Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 260013

Area Forecast Discussion
National Weather Service Marquette MI
813 PM EDT SAT JUN 25 2016

Issued at 811 PM EDT SAT JUN 25 2016

Per coordination fm SPC, issued severe TS Watch 300 for about the SW
half of Upr MI, where latest SPC mesoanalysis shows area of hier
MUCAPE/weaker CIN away fm area that was stabilized by earlier
convection as well as a SE flow off the cooling influence of Lk MI.
DCape is also more signicant in this area, so damaging winds should
be the primary threat. The watch is in effect until 06Z, with line
of TS now aprchg Ironwood likely to bow out to the ESE parallel to
the WI border.

.SHORT TERM...(This evening through Sunday)
Issued at 455 PM EDT SAT JUN 25 2016

Mess of convection has affected Upper Great Lakes today. To put it
nicely the models have really struggled with initial surge of
showers and thunderstorms that produced damaging winds across
Keweenaw Peninsula earlier today. That complex of storms has made it
over eastern Upr Michigan riding along edge of instability gradient
and within strong h85 warm air advection. Isolated storms have
formed within last hour over western Upr Michigan on edge of h8-h7
capping seen on 12z soundings fm Aberdeen SD and Minneapolis MN.
Earlier complex threw out an outflow/lake enhanced boundary and
this has settled over northwest WI and into far western Upr Michigan.
Also seeing additional showers and thunderstorms lifting across
northern WI and those likely will be in over southwest and south
central Upr Michigan in the next few hours. Attn is also on cold
front working across central MN where large cluster of severe storms
developed over last two hours.

Lets reset for the evening. Current layout of instability from SPC
meso page shows SB/ML cape gradient is oriented wnw/ese along the
sfc outlow/warm front into western Upr Michigan. Effective
instability (SBcape over 3000 j/kg) and shear (30-40 kts) feeding
storms forming over WI and into western Upr Michigan will continue
to support severe threat into the evening hours with the scattered
storms already ongoing. 0-1km shear 30+ kts also will support
balance of cold pools with environment shear. Thus, storms may merge
and keep a damaging wind threat going even away fm the strongest
instabiilty over northern WI. How far north and east these storms
can go into instability that is worked over from earlier aftn
convection is uncertain. Attn also will be on the strong convection
already growing upscale over MN to the west of DLH. Increasing h85
jet to 40-50 kts and 0-1km shear over 30 kts supports these storms
continuing to merge and congeal and follow the h85-h3 thickness and
SB cape gradient. This would bring a line of thunderstorms with
damaging winds the primary hazard across western half of Upr
Michigan through midnight and possibly across eastern cwa after

Front sweeps through late tonight. Showers and thunderstorms could
linger over eastern cwa until midday Sun. West winds will get very
gusty, especially over Keweenaw where advisory level gusts appear
likely. Cold air lags the cold front, typical for this time of year.
Expect highs to reach well into the 80s over central and east.
Downslope areas south central may near 90 degrees.

.LONG TERM...(Sunday night through Saturday)
Issued at 403 PM EDT SAT JUN 25 2016

Concerns include continued gusty west winds into early Sun evening,
especially over the Keweenaw Peninsula, and then a trend toward
cooler temps and some isold/sct -shra Sun night into Mon with more
sct shra possible Thu-Fri.

Beginning Sun night and Mon, expect gusty west winds to continue
into early evening especially over the Keweenaw Peninsula as model
soundings at KCMX show the potential of up to 40 kt winds within
mixed layer through 02z. Isallobaric component from pres rises still
occurring at this time will also likely aid gusts. By late evening,
winds should come down blo advisory level over the Keweenaw with
diminished mixing although breezy conditions will continue into
Monday especially along Lake Superior due to tight gradient on
backside of low over Quebec. Winds will shift from west to northwest
on Mon.

Concerning shower chcs Sun night into Mon, trailing shortwave energy
will likely support some isold -shra into areas along Lake Superior
Sun night with isold/sct shra expanding inland across the area on
Monday. With models showing 850mb temps falling to 4-5C over much of
the area and soundings showing quite a bit of low/mid level moisture
for clouds, Mon may end up unseasonably cool. Expect early max temps
to range the low/mid 60s n to low 70-mid 70s s central. In reality,
for much of the day, temps may not get out of the 50s w and n, and
nw winds will be breezy, adding to the cool feel.

Abundant sunshine and some warming will follow on Tue under a dry
air mass. Dry weather will continue into Wed with temps rising
closer to late June normals. Next nw flow shortwave dropping into
the eastern N America trough will arrive over the Upper Great Lakes
Thu. At this point, timing looks to coincide favorably with the
heating cycle to generate isold/sct shra/tsra Thu into Thu evening
where GFS shows MLCAPE values approaching 500 j/kg over the western
interior. Another shortwave moving through could bring some more sct
showers on Fri. Cyclonic nw flow continues over the area into Sat
although flow becomes more confluent aloft with sfc high pres
building into the area so expect drier conditions on Sat.

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 811 PM EDT SAT JUN 25 2016

A band of TS moving W-E ahead of an aprchg cold fnt wl impact the
TAF sites this evng, bringing some gusty winds and at least tempo
MVFR conditions. Some of the storms could be severe with damaging
winds. These storms should clear SAW during the early mrng hrs on
Sun. Aggressive drying behind the fropa wl then bring VFR wx the
rest of the fcst period. Gusty W winds, especially at the more
exposed CMX location, wl then occur thru the day on Sun under the
tight pres gradient behind the fropa and in the presence of diurnal

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 455 PM EDT SAT JUN 25 2016

Expect cold front to sweep across Lk Superior late tonight into Sun
morning. S-SE winds 20-30 kts, with wind speed and directions
altered by any showers and thunderstorms that occur as some of the
storms may be strong, will shift to SW behind the front. Gusts 30-35
kts may occur on Sun at higher observation platforms over west half
of Lk Superior. Expect gusty W winds to 25 knots to continue into
Monday before high pressure brings generally lights winds through
the remainder of next week.

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


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