Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 300001
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
701 PM CDT WED JUN 29 2016

.UPDATE...
Issued at 643 PM CDT Wed Jun 29 2016

Update for new aviation section below. Have made some adjustments
for the timing of the convection as the front slowly slides
southeast through the area tonight.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 316 PM CDT Wed Jun 29 2016

After a mild day with highs approaching 80 a cold front moving from
north to south across the region will result in a chance for showers
and thunderstorms this afternoon through tomorrow, with cooler
temperatures and breezy winds behind the front. Not expecting any
severe thunderstorms because of the amount of instability and poor
wind fields aloft to sustain storms, though these pulse storms have
a tendency to produce gusty winds as they quickly develop and
dissipate.

On the synoptic scale a fairly strong trough axis associated with an
upper low over Hudson Bay will swing south across the Canadian
Prairie today, reaching the upper Midwest Thursday. A cold front well
ahead of trough is gradually moving south across southern Manitoba
and northwest Ontario this afternoon and will cross the
international border in northern Minnesota late today. This will
result in an area of showers and storms along and ahead of the
front, with precipitation expected to decrease in coverage overnight
as the front moves southeast across northeast Minnesota. However,
towards Thursday morning activity is expected to pick up again as
the PVA from the approaching trough axis results in much better
large-scale lift. This combined with a bit of elevated CAPE will
result in showers and a few thunderstorms increasing in coverage by
mid-morning across east-central Minnesota into northwest Wisconsin.

By Thursday afternoon this front will accelerate out of the CWA as a
strong area of high pressure builds in over the northern Plains
behind it. At least partially clearing skies are expected behind the
front in north-central to northeast Minnesota Thursday afternoon
with surface heating combined with strong low level winds resulting
in some breezy winds at the surface with peak gusts approaching 20
knots. In the post-frontal environment isolated showers will also be
possible due to the instability introduced by seasonably cool air
aloft. Highs cooler Thursday in the mid 60s to near 70.

.LONG TERM...(Thursday night through Wednesday)
Issued at 345 PM CDT Wed Jun 29 2016

The main concern for this package is uncertainty regarding
thunderstorm chances over the holiday weekend.

Closed upper low over James Bay Thursday evening is expected to
slowly progress southeastward through Saturday night, with a
building ridge to the west of the Northland. Surface high pressure,
in concert with the building ridge, will result in quiet conditions
across the Northland Thursday night through Friday night.

Model solutions begin to diverge Friday night as the upper trough
rotates farther eastward into New England. The differences are
subtle initially with the ECMWF picking up the baton from
yesterday`s 12Z GFS and bringing a compact shortwave and vorticity
max southeast across the area and along an advancing warm front.
Meanwhile, the NAM/GFS/GEM are weaker with the feature with
differing placement. This general signal has been found in the
deterministic guidance, with differences in the details, for the
past 8 to 10 model runs. Continuing to carry low POPs in north-
central Minnesota for Saturday with thunderstorms mentioned. Just
not enough confidence with the run-to-run and model variability to
justify going dry.

The pattern shifts beginning Saturday night toward a quasi-
zonal/southwest flow regime for the remainder of the weekend and
into Tuesday. In typical late June/early July fashion, much of the
details regarding thunderstorm chances, cloud cover, and
temperatures during the upcoming holiday weekend will be governed by
convective evolutions across the Northern Plains and Canadian
Prairies. Again, details vary from model-to-model and even run-to-
run. Signal for at least some thunderstorm potential has been
present during the past several days. Given climatology factors plus
the variability in the guidance, think maintaining thunderstorm
chances is the right decision today. A warm front will be located
somewhere in the region for much of the weekend, with subtle, low
amplitude impulses propagating along the boundary. Instability and
wind fields don`t support much of a risk of severe storms, but have
to believe it is no-zero. Potential exists for one or several storm
complexes to fire near the warm front over the Plains and propagate
eastward toward the western Great Lakes each afternoon, likely aided
by strengthening low-level jet during the overnights. Since
forecasting trajectories of these features even in the 6 to 12 hour
timeframe is difficult at best, opted to broad brush storms through
the weekend through Tuesday night.

Temperatures through the period will trend near to slightly below
seasonal averages. Look for highs in the low to middle 70s Friday
and warming into the upper 70s to low 80s by Monday and Tuesday.
Lows are expected to range from the upper 40s to low 60s.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 643 PM CDT Wed Jun 29 2016

A cold front will slowly slide southeast across the area through
18z Thursday. It will bring a period of showers and a few
thunderstorms to each of the terminals in turn...and have focused
on a 3-6 hour period of time where storms are most likely...and
have kept mainly to a VCTS group with tempo groups for MVFR
visibilities and ceilings. Will have to adjust timing as the
convective trends develop. Behind the front a gradual return to
VFR conditions are expected.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  56  68  48  71 /  60  60   0   0
INL  55  65  45  73 /  90  10   0   0
BRD  57  71  49  74 /  50  20   0   0
HYR  56  71  49  72 /  50  80   0   0
ASX  55  69  50  71 /  50  70  10   0

&&

.DLH Watches/Warnings/Advisories...
WI...None.
MN...None.
LS...None.
&&

$$

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



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