Area Forecast Discussion
Issued by NWS Grand Forks, ND

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FXUS63 KFGF 200401
AFDFGF

Area Forecast Discussion
National Weather Service Grand Forks ND
1001 PM CST Mon Feb 19 2018

.UPDATE...
Issued at 951 PM CST Mon Feb 19 2018

Light snow continues to move in from the southwest, with more seen
upstream all the way down to the Nebraska panhandle and
northeastern Colorado. Amounts so far have been pretty light, but
short range models as well as the 00Z NAM are pretty consistent on
bringing in another surge of moisture into the southeastern CWA
later tonight. There is some mid level frontogenesis, so several
tenths of an inch of QPF will be possible later tonight. The
question is just how much and if the second round follows the same
track as the first and leads to more accumulation. At this point,
running the expected QPF based on the blend of short range models
along with snow ratios near 20:1 gives snow amounts generally in
the 4 to 6 inch range across the current advisory area, with a few
spots over 6 inches. Still not confident enough to upgrade to a
warning, but will keep an eye on things for the next couple of
hours. Bumped up lows a few degrees as with clouds we are not
falling off as much as expected in the west.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 325 PM CST Mon Feb 19 2018

Not much change for this forecast period from our previous
package. Some light snow or flurries continue to brush some of
our westcentral MN counties this afternoon while clouds thicken
and lower over southeast ND... in advance of a more significant
moisture surge still working its way up through central SD. A hint
of the likely deformation band is currently setting up in an arc
from northeast SD into westcentral MN.

Model guidance is fairly consistent on placing band of QPF over
the tri-state border area in the 0.25 to 0.40 inch range. With
snow ratios likely to push from 18:1 to 22:1 through the period
there should be an area pushing 6 inches of snow or a bit more,
from near Aberdeen... through Fergus Falls... and past Park
Rapids. Heaviest snowfall there links peak moisture advection
with coolest boundary layer temps... from just after midnight
through Tuesday morning drive time.

For now... its looks as if the Lisbon-Fargo-Bemidji Line is
setting up as the north edge of that heavier (3 to 5 inch)
snowfall range, with snowfall likely to taper off fairly sharply
north of that line. Will remain to be seen if the heavier snow
band shifts further north as some of the HRRR runs show a bit of
variability. Thus have stuck with previous Winter Weather Advisory
outline and timing, but have split out the southern portion to
indicate the somewhat higher snowfall potential there.

System exits the area a bit more slowly on Tuesday than the
previous system, so some lingering low clouds and snow flurries
are likely after midday. Northwest winds will increase in the
late forenoon and afternoon, so some blowing and drifting is to
be expected in open areas.

.LONG TERM...(Tuesday night through Monday)
Issued at 325 PM CST Mon Feb 19 2018

Clearing skies and fresh snow will lead to a cold night on Tuesday
with dangerous wind chills. After this cold night a warming trend is
present through Sunday, with temperatures from Thursday through the
weekend temperatures near normal.

High pressure dominates until Thursday when the next chance for snow
arrives. An upper level trough and its associated surface low will
provide some light accumulating snow. There is fairly good agreement
between the GFS and ECMWF for this event. The best snow chances will
be from southeast North Dakota to north central Minnesota. High
pressure returns Friday into the weekend. There is still a clipper
passing nearby in the GFS in around Sunday but the ECMWF and CMC
have a different evolution in this period so there is significant
uncertainty.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 723 PM CST Mon Feb 19 2018

Ceilings are currently VFR across the forecast area but will begin
to deteriorate overnight. Conditions will drop to MVFR during the
06 to 12Z time frame as more moisture moves in from south along
with a band of light snow. The snow band will produce visibility
down to 1-2SM at times across all but KDVL. Think the heaviest
snow with vis below 1SM will stay to the south and east of TAF
sites. Snow will taper off by mid-day tomorrow and conditions will
improve to VFR at KDVL and KFAR by the end of the period. Winds
will be from the north at 10 to 15 kts, becoming northwest by
tomorrow afternoon.


&&

.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Weather Advisory until noon CST Tuesday for NDZ038-039-
     049-052-053.

MN...Winter Weather Advisory until noon CST Tuesday for MNZ002-003-
     009-015>017-022>024-027>032-040.

&&

$$

UPDATE...JR
SHORT TERM...Gust
LONG TERM...NC
AVIATION...JR



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