330
FXUS63 KAPX 121737
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
137 PM EDT Wed Jun 12 2024

.KEY MESSAGES...

- Increasing showers/storms tonight

- Chances for marginal severe storms Thursday

- Heat builds in this weekend and early next week

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 235 AM EDT Wed Jun 12 2024

Pattern Synopsis/Pattern Forecast:

Weak (and weakening) shortwave trough in the process of working east
across the area early this morning...becoming increasingly detached
from rapidly decaying cold front working into the western Great
Lakes. Just enough forcing/mid level moisture convergence to kick
off a few sprinkles and light showers across the Northwoods...
although those continue to decay as forcing and convergence do the
same. Definitely a much milder night, with current readings mostly
in the 50s.

Shortwave and attendant disjointed moisture plume will work east of
the area early on this morning, with remnant weak surface trough
following in their wake. Next shortwave trough will sharpen some as
it races east/southeast...reaching vicinity southwest Ontario and
the northern Mississippi Valley region by sunrise Thursday.
North/south oriented cold front will work out ahead of this wave,
expected to reach western upper Michigan down into central Wisconsin
by Thursday morning. Organizing pre-frontal moisture plume will
spread across our area tonight, bringing the next threat for showers
and thunderstorms along with it.

Primary Forecast Concerns/Challenges:

Cloud/temperature trends and addressing shower and thunderstorm
potential tonight.

Details:

Any lingering showers/sprinkles expected to come to an end early on
this morning, leaving behind partly to mostly sunny skies. Airmass
continues to modify, and when combined with that sunshine...will
support high temperatures this afternoon reaching into the lower 80s
across much of northern lower Michigan...with readings just a touch
cooler right near those big waters and across eastern upper
Michigan. Will likely see some afternoon cumulus develop,
particularly across northeast lower Michigan where convergence will
be maximized. Not out of the realm of possibility for a stray shower
or two to develop out of this cu field, but probabilities are simply
too low to include in the forecast at this time. Deep layer moisture
advection ramps up tonight out ahead of that approaching wave.
Expect upscale growth to showers and thunderstorms off to our
northwest later this afternoon and evening, with favorable mass
convergence along veering of 40+ knot low level jet helping drive at
least some of that activity into the region tonight. Not overly
confident on how organized and widespread showers will remain as
they depart much more impressive instability plume to our west.
Still, axis of elevated instability (several hundred joules/kg cape)
and forced convergence along the leading edge of that low level jet
definitely supports at least some maintenance of showers and
thunderstorms. Despite increasing wind fields through the vertical,
surface based instability is lost...negating any real severe weather
concerns. Suppose a more organized updraft through that elevated
instability plume would support some brief gusty winds, but any
severe threat most definitely appears minimal at this time. Even
milder tonight, with lows likely not even dropping out of the 60s
for most areas south of the big bridge.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 235 AM EDT Wed Jun 12 2024

Pattern Synopsis and Forecast: A weak surface feature will be moving
over northern MI Thursday morning around sunrise. Mostly stratiform
rain with a few spots of embedded thunder and more moderate rain
showers will be generally exiting to the east. Southwest winds will
prevail and will strengthen as we head into midday. Moisture from
the recent rain and continual moisture advection will allow surface
dewpoints to reach into the mid 60s over much of the area Thursday
afternoon. An upper level short wave will track to clip the Great
Lakes region, trending upper heights down while surface temperatuers
warm. This leads to good chances for around 1000 - possibly 2000
j/kg SBCAPE (00Z HRRR and NAM most agressive) Thursday afternoon.
Better mid level shear exists (mostly speed and less directional)
which will help storms get organized. This (and a few other details
discussed below) will lead to good chances for a severe environment
Thursday afternoon and evening. A cold front will be approaching
from the north, possibly moving through the CWA late
afternoon/evening to even early Thursday night. At this time, CAMs
depict more discrete convection forming along the boundary as it
moves through the CWA. Model sounding profiles depict better chances
for hail and wind threats with storms, as we lack stronger lower
level shear.

Northwest winds and upper level heights starting to rise Friday.
Temperatures will dip around 10 degrees with the cooler and drier
Canadian air settling in. Upper level ridging building over the
easter CONUS coast will keep the warming trend in place through the
end of the period. Moisture will eventually be advected northward,
rising heat indices even more for early next week and introducing
more rain chances.


Primary Forecast Concerns/Key Messages: Short range CAM guidance has
been trending up for available instability Thursday. The mean HREF
SBCAPE for Thursday afternoon is around 900 j/kg. 00Z Sounding
traces from the HRRR  depict a healthy part of that instability
within the HGZ, even with drier mid level air. CAMs more
consistently show an elongated hodograph trace, indicating weaker
low level shear but enough mid level shear to organize storms. LCL
heights will generally be around 2 - 3.5 kft, and combined with
weaker low level shear will be less favorable for tornadic activity.
The more likely threats will be hail and wind with storms that do
form. Now do form is the key there, as there is uncertainty in the
timing of the cold front. Some guidance moves it through eastern
upper more in the afternoon hours, and some guidance shows it
slightly later (especially previous runs). If there is ample
afternoon sunshine after the morning rain moves out Thursday,
isolated to scattered storm formation won`t need the boundary and
will likely fire off somewhere over northern lower (convective T is
around 83 degrees, which northern lower will likely reach in the mid
afternoon hours). The front will likely aid in storm initiation over
eastern upper sometime Thursday afternoon, and these storms have
chances for producing severe hail and/or winds. Enough instability
(elevated at least) should stick around for the frontal passage once
it reaches northern lower, meaning storm chances will continue
through Thursday evening and maybe night (depending on the frontal
timing).

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 129 PM EDT Wed Jun 12 2024

Upper wave and associated cold front will approach the Great
Lakes tonight, with mid level clouds increasing along with the
threat for showers/storms. Areas of MVFR cigs possible after
midnight into early Thursday before drier air moves in with
clearing skies. LLWS developing at KMBL, KTVC and KPLN later
tonight as winds ramp up aloft from the southwest. Surface winds
becoming gustier late tonight into the day on Thursday.
Additional showers/storms possible on Thursday, especially
during the afternoon.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

SHORT TERM...MSB
LONG TERM...ELD
AVIATION...MSB/JK