Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 221717

Area Forecast Discussion
National Weather Service Bismarck ND
1217 PM CDT Thu Mar 22 2018

Issued at 1215 PM CDT Thu Mar 22 2018

Dense fog over central into parts of western North Dakota has been
reluctant to dissipate, so have extended dense fog advisory into
the mid-afternoon. Have also added a few counties on the western
edge as satellite indicated some fog creeping a bit westward.
Otherwise, remainder of forecast continues to be on track with the
highlight continuing to be the snow late tonight into Friday.


.SHORT TERM...(Today and tonight)
Issued at 250 AM CDT Thu Mar 22 2018

Dense fog over much of northwest and central North Dakota
highlights the short term.

Clearing skies yesterday evening, light southerly winds, and
abundant recent moisture at the surface has facilitated widespread
dense fog along and generally north/east of Lake Sakakawea and the
Missouri River. GOES-16 fog difference channel and the night-time
microphysics RGB product outline this area nicely. Fog should
diminish by late morning or early afternoon.

At the upper levels, a ridge will progress towards western North
Dakota through the afternoon, with the axis translating across the
state overnight, transitioning the forecast area into a southwest
flow regime.

As return flow increases with a digging western trough
approaching, a mix of rain and snow will begin late tonight over
the southwest, announcing the initial approach of a strong winter
storm that will impact western and central North Dakota Friday
and Saturday.

.LONG TERM...(Friday through Wednesday)
Issued at 250 AM CDT Thu Mar 22 2018

Hazardous winter weather returns to the forecast area by Friday
morning. A potent shortwave will eject from the western trough,
with impressive moisture transport entering the southwest, aided
by a strong mid-level jet max. NAEFS guidance remains constant,
holding onto the 99th percentiles of moisture transport and
precipitable water anomalies over the south.

By 12z on Friday, moderate low level and strong mid level
frontogenesis will overlap strong upper level Q-Vector
divergence. This zone will be the focus of rapid precipitation
development as strong forcing will facilitate vigorous upward
motion in the saturated dendritic growth zone. A tight temperature
gradient will also characterize this frontal zone, and snowfall
amounts and location of the heaviest accumulations will depend on
where it sets up. Southwest of the frontal zone, rain will be the
dominant precipitation type, with snow mixing in at times.

Guidance has been fairly consistent that the transition zone will
generally reside along Lake Sakakawea and the Missouri River
Valley. Areas north and east of this gradient will experience
heavy wet snowfall and accumulations in the 6 to 10 inch range
with localized amounts up to 12 inches. For these areas, we
decided to upgrade the winter storm watch to a winter storm
warning except for the James River Valley. Moving south and west
from this band, forecast accumulations drop off quickly. As we
move towards Friday night and into Saturday morning, BUFKIT
soundings suggest the potential of freezing drizzle across the
eastern half of the forecast area.

Surface winds will increase through Friday afternoon as strong mid
level momentum digs into the shallow mixed layer near the
surface. This will promote wind gusts as high as 35 to 40 mph
over the central part of the state and the James River Valley.
Periods of near whiteout conditions are possible.

Finally, in the wake of the winter storm, we will remain in an
active southwest flow pattern through the beginning of the week.
Subtle ejecting shortwaves from the western trough will bring
periodic chances of light rain or snow through Monday before we
make the transition back to northwest flow aloft.


.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.


Dense Fog Advisory until 4 PM CDT /3 PM MDT/ this afternoon for

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

Winter Storm Watch from Friday morning through Saturday morning
for NDZ005-013-050-051.



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