Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 222041
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
341 PM EST Wed Feb 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 245 PM EST WED FEB 22 2017

A mid-level front lifting through northwest Wisconsin into Upper
Michigan has allowed a narrow band of light rain develop this
afternoon. Further upstream across the northern plains, a shortwave
continues to rotate towards the Upper Great Lakes Region, with cold
air filtering southward from Canada.

It has taken the low-levels a bit to moisten this afternoon, but
expect this light rain to continue to lift northeast across the area
as the mid-level front traverses Upper Michigan. Given the
convective nature of the mid-level front, a few locations across
western and north central portions of Upper Michigan could see a
brief period of moderate rainfall through the evening. However, with
the band quickly lifting northeast, the better mesoscale lift will
be displaced northeast of the area. The attention then turns to the
above mentioned shortwave that will lift across the area tonight
bringing another chance for precipitation. As the main vort-max
arrives and colder air begins to filter southward, expect rain to
transition over to snow across the west and portions of the central
Upper Michigan. Thermal profiles do not look terribly impressive, so
do not expect SLRs to be high. Therefore, even though snow will
finally return to the area do not expect much in the way of
accumulations. Locations right along the lake shore and across the
higher terrain will have the best chances at seeing any accumulating
snowfall with north to northwest onshore flow.

Thursday morning, as the deeper moisture vacations the region
soundings show the potential for lingering precipitation, primarily
across the north wind snow belts. The question will be if cloud top
temperatures will be cold enough to support the production of ice.
With the 850mb temperatures only progged to drop to around -6 to -
8C, could see a mixture of light snow and freezing drizzle in the
north wind snow belts. Across the east, temperatures look like they
will be just warm enough to support drizzle, versus freezing
drizzle. Expect precipitation across the area to diminish through
the late morning hours, but cloud cover will linger across much of
the area. With the colder air dropping down from Canada, expect
temperatures to become more seasonable during the day on Thursday,
while still remaining 5 to 10 degrees above normal.

.LONG TERM...(Thursday night through Wednesday)
Issued at 340 PM EST WED FEB 22 2017

Beginning Thu night into Fri...Models in fairly good agreement
indicating waa/isentropic ascent will quickly translate ne thru the
Upper Lakes late Thu night/Fri morning downstream of the deepening
system over the Plains. Additional forcing will be provided in the
right entrance of a 100kt upper jet lifting n across the Upper Lakes
to near James Bay. NAM remains an outlier, being deeper and a little
farther ne with the mid level low over the central Plains at 12z
Fri, which explains the much stronger push of isentropic ascent and
thus heavier pcpn moving across Upper MI late Thu night and Fri
morning. Have favored the consensus of the other models in showing a
less aggressive push of isentropic ascent into Upper MI. This surge
of pcpn will be all snow. With mixing ratios around 3g/kg avbl in
the 700-750mb layer, could see a general 2-4in snowfall with this
initial batch of snowfall thru early Fri aftn. Models then show
fairly strong indications that mid level dry slot may push into
central and eastern Upper Mi Fri afternoon into Fri evening which
would result in a transition toward mainly -fzdz/-dz at times
until a change back to just snow by late Fri night Sat morning.
Meanwhile, diminishing deformation snow shield will streak up thru
the w half of the fcst area. Northeast winds veering to north
late Fri night and then to northwest on Sat along with the column
cooling will support development of lake enhancement off Lake
Superior, and this will be the biggest factor for boosting snow
totals later Fri into early Sat. Unfortunately, there is decent
uncertainty in how much overlap there will be between favorably
cold column for lake enhancment, and deep layer synoptic forcing
before system pulls out. Not to mention uncertainty with the depth
of the synoptic moisture when best enhancement would occur. Right
now, the window when all these elements come together looks
fairly short. In the end, with snow accumulations drawn out over a
longer time of 36-48 hours rather than 12-24hrs, confidence is
poor in reaching warning criteria snowfall amounts. Thus, winter
storm watch headlines will not be issued at this time, although
may end up issuing a SPS since snow will be on the wet/heavy side,
so plowing/shoveling will be more difficult. The wet snow along
with possible fzdz mixed in as well will make travel conditions
hazardous. Finally, gusty winds will lead to some blowing snow,
especially in open areas more exposed to Lake Superior.

Transition to diminishing LES off Lake Superior will occur during
Sat. Some light LES may continue thru Sun/Mon.

Heading into the midweek period, attention turns to the next
shortwave dropping down the W Coast Sun/Mon. The 12z runs of the GFS
and ECMWF are in remarkable agreement for Tue into Wed with the
timing/track of this shortwave and its quickly deepening sfc low as
it moves through the Great Lakes region. The track of the sfc low
across central Lower Mi and Georgian Bay in the GFS/ECMWF scenario
would target south central and eastern Upper Mi for at least
moderate synoptic snow accumulation with lighter accumulation
tapering to the nw. Enhanced lake snow could also add a few more
inches to total snow accumulation into north central counties with
this storm track. The 12z Canadian Model was much more progressive
and much farther west with the storm track which would argue for the
bulk of initial pcpn to be mixed ptype across much of the CWA Tue
night before colder air wrapping behind the system changes over
remaining pcpn over to snow late Tue night into Wed.  Given expected
model uncertainty out this far in the fcst will utilize model
consensus for fcst details/pops for Tue-Wed time frame but lean
toward predominant ptype of snow per ECMWF/GFS soln.
&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1254 PM EST WED FEB 22 2017

A fairly narrow band of rain has developed along a mid-level front
across northwest Wisconsin. This band will continue to lift
northeast through the afternoon and evening hours impacting KIWD
first and then KCMX/KSAW bringing reduced visibilities, lowering
ceilings, and light rain. Depending on where the band sets up,
visibilities could drop a little lower than MVFR or be just above
MVFR. Later this evening, as a shortwave moves across the area,
additional lift will push through the area and impact all
terminals. This additional lift will also come with a cold surge,
and allow rain to transition over to snow this evening/tonight.
Towards the morning hours as the deeper lift vacations the region,
depending on how cold cloud top temperatures can stay, could see
some freezing drizzle mix in with the snow.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 245 PM EST WED FEB 22 2017

Tonight into Thursday morning as low pressure lifts out of central
Wisconsin across lower Michigan, the surface pressure gradient will
increase, along with subsidence, resulting in increased northerly
winds of 20 to 30 knots. Late on Thursday, expect the winds to
decrease in speed to around 15 to 20 knots. Thursday into Friday as
a storm system begins to organize across the Central Plains, flow
will become northeasterly and begin to increase to around to 20 to
30 knots, especially across western portions of the lake. As the
system gets closer during the day on Friday, expect northeast gales
of 35 to 40 knots to develop. As the system moves just to our south,
expect northeast winds to back to the north with gale force gusts
still possible Friday night into Saturday. Through much of the
weekend expect north winds 20 to 30 knots. By Sunday afternoon the
winds will begin to weaken to around 15 to 25 knots as the winds
back westerly. Monday through Tuesday, winds will become southerly
at around 20 knots.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
  Dense Fog Advisory until 10 PM EST this evening for LMZ248-250.

&&

$$

SHORT TERM...Ritzman
LONG TERM...Voss
AVIATION...Ritzman
MARINE...Ritzman



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