Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 212337

Area Forecast Discussion
National Weather Service Grand Forks ND
637 PM CDT Wed Mar 21 2018

Issued at 637 PM CDT Wed Mar 21 2018

Clearing has progressed west of a Devils Lake to Valley City to
Forman line, with mainly cloudy conditions remaining to the east.
Dew point values are pretty high, in the low 30s, so as
temperatures fall tonight, most models are indicating fog and low
stratus forming. Big question is how long it takes, and am
thinking it may be mid to late evening, with the lowest
visibilities around sunrise.


.SHORT TERM...(This evening through Thursday)
Issued at 300 PM CDT Wed Mar 21 2018

The vort max which produced the morning snow in the Grand Forks
area is near Bemidji but it is weaker and the snow has weakened
with it in the Detroit Lakes-Fosston area and will continue to
weaken thru early evening. Some clearing has moved into the far
western fcst area while clouds cover the rest of the area.

Tonight with light winds and low level moisture, conditions are
favorable for low cloud re-development and some fog...with best
fog chances once again west of the Red River. Clouds should
prevent fog from getting dense but will need to watch. Went on a
high side of low temp guidance tonight some as moist low levels
will prevent much of a fall.

Thursday will see clouds give way to some breaks of sun. If sun
occurs temps will rise into the upper 30s to low 40s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 300 PM CDT Wed Mar 21 2018

Confidence continues to grow in winter weather impacts across
eastern North Dakota Friday night through Saturday.

Afternoon water vapor imagery shows a longwave trough with several
embedded shortwaves off the west coast of the US with an upper level
ridge gradually moving eastward over the western and central CONUS.
Southerly return flow underneath this upper level ridge will help to
advect higher PW air northward through the Plains Thur through Thur
night. This additional high PW airmass will help augment the pacific
airmass that is expected to move into the northern Plains region as
the upper level trough comes onshore Friday. Initial lee troughing
over the northwestern Plains will strengthen southeasterly winds
across the region with wind speeds 15 to 20 mph and gusts 25 to 30
mph on Friday. As one of the aforementioned shortwaves propagates
northeastward through the upper level flow the additional DCVA and
proximity to the right entrance region of an upper level jet over
the Great Lakes region will help induce large scale ascent over
North Dakota bringing widespread snow chances. Mid level
frontogenesis will help support mesoscale banding that could lead to
higher snow amounts across central and eastern North Dakota.

Precipitation is expected to begin Friday morning across western ND,
spreading eastward into central ND by mid day, and into the southern
Red River Valley and western MN by Friday evening. As a 500 mb jet
streak comes over the central Rockies the strongest lee troughing
will shift southward, dragging much of the precipitation with it
overnight Friday and into Saturday.

While forecast soundings indicate that the predominant precip type
will be snow for much of the event, afternoon high temperatures just
above the freezing mark may result in a rain/snow mix across
southeastern ND and the Red River Valley Friday afternoon. While
details are becoming more clear for this event, there is still
uncertainty with the exact timing, placement, and amount of snowfall
and/or rainfall. Impacts to roads and travel will be determined by
whether surface temperatures can climb above freezing during the
day, localized heavy snowfall rates, and how much snow can fall
Friday night into Saturday morning.

Winter weather will diminish through mid day Saturday as light snow
exits the region to the southeast. A second shortwave is expected to
propagate through the region during the day on Sunday, bringing
additional snow chances across northeastern ND and northeastern MN.
Snowfall amounts from this second round are not anticipated to be as
high as from the Friday system.

Additional chances for rain/snow will continue on Monday mainly
along and south of the Highway 2 corridor. However, model
uncertainty and high ensemble spread give low confidence for these
precip chances. Quiet weather is expected to return by the middle of
next week.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 637 PM CDT Wed Mar 21 2018

Models are indicating fog and low stratus forming tonight, first
in the KDVL area. However, temperature and dew point spreads are
fairly close in other areas too. Therefore, think conditions will
deteriorate by late evening and overnight, with the worst
conditions around sunrise. Wind speeds remain pretty light, so it
may take a while into Thursday morning before the fog thins out.
At this point, guidance is showing KDVL, KGFK, and KFAR being
affected the most.


ND...Winter Storm Watch from Friday morning through Saturday morning
     for NDZ006-014-015-024-026-028-029-038-039-049-052-053.

MN...Winter Storm Watch from Friday morning through Saturday morning
     for MNZ003-029-030-040.



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