Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 111838
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1238 PM CST Mon Dec 11 2017

.UPDATE...
Issued at 1234 PM CST Mon Dec 11 2017

Wind advisory continues down the main RRV corridor through 3pm
local. There is patchy blowing snow and snow squalls reducing
vsby to a mile or less at times. An updated Aviation Discussion is
attached below.

UPDATE Issued at 930 AM CST Mon Dec 11 2017

Have added western OTC and Grant County to the existing Wind
advisory. Winds are penetrating well down into west central MN,
behind the cold front. With much colder air pouring in at the
surface now and cutting under the warmer/moister layer just
above... and we`re seeing some ground based convective snow
squalls in the RRV corridor. So brief enhanced reductions in
visibility with those through the forenoon.

UPDATE Issued at 754 AM CST Mon Dec 11 2017

Received a report of localized areas of blowing snow just south of
Grand Forks. These conditions appear limited to west east
orientated roads in wide open areas. Coverage not enough to
warrant a winter weather advisory, but did update the forecast
with more blowing snow and issued a special weather statement.

UPDATE Issued at 550 AM CST Mon Dec 11 2017

Winds across the northern valley counties are currently 30 mph
gusting to over 40 mph. RAP/HRRR soundings indicate mixing will
continue into the afternoon hours with 925mb winds 40-45 knots. As
such, feel that advisory criteria winds will continue for at least
the morning hours. Issued a wind advisory for the valley counties
and a portion of SE ND until RAP guidance diminishes the winds
aloft. Possible winter weather impacts (blowing snow) may occur
across the part of northwest Minnesota that received fresh snow
and temperatures did not climb above freezing. This is a very
limited area, but will monitor and adjust as necessary.

&&

.SHORT TERM...(Today and tonight)
Issued at 406 AM CST Mon Dec 11 2017

Strong upper level low propagating through the region causing all
sorts of concerns. Initially, precipitation associated with the
vorticity advection across the southern parts of the region is
falling as mostly liquid, and leading to icy roads where
temperatures are below freezing. With that said, temperatures are
rising above freezing which is limiting impacts.

Cold front is currently (10z) situated just north of the
International border, and set to quickly propagate from north to
south through the region this morning. Current radar imagery not
very impressive, and although snow showers will occur with the
fropa, visibility will likely not be limited too much. Winds will
increase, and the main question revolves around magnitude (i.e.
will a wind advisory be needed?). Strong wind indicators (pressure
rise max, cold air advection, winds aloft) would suggest sustained
30mph gusting to over 45mph, but current observations upstream do
not support these values. Most likely a situation where we see a
a brief period (less than an hour) of wind advisory speeds with
the fropa. Winds will begin to diminish by late morning. The other
concern will be flash freeze potential with moist roads and
temperatures above freezing before the fropa. Will monitor, but
roads may have enough time to dry before temperatures drop below
freezing.

.LONG TERM...(Tuesday through Sunday)
Issued at 406 AM CST Mon Dec 11 2017

The parade of clippers out of Canada continues with the grand
marshall leading the parade around the Wednesday timeframe. Guidance
is still struggling with interaction between a compact but strong
vort max rounding the western ridge near southern British Columbia
and energy originating from more northern Canada. However it does
seem guidances wants to keep the former further west into eastern
Montana perhaps preventing phasing between the two once shown
before. Regardless, light snow and elevated winds are expected
Wednesday into Thursday.

Behind the grand marshall comes another clipper shortly after around
late Friday into Saturday. It is advertised that there may be a bit
more moisture to work with as the source air mass will not have as
much time to be modified originating from the Pacific northwest as
opposed to deeper into Canada. This is a result of flattening of the
western ridge which could also bring warmer temperatures into the
region.

Several pieces of energy emanate from the US Pacific northwest out
of the barrel of a more zonal upper level jet max pointed towards
southern British Columbia/Washington state. Interaction with a
Pacific atmospheric river will supply moisture for these pieces of
energy to play with towards the late weekend. Ensemble guidance is
highlighting one piece of energy around the Sunday/Monday timeframe
to cross the region bringing elevated precipitation chances.

Temperatures will continue to be above normal as colder air stays
trapped in the eastern trough. Normal temperatures this time of year
are in the lower 20s for highs to mid single digits above zero for
lows.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1234 PM CST Mon Dec 11 2017

Widespread MVFR CIGS and VSBYS in light snow and blowing snow are
expected across the area through mid afternoon... with strong
north winds gusting to 45 kts along the central RRV corridor.
Conditions will gradually improve through the afternoon/evening
hours. MVFR cigs again possible Tuesday morning.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Wind Advisory until 3 PM CST this afternoon for NDZ008-016-027-
     029-030-039-053.

MN...Wind Advisory until 3 PM CST this afternoon for MNZ001>004-007-
     029-030-040.

&&

$$

UPDATE...Gust
SHORT TERM...TG
LONG TERM...CJ
AVIATION...Gust



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