Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 062135
Area Forecast Discussion
National Weather Service Marquette MI
435 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 night through Tuesday)
Issued at 434 PM EST TUE DEC 6 2016
An extended period of LES is expected into Saturday as the first
batch of cold air moves through with n to nw winds. Models suggest
that a progressive pattern will prevail into next week. High latitude
blocking near Alaska will favor an intrusion of severe arctic cold
next week as the mid level low and core of coldest air drops through
cntrl Canada into nrn Ontario.
Wednesday night, timing differences remain with the passage of the
trough that will support an area of sharp low level conv and sharply
veering winds with the higher res models bringing this feature
through btwn 06z-12z through the Keweenaw into n cntrl Upper
Michigan. 850 mb temps to around -11C with deep moisture over the
area will provide favorable instability for moderate to heavy LES.
Snowfall amounts in the 2 to 4 inch range are expected, greatest
from Rockland through the Keweenaw.
Thursday and Thursday night, wind direction in the 340-350 range
will favor the greatest snow accumulations over the west near IWD
and n cntrl from Marquette into the Huron Mountains. However,
confidence in the details about where the heavier or dominant bands
will develop (with the influence of land breezes and upstream bands
from Lake Nipigon) is still low. Snowfall amounts in the 2 to 6 inch
range per 12 hours will be common. Confidence in warning amounts is
highest over the west near IWD, but the event not developing til
late Wed night, opted to retain the watch/advisories. There will be
some areas of blsn but overall winds are expected to remain at or
below 30 mph limiting impacts from reduced vsby or drifting.
Friday into Saturday, Winds will gradually back go the nw then wnw shifting
the heavier LES into the ern CWA toward Alger county eastward while
light to moderate LES persists over the west.
Saturday night-Sunday, a shortwave trough moving from the nrn plains
into the Great Lakes late Saturday night into early Sunday may bring
a widespread few inches of snow to the area. Some lake enhancement
may be possible near Lake michigan with the sse low level flow and
850 mb temps around -9C.
Sunday night-Tuesday, Some LES may develop behind the trough into
Monday for nw flow locations. The more significant blast of arctic
air and continued w to wnw flow LES is expected to move in by late
Tuesday with 850 mb temps dropping to near -25C.
.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.
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
Lake Effect Snow Advisory from 1 AM Thursday to 7 PM EST Friday
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-