Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 140900

Area Forecast Discussion
National Weather Service Marquette MI
400 AM EST Tue Nov 14 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 243 PM EST MON NOV 13 2017

...Freezing drizzle possible late tonight into Tue morning...

Quiet at this time, though still mostly cloudy, with high pressure
overhead. Had some slippery roads this morning due to light freezing
drizzle off Lk Superior. Could see repeat of that Tue morning,
mainly over western forecast area as drizzle increases in warm/moist
air advection regime btwn the departing high and sfc low sliding
over scntrl Canada. Already seeing signs of increased near sfc
moisture with cigs blo 010 and fog seen over Iowa/northern Illinois
this aftn. This moisture is projected to lift toward northern WI and
western Upper Michigan after 09z on Tue. South winds not that strong
but any additional upslope lifting/moistening would be maximized
over inland west, especially affecting IWD, LNL and IMT. Temps over
inland west half will not rise above 33-34F until later Tue morning
so with any light drizzle there could be icing potential on
untreated roads. QPF from all the models is very light late tonight
into Tue morning so am going to handle fzdz/icing with a SPS.
Evening shift can put out a winter weather advy if more precip looks
to occur.

Later Tue morning into Tue aftn, expect light drizzle to increase to
light rain especially over central U.P. with south winds off Lk
Michigan adding moisture. Overall even though the most widespread
light rain/drizzle will occur during the aftn, the biggest impact
will likely be during the morning due to the temperatures at or just
below freezing.

.LONG TERM...(Wednesday through Monday)
Issued at 400 AM EST TUE NOV 14 2017

The main forecast highlights continue to be the active pattern
developing across the CONUS, which will allow a couple of systems to
track across Upper Michigan this week through the weekend. Each of
these systems will have different impacts, with lake effect snow
developing on the back side of both. The medium-range models are in
good agreement with the initial system tracking across Upper
Michigan on Wednesday. However, in regards to the second system both
run-to-run and model-to-model inconsistencies continue. Therefore,
considerable uncertainty/low confidence continues for later this
week through the weekend. Expect this trend to continue until the
main upper-level trough comes onshore across the Pacific Northwest
later this week, allowing better upper-air sampling to take place.
Temperatures wise, the middle of the week will be closer to normal,
but overall a cooling trend is expected with afternoon highs only
climbing into the 20s by Saturday. Temperatures will modify into
early next week, but will remain below normal for this time of year.

Wednesday through Thursday: As an upper-level trough digs across the
Upper Mississippi and pivots across the Western Great Lakes, the
associated surface low will deepen as it tracks across Upper Michigan
on Wednesday. By Wednesday morning, the surface low is expected to
be in the vicinity of western Upper Michigan. Therefore, as warm air
advection continues to stream northeast along and ahead of the
surface low, precipitation should remain mostly liquid, especially
across the east where warm air advection will linger through the
day. A few locations could pick up a quarter to one-half inch of
rain, with higher confidence across the east. As the low lifts
northeast of the region Wednesday into Thursday, cold air advection
wrapping around the system bring back favorable wind directions for
accumulating lake effect snow showers. This transition over to snow
should start to occur across the far west in the day on Wednesday,
and then gradually transition eastward across the north-northwest
wind belts Wednesday night. By Thursday morning, expect the lake
effect snow showers to transition to the north wind snow belts as
the combination of return flow developing across the Upper
Mississippi Valley and the exiting 850mb low pressure to our east
allow 850mb flow to veer northerly. Expect generally around or less
than 3 inches of lake effect snow near Lake Superior by Thursday
morning. Given the strengthening trend of this system, Wednesday
night into Thursday morning strong winds across Lake Superior will
allow waves to build to 12 to 14 feet near the shoreline. Therefore,
beach erosion and lake shore flooding look possible, especially east
of Marquette. Areas of blowing snow and reduced visibilities will
also be possible due to the strong and gusty winds.

Through the day on Thursday, inversion heights will lower and the
cold air advection will begin to shut down from west to east as
850mb flow backs southerly. The winds will also calm down throughout
the day, with diminishing lake effect snow showers.

Friday through Sunday: The above mentioned return flow will spread
northward across the region in response to a potent longwave trough
tracking across the intermountain west. Recall from above, there is
still considerable uncertainty with the track, strength, and timing
of this next system. The 00Z runs of the GFS and Canadian still show
what would be a strong fall storm tracking across Lakes Michigan and
Huron Friday night into Saturday. The ECMWF is much further south
and weaker. Ahead of the system, strengthening warm air advection
will allow widespread precipitation to develop. Initially we could
see wintry mix on Friday, but as the warm nose pivots across Upper
Michigan this should allow precipitation to transition over to
mostly rain during the day. However, as the system lifts across Lake
Huron, colder air advection will start to return. This will favor
the transition over to moderate to heavy lake effect snow across the
west, and the potential for accumulating system/lake enhanced snow
across the central and east. Saturday through Sunday, the main upper-
level trough will continue to slowly lift northeast of the region.
Depending on the strength of the cold air behind the system, we
could see lake effect snow showers through the weekend across the
northwest wind snow belts. As 850mb temperatures approach -10 to -15C,
inversion heights will rise and ample lake-induced CAPE is
expected to develop. Forecast soundings also show fairly deep
cloud depths and lift through the DGZ, so expect the lake effect
snow to be quite efficient with high SLRs. Therefore, the
potential is there for heavy lake effect snow Saturday and Sunday.
Given the gusty winds expected, blowing snow will likely be an
issue as well.

Early next week: Confidence is low in regards to how precipitation
chances will play out. However, lake effect snow will likely linger
into Monday before diminishing.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 104 AM EST TUE NOV 14 2017

Mainly VFR conditions overnight. Conditions will deteriorate Tue
morning to IFR at KIWD and MVFR at KCMX and LIFR at KSAW. Conditions
will stay down at KSAW through the period. Could be some light
drizzle/freezing drizzle Tue morning as well.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 243 PM EST MON NOV 13 2017

...Gales at times Wed into the weekend...

South winds increase to 20-30 kts Tue/Tue night as pressure gradient
tightens btwn departing high pressure and low pressure tracking over
scntrl Canada. The low crosses Lk Superior and northern Ontario
Wed morning and expect northwest gales to 35 kts over the east
half of Lk Superior Wed aftn into Wed night. Gale watches have
been posted. Winds diminish Thu but more strong winds are expected
Fri-Sun as strong low pressure system tracks from Upper Great
Lakes to eastern Canada. At the least we`ll see gales with this
system and there could even be storm force winds behind the storm
system Sat Night into Sun morning. &&

Upper Michigan...
Lake Superior...
  Gale Watch from Wednesday afternoon through Wednesday evening
     for LSZ264>267.

Lake Michigan...
  Gale Warning from 9 PM this evening to 8 AM EST Wednesday for



LONG TERM...Ritzman
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