Area Forecast Discussion
Issued by NWS Marquette, MI

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458
FXUS63 KMQT 201909
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
309 PM EDT Tue Jun 20 2017

.SHORT TERM...(Today and tonight)
Issued at 416 AM EDT TUE JUN 20 2017

Upper troughing firmly in place from Hudson Bay to the Great Lakes.
More vigorous shortwave is digging across Minnesota within the
western edge of mean troughing. Main sfc low well to the northeast
of the region over northern Quebec at 996mb but there is weaker sfc
trough just northwest of Lk Superior. Are even seeing a few light
showers ahead of these features working west to east across central
forecast area. 00z sounding at CWPL in northern Ontario showed
increasing h7-h5 moisture beneath the upper trough in wake of the
sfc front so plan is to see increasing showers around daybreak
sliding across mainly northwest to central Upper Michigan. Similar
to Mon, would expect most showers to shift to south central Upper
Michigan by mid aftn. Just a small chance of a thunderstorm with
mlcapes up to 300 j/kg but with similar thermal setup to Mon there
could be more instances of cold air funnels. Not enough confidence
though to issue SPS. Will have to be nowcast type issue as it was
on Monday. H85 temps late this aftn change little compared to
Mon aftn so went with high temps mainly in the 60s, coolest near
Lk Superior east of Marquette and warmest over far scntrl where
readings could again near 70 degrees.

Once shortwave over Minnesota slides south and east of the area by
late this aftn, subsidence and strong drying will end any showers by
early this evening and clouds should decrease quickly from west to
east with skies becoming mostly clear overnight. With high pressure
over the plains settling over the western Great Lakes leading to
light winds/clear skies seems that favored cool spots may try to
fall into the lower 40s as is occurring this morning in the vcnty of
the high over south central Canada.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 308 PM EDT TUE JUN 20 2017

Much more of the same is expected through the upcoming week, with
below normal temperatures and periodic chances for showers and
possibly some storms. North Pacific troughing combined with North
Atlantic ridging will keep a somewhat stagnant flow of western North
American ridging and eastern North American troughing into next
week. Signs are pointing to this pattern finally starting to break
down late next week.

Wednesday night through Thursday: A mid-level low over the Gulf of
Alaska will quickly round the western ridge tonight before
elongating over the southern Canadian Prairies on Wednesday. A lead
trough axis will sweep eastward across Upper MI Wednesday night into
Thursday morning while weak troughing over the central Plains
induces a convective complex over Iowa and southern Wisconsin.
Guidance continues to indicate scattered to numerous showers tied to
this trough axis and associated surface front, with most locations
seeing about a six hour window of precip. A few stronger elevated
storms may even sneak into the far south-central late Wednesday
night into Thursday morning with 1-6km shear of 60kts and MuCAPE
nearing 1000j/kg. The U.P. may end up falling between the two
regions of best forcing, so am inclined to hold on to just low-end
likely PoPs.

The front will lay out across central WI on Thursday, providing an
impetus for more convection there later in the day. Some of this
convection may brush the south-central and far SE in the evening,
but much of the CWA should remain dry after the earlier precip
clears.

Friday through Tuesday: The aforementioned mid-level low will
reinforce deep troughing drifting southward from Hudson Bay. A
series of shortwave troughs wrapping around the longwave trough will
bring periods of scattered showers during this time, with diurnal
enhancement in the afternoons and evenings. With that said, the
focus for the best chances will be late Saturday afternoon into
Sunday morning in response to a stronger trough axis.
&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 142 PM EDT TUE JUN 20 2017

A weak low pressure trough moving across Upper Michigan has
resulted in more showers today. Showers have been mainly over the
se half of Upper Mi and generally not affecting the TAF sites,
except SAW could be on edge of showers activity so did include
VCSH for first few hours of forecast. Low level moisture still
impacting CMX with IFR cigs, but expect improvement to MVFR in
couple of hours with clouds breaking out late in afternoon/toward
evening as drier works in fm the west. Otherwise, expect VFR
conditions for rest of TAF sites through the period.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 416 AM EDT TUE JUN 20 2017

A few westerly gusts to 25 kts are possible this morning over the
east half of Lk Superior. Otherwise expect winds to remain 20 kts
or less into Wed. S winds shifting to the SW may reach up to 25
kts late Wed night through Thu night as a low pressure system and
cold front cross the Upper Great Lakes. Winds will diminish below
20 kts Fri into Sat behind the cold front.
&&

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

$$

SHORT TERM...JLA
LONG TERM...Kluber
AVIATION...Voss
MARINE...JLA



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