Area Forecast Discussion
Issued by NWS Marquette, MI
FXUS63 KMQT 250754
Area Forecast Discussion
National Weather Service Marquette MI
354 AM EDT Tue Oct 25 2016
.SHORT TERM...(This evening through Tuesday)
Issued at 404 PM EDT MON OCT 24 2016
WV imagery and RAP analysis indicated nw mid/upper level flow
through the nrn Great Lakes between a trough from ern Canada into
New England and a ridge from the srn plains into Saskatchewan. At
the surface, a ridge extended from Manitoba into the Upper MS valley
resulting in anticyclonic nw flow into Upper Michigan. Although 850
mb temps around -6C (water temps near 11C) provided enough
instability for isolated lake effect rain showers over the east,
with daytime warming and an influx of drier air, the pcpn has
diminished this afternoon.
Tonight: As high pressure continued to build into the region,
veering winds to the nne and 850 mb temps remaining near -6C will
push the lake effect westward toward n cntrl Upper Michigan.
Inversion heights near 4k-5k ft and continue acyc flow will limit
intensity. Wet-bulb zero heights suggest pcpn will remain mainly as
rain. Otherwise, mostly clear skies inland west will allow temps to
fall into the upper 20s. Temperatures in the lower 30s are expected
over the rest of the cwa.
Tuesday: Confluent mid upper level flow, high pressure building over
the region with low level dry air, and inversion heights lower to
near 3k ft will bring an end to the lake effect pcpn by afternoon.
However, the 925-850 mb thermal trough will remain close enough to
support extensive stratocu development keeping highs in the mid 40s
north and upper 40s south.
.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 06Z TAFS through 06Z Tuesday night)
Issued at 140 AM EDT TUE OCT 25 2016
Lake clouds will move back into SAW overnight as winds shift from NW
to N-NE over Lake Superior and cause conditions to drop to high
MVFR/low VFR there. VFR conditions are expected elsewhere.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 406 PM 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 into this
evening. High pressure will then build across the area overnight
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.