Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181138

Area Forecast Discussion
National Weather Service Marquette MI
638 AM EST Wed Jan 18 2017

.SHORT TERM...(Today and tonight)
Issued at 412 AM EST WED JAN 18 2017

No major systems expected to impact the weather in the Upper
Peninsula for the short-term portion of the forecast. The main
features to note are the upper-level ridging that is building across
the area today and tonight and high pressure, at the surface,
sliding through the area. Initially, the area will be under a
tighter pressure gradient today, which will lead to occasional
breezy conditions, most notable along the shorelines of the western
U.P. Temperatures today will be in the upper 30s to around 40, with
the best chances to see low 40s being over the west half of the U.P.
where skies are expected to remain mostly clear. The high pressure
system slips a bit farther south and east tonight, which will allow
the pressure gradient to relax and winds to become light out of the
south to southwest. The combination of lighter winds and mainly
clear skies will allow temperatures to drop into the low 20s. This
may cause some issues with black ice formation from any snowmelt
that occurs today. In addition to the cooling temperatures, fog may
also develop as the increased radiational cooling sets up a
temperature inversion. The best time for this to happen is after
midnight and will mainly occur for inland locations.

.LONG TERM...(Thursday through Tuesday)
Issued at 425 AM EST WED JAN 18 2017

Large scale pattern evolution indicated by longer range guidance for
well over a week is proceeding largely as forecasted. Negative
height anomalies over AK are expanding thru the Gulf of AK and will
expand farther s down the w coast and into Mexico by the weekend. As
this occurs, positive height anomalies currently dominating much of
the CONUS into s central/se Canada will consolidate into a strong
anomaly centered over northern Ontario/Hudson Bay. The location of
this positive height anomaly will force arctic air almost completely
out of N America, except for the high Canadian arctic and AK and
vcnty. 850mb temp anomalies are fcst to peak at 3 standard
deviations above long term late Jan climatology across northern
Ontario this Fri/Sat and 2-2.5 above climatology across Upper MI.
Thus, unseasonable warmth will continue for the remainder of this
week with the potential for some record high max and/or min temps.
Thru at least the first half of next week, the positive height
anomaly will remain intact and only shift slightly to become
centered over Hudson Bay/Quebec. This will continue to prevent any
build up of arctic air in Canada. In fact, the very cold conditions
currently over AK and far northern Canada will even moderate as
arctic air shifts farther n. As for pcpn, the strong positive height
anomaly to the n will force the strongest shortwave energy streaming
into the western states on a southern route across the southern
CONUS. Energy that does peel n will weaken as it moves toward the
positive height anomaly. Thus, the fcst area shouldn`t see any
significant pcpn thru this weekend, Despite it being late Jan, the
unseasonable warmth will mean pcpn that does occur will be liquid,
and there could be a few days when light rain and drizzle occur,
which would be very unusual for this time of year. After the
weekend, there are indications that the final batch of energy in the
series impacting the western states will make a stronger run into
the Great Lakes than its predecessors, weakening the positive height
anomaly to the n and ne, and at least bringing some potential of
accumulating snow back to the area mid week. Farther down the line,
while there are some indications of renewed troffing into eastern
Canada as we flip the calendar to Feb, there doesn`t appear to be a
strong connection to arctic air yet. So, while trending cooler next
week and into the last days of this month, temps will still remain
above normal.

Beginning Thu, NAM/GFS fcst soundings maintain a dry column under
500mb ridging over the area. The only exception is near the sfc,
roughly the lowest 1kft where saturation is indicated. At some point
during this warm spell, low clouds/stratus will become an issue, but
whether Thu is the start of the cloudy period is uncertain. For now,
will keep sky condition on the optimistic side for Thu. If the day
ends up mostly sunny, temps will easily rise into the 40s away from
any marine layer influence.

Mid level low over the central Plains Thu will open up and lift
negatively tilted up into the Great Lakes late Thu night thru Fri
night. Despite negative tilt, only modest forcing/weak isentropic
ascent is indicated by models to swing thru Upper MI. This should
lead to at least some -ra lifting across the area late Thu night and
Fri. Some of the model solutions indicate enough height
falls/evaporative cooling for a mix with snow over western Upper MI.
At this point, given the warm air dominating the area and shortwave
weakening with time, will maintain ptype as liquid. However, with
temps dropping into the upper 20s Thu night prior to pcpn arriving,
some -fzra will be possible into the morning hrs on Fri.

Would expect extensive cloudiness to then prevail thru the weekend
behind this shortwave. Along with cloud cover, precipitable water
for much of the time is in the upper portion of late Jan
climatology, so min temps which will likely stay above freezing
across the area should be in record territory. Record high min temps
at NWS Marquette are 27, 28, 31, 35 respectively from the 20th to
the 23rd. If clouds dominate, max temps won`t rise significantly
from the mins, running generally in the upper 30s/lwr 40s. Another
shortwave lifting n to the w of the area Sat into early Sun may
generate more -ra. Otherwise, there will probably be some -dz at
times thru the weekend.

A more significant shortwave/low pres system will then cut
underneath the positive height anomaly in Canada and track from TX
late Sat to the se CONUS by Monday. This system in concert with
troffing extending back nw to the northern Plains may work to bring
a better chc of pcpn, likely just -ra, to the area on Mon.

It then appears that the last significant shortwave in the series
impacting the western states will lift ne, reaching the Great Lakes
midweek. Falling heights/cooling column at that time will begin to
support ptype changing to mostly snow. Some accumulating wet snow
certainly possible Tue night/Wed.

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 634 AM EST WED JAN 18 2017

Generally expecting VFR conditions at each of the TAF sites
throughout the day as high pressure slides into the area. There
could be some llvl wind shear this morning, mainly at KSAW where
more stable conditions have allowed inversion to strengthen. Light
winds tonight and mostly clear skies will allow fog to form once
again at each of the TAF sites; however, the lower visibilities
will most likely be over the KSAW and KIWD sites.


.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 412 AM EST WED JAN 18 2017

Expect winds to become west southwest up to 25-30kt through early
afternoon as the pressure gradient tightens between a high pressure
passing through the Lower Great Lakes and low pressure crossing
central Canada/Hudson Bay. As the low continues eastward and the
pressure gradient weakens, winds will diminish later this afternoon
into tonight. For the remainder of the week and into the weekend,
expect winds under 20kts as conditions become unseasonably warm over
the Upper Lakes with no significant weather features impacting the

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


LONG TERM...Rolfson
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