Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251736

Area Forecast Discussion
National Weather Service Marquette MI
136 PM EDT Tue Oct 25 2016

.SHORT TERM...(Today and tonight)
Issued at 427 AM EDT TUE OCT 25 2016

Confluent northwest flow aloft is leading to large sfc ridge
expanding from Hudson Bay across the western Great Lakes. Low level
flow is chilly with h85 temps around -6c flowing across eastern Lk
Superior. Lk Superior sfc temps are 10-13c so there delta t/s 16-19c
are plenty to support at least isold lake effect rain/snow showers
even with the ridge/anticyclonic low-level flow. IR satellite and
radar indicates most lake effect is occurring over north central and
eastern cwa. Kind of a tricky setup concerning ptype. Wbzero heights
1500-2000 ft indicate rain is main pytpe, but partial clearing has
allowed near sfc temps at or even blo freezing in parts of central
cwa. MDOT site near Gwinn indicated thin film on roadway and other
obs with temps near freezing indicate there is potential for
slippery spots on untreated roads for interior eastern Marquette and
western Alger and perhaps northern Delta too. Thankfully coverage
of lake effect is isold at best for these areas early this morning.

Expect the lake effect to shift farther west across Marquette county
this morning, maybe more after daybreak, as sfc-h925 winds veer more
northerly. The flow will result in expansion of stratocu clouds
across western and central Upper Michigan. Light lake effect should
diminish/end late morning into the early aftn, with the upslope flow
keeping it going longest over higher terrain of ncntrl cwa. Temps
mainly in the 40s with more clouds compared to Mon aftn. Also not as
breezy as Mon with strongest winds up to 20 mph over east cwa
near Lk Superior this morning.

Attn tonight will be on shortwave trough emerging out of mean
troughing over far western conus this morning. Shortwave and deep
layer q-vector convergence/lift makes its way toward Upper
Mississippi river valley late tonight. System will be pushing into
the large low-level ridge so dry air will need to be overcome and
probably will restrict precip pushing into southern Upper Michigan.
Kept pops very low and do not have them in until late tonight. Temps
could be chilly early on in mid-upr 20s inland central and east then
begin to rise some as mid-high clouds thicken ahead of the system.
Even so, if there is precip over west cwa, soundings indicate that
ptype would be rain as wbzero heights are well above 1kft. Thus took
out any mention of snow for tonight.

.LONG TERM...(Wednesday through Monday)
Issued at 353 AM EDT TUE OCT 25 2016

Beginning Wed into Thu...Majority of models slower bringing pcpn
into Upper Mi with next shortwave fcst to move through the Central
Plains and mid-Mississippi Valley. The slower arrival of pcpn will
likely be due to the shortwave moving into downstream mid-upper
ridging over the Mississippi Valley and surface ridging holding
strong from Ontario/Quebec into the Upper Great Lakes. 00Z NAM is
the only outlier model bringing pcpn across much of west and central
Upper Mi by Wed afternoon while the rest of the models show only
light pcpn reaching into the Wi border counties and south central
U.P. by late Wed morning into afternoon. Given model tendencies and
amount of dry air in place from ridging would tend to side with
slower/farther south solution per model consensus and generally
disregard NAM. This would likely mean little if any snow Wed since
pcpn timing would be later in the morning when diurnal warming would
turn pcpn over to rain. Also model consensus would argue for drier
fcst overall Wed into Thu for the northern portion of Upper Mi as
farther south track of shortwave and associated sfc low would keep
best forcing/moisture transport well south of area. Expect highs
both Wed into Thu to be in the 40s.

The trough axis will then push east as mid-upper ridging and mostly
dry conditions briefly return to the Upper Great Lakes. The drying
will be short-lived as models indicate a Pacific NW system lifting
through the Canadian Rockies and arriving into the Upper
Midwest/Great Lakes region late Fri/early Sat. Warm advection ahead
of this system will spread an area of rain through the region late
Fri into Fri night with higher (likely) pops over the east half
where isentropic ascent will be maximized. After some lingering
showers on Sat with exiting Pacific system, expect mostly dry
conditions on Sunday as ridging moves back in from the west. In
between the mid-week system and weekend system, high temps could
rebound into the lower 50s on Fri before turning cooler into the 45
to 50 range for the weekend.

Monday looks potentially wetter again as the next Pacific shortwave
and associated frontal boundary approaches from the Northern Plains.

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 135 PM EDT TUE OCT 25 2016

VFR to sometimes MVFR celings and isolated showers are expected with
lake effect clouds at KSAW into early evening. Otherwise, VFR
conditions are expected at all sites overnight into Wednesday
morning before MVFR ceilings arrive late Wednesday morning and


.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 427 AM EDT TUE OCT 25 2016

No gale force winds are expected through the period. ESE-E winds may
reach 25-30 kts late tonight into Wed, strongest tonight over
western sections then over north central and eastern sections on
Wed. 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. NW winds
may reach 30 knots behind the system Fri night into Sat as well.

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


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