Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 230403
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
1003 PM CST Wed Feb 22 2017

.UPDATE...
Issued at 1003 PM CST Wed Feb 22 2017

The snow band moving through northern Wisconsin is resulting in a
period of low visibility. Increased the snowfall forecast a bit
and issued a special weather statement to communicate the threat
from this snow band.

Concerning the upcoming winter storm later this week, the latest
NAM trended much farther east, and came more in line with the
previous runs of the GFS, ECMWF, and Canadian. This finally gives
a jump in confidence that the accumulating snowfall, for our
forecast area, will primarily remain in northwest Wisconsin. There
was a push by NWS offices to update the forecast to reflect this
increase in confidence on the track and cut back on snowfall
chances and amounts on the western edges of the previous forecast.
The new forecast has cut back on snowfall for areas like the North
Shore, Duluth, and Aitkin areas.

UPDATE Issued at 550 PM CST Wed Feb 22 2017

Updated for the new 00Z Aviation Discussion below.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 330 PM CST Wed Feb 22 2017

A quick round of rain/snow this afternoon into the early evening,
with few rumbles of thunder and up to an inch of snow possible, but
precipitation comes to end quickly tonight. Some sunshine tomorrow
north of Highway 2 Thursday but otherwise mostly cloudy with
temperatures remaining above normal in the upper 20s (int`l border)
to mid/upper 30s.

On the synoptic scale a fairly impressive mid-level shortwave trough
is lifting east across central and northern Minnesota, with the PVA
induced by the vort max resulting in an area of moderate to heavy
precipitation and even a few rumbles of thunder with the marginal
instability. Rain will change over to snow fairly quickly from west
to east as these showers move through, with up to an inch of
snowfall possible towards the evening. Strong subsidence in the wake
of the mid-level disturbance will result in precipitation quickly
coming to an end this evening from west to east. Lows in the low 20s
to near 20, with some spots across the borderland falling to the
teens as skies clear out.

Skies are expected to at least partially clear late tonight towards
Thursday morning despite some guidance keeping a persistent stratus
deck around. However, towards the afternoon clouds will increase
from south to north ahead of the winter storm approaching from the
southwest.

.LONG TERM...(Thursday night through Wednesday)
Issued at 330 PM CST Wed Feb 22 2017

The winter storm for Thursday night through Saturday is the main
focus of this forecast. Forecast models are showing that our winter
storm is still on track to bring some significant snow to the
forecast area, mainly for northwest Wisconsin. The 12z runs of the
ECMWF and GFS are on a very similar track as they have for a several
runs, showing the main snow band across northwest Wisconsin with a
sharp gradient in the snowfall to the northwest.  The 12z NAM has
come in much farther to the northwest, with the heaviest snow band
all the way over the Arrowhead, barely overlapping the ECMWF/GFS
solution at all.  The 12z NAM brings the surface low much farther to
the northwest based on its position of the baroclinic zone in the
next 24 hours and the way it barely generates any convection over
Iowa overnight, instead producing precipitation farther northwest.
With the strong dynamics along the warm front ahead of the surface
low there should be more, as is better depicted by the GFS and
ECMWF.  Have pretty much discounted the 12z NAM for now, and the 18z
NAM doesn`t look much better. Am still seeing some differences in
even the GFS and ECMWF timing, track and phasing beyond 12z Friday,
but still a similar amount for snow amounts for the forecast area.

For now, have very high confidence in bringing snow into the
forecast area Thursday night, with the best dynamics over the
forecast area during the day on Friday before the whole system
bodily shifts northeast and out of the area by Saturday morning.
Snowfall amounts are still questionable since the NAM is so very
different, but given the current favoring of the GFS/ECMWF, I
currently have a broad stripe of heavy snow over much of northwest
Wisconsin.  Have expanded the current winter storm watch to the rest
of our northwest Wisconsin counties, and we will make the call
either tonight or tomorrow about warnings or advisories.

After the big winter storm, we have some potential for lake effect
snow Saturday night which comes to an end by Sunday as the winds
turn.  Another fairly strong storm system is going to affect the
southern plains Sunday night/Monday, but should not have much of an
effect here.  In the Tuesday-Wednesday time range there is another
interesting winter storm that may/may not affect the forecast area,
but the  ECMWF is certainly interesting.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 550 PM CST Wed Feb 22 2017

A passing upper-level disturbance will continue to result in a
period of snow, and rain transitioning to snow, across northeast
Minnesota and northwest Wisconsin this evening. The precipitation
will be shifting east. Expect a period of LIFR/IFR conditions from
the combination of low ceilings and reduced visibility in the
snow.

The precipitation will exit later this evening, but there will be
lingering IFR/MVFR ceilings overnight. However, it looks like
there will be a transition to back to VFR late tonight and
Thursday morning.


&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  24  33  20  26 /  90   0  10  30
INL  16  28  11  25 /  10   0   0  10
BRD  24  35  21  27 /  80   0  10  10
HYR  29  39  25  30 /  80  10  50  90
ASX  29  36  24  29 /  80  10  30  80

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Watch from Thursday evening through Saturday
     morning for WIZ001>004-006>009.

MN...Winter Storm Watch from Thursday evening through Saturday
     morning for MNZ038.

LS...None.
&&

$$

UPDATE...Grochocinski
SHORT TERM...JJM
LONG TERM...LE
AVIATION...Grochocinski



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