Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141223

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

.SHORT TERM...(Today and tonight)
Issued at 432 AM EST TUE NOV 14 2017

...Freezing drizzle possible this morning...then rain developing
later tonight...

Increasing low-level moisture reflected by low stratus clouds over
nw WI has advected north into far western Upper Mi early this
morning in a southerly flow ahead of cold front approaching from the
Northern Plains. Moisture depth is fairly shallow as noted on fcst
soundings (5kft or less) and airmass is dry above and into the DGZ.
The shallow moisture along with the presence of a weak shortwave
trough moving through nw WI has helped generate areas of dz. As this
shortwave moves east into Upper Mi later this morning into early
afternoon, expect low clouds and drizzle to continue to spread east
across Upper Mi through the day. With temperatures expected to be
around or just blo freezing into mid to late morning, there could be
some freezing drizzle into mainly the interior west half of Upper
Mi. The light icing potential could cause slippery conditions on
untreated roads and sidewalks this morning so will continue the SPS
to highlight this potential. As moisture deepens through the column
and DGZ later this evening and overnight Wed morning ahead of the
main shortwave and frontal boundary moving in from the Northern
Plains, expect drizzle to eventually turn into steady rain.

The moist conditions from the drizzle and rain will also lead to the
development of fog especially over the east half counties getting
added moistening and upglide with a southerly flow off Lake Mi.

.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 12Z TAFS through 12Z Wednesday morning)
Issued at 712 AM EST TUE NOV 14 2017

MVFR conditions will lower to LIFR at KSAW this morning in
fog/stratus before rebounding briefly to IFR this afternoon and
then lowering to LIFR again tonight in rain/fog. MVFR conditions
at KIWD and KCMX will also lower down to LIFR late tonight in rain
and fog. &&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 432 AM EST TUE NOV 14 2017

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

South winds increase to 20-30 kts today into tonight as the pressure
gradient tightens between departing high pressure and low pressure
tracking over south central Canada. The low crosses Lake Superior
and northern Ontario Wed morning with northwest gales to 35 kts over
the east half of Lk Superior Wed aftn into Wed night. Gale watches
remain posted. Winds diminish Thu but more strong winds are expected
Fri-Sun as a 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 Thursday morning for

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



LONG TERM...Ritzman
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