Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 091745

Area Forecast Discussion
National Weather Service Duluth MN
1145 AM CST Fri Dec 9 2016

.SHORT TERM...(Today through Saturday)
Issued at 357 AM CST Fri Dec 9 2016

Lake effect snow is on-going this morning due to a northwesterly
flow regime over Lake Superior. Plenty of snow was falling as we
received a report of 12.4 inches of storm total accumulation so
far in Gile, Wisconsin in Iron county, reported at 9:30 PM CST
Thursday. There was a very thin band of lake effect snow that
seemed to originate from Lake Vermillion in north central St.
Louis county. This band likely was enhanced thanks to Lake
Superior, which helped to bring abundant snowfall to portions of
Bayfield county.

This lake effect snow is expected to continue through the morning
hours as winds remain from the northwest. However, latest
GFS/NAM/HRRR models are progging 1000-850 mb winds to back to a
more westerly component, which should decrease lake enhancement.
Thus, we have bumped up the expiration times for the Lake Effect
Snow Warning and Advisories for Friday afternoon and early
evening, respectively. There could still be some lake enhancement
in northern Bayfield county from the westerly winds, but not
expecting much in the way of new accumulations.

Sfc high pressure and drier air, as indicated in 09.00z GFS/NAM
soundings, moves into the region late Friday through Saturday
morning. Skies will clear some during this time due to the drier
atmospheric profile, which looks to support some very cold
temperatures. 925 mb temperatures will drop as low as -20 degrees
C. Due to the clearing skies and very cold low-level thermal
profile, I decreased the consensus blend low temperatures
slightly for Saturday morning, with lows reaching the negative
single digits across NE MN and the single digits above zero for NW

Our next storm system will arrive late Saturday ahead of a push of
850-700 mb layer warm air and moisture advection from the
southwest. Kept slight chance/chance PoPs across our southwestern
most counties for Saturday afternoon as the storm system
approaches. Most, if not all, of the action from this system
occurs in our long term period.

.LONG TERM...(Saturday night through Thursday)
Issued at 212 AM CST Fri Dec 9 2016

Saturday night through Sunday night a fairly potent shortwave moves
from the northern Rockies east across the northern plains to the
Great Lakes.  A surface low develops over eastern Colorado, moving
east across Kansas to Iowa before turning northeast to move to Lower
Michigan by Sunday night.  The broad and strong baroclinic zone that
extends along this same path is going to produce a broad area of
precipitation that should affect the southern half of the forecast
area with a period of light snow beginning late Saturday continuing
through Saturday night and Sunday before tapering off late Sunday
night and Monday.  The forcing for this event appears strongest for
Iowa, southern Minnesota and Wisconsin, but we get enough isentropic
lift and frontogenesis up here for this to be a fairly high
probability but low QPF event.  Thus, we are looking at long
duration of light snow from Saturday night through Sunday night for
areas generally along and south of highway 2.  We are only looking
at event total snowfall amounts of 2-4 inches across the southern
CWA, to less than an inch towards the Canadian border.

Behind this system, we go into a fairly long period of northwest
flow with a strong upper low in the vicinity of Hudson Bay,
generally from Monday through at least Thursday.  This is going to
send a surge of much colder air into the region, with 850mb
temperatures sinking into the -20 to -30 range on Wednesday when the
coldest air gets into the area.  This is also going to send a series
of weaker shortwaves through the area to bring some short periods of
light snow.  Lake effect snow will also affect the south shore of
Lake Superior most of the week.  We are going to have some seriously
cold nights ahead of us beginning on Monday night through the end of
the work week.  In fact, as cold as the forecast is now, we will
have to evaluate each night carefully.  If we can set up a night of
good radiational cooling  conditions on top of the already cold
airmass, we could be another 5 to 10 degrees colder than current
forecast.  Incredible as it seems, this would not put us in record
territory most of this upcoming week, with records around -20.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1145 AM CST Fri Dec 9 2016

Cyclonic flow will continue across the Northland this afternoon
and tonight. This will combine with lift from a shortwave moving
southeastward from southern Manitoba to northern Lake Superior.
The result will be scattered snow showers this afternoon and
tonight. Expect ceilings to remain in the MVFR range between 1500
to 3000 feet for much of the forecast. In the heavier snow showers
expect visibilities to drop to MVFR/IFR range. More confident on
visibility reductions at KINL/KHIB per the latest observations
and the ARW/NMM/RAP.

Expect snow showers to come to an end at KDLH/KHIB/KBRD early
Saturday morning as high pressure nudges into the region. The
drier air advecting into the region aloft may be enough to scatter
skies out to VFR.


DLH  13  -1   8   6 /  10  10  10  40
INL  10  -6   5  -2 /  30  20  10  20
BRD  11  -4   9   7 /  10   0  30  60
HYR  16   2  12   8 /  10  10  10  50
ASX  18   6  12  10 /  30  20  10  30




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