Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 200515
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1215 AM CDT Fri Apr 20 2018

.UPDATE...
Issued at 1209 AM CDT Fri Apr 20 2018

While the CAM/Meso models show limited fog potential tonight the
surface observations from Tioga to Stanley show 4-5 miles in
light fog. Mainly high clouds cover the area. Kept the mention of
fog in and nudged it closer to northwest North Dakota. Otherwise
current forecast looks ok.

UPDATE Issued at 936 PM CDT Thu Apr 19 2018

No significant updates this evening. Mid and high clouds continue
to lift northward into North Dakota. Current observations show
some minor visibility reductions in Stanley and Tioga, which are
typically lower than surrounding sites. But this was the area
where low clouds were the last to dissipate this afternoon. Also
where mesoscale models hint at fog development again tonight.
Watford City and Hazen also down to 7 miles. With the amount of
high clouds streaming over, it will be more difficult tonight to
discern areas of fog. Will continue to monitor but current
forecast has a good handle on latest observations and expected
trends.

UPDATE Issued at 630 PM CDT Thu Apr 19 2018

Surface high pressure remains over southeast Saskatchewan into
north central and eastern ND. A closed upper low over the desert
southwest is already beginning to spread high level moisture into
the state. With increasing mid and high level clouds tonight and
warmer temperatures combined with more winds aloft, think the
potential for fog is certainly less than last night. Latest CAMS
are also pulling back on the extent of fog over the northwest and
north central later tonight. Will still keep the mention of fog
but may cut back on areal extent with the next update. Did adjust
the diurnal curve a bit this evening as blended short term models
like to drop off temperatures a bit too quick in the evenings.
Until very recently this was the case with our extensive snow
cover and below normal temperatures.

&&

.SHORT TERM...(This evening through Friday)
Issued at 209 PM CDT Thu Apr 19 2018

Fog is likely to redevelop across parts of northwest and north
central North Dakota tonight, continuing into Friday morning.

The latest CAM model guidance and forecast NAM BUFR soundings
support the redevelopment of fog in these areas around midnight,
continuing through about 11 AM CDT tomorrow morning.

A split flow synoptic pattern will continue through Friday with a
large upper level low centered over the Central Plains and nearly
zonal flow across North Dakota. A surface high centered over
Minnesota will lead to 10-15 kt southeasterly winds tomorrow
across western and central North Dakota.

Forecast NAM/GFS BUFR soundings and the latest suite of model
guidance suggest a mostly cloudy day tomorrow across southern
North Dakota with breaks of sunshine in the afternoon for much of
central and northern North Dakota after morning fog lifts. A brief
sprinkle cannot be ruled out across southwest North Dakota along
the border of South Dakota tomorrow. High temperatures look to be
in the 50s.

.LONG TERM...(Friday night through Thursday)
Issued at 209 PM CDT Thu Apr 19 2018

Warmer temperatures with dry weather for the weekend, with the
return of precipitation Monday night into Tuesday highlight the
extended forecast.

The 12z iterations of the GFS and ECMWF favor the continuation of
a split flow synoptic pattern as the large upper level low over
the Central Plains dives southeast into Arkansas by Sunday.

Nearly all of western and central North Dakota should feature
highs in the 60s for Saturday and Sunday with partly to mostly
sunny skies. Most model guidance suggests temperatures that are
too cold for the Missouri Coteau, likely due to a combination of
model snow depth being too high compared to observations and bias-
corrected models struggling with a pattern change to warmer
weather.

A potent shortwave trough swings through North Dakota Monday
night through Tuesday, bringing with it enough moisture and lift
to support light to moderate rain across North Dakota. The 12z
iteration of the GFS suggests moderate to strong mid-level
frontogenesis across southern North Dakota for Monday night,
combined with modest Q-vector convergence. For these reasons,
southern North Dakota looks to have the best chances for heavier
rainfall Monday night.

Wednesday and Thursday look to be dry with the return of zonal
flow across North Dakota. Strong late April sunshine will help
warm western and central North Dakota into the upper 50s and 60s for
both Wednesday and Thursday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1209 AM CDT Fri Apr 20 2018

Surface high pressure across Manitoba will move east today as low
pressure remains in Montana. VFR conditions are expected. Some
light fog is possible 08-12z at KMOT. Otherwise VFR.

&&

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

$$

UPDATE...WAA
SHORT TERM...TK
LONG TERM...TK
AVIATION...WAA



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