Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251741

Area Forecast Discussion
National Weather Service Marquette MI
141 PM EDT Thu May 25 2017

.SHORT TERM...(Today and tonight)
Issued at 454 AM EDT THU MAY 25 2017

Upper trough from the Upper Great Lakes to the southeast Conus
continues to slowly move east today while 993mb sfc low along the
IN/OH border reaches the lower Great Lakes by this evening. Even
though the main system is tracking well to the east and south of
Upper Michigan, pockets of deeper moisture and weak lift may still
lead to some showers today. Have seen isolated showers through the
night over the central forecast area but main focus for rain today
will be over southeast half of Upper Michigan. Since the lift is
weak and high pressure continues to build in from the northwest,
rain amounts should be light for most part. However, this aftn with
some heating could see showers increase some, especially over south
central and east forecast area away farther away from lake
moderation and stabilzation off Lk Superior. Will continue to favor
partly cloudy skies over west farther away from the low pressure
system and closer to the high pressure/dry air over northern
Ontario. Temps aloft warmer than Wed and better chance at seeing
some sunshine, so expect decent warming trend today compared to last
couple days. Coolest readings in the low 50s will be near Lk
Superior with persistent NE-NNE flow but otherwise expect highs well
into the 60s if not reaching 70 over interior west. Could also get
well into the 60s over interior east away from Lk Superior but that
will depend on how many breaks occur in the clouds.

For tonight, as upper low and sfc low move toward the Mid Atlantic
states, they should no longer directly influence the weather over
Upper Michigan. Instead the high pressure ridge moving into western
U.P. this aftn will move over rest of the area through the night.
Another sfc low tied to larger upper low over Saskatchewan and
Manitoba will be dropping across southern Manitoba late tonight
pushing a low pressure trough across MN and western WI. Best chance
for some clear skies through at least midnight will be from Keweenaw
to parts of central Upper Michigan. Skies will then cloud up later
tonight over those areas fm the west. The clear skies and light
winds may lead to some fog as temps could drop into the upper 30s.
Otherwise, sct-bkn clouds will lead to temps staying in the 40s.
Some rain showers may try to work in very late tonight far west as
weaker shortwave and some h85 warm air advection ahead of scntrl
Canada upper low surges toward Upper Great Lakes. Forecast soundings
show various degrees of saturation though with weak forcing overall
so went nothing more than slight chance pops at IWD late.

.LONG TERM...(Friday through Wednesday)
Issued at 344 AM EDT THU MAY 25 2017

Fairly active but low impact weather is expected through the long
term. Beginning Fri, models show mid-level ridge axis centered over
the area in the morning shifts e late in the day as a shortwave
approaches up the backside of the ridge. As the ridge axis shifts e
later on Fri scattered showers should return to at least west half
portions of Upper Mi Fri afternoon into Fri night and even some
isold showers could move into the east Fri night with passing
shortwave. Instability looks somewhat marginal for thunder.

There is bit more model uncertainty regarding timing of next
shortwave into the area for the weekend. NCEP and even 12z ECMWF
suggest drier conditions with absence of any shortwave while the 00z
CMC still suggests a weaker passing shortwave leading to some isold
afternoon showers over the central counties where developing lake
breezes should aid convergence along lingering sfc trough. Expect
shower chances to increase heading into Sun and Memorial Day as the
broad mid-level trough over south central Canada and the Northern
Plains deepens over the Western Great Lakes and a series of
shortwaves move through the region. There is also better instability
for diurnal thunderstorms Sun and Mon with model soundings
indicating up to a couple hundred j/kg SBCAPE. There is still plenty
of model uncertainty on timing of shortwaves heading into Tue and
Wed, but model consensus suggests scattered showers should linger
into at least Tue. While many of the models are indicating drier
conditions for Wed, weak mid-level troughing and cyclonic flow would
argue for keeping at least a slight chcs for showers in fcst.

As for temps, waa on backside of mid-level ridge and ahead of
advancing trough will yield normal to slightly above normal temps
Fri into Sat, but then temps will trend cooler for the rest of the
Memorial Day weekend into midweek falling below normal again Mon-Wed
in response to the deepening trough over the area.

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 139 PM EDT THU MAY 25 2017

Expect VFR conditions to prevail at IWD and CMX through the period.
VFR conditions will also prevail at KSAW but there could be some
radiation fog late tonight with IFR vsby.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 454 AM EDT THU MAY 25 2017

Expect winds under 20 kts through early next week as a relatively
flat pres gradient dominates the Upper Lakes.

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


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