093
FXUS63 KMQT 200516
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
116 AM EDT Sat Jul 20 2024

.KEY MESSAGES...

- 30-60% chance of showers and thunderstorms mainly over the
southern half in the afternoon/evening Saturday. Severe weather not
expected.

- Next chance of showers/storms Tuesday/Wednesday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 1253 PM EDT Fri Jul 19 2024

Early afternoon water vapor shows an anomalously strong cutoff low
over northeastern Hudson Bay, with ridging over the Desert Southwest
northward into the Canadian Rockies. Midlevel height field is rather
baggy over the Great Lakes; however, there is an MCV noted over far
SW Ontario, and a zonally elongated vort max moving southward across
central Ontario. Surface pattern is similarly nondescript over the
local area with weak zonal flow. Fair weather cumulus are dotting
the skies with quiet and seasonable weather expected for the rest of
the day.

Tonight, the zonal vort max will shift southeast as the parent low
moves east into northern Quebec. Surface high will expand a bit
southward in the wake of this activity, with the net result being a
weakening low-level front crossing Lake Superior from the north.
Maybe just enough forcing and moisture for isolated showers/t-storms
over the lake late, possibly reaching the tip of the Keweenaw prior
to 12Z Sat. Otherwise, a quiet and seasonable night expected.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 247 PM EDT Fri Jul 19 2024

Low-level frontal boundary discussed in the short term section will
continue progressing south through the UP on Saturday while losing
upper level support as the parent low continues shifting eastward
into Quebec. This may result in a few showers in the northern half
during the morning and early afternoon, but should be no more than a
nuisance if anything. Relatively more widespread coverage of showers
and thunderstorms expected over the southern half (highest near the
WI/MI border counties) where the arrival of the front will coincide
with a modestly destabilizing diurnal boundary layer. SBCAPE progged
by the HREF mean mainly in the 500-1000 J/kg range, but
midlevel lapse rates are weak and winds through the column are
very light, so any storms should be of the garden variety. There
could be a few heavier downpours with likely slow moving storms
and a narrow ribbon of 1.5-1.75" PWATs, but overall low impacts
expected. Saturday night into Sunday, big bubble no trouble as
the Ontario high continues to expand over Lake Superior and the
UP. Highs both days fairly seasonable, a little cooler near the
big lake due to onshore flow.

Another tranquil day Monday under the influence of the high, but
weak warm advection should boost temps a couple degrees to the
seasonably warm side. Western NOAM ridging remains strong into next
week, while shortwave energy dives south along its eastern flank.
Deterministic guidance is showing some of this energy consolidating
and possibly cutting off in the vicinity of the upper Great Lakes.
This will bring our next chance at showers and thunderstorms in the
Tuesday/Wednesday frame, along with cooling temps by Wednesday.
Temps look to rebound with a drying trend for the end of next week
as this low moves out. In fact, some summer warmth could return
Friday into next weekend as there are indications that some of the
western US ridging folds eastward into the upper Great Lakes.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 115 AM EDT Sat Jul 20 2024

VFR conditions will continue through the TAF period. The only
forecast concerns are a northerly wind shift with an approaching
cold front set to cross the UP in the daytime hours (12-18z) and
some incoming cloud cover, though, not expecting any drop to MVFR or
lower. Some spotty showers are possible along the boundary, however,
more convective activity is possible in the southwest UP
(potentially at IWD) along the MI/WI border as the cold front
interacts with max diurnal destabilization. Confidence in shower or
afternoon thunderstorm coverage is low, but I did include a VCSH at
SAW Sat afternoon where shower coverage will probably be the best of
all the TAF sites.

&&

.MARINE...
Issued at 517 PM EDT Fri Jul 19 2024

Southwest winds up to 20 knots over mainly the west half of Lake
Superior will diminish below 20 knots tonight as a cold front
moves through overnight into early Saturday. There is a slight
(20%) chance for storms developing along this boundary to make
it across the lake later tonight, but confidence is low. Winds
stay light, mainly below 20 kts at least through Monday. Winds
increase out of the NE across the western portions of the lake
Tuesday with another shortwave trough moving through. Gusts
around 20kts are possible. This is also our next decent window
for showers/storms to move over the lake (20- 30% chance) before
mainly dry weather returns midweek onward.

&&

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

&&

$$

SHORT TERM...Thompson
LONG TERM...Thompson
AVIATION...Voss
MARINE...Voss