Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 211118

Area Forecast Discussion
National Weather Service Bismarck ND
618 AM CDT Wed Mar 21 2018

Issued at 609 AM CDT Wed Mar 21 2018

Upon further review of experimental probabilistic snowfall
accumulations in excess of 6 and 8 inches, available at, decided to issue a Winter Storm Watch
for portions of northwest and north central North Dakota through
the Turtle Mountains and James River Valley for Friday morning
through Saturday morning. The trend from the 18Z through 06Z
global suites has been for increasing snowfall potential. While
some uncertainty in snowfall totals remains due to near freezing
temperatures, a burst of heavy snow occurring Friday morning
before insolation increases may allow for greater accumulation,
including on road surfaces. The 00 UTC GEFS plumes also favor a
watch issuance for the aforementioned areas.


.SHORT TERM...(Today and tonight)
Issued at 250 AM CDT Wed Mar 21 2018

Fog potential highlights the short term forecast for today.

The GOESEast Nighttime Microphysics RGB through 0830 UTC shows
the beginnings of fog development across western North Dakota
where skies have cleared. The RAP/HRRR/NBM/GFSLAMP through their
07 UTC iterations continue to favor an expansion of the fog first
across western North Dakota where skies are clear, with an
eventual expansion across much of central North Dakota through the
morning underneath the stratus. With weak winds, fog may linger
through much of the afternoon for many locations, and possibly
through tonight. Trends will be monitored for a possible Dense Fog

.LONG TERM...(Thursday through Tuesday)
Issued at 250 AM CDT Wed Mar 21 2018

The potential for accumulating snow, and possible light ice
accumulations, Thursday night through Friday night highlight the
extended forecast.

The 00 UTC global suite is in overall agreement on strong moisture
transport into the Northern Plains Thursday night into Friday
ahead of low pressure across southeast Montana and eastern Wyoming
that will propagate east as an inverted trough across North and
South Dakota during the day on Friday. The 00 UTC NAEFS mean
precipitable water values climb to their 90-97.5th percentiles
across much of western and central North Dakota on Friday.
Strong lift associated with low level frontogenesis and warm air
advection will couple with multiple impulses embedded within
southwest flow aloft to support a band of moderate to at times
heavy precipitation. Precipitation type will be heavily dependent
on the surface temperature and ice presence within the
atmospheric profile.

Southwest North Dakota may see little snowfall, as most if not
all the precipitation falls as rain with surface temperatures
expected to remain well above freezing through the event.

Accumulating snowfall potential increases towards the Missouri
River and Lake Sakakawea where surface temperatures will be
hovering near freezing early Friday morning. Precipitation may
start as a rain/snow mix until dynamic coolings increases to
favor all snow. However, with strong March insolation through the
cloud cover, temperatures by mid day Friday are forecast at this
time to become unfavorable for accumulating snow, if not a
complete change over to rain for the these areas.

The greatest snowfall accumulations in excess of 4 inches at this
time are favored across north central North Dakota, the Turtle
Mountains through the James River Valley where thermal profiles
will be coolest. Strong southeast winds coupling with heavy snow
may lead to significantly reduced visibility. Ice loss in the
column Friday night could lead to freezing drizzle mixing in with
the the snow, with possible light ice accumulations. While
confidence is increasing regarding snowfall potential, uncertainty
remains sufficiently high due to near freezing temperatures to
hold off on any winter headlines at this time. Will message the
event for now with an SPS.

Additional accumulating snow is possible Saturday night into
Monday with continued southwest flow aloft over the region.
However, uncertainty remains high.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 609 AM CDT Wed Mar 21 2018

Widespread MVFR/IFR stratus across northwest and central North
Dakota will likely continue for most of the 12 UTC TAF period.
IFR/LIFR conditions in fog are expected to develop early this
morning across western North Dakota, potentially impacting
KISN/KDIK. Fog is forecast to develop Wednesday morning across
central North Dakota.


Winter Storm Watch from Friday morning through Saturday morning
for NDZ002>004-010>013-021>023-025-036-037.



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