Area Forecast Discussion
Issued by NWS Duluth, MN

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464
FXUS63 KDLH 071203
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
603 AM CST Wed Dec 7 2016

.UPDATE...
Issued at 600 AM CST Wed Dec 7 2016

Updated aviation section below.

&&

.SHORT TERM...(Today through Thursday)
Issued at 336 AM CST Wed Dec 7 2016

A vertically stacked area of low pressure will continue to move
through the region this morning, and eventually translate to the
east later today into tonight. Winds will slowly veer to the
northwest through the day Wednesday as the low pressure moves away
and should remain gusty as a tight sfc pressure gradient persists.
Thanks to the cyclonic flow aloft, and cold temperatures in the
low levels, scattered snow showers should remain over the
Northland on Thursday morning. RAP/NAM/GFS model soundings
indicate saturation within the -12 to -18 degrees C dendritic
growth zone, along with some decent mid-level isentropic ascent
which should support these snow showers.

As the winds veer to the northwest, this looks to set up a likely
potential for lake-effect snow along the south shore of Lake
Superior over northwestern Wisconsin. The isentropic lift profile
looks favorable for lake effect in this area, along with strong
delta-T values between the lake temperatures and the 850 mb
temperatures, with values ranging from 18 to 22 degrees C from
Wednesday night through Thursday morning. This looks like a
favorable set up for significant snow accumulations, especially in
Iron county, and modest accumulations in Ashland and Bayfield
counties. Thus, we have upgraded the Lake Effect Snow Watch to a
Lake Effect Snow Warning for Iron county, and a Lake Effect Snow
Advisory for Ashland and Bayfield counties, which are in effect
through the day Friday.

.LONG TERM...(Thursday night through Tuesday)
Issued at 336 AM CST Wed Dec 7 2016

Cyclonic, northwest flow continues over the area Thursday night
through Friday night.  The strength of the low level winds gradually
weakens through this period, but there is enough moisture and lake-
850mb temperature difference to keep the lake effect snow machine
going through the period.  Backing winds and diminishing speeds
should finally cut it off for our forecast area by early Saturday
morning.  Thus, we have the lake effect snow warning going through
Friday night to best capture all of the accumulating snow.
Temperatures through the period will be well below normal, and for
areas away from Lake Superior have gone below zero for any area that
breaks out of the clouds overnight.  Daytime high temps to stay on
the cold side as well with highs only in the teens and high single
digits most locations.

Saturday begins our next accumulating snow event as an upper level
trough sweeps across the plains Saturday through Sunday.  A surface
low should develop in the vicinity of western Kansas and then move
northeast across Iowa and to lower Michigan by Sunday.  The GFS is
much stronger than the ECMWF with this wave and actually develops
this surface low while the ECMWF is weaker both aloft and at the
surface has little more than an inverted trough.  Ensembles support
a stronger solution, and have favored the stronger GFS solution,
though have kept some ECMWF as well.  It appears there should be
some lingering lake effect going into early Monday,

Once this system pulls off to the east early next week will be cold
and mostly dry, with some weak shortwaves to produce some snow
showers mainly on Monday.  The surface ridge builds into the area
more on Tuesday and Wednesday, which should quiet down most snow
shower activity.  We can still expect some lake effect snows for the
south shore with very cold air aloft, northwest flow and lake
temperatures remaining mild for this time of year.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 600 AM CST Wed Dec 7 2016

Strong northwest winds combined with snow showers for much of the
next 12-18 hours will produce poor visibilities in snow and
blowing snow, with IFR to even LIFR conditions, with MVFR
ceilings. This to affect most terminals, with a gradual
improvement to at least MVFR expected after 00z this evening as
winds finally diminish and snow showers become less widespread.
MVFR ceilngs expected to continue through remainder of TAF period.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  22  19  23   8 /  40  40  30  10
INL  27  19  19   3 /  80  50  30  10
BRD  18  16  19   5 /  40  40  20  10
HYR  21  19  25   9 /  40  40  40  20
ASX  25  21  28  15 /  40  60  50  80

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Lake Effect Snow Warning from midnight tonight to 6 AM CST
     Saturday for WIZ004.

     Lake Effect Snow Advisory from midnight tonight to 3 PM CST
     Friday for WIZ002-003.

MN...None.
LS...Gale Warning until 6 PM CST this evening for LSZ121-143>148.

     Small Craft Advisory from 9 AM this morning to 6 PM CST this
     evening for LSZ140>142.

     Gale Warning until 9 AM CST this morning for LSZ140>142.

&&

$$

UPDATE...LE
SHORT TERM...JTS
LONG TERM...LE
AVIATION...LE



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