Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 062013

Area Forecast Discussion
National Weather Service Marquette MI
313 PM EST Tue Dec 6 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 313 PM EST TUE DEC 6 2016

Visible satellite imagery this afternoon shows the cloud layers
along the eastern half of the U.P. are less thick; however, a narrow
band of snow with a light wintry mix along the front edge was
pushing east from the Keweenaw to Iron Mtn. Hi-Res forecast guidance
indicates this band will continue to progress east with thickening
cloud cover. Within the band strong forcing was taking place, as a
result of some narrow convergence, which is producing significant
reductions to vsbys to around 1/2 mile, but not expecting this will
last for longer than a couple hours before ending. Guidance
indicates a lull in precip just prior to sunset thru 2-3z when wrap-
around moisture slides east. Pressure gradient will tighten back up
with good height falls by 3-6z, which will usher in gusty west winds
to around 30-35mph. It is possible in the higher terrain locations
gusts could approach 40 mph at times. Not expecting any wind
headlines overnight into Wed.

Main concerns heading into midday Wed, will be on the developing
lake effect snow machine for the Keweenaw. Winds will be turning
westerly to northwesterly with much colder air advecting southeast,
profiles indicate good moisture within the DGZ coupled with good
vertical lift of parcels, so expect a good band or two to develop
over the Keweenaw by Wed aftn. Coupled with the falling snow and
reduced vsby`s, mixed layer should be bringing to the surface gusts
throughout the day to around 25-30mph and with increased snow-liquid
ratio`s around 20:1, this should easily result in blowing snow and
could further reduced vsby`s in the late afternoon hours.

.LONG TERM...(Wednesday through Monday)
Issued at 506 AM EST TUE DEC 6 2016

Very busy with the forecast for tomorrow through Fri night as a
couple shortwaves move through and colder air leads to LES.

Most uncertain with start times of the snow and associated
headlines. Don`t have a lot of time to provide details here so will
keep it brief. Models differ on if a compact SFC low will move
across northern Lake Superior Wed morning or if it will just be a
trough crossing as a shortwave moves across the area. If the low
develops, snow will likely move into the Keweenaw very early on Wed
(possibly even before 12Z) and may be very heavy. The GEM drops over
0.60" of QPF just Wed morning, which is backed up by the NCEP WRF
ARW. If that doesn`t occur, then amounts closer to what is in the
forecast are expected as flow will be WSW early and gradually
turning SW and W...then NW late. Models also differ on when to drop
the SFC trough across the rest of the area, which should allow for a
hefty burst of snow right along the trough. Set headline start times
to match best expectation for when the trough moves in, but
adjustments may need to be made. Another area of uncertainty is
eastern Marquette and western Alger Counties. Models show N to NNW
winds, which will drive the LES and the Lake Nipigon band somewhere
into this area. Of course, that makes the snowfall forecast highly
volatile in the north-central U.P. See the forecast and hazard
products for more info.

With focus on the forecast through Fri night, let blended
initialization handle the forecast from Sat on.

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 110 PM EST TUE DEC 6 2016

Narrow band of moderate snow was approaching KIWD stretching
southeast, and this band will continue to lift northeast towards KCMX
later this afternoon. CIGS are mainly MVFR across TAF sites, but
expect some light snow/rain and possibly fzra/sleet may accompany
precip between 23z and 01z before it transitions over to all snow for
KSAW. At KCMX precip should remain as all snow through TAF period,
however a brief lull in snow does appear favorable with some minor
improvements to CIGs back to MVFR and possibly VFR. Winds will be on
the increase from the southwest overnight, with gusts developing to
around 28-32kt thru daybreak Wed. Lgt snow will redevelop and coupled
with the gusty winds will likely further reduce VSBYs by daybreak Wed
with low end MVFR conds returning.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 313 PM EST TUE DEC 6 2016

No changes to current marine headlines. While a brief lull in gales
conditions are expected for the western portions of Lake Superior,
further west across Central Minnesota surface observations indicate
gusty winds returning to around 35kts. Expect this channel of higher
gusts to eventually return to the western portions of Superior. As a
result will leave the gales going in the western zones and including
the nearshore zones up to the western side of the Keweenaw. Along
the tip of the Keweenaw a boat earlier had reported gusts to 50kt,
but this appear to be a local enhancement due to the narrow
convergence that was taking place. Expect the convergence zone to
shift east and dissipate with a more sustained low-end gale
conditions overnight into Wed for the western half. Further east, it
is possible gales may need to be introduced; however, expect the
gradient to slacken off, so will hold off on any open water
headlines for Wed at this time.

Winds will eventually shift northwest and with much colder air
sliding across Lake Superior from Canada, this coupled with winds
mainly between 25-30kt and occasional gales to 35 kt will allow
waves to easily build later in the week.

Upper Michigan...
  Lake Effect Snow Advisory from 1 AM Thursday to 7 AM EST
     Saturday for MIZ006.

  Lake Effect Snow Watch from late Wednesday night through Friday
     evening for MIZ002-004-005-009.

  Lake Effect Snow Advisory from 7 AM Wednesday to 7 PM EST Friday
     for MIZ001-003.

  Lake Effect Snow Advisory from 1 AM Thursday to 7 PM EST Friday
     for MIZ084.

Lake Superior...
  Gale Warning until 10 AM EST /9 AM CST/ Wednesday for LSZ162.

  Gale Warning until 7 PM EST /6 PM CST/ Wednesday for LSZ240>243-

Lake Michigan...


SHORT TERM...Beachler
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