Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 052257
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
457 PM CST Mon Dec 5 2016

.UPDATE...
Issued at 453 PM CST Mon Dec 5 2016

Quick update to add Billings and Golden Valley counties to the
Blizzard warning. These counties remain in the deeper snowpack,
compared to the southwest. Area webcams also show significant
blowing and drifting snow.

&&

.SHORT TERM...(Tonight)
Issued at 414 PM CST Mon Dec 5 2016

Headlines have been upgraded to a Blizzard Warning for much of
western and central North Dakota. Blizzard conditions are
occurring in northwest areas, supported well with observations
and public reports of visibilities of a quarter of a mile or less
and winds sustained around 30 mph.

An Upper level trough and an associated surface front were pushing
eastward across North Dakota. Sufficient mid-level lapse rates of 7
C/Km and atmospheric instability, in combination with ample
mid/upper level moisture, were creating a dynamic setup for snowfall
to continue through Tuesday.

The surface low is projected to phase with the upper level low, as
the system scoots north and east today and through the overnight
hours. Chances for snow are expected to linger over central areas
through Tuesday. Northwest winds will also remain strong through
Tuesday with gusts near 50 mph, creating the continued likelihood of
reduced visibilities and dangerous travel conditions.

A Blizzard Warning has been issued for much of western and central
North Dakota. Blizzard headlines have started in the northwest and
will progress eastward this evening and through Tuesday. As of now,
southwest areas remain in a Winter Weather Advisory until 16Z
Tuesday.

.LONG TERM...(Tuesday through Monday)
Issued at 414 PM CST Mon Dec 5 2016

Blizzard conditions are expected across most of western and
central ND late tonight through Tuesday.

The 12 UTC model suite, including the GFS, NAM, and ECMWF, is in
good agreement showing a strong stacked low ejecting to near Grand
Forks by early Tuesday morning. The low is then forecast to move
slowly eastward during the day. Strong northwesterly winds are
forecast behind the low, with mean boundary layer winds near 35
kt and peak speeds at the top of the mixed layer pushing 50 kt.
Stout cold air advection will promote efficient momentum transfer
and wind gusts to 50 mph should easily be achieved, especially
in open/rural areas across central ND late tonight and Tuesday
morning. Guidance is also in agreement showing light to possibly
moderate snow continuing to fall in the cyclonic, "wrap-around"
moisture regime late tonight and Tuesday. Determining the westward
extent of that area of snow is one challenge to the forecast, but
the multi-model consensus is generally on board with it extending
to the Highway 83 corridor. The Baggaley Blowing Snow Model
supports blizzard conditions over a wide expanse of the area
through Tuesday afternoon, especially in rural areas, due to the
snow on the ground and light falling snow. Interrogation of that
model does suggest falling snow will be required to sustain near-
zero visibilities, so the westward extent of "wrap-around" snow
will ultimately be critical. The 12 UTC ECMWF is particularly
robust with higher amounts of snow all the way westward into the
Highway 83 corridor from 09 to 15 UTC, but even the GFS and NAM
simulated enough light snow that we were confident enough to post
a blizzard warning for that area. The fresh snowpack of 4 to 6
inches that fell Monday afternoon in south central ND will also
readily blow and drift.

Thereafter, strong cold air advection will continue to bring
Arctic air into the region the rest of the week. Forecast wind
chills to 25 below zero in multiple periods from Tuesday night
through Friday morning will likely require wind chill advisories
in later forecast releases. Model guidance suggests 500 mb flow
may back more westerly by this weekend, yielding some moderation
in temperatures, but that could come at the expense of more
snowfall occurring along the resultant tightening baroclinic zone.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 453 PM CST Mon Dec 5 2016

Widespread IFR and LIFR conditions are forecast across western
and central ND through Tuesday afternoon due to snow and blowing
snow. Gusty northwest winds to 45 kt in western ND this afternoon
will spread into the central part of the state tonight and then
continue into Tuesday as strong low pressure affects the region.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM CST /4 PM MST/ this afternoon
for NDZ003-011-019>021-034-035-042-045-046.

Blizzard Warning until 6 PM CST /5 PM MST/ Tuesday for NDZ003-
011-019>021-034-035-042-045-046.

Blizzard Warning until 9 AM CST /8 AM MST/ Tuesday for NDZ001-
002-009-010-017-018-031>033.

Winter Storm Warning until midnight CST tonight for NDZ004-005-
012-013-023-025.

Blizzard Warning from midnight tonight to 6 PM CST Tuesday for
NDZ004-005-012-013-022-023-025-036-037-047-050.

Winter Weather Advisory until midnight CST tonight for NDZ022-
036-037-047-050.

Winter Weather Advisory until 11 AM MST Tuesday for NDZ040-041-
043-044.

&&

$$

UPDATE...TWH
SHORT TERM...AC
LONG TERM...CJS
AVIATION...TWH



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