Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 291940

Area Forecast Discussion
National Weather Service Marquette MI
340 PM EDT MON AUG 29 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 338 PM EDT MON AUG 29 2016

Water vapor imagery and RAP analysis shows a zonal flow over the
northern conus into the Upper Great Lakes. A shortwave upstream over
the Dakotas is poised to move east into the Upper Great Lakes later
this evening and overnight bringing the cold front now over nw Mn
into the area, and this front could become the focus for some
convection later on this evening into the overnight hours. Over
Upper Mi this afternoon some cloud debris remains from morning
convection which has now lifted into far northern Lake Superior, but
there has been enough sunshine to allow temps to rise into the upper
70s/lower 80s across much of the cwa. Moist dewpoints in the lower
to mid 60s have also contributed to humid/muggy conditions across
much of the area this afternoon.

Big question tonight will be shower coverage as cold front arrives
from west later this evening. Forecast is complicated by fact that
latest SPC mesoanalysis shows fairly strong capping of 100-200 j/kg
CIN along and downstream of the cold front over eastern Mn and
northwest Wi despite MLCAPEs of 1000-1500 j/kg. There has been some
weakening of the cap into the western interior of Upper Mi in the
past hour and this may be an area to watch to see if convection
initiates in the next couple hours. If convection fails to form in
next few hours, we may need to wait until the arrival of the front
later this evening (just after 00z) before convection gets going.
Only problem is that by then instability will begin to wane ahead of
the front. Also, models indicate best shortwave dynamics will lift
mainly well north into Ontario so not expecting much help from
shortwave to enhance shower activity along the front.

Given uncertainty with shower/t-storm coverage along the front,
generally decided to lower pops to low chc category (30-40 pct)
along the front as it slowly sags se through Upper Mi. Remaining
shower coverage will probably become more isolated late tonight
along the front as instability diminishes. Isolated shra/tsra could
continue into Tue morning before front sags farther se of area.

Min temps tonight will be in the 60s and max temps on Tuesday will
be generally in the 70s. Conditions will become more comfortable
Tuesday as dewpoints lower from the west through the day.

.LONG TERM...(Tuesday night through Monday)
Issued at 257 PM EDT MON AUG 29 2016

Nam shows a 500 mb trough coming onto the west coast 00z Wed with a
ridge in the Rockies and northern Plains. A shortwave digs se out of
Ontario Tue night and affects the area Wed. This shortwave digs into
the lower Great Lakes and New England on Thu. This shortwave stays
far enough away though that it should remain dry for Tue night
through Thu. Overall, did not make too many changes to the going

In the extended, GFS and ECMWF show a 500 mb ridge building into the
upper Great Lakes 12z Fri with a deep trough on the west coast and
another over the east coast. This ridge builds into the lower Great
Lakes with the trough in the western U.S. 12z Sat with warmer air
moving into the area. The trough slowly moves into the Rockies 12z
Sun with some shortwaves ejecting out of it into the plains and
Great Lakes region and pattern changes little 12z Mon. A sfc front
stalls out northwest of the area Sun into Mon. Temperatures will be
above normal this forecast period. Will be dry Thu night through Sat
before front gets close enough to have some chance pops in the far
west Sat night through Sun and then have chance pops in for Sun
night into Mon.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 133 PM EDT MON AUG 29 2016

Expect VFR conditions at all 3 terminals to continue into the evening
hours. Additional shra/tsra will probably develop this evening as a
cold front drops into the area from the west. Confidence in coverage
and whether any of the terminals will be affected is low. So, for
most part only a VCSH was included in fcst. MVFR cigs could develop
at SAW for a few hours late tonight/early Tue morning in the wake of
the frontal passage...otherwise expect VFR conditions at the taf
sites through much of the period.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 338 PM EDT MON AUG 29 2016

Expect winds mostly under 20kt through early this week as pressure
gradient remains generally weak. Stronger NW to N winds with gusts
to 25 kts may occur on Wed as a high pressure ridge builds toward
the area in the wake of cold front passage early on Tue morning.
Eastern Lake Superior would be favored for the stronger winds. Winds
diminish to less than 20 kts rest of the week as high pressure moves
across. S to SW winds increase to around 20 kts on Sat as pressure
gradient tightens btwn the exiting high and sharpening sfc trough
over the Northern Plains.

Upper Michigan...
Lake Superior...
Lake Michigan...


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