Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 162051

Area Forecast Discussion
National Weather Service Marquette MI
351 PM EST Mon Jan 16 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 344 PM EST MON JAN 16 2017

Water vapor imagery and RAP analysis show a well-defined shortwave
over eastern KS lifting slowly ne across the Central Plains.
Another shortwave moving ese across the Dakotas and Manitoba may
play a role in the track of the southern stream wave over the next
24 hrs. Current confluent flow across the area resulting from the
ridging ahead of the southern stream wave and the more zonally
oriented flow from south central Canada to New England is supporting
sfc high pres ridging/deep dry air mass from MN eastward across
Lower MI as noted on 12Z area soundings. Mid clouds are beginning to
spread into Upper Mi today ahead of the southern shortwave
approaching the Great Lakes, but the amount/extent of pcpn from this
wave reaching into Upper Mi will largely depend on steering
influence from northern stream wave and also how long dry very
airmass in place will take to moisten.

Tonight and Tuesday, attention turns to the what impact the southern
stream shortwave will have on the fcst area. Models are in fairly
good agreement on the flow aloft, indicating that the shortwave
currently over Dakotas/Manitoba will drop se, but not really have
much interaction/steering influence on the southern stream wave to
pull it sharply N. Consequently, models in good agreement that the
southern wave will track ne, passing across SE Lower MI Tue morning.
As isentropic ascent/deep layer forcing lifts N and weakens while
approaching Upper MI tonight, antecedant dry air mass will have an
impact on slowing and diminishing the approaching pcpn area. That
said, 12Z models and SREF QPF fields in pretty good agreement that
far southern Menominee County could receive up to .2 inch of QPF but
then QPF amounts taper off quickly to the north with generally
.1 inch or less of QPF into northern Menominee county and across the
rest of the counties bordering Lake Mi and the bay of Green Bay.
Thus, forecast will reflect a sharp gradient from categorical pops
over southern Menominee County tapering to schc pops reaching no
farther N than roughly an Iron River to Newberry line. As for ptype,
fcst soundings for Menominee from the RAP/HRRR/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 likely be FZRA. The warmer Canadian
model and deeper isothermal layer above freezing would further raise
the prospect for mostly FZRA as ptype, which NAM sounding for MNM
generally supports as well particularly late tonight. Given that
most of the model soundings support as least some period of FRZA
over southern Menonimee County, have decided to issue a winter
weather advisory for Menominee County from late this evening into
Tue morning. Given that QPF amounts are much lighter farther north
into Delta and Schoolcraft counties will not issue a headline for
mixed pcpn there. Dickinson, Iron and southern Marquette and
southern Alger will be on northern fringe of pcpn shield with only a
dusting of light snow expected.

Temperatures are expected to rise above freezing by Tue afternoon so
threat of freezing rain will subside at that point. Also forcing
from weakening system will be lifting e and out the area so
expect pcpn in general to be quickly diminishing.

.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 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1239 PM 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 PM Lake Superior forecast issuance)
Issued at 344 PM EST MON JAN 16 2017

Winds diminish to under 15kt and remain mostly under 15kt thru Tue
as the pres gradient remains weak across the area due to sfc ridging
across the area. Winds may increase upwards of 20-30kt late Tue
night into Wed as the sfc ridge moves east and sfc trough pushes east
from the Northern Plains. 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...
  Winter Weather Advisory from 10 PM this evening to 11 AM CST
     Tuesday for MIZ012.

Lake Superior...
Lake Michigan...


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