Area Forecast Discussion
Issued by NWS Duluth, MN

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000
FXUS63 KDLH 022326
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
526 PM CST Fri Dec 2 2016

.UPDATE...
Issued at 517 PM CST Fri Dec 2 2016

updated aviation section below.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 320 PM CST Fri Dec 2 2016

The Northland`s light northwest flow will continue into tonight,
especially aloft, while the axis of a subtle ridge of high
pressure shifts into Northland from the west. Ample cloud cover
upstream in Canada is giving good confidence the current overcast
cloud cover will continue overnight, as suggested by the HRRR,
local WRF, and 4 km NAM. The cloud cover will bolster the
overnight temperatures, despite the very light winds speeds later
tonight that tend to favor good radiational cooling, so refrained
from the colder model guidance. Leaned on a blend with lows
ranging from the middle 20s over northwest Wisconsin and low 20s
across northeast Minnesota.

There are low chances of very light snow and patchy freezing
drizzle across small portions of the South Shore, mainly along
west/north side of the Bayfield Peninsula, due to the cold flow
over Lake Superior.

Light, southerly return flow will develop Saturday in the wake of
the passing ridge of high pressure. There should be lingering
broken/overcast low-level cloud cover. Highs should reach the
upper 20s to near 30 degrees.

.LONG TERM...(Saturday night through Friday)
Issued at 320 PM CST Fri Dec 2 2016

A shot of snow showers is possible Saturday night and Sunday
morning as a sharp shortwave trough and associated maximum of
positive vorticity advection will move through the forecast area.
Enhanced low- level convergence will also help to provide the lift
to support snow, which should stay fairly light, with
accumulations between 1-2 inches. Most of the snow will fall
Sunday morning between 12-18z. Bumped up PoPs to categorical along
our southern most tier of counties as the mid-level isentropic
lift is maximized in this area. QPF signals in the synoptic models
also appear to be maximized in this area. Chances of snow will
tapper off Sunday evening and overnight as the shortwave
translates to the east.

Monday morning looks to be dry at this point as the 850-500 mb
layer dries up, according to the GFS/NAM model soundings. A low-
level inversion does develop during this time, which will keep the
low levels fairly moist. A sfc low pressure system then moves in
from the west. There is some uncertainty at this point regarding
chances of precipitation from this system as the GFS is lingering
some measurable precipitation from Tuesday through Thursday, while
the ECMWF has the low pivoting north, keeping the moisture further
north. The CMC model seems to be in better agreement with the
ECMWF, so I lowered the PoPs to better match what the guidance is
leaning towards. After this initial wave moves through, cold air
advection plows into the region. Models indicating 925 mb
temperatures aloft as low as -17 degrees C. This should support
temperatures near or below seasonal averages, with lows in the
teens and single digits Thursday through Saturday.

Tuesday night through Wednesday looks to be mostly dry before
another wave sweeps through from the north. This wave looks to
keep a slight chance of snow around through Friday morning before
moving out Friday evening, except for the Lake Superior snowbelt.
GFS soundings indicate some saturation in the dendritic growth
zone, along with steepening low level lapse rates, so expanded the
pops from what the consensus blends were giving.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 517 PM CST Fri Dec 2 2016

MVFR ceilings with some IFR ceilings are expected to continue
through approximately 18z-21z, with a gradual improvement to
VFR, but with cloud bases still in the 3-5kft range. Flurries
possible, but since timing and location uncertain have left even
VCSH out of terminals for now. Light northwest winds to continue
overnight, then slowly veer to southwest after 15z.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  25  29  24  33 /  10  10  40  50
INL  23  28  23  33 /  10  10  30  50
BRD  22  29  27  35 /  10  10  40  40
HYR  25  31  24  35 /  10  10  30  70
ASX  29  33  25  36 /  10  10  30  50

&&

.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&

$$

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



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