Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 212356
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
556 PM CST Tue Nov 21 2017

.UPDATE...
Issued at 540 PM CST Tue Nov 21 2017

Surface High pressure was situated over western and central early
this evening with mainly clear skies and light or diminishing
winds. The surface high will slide southeast tonight. Main issue
this evening will be how far temperatures drop under good
radiational cooling conditions, before a return flow sets up and
temperatures begin to rise in the west after midnight. Will take
another look at temperatures later this evening. Otherwise no
changes other than some minor tweaks to lower cloud cover and
updating latest sensible weather elements.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 141 PM CST Tue Nov 21 2017

A wintry mix far northwest and north central Wednesday morning
highlights the short term forecast.

Cold surface high pressure across the Northern Plains this
afternoon will propagate into the Central and Southern Plains
tonight. A surface warm front will propagate into the Missouri River
Valley between 12-15 UTC Wednesday morning, with an elevated warm
layer aloft with the slope of the warm front extending further
east into north central North Dakota and the James River Valley. A
clipper will propagate along the low level baroclinic zone from
northwest to southeast across the state through the day. The 12
UTC global guidance is further north with this clipper compared to
yesterday. Thus, the potential for a wintry mix of freezing rain,
sleet and snow has also shifted north compared to yesterday, now
across extreme northwest North Dakota and through the north central
along and north of US Highway 2. While QPF amounts are light, even
a small amount of freezing rain will impact travel.

The aforementioned baroclinic zone will lead to a large spread in
forecast highs for Wednesday, only in the 20s across the Turtle
Mountains, to the 50s southwest and south central. Brisk northwest
winds with gusts around 30s kts are forecast across southwest
North Dakota in the wake of the clipper.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 141 PM CST Tue Nov 21 2017

Record highs possible on Thanksgiving, and a very windy
Friday highlight the extended forecast.

The 00 UTC NAEFS 850 mb mean temperatures climb to their 99th
percentiles across much of western North Dakota on Thanksgiving.
With favorable southwesterly winds, the top edge of the 12 UTC
suite forecast envelope for highs is possible across western and
portions of central North Dakota. As southwest winds and greater
mixing will be late to arrive across the James River Valley
through the Turtle Mountains, a large spread in temperatures is
once again expected on Thanksgiving. Highs perhaps around 70 are
forecast southwest, with perhaps only the 40s and 50s for the
James River Valley and Turtle Mountains.

Location....Forecast High...November 23.....Thanksgiving All Time

Dickinson........70...........63 in 1984........65 in 1998
Williston........64...........56 in 2011........56 in 2002
Bismarck.........60...........62 in 2011........62 in 2002
Minot............57...........55 in 1942........57 in 2011

In a setup similar to Monday, Friday looks to be very windy in
the wake of a strong cold front extending from a clipper system
across Manitoba into Ontario. Strong gradient winds with 45-55 kts
to mix in the 800-850mb layer, with steep low level lapse rates
and cold air advection behind the front support the potential for
strong winds across western and central North Dakota on Friday.
This will have to be closely monitored for a possible High Wind
Watch.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 540 PM CST Tue Nov 21 2017

Light winds and VFR conditions this evening. A warm front will
lift into the area and may bring some VFR ceilings (8000ft) near
Williston this evening. Otherwise clouds remain north of the area
tonight. Wednesday low pressure will track along the international
border. Early Wednesday, there may be some low level winds shear
as strong winds aloft overspread the area. Most likely areas for
shear would be KISN and KDIK. Will take a closer look tonight and
possibly add this to the 06z TAFS around the 12-16Z timeframe. VFR
clouds and light precipitation then spread across KISN and KMOT.
Currently only mention of VCSH at KMOT with precipitation mainly
north of these TAF sites. Surface winds shift from south to west
to northwest at all taf sites during the day with the passage of
the low and associated surface front.

&&

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

$$

UPDATE...TWH
SHORT TERM...PA
LONG TERM...PA
AVIATION...TWH



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