Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 220756
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
356 AM EDT Thu Jun 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 319 PM EDT WED JUN 21 2017

Beautiful puffy afternoon cumulus clouds have dotted the sky across
much of the U.P. With high pressure overhead, and very minimal
pressure gradient in place, lake breeze development off of Lake
Superior/Michigan have pushed inland and eroded the cumulus adjacent
to the lakes. With some filtering of solar radiation, surface temps
have been slow to warm into the 60s with a few low 70s. Minimal
mixing has held onto Td`s in the upper 40s to low 50s. The focus for
tonight will be on the upstream system progged to arrive after
midnight and bring rain back to the region.

GOES-16 satellite imagery shows the leading edge of the cloud shield
with the shortwave over Northern Minnesota stretching northwest
through Canada. With the quasi-zonal flow aloft, it does appear the
forward speed of the system will be progressive. So expect
thickening of the clouds by sunset or shortly after, and precip
beginning to show across the far western U.P. around 3-5z. Further
east the timing for precip arrival will be closer to 7-10z. With the
progressive pattern, by daybreak Thur the frontal boundary should
clear east of the central U.P. with flow aloft remaining relatively
flat. Temps overnight will remain mild in the low/mid 50s.

With the precip arrival, guidance is indicating some instability
with isolated thunder overnight. But this appears to be limited and
confined to the central/southern portions of the U.P.

With the quick clearing Thur, and an active pattern,  the frontal
boundary that is pushed south earlier in the day will begin to lift
north by late afternoon. But with an approaching 500mb vort max
aloft pivoting southeast late Thur aftn, this should help hold the
boundary further south and limit precip to the southern portions of
the U.P. late aftn. Temps will warm into the low/mid 70s Thur, and
could see a few upper 70s to near 80 in the southern CWFA.

.LONG TERM...(Friday through Wednesday)
Issued at 355 AM EDT THU JUN 22 2017

Upper level troughing and resulting cool weather pattern still on
track to begin to settle across Upper Great Lakes on Fri. Main sfc
low near 1000mb starts day over northern Ontario with lead cold
front already east of the forecast area by daybreak on Fri. Weaker
front may slide across through the day but deep drying should result
in mainly dry conditions. Suppose with pooling of 50-55F dwpnts off
northern Lk Michigan and Green Bay and temps into the 70s could see
up to 250j/kg of sbcape and potential for isolated showers over the
southeast especially if there is any type of additional forcing from
shortwave trough working through. With upper level jet axis still
overhead into the aftn ahead of upper troughing, could also be
pockets of upper level divergence to help convection along. Limited
moisture will keep chances very low.

Upper trough expands over the Great Lakes this weekend into early
next week. Daytime highs will stay below normal. Coolest days will
be Sat and Sun as stronger shortwave trough and enhanced rain
chances affect area (Sat) and with lowest temps aloft rotating
across (Sun). Readings both of these days will be in the upper 50s
near Lk Superior and into the upper 60s far south central. Steep mid
level lapse rates up to 6.5-7c/km at times with several shortwaves
and pockets of enhanced moisture and sfc troughs wrapping through
the region within the large scale trough will lead to daily chances
for showers and some thunderstorms Sat through at least Mon, with
maximum coverage occurring during peak heating late morning through
aftn into early evening and/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). 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, though waters
may be just cool enough to not support that at this time.

Troughing begins to break down by middle of next week. Temperatures
should warm back toward normal levels and the periodic chances of
rain should end at least for a day or two. By late next week should
see rain chances increase yet again as strong low crossing central
Canada and cold front extending south across the plains allows warm
and humid air to stream north into the Upper Great Lakes.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 748 PM EDT WED JUN 21 2017

VFR conditions are expected until later tonight when conditions fall
to MVFR at CMX/SAW with some rain moving in from west to east,
mainly aft 06z. The lowest cigs are expected at SAW with sry
upslope flow. Some thunder may also be possible, mainly at IWD.
Conditions should improve to VFR by afternoon with drier air
moving in behind the trough.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 319 PM EDT WED JUN 21 2017

Some patchy fog is possible late tonight with rain sliding over the
lake. Winds will remain sub 20kts tonight; however, there could be a
brief increase in wind gusts with any thunderstorms that move over
the marine environment.
&&

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

$$

SHORT TERM...Beachler
LONG TERM...JLA
AVIATION...JLB
MARINE...Beachler


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