Area Forecast Discussion
Issued by NWS Bismarck, ND

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000
FXUS63 KBIS 190620
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1220 AM CST Fri Jan 19 2018

.UPDATE...
Issued at 1156 PM CST Thu Jan 18 2018

Latest radar loop shows light reflectivities over central into
northeast MT and some very light reflectivities into Divide
county ND. Latest mesoscale models are showing varying amounts of
qpf spreading into northwest ND. Most keep the majority over
northeast Montana. And none have a great handle on the current
radar. Current air temperatures in northwest ND are in the mid
30s, and road surface temperatures are at or just below freezing.
Will continue the advisory for now with road temperatures at or
below freezing, it won`t take much liquid to make streets and
sidewalks icy. Did trend pops lower late tonight as the overall
trend is slower than previously forecast.

UPDATE Issued at 935 PM CST Thu Jan 18 2018

High-res models continue to try and keep some precipitation in
through the morning over northern portions of the area, so have
extended the timing of low precipitation chances into the late
morning. Otherwise, previous forecast remains in good shape.

On another note, the temperature sensor for the Williston ASOS
(KISN) is giving unrealistically high readings when compared to
observations in the vicinity. So, please discount the report.

UPDATE Issued at 634 PM CST Thu Jan 18 2018

For early evening update have increased cloud cover over the area
in line with current observations. Otherwise, remainder of
forecast appears to be on track. A few of the latest high-res
models are starting to suggest that freezing precipitation could
stick around a little later in the morning. Will see if this trend
continues and may need to stretch the timing for precpitation
chances out a little bit with the next update.

&&

.SHORT TERM...(This evening through Friday)
Issued at 156 PM CST Thu Jan 18 2018

A winter weather advisory for freezing rain northwest and portions
of western North Dakota late Thursday night through early Friday
morning is the highlight of the short term period.

Latest suite of satellite imagery shows a overcast cirrus continuing
across western/central ND. A dirty transitory ridge is sliding
across ND currently, with southwest flow upstream. Upper low
spinning west of Vancouver Island has several shortwaves embedded
within the southwest flow. One such shortwave shifts from
southeastern Oregon and western Idaho, into northeast Montana
overnight.

Game changer to previous thinking as the latest NAM/GFS are both
in good agreement with a burst of strong synoptic scale ascent
atop low level frontogenesis, and steep mid level lapse rates
within the forcing layer. Per BUFKIT soundings, despite a dry
low/mid level layer, dynamic cooling is expected to overcome this
and saturate the lower levels between 06z and 09z Friday. This
event should fall under a high POP and low QPF event, but with
a high impact to travel, especially during the morning commute.
Liquid precipitation amounts are around 0.05 inches within the
strongest ascent region. Expect precipitation to reach central and
eastern Montana during the mid to late evening, then push into
western ND around midnight CST. METRo road forecasts show road
temperatures falling below freezing this evening and remaining
below freezing through the event.

A slight chance of light freezing rain extends into north central
ND between 12z and 15z Friday, but by that point, forcing for
ascent weakens. Areal coverage and precipitation amounts dwindle
quickly. Will highlight this area in the HWO and let subsequent
shifts monitor the precipitation across the west for any
adjustments needed.

Dry conditions elsewhere with mostly cloudy sky conditions. A weak
cold front will slide from northwest to southeast tonight into
Friday morning. Overnight low temperatures in the mid 20s to
lower 30s. For Friday, as mentioned above, a slight chance of
light freezing rain north central ending by mid morning then
mostly to partly cloudy. Highs in the mid to upper 30s.

.LONG TERM...(Friday night through Thursday)
Issued at 156 PM CST Thu Jan 18 2018

Split flow along the west shifts east with a strong southern
stream low pressure moving into Colorado Saturday, then into the
midwest and Great Lakes Monday. The GFS/ECMWF keep the bulk of
precipitation along and south of our southern border, while the
SREF maintains a trajectory into far south central and the
southern James River Valley. Forecast Builder has backed off on
coverage and amounts in the southern James River Valley Saturday
night through Sunday night. Snow amounts of around one inch seem
plausible at this time in Dickey County. Will continue to watch
for adjustments in the track of the low pressure and snow. This
low will pull in colder temperatures as winds become northerly
across western/central ND Sunday and Monday. The result will be
for highs in the 20s. Thereafter The GFS/ECMWF continue to trend
toward a better chance of precipiation around the Thursday
timeframe.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1156 PM CST Thu Jan 18 2018

Light freezing rain is expected late tonight into early Friday
morning over many parts of northwest and west-central North
Dakota, affecting the KISN terminal. Otherwise, VFR conditions
expected.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 AM CST /8 AM MST/ Friday for
NDZ001-002-009-010-017-018-031-032.

&&

$$

UPDATE...TWH
SHORT TERM...KS
LONG TERM...KS
AVIATION...TWH



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