Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 172111

Area Forecast Discussion
National Weather Service Marquette MI
411 PM EST Sat Feb 17 2018

.SHORT TERM...(This evening through Sunday)
Issued at 410 PM EST SAT FEB 17 2018

WV imagery and RAP analysis indicated cyclonic wrly flow through the
n cntrl CONUS around a deep mid/upper level low west of Hudson Bay.
A shortwave trough over WI supported an area of light snow that has
from far srn Upper MI through ern WI into nrn IL. Drier low level
air further north has limited coverage of the pcpn into the rest of
the cwa. Another signficant upstream shortwave was moving through
the Pacific Northwest.

Tonight, any remaining snow over the far s or se cwa will move out
during the rest of the afternoon, per radar/satellite trends.
Otherwise, favorable radiational cooling conditions overnight should
allow temps to drop into the single digits over inland locations
before mid/high clouds increase from west to east late.

Sunday, a broad area of WAA and isentropic lift will strengthen as
the shortwave move through the nrn plains. Models suggest that the
heaviest band of snow will move through nrn MN into wrn Lake
Superior and mainly the Keweenaw Peninsula. There is still some
uncertainty with the snowfall amounts as the ECWMF/NAM and
regional GEM remained or trended farther north compared to the GFS
with higher QPF axis. So, an advisory was issued only for the
Keweenaw where the highest amounts are likely. With 2-3g/Kg
moisture avbl and a period of intense lift and mid level fgen,
local amounts in the 3 to 6 inch range will be possible. Farther
south amounts should range from 1 to 3 inches over most of the
rest of the nrn half of Upper Michigan.

.LONG TERM...(Sunday through Friday)
Issued at 454 AM EST SAT FEB 17 2018

Most attention remains on Sun through Mon when a couple rounds of
light to moderate system snow are expected.

Snow associated with a shortwave Sun has been trending more N/NW
with latest model runs. The s-central looks to see little to no
snow, while the NW half of Upper MI is forecast to be closer to 4-6
inches. Elsewhere generally 2-4 inches is expected. However, there
remains uncertainty in exact track and magnitude of QPF, and locally
higher amounts are possible depending on details of possible FGen
banding over the NW. Snow ratios will be around 20:1 and winds will
be breezy but not too windy. An advisory looks to be a good call,
but will let the day shift have a final look at trends.

The next system remains pretty uncertain, but models have trended
lower with QPF/snowfall, which makes sense given the setup.
Generally have 2-5 inches of wet 10:1 ratio snow Mon and Mon
evening, with lesser amounts under 2 inches near Lake Michigan where
some light freezing rain is possible. Still hard to pin the ice
forecast down given the uncertainties. Looks like a solid advisory
level event for much of Upper Michigan at this point. Certainly
plenty of room for models to change, so continue to monitor.

Could see another couple inches of snow Mon night and Tue, but does
not look too impactful.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 115 PM EST SAT FEB 17 2018

MVFR cigs at KCMX adied by some lake moisture in wsw flow are
expected to give way to VFR conditions by mid afternoon as drier air
moves in. VFR conditions should then prevail at at all sites into
Sunday morning. Light snow will move into the west at KIWD/KCMX by
late Sun morning with MVFR and possibly IFR vsby by the end of the
period. Cigs should remain MVFR.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 410 PM EST SAT FEB 17 2018

A few southwest gale force gusts to 35 knots are expected Sunday
night over eastern Lake Superior. Otherwise, winds are expected to
stay below gales through the rest of the forecast period.

Upper Michigan...
  Winter Weather Advisory from 9 AM Sunday to 1 AM EST Monday for

Lake Superior...
Lake Michigan...
  Gale Warning from 4 PM Sunday to 1 AM EST Monday for LMZ248-250.



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