Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 130523
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
123 AM EDT Fri Oct 13 2017

.SHORT TERM...(This evening through Friday)
Issued at 412 PM EDT THU OCT 12 2017

WV imagery and RAP analysis indicated a mid/upper level ridge from
the Gulf Coast to the ern Great Lakes and a trough over the nw CONUS
resulting in sw flow from the plains to the nrn Great Lakes. At the
surface, srly flow was strengthening over the upper MS valley and
nrn Great Lakes between a ridge over Quebec and nrn New England and
a cold front/trough from nrn Manitoba into the cntrl Dakotas. The
southerly winds have also brought in enough to low level moisture to
support an extensive area of low clouds over much of the region.
However, there was enough dry air over the ern cwa along with
additional daytime mixing for at least partial clearing over the
west half of Upper Michigan.

Tonight, Low level RH fcst and satellite trends suggest that clouds
will fill back into the area this evening. 925-900mb winds veering
from s to sw late and increasing to 30-35 knots will provide enough
low level lift to sustain the low clouds and possibly produce some
drizzle where srly upslope flow prevails and especially where
additional moistening occurs off of Lake Michigan, such as locations
from ISQ-ERY overnight.

Friday, A low pressure system is expected to lift ne through Hudson
Bay dragging a cold front across the Upper Michigan. Limited
moisture transport and weak forcing along and ahead of the cold
front may only result in a narrow band of isolated to scattered
light showers or sprinkles along the frontal passage.

.LONG TERM...(Friday night through Thursday)
Issued at 414 PM EDT THU OCT 12 2017

Only significant impacts in the long term are due to winds and waves
late Sat through late Sun.

Models have generally trended farther N and strong with a shortwave
and SFC low. For the most part there are two camps with the low
track/strength. The GFS and NAM are very similar in deepening the
low from around 1,000mb over SW WI 00Z Sun to mid 990s mb over S-
central Upper MI 06Z Sun to 986mb over far eastern Lake Superior 12-
15Z Sun, then quickly E into Quebec by 18Z Sun. The CMC and ECMWF
are weaker, only deepening to the mid 990s mb, and tracking farther
south over northern Lake Michigan and eastern Upper MI. Still plenty
of uncertainty with the exact track and strength so definitely favor
the blended guidance for winds. Current "middle of the road"
forecast has increasing E-NE winds Sat afternoon into early Sat
night, but nothing significant over land through that time. Winds
switch to N-NNW through the rest of the night while increasing up to
gusts up to 35mph in land areas near central and western Lake
Superior. Stronger NW winds and CAA then kick in Sun morning and
early afternoon, with shorelines gusts to 45-50mph east of
marquette, and gusts of 35-45mph elsewhere near Lake Superior. Winds
then decrease Sun evening and night. This will lead to waves in
excess of 8ft along all exposed Lake Superior shorelines in the CWA,
and in excess of 12ft east of Marquette. Last season we saw beach
erosion issues at 8ft and lakeshore flood issues around 14ft.
However, lake levels are 6 inches higher than this time last year,
so those thresholds may be lower. Of course, if the NAM/GFS
solutions verify, winds will be stronger, with potential for
shorelines gusts to 60mph. If the ECMWF/CMC verify, winds will be
weaker. Will continue to promote the impacts in the HWO/EHWO.

Only changes made to blended initialization was to pull winds to
downwind shore areas late Sat through late Sun. Otherwise, no
significant impacts expected and blends performed well.
&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 123 AM EDT FRI OCT 13 2017

Advection of low-level moisture around high pressure to the east of
Upper Michigan has resulted in large area of stratus over the
region. MVFR conditions to IFR conditions are expected tonight
through the early morning hours Friday. There could also be some
light drizzle or sprinkles tonight into Friday morning. By late
Friday morning into early Friday afternoon, drier air will begin to
push in from the west allowing for steadily improving conditions as
a cold front pushes to the east of the area. Most sites will likely
become VFR by late morning and remain VFR through the rest of the
TAF period at each site.

&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 412 PM EDT THU OCT 12 2017

...NE to N gales possible on Lake Superior Sat night into Sun
afternoon...

A tightening pres gradient btwn high pres to the e and low pres
tracking ne to s central Canada will lead to an increase in srly
winds to generally 15-25kt across much of Lk Superior through
tonight. Winds will diminish slightly for Fri/Fri night as
weakening cold front associated with low pres tracking to Hudson
Bay moves across the Upper Lakes. New low pres will then lift ene
along the frontal boundary this weekend, passing across the Great
Lakes Sat night/Sun morning. Depending on the strength of the low
and cold air moving in behind the low, there may be a period of NE
to N gales Sat night into Sun morning over the west half of Lk
Superior and then Sun morning into mid Sun afternoon for the east
half of Lk Superior. Winds should be down to less than 20 kts by
Mon.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLB
LONG TERM...Titus
AVIATION...KEC
MARINE...JLB



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