Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251847

Area Forecast Discussion
National Weather Service Marquette MI
247 PM EDT SUN SEP 25 2016

.SHORT TERM...(Today and tonight)
Issued at 434 AM EDT SUN SEP 25 2016

Upper air pattern consists of a closed 500 mb low over ND embedded
in a longwave trough over the northern plains with a shortwave ridge
over the upper Great Lakes this morning. The trough and closed low
move east and affect the upper Great Lakes this afternoon and
tonight. Nam brings in some 850-500 mb q-vector convergence along
with deeper moisture today into tonight with a dry slot moving
through tonight across the western half of the cwa.

Overall, did not make too many changes to the going forecast for
temperatures. As for weather, slowed the progression of pops across
the cwa a bit today and delayed pcpn in the east a couple hours due
to drier air remaining over that area the longest for this morning.
Did go categorical pops in a narrow band that moves across the area
this afternoon and tonight and could see 0.50 to 1 inch of rain as
this band moves through.

.LONG TERM...(Monday night through Sunday)
Issued at 246 PM EDT SUN SEP 25 2016

Focus in the long term continues to be on a low pressure system that
will be occluding over or just N of far northern Lake Superior Mon
evening. The low will linger in the vicinity of the far northern
lake until Tue morning when it will start a slow move to eastern
Upper MI by 00Z Wed. The system moves S of the area Tue night, with
SFC and upper ridging moving in from the NW on Wed.

Main significant impacts will be strong winds near/over Lake
Superior and resulting high waves. Certainly will be seeing plenty
of rain, but not a worrying amount.

Models agree quite well with the track/strength/timing, but some run
to run variability still exists, so the wind forecast will continue
to need fine-tuning. Expect the strongest winds (at least in the
long term) on Monday evening with WNW gusts to 45mph along Lake
Superior over the western U.P. and over much of the Keweenaw. NW-N
winds will gust 35-40mph near Lake Superior for the rest of Mon
night through Tue. Winds will diminish Tue night into Wed.
Winds/waves will lead to dangerous swimming conditions on Lake
Superior, as well as beach erosion (especially along eastern Lake
Superior). No need for a beach hazards statement as temperatures
will be below criteria and it will be rainy.

Lake enhancement will occur as 850mb Temps will be 1-4C from Mon
into early Wed, which when combined with deep cyclonic flow and
upslope forcing will lead to lots of rain near Lake Superior and
more scattered showers well inland. Winds will favor WNW flow area
Mon night, NW-N flow areas Tue, N-NE flow areas Tue night, then
diminishing chances in north central Upper MI Wed morning as NE flow
remains while ridging increases. Should easily see over an inch of
rain Mon night and Tue over the higher terrain of the NW and a
quarter to half inch elsewhere near Lake Superior...under a quarter
inch south central. Tue night into Wed should add another quarter
inch or less of QPF...highest over the higher terrain of the north

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 145 PM EDT SUN SEP 25 2016

Gusty sse winds wl advect a good deal of mstr into Upr MI ahead of
an aprchg cold fnt. The combination of this llvl mstr and showers wl
result in period of MVFR/hi end IFR conditions at the TAF sites. The
arrival of some drying following the cold fropa with a wshft to the
wsw wl then bring at least a brief improvement to VFR w-e this evng
into the overngt before more llvl mstr arrives and causes cigs to
drop into the MVFR category, earliest at IWD/CMX. Winds shifting to
the w wl become gusty over the wrn TAF sites on Mon mrng, especially
at the more exposed CMX location.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 434 AM EDT SUN SEP 25 2016

Tightening pressure gradient will happen across the area 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 and will go with a gale warning
across the far eastern lake for gales to 35 knots tonight. 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 and a gale watch was issued for
this. Northwest winds to 30 kts continue on Tue then winds diminish
to 20 kts or less by Wed through Thu as high pressure crosses the
Great Lakes.

Upper Michigan...
Lake Superior...
  Gale Warning from 8 PM this evening to 4 AM EDT Monday for

  Gale Watch from Monday afternoon through late Monday night for

  Gale Watch from Monday morning through late Monday night for

Lake Michigan...


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