Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 132245
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
545 PM EST Wed Dec 13 2017

.SHORT TERM...(This evening through Thursday)
Issued at 427 PM EST WED DEC 13 2017

WV imagery and RAP analysis indicated a mid/upper level ridge over
wrn North America and a trough from north of Hudson Bay through the
ern CONUS. A vigorous shortwave torugh that has produced a swath of
moderate to heavy snow from nrn WI into srn upper MI, extended from
se WI into wrn IN. At the surface, a 992mb low was located over srn
Lake Michigan resulting in cyclconic ene to ne flow across the cwa.
Lake enhanced snow (850 mb temps near -17C) into n cntrl Upper
Michigan was transitioning to LES with an area of moderate to heavy
snow.

Tonight: Expect the clipper system snow to slowly taper off into
this evening, per usptream obs over most of nrn WI with lingering 1-
2sm vsby. With amounts up to 8 inches already observed near
Menominee to Stephenson, the winter weather advisory was upgraded to
warning given potential for a few more inches, including some lake
enhancement. In addition to the snow, considerable blowing and
drifting snow will lead to to very poor driving conditions during
the evening commute.

Expect the initial burst of heavier snow around KMQT to also give
way to weaker multiple parallel band LES as subsidence moves in
and the 850-700 mb moisture moves out of the area with weakening
low level convergence. In addition, winds will also steadily back
to nrly this evening and to the nw overnight, shifting the focus
of any heavier bands.

Thursday, As another shrtwv drop toward the area out of Manitoba,
winds will continue to back from nnw to wnw. Even with 850 mb temps
remaining near -17C, inversion heights at or falling below 5k ft
will limite LES intensity. Only 1 to 3 inch amounts are expected for
nw flow favored areas with the greatest amounts from Munising
eastward.

.LONG TERM...(Thursday night through Wednesday)
Issued at 303 PM EST WED DEC 13 2017

...Lake effect Thu night into Fri then warmer late this weekend into
early next week...

Upper troughing and cold continues into first part of weekend. Could
be brief relaxing of upper trough to more of a WNW flow aloft late
this weekend into early next week which may allow us to see temps
push above normal into the lower 30s on Sun-Tue. Primary long range
models (GFS, ECMWF, GEM) along with associated ensembles and recent
runs of longer range CFS indicate any warm up will be brief with
persistent pushes of cold air dropping through again later next week
and on into the rest of the month. Signal continues that it could
get very cold (sub zero lows and single digit highs) just beyond the
end of the long term toward the holiday weekend. We`ll have to wait
and see on that though.

Main weather issue for the long term is bout of moderate to heavy
lake enhanced snow expected Thu night into Fri for the northwest
wind snow belts near Lk Superior. Strong shortwave trough digs down
across Lk Superior and Upper Michigan late Thu evening through early
Fri morning. Similar to recent trends it seems, could see light snow
arriving just in time for Fri morning commute away from the lake
effect areas. Additional shortwave energy drops across Fri morning
through late Fri afternoon but moisture with that wave is less than
the earlier morning wave so probably will not see much widespread
light snow but could see some more flurries. Lake induced troughing
helps low pressure over far eastern Lk Superior deepen from 1013mb
late Thu night to around 1008mb Fri morning. Subtle deepening of the
low, but this will only increase low-level convergence with the lake
effect.

Soundings over west and northwest show lake induced troughing to at
least 10kft AGL with strong lift well within DGZ. Winds in blyr less
than 20 kts into Fri should allow snow to be quite efficient with
SLRs 25-30:1 at least. Winds do look to shift some from W to NNW and
back to NW as the shortwaves move through. Overall, expect moderate
to heavy lake enhanced snow over west and northwest Thu night into
Fri morning. Meanwhile, over the east the low and sfc trough could
disrupt the lake effect over the east with main area of heavier lake
effect possibly shifting out over Lk Superior late Thu night or more
so Fri morning depending on where main center of low ends up. 12z
GEM shows such a scenario while most other higher res guidance still
keeps heavier snow showers in over northeast forecast area. Will
need headlines for this event. At this point, winds and blowing snow
does not look to be big factor. Snow could be very fluffy though so
should see solid advisory but if snow showers can stay anchored
later Thu night into Fri morning certainly a potential for isold
warning amounts of 8"/12 hours. Too much uncertainty where focus for
heavier snow will be to go with a winter storm watch for lake effect
attm, especially since the wind/blowing snow should not be too big
of an issue.

Beyond the lake effect late this week, weekend looks pretty quiet
other than some snow that develops as warmer air works in. Stronger
upper level waves that could focus stronger low pressure systems
remains well to south as it looks now, so think we will be okay in
terms of staying away from stronger low pressure/widespread heavy
snow that can sometimes come with switch from colder pattern to
warmer one. Cold front charging in Tue/Wed of next week will
bring next better chance of widespread snow with more lake effect
by Wed as colder air returns.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 545 PM EST WED DEC 13 2017

As winds back to nrly, lake effect snow showers will return to all
terminals at times with MVFR ceilings and variable reduced
visibilities. Lake effect snow showers will end by afternoon at KIWD
and KCMX and by morning at KSAW.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 427 PM EST WED DEC 13 2017

Winds will remain at or below 25 knots through Thursday night as the
pressure gradient relaxes across Lake Superior. Winds will increase
to 20 to 30 knots late Thursday night through Friday evening as the
next low pressure system develops and strengthens over eastern Lake
Superior. Winds will then remain in the 15 to 25 knots range through
the beginning of the work week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 1 AM EST Thursday for MIZ005.

  Winter Weather Advisory until 7 PM EST /6 PM CST/ this evening
     for MIZ010-011-013.

  Winter Storm Warning until 6 PM CST this evening for MIZ012.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLB
LONG TERM...JLA
AVIATION...07
MARINE...JLB


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