Area Forecast Discussion
Issued by NWS Bismarck, ND

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959
FXUS63 KBIS 091238
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
638 AM CST Sat Dec 9 2017

.UPDATE...
Issued at 634 AM CST Sat Dec 9 2017

No changes for today other than for observed trends through 12
UTC.

&&

.SHORT TERM...(Today and tonight)
Issued at 240 AM CST Sat Dec 9 2017

A mild day today highlights the short term forecast.

A stationary front between US Highway 83 and ND Highway 3 across
central North Dakota will propagate east as a warm front today.
Maintained the forecast trend to go above the 00 UTC guidance
consensus for high temperatures for today, especially to the west
of ND Highway 3. The challenge remains how deep mixing will become
today. The 00 UTC NAM/GFS Bufr and the 07 UTC RAP soundings all
suggest rather shallow mixing with a strong inversion above the
925-880mb layer. However, the thinking is with gradient west-
northwest winds of 10-20kts and a very shallow and depleting
snowpack, that mixing will be greater allowing warmer temperatures
to be achieved. Widespread 40s are forecast west of ND Highway 3,
with temperatures in the lower to mid 30s east where mixing will
be less.

.LONG TERM...(Sunday through Friday)
Issued at 240 AM CST Sat Dec 9 2017

Another mild day on Sunday, followed by strong winds Sunday night
into Monday highlight the extended forecast.

With no airmass exchange, another mild day is expected on Sunday,
once again trending above the 00 UTC guidance consensus with
greater mixing anticipated with favorable westerly winds. The 00
UTC NAEFS 850mb mean temperatures remain near their 90th
percentiles generally along and west of US Highway 83. Maintained
the thinking for high temperatures in the lower 50s southwest and
south central. Further north, increasing cloud cover may hold
temperatures in the 40s northwest and north central.

A cold front associated with a clipper will rapidly propagate
across western and central North Dakota from north to south Sunday
evening and night. Strong northwest winds are expected behind the
front. The strongest winds are forecast in the 06-12 UTC window
when lapse rates and cold air advection increase, coincident with
the greatest isallobaric forcing. However, the 6-7mb/3 hr pressure
rise bubble and greatest isallobaric forcing are forecast to
impact eastern North Dakota to a greater degree. With 45-55kts at
the top of the mixed layer, wind headlines are certainly
possible. However, the strongest gusts are likely to occur over a
short window when isallobaric forcing is greatest.

Another warm front is favored to quickly overtake western and
central North Dakota on Tuesday with well above normal
temperatures favored for most of the area.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 634 AM CST Sat Dec 9 2017

MVFR stratus is expected to impact KJMS and the James River Valley
and through the Turtle Mountains through at least 14-15 UTC.
However, this is a bit uncertain and may persist longer this
morning. Otherwise, VFR conditions are forecast across western and
central North Dakota for the 12 UTC TAF cycle. A stationary front
across central North Dakota as of 12 UTC will move east as a warm
front today. West-northwest gusts of 20-25kts are expected behind
the front, locally higher southwest near 30kts. Low level wind
shear is likely across most of the area this evening and tonight
with strong winds in an inversion off the surface.

&&

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

$$

UPDATE...PA
SHORT TERM...PA
LONG TERM...PA
AVIATION...PA



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