Area Forecast Discussion
Issued by NWS Duluth, MN

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FXUS63 KDLH 261134
AFDDLH

Area Forecast Discussion
National Weather Service Duluth MN
634 AM CDT Wed Jul 26 2017

.SHORT TERM...(Today through Thursday)
Issued at 315 AM CDT Wed Jul 26 2017

As of 08z this morning, very little activity was observed on radar,
with only a few showers over northwest Wisconsin as the cold front
boundary slowly makes its way southward. The current position of the
cold front is roughly from the Twin Ports and southwestward towards
Lake Mille Lacs. The bulk of the stronger activity is over central
Minnesota and central Wisconsin where the better instability
resides. The latest convective-allowing model output shows some
disagreement regarding the areal coverage of any showers and storms
over northwest Wisconsin. The HRRR model, along with the WRF NMM and
RAP models, appear to be a bit too bullish with progging showers
later this morning as they are over-doing what is currently observed
on radar. The best guidance appears to be the NAMNest, so leaned
more toward this guidance for the forecast. Patchy fog this morning
should dissipate by mid-morning as skies become partly to mostly
sunny.

As the cold front boundary moves southward, there could be more
showers developing, with a thunderstorm or two possible, with the
highest confidence over Price county in Wisconsin. As the front
passes, winds will turn more northwesterly. Due to these northwest
winds, there is the potential for downslope heating along the North
Shore, mainly from Duluth to Taconite Harbor. I did increase the
temperatures slightly over the North Shore because of this. Today`s
highs should be in the upper 70s to lower 80s. Moreover, dew point
temperatures in the lower to mid 60s through the day today will
keep conditions humid, especially over northwest Wisconsin. The
high pressure should remain in control overnight tonight, leading
to another night of some patchy fog possible as winds become light
and skies become mostly clear, especially over the Brainerd Lakes
area and points north and east.

A mid- to upper-level shortwave trough will then dive southeastward
from southern Manitoba Thursday morning and afternoon, which should
support at least a chance of showers and storms over the Minnesota
Arrowhead region. The Thaler QG 850-300 mb layer omega values
indicate some decent lift associated with the shortwave. The main
questions regarding precipitation chances are due to a lack of
moisture in the low-levels as seen in the GFS/NAM model soundings,
which could inhibit precipitation amounts. Some instability is
progged by the GFS/NAM models for Thursday afternoon, with modest
MLCAPE values up to 1000 J/kg over the Arrowhead, so if anything
materializes, thunderstorms will be possible. However, severe
weather is not expected with this system. This activity could
linger into the evening, but there`s some uncertainty on this as
the better lift moves off to the east.

.LONG TERM...(Thursday night through Tuesday)
Issued at 315 AM CDT Wed Jul 26 2017

A digging upper level short wave trof will be dropping over the
forecast area Thursday night and then closing off as it exits the
area by 12Z Friday. Moisture is lacking ahead of the trof, but
increases behind the trof. With this lack of moisture and the best
forcing ahead of the trof, not expecting any rain Thursday night.
Meanwhile, high pressure will be covering the region. Upper level
and surface ridging are in place over the region Friday and linger
through Saturday. Model differences show up Saturday night. The
upper flow transitions from ridging to northwest flow with embedded
pieces of short wave energy moving through the area. At the surface
is where the differences become pronounced. The ECMWF, and to a
lesser extent the GEM, have high pressure in control. The GFS
decides to drop a cold front into northern Minnesota with showers
and storms. Using a blend resulted in low pops over the northwest
third of the forecast area. These differences continue Sunday and
Sunday night. The ECMWF keeps things dry with the high pressure in
charge. The GFS/GEM march the cold front through the region with
showers and storms. Using a blend results in low pops to acknowledge
the front while giving the dry ECMWF forecast some weight.
Maintained the blended approach for Monday and Tuesday to resolve
differences in the handling of showers and storms with the potential
of fast moving impulses in the northwest flow.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 634 AM CDT Wed Jul 26 2017

A cold front was moving through northeast Minnesota at the start
of the forecast. Northwest wind and VFR behind the front. MVFR
with pockets of showers and BR ahead of the front with a
southwest wind at HYR. It will take until afternoon for the front
to move past HYR. However, ceilings should improve to VFR at HYR
fairly quickly this morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
DLH  80  59  76  55 /   0  10  20   0
INL  78  55  79  53 /   0  10  20   0
BRD  80  59  80  57 /   0   0   0   0
HYR  82  58  79  52 /  30   0  10   0
ASX  83  58  76  52 /  10   0  20   0

&&

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

$$

SHORT TERM...JTS
LONG TERM...GSF
AVIATION...GSF


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