Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211021

Area Forecast Discussion
National Weather Service Marquette MI
621 AM EDT Wed Jun 21 2017

.SHORT TERM...(Today and tonight)
Issued at 309 AM EDT WED JUN 21 2017

Upper air pattern consists of a 500 mb ridge across the desert sw
and southern Rockies and troughing across the eastern U.S. and lower
Great Lakes. The upper level flow across the northern Rockies and
northern plains is zonal this morning. There is a shortwave over the
Canadian Rockies that will be the next weather maker for the area as
it heads east into the Canadian prairies tonight. Nam brings in some
deeper moisture along with 850-500 mb q-vector convergence tonight.
GFS and ECMWF show a same thing. Did not make too many changes to
the going forecast overall except did go dry for today for all the
U.P. and removed the pops that were in the west late in the
afternoon. Pops will rapidly increase tonight and have likely pops
across the central late tonight before they pull to the east late

.LONG TERM...(Thursday through Tuesday)
Issued at 354 AM EDT WED JUN 21 2017

Upper trough over western Canada moves to central Canada by Thu
morning. Sfc-h85 low associated with the upper trough will be over
central Manitoba with an occluded sfc front arcing toward Lk
Superior and Upper Michigan. Occluded front should transition to
cold front northern MN to Neb while warm front with 65+ dwpnts will
be approaching Upper Michigan from Wisconsin and Lower Michigan.
Strong moisture transport into the warm front along with 1000+ j/kg
of elevated cape will support showers and thunderstorms later
tonight and these should be shifting mainly south and east of Upper
Michigan on Thu morning as h85 low-level jet veers WSW. What is
leftover for rest of Thu is a question. Based on progged sfc
winds/temps/dwpnts the GFS and NAM are more aggressive in pushing
warm front into at least south central Upper Michigan by Thu aftn
before the cold front arrives while the GEM and ECMWF keep warm
front mainly south of the area. Think the latter solution may be on
right track given possibility that outflow from morning convection
would push effective warm frontal boundary farther south.

Since occluded front is forecast to slide west to east across Upper
Michigan on Thu probably can not discount additional showers and
thunderstorms trying to develop later in the day and into the
evening. This would be especially true if occluded front is slower
to cross and if h7 shortwave and associated moisture transport shown
by NAM/GFS and hinted at by ECMWF brings a push of larger scale lift
across forecast area late in the day into the evening. Instability,
even elevated, is not very high though as it is tied closer to sfc
warm front expected to be south of area. If a bit more instability
can work farther north then there is a risk of stronger storms over
scntrl Upper Michigan Thu evening as effective shear is over 40 kts.
Pops will be highest over south central Upper Michigan in the
evening given the forcing but rain chances will diminish steadily
overnight as stronger subsidence arrives in wake of shortwave trough
sfc low and cold front passage.

With upper level troughing overhead Fri along with steeper mid level
lapse rates could see a few shra/tsra in the aftn. Moisture looks to
be limited so coverage and chances will be minimal. WNW winds could
be quite gusty on Fri with wind gusts 30-40 mph possible in the
higher terrain near Lk Superior. Increased winds over what model
blends offered up as they seemed too low in this type of post
fropa/deeper mixing pattern. More significant cooling will not
arrive until the weekend though so temps on Fri could still reach
well into the 70s, especially for downslope areas of scntrl
foreast area.

Upper troughing becomes stronger through the upcoming weekend and
even into early next week. Daytime highs will stay below normal
with readings most days in the 60s though there may even be a day
or two near Lk Superior with readings staying in the 50s. Mid
level lapse rates steep at times with 6.5-7c/km and there are
multiple shortwaves/pockets of enhanced moisture and sfc troughs
wrapping through the region within the large scale trough. Expect
daily chances of showers and some thunderstorms Sat through next
Tue, with maximum coverage occurring during peak heating late
morning through aftn into early evening or when stronger
shortwaves come across. On days the thunderstorms are stronger, at
least small hail would occur. Could also see some more cold air
funnel episodes (similar to what occurred Mon of this week) and as
water temps warm up on Great Lakes, getting to the point where
this type of upper trouging/cold air advection regime could even
lead to waterspouts. Not quite what you expect for the first full
weekend of Summer.

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 621 AM EDT WED JUN 21 2017

VFR conditions are expected through most of the forecast period
until later tonight when conditions fall to MVFR with some rain
moving in. Conditions will fall first at IWD.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 309 AM EDT WED JUN 21 2017

Expect winds to remain 20 kts or less through the forecast period.
There could be some patchy fog that forms late tonight across the
waters as rain moves through and this fog would burn off on Thu.

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


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