Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 172355
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
555 PM CST Sun Dec 17 2017

.UPDATE...
Issued at 547 PM CST Sun Dec 17 2017

Little change outside of observed trends through 23 UTC as a mild
overnight is expected behind a warm front across western North
Dakota early this evening that will propagate east through the
night.

Focus remains on snow and cold impacts beginning tomorrow, and
continuing right on through the Christmas Holiday. Will likely
issue an SPS this evening to message confidence and summarize the
possible impacts.

&&

.SHORT TERM...(This evening through Monday)
Issued at 309 PM CST Sun Dec 17 2017

Late tonight/early Monday morning a Canadian cold front will begin
a southward descent into ND, progressing across the state through
Monday. The proceeding warm front will make for a mild Monday,
particularly in central and southern areas where high temperatures
are expected to climb into the mid/upper 40s. Forcing with this
system remains concentrated across the north, where the best
chances for precipitation will be. Though we could see some
precipitation track with the cold front as it drops south through
the forecast area. The 12Z model suite is indicating higher QPF
then previous model runs. Chances for precipitation were increased
in the forecast though overall accumulations still look to be
light. Snowfall amounts of a few tenths are forecast with pockets
of 1-2 inches possible in northern areas. Mostly snow is forecast
for the morning with chances transitioning to rain and snow late
morning/early afternoon.

Breezy conditions are also expected Monday though disagreement
within the model blend and guidance continues to create uncertainty
as to how strong winds may become. Though the 12Z guidance is
indicating momentum transfer is possible with phasing between
surface and 850MB winds and steep mid/upper level lapse rates, opted
to go with the model blend in the forecast. The model blend does
highlight southwest and south central areas with breezy conditions
which is also where ingredients align within the guidance for the
potential for gusty conditions with gusts around 40mph.

.LONG TERM...(Monday night through Sunday)
Issued at 309 PM CST Sun Dec 17 2017

Noticeably colder air is expected to spill into the state Monday
night and Tuesday. Late Tuesday night through Thursday will be a
transition period as an upper level trough moves onto the West
Coast and then drops into the Desert southwest. The strongest
synoptic scale forcing will track to the south of our area, with
the upper low, but modest synoptic scale forcing will still exist
over the area ahead of a northern stream trough. This will combine
with a period of decent warm advection associated with a strong
baroclinic zone that moves across the northern plains Tuesday
night and Wednesday. Models continue to wobble on the placement of
precipitation with the system. Latest runs keep higher amounts in
the north Wednesday, with a southward shift in precipitation
Wednesday night into Thursday. No matter where the snow ends up,
at this time it looks like we can be assured of a blast of Arctic
air, resulting in dangerously cold wind chill values, late in the
forecast period, lingering at least through Christmas.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 547 PM CST Sun Dec 17 2017

VFR conditions are forecast tonight across western and central
North Dakota. However, MVFR/IFR conditions in snow and stratus will
develop Monday morning across northwest and north central North
Dakota, including KISN/KMOT. Rain may mix with the snow by mid
day and through the afternoon. MVFR stratus may build south into
KDIK/KBIS/KJMS during the afternoon. Strong westerly winds with
gusts to 30kts are expected across southwest North Dakota Monday
afternoon.

&&

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

$$

UPDATE...PA
AVIATION...PA


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