Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 190048
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
648 PM CST Sun Feb 18 2018

.UPDATE...
Issued at 643 PM CST Sun Feb 18 2018

Main forecast challenge continues to be the snow development over
southwestern North Dakota. Webcams suggest that some very light
snow has developed over parts of the area, but expect additional
development to occur late tonight into early Monday morning.
Otherwise, mainly quiet conditions expected tonight over remaining
locations.

&&

.SHORT TERM...(This evening through Monday)
Issued at 257 PM CST Sun Feb 18 2018

A period of light snow along and south of I-94 is the main concern
in the short term.

Currently at upper levels, a longwave trough was established over
the Pacific Northwest states, with southwest flow aloft streaming
from the base of the trough northeastward across the northern US
Rockies into the Dakotas. Meanwhile at the surface, low pressure
upstream from the trough was centered over Colorado with an inverted
trough extending from Colorado northeastward towards Minnesota.

Saturday night through this morning, a west-east band of moderate to
heavy snow developed mainly between ND highway 200 and US highway 2,
where reports of 3-5 inches of snow were received. This heavier band
of snow had dissipated this afternoon.

Tonight through Monday night, the west coast upper level trough
continues to dig and expand across California and Nevada, and
another series of upper level impulses streaming northeastward from
the base of the upper level trough expands light to moderate
snowfall from Wyoming and South Dakota and into southern North
Dakota.

The models are depicting the strongest upper level impulses
reaching southwestern ND tonight and expanding across south central
ND on Monday, then the main forcing shifts to south central and
southeastern ND Monday afternoon and night.

Snowfall summary: 1-4 inches of snow along and south of I-94
expected during the 36-hour period beginning tonight and ending
Tuesday morning. Best accumulations of 2-4 inches in the counties
along the SD border.

Timing: tonight through Monday afternoon for the southwest...and
Monday afternoon through early Tuesday morning for the south
central.

A winter weather advisory has been issued for far southwestern ND
(Bowman/Slope/Adams counties) beginning this evening through Monday
afternoon for accumulations of 3-4 inches of snow in this 24-hour
period.

A special weather statement has been issued for south central ND
counties farther east of the advisory to address the snow beginning
mainly Monday afternoon through early Tuesday morning for 3-4 inches
of snow accumulation.

.LONG TERM...(Monday night through Sunday)
Issued at 257 PM CST Sun Feb 18 2018

Tuesday through Sunday, the upper level trough weakens a bit
and merges with the already established Hudson Bay Low, keeping a
cyclonic flow aloft over North Dakota, keeping below average
temperatures in the forecast with some small chances of
light snow off and on throughout the week and into next weekend.
There is a potential for dangerous wind chills Tuesday
night/Wednesday morning.  A slight warmup is possible by the end of
the work week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 643 PM CST Sun Feb 18 2018

MVFR to low end VFR ceilings expected over much of the area
overnight into early Monday morning. Deteriorating conditions
expected Monday, especially over southern areas with snow
developing.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST Monday for NDZ040-043-044.

&&

$$

UPDATE...JJS
SHORT TERM...JV
LONG TERM...JV
AVIATION...JJS



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