Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 142036

Area Forecast Discussion
National Weather Service Marquette MI
336 PM EST Tue Nov 14 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 335 PM EST TUE NOV 14 2017

Tonight into Wednesday: The main focus for this time period will be
precipitation associated with a low pressure system sliding from
southern Manitoba eastward into Lake Superior and Ontario.  An
associated cold front is progged to shift from the Northern Plains,
tonight, into the far eastern U.P. by Wednesday afternoon.
Initially, late this afternoon into the early evening hours, the
moisture will be fairly shallow, leading to mainly drizzle/very
light rain and some fog across the area. Widespread forcing and
deeper moisture along and ahead of the front, by mid to late
evening, will lead to widespread precipitation across much of the
U.P. Soundings show that the lower levels of the atmosphere are warm
enough that the precipitation should mainly fall in the form of rain
tonight through early Wednesday afternoon. After the low shifts to
the east and frontal passage occurs by early afternoon, winds will
shift to the west, then northewest by mid to late afternoon. As
colder air advects into the area on the back side of the low, expect
breezy conditions to develop through the day with gusts as high as
25 to 35 mph along the Lake Superior shoreline during the mid to
late afternoon. Wrap-around moisture along with uplope westerly flow
over the western U.P. will allow rain showers to continue through
much of the day before transitioning to snow by late in the
afternoon. As temperatures continue to cool aloft, expect lake
effect snow showers to begin developing by late Wednesday afternoon,
probably closer to 00Z/16 before the lake effect really gets going,
mainly over the western U.P. 850mb temperatures by 21Z-00Z are
progged to drop to around -4C to -6C over the western U.P. while the
central and eastern U.P. sees 850mb temps around 0C to -3C. Lows
tonight are expected to be mainly in the mid 30s with daytime . This
would only be marginally favored for lake enhancement over the far
west by late Wednesday afternoon.

.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 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1236 PM EST TUE NOV 14 2017

MVFR conditions will be IFR/LIFR at KSAW in fog/low stratus/rain
through early Wednsday morning before slowly improving by Wednesday
afternoon. Ocassional MVFR conditions at KCMX/KIWD will also lower
down to LIFR tonight in heavier rain and fog. Slow improvemnt will
occur at the western TAF sites during the afternoon, before lake
effect/enhanced snow showers develop.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 335 PM EST TUE NOV 14 2017

South winds will gust to 20-30 kts through tonight as the pressure
gradient tightens between departing high pressure and low pressure
tracking over south central Canada. The low will cross Lake Superior
and northern Ontario Wednesday morning with northwest gales to 35
kts over all but far western Lake Superior Wednesday afternoon into
Wednesday night. Gale warnings are in effect from late Wednesday
afternoon into Thursday morning. Winds will diminish Thursday but
strong winds are expected again Fri-Sun as a strong low pressure
system tracks from Upper Great Lakes to eastern Canada. At the least
there will be 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 Warning from 6 PM Wednesday to 10 AM EST Thursday for

  Gale Warning from 4 PM Wednesday to 7 AM EST Thursday for

  Gale Warning from 4 PM Wednesday to 4 AM EST Thursday for LSZ263.

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



LONG TERM...Ritzman
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