Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 172235
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
535 PM EST Sun Dec 17 2017

.SHORT TERM...(This evening through Monday)
Issued at 356 PM EST SUN DEC 17 2017

WV imagery and RAP analysis indicated mainly zonal flow through the
nrn CONUS and srn Canada with a shortwave trough over nrn Ontario
near CYPL. At the surface, weak srly flow prevailed as high pres
moves to nrn New England and low pressure develops over the plains.
Radars indicated weak returns from nw Wi into Upper Michigan with
sfc reports showing some light snow over far nrn WI.

Tonight, expect the light snow, supported by 800-600 fgen to slide
through the cntrl and ern cwa this evening. However, with only weak
to moderate forcing and little moisture inflow, only lower end POPs
were included with little or no accumulation expected. Any lingering
light snow should end by around 06z.

Monday, southwest winds will increase as a deep low moves through
cntrl Canada to far nw Ontario. WAA will help push temps above
seasonal averages with highs in the lower to mid 30s. A shortwave
moving toward nrn MN, with upper level div in the left exit of the
250-300 jet, may help to spread some light snow into wrn Lake
Superior and possibly into the far wrn cwa late.

.LONG TERM...(Monday night through Sunday)
Issued at 347 PM EST SUN DEC 17 2017

Monday night through Wednesday: A series of embedded trough axes
rounding a broad mid-level low over Hudson Bay will brush the CWA
the during this time. A strong surface pressure gradient juxtapose
with a favorable isallobaric wind will promote gusty W/WNW winds
late Monday night into Tuesday evening. 925-850hPA winds of 40-45kts
should allow for surface gusts to 40mph across the Keweenaw
Peninsula late Monday night through much of Tuesday. Though 850hPa
temps of just -10 to -12C and reduced residence time from the
stronger winds will limit LES intensity, intermittent white out
conditions will be possible given the added component of blowing
snow from the current snowpack. This concern will also translate to
the immediate shore of Lake Superior from Munising eastward Tuesday
evening.

As noted, LES should be limited early on Tuesday, but a secondary
trough axis will bring more favorable thermodynamic conditions for
LES Tuesday evening. A period of moderate LES will be possible for
the W to NW wind snow belts Tuesday night into Wednesday before
lowering inversion heights subdue the LES into Wednesday evening.

Wednesday night through Sunday: As can be expected this time of
year, model guidance continues to show decent run-to-run differences
with the evolution of the large scale pattern and associated period
of active weather across the western Great Lakes. The main message
is that high-impact weather may affect early holiday travel
somewhere across the region during this time.

Light WAA snow should spread across the CWA late Wednesday evening
into Thursday morning, producing sub-advisory accumulations across
the SW half of Upper Michigan. Guidance begins to diverge after this
as notable disagreement develops with the handling of lee
cyclogenesis in the central and southern Plains as a mid-level
trough ejects from the four corners region. Contrary to yesterday,
the GFS has become the strongest and northern most solution with
this low, bringing a period of high-impact snowfall to Upper MI late
Thursday morning into Friday night. The ECMWF and CMC model bring a
broader swath of moderate snow across Upper MI Thursday evening into
Friday, keeping more significant precipitation well south of the
region. Again, given the highly varying solutions, providing any
detailed forecast is nearly impossible at this point. However, those
who could be affected by moderate to heavy snow accumulations in the
western Great Lakes Wednesday night into Saturday should continue to
monitor forecast updates through the upcoming week.
&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 535 PM EST SUN DEC 17 2017

There is enough low level moisture upstream that conditions will
continue to be in the IFR/LIFR range for the most part tonight. More
substantial dry advection with improving conditions is expected
Monday afternoon with improving conditions.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EST SUN DEC 17 2017

Southwesterly winds will increase to 20 to 30 knots Monday over the
west and north central portions of Lake Superior possibly reaching
gales late Mon afternoon and evening before veering to northwesterly
gales to 35-40 knots late Mon night into Tue night. With increasing
wave heights and colder air temperatures, freezing spray is possible
Tuesday night into Wednesday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Gale Watch from late Monday night through late Tuesday night for
     LSZ243>245-264>267.

  Gale Watch from Tuesday morning through Tuesday evening for
     LSZ162-241-242-246-247-263.

  Gale Watch from Tuesday morning through late Tuesday night for
     LSZ248>251.

Lake Michigan...
None.
&&

$$

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



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