Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 170924

Area Forecast Discussion
National Weather Service Bismarck ND
324 AM CST Tue Jan 17 2017

.SHORT TERM...(Today and tonight)
Issued at 322 AM CST Tue Jan 17 2017

Temperatures are the main forecast issue in the short term period.

Currently, upper level ridging was expanding from the Rockies into
the Northern Plains. Upper level shortwave energy moving through the
flow across the southern Canadian Rockies into the Canadian Plains
was associated with a large area of cirrus clouds moving east across
the Northern Plains. At the surface, a large high pressure center
extended from Utah/Nevada eastward into south central ND and central
SD. Meanwhile low pressure was over north central Canada...with
another low over Illinois. This resulted in weak surface winds at
the surface near the high center, but a good southwesterly/southerly
flow over the Front Range and Canadian Prairies.

Today the eastern portion of the high center moves southeast and the
pressure gradient associated with the northern Canadian low tightens
over Montana and the Dakotas. This should result in a more uniform
southwest/westerly surface wind of 10 to 20 mph across ND with the
surface layer mixing with the warmer air aloft. Warm advection
continues today with H850 temperatures increasing to around +10C by
this evening. We expect our afternoon surface temperatures to reach
the mid/upper 20s over eastern portions of central ND...and the mid
30s in the southwest. Followed what the day shift used for max temps
today with a blend of the cooler consensus of the raw model
guidance, which has performed well lately, and our given Superblend.

Tonight the zonal flow aloft from the flattened ridge continues. The
southwesterly surface winds of 5 to 15 mph should be able to be
maintained much of the time. Used a blend of the consensus guidance
and a cooler output from the models. This seems to do well over
areas south and east of Bismarck and tend to have lower max and min
temperatures, since these areas are not on the raised Coteau ridge
(higher elevations along the Coteau should see more uniform
southwest winds at 10 to 15 mph - which in turn keep the lower
atmosphere mixed). Looking at lows tonight from the teens to the 20s
across our area.

.LONG TERM...(Wednesday through Monday)
Issued at 322 AM CST Tue Jan 17 2017

The quasi-zonal upper flow continues Wednesday with a downsloping
southwest to west surface flow. Wednesday is expected to be our
warmest day of the week with highs potentially rising to around 40
southwest. We again leaned toward the cooler side of guidance given
the deep snowpack. Without our snowpack we would certainly see the
potential for much warmer temperatures with unseasonably warm mid
level heights over the northern plains.

The surface gradient relaxes by Thursday and flow turns more
southerly bringing an increase in low level moisture that arrives
in earnest by Friday. On Thursday, expect highs probably a bit
cooler than Wednesday but still seasonably mild.

One additional thing to consider is that if temperatures rise into
the 30-40 range, we will see some widespread melting of the deep
snowpack...and evaporation into the surface layer. This additional
moisture may result in areas of stratus and/or fog over our area.

Friday through Monday a blocking upper level pattern develops to our
east (a ridge over Manitoba/Ontario and a low over the southern/mid
Mississippi Valley). Meanwhile an upper level trough in the west
eventually lifts into the northern plains and stalls as it
encounters the upper ridging to our east. This will bring a chance
of precipitation (mainly snow, but mixed with rain at times) Friday
night through Sunday and possibly into Monday with gradually cooling
temperatures through the weekend. There are still significant model
differences in how and where this blocking pattern sets up and the
resulting weather for the northern plains. At this time appears that
precipitation amounts will be light but will certainly need to
monitor in the coming days.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1220 AM CST Tue Jan 17 2017

VFR conditions will prevail through the forecast period. Mainly high
level cirrus clouds expected across TAF sites. Surface high pressure
was centered over south central ND at midnight CST. As the high
moves southeastward, expect southwest winds to become well
established as the pressure gradient increases throughout the day on




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