Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 180046
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
646 PM CST Sun Dec 17 2017

.UPDATE...
Issued at 629 PM CST Sun Dec 17 2017

Fog and low stratus deck the main concern and impact this evening
and overnight. Lowest visibilities so far at Crookston METAR
showing a half mile. Will continue to monitor its evolution and
coverage. Dense fog advisory a definite possibility this
evening, will see how observations do over the next couple hours.


&&

.SHORT TERM...(This evening through Monday)
Issued at 200 PM CST Sun Dec 17 2017

Concerns will be fog potential tonight and then snow chances on
Monday. 12z guidance in good agreement.

Lots of questions regarding clouds and fog potential for tonight.
Clouds and fog remain this afternoon where SFC dewpoint values
are in the upper 20s/low 30s. Latest RAP guidance indicates this
low level moisture will remain in place, and advect northward this
evening, placed along and east of the valley. With this thinking
in mind, will go mostly cloudy with fog east of the valley. Not
sure about dense fog potential but will monitor into the evening
hours. Anticipate high clouds overtaking the region by 12z Mon.
Warm air advection overnight will make min temp forecast tricky.
Steady temps along with clouds. Areas with no clouds this evening
will likely see a quick temperature drop before steadying and
possibly slowly rising. How far these temps fall is uncertain.

Left exit region of a strong upper level jet brings forcing and
snow chances to the northern half of the region on Monday.
Increase these snow chances based on the latest guidance. Most
guidance also indicating weak MUCAPE (up to 50 J/KG). Given the
forcing along with the potential for weak instability, convective
type snow showers could lead to a quick 2-4 inches on Monday. Main
message is for widespread snowfall totals of 1-2 inches with
localized snowfall up to 4 inches possible.

.LONG TERM...(Tuesday through Sunday)
Issued at 200 PM CST Sun Dec 17 2017

A sfc ridge builds into the area on Tuesday with NW flow aloft
becoming more zonal by Wednesday.  This will allow an abundance of
Pacific moisture to move across the northern Rockies and into the
northern tier as sfc low pressure develops lee of the Rockies and
moves across the plains.  Models continue to show a band of snow
across the CWA Wed aftn...for the best chance of widespread snowfall
accumulations in the long term period.  Models are showing
significant snowfall accumulation in the Cascades/Northern Rockies
so QPF amounts still in question as well as track of sfc features,
but do think one to three inch accumulations across at least eastern
ND is possible.  QPF amounts and calculated snow fall accumulations
did come in a bit lower today which makes sense with what is
expected in the PAC NW.  Beyond Wed, low chances of snow continuing
across the far south into Friday but main feature is a push of cold
air that brings Christmas Eve highs possibly into the single digits
below zero across the northern two thirds of the CWA.  Adjusted
temps with a 50/50 Superblend/CONSALL solution for Thu-Sun, however
coldest temps will be dependent on cloud cover, winds, and where
exactly the freshest snowfall sets up mid week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 629 PM CST Sun Dec 17 2017

LIFR conditions at TVF trying to work into FAR and BJI this
evening as low stratus deck with fog lifts to the north and
expands in coverage this evening across NW MN. Stratus deck will
persist into the overnight before it slides to the east towards
morning.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
&&

$$

UPDATE...JK
SHORT TERM...TG
LONG TERM...Speicher
AVIATION...JK



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