Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 280650
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1250 AM CST Mon Nov 28 2016

.UPDATE...

Issued at 1250 AM CST Mon Nov 28 2016

Inherited forecast is mainly on track. I did increase winds Monday
night into Tuesday. We start to see pressure rises develop west
into central Monday night along with an increase in gradient
forcing, which continues Tuesday. 1000-850mb geostrophic winds
range from 50-60KTs as well during this time frame.


UPDATE Issued at 933 PM CST Sun Nov 27 2016

No significant changes with this update. Based upon trends in the
12-00 UTC global suites and the high resolution iterations through
02 UTC, have increased the wording to isolated areas of 15 inches
of storm total snowfall by Wednesday evening. This is in line with
the WPC afternoon forecast. Through 0330 UTC precipitation per
reports and webcams is transitioning from rain through sleet and
now snow in Glen Ullin, New Salem and Bismarck. This is generally
on time with the previous forecast thinking of change over.

UPDATE Issued at 647 PM CST Sun Nov 27 2016

As of 0045 UTC...rain is the predominant precipitation type across
south central North Dakota. Road temperatures are holding in the
34-36 degree range. Thus, at the time the freezing rain potential
seems somewhat lower given the road temperatures expected take a
few more hours at least to cool to freezing. However, by that time
across the south central, the 22-23 UTC RAP and HRRR suggest
precipitation is expected to begin its transition to mostly snow
in the 04-06 UTC timeframe. A mix is favored through the night and
and through much of Monday across the James River Valley. Given a
slightly quicker onset of precipitation, did adjust the Winter
Storm Warning start time to 01 UTC for south central North Dakota.

&&

.SHORT TERM...(This evening through Monday Morning)
Issued at 236 PM CST Sun Nov 27 2016

A major winter storm will impact western and central North Dakota
beginning tonight.

A negatively tilted upper level trough will swing into the
Northern Plains tonight. This will induce rapid cyclogenesis over
the central and northern plains with a 975-980MB surface low
situated somewhere near the ND/SD/MN border by 6 AM Monday. Ahead
of this, abundant moisture will stream into the eastern Dakotas,
with strong forcing from the leading shortwave inducing
precipitation over the James River Valley as early as this
evening, but certainly by midnight tonight.

As the system deepens and becomes stacked tonight, a well defined
trowal develops, spreading precipitation westward into central and
eventually western ND by Monday morning. Models continue to
indicate a brief period of warmer temperatures aloft and the
potential for freezing rain and sleet over portions of the James
River Valley this evening. Temperatures will remain near the
critical freezing threshold for much of the overnight and daytime
hours of Monday across the James Vally. Eventually colder air will
advect in and change the rain/freezing rain to all snow by Monday
night. For these areas a Winter Weather Advisory has been issued
to highlight the potential for freezing rain tonight and
accumulating snow tomorrow through Wednesday. Due to the delay in
switching over to snow, portions of Foster, Stutsman, LaMoure and
Dickey Counties will see less snow than locations further west.

.LONG TERM...(Monday through Saturday) Issued at 236 PM CST Sun
Nov 27 2016

Deterministic and ensemble model guidance have come into pretty
good agreement in the evolution of this storm. The deep low near
the ND/SD/MN border Monday morning moves very little through
Tuesday morning. The stacked system moves slowly east across
Minnesota through Wednesday morning, and finally lifts into the
Great Lakes region by Thursday.

With such a deep and slow moving system there is the potential for
significant snowfall across most of western and central ND Sunday
night through Wednesday night. The brunt of the snowfall is
expected from late Sunday night through Tuesday morning as the
warm moist air continues to feed into western and central ND via
the TROWAL. Winds with this strong system will increase over
western ND on Monday and spread into central ND Monday night and
Tuesday. At this time it looks the snow will be wet enough and
winds will be low enough to keep Blizzard conditions from forming,
but this could change if temperatures are little cooler and winds
a little higher. Regardless winds around 30 mph will cause some
blowing and drifting of snow, limiting visibility and making
travel hazardous. Therefore, a Winter Storm Warning has been
issued for all of western and most of central North Dakota. The
heaviest snow is expected across central North Dakota where 6 to
12 inches could accumulate by Wednesday. The TROWAL begins to
break down Tuesday evening, but synoptic forcing will remain
sufficient to produce light snow through Wednesday night.
Accumulations will become much lighter during this period, but
winds will remain strong through Tuesday evening.

There are still some uncertainties with this storm system. The
biggest being snowfall accumulations, and the potential for
blowing and drifting snow. Due to our very warm November, soil
temperatures remain in the mid 30s to lower 40s. Road surface
temperatures will also be warm during the beginning portions of
this storm. A heavy wet snow is expected initially with a reduced
threat of widespread blowing snow. This combination may initially
limit the severity of impacts, but later as temperatures drop and
surfaces freeze widespread travel impacts are expected.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)

Issued at 1250 AM CST Mon Nov 28 2016

A winter storm will impact all of western and central North
Dakota through Wednesday. Significant hazards to aviation can be
expected. Flight categories will fall to IFR-LIFR all terminals.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 PM CST /5 PM MST/ Wednesday for
NDZ001>005-009>013-017>023-031>036-040>047-050.

Winter Weather Advisory until 6 PM CST Wednesday for NDZ025-037-
048-051.

&&

$$

UPDATE...NH
SHORT TERM...AJ
LONG TERM...AJ
AVIATION...NH



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