727
FXUS63 KAPX 291756
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
156 PM EDT Sat Jun 29 2024

.KEY MESSAGES...

- A few severe storms possible this afternoon/evening.
  Winds/hail primary hazards.

- Cooler/drier Sunday and chilly Monday morning.

- More unsettled weather starting Tuesday with potential for
  another round of heavy rainfall.

- Drying out for the Fourth of July?

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 353 AM EDT Sat Jun 29 2024

Pattern/synopsis: 500mb mean troffing evolves eastward toward
the northern Great Lakes. Two primary shortwaves are responsible
for this; one rotates thru this morning, the 2nd toward evening.
At the surface, 1001mb low pressure over Lk Superior will move
eastward. A warm front crosses from w to e early today, with a
cold front following from the nw late today.

Showers continue to cross the region early this morning,
especially in eastern upper and ne lower MI. There hasn`t been
much lightning with this activity, though in the past hour a few
CGs have been seen from Atlanta to Alpena. Warm/moist advection
continues, and additional destabilization is occurring aloft.
MuCape values of 100-200j/kg are present, but closer to 500j/kg
or more over WI and northern IL. CAMs generally favor an
additional round of showers with some embedded t-storms to
develop toward 7-8am, from MBL and Leelanau Co up into eastern
upper MI. The low level jet does weaken with time, so this round
of convection will push gradually eastward, with coverage
decreasing with time. By noon, sct showers and perhaps a t-storm
will linger over ne lower and far eastern upper MI, with nw
lower drying out seeing some partial sunshine break out
(especially by early afternoon). Morning convection is not
expected to be strong or severe, due to limited instability.

However, the emerging partial sunshine will allow for
destabilization to occur ahead of the cold front. By late
afternoon, MlCape values will be near 1k j/kg, with 0-6km bulk
shear of 40-50kt. This is a reasonable spot for some storm
organization (though this is over land; instability will be
lower over the big lakes). Surface winds will be veered to west,
even ahead of the cold front, which will significantly limit
convergence along the boundary. Those winds will be too strong
for pure lake breezes, but onshore turning and localized
convergence will still develop in some areas. Initial stronger
convection could form in central upper MI by mid afternoon, and
gradually grow upscale and expand se-ward. These storms will
bring a severe wind and (perhaps) hail threat, across all of
northern MI.

Instability falls off behind the cold front, though there`s
sufficient moisture for a few showers to linger. By late
tonight, there might even be a touch of drizzle over eastern
upper and northern lower MI.

Max temps today from low-mid 70s north, to mid 80s far se. Lows
tonight upper 40s to mid 50s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 353 AM EDT Sat Jun 29 2024

Pattern Forecast:

Weekend ends/new week starts with long wave troughing over eastern
Canada extending into New England/Mid Atlantic/Great Lakes Sunday...
with rising heights/short wave ridging into the Midwest and Great
Lakes for Monday.  Ridge axis forecast to slide into the lower Lakes
Tuesday as the next Pacific-origin short wave trough crosses the
Rockies and into the Plains.  This should set up a baroclinic zone
across the Great Lakes by midweek...and the potential for unsettled
weather heading into the Fourth of July holiday.

Unseasonably strong high pressure (~1028mb/+2 to +3 sigma
standardized MSLP anomaly) builds into the Plains/Midwest for
Sunday...providing Michigan with cooler northwest boundary layer
flow while a secondary short wave trough pivots southeast across the
state. Surface high will be over the upper Lakes by Monday
morning...then shifts east Tuesday allowing for a return of warmer
air (along with a northward moisture surge).  Height falls are then
expected to push a cold front into the region Wednesday...will have
to see how far south it gets before becoming parallel to more zonal
flow setting up across the Great Lakes Thursday.

Primary Forecast Concerns:

Cooler/drier Sunday and chilly Monday morning: A nice cool shot on
the way for Sunday in the wake of today`s cold front passage...
probably cold enough (below 8C at 925mb) to allow lake convection
to augment early cloud cover.  Clouds should eventually mix into a
high Sc deck and thin out in the afternoon.  High temperatures
should be in the 60s...possibly around 70 near Saginaw Bay due to
downsloping flow...but a solid 10-15 degrees below normal for the
last weekend of June.  Should be breezy as well given cold air
advection and a decent pressure gradient with upstream surface
high...gusts of 15 to 25 mph expected (and likely Small Craft
Advisories within most nearshore zones).  Should be good radiational
cooling conditions for most areas Sunday night as winds drop off
under clear skies...and with temperatures only starting in the 60s
suspect some of the colder low lying spots could dip into the upper
30s overnight.  Used a combination of the NBM 10th percentile and
statistical guidance to adjust low temperatures Monday morning.

More unsettled weather starting Tuesday with potential for another
round of heavy rainfall:  The return of warmer air may be
accompanied by an impressive surge of deep layer moisture from the
Gulf.  This could set the stage for potentially more heavy rainfall
Tuesday night into Wednesday.  Current probabilities only hint at it
for northern Lower and are more focused on Wisconsin (as well as the
Day 5 Excessive Rainfall Outlook). But an idea to monitor heading
into midweek.

Drying out for the Fourth of July?: As of now looks promising...rain
chances may not be too far to the south but for now see no
compelling reason not to be optimistic about it.  Temperatures
should at least be seasonable (normal highs in the upper 70s-lower
80s)...doesn`t look brutally warm at this point.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 153 PM EDT Sat Jun 29 2024

MVFR to IFR CIGs will continue to erode this afternoon, if only
for a short while. Think a good chunk of the area/TAF sites has
the chance to see VCTS, generally from about 20/22Z to 00/02Z.
Showers may linger thereafter into the early overnight.
Generally expecting MVFR, perhaps iso IFR CIGs to become
possible once again this evening and into the overnight hrs. Any
stronger storms may produce gusty winds and hail.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 11 PM this evening to 8 PM EDT
     Sunday for LHZ347>349.
     Small Craft Advisory from 8 PM this evening to noon EDT Sunday
     for LMZ323-341-342-344>346.
     Small Craft Advisory from 8 PM this evening to 8 PM EDT Sunday
     for LSZ321.

&&

$$

SHORT TERM...JZ
LONG TERM...JPB
AVIATION...JLD