Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 220854
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
454 AM EDT Sat Jul 22 2017

.SHORT TERM...(Today and tonight)
Issued at 454 AM EDT SAT JUL 22 2017

Water vapor imagery this morning shows a couple lead shortwaves
pushing across the northern Plains, with a more potent shortwave
beginning to dig south across southern Saskatchewan and Manitoba.
From the northern Plains down and across the Corn Belt, we`re seeing
another active morning with numerous complexes of thunderstorms
riding along the upper-level ridging parked across the central and
southern Plains.

The main forecast concern is the chance for strong to severe storms
across the west and central portions of Upper Michigan. The above
mentioned complex of storms rolling across the northern Plains has
remained active this morning as additional updrafts have developed
along the southern edge of this complex where outflow continues to
generate new updrafts. With around 1000-1500 J/kg of MUCAPE and 2-
6km lapse rates of 7.5-8.0 C/km, expect this convection to hold
together through the rest of the morning. With mid-level flow
becoming a bit more zonal ahead of the more potent shortwave, this
line of storms has begun to move more easterly, which provides a
more favorable track for clipping southwest portions of the area
later this morning/early afternoon. Models are generally not in good
agreement with the speed of this initial wave of convection, but
with the convection already moving into western Minnesota this
morning, the late morning to early afternoon hours seem reasonable.
With this first round of storms, a few could be strong wind gusty
winds and small hail. As the afternoon progresses and early morning
convection will diminish as it tracks across central portions of the
area, with another round of storms possible later in the afternoon
as an inverted surface trough moves across the area. Thinking that
the GFS is overdoing the amount of instability progged to develop
this afternoon, but at least 2000-2500 J/kg of MUCAPE should
develop, and with 0-6 km bulk shear increasing to 40 to 50 knots,
expect convection to remain organized. With the bulk shear oriented
perpendicular to the surface trough, it is not out of the question
that a supercell or two will be possible if storms can remain
isolated. Western and central portions of Upper Michigan will have
the best chance at seeing any of these strong to severe storms later
this afternoon and evening. Hail and damaging winds look to be the
primary hazards with the stronger convection. There may be a small
tornado threat if convection interacts with any residual boundaries
and/or lake breezes. Tonight, as the main upper-level wave tracks
across the area, expect showers and thunderstorms to become more
widespread as convection moves eastward across Upper Michigan.

.LONG TERM...(Sunday through Friday)
Issued at 356 AM EDT SAT JUL 22 2017

Generally a pretty quiet stretch of weather in the long term. Strong
shortwave trough still will be over the Upper Great Lakes on Sunday.
This wave along with inverted sfc trough will support showers and
some thunderstorms mostly over the east half into early Sun aftn.
Sun will also be cooler (all but the far scntrl) with low clouds
and given the moist cyclonic upslope flow behind the departing low
there may also be drizzle in the higher terrain of the west and
north central. Low clouds and some drizzle likely will persist
well into Sun night before high pressure/drier air lead to improving
conditions through Mon morning.

The high pressure will result in quiet weather Mon into most of Tue.
Next shortwave in NW flow aloft will move through on Tue night.
Could be scattered showers and a few thunderstorms late Tue aftn
into Tue night. Appears forcing outruns greater instability which
pokes into southern U.P. Tue evening. Mismatch of these two factors
probably reduces the chances of seeing any severe storms. Once the
trough moves through, high pressure resumes dry weather for the rest
of the week.

Temperatures will generally be at or slightly above normal but we
should not be dealing with more persistent summertime humidity.
Coolest temps will be on Mon in wake of the low pressure system that
moves through this weekend. Warmest days of the week, with readings
possibly well into the 80s in parts of forecast area, will be Tue
and Wed. The humidity this weekend will be replaced by less humid
conditions on Mon with the high drifting overhead. Humidity will
increase again Tue/Wed as the sfc trough moves through. Less humid
conditions then return later this week.
&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 123 AM EDT SAT JUL 22 2017

With rainfall that has occurred around KIWD, expect VFR conditions
to fall to MVFR by daybreak. Not out of the question that conditions
could fall to IFR. MVFR conditions should then continue into early
aftn. At KCMX and KSAW, VFR conditions should prevail thru the
morning hrs, but will need to watch for stratus to develop northward
toward KSAW. There could be some shra and isold thunder overnight
thru the morning, but confidence in any of the terminals being
impacted is low. Better potential of shra/tstms will arrive this
aftn/evening as a vigorous disturbance approaches. MVFR or even
brief IFR conditions may occur with any of the shra or tstms.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 440 AM EDT SAT JUL 22 2017

East to northeast winds gusting to 25 kts today, strongest over
western Lk Superior, as low pressure system and cold front slide
toward Great Lakes from the northern Plains. East to southeast winds
will remain gusty tonight mainly over eastern Lk Superior toward
Whitefish Bay. Sfc low slides over central Great Lakes on Sunday
while cold front drops south across Lk Superior. Expect east winds
to shift north to northeast 20 to 25 kts on Sun aftn behind the
front. Winds will gradually diminish Sun night into Mon as high
pressure builds across the region. Low pressure trough moving in
late Tue may lead to southwest winds increasing to 25 kts late Tue
into Tue night. Otherwise, winds this week should be 20 kts or less.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...JLA
AVIATION...Rolfson
MARINE...JLA



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