Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240907

Area Forecast Discussion
National Weather Service Marquette MI
507 AM EDT Mon Oct 24 2016

.SHORT TERM...(Today and tonight)
Issued at 505 AM EDT MON OCT 24 2016

Latest 07z water vapor imagery showed a weak shortwave passing over
the Upper Great Lakes. This shortwave and weak q-vector convergence
associated with it supported some moderate lake effect rain showers
over eastern Marquette County a couple of hours ago. Now it looks
like forcing has weakened and these rain showers have since
dissipated with the main area of showers generally shifting east
into Alger and Northern Schoolcraft counties per radar imagery.

Today and Tonight: With 850mb temperatures of -5C to -6C range still
forecast to move across the far eastern portion of Lake Superior in
a nw flow and lake delta-t values 16-17C, would expect lake effect
clouds and some light and scattered lake effect rain showers to
continue into Alger, Luce and northern Schoolcraft counties today.
The Keweenaw Peninsula will likely see lake clouds persisting, but
the cooler 850mb temperatures for lake effect rain showers will
remain over the east. Another feature inhibiting shower potential
over the west will be subsidence associated with a surface/upper
level ridge sliding into the area through the day today. Increased
subsidence may result in breaks in cloud cover especially over the
far west. Expect highs today from the lower 40s north to the upper
40s/around 50F south central.

As the sfc-h85 ridge axis begins to shift even farther east into the
west half of Upper Mi tonight, winds will begin to veer more
northerly and even north-northeast overnight tonight allowing
lingering isolated lake effect bands to shift from the far eastern
counties into Marquette-Alger and even Baraga counties late tonight
into Tue morning. Falling temps tonight will allow snow to mix in
with rain showers, especially over higher terrain areas away from
Lake Superior. Expect min temps tonight to range from the mid to
upper 20s over the west and central interior to the upper 30s to
around 40F along Lake Superior in onshore northerly flow.

.LONG TERM...(Tuesday through Sunday)
Issued at 358 AM EDT MON OCT 24 2016

Mean upper level troughing remains in place into this weekend.
Daytime temperatures should stay at or slightly blo normal mainly in
the 40s while nighttime temperatures in the upper 20s to upper 30s
are pretty typical for this time of year. Confluent northwest flow
on Tue will result in high pressure ridge building across Great
Lakes. Could see light lake effect hang on early in the day over
north central cwa as blyr winds veer northerly as the ridge builds
in. Probably will see good deal of cloud cover persist even after
lake effect ends as higher rh remains in the 925-850mb layer beneath
a subsidence inversion. Clouds should eventually try to clear out
later in the day with mixing, though there are indications at least
scattered clouds could linger into Tue evening.

Attn later Tue night into Wed will be on shortwave trough sliding
across the Central Plains. Sfc-h85 low tied to the wave should be
crossing vcnty of IA to southern MN by 12z Wed. Deep layer q-vector
forcing and lift within right entrance region of of jet streak from
northern Ontario to mid Atlantic will support rain moving in through
the day on Wed. Despite temps in the 30s on Tue night, soundings
look too warm in the lowest levels /wbzero heights aoa 1000 ft agl/
to support any snow as precip moves in so have took out any mention
in the wx grids. As long as circulation in low-levels remains south
of Upper Michigan, suspect heavier rain will remain there as well
closer to where better moisture influx 925-700mb is located and on
northern edge of elevated instability. Even if precip stays light,
likely pops still appear on track for Wed into Wed night. Lack of
phasing btwn lead system moving through Wed and additional shortwave
dropping across in northwest flow late Wed night into Thu continues
to lead to lower potential for much in way of accumulating snow late
Wed night into Thu, but there will be enough low-level cooling in
wake of the sfc low to keep a mix of rain/snow especiallly for the
interior as has been in forecast for a while now.

Well for at least this model cycle, there is okay agreement among
the GFS, ECMWF and GEM for Fri-Sun. Model consistency during this
time frame has been low so we`ll see if the agreement continues in
the coming days. For now though, another shortwave working through
in the nw flow will keep troughing across the region into the
weekend. Best chance for precip would be on Fri-Fri night as
associated sfc low crosses the Upper Great Lakes while deepening.
Exact track of the low still a bigger question though. If the
pressure pattern holds up as forecast, then would be chilly and
windy on Sat behind this system. High pressure/dry low-levels
building in quickly would limit lake effect precip on Sat though
probably cannot rule it out. Weaker system(s) that would produce
light precip as deep moisture is lacking crosss the region on Sun
and maybe Mon as well.

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 128 AM EDT MON OCT 24 2016

Clouds will linger into Mon morning bringing MVFR to VFR ceilings
across the area. Drier air moves in Mon afternoon and should
decrease the cloud cover.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 505 AM EDT MON OCT 24 2016

Winds will remain below gales through the period. A tightening
gradient between a deep low pressure system moving through Quebec
and a high pressure ridge building into the Plains will lead to NW
winds gusting to 30 knots over eastern Lake Superior today. High
pressure will then build across the area tonight into Tuesday,
keeping winds generally light across Lake Superior. Southeast winds
will increase again to 20 to 30 knots Wednesday into Wednesday
evening as a low pressure system passing just south of the area.
There will be a trough passage on Thursday but winds should still
remain fairly light. Friday will see south winds increase to 20 to
30 knots again over the east half of Lake Superior as another low
pressure system approaches from the Northern Plains.

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


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