Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 191241
AFDBIS

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

.UPDATE...
Issued at 631 AM CST Fri Jan 19 2018

After coord with GGW, have decided to leave the advisory going.
Light rain reported at Sidney and Glendive MT during the past hour
and also precip was indicated at Watford city this past hour.
Expect there has been some precip reaching the ground across much
of Mckenzie county and possibly southern Williams county. Air
temperatures are in the mid and even upper 30s but road
temperatures continue to remain at or below freezing over much of
the advisory area. The exception being the far northwest including
the Crosby and Tioga areas where road temperatures have risen to
33 degrees. Given the road temperatures and the surface reports of
rain, will not cancel the advisory. Will tone down the advisory
as accumulations up to a tenth of an inch are way overdone. Most
likely all locales will see trace amounts up to maybe a couple
hundredths. But that is enough for untreated roads, sidewalks and
parking lots to become slippery. By 9-10 AM central expect road
temperatures to climb above freezing, ending the threat of
freezing rain.

&&

.SHORT TERM...(Today and tonight)
Issued at 332 AM CST Fri Jan 19 2018

Main forecast issue in the short term is the current advisory for
freezing rain. Currently, temperatures are in the mid 30s across
northwest and west central ND. However, road temperatures are below
freezing, thus certainly a potential for freezing rain on untreated
roads, sidewalks, parking lots, etc. There have been a few reports
of light freezing rain over far northeast Montana during the past
hour and think this should move into northwest ND in the next hour
or so.

Bufkit forecast soundings show the best forcing over the northwest
around 12 UTC. The forcing increases atmospheric moisture, but by
the time the atmospheric moisture becomes plentiful, the forcing has
moved south. This area of strongest forcing sags south through west
central and into southwest/south central ND during the morning.

GFS/NAM isentropic analysis shows only a narrow band of higher
condensation pressure deficits dropping south at 295-300K. The RAP
shows a strong jet developing across northwest ND this morning with
maybe a little channeled vorticity tracking along the International
border, but most of the forcing is associated with the mid level
front dropping south. Maybe even some extra mid level forcing over
the southwest and south central around 18z as the right entrance
region of the strong jet moves over this area.

Initial thinking is to leave the advisory going for now. At 12Z, it
looks like the front may be far enough south to cancel the part of
the advisory north of the Missouri, and let it remain through 15z
for areas south. This is where the strongest forcing will be 12-15
UTC. Metro Model shows that by 15-16Z road surface temperatures will
be warming above freezing. With our currently cold road
temperatures, hate to cancel the advisory early.

Again by late morning, will see road temperatures rise enough that
freezing precip will no longer be a concern. There may be a sprinkle
or brief shower drop south into southwest and south central ND
late morning or early afternoon. East of the highway 83 corridor
will probably limit any precip to a mention of sprinkles or
flurries.

Cooler and drier air seeps southward over the forecast area tonight
and Saturday with mainly dry conditions expected.

.LONG TERM...(Saturday through Thursday)
Issued at 332 AM CST Fri Jan 19 2018

The main forecast issue in the long term period will be a storm
system that develops over the central plains on Sunday and tracks
into the upper midwest/lower Great Lakes region through Monday. The
trend has been to move this system a little farther south, only
brushing the far southeast portion of the CWA Sunday and Sunday
night. We did bump up the winds during this timeframe, using a blend
of SuperBlend and CONSMOS.

Once this system exits the region, we remain in a fairly active but
mainly northwest upper flow pattern with weak waves bringing mainly
small precipitation chances, while temperatures remain near seasonal
normals. Will need to monitor the latter portions of the extended
period as another stronger system develops over the plains.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 631 AM CST Fri Jan 19 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/ this morning
for NDZ001-002-009-010-017-018-031-032.

&&

$$

UPDATE...TWH
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...NH



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