914
FXUS63 KMQT 151716
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
116 PM EDT Mon Jul 15 2024

.KEY MESSAGES...

- Marginal risk (category 1 out of 5) of severe thunderstorms today
mainly from 4-10 pm EDT. Main threat is damaging winds and large
hail.

- Cooler and drier for midweek with the arrival of high pressure.

&&

.SHORT TERM /THROUGH TODAY/...
Issued at 1254 PM EDT Mon Jul 15 2024

Early afternoon water vapor imagery shows a midlevel anticyclone
centered around the Four Corners and a cutoff low just southwest of
Hudson Bay. Stronger 500 mb flow between these features is spreading
eastward into the Upper Great Lakes, with a notable shortwave trough
now progressing into northern MN. High convective debris clouds are
spreading into the local area ahead of this feature and also along
the northern periphery of a decaying MCS over southern MN/WI, but
there is some clearing noted over northern WI where some lower cu is
developing. Gradual moistening is taking place over the western UP
where dewpoints are creeping back up into the low to mid-60s.
Surface pattern is a bit messy, but there is a cold front apparent
from roughly Thunder Bay SWWD to about Fergus Falls, MN.

Modest destabilization ahead of the incoming wave/cold front should
continue over roughly the SW half of the UP this afternoon due to
clearing skies and weak advection of better low-level moisture.
Despite midlevel lapse rates decreasing to less than 7 C/km, this
should allow for the development of 1000-1500 J/kg MLCAPE just ahead
of the incoming disturbances. Further north toward the Keweenaw,
Marquette area and points east, destabilization is less certain with
MLCAPE likely remaining less than 1000 J/kg. Deep-layer shear does
look good, increasing to 40-45 kt. Low-level winds are a bit more
modest and may actually decrease a bit ahead of the front, leaving
low-level convergence a question-mark. Still, high confidence in a
rather quick-moving area of showers and thunderstorms moving across
the UP from west to east this afternoon, primarily 4-10 pm EDT.
Marginal risk (category 1/5) for severe weather with a few storms
capable of damaging winds and large hail. Risk appears highest south
of a line from roughly Manistique to Ontonagon.

Cold and dry advection ensues tonight, ushering out the seasonably
warm airmass of the last couple days. Skies clearing with lows in
the mid-50s to near 60.

&&

.LONG TERM /TONIGHT THROUGH SUNDAY/...
Issued at 427 AM EDT Mon Jul 15 2024

Starting Monday evening, storms are expected to be ongoing over
central Upper MI ahead of the cold front to the west. As the front
and shortwave push east out of the area, storms exit our CWA by
around midnight. Some of these storms could still be strong to
severe given the bulk shear of ~35-40 kts, lightly capped MUCAPE of
500-1500 J/kg, and 1km helicity ~100 m2/s2. Otherwise the UP returns
quiet as lows settle into the mid 50s to low 60s.

Tuesday and Wednesday, the positively tilted mid level trough over
northern Ontario becomes more vertically oriented as it pivots over
the UP before swinging east toward Quebec and New England for
Thursday. This results in a period of northwest flow, supporting
some light northwest winds gusting up to 20 mph and cooler temps. A
shortwave rotates over the UP on Tuesday ahead of the trough,
yielding slight chances for light showers in the afternoon. With the
main trough pivoting overhead on Wednesday, cloud cover and chances
for showers increase again. That said, a drier airmass will be
advecting in from the northwest, evident in the PWATs dropping to
around 0.7-0.9". Thus, this round will also bring very low impact
accumulations if any. Also with a couple hundred J/kg of MUCAPE, no
severe weather is expected. Highs on Tuesday stay mainly in the 70s
while Wednesday cools off even more with highs only in the mid 60s
to low 70s. Lows Tuesday and Wednesday night dip into the 40s in the
interior with 50s near the lakeshores.

High pressure then builds in from the west Wednesday, continuing to
shift east-southeast over the Great Lakes through the rest of the
week into next weekend. This results in a gradual warming pattern
late next week into the weekend with dry weather likely through the
first half of the weekend. Also during this period, the mid level
ridge over the west amplifies, resulting in troughing over northern
Ontario/Quebec. That leads to the next precip coming from a
shortwave trough dropping south across the Upper Great Lakes late
next weekend, although confidence on timing is low given the spread
in deterministic solutions at this time. From there, ensemble
guidance indicates that the fairly drier pattern is expected to
persist with another sfc high pressure building in from northwestern
Canada as the amplified ridge eventually gives way and shifts
eastward across the CONUS. This means that outside any additional
shortwaves, precip will be largely driven by diurnal heating or lake
breeze convergence moving into next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 116 PM EDT Mon Jul 15 2024

Main aviation concern is convective potential this afternoon and
evening. TEMPO included 20-22Z for IWD and 22-24Z at SAW for TS. Any
storm could produce brief downpours reducing vsby to MVFR/IFR as
well as gusty winds and hail. TS probability lower at CMX so it was
not included; however, one cannot be ruled out roughly 21-23Z. VFR
conditions should exist outside of these storms, although there is
some potential for MVFR clouds/fog in their wake for at least a few
hours overnight. Potential too low to include at SAW/CMX at this
time.

&&

.MARINE...
Issued at 427 AM EDT Mon Jul 15 2024

Winds remain light and somewhat variable through this morning as
weak sfc ridging moves over the lake and the next round of storms
approaches from the west. Storms are expected to move over the west
end of the lake this afternoon, continuing east across the lake into
the evening hours. Some of these storms will be capable of producing
gusty winds, frequent lightning, and isolated large hail. Patchy
dense fog is possible, especially in the wake of precipitation.
Winds turn west to northwest behind the cold front Monday evening
into Monday night. Winds are generally expected to remain below 20
kts through the remainder of the forecast period as high pressure
builds in from the west on Wednesday, continuing east-southeast over
the Great Lakes Basin through the rest of the week and into the
weekend. However, the strongest winds up to 20 kts are most likely
on Tuesday and Wednesday.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Dense Fog Advisory until 5 PM EDT this afternoon for LSZ250-
     251-267.

Lake Michigan...
None.

&&

$$

SHORT TERM...Thompson
LONG TERM...Jablonski
AVIATION...Thompson
MARINE...Jablonski