Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 211235 AAB
AFDDLH

Area Forecast Discussion...UPDATED
National Weather Service Duluth MN
735 AM CDT Mon Aug 21 2017

.UPDATE...
Issued at 735 AM CDT Mon Aug 21 2017

Please see the new 12Z Aviation Discussion below.

UPDATE Issued at 627 AM CDT Mon Aug 21 2017

A batch of showers has quickly developed over Pine county,
southern Douglas, Burnett and Washburn counties. Added pops into
these areas to account for the showers. A rumble of thunder is
also possible as MUCAPE is about 250 J/kg. Made some adjustments
to account for this activity.

&&

.SHORT TERM...(Today through Tuesday)
Issued at 337 AM CDT Mon Aug 21 2017

A fast quasi-zonal flow aloft covered the forecast area at 08Z while
high pressure was in charge at the surface. A mix of mid and high
clouds were streaming over the area in advance of several embedded
impulses moving along in the fast flow. Some patchy fog had also
formed. The additional cloud cover arriving from the west may limit
the overall extent of anymore fog forming. The models offer
different solutions on how the morning evolves and if any showers
develop and affect the region. Used a blended approach to pops which
led to some pops over southern Price county by mid morning. This is
in response to the impulse in eastern SD at this moment. A second,
stronger impulse moves through the southern portion of the forecast
area in the afternoon. The short term hires models attempt to keep
this area from much in the way of precipitation in northwest WI.
Meanwhile, the deterministic models are more bullish on QPF.
Attempted a blend here as well which led to higher pops over the
southeast corner of the region in the late afternoon. Unfortunately,
with these impulses moving through the area, this will lead to an
expansive cloud cover right at eclipse time.

A vigorous long wave trof will drop south out of Canada tonight and
across the region. A strong cold front will accompany this trof.
850mb temps will drop from the teens celsius ahead of the front/trof
to the single digits behind the front. Look for showers and
thunderstorms over northwest WI in the evening, diminishing
overnight as the cold front departs. Lower pops farther north
tonight as dry air is advected into the northern half of the region
as the strongest impulse in the base of the upper trof moves quickly
east of the area. A fairly tight pressure gradient will be found
across the area tonight with the cooler temps making it feel very
fall-like.

Model differences prevail once again on Tuesday. A surface trof is
progged to clip the northern third of the forecast area in the
afternoon. The NAM/GEM/ARW/NMM/GFS are all dry, but the ECMWF brings
a swath of QPF into the border region as a channeled area of
vorticity slides into the area. The pops across the north
acknowledge the ECMWF solution, with some weight to the other
models.

.LONG TERM...(Tuesday night through Sunday)
Issued at 337 AM CDT Mon Aug 21 2017

Temperatures trend a bit cooler for the start of the long term,
moderating through the end of the week, with a few chances of
showers and thunderstorms.

Tuesday evening will see a stout upper trough over eastern
Canada, portions of the Great Lakes, and New England. Several
shortwave disturbances will be found rotating around the closed
low over northeast Ontario and western Quebec. Another shortwave
trough will approach from upstream and kick the closed low
farther east Tuesday night and Wednesday. That disturbance will
move out of southern Manitoba and into northern Minnesota during
the day Wednesday, and may provide enough lift for a few isolated
showers or maybe a thunderstorm. Temperatures aloft will be
somewhat chilly for late August with 850 mb values in the middle
single digits Celsius Wednesday afternoon and Wednesday evening.
The cool temperatures aloft and cloud cover associated with the
transient wave should yield afternoon highs in the 60s over the
Northland.

High pressure returns in the wake of the passing shortwave trough
bringing mostly sunny to partly cloudy skies to the area and
gradually moderating temperatures. Quiet and mostly sunny
conditions are expected Thursday through Friday afternoon.
Deterministic guidance then diverges with the handling of the
next shortwave trough for Friday afternoon through Saturday
night. The ECMWF brings clouds and precipitation into the
Northland as early as Friday afternoon, while the CMC and GFS are
a bit slower. All three models slow the forward progression of
the shortwave due to a deepening trough downstream over Quebec
and New England. The consensus of the guidance keeps a chance of
rain in the picture for much of the weekend. Think that`s the
right call with this update and have broad-brushed slight and low-
end chance POPs across much of the Northland for the weekend into
Monday. Temperatures will trend near normal Friday through Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 735 AM CDT Mon Aug 21 2017

Scattered showers will affect the Northland today as a trough of
low pressure aloft moves through the region. A broken line of
thunderstorms over central Wisconsin, southern Minnesota, and
northern South Dakota may eventually drift northward toward HYR
and BRD this afternoon. Otherwise, mainly VFR conditions are
expected outside of the showers. Areas that receive rain today
should see some fog development overnight, but left any explicit
mentions of lower visibility out of the forecast for now due to
low confidence in timing/location.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  74  53  71  50 /  30  20  10   0
INL  74  49  70  47 /  20  20  20   0
BRD  73  53  72  50 /  30  10   0   0
HYR  78  54  71  49 /  40  50   0   0
ASX  77  55  72  51 /  40  40  10   0

&&

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

$$

UPDATE...GSF
SHORT TERM...GSF
LONG TERM...Huyck
AVIATION...Huyck



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