Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 270715
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
315 AM EDT TUE SEP 27 2016

.SHORT TERM...(Today and tonight)
Issued at 315 AM EDT TUE SEP 27 2016

Upper air pattern consists of a 500 mb closed low north of Lake
Superior this morning. Nam takes the closed low south to southern
Lake Michigan by 12z Wed. Nam shows some 850-500 mb q-vector
convergence and deeper moisture remaining across the area through
this evening before the dynamics weaken and head south with the
upper low. Overall, did not make too many changes to the going
forecast. Interesting thing happened on Lake Superior though as the
western buoy dropped to 7C from 16C yesterday. The central and
eastern waters cooled about 2C from yesterday with the gale event.
With Lake Superior a bit cooler, this has helped to increase the
stability a bit and thinking is that the lake temperatures are
running from 12C to 15C and 850 mb temperatures will be around 4C,
so there is still enough lake-850 mb delta-t to get some lake
enhancement pcpn. Looked at thunder possibility and still looks like
there could be several hundred j/kg of cape to work with, so kept
isolated thunder mention in there. As for waterspouts, there is
still a small possibility even though the lake-850 mb delta-t has
decreased a bit from yesterday as the lake has cooled a bit. Enough
of a chance with the lighter winds in the east and in Lake Michigan
to keep a slight chance of waterspouts going.

.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
afternoon.

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 06Z TAFS through 06Z Tuesday night)
Issued at 121 AM EDT TUE SEP 27 2016

A slow moving low pres system will continue dominate the Upper Great
Lakes thru tonight. The resulting cyclonic upslope w to nw flow and
abundant moisture will lead to prevailing low MVFR cigs at KIWD/KCMX
thru this fcst period. IFR conditions are possible at times,
especially at KIWD as the flow veers more to the nw and increases
the overwater trajectory of the flow. At KSAW, the downslope nature
of the flow will allow for higher end MVFR cigs initially, but the
cig is still likely to drop into the lower MVFR range during the
early morning hrs as low pres now in northern Ontario sinks s and
draws closer. Gusty winds will also continue, more so at KIWD/KCMX,
and especially at the more exposed KCMX location, where gusts aoa
30kt are likely to continue thru the morning. However, winds will be
tending to diminish thru the day with the closer approach of the
Ontario low pres and a weakening pres gradient.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 315 AM EDT TUE SEP 27 2016

As low pressure over Ontario sinks slowly south and moves over Lake
Superior, the pressure gradient over the waters will continue to
slowly loosen and cause ongoing w gales to diminish under 30 kts
early this morning. There could be some waterspouts over the e half
of Lake Superior today into tonight under the slowly passing lo
pres. With the slow approach of trailing high pressure, the winds
will continue to slowly diminish into Wed. This high pressure will
then bring lighter e to ne winds under 20 kts to end the week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning until 5 AM EDT early this morning for LSZ243-244-
     264>267.

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

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

Lake Michigan...
None.
&&

$$

SHORT TERM...07
LONG TERM...Titus
AVIATION...Rolfson
MARINE...07



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