Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 220739

Area Forecast Discussion
National Weather Service Marquette MI
339 AM EDT Sun Oct 22 2017

.SHORT TERM...(This evening through Sunday)
Issued at 315 PM EDT SAT OCT 21 2017

No significantly impactful weather is expected in the short term.

A weak shortwave lifting across the western forecast area today will
bring some isolated to scattered showers and possibly some thunder
to mainly western Upper MI this afternoon. Instability is minimal
with only a couple of hundred j/kg of MUCAPE and with only weak
shear, so only isolated thunder is expected. South winds will gust
to 20-30 mph through the remainder of the afternoon, strongest near
northern Lake Michigan and in downslope areas along the eastern
shore of Lake Superior. Temps under partly sunny skies this
afternoon have climbed to nearly 20 degrees above normal with
highs in the mid 60s to mid 70s.

As a stronger shortwave trough shifts east through the Plains a
cold front will move into the western U.P. later tonight, which
will likely bring in showers and maybe a thunderstorm. Chances
should be confined to mainly the west half through 12Z Sun. Lows
tonight will be 20-25 degrees above normal with lows expected in
the 50s. Record high minimum temperatures will likely be set at
many locations including WFO MQT.

Sunday, the progression of the shortwave trough eastward into the
Upper Great Lakes will push the cold front through the rest of Upper
Mi on Sunday. Fairly vigorous deep layer forcing and abundant
moisture with pwat upwards of 1.3 inches/250pct of normal should
support a band of showers in the vicinity of the front. Very little
instability is forecast along/ahead of the front by 12z Sun and thru
the day Sun (MUCAPE is mostly less than 100j/kg), so no mention of
thunder is warranted. Showers should be out of the w half by late
afternoon but won`t exit the e until mid-late Sun evening. Since
front progresses through area fairly quickly not expecting a lot of
rain despite high pwats Look for the greatest amounts of .2 to
.5 inches over the east half. Skies should clear fairly quickly once
the pcpn ends. Sun will be cooler under clouds/showers and in wake
of passing cold front. Expect highs from around 60F west to
generally mid 60s east half.

.LONG TERM...(Monday through Saturday)
Issued at 339 AM EDT SUN OCT 22 2017

Main story in the long term is potential for a significant storm
system to bring strong winds and very large waves Mon night into Tue

Confidence in this event is still on the low side given model
variability and disagreement, but users of this forecast should
certainly keep aware of potential threats from the system. The CMC
and ECMWF are is decent agreement in showing a sub-980mb SFC low
moving to the SE of the CWA, while the GFS is considerably weaker at
just under 1,000mb. If the stronger consensus of CMC and ECMWF
verifies, Strong winds over and near S-central Lake Superior could
gust to around 60mph along the central and eastern Lake Superior
shorelines, but for now have kept with a more moderate consensus
solution featuring gusts to around 45mph. These winds would lead to
waves over 15ft across S-central Lake Superior, which would cause
lakeshore flooding and beach erosion, especially since the lake
levels are well above normal. Still plenty of chance for things to
change, stronger or weaker than the consensus mean in the forecast,
so stay tuned. Storm total QPF is forecast to be around an inch over
the N-central and eastern UP, with almost all of that being rain.
There is a chance that portions of the interior W could see some
traces of snow Tue night, but at this point not expecting enough for
any impacts.

Attention then turns toward Fri into Sat when another system may
move through the region. Lots of uncertainty with this system, so
will just be using consensus mean and monitoring for now. There is
potential for some more significant snowfall totals with the
strongest/coldest/optimally-placed solutions.

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 133 AM EDT SUN OCT 22 2017

A cold front will move through the area overnight and today,
bringing showers and reduced CIGs from west to east across the
TAF sites. Thunder is possible, mainly over the west, but
potential is very low. LLWS will end at KIWD/KCMX overnight, but
will continue into the morning at KSAW. Improvement to VFR is
expected at KIWD and KCMX by early afternoon with drying behind
the front.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 315 PM EDT SAT OCT 21 2017

South-southeast winds will gust 20-30 kts through tonight, strongest
over the eastern half Lake Superior. Sun, south-southeast 20-30 kts
winds will shift west-southwest in the wake of a cold frontal
passage. Southwest winds will diminish to 15-25 knots Sun night into
Mon. Northerly winds will pick back up again Mon night into Tue as a
low pressure system is expected to rapidly deepen just east of Lake
Superior. North gales are possible late Mon night into Tue evening
with the deepening low but should diminish blo gales late Tue night
into Wed as sfc low weakens and lifts east of the region.

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


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