Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 271935
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
335 PM 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...(Wednesday night through Tuesday)
Issued at 332 PM EDT TUE SEP 27 2016

High pressure building in from the northwest Wed night and Thu
should end showers and allow for decreasing clouds. The NAM and GFS
soundings indicate that there could be some near sfc moisture
trapped beneath strengthening subsidence inversion Wed night into
early Thu which could maybe lead to some stratus formation for
locations favored by upslope ne flow. Models indicate there should
be enough wind/mixing to preclude fog formation so removed patchy
fog for western counties Wed night into early Thu. Cut-off mid-upper
level low pressure system remaining nearly stationary over the TN
River Valley should maintain dry conditions through Fri. Expect mins
Wed night and Thu night to range from lower 40s interior west to mid
50s near Lake Superior in onshore ne flow. H85 temps of 7-8C should
support inland max temps mainly in the mid to upper 60s on Thu and
H85 temps of 8-10c should support inland max temps in the upper 60s
to lower 70 on Fri. Continued onshore ne flow will keep max temps
cooler both days near Lake Superior in the lower to mid 60s. Influx
of mid-Atlantic moisture wrapping around cut-off low could lead to
increase in mid-level clouds on Fri over the southeast half of U.P.

Models in general agreement with mid-upper low moving slowly
northward into the Ohio Valley/Great Lakes region Fri night into the
weekend and getting eventually caught back in westerly mid-latitude
flow in response to deepening mid-upper trough over the West Coast.
Continued influx of deeper mid-Atlantic moisture wrapping around low
and increasingly cyclonic ne flow will lead to increased chances for
rain beginning Fri night and continuing into the weekend especially
for the east half of Upper Mi closer to the movement of mid-upper
low.

Model trends indicate closed low slowly moving east toward New
England Sun night into Mon as western CONUS trough moves slowly
eastward. Should see improving weather across Upper Michigan Sun
night into Mon as upper level ridging from west becomes main feature
again. Expect increasing clouds from the west late Mon night into
Tuesday as mid-level moisture increases with approach of mid-upper
trough from western CONUS and associated sfc trough from the Plains.
Some increase in mid-level q-vector convergence ahead of the trough
could also bring some light rain into west and central Upper Mi on
Tue. Not surprisingly the 12z GFS is showing its typical bias with a
quicker advance of trough than the 12z ECMWF so will include some low
chance pops for rain over west and central counties mainly Tue
afternoon. &&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 142 PM EDT TUE SEP 27 2016

A deep, moist cyc flow arnd a slow moving lo pres system sinking
slowly s thru the Upr Great Lks will bring some showers and MVFR
conditions much of the time thru tngt. The best shot at IFR
conditions wl be at IWD due to a more favorable upslope nw veering n
wind component and longer air trajectories down wrn Lk Sup.
Downslope nature of the nw flow into SAW may lead to vfr conditions
at times this aftn. Although the arrival of drier air aloft and a
weakening cyc flow wl tend to diminish the showers on Wed, lingering
llvl mstr/upslope nne winds wl lead to continued MVFR cigs.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 332 PM EDT TUE SEP 27 2016

As low pressure over eastern Lake Superior weakens and sinks slowly
south of the area through Wednesday, the pressure gradient over the
lake will gradually slacken causing north-northeast winds to 30
knots tonight over west and north central Lake Superior to diminish
to 20 to 25 knots on Wed. There could be some gale gusts to 35 knots
tonight mainly over the western half of Lake Superior. With the slow
approach of trailing high pressure, the winds will continue to
diminish late Wed into the weekend with lighter east to northeast
winds under 20 kts expected.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...07
LONG TERM...Voss
AVIATION...KC
MARINE...Voss



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