Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 270750

Area Forecast Discussion
National Weather Service Marquette MI
350 AM EDT SAT AUG 27 2016

.SHORT TERM...(Today and tonight)
Issued at 349 AM EDT SAT AUG 27 2016

SW flow aloft is present downstream of deep trough scntrl Canada
into the northern plains. Main surface front is well to the south of
Upper Michigan as close as northern Missouri and central Illinois
but clusters of elevated shra/tsra due to lead shortwave energy are
rapidly moving northeast across Wisconsin within right entrance
region of jet streak that is lifting across Upper Great Lakes. As
the shortwaves lift across central and east cwa today, expect
showers over Wisconsin to spread across much of cwa while a weak sfc
wave of low pressure forms and crosses eastern cwa. It is closer to
the track of the sfc low where likely pops will be highlighted. Btwn
the lead shortwave/wave of sfc low pressure and the deepening trough
over the northern plains there may be a min in activity over western
cwa so will keep pops lowest over far west and temps warmest in the
low 70s. Even after showers move through over central by early aftn,
south to southeast winds may help light drizzle or isold showers
persist over north central cwa. Heaviest rain amounts should stay
just southeast of cwa on northern edge of where MUCAPEs are 500-1000
j/kg. Could see isold lightning strikes over far southeast cwa but
most area should stay free of thunderstorms today.

Upper trough moving to Northern Ontario/Minnesota this evening
should spread at least scattered showers and possible thunderstorms
over northwest to north central cwa by this evening. Strongest q-
vector convergence slides more across Lk Superior so the rain
showers should stay focused more over northern cwa for the evening.
Strong q-vector divergence and resulting subsidence will end showers
after midnight for all areas. Expect enough clouds to linger to keep
fog from developing but if clearing occurs earlier in the night
certainly could see some fog as winds will be light.

.LONG TERM...(Sunday through Friday)
Issued at 349 AM EDT SAT AUG 27 2016

Sunday through Sunday night: Another shortwave will slide through
the Upper Great Lakes Region Sunday afternoon into Sunday evening,
which may bring some isolated showers and thunderstorms. MUCAPE
values are progged to be around 400 to 700 J/kg across the area
during the afternoon and evening hours. The main forcing mechanism
will be an approaching warm front during the late afternoon and
evening hours. Otherwise, winds will be fairly light across the area
with a trend toward above normal temperatures as the warm front
passes through overnight. Highs will be in the mid to upper 70s with
overnight lows in the mid to upper 50s.

Monday through Tuesday: A surface low, over northern Ontario Monday
morning, will slide to near James Bay by Tuesday afternoon. As this
happens, the low will drag and associated cold front across the
Upper Great Lakes region. The best timing for the frontal passage
looks to be Monday night over the west and central U.P. and the
eastern U.P. Tuesday morning. Along and ahead of the cold front,
warm moist air will slide northward into the Upper Great Lakes
Region. The warm, moist air will create unstable conditions across
the area allowing showers and thunderstorms to form with the forcing
associated with the cold front. MUCAPE values are progged to be
around 1000 to 1500 J/kg ahead of the front. Deep layer shear values
are not overly impressive at or around 20 to 25 knots, with the
stronger shear expected behind the front. There may be a couple
stronger thunderstorms if the higher CAPE values are realized;
however, the lack of shear would lean against organized/widespread
strong to severe thunderstorms. The increase WAA ahead of the cold
front will allow temperatures to warm well above normal Monday with
many locations warming into the low 80s. Normal highs this time of
year are in the low 70s for comparison. High pressure will build
across the U.P. from the west by Tuesday afternoon allowing
conditions to dry out once again and skies to clear from west to

Wednesday through Thursday: High pressure will continue to build
across the Upper Great Lakes region through this time period,
keeping conditions mainly dry under partly cloudy skies. Aloft, flow
will be under slight troughing to near zonal flow through this time
period which will keep temperatures near normal.

Friday through the Extended: Models begin to vary quite a bit during
this time period ranging from nearly zonal flow to a fairly good
ridge axis sliding across the Plains. At this point have decided to
stick with a consensus of the models until the models merge toward a
similar solution from run to run and model to model.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 141 AM EDT SAT AUG 27 2016

High pressure sliding overhead tonight will keep conditions VFR at
all the TAF sites. Mid to high clouds will increase late tonight as
the high center slides east and winds turn south southeasterly ahead
of another system. This next system will bring rain and lower
ceilings Saturday into Saturday night, especially near KSAW where
upslope southeast winds will help produce lowered ceilings.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 349 AM 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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