Area Forecast Discussion
Issued by NWS Bismarck, ND

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147
FXUS63 KBIS 200926
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
326 AM CST Mon Nov 20 2017

.SHORT TERM...(Today and tonight)
Issued at 325 AM CST Mon Nov 20 2017

Warmer and windy today...then cold and windy tonight with low
wind chills are the highlights in the short term.

Currently, a clipper low pressure system was centered over
southwestern Saskatchewan. Southerly winds were established ahead of
the system over the eastern Dakotas, where temperatures were mainly
in the 20-30F range. Meanwhile southwesterly winds in the warm
sector of the clipper were occurring over Montana/Wyoming/western
Dakotas, where temperatures were mainly in the 30s and 40s.

The clipper is forecast to move east across southern Manitoba into
southwestern Ontario by this evening, continuing across southern
Ontario tonight. The warm sector of the system will dominate
southern ND today, with southwesterly winds becoming westerly and
increasing to 15 to 30 mph this afternoon. Across northern ND, the
warm sector of the system will be replaced by the cold sector this
afternoon as the trailing cold front of the clipper enters
northwestern ND around noon and begins to sweep south/southeast
across the state this afternoon, with winds becoming northwesterly
at 20 to 30 mph ushering in cold advection. Temperatures should
climb into the 50s across southern ND this afternoon. Across
northern ND, temperatures will climb into the upper 30s and 40s by
around noon...but temps will be steady or falling through the
afternoon. By sunset today, temperatures should be in the 30s north
to 40s south.

Tonight the northwest winds will continue to bring much colder air
into the state. We are looking at overnight lows from the single
digits above zero across northern counties, to lower teens across
the southwest and south central. 3-hour pressure rises behind the
cold front are forecast to be around 6-7 mb. Bufkit soundings
indicate momentum transfer from h850 to the surface, tapping into
northwest winds of 40-50 knots at the h850 level - especially from
the north central through the James Valley (Minot to Jamestown
soundings). A wind advisory may be needed for this area. We expect
northwest winds of 25 to 35 mph with gusts to near 50 mph possible north
central through the James Valley. Farther south and west, expect
northwest winds of 20 to 30 mph with possible gusts as high as 40 mph.

The combination of these strong winds and low temperatures will
result in wind chills of zero to 10 below in southern ND and from 10
to 20 below zero across northern ND. Now is the time to break out
the hats, hoods, and gloves if you haven`t already this season.

.LONG TERM...(Tuesday through Sunday)
Issued at 325 AM CST Mon Nov 20 2017

Holiday travel impacts are possible Wednesday as confidence
increases for a wintry mix of precipitation across northwest and
central ND. On Friday and Saturday after Thanksgiving the main
concern is strong winds.

Tuesday will be cold as the arctic high pressure behind Monday
night`s cold front pushes into the state, with its axis extending
from southern Saskatchewan to the central Dakotas. Expect high
temperatures only from the teens north to 20s south, northwest winds
at 10 to 20 mph, and resulting afternoon wind chills from zero to 15
above.

Wednesday we will see the approach of another low pressure system
emerging from the northern US Rockies, moving southeast across
Montana, southwestern ND, and across SD. The best forcing with this
system will be on its northern and eastern side, resulting in a
northwest-to-southeast oriented area (southeast Saskatchewan across
northwest/north central ND into the James Valley) where the
strongest baroclinic zone should set up, and where chances of
accumulating precipitation is most likely. Precipitation is expected
to begin around sunrise in the west and expand eastward. At first,
precipitation should be in the form of light snow, then change to a
mix of sleet and freezing rain from west to east as the warm air
begins moving into the state from the west. Surface temperatures in
southwestern ND should be warm enough by late morning for any
precipitation to be in the form of light rain. The wintry mix of
precipitation shifts to the eastern half of the state Wednesday
afternoon. The model runs have been consistent regarding up to
around 0.05 water equivalent precip expected across northwest into
north central ND.

On Wednesday the area of most concern for freezing rain and sleet is
over northwestern ND, namely Divide, Williams, Mountrail and Burke
counties. Even though farther south and east the threat is less, it
is good to remember that it doesn`t take much of an accumulation of
freezing rain/sleet to result in hazardous travel conditions. Snow
accumulations are not of a great concern, with 1/2 inch or less of
snow expected across the northwest and north central. The takeaway
is that the likelihood/confidence of slick roads Wednesday continue
to increase as model runs are consistent with this scenario. There
will be a large temperature gradient across the state with highs in
the 20s and 30s over the northeast half of the state to the 50s over
much of southwestern ND.

Weather for Thanksgiving looks fairly quiet. The large temperature
gradient continues, with highs from 25 in northeastern ND to the
lower 60s in the far southwest.

Another strong Alberta clipper system moves out of Alberta Thursday
night and sweeping southeast across southern Canada on Friday.
Today`s model runs indicate very strong winds Friday into Saturday,
impacting travel for the Thanksgiving weekend. The good news is that
most of the precipitation with this system should be to our north
and east.

Sunday looks quiet for a better ending of the holiday weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1231 AM CST Mon Nov 20 2017

VFR conditions expected through the 06Z TAF period. High clouds
tonight and Monday morning with low pressure to our north. Light
south to southwest winds expected. A cold front moves through Monday
afternoon with winds shifting west to northwest and becoming gusty.
Decided to add LLWS late tonight into Monday morning for KISN and
KMOT due to light surface winds and increasing westerly winds aloft.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...JV
LONG TERM...JV
AVIATION...TWH



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