Area Forecast Discussion
Issued by NWS Marquette, MI

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999
FXUS63 KMQT 250806
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
406 AM EDT SUN SEP 25 2016

.SHORT TERM...(This evening through Sunday)
Issued at 253 PM EDT SAT SEP 24 2016

Surface ridge axis that extends from Ontario through eastern Lake
Superior into the eastern Great Lakes will only shift slowly
eastward tonight. Low level airmass is pretty dry and with several
hours of clear skies across the east tonight temperatures should
fall back into the 40s. Increasing clouds across the west should
keep temperatures much milder in the mid 50s.

Surface low over the northern plains will lift slowly northeastward
to the Manitoba/Ontario border on Sunday dragging an occluded front
eastward into the area. Deep moisture and convergence ahead of the
front should bring widespread shower and isolated thunder activity
to the U.P. during the day on Sunday. Rainfall totals should average
between a quarter and half inch before precipitation tapers off from
the west late in the day. Temperatures will be pretty seasonable in
the mid 60s.

.LONG TERM...(Monday through Saturday)
Issued at 400 AM EDT SUN SEP 25 2016

Main story in the long term is deepening low pressure system that
affects the Upper Great Lakes early this week as upper trough
deepens/closes off over Great Lakes and northern Ontario.

Strong and gusty winds should will occur at times though differences
in forecasted winds aloft keep confidence on widespread high impact
wind event on the lower side attm. Tightest pressure gradient and
925mb winds 35-40 kts would favor the Lk Superior shoreline of
western Upper Michigan and over all of the Keweenaw Peninsula for
west to northwest wind gusts up to 45 mph mid morning Mon into Mon
evening. Could also see similar wind gusts along Lk Superior from
Big Bay to Munising and Grand Marais Mon night, but model trends are
not as clear as they are over western cwa. Winds will remain gusty
into Tue over most cwa, but especially along Lk Superior. Waves will
be high on Lk Superior as well leading to high swim risk and the
potential for some beach erosion. Both of these items will be
mentioned in HWO. May not end up needing a Beach Hazard Statement
though as expected temps in the 50s and inclement weather with
frequent showers and blustery winds should keep most people away
from the beaches.

Due to the deepening upper level trough across the Great Lakes and
sufficient deep moisture/cyclonic low-level flow, cool air advection
with h85 temps down to 1-4c should result in plenty of showers due
to the system and/or lake enhancement with terrain upslope lifting
occuring as well. Likely pops or greater will start up on Mon morning
as wraparound moisture in the cyclonic low-level flow moves in and
the higher pops will last all the way through Tue afternoon. Only
scntrl cwa will escape the frequent showery weather, though should
see pops increase there as well on Tue helped along by daytime heating
and with upper low center settling closer by across east half Upper
Michigan to Georgian Bay. Through the period the lowest h85 temps are
over western Lk Superior and western Upper Michigan. This area is
also where sharpest cyclonic flow is too. The low-level convergence
along with sfc-h85 delta t/s nearing 13c signals potential for at
least moderate rainfall for western cwa, again helped along by
additional upslope lift.

With upper low in the vicinity and SI/s falling to around 0c, did
include slight mention of thunder Mon into Tue with the stronger
dynamics around.

Upper low and sfc low drift toward lower Great Lakes on Wed. North
winds will be weakening over Upper Michigan but the flow off Lk
Superior with daytime heating and some lingering low-level moisture
could help develop some light showers/sprinkles out of a cu/sc deck.
High pressure then builds in late this week into next weekend. Expect
dry weather with a gradual warming trend. Nighttime temps once the
high centers overhead late this week could drop into the upper 30s to
low 40s. Interesting side note that so far at NWS Marquette office
this month we have not recorded a temp blo 41 degrees. Last time this
site saw a reading in the 30s was back on July 16th (of course), when
we saw a low that morning of 39 degrees.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 102 AM EDT SUN SEP 25 2016

VFR conditions will continue overnight at KIWD/KCMX/KSAW as low
levels remain relatively dry. Under a tightening pres gradient,
increasing winds above inversion will be sufficient for llws at KIWD
late tonight. Ahead of a cold front arriving late aftn/evening, a
band of shra will gradually spread e across the area, bringing
deteriorating conditions to low MVFR. May see a short period of IFR
at KIWD/KSAW. Winds will also become gusty to around 20-25kt today.
Toward the end of the fcst period after fropa, KIWD may improve to
VFR.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 253 PM EDT SAT SEP 24 2016

Tightening pressure gradient across the lake tonight as high pressure
moves toward Quebec and New England and a low pressure system lifts
across Manitoba to northern Ontario. Southeast winds may gust as
high as 30 kts Sun into Sun evening over north central and eastern
sections of Lk Superior. The low will move east of the region Mon
into Tue and a cold front will cross Lake Superior. With 850
Temperatures falling to 2 C and tight pressure gradient on back side
of surface low dropping southward over the eastern lake...expect
northwesterly gales to around 40 knots on Monday and Monday evening.
Northwest winds to 25 kts continue on Tue then winds diminish to 20
kts or less by Wed as high pressure crosses the Great Lakes.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Warning from 8 PM this evening to 4 AM EDT Monday for
     LSZ267.

  Gale Watch from Monday afternoon through late Monday night for
     LSZ264>266.

  Gale Watch from Monday morning through late Monday night for
     LSZ162-240>242-263.

Lake Michigan...
None.
&&

$$

SHORT TERM...MZ
LONG TERM...JLA
AVIATION...07
MARINE...MZ



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