Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 280721

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

.SHORT TERM...(This evening through Sunday)
Issued at 359 PM EDT SAT AUG 27 2016

Radar imagery shows area of showers over the southeast portion of
Upper Mi generally dissipating and moving east under weakening waa
pattern. Focus now into tonight will shift to area of showers over
the western U.P. which is being supported by increasing q-vector
convergence ahead of mid-level trough and associated shortwave
lifting ene through the Northern Plains toward the Upper Great

With the track of shortwave trough expected to lift more over
western and north central Superior and Ontario tonight models
indicate the strongest q-vector convergence will also stay generally
over the western and northern part of lake and points to the north.
Radar trends and models suggest best chance for sct showers to
numerous shra will likely be confined to far wrn counties of Upper
Mi through this evening into early overnight on edge of best
forcing/dynamics. As shortwave trough lifts well north of area late
tonight, strong q-vector divergence and resulting subsidence is fcst
to spread in fm west and will end showers after midnight for all
areas. There is a concern of some fog forming later tonight as low-
level moisture remains trapped near the sfc under increasing
subsidence...especially with potential for partial clearing.
Southeast upslope flow may also aid fog formation this evening over
central and eastern fcst area where ground will still be moist from
today`s rainfall.

Rising 5h heights and increasing mid-lvl subsidence should result in
dry conditions across the CWA on Sunday. Expect highs mainly in the
70s under mostly sunny/partly sunny skies.

.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 06Z TAFS through 06Z Sunday night)
Issued at 123 AM EDT SUN AUG 28 2016

Weak low pressure sliding across the area will bring continued low
cloud cover through much of the night. There may be some isolated
rain showers at KIWD and KCMX early in the TAF period otherwise
conditions should remain dry. Ceilings at each of the TAF sites are
expected to be MVFR to IFR through much of the overnight hours,
before lifting through the day today as drier air slides into the
area. There may be some fog that forms late overnight if breaks in
the clouds occur. Overall confidence is medium on coverage and
density of the fog; therefore, did not go as low as some guidance
suggests. Improvement will occur at all TAF sites this morning
with VFR this aftn and evening.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 359 PM EDT SAT AUG 27 2016

Winds into next week should remain at 20 kts or less as the pressure
gradient remains weak.

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


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