Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 060455
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
1155 PM EST Tue Dec 5 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 418 PM EST TUE DEC 5 2017

WV imagery and RAP analysis indicated an amplified pattern with a
mid/upper level trough from Manitoba into the cntrl CONUS. A
vigorous shortwave/intense storm system was lifting north through
Ontario.

This evening into tonight, the tight gradient south of the 969 mb
centered west of James Bay in northern Ontario is still generating
storm force winds over much of central and eastern Lake Superior and
advisory level winds over the Keweenaw Peninsula this afternoon. As
the sfc low gradually fills and lifts slowly ne tonight expect winds
to gradually subside to gales over Lake Superior and blo wind
advisory criteria over the Keweenaw Peninsula. Have already
cancelled the wind advisory across the rest of Upper Mi as west
winds have generally subsiding blo 40 mph.

A shortwave swinging across the Upper Great Lakes will push a sfc
trough across the region late tonight and Wed morning causing winds
to gradually veer from wsw to wnw. This will bring the heavier lake
effect snow now over the Keweenaw peninsula back into Ontonagon and
Gogebic late tonight. Favorable deep moisture within the DGZ along
with 850 mb temps around -16C will support moderate to occasionally
heavy snow tonight into Wed with additional accumulations in the 6
to 10 inch range for Gogebic and Ontonagon and accumulations in
excess of a foot over the Keweenaw and higher terrain locations.

Broad upper troughing will be fully in place on Wed across the
region south of the Ontario storm system. Winds veering NW over
eastern Lake Superior and H85 temps to -16c will support widespread
lake effect into Alger, Luce and Northern Schoolcraft counties. Snow
showers will be enhanced due to widespread deep moisture to H7 or
10kft AGL and favorable positioning of DGZ within the lake
convective layer so snowfall will be efficient. Only negative for
really high SLRs toward 30:1 is mixed layer winds over 25 kts which
will fracture snowflakes. Expect WNW-NW flow areas to see moderate
to heavy lake effect into Wed evening west and over east into Wed
night. Probably looking at 12 hour snow amounts Wed of 3-5 inches
west to 4-7 inches east due to ideal placement of DGZ and higher
inversions up to 10kft. Expect winter storm warning headline over
the Keweenaw to either be extended late tonight or transitioned over
to a winter weather advisory.  Have issued winter wx advisories for
the eastern counties beginning late Wed morning and continuing
through Wed night.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 324 PM EST TUE DEC 5 2017

Deep trough will be parked over the Great Lakes stretching south
through the Ohio Valley for the bulk of the extended periods.
Upstream a high amplitude ridge will remain nearly stationary,
allowing a continued northwest flow. With the locked in cold
airmass, the generation of lake-effect snow seems very plausible for
much of the extended periods. Thur the moisture availability
decreases; however, it is likely that some lake induced moisture
will persist and allow for some light snow showers in the favored
snow belts. Operational guidance continues to prog a clipper system
pivoting southeast along the western periphery of the deep trough
over James Bay late Thur. This clipper will arrive Fri across the
U.P.

With the clipper progged to arrive Fri, guidance indicates good
vertical lift of parcels within the favored dendritic growth zone.
Additionally moisture availability looks promising, which points
towards the potential for some steady moderate LES snow with this
system. Then a brief lull in the steady snow showers Sat, until yet
another clipper is progged to skirt the area late in the weekend.

Beyond the upcoming weekend, it appears the pattern will remain
locked in the northwest flow with periodic clipper systems bringing
light to at times moderate lake-effect snow showers. Temps
throughout the extended will remain in the low/mid 20s, with lows
likely falling into the teens to single digits above zero away from
the lakes.
&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1154 PM EST TUE DEC 5 2017

Combination of lake effect shsn and gusty w winds to around 35kt
producing blsn will result in LIFR conditions with vis frequently
near airfield mins thru this aftn at KCMX. Some improvement is
expected this evening as winds diminish and somewhat drier air
arrives. At KIWD, gradual veering of winds from w to nw will result
in increasing lake effect shsn while gusty winds to 25-30kt create
blsn. Expect prevailing IFR conditions into the morning to fall to
LIFR this aftn/evening. However, as is typical for lake effect,
conditions will likely be quite variable. At KSAW, downslope nature
of the w to nw winds should result in conditions varying btwn MVFR
and VFR with -shsn/flurries at times, though MVFR conditions will
likely become prevailing this aftn/evening.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 457 AM EST TUE DEC 5 2017

Active period on Lk Superior continues until further notice. Storms
expected over most of Lk Superior today into tonight. Winds diminish
to gales into Wed and Wed night. Storm warnings up at this time and
those will need to be transitioned to gale warnings later today or
tonight. Should be down blo gales by daybreak Thu as deep low
pressure in the Lk Superior region moves farther away into northern
Quebec. Winds will stay in the 20-30 kt range into Fri but a clipper
surging through may bring a brief return of N gales Fri night. Most
of weekend will stay with 20-30 kts for winds but more gales from
the NW are possible late Sun as another clipper works through. Bouts
of freezing spray are expected Today into Thu, late Fri and again
late Sun. Air temps staying mainly in the 20s throughout the
weekend should prohibit heavy freezing spray.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 9 AM Wednesday to 7 AM EST Thursday
     for MIZ006-007-085.

  Winter Storm Warning until 5 AM EST Wednesday for MIZ001-003.

  Lakeshore Flood Advisory until 8 AM EST Wednesday for MIZ001>003.

  Winter Weather Advisory until 6 PM CST Wednesday for MIZ009.

  Winter Weather Advisory until 7 PM EST Wednesday for MIZ002.

Lake Superior...
  Storm Warning until 2 AM EST Wednesday for LSZ264>267.

  Gale Warning until 1 AM EST Thursday for LSZ264>267.

  Gale Warning until 7 AM EST Wednesday for LSZ246-247.

  Gale Warning until 4 PM EST Wednesday for LSZ248>251.

  Gale Warning until 1 AM EST Thursday for LSZ244-245.

  Gale Warning until 1 PM EST /noon CST/ Wednesday for LSZ162-
     240>243-263.

Lake Michigan...
  Gale Warning until 7 AM EST Wednesday for LMZ221-248-250.

&&

$$

SHORT TERM...Voss
LONG TERM...Beachler
AVIATION...Rolfson
MARINE...JLA



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