Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 181548 AAB
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
948 AM CST Sat Feb 18 2017

.UPDATE...
Issued at 948 AM CST Sat Feb 18 2017

Fast-moving impulse that is now located to the east of Lake
Superior as of mid-morning amplified rather considerably overnight
while sliding eastward along the Canadian Border region of
northern Minnesota. In it`s wake, rather strong WNW flow is
persisting in the lower to mid levels, with almost 40 knots of
flow just above the morning/frontal inversion on the KINL 12z
sounding. This is also supporting cold advection in the lower
troposphere across the Border Region and the Arrowhead. However,
the airmass farther south across most of the remainder of the
Duluth CWA remains largely unchanged (i.e. very warm) this
morning. Given that we still have rather strong west/southwest
flow near the surface, nearly full sun, a very warm airmass and
the lower forest albedo effects, we have raised high temps across
the board for today as we are already starting out in the
mid/upper 30s in many locations, and it shouldn`t bee too much
trouble to rise another 15 degrees or so, if not more. We are a
bit concerned that a 2-4 degree raise may not still be sufficient
in some locations, especially over the south sections of the CWA
where large bare spots are opening up in the snow cover, and also
possibly over the interior northeast, where the forest sun
absorption effects are largest. Winds should remain somewhat gusty
across the Arrowhead and adjacent areas of the North Shore until
mid-late afternoon when the gradient weakens and pressure rises
wane. Updates to reflect the above reasoning have already been
made available.

In addition, there is an updated aviation discussion below.

&&

.SHORT TERM...(Today through Sunday)
Issued at 246 AM CST Sat Feb 18 2017

The dry and well-above average temperatures look to continue
through the short-term forecast period. Mostly clear skies
continued this morning across much of the region as a dry air mass
remains situated overhead, along with mid- to upper-level
ridging. The 18.00Z GFS/NAM models are indicating another sunny
day across the Northland Saturday, although some high clouds could
develop, especially in the afternoon. Much like Friday, high
temperatures are expected to be well above normal again for
Saturday. Much of the latest guidance seems much too low for
temperatures, so bumped up highs Saturday quite a bit higher, with
highs in the upper 40s and lower 50s expected for much of the
Northland. Conditions should remain dry as a surface high pressure
ridge advances through the region this evening and overnight.
With another day of additional melting of the snow pack, model
soundings are indicating a shallow moist boundary layer developing
tonight. With dewpoint depressions near zero, and decreasing
winds due to the surface high pressure ridge passage, areas of fog
are expected to develop late Saturday night, persisting through
Sunday morning. Some of the guidance is progging visibilities for
portions of the Northland as low as one- quarter of a mile, but
other guidance doesn`t seem quite as bullish on dropping that low.
For now, will maintain areas of fog across the Northland.

Another above-average temperature day is expected for Sunday as
mid-level ridging continues. Any fog that develops early Sunday
morning should dissipate by mid to late morning as temperatures
increase. Model soundings indicating mid to high clouds to
develop. This could prohibit temperatures from getting warmer than
Saturday`s temperatures, despite slightly warmer 925 mb
temperatures progged for Sunday. Still, highs in the upper 40s to
lower 50s are looking likely.

.LONG TERM...(Sunday night through Friday)
Issued at 237 AM CST Sat Feb 18 2017

An upper-level ridge will be over the forecast area Sunday night
while high pressure over the western Great Lakes drifts off to the
east. Meanwhile, an upper level long wave trof will be crossing
the Rockies, with a surface low organizing in the western Dakotas.
With the tightening pressure gradient, mixing will occur to the
surface and preclude any fog formation and have removed. Model
differences in the onset of the rain into the western portion of
the area shows up overnight. The ECMWF is dry, the NAM/GEM are too
fast and wet, the GFS is pointing toward some light QPF
developing. Went with a blend and have small POPs over the
western third of the region. On Monday, the long wave trough
moves into the eastern Dakotas, while the surface low lifts north
into southern Manitoba. The rain overspreads the forecast area
through the day. Models have backed off on the amount of CAPE
available and have removed the mention of thunder as a result.
There is a chance of some light freezing rain Monday morning east
of Ely and through the Arrowhead. The surface low continues on
its northerly trek through Manitoba Monday night. Meanwhile, the
long wave trough pushes into the forecast area. Temperatures will
be warm enough for rain, which will begin to diminish late Monday
night. The long wave trough and surface low finally exit the
region on Tuesday. Model differences show up Tuesday night with
the approach of a low pressure system that will move along the
Canadian border. This signals a change in the overall pattern from
warm to cold and the return of a winter pattern. POPs will be
aligned along the northern third of the forecast area Tuesday
night through Wednesday evening as the surface low moves along the
border. A rain/snow mix is expected with the diurnal fluctuation
in temps. A break from the precipitation comes late Wednesday
night through Thursday morning as high pressure moves nearby.
Model differences with the timing of the next round of
precipitation and the overall coverage begins Thursday afternoon
through Friday. Regardless, a good size weather maker is due to
affect the region. Will see mixed rain and snow Thursday afternoon
and evening before changing to all snow overnight. Overall QPF
coverage and amounts are in question this far out and have used a
blend.

&&

.UPDATED AVIATION...(For the 12Z TAF updates through 12Z Sunday
morning)
Issued at 948 AM CST Sat Feb 18 2017

The 12z KINL sounding and KDLH VWP reveal that winds just off the
surface within the morning/weak frontal inversion are stronger
than previously expected. Thus, we have re-introduced low level
wind shear at all terminals through late this morning, with west-
northwest winds between 30-40 knots 1500-2000 AGL persisting in
that layer. These winds should decrease/mix by around midday as
the disturbance producing them continues to move off to the east.
The remainder of the forecast reasoning and confidence is
unchanged, VFR conditions until the chance for fog later tonight
and Sunday morning, dropping flight conditions into the MVFR
(high confidence) or possibly IFR (lower confidence) category.

&&

.CLIMATE...
Issued at 850 AM CST Sat Feb 18 2017

Record Highs for February 18...

Duluth................ 53 in 1981
International Falls... 49 in 1954

Record Warmest Lows for February 19...

Duluth................ 35 in 1930
International Falls... 32 in 2016

Record Highs for February 19...

Duluth................ 51 in 1930
International Falls... 47 in 1994

Record Warmest Lows for February 20...

Duluth................ 33 in 1954
International Falls... 32 in 1915

Record Highs for February 20...

Duluth................ 54 in 1877
International Falls... 48 in 1990

Record Warmest Lows for February 21...

Duluth................ 33 in 1878
International Falls... 29 in 1981

Record Highs for February 21...

Duluth................ 57 in 1877
International Falls... 50 in 2000

Record Warmest Lows for February 22...

Duluth................ 35 in 1930
International Falls... 32 in 1998

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  51  30  47  35 /   0   0   0  10
INL  46  27  45  35 /   0   0   0  10
BRD  51  30  52  41 /   0   0  10  20
HYR  52  29  50  38 /   0   0   0  10
ASX  53  31  50  35 /   0   0   0  10

&&

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

$$

UPDATE...Miller
SHORT TERM...JTS
LONG TERM...GSF
AVIATION...GSF
CLIMATE...Mokry/Howell/Huyck



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