Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 182353
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
653 PM CDT Tue Apr 18 2017

.UPDATE...
Issued at 649 PM CDT Tue Apr 18 2017

Cloud trends and fog potential main challenge tonight. Brief
clearing has filled back however after dark likely to see more
clearing as high pressure builds in. Fog potential still
uncertain. No changes to current forecast at this time.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 226 PM CDT Tue Apr 18 2017

Main issue for the period will be cloud cover tonight and if we
get any fog formation.

Water vapor loop shows our upper low that brought up to 1 and even 2
inches of rain to portions of the central and southern CWA exiting
off to the east. Rain has stopped but there is still plenty of
cloud cover wrapping around the backside of the surface low
currently over central MN. There is also a fair amount of stratus
along the front side of the surface high across central and
northwest ND, but some clearing has been trying to move into our
northwestern counties. The surface low will move off to the east
tonight, with a weak surface high building into the Red River
Valley tonight. Winds that have been a bit breezy from the north
will drop off overnight.

The question is what exactly will happen with clouds and if we can
get any fog to form. With light winds and recent rainfall, the low
level boundary layer should have plenty of moisture. However, the
question is how much of the stratus will clear out in order to get
good radiational cooling. There is also a fair amount of mid and
high clouds coming in from upstream as one weak shortwave moves
across southern Canada into Ontario and another comes into the
northern Rockies. There could be some brief clearing between the
low level clouds dissipating and the higher clouds coming in, with
some fog formation not completely out of the question. Included
some patchy mention for a period in the southwestern counties
which has the better shot of seeing both clearing and high
rainfall totals. If it clears out more than expected, may have to
make adjustments.

Tomorrow the shortwave over the Northern Rockies will move into
the Dakotas. The main surface low will be well to our south, but
models are bringing some decent rainfall into the far southern
counties by tomorrow afternoon. Bumped up POPs a bit although with
north to northeast winds bringing in drier air it should cut back
amounts that actually reach the ground.

As for temperatures, with some breaks in the clouds think the far
northern tier could see readings drop below freezing overnight,
while the more moist south should stay in the upper 30s. Highs
tomorrow will be dampened by cloud cover, but should be a few
degrees warmer than today in the low to mid 50s.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 226 PM CDT Tue Apr 18 2017

Thursday night into Friday morning, high pressure will move into the
Northern Plains. This will bring a brief period of clearer skies and
a break from precipitation. By Friday afternoon, warm air advection
from the south will bring in a warmer air mass, increasing high
temperatures into the sixties with low temperatures in the thirties.

The warm temperatures will continue on Saturday with highs in the
sixties and lows in the thirties. A weak low pressure system will
move in by Saturday afternoon starts to deepen overnight. The
biggest challenge in the long term period is in regards to
precipitation with this system. As the upper low matures and moves
eastward, cooler air will advects into the Northern Plains which
could increase our chance for precipitation and cloud cover.

Discrepancies between the models increase after Sunday in regards to
heights and pressure profiles. However, there tends to be moderate
zonal flow through the Northern Plains allowing for cooler
temperatures to continue.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 649 PM CDT Tue Apr 18 2017

MVFR cigs across the south and east will continue to lift through
the evening as high pressure builds into the region. VFR
conditions then expected through the remainder of the period. Only
catch may be fog development however low confidence on fog
development at this time.

&&

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

$$

UPDATE...Voelker
SHORT TERM...JR
LONG TERM...Lee/Anderson
AVIATION...Voelker



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