Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 180517

Area Forecast Discussion
National Weather Service Bismarck ND
1217 AM CDT Sun Mar 18 2018

Issued at 1210 AM CDT Sun Mar 18 2018

Short term/meso scale models continue to show large areas of fog
forming across west and central north dakota. The large stratus
area in place may slow the fog formation a bit and have doubts it
will be as dense as modeling suggests. Will keep patchy to areas
of fog n the forecast for now. The clear skies over central North
Dakota will fill in and become cloudy shortly. Current forecast
looks ok.

Issued at 942 PM CDT Sat Mar 17 2018

Clearing across central ND persists. Used a blend of the last two
HRRR iterations for sky grids, which is similar to the RAP/NAM in
filling in this clear area with clouds between 06-09Z. No other
changes at this time.

Issued at 640 PM CDT Sat Mar 17 2018

Sky cover was adjusted with a rather large hole in the stratus
deck over portions of western and central ND currently. This hole
will fill in this evening along with fog developing. Temperatures
were adjusted upwards with cloud cover tonight keeping values from
dropping too much. Otherwise edits to the forecast were minor.


.SHORT TERM...(This evening through Sunday)
Issued at 243 PM CDT Sat Mar 17 2018

The main focus for the short term is fog tonight and mixed
precipitation developing afternoon tomorrow.

Tonight, warmer and more moist air starts to be advected in. Low
stratus is already forming across southwest North Dakota in
response to this return flow. Low stratus will continue to develop
and overspread most of western and central North Dakota tonight.
An upslope component to the winds will further aid in the
development of stratus and eventually fog late tonight. Fog may
become dense in some of the valleys later tonight.

Tomorrow, the next storm system approaches North Dakota. Several
small upper level waves will rotate around the main upper level
circulation currently located in the Pacific Northwest. One such
wave will swing through southwest North Dakota Sunday afternoon.
This will combine with developing frontogenesis to spark an area
of precipitation oriented southwest to northeast across western
North Dakota. The evening hours on Sunday will see a period where
there is support for banded precipitation with frontogenesis, an
upper level jet streak and fairly steep mid level lapse rates. The
period of highest precipitation rates will be late Sunday
afternoon and Sunday night. With temperatures in the critical
threshold of mid 30s there could be mix of rain, freezing drizzle
and snow Sunday afternoon and evening.

.LONG TERM...(Sunday night through Saturday)
Issued at 243 PM CDT Sat Mar 17 2018

The focus in the extended will be the Sunday and Monday period.

There continues to be some uncertainty in the snow amounts,
however, we are seeing convergence on a location of highest
accumulation. It appears west central North Dakota, locations
generally between Bismarck and Dickinson, will see the highest
accumulations. There appears to be a good chance for at least four
inches over west central North Dakota for Sunday night and
Monday. We continued the Special Weather Statement, with headlines
possible later tonight/tomorrow.

Tuesday through Thursday will see a building ridge across the
Northern Plains which will suppress precipitation, but another
rather robust negatively tilted upper low is forecast to move from
the northwest US into the Northern Plains by Friday. This will
provide another opportunity for precipitation, both rain and snow.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1210 AM CDT Sun Mar 18 2018

Hazards to aviation include widespread IFR to LIFR conditions in
areas of fog and low stratus expected to develop across est and
central North Dakota Sunday morning. This will be followed by
developing snow over western North Dakota Sunday evening. Patchy
areas of freezing drizzle are possible but too much uncertainty to
include in TAFs at this time.




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