Area Forecast Discussion
Issued by NWS Marquette, MI

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KMQT 302227

Area Forecast Discussion
National Weather Service Marquette MI
627 PM EDT Fri Oct 30 2020

.SHORT TERM...(This evening through Saturday)
Issued at 404 PM EDT FRI OCT 30 2020

Lingering clouds continue to hang around on the eastern half of the
CWA early this afternoon. For those that were watching satellite
earlier today, a small scale mesolow developed near the Keweenaw
Peninsula before eventually dissipating by late morning. Clouds
should continue to push east as the late afternoon progresses into
the evening hours. Additionally, the building upper level ridge will
propagate over the northern Great Lakes region. This will allow for
subsidence to take hold for the short term period and keep overnight
skies clear, allowing for a quick radiational cooling period. This
will be shortlived as the warmer air is advected aloft over the area
making the overnight lows a bit tricky due to the coolest
temperatures happening potentially closer to the midnight hour
before warming a few degrees by 12Z. A strong 987mb surface low
north of the Canadian border will evolve and continue to propagate
eastward from the northwest of the CWA. Deepening pressure gradients
will enhance winds speeds over the southern portions of the CWA
first. Some of the hi-res models are showing light rain showers
developing between 12-18Z for areas spreading from the Manistique to
Grand Marais region before the main portion of the developing wave
brings a larger swath of precipitation for Saturday afternoon onward
that will start off as rain, eventually changing over to a lake
effect snow regime once the temperatures behind the associated cold
front decrease quickly.

.LONG TERM...(Saturday night through Friday)
Issued at 352 PM EDT FRI OCT 30 2020

Main story of the long term will be the strong shortwave that will
be moving across the Upper Great Lakes Saturday night into Sunday
with the warm front already passed through the area and waiting on
the trailing cold front and secondary cold front Sunday morning that
will usher in strong CAA towards the CWA. Winds will shift from the
south to the northwest behind both fronts which will aid in rushing
in that much colder air over a generally warm lake (lake sfc temps
are about 5-7C), 850mb temperatures will fall to between -10C to -
13C by Sunday afternoon. With this and the combination of strong
fgen and tightening pressure gradient, there will be a period of
heavy lake-effect snow over the northwest wind belts. But wait
there`s more! Strong mixing with quick change in pressure gradient
and isallobaric lift will create gusty winds Sunday morning into the
afternoon where enough mixing coming down to the sfc could create
some wind gusts of 50+ mph along the Lake Superior Shoreline and the
over the Keweenaw Peninsula. Overall, it is going to be an miserable
day with wind, rain, and snow. In terms of snowfall totals, models
haven`t been really consistent with amounts but given a baseline
estimate, I`d expect somewhere between 2-6 inches over the west half
and roughly 2-3 inches over the east half. This is all dependent on
how long the WAA holds over the area and how fast this low moves
through the CWA. If the low moves faster than forecasted, then long
fetch over the lake won`t last long but if low slows a bit, that
could enhance totals over the higher terrain areas. We`ll continue
to watch what latest guidance suggest. Given we are still more than
36 hours out, will hold on WSW and wind headlines for now.

In terms of lakeshore impacts, waves will still be high, about 5-8
ft, along Lake Michigan Saturday night with south-southwest gales
diminishing by early Sunday morning which minor lakeshore flooding
and beach erosion is a good possibility through early Sunday
morning. Sunday along the Lake Superior shoreline is another good
bet of Lakeshore Flooding and beach erosion, especially western
shoreline and areas east of Marquette. Again, lakeshore headlines
will be needed but holding off for now for Lake Superior. This
weekend will be a good idea to stay away from the Great Lakes
Lakeshores as impacts are certain.

Behind this system, winds and precipitation will wind down by Sunday
Evening into Monday morning. A couple of models are trying to hint
at a weak shortwave passing just to the north of Lake Superior
Monday which may bring a light rain/snow mix over the east Monday.
Latest guidance shows any precip that is associated with the
shortwave will miss the CWA off to the northeast. Took out any PoPs
that were in there. Then ridging will begin to take hold of most of
the northern CONUS starting Tuesday as 500mb heights will rise,
helping to bring in warmer air towards upper Michigan. This pattern
will likely hold through the end of next week.

In terms of temperatures, Sunday will be well below average with
upper 20s to mid 30s. Then the warmup will slowly start Monday with
mostly 40s and then 50s likely Tuesday through Thursday as the ridge
takes firm control. Sorry to the snow lovers as most of the extended
will be above average temperatures which will melt a good amount of
snow that is left on the ground.

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 627 PM EDT FRI OCT 30 2020

VFR conditions will continue at all sites until late Sat afternoon
when lower MVFR cigs move in. Will get gusty on Sat at all sites.
IWD will see some LLWS in the morning before gusting in the

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 404 PM EDT FRI OCT 30 2020

Wind speeds generally below 20 knots can be expected through
Saturday morning, and then attention will turn to Saturday afternoon
into Sunday. Confidence is high, regarding the potential for high-
end gales Saturday afternoon into Sunday. Southerly winds start to
increase on Saturday with winds to 40 knots over the east and 30
knots, which a few gusts to gale, over the west. The strongest winds
will come behind the cold front early Sunday morning into the
afternoon. Winds behind the front will shift NNW and reach 40 to 45
knots over the west half. Over the east storm force gusts of 50 to
55 knots will be possible. Confidence remains high with regards to
this high end gale to storm force event and have continued to
maintain the gale and storm watches. Winds will diminish to 20 to 30
knots and still couldn`t rule out a few gusts to gale on Monday.

Upper Michigan...
  Lakeshore Flood Advisory from noon EDT Saturday to 1 AM EST
     Sunday for MIZ013.

  Lakeshore Flood Warning from noon EDT Saturday to 3 AM EST
     Sunday for MIZ014.

Lake Superior...
  Gale Watch from late Saturday night through Sunday morning for

  Storm Watch from Sunday morning through Sunday afternoon for

  Gale Warning from 8 AM to 9 PM EDT Saturday for LSZ249>251-266-

  Gale Watch from Saturday evening through Sunday afternoon for

  Gale Watch from Saturday evening through Sunday morning for

  Gale Warning from 10 AM to 5 PM EDT Saturday for LSZ244-245-248-

Lake Michigan...
  Gale Warning from 11 AM EDT Saturday to 1 AM EST Monday for



MARINE...- None - is the U.S. government's official web portal to all federal, state and local government web resources and services.