976
FXUS63 KAPX 120210
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1010 PM EDT Thu Jul 11 2024

.KEY MESSAGES...

- Elevated showers and thunderstorms possible overnight...with
  additional convection expected Friday mainly northeast Lower.

- Multiple chances for thunderstorms, mainly Saturday night
  through early next week.

&&

.UPDATE...
Issued at 1010 PM EDT Thu Jul 11 2024

Synopsis: Water vapor imagery shows a well defined mid-upper level
short wave trough centered right over the upper Great Lakes this
evening...with its upward motion field right over northern Michigan.
There is a weaker vorticity center tracking northeast across
southwest Lower with a more substantial PV anomaly over western Lake
Michigan.  No real surface reflection of this with a broad area of
high pressure (1019mb) also centered over Michigan.  Northwest-
southeast moisture gradient across the state with better absolute
moisture across Lower Michigan (precipitable water less than 0.50
inch across Lake Superior/western Upper).  Scattered convection
bubbled up during the afternoon...initially along the eastern Upper
lake breeze collision zone...then along the US-131 corridor.
Convection continues to develop roughly along the northern Lower I-
75 corridor where low level moisture convergence has been maximized
for several hours now along the eastern instability gradient (around
400-700J/kg MLCAPE)...and focused along several boundary collisions.
Eastern Upper convection has largely dissipated with skies clearing
over northern Lower "horseshoeing" around the area of convection/
overcast over central portions of the state.

Short wave trough/cold pool with meander across Michigan through
Friday...pushing into the lower Lakes/southeast Ontario Friday
night.  Surface pressure gradient remains weak so another day of
lake breeze development on tap for Friday.

Forecast Update: Of interest for the overnight will be what becomes
of second PV anomaly that will be moving across Lower Michigan
overnight and into the day Friday.  Good case of differential
advection with colder dynamic tropopause temperatures advecting over
a low level theta-e ridge in place...resulting in 400-800J/kg MUCAPE
with not a lot of inhibition forecast.  Current forecast has this
basic idea in mind but will re-orient the PoPs into more of a north-
south axis roughly from US-131 to M-33 in northern Lower.  Will also
extend this idea into Friday morning...though with most of the PoP
focus over northeast Lower.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 302 PM EDT Thu Jul 11 2024

Col region still in the vicinity...as PV swirly spins over northern
IL. High clouds from said swirly advecting northward into northwest
Lower...as additional PV dives across SW WI. Diurnal heating and
lingering low-level moisture helping generate afternoon cu...and
lake breeze development very obvious per visible satellite with the
lake shadows quite present amid weak winds/flow through the column.
Temps already pushing or breaking 80 inland...with dewpoints in the
60s...and finally starting to see our first few showers/storms pop
up on the radar in the last hour...particularly along lake breeze
axes -- one near Cadillac, the other at the convergence of the
Straits breezes near Pellston. Expecting this trend...increasing pop-
up showers and storms...to continue through the remainder of the
afternoon into this evening with PV maxima slowly meandering
northward. Weak flow continues tonight...as col region/trough axis
itself slips overhead through morning. Anticipate some fog
development...but also concerned about continuation of
showers/storms even during the early morning hours Friday, along
with additional pop-ups in the afternoon again. Highs today and
Friday up into the lower 80s, with seasonably warm lows tonight
around 60 (give or take a few degrees).

Primary Forecast Concerns:

Afternoon showers/storms today...500-1000j/kg mixed layer CAPE this
afternoon as surface heating helps break weak capping aloft to
generate aforementioned showers/storms. As mentioned in the morning
update...not expecting anything necessarily severe with the
convection this afternoon, given weak wind profiles through the bulk
of the column that are not terribly supportive of organization or
downward momentum transfer. However...do think that the slow moving,
pulsey nature of these storms could support some brief, gusty
downburst potential with precip loading...and perhaps some small
hail. Think one of the greater threats with the convection this
afternoon is heavy downpours, given that the warm cloud layer is
still deeper than 3km and pwats are still hanging around an inch
ahead of this weak niblet. Pretty similar to things like yesterday;
if storms persist over an area for a while, could see some localized
flooding going into this evening as storm motion could become
slower/more nebulous with outflow boundaries converging with lake
breeze boundaries, particularly as additional storms pop up this
afternoon. For now, though...expecting just a general summertime
thunderstorm situation.

Not entirely sure all the activity will totally fade after dark
tonight...as core of coldest air aloft slips overhead and weakens
stability. Think we should hold onto some decent MUCape through the
night into early Friday morning...as PVA begins to increase with the
approach of the next niblet...and do carry some low/slight-chance
wording in the forecast for now regarding precip chances starting as
early as 9-12z. Worst case scenario...we could start popping
convection as early as 12-15z Friday, and wouldn`t be surprised if
some of it tried to be a little stronger, given the weaker stability
aloft...though aside from that niblet passing through from SW-NE in
the morning, and perhaps lake breeze boundaries developing in the
afternoon...not a ton of forcing present Friday. Background flow
should become a little more south/westerly for Friday, which could
focus the better chances for convergence closer to the Sunrise Side
again.

Otherwise...do think we`ll have to watch for patchy fog again
tonight into Friday morning, perhaps not all that dissimilar from
last night/this morning. Think the greatest focus of this will be
over NW Lower into the interior higher terrain again...where low-
level moisture is most prevalent attm (and should be aided by this
afternoon/evening`s convection)...though may be possible elsewhere
convection occurs through this evening, too.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
Issued at 302 PM EDT Thu Jul 11 2024

Pattern Synopsis:

Troughing over the Great Lakes will begin to lift into eastern
Canada Friday night as shortwave ridging temporarily works overhead
on Saturday. Subsidence aloft provided by this feature will help
build surface high pressure across the region through the first half
of the weekend. A shortwave/jet max looks to punch into the northern
Great Lakes with progressive flow/additional shortwaves potentially
working overhead for much of next week.

Forecast Details:

Multiple chances for thunderstorms -- Mainly quiet weather is
expected across the area on Saturday as aforementioned high pressure
builds in. While less than 15% PoPs are in the forecast, the chance
for an isolated shower/storm cannot be entirely ruled out. The
primary chances for thunderstorms return Saturday night into Sunday
morning. Strong buoyancy will be in place to our northwest across
the upper Midwest and south-central Canada, where storms are
expected to initiate on Saturday. While there is high uncertainty in
timing and eventual track of these thunderstorms, there is the
potential for a strong line of storms to move into the Great Lakes
in the Saturday night/Sunday morning timeframe. Further details in
regards to confidence/timing/location of any expected storms will
become more clear in future forecast cycles.

Northern Michigan`s best chances for thunderstorms will likely be
later Sunday through Monday with strong buoyancy on the order of
2,000-3,000 MLCAPE in place. This will be plenty to support the
chances for strong storms, especially with the potential for
multiple shortwaves to work across the region and provide support
aloft for any storms that initiate. While not specifically outlined
in severe categorical outlooks by SPC at this time, the potential
for severe thunderstorms cannot be ruled out Sunday and Monday.
Still being several days out, very low confidence exists in any
details regarding timing/specific locations. However, with no major
frontal boundary passages during that time, buoyancy will likely
remain in place -- bringing the potential for multiple rounds of
storms, even overnight Sunday into Monday. Otherwise, temperatures
look to warm well into the 80s this weekend into early next week. As
the previous forecaster noted, the high temperature forecasts on
Sunday and Monday will be highly dependent on thunderstorm
development and associated rain-cooled air/cloud cover potentially
leading to cooler-than-anticipated afternoon highs where
thunderstorms track. After a front moves through in the late
Monday/Tuesday timeframe, quieter weather looks to be on the horizon
with cooler temperatures in the 70s through the middle of next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 712 PM EDT Thu Jul 11 2024

So far into the early evening pop-up convection has mostly
evaded the terminals with a decrease in coverage over the past
hour. Still monitoring along the I-75 corridor where low level
moisture convergence has been maximized though that area is
along the eastern edge of the instability gradient. Concerns for
the overnight revolve around fog potential...not a great signal
for that with probabilities for MVFR visibilities generally 20
percent or less. There are exceptions to every rule and suspect
KMBL may go LIFR overnight but fog should mix out quickly
Friday morning. Other concern is passing short wave trough and
lingering elevated instability along low level theta-e ridge
into northeast Lower beneath cooling temperatures aloft.
Potential is there for some morning convection across most of
northern Lower...maybe even some "sunrise surprise" development.
But appears that KAPN would stand the best chance of seeing any
impacts from that probably starting mid morning.

&&

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

&&

$$

UPDATE...JPB
SHORT TERM...FEF
LONG TERM...DJC
AVIATION...JPB