Area Forecast Discussion
Issued by NWS Marquette, MI

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179
FXUS63 KMQT 261131
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
731 AM EDT Sat May 26 2018

.SHORT TERM...(Today and tonight)
Issued at 353 AM EDT SAT MAY 26 2018

Early this morning, lingering thunderstorms across far eastern Upper
Michigan continued to slowly drift eastward as the main axis of
moisture transport continued to advect into Lower Michigan and
southern Ontario. Behind this main moisture axis, skies began to
clear across the west half of Upper Michigan. The combination of a
moist, humid airmass and light winds associated with an advancing
surface trough allowed for areas of patchy fog this morning. The
main forecast concerns today are: patchy fog early this morning
across the west half of Upper Michigan, another warm and humid day
with temperatures soaring 20 to 30 degrees above normal for this
time of year, and yet another chance for stronger thunderstorms.
Anyone who has outdoor activities planned later today and this
evening should keep a close eye on the weather.

Through the morning hours, patchy fog is expected across the west
half of the area. It is possible that this fog could become locally
dense in low-laying areas where the "cooler" air has drained
overnight. Once the sun starts to rise, any areas that see this
patchy fog should expect visibilities to briefing worsen, but as
insolation continues to increase and begins to foster mixing
visibilities will improve. As the day progresses, deep mixing is
progged to develop favoring efficient mixing of warmer air aloft down
the surface. Temperatures will easily climb into the mid to upper
80s, with even a few locations climbing into the lower 90s across
the interior west. Further east, flow off of the Great Lakes should
limit the amount of mixing, so temperatures are only expected to
climb into the mid to upper 70s inland from the Great Lakes. Along
the shoreline of Lake Michigan, onshore flow will keep temperatures
much cooler compared to inland.

As for thunderstorm activity, as the main shortwave moving across
the Arrowhead of Minnesota this morning continues to dig south
across Upper Michigan later this morning and afternoon, chances for
thunderstorms will increases. As insolation increases, even though
mixing should favor slightly lower dew points than yesterday,
steepening lapse rates aloft will help make up for the slightly
reduced low-level moisture to favor SBCAPE values averaging around
1500-2000 J/kg inland from the Great Lakes. With the main shortwave
digs across the region, the deep layer shear will be slightly better
today compared to yesterday with 0-6km shear approaching 30 to 35
knots. Therefore, it is possible that storms could remain more
organized today. With ample instability and better shear today, hail
should be more of a threat today with any convection that can remain
isolated. Otherwise, strong downburst winds will also be possible
given the very steep low-level lapse rates expected to develop. The
main area of concern for stronger storms is across the interior west
and central where lake breezes off of Lake Superior and Michigan
will enhance low-level convergence along the above mentioned surface
trough. Across the far east, afternoon thunderstorms are possible
where the Lake Superior and Michigan breezes converge, but with the
shear expected to be weaker these storms will likely be more pulsey.

Tonight as we lose insolation, convection should start to weaken.
With the main trough axis tracking across the central and east half
of the area, cannot rule out a few lingering showers and
thunderstorms during the overnight hours. As high pressure briefly
settles in behind the exiting surface trough, light winds will favor
the possibility of patchy fog developing - especially over areas
that see heavier rain today.

.LONG TERM...(Sunday through Friday)
Issued at 458 AM EDT SAT MAY 26 2018

Models suggest that a slowly progressive pattern will prevail
through the middle of next week as a mid/upper level trough over the
wrn CONUS advances into the nrn plains and the downstream ridge over
the plains shifts through the Great Lakes. Above normal temperatures
will persist through most of the period but should moderate with
cooler drier conditions toward the end of the week as high pressure
builds into the area from nrn Ontario.

Sunday, weak high pressure is expected to build into the northern
Great Lakes bringing dry but warm weather. Inland high temps will
again climb into the mid to upper 80s. Light winds will allow
prominent lake breezes to bring cooling along the Great Lakes.

Sunday night into Monday, With a prominent theta-e ridge through the
upper MS valley, MUCAPE values into the 1000-1500 J/Kg range, and
weak shrtwvs likely moving into the region, models suggest that an
MCS or area of shra/tsra may develop or strengthen over nrn MN and
slide into Upper Michigan late Sunday night into Mon morning.
Effective shear should be strong enough to support storm
organization with potential for some marginally severe hail.
However, confidence is low with the timing/location/strength of any
storms. Additional tsra may redevelop with daytime heating along
leftover outflow or lake breeze boundaries.

Tuesday, additional shra/tsra will be possible with the unstable
airmass over the region and the potential for additional shrtwvs
moving near the top of the mid/upper level ridge.

Wednesday-Friday, the mid level trough moving out of the nrn plains
should bring lower heights into the northern Great Lakes with
increasing shra/tsra chances especially during peak heating. As the
mid level trough shifts to the east, refreshingly cooler and drier
air will move in on ne winds as high pressure builds into the area
from nrn Ontario.
&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 731 AM EDT SAT MAY 26 2018

The main aviation concern today is the potential for thunderstorms
and their impacts. Confidence was not high enough to include
prevailing mentions for thunder at KIWD/KCMX today, so if these
trends change expect amendments or subsequent TAFs to add mentions.
Further east, confidence was high enough that KSAW will see
afternoon thunderstorms to include prevailing mentions. If stronger
storms do impact terminals, reduced visibilities due to heavy rain
will be possible, along with gusty, erratic winds and hail. Storms
will gradually diminish after sunset, but tonight we could see the
potential for fog over areas that see heavy rain as winds become
light and skies clear out. At KSAW, if the marine layer comes
onshore and pushing inland further than currently expected,
visibilities and ceilings could be sharply reduced.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 353 AM EDT SAT MAY 26 2018

This morning, surface troughing has begun to push south across the
Lake. Along the leading edge of this trough, expect a brief increase
in winds to upwards of 20 to 30 knots. Otherwise, winds are expected
to remain less than 20 knots today, and through the middle of next
week. Expect areas of fog to develop and linger at times into the
weekend as multiple rounds of rain are expected over the lake and
the humid airmass lingers. Fog may be dense at times. Thunderstorms
are possible this afternoon into sat night, and then again early
next week.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 2 PM EDT this afternoon for LSZ243>245-
     263-264.

Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...JLB
AVIATION...Ritzman
MARINE...Ritzman



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