Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 160851
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
451 AM EDT Sat Sep 16 2017

.SHORT TERM...(Today and tonight)
Issued at 450 AM EDT SAT SEP 16 2017

Water vapor imagery shows the main trough axis associated with the
developing surface low across the Upper Mississippi Valley
continuing to gradually lift across the central and northern Plains
this morning. Ahead of this trough, broad warm air advection has
allowed a fairly narrow band of showers and thunderstorms to develop
across central and eastern portions of the area this morning.
Overnight lows have remained very mild as a stalled out, stationary
front remains anchored across northern portions of Upper Michigan.
Today`s forecast highlights include a high swim risk for Lake
Michigan beaches along the shores of southern Schoolcraft County,
another unseasonably warm day with increasing humidity, and then the
arrival of additional showers and thunderstorms later this
afternoon/evening across the west, a few of which could be strong to
severe.

In response to the above mentioned wave lifting into the Upper
Mississippi Valley, the stationary front will become reinforced
across far northern portions of the area as a secondary area of low
pressure develops across western Wisconsin. This elongated surface
trough/cold front will be the primary focus for convective
initiation later this afternoon across western Lake Superior and
Upper Michigan. It looks like a few storms could be strong to
severe, especially closer to the Wisconsin border where the nose of
1500-2000 J/kg of MUCAPE is progged to develop as mid-level lapse
rates steepen and moisture transport increases. The deep-layer shear
is also progged to increase to around 30 to 40 knots later this
afternoon and evening as jet streak energy lifts northeast across
the Upper Mississippi Valley. With the deep-layer shear vectors
oriented fairly perpendicular to the surface trough, wouldn`t be
surprised if a few stronger updrafts develop and remain better
organized. The main hazards from stronger storms will be hail and
strong downdraft winds. Otherwise, expect the unseasonably warm
temperatures to linger, with many locations likely climbing into the
low to upper 80s once again today. The humidity will be on the
increase, so it may feel rather uncomfortable at times outside.
Breezy south winds may offer some relief, but these breezy winds
will create a high swim risk for the Lake Michigan beaches along the
shoreline of southern Schoolcraft County. Therefore, a beach hazard
statement has been issued as dangerous currents are expected to
develop.

Tonight, ongoing convection across the west is expected to lift
northeast across Lake Superior, and central and eastern portions of
Upper Michigan as the surface trough/cold front continues it`s
eastward track. Storms should weaken in intensity through the
overnight hours, but with lingering elevated instability expect
thunder to remain prevalent. Temperature wise, we`re looking at
another mild night across much of the area and these temperatures
will be highly dependent on the arrival of the cold front. Across
the west, temperatures should drop into the mid 50s as the front is
expected to move through during the overnight hours. Further to the
east where the front will be slow to arrive, expect low temperatures
to only drop into the 60s.

.LONG TERM...(Saturday night through Friday)
Issued at 348 PM EDT FRI SEP 15 2017

Guidance continues to hold onto the dominant upper level ridge
across the eastern CONUS through the weekend; however, there
continues to be some nudging to the east which could bring the
upstream trough further east towards the Upper Peninsula. Will
continue to bring steady increases of precip and possibly thunder.
With a low pressure system lifting north of the forecast area Sun,
guidance indicates a frontal boundary will precede a surface ridge
of high pressure late in the weekend into early next week. This will
then allow dry weather to return.

The pattern does start to become more active with a quasi-zonal
orientation from Tue-Thur of next week. This will bring periodic
chances for showers and possibly thunder, but also with more
seasonal temps.
&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 125 AM EDT SAT SEP 16 2017

LLWS at all sites overnight and at KSAW Saturday evening. Expect
showers to generally hold off to the west through much of the
period.

At KCMX, LIFR to VLIFR conditions in CIGS and fog are expected
into early overnight with eastern flow off the lake and plenty of
upstream low level moisture. Conditions should improve by early
Saturday morning to VFR as winds shift to a downslope southeast
direction.

At KSAW, a narrow band of showers will impact the terminal early
this morning, otherwise moist southeast upslope flow could lead to
some patchy fog/stratus overnight but uncertainty is such that kept
VFR conditions thru the period.

At KIWD, moist northeast flow off Lake Superior will lead to LIFR
stratus clouds into early overnight but once winds shift southeast
early Saturday morning expect improvement to VFR.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 450 AM EDT SAT SEP 16 2017

Winds of 20 to 30 knots are expected this morning, but they will
weaken to around or less than 20 knots through the day today. By
Sunday morning, expect the winds to pick back up to around 20 to 30
knots as a cold front pushes east across the lake. Winds will relax
to around or less than 15 knots by early Monday morning through
Tuesday. By Wednesday winds will increase to 20 to 25 knots briefly,
and then will be around 20 knots through the end of next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement from 8 AM EDT this morning through this
     evening for MIZ014.

Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...Beachler
AVIATION...Voss/Ritzman
MARINE...Ritzman



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