Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 221949

Area Forecast Discussion
National Weather Service Bismarck ND
249 PM CDT Thu Mar 22 2018

.SHORT TERM...(This evening through Friday night)
Issued at 238 PM CDT Thu Mar 22 2018

Main highlight is the winter storm set to arrive early Friday
morning. All types of wintry precipitation will be possible with
heavy snow likely for northwest, central, and eastern North

Water vapor analysis depicts a potent Pacific trough with southwest
flow over the Great Basin and into the northern Rockies. The
downstream upper level ridge axis was centered over the eastern
Rockies into eastern Montana and through the western Canadian
prairies. Light winds and subsidence associated with the
anticyclonic flow aloft was keeping fog in place through areas of
western and central North Dakota. Would expect at least areas of fog
to continue tonight as the upper ridge axis shifts over the state.

Overnight tonight a shortwave ejects out of the western trough and
on over the northern Rockies. Mid level winds turn southeasterly,
with winds at 850 mb increasing to 40-50 knots by early Friday
morning and enhancing moisture transport ahead of this wave. A band
of deep frontogenesis overlaid by Q-Vector convergence crosses into
southwest ND during the overnight hours, signifying the arrival of
strong mesoscale-synoptic coupled ascent. This band pushes eastward
through the day. Expect mostly rain in the far southwest where a
warm nose aloft remains strongest and a transition to snow over west-
central ND. Greatest confidence for heavy accumulating snow lies in
a swath of 8 to 12 inches from northwest and north-central ND down
southeast through the upper James River Valley.

The major note of concern in this forecast remains precipitation
type along a thermal gradient mostly aligned with the Missouri River
through Lake Sakakawea. Forecast soundings in this area depict a
temperature profile near freezing for much of the event which will
A) create lower snow ratios and B) potentially create an area of
more liquid precipitation which would drastically cut down snow
accumulation totals on the southwest edge of the band of snow.

A second area of concern in snowfall totals is an area of drier air
in the 12Z NAM/GFS runs progged to pass over south-central North
Dakota by mid-day Friday. The impact on snow accumulations will
depend on the depth of this dry layer, but could be a reason for a
lull in precipitation across the south-central during the day

Tightened surface pressure gradients associated with the deepening
low will be responsible for wind speeds up to 20-30 kts. While
this means blowing snow and lowered visibilities will be a threat
with this storm, the nature of the wetter snow will mean the
blowing snow threat will be less than what would normally be
expected with this wind/snowfall combination.

As this wave meanders off to the east, a loss of ice growth aloft
will lead to a threat of freezing drizzle on the back end Friday night.

.LONG TERM...(Saturday through Thursday) Issued at 238 PM CDT Thu
Mar 22 2018

The aforementioned Pacific trough crosses the western coastline
overnight Friday night into Saturday, continuing southwest flow
over the Northern Plains. Another wave ejects over the northern
Rockies early Sunday morning, bringing chances for mixed
precipitation through the day. Models diverge in agreement on
synoptic forcing and moisture associated with this system, which
leaves high uncertainty for totals and precipitation types.

Into next week, global models hint at a deep low moving through
the southwest with a northern Canadian low to our north. There are
signs of a few impulses moving through the cyclonic flow over our
area but once again certainty in any timing or intensity remains


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1215 PM CDT Thu Mar 22 2018

Widespread LIFR/VLIFR conditions in fog and stratus lingering at
KBIS/KMOT early this afternoon. There may be a break in the IFR
conditions for a couple hours this afternoon, then back into the
LIFR/VLIFR again by around 00z.

MVFR/VFR off and on at KJMS this afternoon, becoming IFR by
around 00z.

VFR initially at KISN and KDIK, but seeing trends of IFR stratus and
fog moving westward from central ND. Thus expecting conditions to
deteriorate to MVFR/IFR during the afternoon.

Tonight widespread LIFR/VLIFR conditions in stratus and fog, then
rain/snow developing in southwestern ND mainly affecting KDIK aft
03z, spreading to KISN/KBIS aft 06z as mainly snow, reaching
KMOT/KJMS around 12z as snow. Conditions remaining IFR through the
day Friday with heavy accumulating snow and strong southeast winds
for all TAF sites. The far southwest corner of ND may see mainly
rain - at Hettinger, Bowman, and Beach airports.


Winter Storm Warning from 4 AM CDT /3 AM MDT/ Friday to 7 AM CDT
/6 AM MDT/ Saturday for NDZ009-010-018>021-034-035.

Winter Weather Advisory from 1 AM CDT /midnight MDT/ Friday to 1
AM CDT /midnight MDT/ Saturday for NDZ017-032-033-041-042-045-

Winter Storm Warning from 7 AM Friday to 7 AM CDT Saturday for



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