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FXUS63 KBIS 172030

Area Forecast Discussion
National Weather Service Bismarck ND
230 PM CST Sun Nov 17 2019

.SHORT TERM...(This evening through Monday)
Issued at 227 PM CST Sun Nov 17 2019

Mostly cloudy skies and mild temperatures are observed across the 
area this afternoon under subtle upper level ridging. A warm 
front tied to a surface low over central Alberta/Saskatchewan will
move across western and central North Dakota late this afternoon 
into tonight. Strong warm air advection and a few impulses 
embedded in northwest flow aloft may produce enough lift to 
generate isolated to scattered showers across much of the area 
this evening into Monday morning. Most, if not all of the 
precipitation will fall in liquid form as maximum temperatures 
aloft are forecast to exceed 3 C. The one exception may be over 
the Turtle Mountains where cooler temperatures may allow frozen 
hydrometeors to mix in. Looking at surface temperatures, much of 
western and central North Dakota is forecast to remain above 
freezing overnight (near record warm minimums), allowing 
precipitation to fall as rain. However, parts of the James River 
Valley and Turtle Mountains could see temperatures fall below 
freezing overnight, resulting in a slight chance of freezing rain.
Little to no accumulation of ice is expected, but if any ice 
should accumulate, it would most likely be limited to the Turtle 
Mountains area.

A shortwave trough digs into the Red River Valley by Monday 
afternoon. Even at this short forecast lead time, models are 
struggling on the track and amplitude of this feature. The ECMWF 
is the farthest south and has the strongest PVA and upper level 
divergence. The NAM is farther north with a much weaker trailing 
jet streak, while the GFS lies somewhere in between. Will maintain
a slight chance of precipitation across northern and central 
North Dakota through the day. Thankfully, temperatures will be 
warm enough for any precipitation that develops to fall as rain 
through the day.

Aside from the light rain potential, Monday will be mild and breezy, 
with highs generally in the mid 40s to lower 50s.

.LONG TERM...(Monday night through Sunday)
Issued at 227 PM CST Sun Nov 17 2019

The main concern for the extended period is a chance of accumulating 
snow Tuesday afternoon into Wednesday.

Benign weather is expected Monday night through Tuesday morning with 
unperturbed flow aloft and diffluent surface flow. Attention then
quickly turns to a shortwave trough ejecting off the Northern 
Rockies into the Northern Plains Tuesday into Wednesday. In the 
last 24 hours, models have trended quicker, weaker, and slightly 
farther south with this feature. Synoptic scale lift ahead of the 
shortwave may induce precipitation as early as Tuesday afternoon 
across parts of western North Dakota. The earlier start time may 
allow a greater percentage of the precipitation to fall as rain, 
though some guidance suggests cooler antecedent temperatures due 
to preceding cloud cover and rapid onset of dynamical cooling. 
Surface temperatures should quickly fall below freezing Tuesday 
evening, allowing precipitation to change over to snow as it moves
across the area. While the current suite of guidance suggests 
maximum QPF less than 0.25", there are still signals that 
mesoscale banding could occur, which are mainly evident in 
frontogenesis and EPV fields. However, mid level lapse rates 
generally around 5 C/km or less do not support banding. Also in 
question are snow ratios. Models do hint at periods of enhanced 
lift in the DGZ, but soundings suggest a deep layer of greater 
than -10 C for snow to fall through, which may cause heavy riming,
reducing snow ratios. All told, this appears to be a low impact 
snowfall at this time, but there is potential for that to change 
as the system comes into greater focus over the next couple days. 
The highest snow amounts are currently favored somewhere between 
Highway 2 and Interstate 94. But there is still considerable 
ensemble spread in both the track and strength of this system.

As the best synoptic forcing begins to exit the area early 
Wednesday, a loss of cloud ice may occur. However, enough lift may 
remain present to generate light precipitation, resulting in 
freezing drizzle. This potential is currently favored over southwest 
into south central North Dakota.

Starting Wednesday night, models are in agreement with strong 
surface high pressure building over the Northern Plains, along with 
a seasonably cool air mass. Upper level ridging over the Rockies 
looks to nudge back east by the weekend, allowing temperatures to 
moderate. There may be a couple clipper type systems moving across 
the region next weekend, but they look dry at the moment.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1149 AM CST Sun Nov 17 2019

MVFR ceilings are expected to scatter out early afternoon at KMOT
and later in the afternoon at KJMS. Otherwise, VFR conditions are
expected through this forecast period, although MVFR ceilings may
redevelop at KJMS later tonight. 5-10 kft ceilings spread across 
the area this afternoon and evening, along with a chance of 
scattered rain showers. Light southwesterly winds will become 
west-northwest and increase to 10-15 kts late tonight into Monday 
morning. The strongest winds are expected at KDIK, where a period 
of low level wind shear concerns may develop later this evening as
2000 ft winds reach 40 kts out of the northwest.




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