Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 100030

Area Forecast Discussion
National Weather Service Bismarck ND
630 PM CST Sat Dec 9 2017

Issued at 621 PM CST Sat Dec 9 2017

A weak clipper tracking southeast through northwest Minnesota has
resulted in some gusty gradient winds across western and portions
of central North Dakota this afternoon and early evening. The winds
will continue to die down this evening with the more traditional
gusty spots in north central North Dakota taking a bit longer.
The clipper will bring a few clouds into the north and east later
tonight otherwise the weather should remain dry. Current forecast
looks ok.


.SHORT TERM...(This evening through Sunday)
Issued at 320 PM CST Sat Dec 9 2017

A mild Sunday highlights the short term forecast.

A north-south oriented warm front extended from western Manitoba
across the eastern Dakotas this afternoon. Temperatures were in the
40s across southwest North Dakota, with 30s spreading across
northwest, north central, and south central North Dakota.

This warm front will continue moving east as a west coast upper
level ridge continues to expand eastward across the Rockies and
western Plains. This warm airmass remains in place through Sunday,
with even warmer H850 temperatures advecting into the state. As in
the past few model runs, the 00z NAEFS 850mb mean temperatures are
forecast to be around the 90th percentiles along and west of highway
83. Kept the higher side of forecast temperature guidance with highs
in the lower 50s for much of southwest and south central ND, with
40s elsewhere except in the Turtle Mountains and along the James
River Valley, where highs should reach into the 30s.

.LONG TERM...(Sunday night through Saturday)
Issued at 320 PM CST Sat Dec 9 2017

Strong winds Sunday night into Monday with a clipper system
highlight the long term forecast.

On Sunday, a fast-moving shortwave in the upper level flow is
forecast to propagate out of northern British Columbia and dive
southeast along the upper level ridge, reaching southern
Saskatchewan by Sunday evening, and reach northeastern North Dakota
by midnight Sunday night, into southern Minnesota by daybreak Monday
morning. This shortwave and its associated surface low track is a bit
farther east than depicted in yesterday`s model runs. The strongest
cold advection and highest 3-hour pressure rises are now forecast to
be over eastern North Dakota and western Minnesota late Sunday night
through Monday morning. We are still expecting strong and gusty
northwest winds to develop Sunday evening, with strongest winds
occurring from late evening Sunday night through early afternoon on
Monday. This is the time when H850 winds of 50-55 knots are
occurring, with surface winds mixing up almost to that
pressure/height. We may need a wind advisory, moreso for central ND.

After the clipper Sunday night and Monday, warm advection builds
back in for Tuesday as the persistent western upper level ridge
expands eastward again across the western Plains. We are looking at
high temps again in the 40s across southwest and parts of
northwestern ND.

Yet another clipper system is forecast to ride the upper ridge out
of northern Alberta across the Dakotas Tuesday night/Wednesday, with
global models not in agreement on placement and timing. There is a
hint in the global solutions that by the end of next week the
western ridge may be breaking down, allowing more transitory large-
scale waves to move across North America.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 621 PM CST Sat Dec 9 2017

Main hazard to aviation will be wind shear as high as 50kts through
06z from 2000 agl. Otherwise VFR through the forecast period.




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