Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 230622
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1222 AM CST Thu Nov 23 2017

.UPDATE...
Issued at 1220 AM CST Thu Nov 23 2017

Currently, there is a northwest-to-southeast boundary across ND
separating cooler air to the northeast and the warmer air to the
southwest. This boundary extended from roughly Divide county in the
northwest corner to near Minot to Harvey and the James Valley.  Low
clouds had expanded in the cool sector from east of Minot to
Jamestown.

The main concern this update is the threat of expanding fog - and
possible dense fog.

Visibility was down to zero at Estevan in southeastern Saskatchewan.
Latest iterations of high res models indicate the fog expanding.
However, those same models are indicating fog across 4 northwestern
ND counties at 10pm/11pm, and there was no reported fog at that
time. Since then, there were a couple of social media reports of fog
in Divide and Renville counties. Instead of mentioning "patchy" fog,
will mention "areas" of fog for widespread nature of expected fog
development across northern ND and into the James River Valley. Will
not yet mention dense fog (visibility 1/4 mile or less). Re-issued
the special weather statement to address this possibility.

The threat of fog should wane from west to east slowly this morning
as the push of warm air from the west allows the aforementioned NW-
to-SE boundary moves east this morning.

UPDATE Issued at 924 PM CST Wed Nov 22 2017

Starting to see signs of dense fog forming in Saskatchewan that
may work its way southeast along the edge of the cool air. The
stretch from Burke southeast through northern Ward then north
into Bottineau appears to be the best chance for dense fog. Will
issue a special weather statement at this time then evaluate
the need for any advisories later this evening in this area.

UPDATE Issued at 616 PM CST Wed Nov 22 2017

Main concerns for this update include the stratus clouds sliding
southeast through North Central North Dakota early this evening.
Updated the sky condition to bring the clouds through a Minot to
Jamestown later tonight but remain north of and east of a Bismarck
to Williston line. Used the latest run of the HRRR for this.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 227 PM CST Wed Nov 22 2017

Fog potential tonight into Thursday morning, and possible all
time record highs for Thanksgiving highlight the short term
forecast.

The 19-20 UTC RAP/HRRR favor the potential development of fog
across central North Dakota on the cool side of the low level
baroclinic zone. Also added a mention of patchy fog for the
Missouri River Valley above Lake Sakakawea and also most of
northwest North Dakota.

For Thanksgiving, record highs are forecast for many locations
across western and central North Dakota with an anomalous warm
airmass characterized by 850mb mean temperatures on the 12 UTC
NAEFS around their 97.5-99th percentiles. With favorable
southwesterly winds for warming, the top edge of the forecast
envelope is favored for most areas for highs. The one caveat will
be how long stratus and fog is able to hold across the north
central through the James River Valley and its associated impact
on forecast highs.

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

Dickinson........71...........63 in 1984........65 in 1998
Williston........67...........56 in 2011........56 in 2002
Bismarck.........65...........62 in 2011........62 in 2002
Minot............61...........55 in 1942........57 in 2011
Jamestown........54...........59 in 1942........56 in 2011

.LONG TERM...(Thursday night through Wednesday)
Issued at 227 PM CST Wed Nov 22 2017

A windy Friday and a potential rain/snow mix Monday into Tuesday
highlight the extended forecast.

The 12 UTC global suite is in agreement on a cold front
propagating across western and central North Dakota Thursday
night. Strong winds behind the cold front are favored, especially
Friday morning and into the afternoon, when isallobaric forcing is
greatest. 45-55kts to mix in the 800-850mb layer suggest that wind
headlines are possible. However, the window for high wind warning
criteria gusts is small. As has been the case, a few sites may
sporadically reach warning criteria Friday morning with most sites
in advisory criteria (sub 50kt gusts).

For early next week, the 12 UTC suite diverges on how the wave
arriving onto the Pacific Northwest coast Sunday into Monday
evolves into the Northern and Central Plains Monday into Tuesday.
While there is a chance for a rain and snow mix for western and
central North Dakota, confidence in any one solution is low.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1220 AM CST Thu Nov 23 2017

Main hazards and impacts to aviation include MVFR to IFR
conditions associated with a stratus deck and some fog forecast to
move through a KMOT-KJMS line this morning. Main concern is whether
the fog will become dense in widespread areas to include KMOT or
KJMS. Estevan reporting zero visibility...but that is the only
location as of TAF issuance time. Conditions becoming VFR after 12-
15Z Thursday.

VFR at KISN-KDIK-KBIS.

&&

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

$$

UPDATE...JV
SHORT TERM...PA
LONG TERM...PA
AVIATION...JV


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