Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 071011
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
511 AM EST Thu Dec 7 2017

.SHORT TERM...(Today and tonight)
Issued at 511 AM EST THU DEC 7 2017

...Lake effect diminishing east today then more lake effect for WNW
flow areas tonight...

Deep troughing remains in place and that will be the case until
further notice. Main sfc low remains over northern Quebec this
morning with sfc ridge well to the west over central Plains. Cold
northwest flow continues to result in widespread lake effect, though
drying aloft has lead to the most intense snow showers this morning
staying east of Marquette. Couple of stronger bands have developed
overnight, one with connection to Lk Nipegon in Ontario and another
thriving off shoreline convergence off Marquette county. That band
of snow using a 20:1 SLR could be putting down snow accums over 2
inches per hour. Winds backing from NNW to NW are keeping this band
on the move to the east. Since the east will still be in and out of
heavier snow bands this morning, have extended the advisory til noon.
Marquette county advisory will expire at 7 am.

Winds backing west will end the lake effect most areas by early
aftn. Only exception will be over the northwest as WSW to W flow
will bring back in lake effect this aftn. First off the lake effect
should be light with inverisons only2-3kft AGL, but eventually LES
will increase as shortwave over northern Manitoba moves in. Stronger
low-level convergence tied to developing sfc trough and lift in the
DGZ should support moderate to heavy lake effect late this aftn and
more so tonight for areas favored by WNW flow. Lift fm the shortwave
will be strongest late evening into the overnight hours. Expect snow
totals most areas for NW flow areas of the west will be in the 3-5
inch range tonight, but some areas of higher terrain from Rockland
to Houghton could see isolated 8-10 inch amounts. Solid advisory
amounts expected and have went with one from late this aftn into Fri
AM. Gusty winds and blowing snow an issue as well, especially where
strong convergent west winds set up over the Keweenaw. West flow
lake effect will likely drop into far northeast forecast area late
tonight and could need another headline for those areas into Fri.
Will let current headline run its course before putting out another
one.

Away from the lake effect areas, no high impact weather is expected.
Could see some peeks of sunshine especially late morning/early aftn
in between clouds from the lake effect breaking up and mid to high
clouds coming in tonight as shortwave moves in. Most areas could see
some flurries or light snow showers tonight as the shortwave and sfc
trough move through. Highs today upper teens west to mid 20s in the
east. Lows tonight mainly in the teens.

.LONG TERM...(Friday through Wednesday)
Issued at 439 AM EST THU DEC 7 2017

The extended forecast will continue the trend of near to below
normal temperatures along with a very active lake effect snow
pattern through the entire period.

Generally expecting northwesterly flow aloft into the Upper Great
Lakes region, bringing the continued cold air into the area. 850mb
temperatures are expected to be in the -12C to -18C range through
much of the extended, which will be plenty cold enough for continued
lake effect snow downwind of Lake Superior. For the most part, west
to northwest wind favored snow belts will be the favored lake effect
areas; however, there are a couple clipper systems that will drop
850mb temperatures to around -20C and help to turn the winds a bit.

Friday into Saturday: A couple quick moving clipper systems will
slide through during this time period. This will allow 850mb temps
to drop down near -20C, helping to steepen the overwater
instability. The surface pressure pattern would initially favor west
to northwest wind favored snowbelts Friday; however, as a surface
low shifts off to the south of the U.P. Friday night through
Saturday, winds will turn more northerly. This would give most
locations along Lake Superior a good shot at at least moderate lake
effect snow. Snow ratios look to be a little better during the
Friday night into Saturday time period as the wave slides through
with fairly light winds through and below the snow growth layer.
Good forcing and instability in the snow growth layer along with
inversion heights reaching close to 10 kft also point to an uptick
in the snowfall intensity Friday night into Saturday morning. At
this point, blending some hi-res qpf guidance gives several inches
of snow from Friday night into Saturday morning especially for north
wind favored snow belts. The heaviest snowfall totals are expected
over the high terrain of the west and over the high terrain of the
north central U.P. Current thinking is that 4 to 8 inches of fluffy
snow may fall in the aforementioned areas with locally higher totals
possible by early Saturday afternoon. Elsewhere along Lake Superior
will likely see totals around 3 to 6 inches. A headline will likely
be need for this time period, Friday night into Saturday morning.

Sunday into Sunday night: Another quick moving clipper-type system
is progged to slide through the Upper Peninsula. This will again act
to steepen the lapse rates enough to enhance the lake effect snow
downwind of Lake Superior. This will be a similar type setup as the
Friday night into Saturday setup, except not quiet as strong and a
little quicker. Initially the lake effect snow would be confined to
the west wind favored snowbelts Sunday morning; however, as the low
shifts to the east of the U.P., winds are expected to once again
shift to the north and northwest, giving most areas light to
moderate snowfall along Lake Superior.

Monday into Tuesday: Yet another fairly strong shortwave, in the
active weather pattern, will slide through the Upper Peninsula
Monday through Tuesday morning. Winds look to be north to north-
northwest through this time period, allowing for yet another period
of enhanced lake effect snowfall downwind of Lake Superior. Again,
moderate lake effect snow is possible for the north to north-
northwest wind favored snow belts and as is typical, the greatest
totals are expected over the higher terrain of the north central
U.P. and over the higher terrain of the west.

Rest of the Extended: Active cold weather pattern is expected to
continue with another shortwave progged to slide through the area
Tuesday night into Wednesday. At this point, will stick with a
consensus of the models, giving good chances of lake effect snowfall
along Lake Superior, especially in the north to northwest wind
favored snowbelts.
&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1157 PM EST WED DEC 6 2017

Much drier air spreading s across the area overnight into the
morning hrs will cause lake effect shsn to diminish from w to e.
At KIWD, expect prevailing MVFR conditions to improve to VFR this
aftn, then fall back to MVFR this evening as next disturbance
approaches. At KCMX, MVFR conditions should mostly prevail into the
aftn. There may be some brief periods of IFR overnight, then w winds
and an approaching disturbance should lead to an increase in lake
effect shsn at KCMX late this aftn/evening, dropping conditions back
to prevailing IFR. At KSAW, conditions should vary btwn VFR and MVFR
thru the morning hrs before becoming VFR.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 439 AM EST THU DEC 7 2017

Winds are expected to remain in the 20-30 kt range into early next
week as an active weather pattern keeps a fairly tight gradient
across Lake Superior. Freezing spray is expected through Friday
night and again late Monday into MOnday night. Air temps staying
mainly in the 20s should prohibit heavy freezing spray through this
time period.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until noon EST today for MIZ006-007-085.

  Winter Weather Advisory from 3 PM this afternoon to 10 AM EST
     Friday for MIZ001>004-084.

  Winter Weather Advisory until 7 AM EST this morning for MIZ005.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...KEC
AVIATION...Rolfson
MARINE...KEC



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