Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 161145

Area Forecast Discussion
National Weather Service Marquette MI
645 AM EST Mon Jan 16 2017

.SHORT TERM...(Today and tonight)
Issued at 508 AM EST MON JAN 16 2017

Water vapor imagery and RAP analysis show a well-defined shortwave
moving across the TX panhandle/OK. Another shortwave across
MT/Saskatchewan will play a role in the track of this southern
stream wave over the next 24-36hrs. Current confluent flow resulting
from the ridging ahead of the southern stream wave and the more
zonally oriented flow from S central Canada to New England is
supporting sfc high pres ridging/deep dry air mass from MN eastward
across Lower MI. Thus, mostly clear skies have dominated the fcst
area overnight. A few of the traditional interior cold spots where
winds are decoupled have fallen into the single digits with Peavy
Falls the coldest at 2F.

Today will be quiet under deep dry air mass. As the aforementioned
southern stream shortwave lifts ne, there will be a gradual
increase/thickening of high clouds from the s thru the day, most
noticeable across the S central. For the most part, however, much of
the area will see mostly sunny skies today. As the sfc high pres
ridge just s of the area drifts n, light winds be the rule across
the area by mid to late aftn. High temps will reach the low to mid
30s, though a few spots may approach 40F.

Tonight, attention turns to the what impact the southern stream
shortwave will have on the fcst area. Models are in good agreement
on the flow aloft, indicating that the shortwave currently over
MT/Saskatchewan will drop se, but not have enough interaction on the
southern stream wave to pull it sharply N. In the end, it will track
ne, passing across SE Lower MI Tue morning. As isentropic
ascent/deep layer forcing lift N and weaken while approaching Upper
MI tonight, antecedant dry air mass will have an impact on slowing
and diminishing the approaching pcpn area. That said, in this case,
there won`t be a strong high to the N and E to support a continued
feed of dry air, so the incoming pcpn will likely make progress into
S central Upper MI tonight. The big question will be how far N will
the pcpn move and what form will it take. Given the antecedant dry
air mass and the track of the shortwave a good distance SE of here,
leaned toward the models showing a more suppressed northward
advancement of pcpn tonight. Fcst will show schc pops reaching no
farther N than roughly an Iron River to Newberry line, and pops will
ramp up to categorical in southern Menominee County. As for ptype,
fcst soundings for Menominee from the NAM/GFS show a deep isothermal
layer around 0C once saturation occurs. Result would be all snow if
it`s no warmer than 0C, but if the deep layer is just above
freezing, then pcpn would be FZRA. The slighty warmer ECMWF and even
more so CMC raise the prospect for mostly FZRA as ptype. For now,
fcst will reflect mostly snow with some FZRA. In the end, the fcst
for Menominee County is a big challenge. Some of the models, NAM in
particular, bring a healthy dose of pcpn up to a half inch or so to
the southern part of the county. If that occurs and it`s all snow,
that will be significant since the snow will be very wet/hvy. If it
ends up mostly FZRA, then ice accumulations will be significant.
Given the still significant spread in the operational models and
ensembles, have opted to hold off any headlines for Menominee
County. Stay tuned for updates later today.

.LONG TERM...(Tuesday through Sunday)
Issued at 503 AM EST MON JAN 16 2017

Challenging forecast in the early part of the extended with regards
to precipitation type and amounts.

The biggest weather impact during the extended will be early in the
extended forecast as an area of low pressure slides across lower
Michigan into Southern Ontario Tuesday. At the same time, added
support will be given from shortwave energy progged to link up with
the surface low. Model differences continue with respect to the
amount of precipitation and warm air that lifts into the area;
however, models are still trying to push the system a bit farther
south and east for the most part. This would mean that there would
be lower QPF with the system and that colder air will remain in
place. At this point, it looks like the system would only impact the
south central portion of the U.P. and areas east especially near
Lake Michigan. The precipitation will generally be in the form of
snow as it begins; however, there may be a bit of a light freezing
rain or rain mixing in throughout the day as temperatures through
the profile will be nearly isothermal along the 0C line.
Temperatures in the morning will be near freezing at the surface
before warming into the mid 30s by early afternoon, which may make
roads slippery Tuesday morning. Again, this would mainly be south
central and east. Precipitation totals will be very light as the
west half will likely see no precipitation and the east will only
see a tenth or less. The exception may be over the far south central
U.P. where liquid QPF may be closer to the 0.10 to 0.20 range. This
would yield a sleet/snow mix of up to an inch with a tenth of an
inch of ice accumulation or less expected over the south central and
east. This may still cause some travel headaches Tuesday morning,
with any ice accumulation that does occur.

The system will quickly exit Tuesday night allowing for fairly quiet
and warmer weather through the end of the work week with little to
no chance of precipitation. This will be due, in large part, to a
broad 500mb ridge building across much of the central part of the
U.S. At the surface, much of the U.P will be influenced by the
northern edge of a broad surface ridge. As the ridge slides eastward
through Friday, winds will become southerly, helping to edge
temperatures into the above normal category into the upcoming
weekend, probably reaching into the upper 30s to around 40. The next
area of low pressure is progged to slide just west or over the
western half of the U.P. Saturday, which would lead to continued
warming; however, the chances for, mainly rain, would steadily
increase for the first part of the upcoming weekend. Another system
is progged to move across the central U.S. toward the end of the
upcoming weekend into the next week, which could give chances of
precipitation; however, confidence in any one model solution is
limited at best. Have gone with a consensus of the models for this
time period.

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 645 AM EST MON JAN 16 2017

A deep dry air mass currently over Upper MI will continue to prevail
at KIWD/KCMX/KSAW thru this fcst period, resulting in VFR

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 508 AM EST MON JAN 16 2017

Winds initially this morning up to 20-30kt across Lake Superior will
diminish to under 15kt by late aftn as a high pres ridge lifts n to
the Upper Great Lakes. Winds will then remain mostly under 15kt thru
Tue as pres gradient remains weak across the area. Winds may
increase upwards of 20-30kt late Tue night into Wed. For the
remainder of the week, expect winds mostly 20kt or less as
conditions become unseasonably warm over the Upper Lakes with no
significant weather features impacting the area.

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


SHORT TERM...Rolfson
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