Area Forecast Discussion
Issued by NWS Grand Forks, ND

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911
FXUS63 KFGF 201245
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
645 AM CST Mon Feb 20 2017

.UPDATE...
Issued at 645 AM CST Mon Feb 20 2017

The dense fog over the Devils Lake region has been expanding
eastward overnight, and now has spread into portions of the
central and northern Red River Valley. Therefore, also expanded
the dense fog advisory to include these areas as well.
Observations and web cams show that there are holes with better
visibilities from New Rockford up through Devils Lake, so will
continue to watch and see if this holds or expands in area. If so,
may be able to cancel the dense fog advisory a little earlier in a
few spots.

Otherwise, the showers and tstms continue from the southern Red
River Valley up toward the Lake of the Woods. Increased pcpn
chances through this corridor, but so far amounts have not been
all that impressive. The radar would estimate the highest amounts
from just north of Fergus Falls to near Detroit Lakes with over a
quarter inch of accumulation, but have no ground truth for that.
Other observations outside this area have generally been less
than a tenth of an inch. High resolution models continue to keep
most of the additional pcpn through this same corridor, before
sliding it off to the east by later this afternoon.

&&

.SHORT TERM...(Today and tonight)
Issued at 250 AM CST Mon Feb 20 2017

Plenty of forecast challenges today, namely dense fog/pcpn
chances/thunder/pcpn amounts and record high temps. So far,
showers with embedded thunder have been moving quickly NNE out of
eastern SD and western MN. Models have shown a ribbon of mid
level instability with a low level jet, working through the Red
River Valley into the northwest quarter of MN today, so that has
been consistent. However, the latest model runs have shown the
instability arriving sooner and ending sooner, so kept the thunder
mentioned this morning and removed it for the afternoon. The pcpn
has developed a little further east than the latest high
resolution models showed, so basically the entire FA has pcpn
chances today. Pcpn amounts so far have been spotty and fairly
light.

The spottiness is always a function of convection, so amounts
will stay on the variable side. Overall, thinking most areas will
probably be lower than a tenth to a quarter of an inch, but if
several rounds of stronger echoes move over the same area, some
quarter to half inch amounts are possible. This would mainly be
over the southern Red River Valley up into NW MN. Dense fog
developed over the Devils Lake region, where the low level
moisture moving northward has encountered the coolest sfc temps.
Went with a dense fog advisory for several counties around Devils
Lake through mid Monday morning. Will keep an eye on visibilities
in that area and adjust as need be. Finally, forecasting a record
high at Fargo, but it appears the Grand Forks records will be
safe. High resolution models show any pcpn moving off to the NE by
late this afternoon, so kept tonight dry.

.LONG TERM...(Tuesday through Sunday)
Issued at 250 AM CST Mon Feb 20 2017

Tuesday will be the last very mild day, and are currently
forecasting highs just below records. Models continue to show some
light pcpn developing as well, but the details remain quite
sketchy. There is much better agreement by late Tuesday night
into Wednesday, in showing pcpn developing mainly across the
northern half of the FA. Low level temps during this time frame
are borderline for rain or snow, depending on the time of day and
location. The day 2 winter weather map shows an inch or two of
snow possible across the north, but mainly over the Devils Lake
region. Even a hint for freezing rain on the southern fringe of
the pcpn band is indicated. So this system will also bear
watching. Models also differ quite a bit on how fast it will exit
off to the east, but it looks to be by Wednesday evening.

Longer range models are currently in fairly close agreement on
developing a broad trof across northcentral Canada NOAM and
extending southwestward across the western half of the CONUS. This
leaves the path opened for a series of fairly wet systems to work
through the intermountain west and to produce some winter-like
activity into the Great Plains states.

Thursday and Friday... The GFS and ECMWF have been most consistent
in developing a Colorado Low type system across the central plains
...with heavier snow indicated across portions of SD and southern MN
...and only a brush of snow across far southern Red River Valley and
adjacent portions of west-central MN. This most of our area should
stay under a mainly dry northerly flow... with temperatures still
ranging a bit above long term seasonal normals even on Friday.

Saturday and Sunday... though a muddy H5 trof axis persists just
west of the FA into the coming weekend there is no indication of any
well organized storms brewing. Only a scattered snow shower or two
is in the current forecast package for the Red River Basin... with a
hint additional snow possible along the South Dakota.. southern
Minnesota belt. Meanwhile... temperatures continue to linger a good
five degrees above long term normals.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 645 AM CST Mon Feb 20 2017

Very tricky set of TAFs, since there are a lot of aviation issues
to deal with...from fog to showers and thunderstorms, wind shifts,
and low level wind shear. Kept the mention of low level wind shear
at KBJI/KTVF, due to the low level jet focused most in these
areas. Model guidance has not been of much help recently in
regard to its cloud height forecasts, wanting to keep most of the
area in MVFR conditions today. However, outside of the dense fog
area in northeast ND, ceilings have been VFR. Therefore,
hesitant to bring MVFR conditions outside of possibly KDVL or
KGFK. If these lower ceilings seem more probable, later shifts can
adjust. The vsby at KDVL has increased, while KGFK has decreased.
There should be some bouncing around to these vsbys for a while
yet this morning. Otherwise, as the sfc low pressure system moves
thru by later today, winds will turn more westerly. The showers
will gradually end from west to east by this afternoon.

&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Dense Fog Advisory until 9 AM CST this morning for NDZ006>008-
     014>016-024-026>029-054.

MN...None.
&&

$$

UPDATE...Godon
SHORT TERM...Godon
LONG TERM...Godon/Gust
AVIATION...Godon



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