Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 112241

Area Forecast Discussion
National Weather Service Marquette MI
541 PM EST Sat Nov 11 2017

.SHORT TERM...(This evening through Sunday)
Issued at 341 PM EST SAT NOV 11 2017

Lake enhanced snow N of Lake Michigan is resulting in a narrow band
of moderate snow over far southeastern Schoolcraft County and into
far southern Luce County. This will continue to slowly shift E and
diminish this evening.

Meanwhile, a shortwave N of the MN arrowhead will move across
northern Lake Superior by 06Z tonight. 850mb temps will drop to -6C
to -8C behind the shortwave and remain that temp through Sun. A SFC
trough will settle over Lake Superior behind the shortwave, and will
remain in place through Sun. Expect an area of snow showers near
Lake Superior over the W and the Keweenaw this evening through early
tonight, then will become isolated late tonight. Light, isolated
snow showers are then possible in NW wind snowbelts Sun, but no
significant accumulations are expected. There is a slight chance
this could be drizzle/freezing drizzle due to DGZ dryness, but the
moist layer goes up to -9C to -10C with decent lift just below and
into the -8C to -10C layer, so most likely will be all snow as is
normally the case in that scenario.

.LONG TERM...(Sunday night through Saturday)
Issued at 326 PM EST SAT NOV 11 2017

Compared to guidance viewed yesterday, last 24hrs of medium range
model runs show no notable changes in the large scale pattern for
the upcoming week. A strong ridge will remain nearly stationary over
the N Pacific for at least the next 7-10 days. On most days, daily
500mb height anomalies centered mostly over the Bering Sea will be a
very impressive 400+m. This positive height anomaly will force
persistent troffing downstream over the ne Pacific. Shortwaves
ejecting from this ne Pacific trof will progress downstream across
the northern CONUS in lower amplitude/more progressive flow
underneath a mean closed mid-level low over far northern Canada.
With lower amplitude/progressive flow the rule, temps across Upper
MI should fluctuate within a few degrees of mid Nov normals on most
days over the next 7 days (normal high temps are generally in the
upper 30s to lwr 40s). As for pcpn, after todays pcpn, little in the
way of rain/snow is expected until Tue night when the next shortwave
and associated cold front arrive. Conditions will be warm enough so
that this round of pcpn Tue night/Wed morning will be all rain. A
stronger shortwave and low pres system is still on track to affect
Upper MI late in the week. Ptype will probably be a mix of rain and
snow initially before becoming all snow.

Beginning Sun night/Mon, at best, air mass will be marginally cold
enough to support LES. In reality, with shallow moist layer
potentialy not extending to -10C for ice nuclei activation, any pcpn
could be in the form of -dz/-fzdz. That said, other than weak sfc
troffing across Lake Superior, don`t see much to generate pcpn given
weak wind fields to limit upsloping. Given that every model shows
some pcpn Sun night, will retain only low schc pops where winds are
onshore off Lake Superior. If there is any very light pcpn Sun
night, that pcpn should end Mon morning as sfc high pres ridge
arrives over the area and air mass begins to moderate.

Next more significant shortwave will move out across the Northern
Plains Tue aftn/evening and will reach the western Great Lakes Wed
morning. Ahead of this wave, gradual strengthening of waa/isentropic
ascent during Tue could yield some -ra, but it looks like it will
take some time to erode dry air in the mid levels. Much better
potential of -ra will arrive Tue night into Wed morning when deep
layer forcing and cold front associated with shortwave arrive.
Models continue to be in good agreement on timing this feature. Rain
will exit the western fcst area Wed morning and the e in the early
aftn. Will be blustery behind the front on Wed, especially over the
Keweenaw where winds will probably gust upwards of 40mph given 35kt
winds in the mixed layer. Medium range models have trended slightly
colder with air mass following fropa, dropping 850mb temps down
toward -10C. Combined with sharper cyclonic nw flow than indicated
in previous model runs, there is a better chc of some LES to develop
into Wed night/Thu morning.

A much stronger shortwave ejecting from the ne Pacific trof will
reach the Upper Great Lakes late week. Medium range models are
trending toward a more similar solution, though much can and
probably will change given the time range into the model runs.
Trends are toward a slightly more delayed strengthening of the
shortwave and associated sfc low as it moves across the Great Lakes.
Given the progressive flow next week, that`s not unreasonable. This
would result in a more impactful system affecting areas e and se of
Upper MI. That said, given strong, farther w recent days guidance
from the GFS/ECMWF, including some 12z GFS/CMC ensembles that wrap
up a deep system farther w (there are actually more deep 12z CMC
ensembles compared to 00z), this will continue to be a system to
monitor late next week for potential of strong winds/signficant
pcpn. As it stands now, it appears that a couple of unorganized sfc
lows will track toward the Great Lakes Thu night, one moving into
northern Ontario and the second moving into the mid Mississippi
Valley. The second low will become the main low as it winds up
heading thru Lower MI Fri and across southern Ontario to sw Quebec
on Sat. Rain and/or snow should develop Thu night and continue into
Fri before transitioning to blustery nw flow LES into Sat.

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 540 PM EST SAT NOV 11 2017

Conditions will stay mostly mvfr for this forecast period at all
sites. Light snow and lowered conditions are expected tonight into
early Sunday at KIWD and KCMX.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 341 PM EST SAT NOV 11 2017

Winds will continue to be 20 to 30 knots this evening. By Sunday
morning, winds will further diminish to around or less than 15
knots. Expect these lighter winds to linger through Monday as high
pressure tracks across the region. Tuesday, southerly winds will
increase to 20 to 30 knots as the pressure gradient strengthens
ahead of an approaching cold front. This front is expected to track
across Lake Superior on Wednesday, with W-NW gales to 35 knots still
looking possible late Wednesday into Wednesday night.

Upper Michigan...
  Winter Weather Advisory until 10 PM EST this evening for MIZ007-

Lake Superior...
Lake Michigan...


LONG TERM...Rolfson
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