Area Forecast Discussion
Issued by NWS Marquette, MI

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560
FXUS63 KMQT 191807
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
107 PM EST Thu Jan 19 2017

.SHORT TERM...(Today and tonight)
Issued at 408 AM EST THU JAN 19 2017

Warmer than normal temperatures continue through the short-term
forecast with at least one more quiet and dry day expected across
the U.P.

The broad surface ridge that has been giving the mostly clear and
warm weather will slowly shift off the east coast into this evening;
however, a surface ridge will linger across the U.P., to the west of
the high pressure center. Aloft, the 500mb trough axis will continue
to linger across the area through late this evening before shifting
slowly to the east of the areas. Other than some patchy fog and some
low stratus along the WI border this morning, skies should become
mostly sunny today with highs topping out in the upper 40s to low
50s over the west half, with the warmest readings expected in the
south to southwest wind downslope including areas near Keweenaw Bay.
This will again be record or near record high temperatures for
portions of the west half as record high, at least locally, are in
the mid 40s. Over the eastern half of the U.P. the south to
southwest wind across Lake Michigan may end up keep patchy fog or
low stratus in the area for much of the day, which will keep
temperatures in the upper 30s to around 40.

As the aforementioned surface ridge and upper-level ridge axis
shifts out of the area, WAA along with moisture advection will
increase across much of WI late tonight. As this happens, isentropic
ascent will increase. This would allow clouds to increase and
possibly even allow for a light mix of rain and freezing rain far
south central and along the WI border. This could cause some
slippery travel conditions for those areas for the early Friday
morning commute. Again, the chances of the precipitation making into
the area are fairly low at this point as the better moisture and
upglide doesn`t really make it into the area until Friday morning.
Additionally, have pulled the timing of the pops back a bit as
models continue to slow the arrival of precipitation, again, until
after 12Z Friday.

.LONG TERM...(Friday through Wednesday)
Issued at 408 AM EST THU JAN 19 2017

Over the next few days, expanding/deepening negative height
anomalies from the AK/Gulf of AK into the western CONUS and even
Mexico will lead to downstream consolidation of positive height
anomalies into a strong anomaly centered over northern
Ontario/Hudson Bay. This positive height anomaly will then expand to
encompass more of Canada by the middle of next week. This will
effectively prevent any build up of arctic air in Canada and will
even shunt very cold conditions currently over AK and far northern
Canada even farther n. Over the next few days, 850mb temp anomalies
are fcst to peak at 3 standard deviations above long term late Jan
climatology across northern Ontario and 2-2.5 above climatology
across Upper MI. Thus, unseasonable warmth will continue for the
remainder of this week with the potential of additional record high
max and/or min temps, though record high min temps will be more
likely once low clouds lock into place beginning Fri night/Sat. The
potential of record high min temps will probably extend into the
first day or two of next week due to abundant low clouds and
complete lack of any caa at the low levels. Expect several days with
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, and there will probably be several days in which light rain
and/or drizzle occur, extremely unusual for the climatologically
coldest period of the year. Toward the middle of next week, there
are indications that the final batch of energy in the series
impacting the western states may 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 any system lifting
thru the Plains will manage to bring significant pcpn into Upper MI.
At a minimum, cooling generated mostly from height falls rather than
advection will mean a gradual transition back to snow by midweek and
at least some light accumulations of snow. Farther down the line,
while there continue to be indications of renewed troffing into
eastern Canada as we flip the calendar to Feb, there still doesn`t
appear to be a strong connection to arctic air yet. So, while
trending cooler next week and thru the last days of this month,
temps will still remain above normal.

Beginning Fri, a weakening negatively tilted shortwave will be
lifting into the Upper Lakes. Despite negative tilt, only modest
forcing/weak isentropic ascent are indicated by models to swing thru
Upper MI. This should lead to some -ra lifting across the area Fri.
Some models suggest there might be just enough height
falls/evaporative cooling for a mix with snow over higher terrain.
Given the warm air currently dominating the area and the
shortwave/forcing weakening with time, will maintain ptype as just
liquid. However, with temps below freezing tonight, some -fzra will
be possible in the morning as the pcpn lifts n into southern Upper
MI. May require a headline if heavier pcpn reaches the area faster
before temps rise above freezing.

Expect extensive cloudiness to then prevail thru the weekend behind
this shortwave. Along with cloud cover, precipitable water 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 28F, 31F, 35F,
respectively from the 21st to the 23rd. If low clouds do dominate,
max temps won`t rise significantly from the mins, running generally
in the upper 30s/around 40F. Another shortwave lifting n to the w of
the area Sat into early Sun may generate more -ra. Otherwise, expect
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
maintain some chc of -ra thru Mon.

Models still indicate 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 just snow. Positive tilt of the
large scale trof in which the shortwave is emedded suggests that a
strong system is unlikely. So, it would appear that snow
accumulations midweek will be not be significant, but more in the
light to possibly mdt range.
&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1245 PM EST THU JAN 19 2017

Very challenging aviation forecasts at the TAF sites through this
period. While there are some signs on satellite of the stratus
lifting over the southwest U.P. (stratus has lifted at IWD),
stratus and fog still persist across much of the east of the
forecast area and also over portions of the Keweenaw
Peninsula...including CMX and SAW. Still expect some improvement
in visibility later this afternoon at CMX and SAW from VLIFR to
IFR or MVFR, but trapped low level moisture below a fairly strong
temperature inversion, could keep fairly low ceilings (IFR or
lower) in place at CMX and SAW. More moisture moves in late
tonight and Friday, which should ensure lowering ceilings for
each of the TAF sites. There could also be some fog that develops
along with some precipitation for the IWD and SAW TAF sites Friday
morning. Downslope south to southeast wind at IWD should result
in conditions only lowering to MVFR late tonight then gradually
lowering to IFR late Friday morning with the onset of rain.
Southeast winds will be upslope at SAW and allow conditions to
lower to LIFR/VLIFR late tonight into Friday. At CMX, also expect
conditions lowering to LIFR/VLIFR late tonight into Friday
morning.


&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 408 AM EST THU JAN 19 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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...KEC
LONG TERM...Rolfson
AVIATION...Voss
MARINE...KEC



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