Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 200926

Area Forecast Discussion
National Weather Service Marquette MI
426 AM EST Fri Jan 20 2017

.SHORT TERM...(Today and tonight)
Issued at 355 AM EST FRI JAN 20 2017

An upper shortwave and accompanying SFC trough are slowly moving
toward the area from the SW, which has led to a wide band of showers
from SW lower MI to E MN early this morning. That precip is expected
to shift through the CWA, mainly from late morning through the
evening. As it moves in, temps along the WI border may still be cold
enough for some freezing rain, but think the threat it minimal since
models are slowing the leading edge. Some models suggest that
measurable precip will not move into the area until at least 15Z
today, which would furthers minimize the freezing rain threat. There
could be some slick roads over the south-central CWA today, so will
continue to highlight that in an SPS. On the flip side, temps may be
cooling to freezing just as the back edge of the precip is pulling
out of E Upper MI this evening, leading to another minimal threat
for icing. Light rain or drizzle will persist closer to the WI
border this evening and tonight, some of which could start freezing
to surfaces as temps fall to around freezing.

The fog, dense at time and in some locations, will continue for the
most part into tonight. Fog should be more dense into this morning.

.LONG TERM...(Saturday through Thursday)
Issued at 425 AM EST FRI JAN 20 2017

As negative height anomalies continue to expand from AK s across the
western CONUS to northern Mexico over the next few days, a strong
positive height anomaly now centered over northern Ontario will
strengthen and become centered over Hudson Bay. During the early and
middle part of next week, this positive height anomaly will expand
to cover most of Canada. This will prevent any build up of arctic
air in Canada and will even shunt bitter cold conditions currently
over AK and far northern Canada even farther n. 850mb temps will
peak over the next couple of days, supporting continued unseasonable
warmth. With cloud cover to dominate and with a lack of any low-
level caa, expect some record high min temps to be set. 2 or 3 days
should see min temps failing to fall to 32F. As for pcpn, a series
of vigorous shortwave trofs will impact the western CONUS thru early
next week. As they shift e, the strong positive height anomaly to
the n will do 2 things, either force that energy on a track well s
of here or weaken shortwaves that do lift ne thru the Plains. End
result will be that Upper MI should be spared from receiving any
significant pcpn thru early next week. Despite it being late Jan,
the unseasonable warmth will mean that pcpn that does occur will be
only liquid, very unusual for the climatologically coldest period of
the year. Beginning Mon, but more so Tue/Wed, gradual height falls
rather than advection of a colder air mass will lead to a cooling
column, supporting a ptype transition from rain to eventually all
snow. Toward the middle of next week, there are still 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. Given the persistence of the positive height anomaly
to the n, it remains to be seen if a system lifting thru the Plains
will manage to bring significant pcpn into Upper MI. At a minimum,
expect at least light accumulations of snow in the midweek period.
Farther down the line, it appears that the positive height anomaly
dominating Canada early next week will consolidate into western
Canada, allowing for development of eastern Canada troffing late
next week thru the last days of this month. This may send a decent
shot of colder air into the area for next weekend, dropping temps
back to near normal and certainly generating LES. Canadian ensembles
indicate some deamplification after the cold shot next weekend, so
temps will probably end up a little above normal heading to the
1st of Feb.

Beginning Sat/Sun, abundant low cloudiness will prevail behind the
shortwave swinging n thru the area today/tonight. Along with low
cloud cover, precipitable water in the upper portion of late Jan
climatology will support unusually high min temps which will likely
fail to fall to freezing. Record high min temps at NWS Marquette are
28F, 31F, 35F, respectively for the 21st to the 23rd. If low clouds
do dominate as they should, max temps won`t rise much from the mins.
Could certainly see only 2-3 degree swings from mins to maxes,
something like mins of 33/34 and maxes of 35/36. One or more
shortwaves lifting n, mainly to the w of the area, Sat/Sun may
generate some -ra. Otherwise, expect some -dz at times thru the

A much more significant shortwave/low pres system will track
underneath the positive height anomaly in Canada, from TX late Sat
to the se CONUS by Mon. While this system will be much too far s and
se of the area to bring pcpn, sfc/mid level troffing extending back
to the Upper Mississippi Valley should work to maintain some chc of
-ra thru Mon. Best chc of rain will be along and e of the sfc trof.
Exact location of the sfc trof is uncertain, but right now, it
appears that it may cut nw to se across Upper MI from the Keweenaw
to northern Lake MI. So that will mark the position for denoting
higher pops. Cooling column under height falls may support a mix
with wet snow over the higher terrain of the w.

Models still indicate that the last significant shortwave in the
series impacting the western states will lift ne, reaching the Great
Lakes midweek. Continued falling heights and cooling column will
mean a ptype transition to just snow, if not for Tue, certainly by
Wed. CMC continues to be more suppressed with the wave than the GFS,
and indicates the main synoptic pcpn shield staying s of Upper MI.
The 00z ECMWF has shifted a bit farther n, but not as far n as the
GFS. Both would bring the synoptic snow shield into Upper MI, though
the GFS much more aggressively. GFS ensembles overall support the
operational GFS, but a number show an even farther n track. A good
number of the CMC ensembles are similar to the GFS track, just
delayed about 24hrs. So, it would seem there is a decent potential
for a period of widespread synoptic snow at some point in the Tue
Night to Thu time frame. Whatever happens, the positive tilt of the
large scale trof in which the stronger shortwave is emedded suggests
that a wrapped up strong system is unlikely. So, snow accumulations
midweek will not be significant, but more in the light to mdt range.
Some LES should follow the system.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1127 PM EST THU JAN 19 2017

Very challenging aviation forecasts at the TAF sites this period
continues. Trapped low level moisture below a fairly strong
temperature inversion, will keep fairly low ceilings (VLIFR) in
place at SAW and will move back into CMX. More moisture moves in
late tonight and Friday, which should ensure lowering ceilings and
visibilities for each of the TAF sites through Fri night.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 355 AM EST FRI JAN 20 2017

A relatively weak pressure gradient over the Upper Great Lakes in
the absence of any strong weather systems will result in winds under
20 kts over Lake Superior most of the time into early next week.

Upper Michigan...
  Dense Fog Advisory until 11 AM EST /10 AM CST/ this morning for

Lake Superior...
Lake Michigan...


LONG TERM...Rolfson
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