Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 190628
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1228 AM CST Thu Jan 19 2017

.UPDATE...
Issued at 1226 AM CST Thu Jan 19 2017

The latest iterations of the short term high res models indicate the
greatest potential for fog is across the James River Valley. Have
added patchy/areas of fog there through the morning hours. Dense
fog has developed over northeastern SD...and may need to issue a
dense fog advisory later this morning.

Not confident enough to add the mention of patchy fog over a
large area of western and central ND despite some melting in the
snowpack on Wednesday. The reasoning is the large dry layer just
off the surface may inhibit fog most areas.

UPDATE Issued at 939 PM CST Wed Jan 18 2017

The forecast remains well on track and was blended to observed
trends through 03 UTC.

UPDATE Issued at 707 PM CST Wed Jan 18 2017

Little change other than to blend to observed trends through 00
UTC and add a patchy mention of fog with snow melt. The greatest
potential for fog is across the James River Valley per trends in
the 22-23 UTC RAP/HRRR/GLAMPMELD visibility forecasts.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 131 PM CST Wed Jan 18 2017

The main forecast problem in the short term period will be
temperatures.

Currently, Broad upper level ridging across the northern plains with
a west to southwest surface flow. This is resulting in mild
temperatures across western and central ND.

Tonight and Thursday...One byproduct of our mild temperatures will be
the introduction of low level moisture into the boundary layer.
This may result in some patchy fog tonight, given our light winds
and lack of sky cover. However, there is abundant dry air just
above the surface so am not confident enough to mention fog at
this time. Think it would be very shallow and patchy in nature
and evening or overnight shift can monitor. If we do remain clear
we will likely see temperatures on the cools side of guidance and
this is where we leaned for our overnight lows.

We will begin to see increasing moisture on Thursday as flow turns
southerly. But before low fog/stratus arrives, we should see another
mild day on Thursday with dry conditions. Highs mainly in the 30s on
Thursday.

.LONG TERM...(Thursday night through Wednesday)
Issued at 131 PM CST Wed Jan 18 2017

The main forecast issue in the extended period will be precipitation
chances and types.

Low level moisture flux into the area continues Thursday night
and Friday as a wave tracking across the southern U.S encounters
upper level ridging and lifts northward into the northern plains.
Forcing with this system is weak and model generated QPF is
minimal. However with our increasing low level moisture and dry
atmosphere aloft, we will see the potential for some drizzle or
freezing drizzle, depending on the temperature. Moisture remains
confined to eastern ND Thursday night and over the James River
Valley into the Devils lake Basin Friday. Temperature profiles do
not support snow so limited precipitation type to drizzle.

late Friday night through Saturday night another wave lifts
through the central and into the northern plains. The mid level
support is a little more robust and thus the chances for
precipitation will be a little higher. The atmosphere will
continue to slowly moisten and cool during this period. Thus we
transition from an environment favorable for drizzle Friday night to
more of a snow set-up by Saturday night. Utilized a multi-model
blend to depict the temperature aloft profile, giving at least a
mention of drizzle/freezing drizzle Friday night through Saturday
night.

By Sunday we should be cold enough for all snow, but by this time
the wave is lifting northward into Canada and any additional snow
accumulations will be light.

Overall, Friday through Sunday looks dreary with cloudy skies and
drizzle/freezing drizzle...fog and light snow/flurries. At this
time we are not anticipating any significant snow accumulations,
likely an inch or less most areas through the entire weekend. The
Turtle Mountains into the James River Valley could see a little
higher amounts through the period, but this will also depend upon
when temperature profiles begin to support snow. Still looking at
maybe 2-3 inches through the entire period of Friday night through
Sunday. At this time the potential for any significant ice
accumulation looks to be farther east into eastern ND or more
likely into northern MN, but with only small amounts of ice
needed to create significant issues, we will need to monitor.

Temperatures will not be dreary with above normal highs in the 20s
and 30s through the weekend. Temperatures do cool back down
closer to normal for the early part of next Week.

There are significant deterministic model differences, and a large
envelope of ensemble solutions regarding the evolution of a wave
tracking across the central portion of the country as we move
toward the middle of next week. At this time a multi-model blend
is giving us chance pops across mainly the southeast half of the
CWA with slight chance pops northwest. Still way too early for
anything more than this.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1226 AM CST Thu Jan 19 2017

There is a potential for patchy fog across western and central ND
this morning, due to increased low level moisture from evaporation
of snow melt across the snowpack on Wednesday. The latest iteration
of the short term model hints at a better chance for stratus/fog in
the James River Valley beginning around 08z and spreading northward
into KJMS before daybreak. Will mention a tempo group for all TAF
sites with some 3-5sm in fog. May need to update KJMS if fog becomes
more dense or if a stratus deck develops as well.

&&

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

$$

UPDATE...JV
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...JV


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