDT Sun Oct 22 2017

Dry and very windy conditions will develop on Monday behind the
passage of a cold front tonight. Relative humidities will not
reach red flag criteria, 20 to 25 percent across much of the
plains in the afternoon. Very high to extreme grassland fire
danger is expected across the SD plains.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 8 AM MDT /9 AM CDT/ to 6 PM MDT /7 PM CDT/
     Monday for SDZ014-025-026-030-032-042>044-046-047-049-072-
     074.

     High Wind Warning from 8 AM to 6 PM MDT Monday for SDZ001-002-
     012-013-031-073.

WY...None.
&&

$$

DISCUSSION...26
AVIATION...JC
FIRE WEATHER...26



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