Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 211921
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
321 PM EDT Wed Jun 21 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...(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 18Z TAFS through 18Z Thursday afternoon)
Issued at 319 PM EDT WED JUN 21 2017

VFR conds will persist thru this evening. CIGs will be slowly
lowering with precip arriving from west to east tonight, but
current guidance indicates the lowest CIGs will be hovering around
1200-1500ft agl. This timing still remains to be after 8z thru 12z
then slowly lift back towards VFR conds.

&&

.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...Beachler
MARINE...Beachler


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