163
FXUS63 KMQT 131637
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
1237 PM EDT Sat Jul 13 2024

.KEY MESSAGES...

- Seasonably warm this afternoon with a 20-30% chance of
  showers/thunderstorms over the west.

- 40-60% chance of showers and thunderstorms this evening into
  overnight hours. Marginal risk (category 1 out of 5) of severe
  thunderstorms for most of the UP. Slight risk (category 2 out
  of 5) for the far west. Main threats are large hail and
  damaging winds.

- Staying warm with additional thunderstorm potential
  Sunday/Monday.

- Cooling and drying trend into the midweek portion of next
  week with the arrival of high pressure.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 1235 PM EDT Sat Jul 13 2024

Upper air consists of an anticyclone centered around the Four
Corners and a cutoff low over northern SK/MB. Belt of seasonably
fast zonal flow between these two features is diffluent over the
local area. Several small areas of convection are noted in this
diffluent zone - one in far SW ON, one in northern MN, and one in
northern WI. These are being fed by modest SW winds at 850 mb and
are located in an area of steep midlevel lapse rates. These lapse
rates weaken with eastward extent, and as a result, there is
uncertainty whether the lead convective cluster over northern WI
will make it into the western UP this afternoon. This cluster has
outperformed CAM depictions of it so far, leading to greater than
normal uncertainty in its evolution. Have expanded 20-40% PoPs over
the far west for mid-afternoon to account for this. Severe risk
appears low given paltry bulk shear if storms do indeed unfold this
afternoon. Otherwise, a few showers are firing up along the lake
breeze in northeast Alger/northern Luce County. Isolated ts possible
here this afternoon.

Similar low predictability exists in the overnight hours with any
MCS activity due to wide variance in CAM output and tendency for
better instability to be located SW of the local area. As a result,
early afternoon forecast update went with a more broad-brush
approach to PoPs in the 50-60% range for the overnight hours. Severe
risk (large hail/damaging winds) does still exist mainly for the
western half of the UP if an outflow-dominant MCS does develop given
respectable convective parameters (1000-2500 J/kg MUCAPE), although
deep shear is a bit lacking at less than 30 kt.

Otherwise, the other concern is the heat with temps on track to
reach the mid-80s to near 90 (warmest in downslope zones near Lake
Superior), although dewpoints should mix out a bit in the warmest
areas with humidity contribution to apparent temps negligible.

&&

.LONG TERM /TONIGHT THROUGH FRIDAY/...
Issued at 531 AM EDT Sat Jul 13 2024

The extended forecast starts off active with two systems late this
weekend and early next week as shortwaves ride the zonal flow aloft.
Meanwhile, low level southwesterly flow will support WAA and
moisture advection, priming the atmosphere for strong to possibly
severe storms. High pressure then returns mid next week, resulting
in a drier and quieter weather period.

Any lingering convection Sunday morning moves out leaving a mainly
dry start to the day. Given the elevated dew points nearing 70 in
the east and warm temps in the 80s (possibly some low 90s south
central), instability returns; the 7/13 0Z HREF mean MUCAPE builds
up to 1000-2000 J/kg. The shear profile will be supportive of any
thunderstorms that do develop with around 30 kts of bulk shear.
Forcing looks to be primarily driven by any lake breeze convergence,
which leaves low confidence in thunderstorms again. The UP then
returns dry Sunday night with lows in the upper 50s to mid 60s,
cooler in the interior.

Monday into Monday night brings another round of showers and
thunderstorms as another shortwave tracks across the region and an
associated sfc low follows east over Lake Superior/northern Ontario.
Bulk shear sees a significant increase from previous convection with
up to 1000 J/kg of MUCAPE, so some strong to severe storms are
possible ahead of the cold front.

Although a mid level closed low will be shifting east through
northern Ontario and Quebec Tuesday and Wednesday, sending a
shortwave over the area during that period, dry weather returns as
high pressure begins building in from the northwest. How long this
dry period will last will depend on when the next shortwave
progresses southeast through the Upper Great Lakes as the mid level
ridge over the western CONUS slowly shifts east. Slight chances hold
off until late next weekend. Otherwise, a cooler period is expected
accompanying the high pressure and northwest flow.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 745 AM EDT Sat Jul 13 2024

VFR conditions will hold steady through the TAF period despite the
threat for showers and thunderstorms later today and into tonight.
For now, confidence is only high enough to carry VCTS mention at IWD
tonight, but thunder could be added to SAW with future TAF
updates/issuances. In addition, there will be a LLWS threat at SAW
tonight with an uptick in a low level jet.

&&

.MARINE...
Issued at 547 AM EDT Sat Jul 13 2024

Southerly winds remain below 20 kts today as the pressure gradient
stays light. South winds increase tonight over the east to around 20
kts with a 15-30% chance for gusts reaching 25 kts tonight ahead of
the next disturbance. Some strong to severe storms are possible
tonight, especially across western Lake Superior. The main threats
are damaging winds, but large hail is also possible. Another round
of storms is expected Monday into Monday night as a low pressure
system moves through the area. Patchy dense fog is also a
possibility in the wake of any precipitation. Following the
Monday/Monday night low presusure`s cold front, west winds increase
to around 20 kts across much of the lake Monday night and Tuesday.
As high pressure begins to build in mid next week, winds look to
fall back below 20 kts, remaining light through the remainder of the
forecast period.

&&

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

&&

$$

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