Area Forecast Discussion
Issued by NWS Rapid City, SD

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172
FXUS63 KUNR 221721
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1021 AM MST Wed Nov 22 2017

.DISCUSSION...(Today Through Tuesday)
Issued at 248 AM MST Wed Nov 22 2017

Water vapor shows highly amplified upper ridge over the western
CONUS, with ridge topping wave over southern Canada pushing into
the Northern Plains. At the surface, lee trof is advancing into
eastern MT/WY. Fairly widespread temp range early this morning
from west to east across the cwfa with staunch warm advection
pushing into NE WY and the Black Hills.

Surface low associated with ridge topping upper wave will push
through ND today with gusty westerly winds spreading much warmer
air through the region. Thermal profiles along with downslope flow
will push temps well into the 60s today, slightly cooler in the
Hills. Mild downslope flow will continue tonight.

On Thanksgiving, upper ridge axis will move into the Northern
Plains with even warmer temps expected, 70s on the SD plains.
Record highs in the Rapid City area are in the upper 60s so expect
some records to be set.

Substantial northern stream trof will work through the Northern
Plains on Friday. 850mb winds will increase to 40-50kts with good
mixing behind frontal boundary likely pushing surface winds into
the advisory range on the SD plains. Little moisture to work with
so any pcpn should be light.

Upper ridge then rebuilds over the weekend into Monday with
possibly some more record highs on Sunday or Monday. Dry
conditions expected. An even more significant trof is expected to
move through on Tuesday with better chances for precipitation.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Thursday)
Issued At 1021 AM MST Wed Nov 22 2017

VFR conditions will continue through the forecast period. West to
northwest winds at 15-25 kt are expected this afternoon.

&&

.FIRE WEATHER...
Issued at 248 AM MST Wed Nov 22 2017

Much warmer and drier air will work back into the region today and
tomorrow. Although relative humidity is not expected to be
critically low (mostly greater than 20 percent), gusty westerly
winds today will push grassland fire danger into the very high
category on the SD plains. Less wind on Thanksgiving should lower
the fire danger a bit. Gusty northwest winds on Friday along with
continued low relative humidity will likely elevate fire wx
conditions once agin. Mild and dry conditions are expected
through the weekend into Monday.

&&

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

$$

DISCUSSION...Johnson
AVIATION...Eagan
FIRE WEATHER...Johnson



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