Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 160319
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
919 PM CST Mon Jan 15 2018

.UPDATE...
Issued at 918 PM CST Mon Jan 15 2018

Lowered temperatures about 3 to 5 degrees west and south central
based on current trends. Otherwise forecast looks ok.

UPDATE Issued at 604 PM CST Mon Jan 15 2018

Arctic High pressure will build into the region tonight. All
indications are a cold night is in ahead. Will watch for any
rapidly falling temperatures that would indicate min temperatures
would need to be adjusted down. So far so good, but with the
center of the high southeast of south central North Dakota, the
climatology predicts this area, in the south central and
southeast would be the coldest spot in the state. That is where
the current min temperatures are coldest so will keep the
forecast going.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 311 PM CST Mon Jan 15 2018

Dangerous wind chills remain the highlight through Tuesday morning.

Latest water vapor imagery loop shows a closed upper low spinning
over southeast Minnesota, and a narrow but sharp upper ridge axis
was positioned over central Alberta. The resultant upper flow
through North Dakota is a strong north to northeast flow. At the
surface, a 1054mb high pressure was located over Sidney, Montana
producing sunny conditions for all of western/central North Dakota
except within the James River Valley. The Snow/Ice GOES16 channel
depicts these low clouds rather well above the snowpack, stretching
from Carrington to Medina, and south into Ashley. BUFKIT soundings
continue to show the high 925mb relative humidity/moisture thinning
with time through 00z Tuesday, as the low level north to northeasterly
winds push these lower clouds a bit farther west into drier air.
The pressure gradient is strongest within the James River Valley,
with sustained winds in the 20kt to 25kt range. Webcams continue
to show drifting snow across the highways this afternoon, so areas
of blowing snow have been maintained in the gridded forecast data
through 00z Tuesday. Wind chills in some areas have warmed above
advisory and warning criteria, but will quickly return

For tonight, the surface high slides southeast into central South
Dakota by 12z/6am CST Tuesday. Although winds will diminish with
the high passing through, radiational cooling will be maximized
with overnight lows ranging between 18 to 28 below zero, and wind
chills to 45 below zero. Current wind chill advisory far west, and
wind chill warning elsewhere is in good standing and will continue
through Tuesday morning.

Low level warm air advection develops with winds becoming southwest
and southerly Tuesday as the surface high shifts farther away.
Plenty of sunshine Tuesday with highs in the upper teens west to
single digits across most of central North Dakota.

.LONG TERM...(Tuesday night through Monday)
Issued at 311 PM CST Mon Jan 15 2018

Warming trend Wednesday through Friday, then turning colder again
Saturday through Monday. With temperatures rising to above
freezing during the day and then below freezing at night, expect
icy conditions each evening/night and through the early morning
hours Wednesday through Friday.

Water vapor imagery shows a shortwave trough near 130W/44N. This
peels away from the main upper trough stretching from the Gulf of
Alaska into the eastern Pacific. This shortwave nudges into the
sharp upper ridge Tuesday/Tuesday night as our upper level flow
becomes westerly Wednesday. The shortwave develops into a compact
closed low Wednesday which is forecast to slide across southern
Saskatchewan and Manitoba, before shifting into northeast ND and
northern Minnesota Wednesday night. The operational NAM/GFS/EC now
have a similar path as mentioned above, with the GFS showing some
light snow over the Turtle Mountains Wednesday night. The GFS
ensemble mean and SREF show a track slightly farther south,
crossing more into north central ND. Will watch this closely as
any shift south like the SREF and GFS Ensemble Mean will likely
bring any precipitation threat south of the border. Right now, the
gridded forecast remains dry with the southern edge of
precipitation north of the border and just east of the Turtle
Mountains. With a cold frontal passage associated with this
shortwave Wednesday, westerly boundary layer winds will evolve and
become well mixed, especially in northern ND. This will allow for
breezy conditions/downslope flow, along with warm air aloft
mixing down to the surface. Highs Wednesday will be mostly in the
30s. Not expecting blowing/drifting snow at this time, as the
current snowpack should exhibit a stronger crust. As is usually
the case, melting during the day will re-freeze at night and
produce icy conditions. Despite melting and increased boundary
layer moisture, the lower layers of the atmosphere should remain
unstable/mixy to inhibit any widespread fog potential.

A brief period of cold air advection Wednesday night into Thursday
morning, then warm air advection quickly returns Thursday afternoon
as a transitory ridge slides through. This is ahead of our next
shortwave and associated cold front slated for Thursday night
through Friday morning. This will be followed up by a secondary
cold frontal passage Friday night into Saturday. Upper level winds
will transition from quasi-zonal Wednesday through Friday, to
northwesterly Saturday through Monday, resulting in cold air
advection/colder temperatures.

In terms of precipitation, a chance of snow will accompany the
Thursday night cold front across the west, transitioning to a
chance of rain/snow Friday central. Liquid amounts are less than
one tenth of an inch and fairly sparse. The second frontal passage
Friday night into Saturday is forecast to pass through dry.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 604 PM CST Mon Jan 15 2018

Arctic high pressure will build over the state tonight. VFR
expected for the 00Z TAFs.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Wind Chill Warning until noon CST /11 AM MST/ Tuesday for
NDZ002>005-010>013-018>023-025-033>037-041-042-045>048-050-051.

Wind Chill Advisory until noon CST /11 AM MST/ Tuesday for
NDZ001-009-017-031-032-040-043-044.

&&

$$

UPDATE...WAA
SHORT TERM...KS
LONG TERM...KS
AVIATION...WAA


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