Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 211243
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
643 AM CST Mon Jan 21 2019

.UPDATE...
Issued at 643 AM CST Mon Jan 21 2019

Overall, the forecast remains on track. The main adjustments for
this update were to trim back PoPs on the northern edge of the
ongoing snow band and better capture the arrival time of the
second wave of snow later this afternoon into southwest North
Dakota. Also expanded the area of freezing drizzle chances across
southwest into south central North Dakota. RAP soundings continue
to show saturated layer temperatures near and above -10 C with
dry air above and weak upward vertical motion.

&&

.SHORT TERM...(Today and tonight)
Issued at 337 AM CST Mon Jan 21 2019

Accumulating snow is the main forecast concern for the short term
period.

An upper level trough is currently moving into the northern Rockies.
Warm air advection far out ahead of this trough has generated a band
of light to moderate snow across southwest and south central North
Dakota early this morning. This band of snow is forecast to pivot to
the north and east into this afternoon, bringing a general 1 to 2
inches of snow across the southern two thirds of the state.

Model soundings across southwest into far south central North Dakota
show potential for a loss of ice nucleation later this morning, with
saturated layer temperatures near or above -10 C. Therefore, could
see some freezing drizzle across these areas from mid morning to mid
afternoon.

As the warm advective snow band slowly dissipates and moves out of
the area this afternoon, the main upper trough will begin to eject
off the Rockies. This push of energy will provide another round of
snow from southwest into east central North Dakota this evening
through tonight. Far south central and southeast parts of our
forecast area are set to pick up an additional 1 to 3 inches of
snow. This gives storm total snow amounts of 2 to 4 inches across
the southern half of our forecast area, highest in the southeast.

Winds will remain brisk out of the southeast this morning, becoming
northerly this evening. This will cause patchy blowing and drifting
snow, especially along and south of Interstate 94.

.LONG TERM...(Tuesday through Sunday)
Issued at 337 AM CST Mon Jan 21 2019

The main concern for the extended period is a powerful Arctic cold
front moving through Wednesday night into Thursday.

A weak wave is forecast to move from southern Saskatchewan into the
Northern Plains Tuesday evening. Models are not generating any
precipitation associated with this wave, but the 700-300 mb PV
advection fields show some decent forcing. Otherwise, a period of
quiet weather and warming temperatures are expected Tuesday through
Wednesday afternoon.

Attention then quickly turns to the aforementioned Arctic cold
front. The first concern is chances for accumulating snow along and
ahead of the front as it moves through Wednesday evening. Models are
beginning to trend up with QPF, especially over southwest North
Dakota. Not expecting significant accumulations, but a few inches is
not out of the questions. The likely bigger concern will be the
strong winds and subsequent blowing snow that develop Wednesday
night into Thursday afternoon. Many signals are emerging for a
potential higher end event: very strong pressure rises, strong cold
air advection, and steep low-level lapse rates. Mixing layer winds
are currently forecast around 30 to 40 kts, and these tend to be
under done in these scenarios. Given numerous rounds of fluffy snow
that should not be crusted over, in addition to the potential for
snow falling as the strong winds arrive, we could be looking at
widespread blowing snow with significant visibility reductions.

Another concern will be the bitterly cold air that moves in behind
the front. Temperatures will begin falling Wednesday night and
continue to fall throughout the day Thursday, with daytime highs
occurring in the morning. Much of western and central North Dakota
will see temperatures plummet below zero early Thursday morning,
with wind chill values as low as -40.

A progressive northwest flow pattern will remain in place through
the remainder of the extended period, with numerous clipper systems
bringing chances for snow and brisk winds. Expect temperatures to
remain below normal overall, despite a warmer day or two mixed in.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 539 AM CST Mon Jan 21 2019

MVFR ceilings are expected for most areas through the forecast
period. Ceilings have yet to drop at KISN, but think this should
occur by the afternoon. Periods of light snow will affect the
southern half of ND today into tonight, reducing visibility to IFR
levels at times. Expect southeast winds around 10-15 kts this
morning, becoming a bit lighter and turning to the northwest this
afternoon into tonight.


&&

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

$$

UPDATE...Hollan
SHORT TERM...Hollan
LONG TERM...Hollan
AVIATION...Hollan


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