Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 192007 CCA

Area Forecast Discussion...CORRECTED
National Weather Service Marquette MI
307 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 night through Thursday)
Issued at 302 PM EST THU JAN 19 2017

January thaw with well above normal temperatures continues into
early next week. Mid to late next week as strong jet stream crossing
northern Pacific attm pushes across the Conus, deep upper level
troughing will become established across much of the Conus. Temps
will only return toward normal as this colder air moves back over
much of the Conus. Lift with shortwaves over the central Conus this
weekend into early next week along with persistent low-level lift
ahead of sfc troughing from the central Plains to the Ohio Valley
will result in off and on rain chances this weekend into Mon and
depending on low-level temp profile, there could be freezing
precip issues as well. Colder air with the increasing troughing
brings snow back into the picture beginning late Monday night or
into Tue. Models have been hinting at more well developed
shortwave and associated low pressure system lifting across Great
Lakes Tue into Wed on leading edge of the troughing and colder
air, but they still do not agree in how strong this system will be
and the exact track of sfc low.

On Fri night, shortwave currently bringing showers to western
portion of Ohio Valley will be in process of lifting across northern
Upper Michigan and Lk Superior as shown by h7-h5 q-vector
convergence and moist isentropic ascent 295-285k (925-700mb). Expect
batch of light rain across mainly northern Upper Michigan in the
evening. Ptype should stay liquid as blyr temps will be middle to
upper 30s. Once rain ends temps could try to drop toward freezing
which may lead to slippery spots developing overnight. There could
also be some fog or drizzle, especially in areas of central Upper
Michigan where SE winds will lead to upslope lifting. Another
shortwave coming out of the trough over the western Conus lifts
across Upper Michigan on Sat. Also should be another round of low-
level isentropic lift as sfc low pressure wave lifts toward the
Upper Mississippi river valley while weakening. Will have to watch
out for possible freezing rain/drizzle Sat morning as warm temps
aloft flow over sfc-1kft layer that could be just blo freezing.
Similar to Friday the freezing precip hazard will diminish as blyr
temps warm into the mid-upper 30s on Sat aftn. Could be slippery on
untreated roads in the morning though.

Yet another shortwave moves across Upper Great Lakes on Sun though
much stronger shorwtwave/sfc low should be more over southern Plains
to the Tennessee river valley. More low-level lift along sfc trough
extending to the northwest of the southern Plains system and high
pressure over eastern Canada will support some light rain or at the
least increase the drizzle potential. Blyr temps on Sun should be
high enough to decrease freezing precip potential, though with even
slight cooling on Sun night could see that hazard return to inland
areas of central and east. On Mon as the system over the southeast
Conus heads to the east coast, expect sfc trough to persist across
the Great Lakes before it meets up with secondary sfc low over the
northern Plains. This low-level lifting mechanism along with another
shortwave lifting northward over the middle Conus and stronger jet
energy crossing middle Conus should help light rain expand over
Upper Great Lakes. Freezing precip could be factor on Mon morning
before temps warm by aftn into the mid to upper 30s.

All through the weekend and into Mon, ongoing light liquid precip,
melting snowpack and sfc dwpnts rising above freezing should result
in areas of fog, especially over the higher terrain of the central
cwa and the Keweenaw with steady ESE-SE wind direction. Fog could be
dense at times.

As shortwave slides across Upper Great Lakes into Tue, expect
cooling aloft to allow for rain/snow mix later Mon night with better
chance of snow on Tue as heights aloft fall and overall column
cools. Whether there is stronger system to bring accumulating snow
to much of region later Tue into Wed is not clear yet. Current runs
all show stronger system across middle Conus on leading edge of
larger scale troughing developing. But, as would be expected this
far out in time, there remains disagreement on track of low. ECMWF
favors track from northern Ill toward Lk Erie while Canadian is more
suppressed and GFS is more wrapped up and farther northwest. Even if
this system does not bring widespread snow to Upper Michigan, it
will still help switch the mild weather pattern back to one that is
breezy and cooler by this time next week. Colder conditions with
readings possible back or even blo normal could come back in by the
weekend of Jan 27-29.


.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

.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.

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


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