Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 201808
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1208 PM CST Fri Jan 20 2017

.UPDATE...
Issued at 1205 PM CST Fri Jan 20 2017

Latest webcams along with satellite and surface observations
continue to indicate fog across south central ND including the James
River Valley. However, dense fog exhibiting visibilities of one-
quarter mile or less is becoming less prevalent, and appears more
isolated than widespread at this time. Will allow the dense fog
advisory to expire at noon, however, will issue a Special Weather
Statement for far south central and the southern James River Valley
mentioning areas of fog this afternoon. Per RAP/HRRR soundings, the
low level moisture/fog will be maintained through tonight; however,
the far west will most likely see the least impact.


UPDATE Issued at 912 AM CST Fri Jan 20 2017

Dense fog advisory remains valid over south central portions of
the area into the southern James River Valley so will let it
continue through noon CDT. Main change for mid-morning update was
to place areas of fog through much of the region through the
remainder of the day going through tonight into early Saturday.
Latest HRRR keeps fog over the area through the day into tonight,
and latest sounding analysis is quite reluctant with mixing the
low level moisture out with light winds. Will keep a close eye on
how this fog evolves as additional changes may be needed.

UPDATE Issued at 624 AM CST Fri Jan 20 2017

Dense fog continues across the southern Missouri river valley east
to the James River valley. Current forecast looks good with just
updates to the current observations.

&&

.SHORT TERM...(Today and tonight)
Issued at 311 AM CST Fri Jan 20 2017

In the short term concerns continue to be dense fog and the
potential for freezing drizzle as the low levels are saturated
with relatively dry air aloft.

The current dense fog advisory which runs through noon Friday looks
good with the edge of the stratus/fog layer now around the
missouri river.

Surface temperatures a few degrees above freezing in the James
River Valley will also complicate the drizzle/freezing drizzle
forecast this morning. The Metro model at Medina mp 231 on I-94
keeps the road surface below freezing through 9 am CST so the
potential for drizzle may be east of this area and freezing
drizzle west. So far have not seen to much in precip yet but the
NAM soundings are saturated with weak verticaL motion. So
reasonable to continue DZ/FZDZ.

After the dense fog advisory ends at noon will keep patchy fog
through the afternoon then expect foggy conditions will return
tonight.

.LONG TERM...(Saturday through Thursday)
Issued at 311 AM CST Fri Jan 20 2017

No real issues in the extended at this time. The upper level low
will continue to drift north Saturday and Sunday. This will keep
low chances for snow across the north and east with amounts very
light.

The next chance for snow will be across southern North Dakota
Tuesday. Currently all the deterministic models depict a closed
h500 low tracking eastward south of the state during this period.
The GEFS plumes have a cluster of runs around a tenth of an inch
or less for Bismarck with a few outliers above a half an inch. So
feel current low pops less than 30 percent across the south seem
reasonable. Wednesday and Thursday could be a little breezy as the
GFS and ECMWF build a ridge over the western CONUS and a trough
to the east. This leaves the Northern Plains in a bit of a
pressure gradient. Current grids have 15 to 20 mph which will be
ok for now as its fairly far out. But will continue to watch the
trends as the GFS ensemble mean Surface pressure gradient is
significant while all other models including the GFS deterministic
run more moderate.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1205 PM CST Fri Jan 20 2017

Widespread IFR cigs and vis with areas of LIFR cigs and vis
continue over central and much of western North Dakota. Expect
visibilities may improve a bit this afternoon, before
deteriorating again towards evening. Patchy FZDL also expected
over many parts of the area this afternoon into tonight.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...KS
SHORT TERM...WAA
LONG TERM...WAA
AVIATION...JJS



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