Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 162223

Area Forecast Discussion
National Weather Service Marquette MI
523 PM EST Sat Dec 16 2017

.SHORT TERM...(This evening through Sunday)
Issued at 413 PM EST SAT DEC 16 2017

WV imagery and RAP analysis indicated confluent wnw mid/upper level
flow through nrn Ontario and the nrn Great Lakes. light erly flow
prevailed between high psressure over nrn Ontario and a trough and
front from the cntrl plains through the srn Great Lakes. Vis loop
showed a small clear area over cntrl Upper Michigan but with low/mid
clouds moving in from the west with increasing 280k isentropic lift.

Tonight, lingering east flow off of Lake Michigan with 850 mb temps
around -8C may support some light lake effect pcpn. With marginal
moisture to -10C for ice nuclei, freezing drizzle will also be
possible from near MNM to ESC. Otherwise, veering winds to srly over
Lake Superior will keep any pcpn off shore. Favorable radiational
cooling over the east should allow temps to drop near zero.
Otherwise, clouds will keep temps mainly in the 10 to 15 range.

Sunday, there may be some lingering light pcpn east near Lake
Michigan. Pcpn associated with a shortwav trough moving through nrn
Ontario, will remain north of the cwa. Even with considerable
clouds, WAA will push temps into the mid 20 to around 30.

.LONG TERM...(Sunday night through Saturday)
Issued at 337 PM EST SAT DEC 16 2017

Monday night through Wednesday afternoon: A broad trough sweeping
across southern Canada will brush the CWA Monday night into Tuesday.
Some light snow showers will accompany this trough across mainly the
northern CWA late Monday evening into early Tuesday morning. Colder
air aloft that would be sufficient for LES will lag the main trough
axis, so more prominent LES will hold off until a secondary surface
trough crosses the west Tuesday afternoon and the east Tuesday
evening. Though LES will be generally weak early Tuesday, gusty
W/WNW winds to 45mph across mainly the Keweenaw Peninsula combined
with a loose snowpack may create intermittent whiteout conditions
Tuesday into Tuesday evening. The same will likely hold true near
Lake Superior east of Munising Tuesday afternoon and evening. A
period of moderate lake effect snow for the W to NW wind snow belts
is then expected Tuesday night before diminishing from west to east
on Wednesday.

Wednesday night through Saturday: Though there remains a lot of
uncertainty in the forecast during the second half of the week, the
main message is that more active weather with accumulating snow will
affect at least portions of the western Great Lakes Wednesday night
through Friday.

A potent mid-level trough moving onto the NW CONUS Tuesday night
will become stretched across the central CONUS by Thursday
afternoon. The extreme positive tilt with the northern portions of
this trough complicate the forecast across the Upper Great Lakes by
Wednesday night. Somewhat disorganized lee cyclogenesis in the
Plains will spread a shield of WAA precip across the region
Wednesday evening into Thursday. Guidance has been quite
inconsistent on the placement of the generally narrow swath of
precip, with the GFS switching from the northern-most solution
yesterday to a much more open southern track with today`s 12Z
guidance. The GEFS and other long-range guidance only increase
uncertainty with a wide distribution of solutions. With that said,
there is a relatively high chance of at least some accumulating snow
across the CWA with this system Wednesday night into Thursday.

By Friday and Saturday, model disagreements grow substantially, with
some solutions suggesting chances of an organized system bringing
accumulating snow across the region as the upper trough receives a
re-enforcing shot of energy from the north. Again, with significant
uncertainty this far out, those with holiday travel plans should
continue to monitor forecast updates.

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 523 PM EST SAT DEC 16 2017

MVFR conditions will continue for most of this forecast period at
all sites as srly low level flow with increasing moisture advection

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 413 PM EST SAT DEC 16 2017

Southwesterly winds will increase late Monday to 20 to 30 knots
before veering to northwesterly gales to 35-45 knots late Mon night
through Tue night. With increasing wave heights, freezing spray is
possible Tuesday night into Wednesday.

Upper Michigan...
Lake Superior...
Lake Michigan...


LONG TERM...Kluber
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