Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 202336

Area Forecast Discussion
National Weather Service Marquette MI
736 PM EDT Thu Oct 20 2016

.SHORT TERM...(This evening through Friday)
Issued at 330 PM EDT THU OCT 20 2016

With a low over James Bay, cold air continues to push into the area
this afternoon. Currently, 850mb temps are below 0C over the entire
CWA and as low as -5C over the northwestern half of the CWA. The
axis of the associated upper trough currently extends from the upper
low to NW MN. The axis will drop through the area tonight into Fri
morning, bringing 850mb temps as low as -6C and N winds behind the
SFC trough. This will increase lake effect showers, especially over
the higher terrain of the north-central, tonight into Fri morning.
Some of the showers over the higher terrain of the interior W should
turn to snow overnight into the early morning, with only trace
accumulations possible. Showers will diminish gradually through the
day Fri.

.LONG TERM...(Friday night through Thursday)
Issued at 415 PM EDT THU OCT 20 2016

A benign stretch of weather for late Oct standards is shaping up
during the long term. At the start of the weekend, mid/upper level
trofs will be located just off the W Coast and along the E Coast
with ridging over the central CONUS. Heading thru the middle of next
week, the eastern trof will lift out to the ne/weaken, and the trof
just off the W Coast will also weaken with core of the negative
height anomalies drifting sw. In response, the central CONUS ridge
will also weaken, leaving low amplitude flow and slightly above
normal 500mb heights across the northern CONUS/southern Canada by
mid week. As for pcpn, after lingering lake effect ends Fri evening,
some -shra will be possible Sun as a shortwave drops into the
eastern trof. Brief shot of colder air following this wave will then
generate a little lake effect pcpn into Mon. Dry weather should
follow into Tue, and then there is some agreement, though with
timing/strength issues, for a shortwave and -shra to reach the area
in the low amplitude flow mid week. As for temps, current cool
weather/blo normal temps will trend to above normal for Sun, then
back to slightly blo normal on Mon. As low amplitude flow takes over
into mid week, temps will trend back to around to slightly above
normal. Farther down the line, CPC, NAEFS and CFSv2 outlooks
continue to favor above normal temps overall into the beginning of
Nov. The signal for warmth in early Nov is actually quite strong.
Even farther out, CFSv2 runs have been persistently indicating that
the above normal temp pattern that has dominated autumn so far
should prevail farther out thru the month of Nov as a whole. These
outlooks don`t preclude some periods of blo normal temps, but
suggest that any cold periods will be short lived.

Beginning Fri night/Sat...although sfc high pres shifting over
central Upper MI will end lake effect pcpn over the w and central,
maintained chc pops thru the evening over the e with a continued
cyclonic nnw flow and 850mb temps near -5C. Meanwhile, to the w,
850mb trof moving across MN to far western Lake Superior combined
with waa will support thickening high then mid clouds spreading over
western Upper MI. Given the isentropic ascent indicated, not totally
out of the question that a few -shra/sprinkles could end up
developing over nw Upper MI late in the night into Sat morning.
Potential is low enough at this point that a mention of pcpn in fcst
is not warranted. With the 850mb trof/waa weakening while shifting
e, will maintain a dry fcst on Sat though there will probably be
quite a bit of cloud cover. Min temps Fri night will be lowest over
the central under sfc high pres ridge axis and least cloud cover.
Temps in the interior could drop to as low as the lwr 20s at
traditional cold spots.

Heading thru Sun/Mon, guidance is in good agreement, showing a
shortwave passing across the Upper Great Lakes on its way into the
eastern trof. GFS and especially CMC are stronger with the shortwave
and show more of a sfc reflection than the ECMWF. These difference
translate to timing with the ECMWF quickest and CMC slowest. Will
lean fcst toward the middle ground GFS which has also shown good
continuity over the last few runs. Modest deep layer forcing and a
decent frontogenesis signature should generate some shra as wave
passes Sun, mainly during the aftn. With 850mb temps falling to
-4 to -5C behind shortwave, isold/sct lake effect -shra should
develop Sun night off eastern Lake Superior. Slightly lwr sfc water
temps over western Lake Superior with 850mb temps a couple of
degrees higher should mostly prevent any pcpn off the lake over the
w. Lake effect pcpn will linger over the e thru at least Mon morning
before sfc high pres ridge arrives and air mass begins to moderate

As mentioned above, medium range models show some agreement for a
shortwave to move across the western Great Lakes midweek. There are
also indications that a weaker lead shortwave and associated waa
could spread -shra into the area as early as Tue. With confidence
low on this feature, will focus better chc of pcpn into mainly the
Wed/Wed night period in association with the stronger shortwave.

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 733 PM EDT THU OCT 20 2016

Cold air moving through the area will generate lake effect clouds
and pcpn with variable CIGs and isolated showers. CIGs will lower
late tonight into Fri as a trough moves through the area, leading to
increased lake effect. Dry air will only slowly move in later Friday
with a returned to sct clouds and VFR conditions.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 330 PM EDT THU OCT 20 2016

No significant low pressure systems are expected to move through the
Upper Great Lakes in the next several days. Winds will remain well
below gales through the period.

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


LONG TERM...Rolfson
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