Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 190931
AFDBIS

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

.SHORT TERM...(Today and tonight)
Issued at 329 AM CST Thu Jan 19 2017

The main forecast problem in the short term period will be
temperatures and possibilities of fog. Will issue a dense fog
advisory for the southern James Valley counties of Dickey and
Lamoure.

Currently, a broad upper level ridge extended over central North
America with a longwave trough over the west coast. A cutoff low was
over the central Plains of NE/KS. The broad ridge was associated
with a south to southwest surface flow and southwest to west mid
level flow, resulting in mild conditions across western and central
ND. Temperatures were in the 20s to lower 30s where winds of around
10 to 15 mph were occurring; and in the teens where winds were
light. A moist low level southerly wind flow over the southern and
central Plains into the eastern Dakotas and Minnesota was advecting
a large area of fog and stratus.

Our mild day Wednesday, with temperatures mainly in the 30s to lower
40s, allowed some melting of the extensive snowpack across western
and central ND. This has introduced low level moisture into the
boundary layer. So far this morning, there has not been any fog
formation due to the snowmelt. However, fog in eastern SD was moving
northward and had already entered the James Valley in ND - Dickey
County. Kept a mention of fog in the James Valley this morning.
Forecast soundings at Jamestown indicate the fog should dissipate
later this morning. The concern is whether the visibility will go
below 1/2 mile - which would warrant a dense fog advisory.

We are expecting another mild day today with high temperatures in
the 30s. Additional melting of the snowpack will add more low level
moisture to the boundary layer. The James Valley may see stratus
clouds moving in this afternoon.

This evening the stratus clouds should be expanding northward and
westward across ND. Forecast soundings for Jamestown indicate a
saturated lower layer (the stratus) with dry air above, which would
favor drizzle (freezing drizzle as temperatures fall into the teens
and 20s tonight). Mentioned a slight chance of freezing drizzle late
tonight in the southern James Valley.

.LONG TERM...(Friday through Wednesday)
Issued at 329 AM CST Thu Jan 19 2017

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

Low level moisture flux into the area continues Friday as the
central Plains low lifts northward into the Northern Plains.


Forcing with this system is weak and model generated precipitation
is minimal. However with our increasing low level moisture and dry
atmosphere aloft, we will see the potential for fog and stratus
expanding north and west across the state. The upper level low moves
north through the eastern Dakotas Friday, and the temperature
profiles suggest freezing drizzle or snow possible in the James
Valley daytime Friday. The upper low backs to the west Friday night,
allowing the chance of freezing drizzle or snow to expand into
central and western ND. Meanwhile the west coast longwave trough
expands eastward and encompasses much of the US, keeping ND in the
clouds, with chances of drizzle/freezing drizzle and light snow
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.

Temperatures should be above average with highs 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.

The GFS and EC develop a low pressure system tracking eastward
across the central Plains around mid 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...
Dense Fog Advisory until 9 AM CST this morning for NDZ048-051.

&&

$$

SHORT TERM...JV
LONG TERM...JV
AVIATION...JV



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