Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 281140
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
740 AM EDT SUN AUG 28 2016

.SHORT TERM...(Today and tonight)
Issued at 519 AM EDT SUN AUG 28 2016

Water vapor imagery and RAP analysis show a well-defined shortwave
over far northern Lake Superior/adjacent northern Ontario. Despite
vigorous look of wave, little pcpn is occurring s of the
international border. Shra and isold tsra did move across western
and north central Lake Superior during the night. More recently,
-shra are brushing the northern Keweenaw, and there may be a few
sprinkles over western Upper MI. A mix of stratus and stratocu
dominates the area early this morning. However, with subsidence
beginning to increase as shortwave departs, some holes are opening
up in the clouds. Upstream, the next feature of interest is
shortwave trof moving across Alberta. Increasing low-level jet ahead
of wave has generated a cluster of shra/tsra in ne SD early this
morning.

If there are a few sprinkles/isold -shra over the w half of Upper
MI, that pcpn will end around sunrise. Then, expect a gradual trend
to mostly sunny skies during the day under subsidence/drying. Based
on projected mixing heights on fcst soundings, max temps should be
mostly in the mid/upper 70s. With sfc high pres setting up over the
area this aftn, lake breezes will develop.

Tonight, as Alberta shortwave moves to Manitoba, attention turns to
the increasing low-level jet in response to the wave. Models
indicate the low-level jet will be aimed across MN into adjacent
northern Ontario during the night. Most guidance show the low-level
jet remaining w of Upper MI tonight, and while an extension of
weakening elevated instability does edge into the w overnight, the
main area of instability holds back to the w, suggesting convection
will probably remain w of Upper MI tonight. Guidance shows a wide
spread of solutions, not unusual for convection. As is often the
case, the GFS is most generous with pcpn, spreading it across the w
half of Upper MI. The Canadian models and ECMWF are dry thru 12z
while the NAM, NCEP ARW/NMM and NSSL WRF indicate pcpn nearing or
reaching far western Upper MI by 12z Mon. NCAR ensembles show quite
a spread, but a majority tend to favor the idea of pcpn reaching the
w very late tonight. At this point, will only include schc/low chc
pops spreading into western Upper MI in the 09-12z time frame. To
the e, slow moving sfc high pres ridge and axis of min precipitable
water around 2/3rds of an inch suggest leaning toward the low side
of guidance for mins tonight. Expect interior locations over the e
to fall into the 40s. Even over the central, a few spots could drop
blo 50F if clouds are slow to increase.

.LONG TERM...(Monday through Saturday)
Issued at 319 AM EDT SUN AUG 28 2016

On Mon, westerly flow aloft in wake of the strong trough moving
through attm brings a cold front in late Mon aftn or Mon evening.
Theta-e advection aloft ahead of the front could result in showers
and isold tsra as early as Mon morning. At the least, consensus of
models indicates good deal of mid-high clouds with a few light
showers. NAM/GEM and various high res guidance such as NCEP WRFs
point to weakening cluster of tsra roaming over west half of Upper
Michigan on Mon morning. Extent of convection on Mon morning dictates
how much instability is present during the aftn as the front
approaches. Even if there is minimal sfc based convection in the
aftn, there is potential for elevated convection on Mon evening
before the front crosses with sfc-h85 winds fm the wsw pushing 1-6km
MUCAPE up to 1000j/kg at least over the west cwa. Strong storms
certainly are possible with that extent of instability but effective
shear is barely over 20 kts so does seem that severe potential is low
attm. Shear is stronger over northern Minnesota and with expected
storm motion seems that greatest chance for severe over the cwa would
be on Mon evening over far west vcnty of IWD. Mon looks to be a warm
and humid day with dwpnts pushing over 60 degrees. Max temps near 80
or into low 80s seems good possibility with even just a few breaks
in the clouds during the day.

Front moves through early on Tue but secondary cold front moves
through late Tue morning into Tue aftn. May still be enough
instability and lingering moisture to kick off more showers and
thunderstorms over mainly south and east cwa. Latest ECMWF is slower
with departing qpf than previous three runs were. Not sure if that is
a trend or an outlier. Will keep some small chances going all day,
especially if another shortwave moves through in the wnw flow aloft.

High pressure builds over west cwa on Tue and will dominate across
all the cwa Tue night into the rest of the workweek. Upper trough in
vcnty on Wed along with h85 thermal trough with temps down to 6c
could support a few showers. Better shot of showers will be north
and east of Lk Superior across Ontario closer to track of shortwave
within the trough. Cool airmass could provide couple chilly nights
Tue night and Wed night and possibly Thu night too.

High slides east by next weekend allowing warm front to lift across
the Upper Great Lakes region. Theta-e advection will gradually bring
chance of showers and thunder back to the region. Depending on how
quick the instability axis progresses could see some rain as early
as late Fri night into Sat morning. Greatest chances as it look now
would occur later in the weekend just ahead of a cold front working
toward the region from the Northern Plains.
&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 740 AM EDT SUN AUG 28 2016

With drier air and high pres building into the area today, lingering
MVFR cigs at KIWD will scatter out to VFR this morning. At
KCMX/KSAW, VFR conditions will prevail today, though brief MVFR cigs
could occur this morning. VFR conditions will then continue tonight.
However, there are a couple of items to note. Shra/tsra may approach
KIWD near the end of the fcst period, and radiation fog could
develop at KSAW overnight. Potential in either occurring is too low
right now to include a mention in fcst.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 519 AM EDT SUN AUG 28 2016

Expect winds mostly under 20kt through the middle of next week as
pres gradient remains generally weak. If stronger winds do occur,
Tue/Wed would be the time frame as a high pres ridge builds toward
the area in the wake of cold front passage Mon night/early Tue
morning. Eastern Lake Superior would be favored for the stronger
winds.
&&

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

$$

SHORT TERM...Rolfson
LONG TERM...JLA
AVIATION...Rolfson
MARINE...Rolfson



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