Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 181704
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1104 AM CST Mon Dec 18 2017

.UPDATE...
Issued at 1055 AM CST Mon Dec 18 2017

Current forecast looks ok but raised the chance for rain/snow
though early afternoon across the west. Getting some reports of an
inch of snow across this area already. But with rising Temps there
accumulations should be inhibited.

UPDATE Issued at 818 AM CST Mon Dec 18 2017

Radar shows some virga moving through south central North Dakota
believe some of this will reach the ground in the next hour or two
so extended the chance of rain/snow into the south central this
morning.

UPDATE Issued at 653 AM CST Mon Dec 18 2017

Light radar reflectivities continue to track out of the north
central into northeast ND along a warm front. No ground truth with
this as of yet but a potential for light freezing rain. This will
move out of the forecast area in the next hour.

Another area of concern early this morning is far western ND.
Rain been reported in northeast MT. Although temperatures in
western ND are above freezing, latest road surface temperatures
show readings just at or below freezing. Will need to monitor over
the next hour or so but expect road surface temperatures to rise
above freezing by around 9 AM.

&&

.SHORT TERM...(Today and tonight)
Issued at 351 AM CST Mon Dec 18 2017

Currently, a low pressure system was centered over northern
Manitoba, with a cold front extending westward across the northern
Canadian plains. A mild west/southwest flow south of this cold front
will keep a relatively mild airmass over North Dakota for most of
today. This afternoon the cold front is forecast to enter northern
North Dakota, reaching the South Dakota border by this evening.
Temperatures should reach well into the 40s across southern ND,
mainly along and south of highway 200. The northern tier of counties
should see mid to upper 30s today.

Meanwhile at upper levels, energy impulses moving west-to-east
across the region will provide enough instability for some light
precipitation, mainly across northern North Dakota. Light snow
should spread from northwest across north central ND this morning,
before mixing with and changing over to light rain this afternoon.
As the cold front drops south, the area of rain/snow should also
move south during the afternoon and evening, before tapering off by
midnight. Snowfall amounts of up to an inch are possible across
northern ND, mainly north of US Highway 2.

Breezy conditions are also expected today, especially in
southwestern North Dakota ahead of the cold front, where sustained
winds of 20-25 mph are expected, with gusts to 35 mph possible.

Tonight cold air advection continues with northwest winds remaining
at 10 to 20 mph. Look for lows from the upper teens north to low to
mid 20s south.

.LONG TERM...(Tuesday through Sunday)
Issued at 351 AM CST Mon Dec 18 2017

On Tuesday, arctic air continues to push into the state as a
Canadian high pressure system drops south out of north central
Canada. The high pressure axis slides to the southeast, mainly
moving across the northeast half of North Dakota Tuesday night.
Lows Tuesday night should range from the single digits above zero
in the Turtle Mountains to the lower 20s in southwestern ND.

The main story in the near term is focused on a potent storm system
to affect our area Tuesday night and Wednesday. The upper level
trough of the system moves into the Pacific Northwest Tuesday, digs
south and elongates as it traversed the Rockies Wednesday, reaching
the Desert Southwest and nearly cutting off from the main belt of
the Westerlies on Thursday before it continues as a more open wave
as it heads east into the Great Lakes and Mississippi Valley. In
response, a surface low develops ahead of the upper level trough on
Tuesday/Tuesday night across the Front Range, deepens further
Wednesday over southeast Montana and Wyoming, and continues
developing/moving into the southern plains by Thursday. Light snow
is expected to begin in the west Tuesday evening on the northeastern
side of the advancing storm system, spreading east across the state
later Tuesday night, continuing Wednesday on the northern side of
the system as it deepens and becomes established over Colorado. The
favored area for the most snowfall is along and north of US Highway
2, where 3 to 4 inches of snow is possible. Expected snowfall
amounts decrease to less than an inch along the I-94 corridor and to
the South Dakota border.

In addition to the snow, we should see an increase in winds, first
southeasterly Tuesday night, then becoming northerly on Wednesday as
the arctic air surges into the state. Wind speeds of 15 to 20 mph
should be common from late Tuesday night through Wednesday night.
Drifting snow may become a hazard, if not an inconvenience, across
northern North Dakota on Wednesday.

Thereafter, the focus is on the arctic air that continues to be
reinforced every day or so with another cold front. The cold air and
dangerously low wind chill values should linger at least through
Christmas.

A special weather statement will be re-issued regarding the snow and
cold conditions.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1104 AM CST Mon Dec 18 2017

A cold front will gradually shift from north to south through 00Z
Tuesday. Occasional light snow or light rain along with periods of
mvfr cigs can be expected along and ahead of the cold front.
Following the cold frontal passage, expect a windshift to the west
and northwest with improving cigs to vfr for the remaining TAF
period.

&&

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

$$

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



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