Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 291858

Area Forecast Discussion
National Weather Service Marquette MI
258 PM EDT MON AUG 29 2016

.SHORT TERM...(Today and tonight)
Issued at 521 AM EDT MON AUG 29 2016

Water vapor imagery and RAP analysis show a shortwave trof moving
across Saskatchewan into Manitoba. In response to the wave, 30-40+kt
low-level jet per latest RAP analysis aimed ne across MN with 1000-
2000j/kg of mucape in the inflow is supporting a large cluster of
shra/tsra in northern MN early this morning. Northern end of
activity is showing signs of weakening, at least partly due to
storms on the southern and western end of the cluster increasingly
becoming aligned to disrupt low-level jet into the convection
farther n and ne. Closer to home, clear skies and good radiational
cooling for a good part of the night has allowed some fog/stratus to
form over portions of the central and eastern fcst area, typical for
this time of year. Lowest observed temp is 43 degrees nw of KERY at
Spincich Lake RAWS site.

Fcst for the morning hrs was largely constructed based on
extrapolation of the MN convection with some weighting of guidance
that has at least some resemblance to reality. As convection moves
out away from the better low-level jet forcing, expect the ongoing
weakening trend to continue, but at this point, it appears likely
pops will be warranted over the far w. Lowered pops to chc farther e
into central Upper MI and kept the e basically dry thru the aftn
with expectation of this cluster of shra/tsra never making it that
far e. What transpires after this convection moves thru/dissipates
is uncertain. While fcst maintains chc pops thru the aftn over the w
and central, it is certainly possible that there could be many hrs
with no shra/tsra under stabilizied air mass following the morning
pcpn. High res NAM window has been very insistent for a number of
runs that new convection will hold off until after sunset,
developing along the cold front that will drop se into the area.
This idea is supported by the NCEP NMM and NSSL WRF, and may offer a
reasonable solution for the aftn hrs and tonight. With deep layer
forcing here very weak as shortwave tracks well n thru northern
Ontario, coverage of new convection may be limited as suggested by
the NAM high res window/NCEP NMM and NSSL WRF. Kept pops mostly in
the chc range. As for svr storms, not expecting any svr storms this
morning as convection will be weakening. New storms that develop
either later this aftn or more likely tonight will be in an
environment of mlcape 1000-1500j/kg. While deep layer shear is
generally 25kt or less, 30-40kt shear is not far to the n and ne.
So, not out of the question that there could be an isold svr storm.

.LONG TERM...(Tuesday night through Monday)
Issued at 257 PM EDT MON AUG 29 2016

Nam shows a 500 mb trough coming onto the west coast 00z Wed with a
ridge in the Rockies and northern Plains. A shortwave digs se out of
Ontario Tue night and affects the area Wed. This shortwave digs into
the lower Great Lakes and New England on Thu. This shortwave stays
far enough away though that it should remain dry for Tue night
through Thu. Overall, did not make too many changes to the going

In the extended, GFS and ECMWF show a 500 mb ridge building into the
upper Great Lakes 12z Fri with a deep trough on the west coast and
another over the east coast. This ridge builds into the lower Great
Lakes with the trough in the western U.S. 12z Sat with warmer air
moving into the area. The trough slowly moves into the Rockies 12z
Sun with some shortwaves ejecting out of it into the plains and
Great Lakes region and pattern changes little 12z Mon. A sfc front
stalls out northwest of the area Sun into Mon. Temperatures will be
above normal this forecast period. Will be dry Thu night through Sat
before front gets close enough to have some chance pops in the far
west Sat night through Sun and then have chance pops in for Sun
night into Mon.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 133 PM EDT MON AUG 29 2016

Expect VFR conditions at all 3 terminals to continue into the evening
hours. Additional shra/tsra will probably develop this evening as a
cold front drops into the area from the west. Confidence in coverage
and whether any of the terminals will be affected is low. So, for
most part only a VCSH was included in fcst. MVFR cigs could develop
at SAW for a few hours late tonight/early Tue morning in the wake of
the frontal passage...otherwise expect VFR conditions at the taf
sites through much of the period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 408 AM EDT MON AUG 29 2016

Expect winds mostly under 20kt through early this week as pressure
gradient remains generally weak. Stronger NW to N winds with gusts
to 25 kts may occur on Wed as a high pressure ridge builds toward
the area in the wake of cold front passage early on Tue morning.
Eastern Lake Superior would be favored for the stronger winds. Winds
diminish to less than 20 kts rest of the week as high pressure moves
across. S to SW winds increase to around 20 kts on Sat as pressure
gradient tightens btwn the exiting high and sharpening sfc trough
over the Northern Plains.

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


SHORT TERM...Rolfson
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