Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 261938

Area Forecast Discussion
National Weather Service Marquette MI
338 PM EDT MON SEP 26 2016

.SHORT TERM...(Today and tonight)
Issued at 501 AM EDT MON SEP 26 2016

Nam shows a 500 mb ridge on the west coast, a closed 500 mb low in
Baja California and a deep trough across the north central U.S. this
morning. Nam shows this upper trough heading slowly east and
reforming a closed low this morning. GFS and ECMWF show about the
same thing as well. Wraparound part of storm will continue to affect
the area through tonight and there will also be some lake
enhancement pcpn thrown in as well as 850 mb temperatures fall to 2C
to 4C today and stay there through tonight. With Lake Superior water
temperatures ranging from 15C to 17C, this is enough lake-850 mb
delta-t for lake effect pcpn and have some higher pops along the
lake shore to account for this. Overall, did not make too many
changes to the going forecast for temperatures or pops.

.LONG TERM...(Tuesday night through Monday)
Issued at 337 PM EDT MON SEP 26 2016

Attention remains focused on the first day or two of the long term
as the closed low shifts out of the area.

Models indicate that the low will be over south central Lake
Superior at 00Z Wed, which is a westward shift from previous runs.
This trend may slightly continue, but would think that models will
have a pretty good handle on the system at this point. The low will
shift to northern Lake Michigan by 06Z Wed, southern Lake Michigan
by 12Z Wed, then gradually shift to central or eastern KY by Thu

As the low shifts through and out of the area, the main hazards will
be gusty winds, high waves/beach erosion, and waterspout potential.
NE winds gusting to 30-35mph will gradually diminish over and near
Lake Superior Tue night into Wed, but winds will increase to 25-
30mph over and along northern Lake Michigan on Wed into Wed evening.
Winds will drive waves up to around 8` over western Lake Superior,
which may result in some minor beach erosion. As for waterspouts,
favored areas will be south central Lake Superior Tue evening and
Tue night then over northern Lake Michigan late Tue night into Wed.

Rain showers will be most focused over north central and western
Upper MI Tue night, transitioning to northern Lake Michigan Wed into
Wed evening as ridging moves in from the NW.

Challenge late in the week is how close does the upper low come to
the area as it moves back to the N from KY. The ECMWF bring it
across central Lower MI and Lake Huron this weekend into early next
week, while the GFS takes it across OH and Lake Erie. The ECMWF
solution brings chances for rain showers Fri through the weekend,
while the GFS confines any precip chances to the far eastern CWA.
With low confidence in the track of the low, stuck with the
consensus blend late week through day 7.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 142 PM EDT MON SEP 26 2016

A moist cyc upslope wnw flow wl bring predominant lo end MVFR
conditions to CMX/IWD this fcst period. IFR conditions are possible
at times, especially at IWD late as the flow veers more to the NW
and increases the overwater trajectory of the air into that site.
The downslope nature of the flow wl allow for hier end MVFR cigs to
prevail at SAW, but even there the cig is likely to drop into the
lower MVFR range by the early mrng hrs on Tue as lo pres now in
Ontario sinks into Lk Sup and draws closer. Gusty winds will also
continue thru this evng, especially at the more exposed CMX location,
where gusts aoa 35 kts are likely. The strongest winds will tend to
diminish later tngt into Tue with the closer approach of the Ontario
lo pres and a weakening pres gradient.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 501 AM EDT MON SEP 26 2016

Active pattern on the waters continues with a gale event across most
of Lake Superior today into Tue morning for most of the lake. Tight
pressure gradient/increasing instability behind a cold front will
cause gales into Tue morning. With the slow approach of high
pressure, these strong winds will diminish later Tue into Wed. This
high pressure will then bring light winds to end the week. Could be
some waterspouts on Eastern Lake Superior Tuesday through Tue night
and also across northern Lake Michigan and bay of Green Bay Tue

Upper Michigan...
Lake Superior...
  Gale Warning until 5 AM EDT Tuesday for LSZ243-244-264>266.

  Gale Warning until 11 AM EDT /10 AM CDT/ Tuesday for LSZ162-263.

  Gale Warning until 8 AM EDT /7 AM CDT/ Tuesday for LSZ240>242.

Lake Michigan...


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