626
FXUS63 KAPX 171358
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
958 AM EDT Mon Jun 17 2024

.KEY MESSAGES...

- Hot and humid temperatures as well as showers and
  thunderstorm chances this afternoon and evening

- Very hot, humid conditions expected to continue through the middle
of the week.

- Chances for showers/storms at times this week.

&&

.UPDATE...
Issued at 947 AM EDT Mon Jun 17 2024

Warm and humid airmass now well established across the northern
Great Lakes. Despite this abundant moisture, conditions remain
dry with no appreciable forcing to drive shower development.
That may change some this afternoon as current sun-filled skies
drive the development of low level instability. No inhibition to
moist updrafts to be found, but lack of trigger for updrafts to
focus on remains hard to come by. Still think the development
of a backed wind field off northern Lake Huron will allow some
scattered moist convection this afternoon...especially across
eastern upper and northeast lower Michigan. Will also need to
watch movement of outflow boundary from current upstream MCS,
with this being a possible source for forced convergence across
eastern upper Michigan this afternoon (if it can survive).
Nothing widespread severe expected given weak wind fields aloft.
If storms can form, locally heavy rain and some brief wet-
microburst produced gusty winds are possible. Very warm today,
with highs expected to top out in the upper 80s to lower 90s
across inland areas south of the Might Mac. Expect readings to
remain a touch cooler near the big waters and across eastern
upper Michigan.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 351 AM EDT Mon Jun 17 2024

Pattern Synopsis and Forecast: Current satellite and radar shows a
few isolated showers and storms moving into Canada from the upper
penisula early this morning as they exit the CWA. Surface
observations show moisture advection continuing from west to east,
raising dew points into the mid to high 60s by mid day today. PW
values of around 1.5" will exist today as deep moisture advection
continues around an anchored upper level high pressure centered over
the Carolinas. Upper level lows exist over central Canada and the US
West, leading to strengthening southwest flow over the central
plains and Great Lakes region today. Slight ridging extending from
the upper high will rotate over the state today slightly increasing
heights aloft. This combined with southwest winds near the surface
(leading to downsloping in some locations) will result in
temperatures warming around 5 to 15 degrees from yesterday (reaching
into the low to mid 80s for eastern upper and high 80s to low 90s
for northern lower). Model soundings depict an environment with
ample instability and weak (but existent) speed shear through the
column. With convective temps around 90, skies should start to fill
in with CU & towering CU over northern lower in the afternoon hours.
Southwest winds will likely work to keep the lake breezy away until
the later afternoon hours (when winds are forecasted to weaken).
Some CAM guidance depicts the lake breeze pushing inland near the
tip of the mitt, which in theory should help kick up a few showers
and thunderstorms in this environment. The main hazards with the few
storms that do form will likely be heavy rain, small hail, and brief
gusty winds. Chances for isolated showers and thunderstorms will
linger through tonight.

Primary Forecast Concerns/Key Messages: Lots of uncertainty still
exists in the forecast today, as the CWA will likely have a high
CAPE low shear environment with chaotic triggers for convective
initiation. CAM soundings show around 2-3k j/kg of SBCAPE with
mixing heights rising to around 4-5 kft around mid day. Convective
temps are around the low to mid 90s for northern lower as well.
All of this points to a likely scenario of skies filling in
where convective temperatures can be reached. Afternoon
temperatures will feel hot and muggy, however the hottest
temperatures will not last that long due to the chances of
shower and storm development in those areas. Some CAMs are not
picking up on the diurnally driven convection as much, and need
a trigger. The HRRR depicts the lake breeze moving over the
northern areas of northern lower later this afternoon, which
could be that trigger for showers and storms.

To summarize, this afternoon will feel hot and humid (with some of
the best chances for the hottest temperatures near Saginaw
Bay). However, chances for afternoon storms will likely allow
for quick relief to most areas in the form of rain, outflows, or
clouds filling in the skies overhead.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 351 AM EDT Mon Jun 17 2024

Pattern Synopsis: Impressive ridging will grip most of the
CONUS east of the Mississippi River through the duration of the
workweek as troughing churns over the Pacific NW and northern
Great Plains. To put this ridging in perspective, forecast 500mb
heights of 594+ dam over a several day stretch would exceed
climatological max values during that span based on a 30-year
reanalysis period centered around the middle of June. Thus, the
strength of aforementioned ridging in place heading into the
weekend is rare. With surface high pressure centered over the
Atlantic, the Great Lakes look to be caught between surface
features into the middle of the week before high pressure may
build in more firmly heading into the weekend.

Forecast Details: Very hot, humid conditions -- The potential
for very hot, humid weather is expected to persist across the
Great Lakes trough the middle of the week, and perhaps through
the end of the week as well. Aforementioned ridging/high
pressure placement will keep Michigan in south/southwesterly
low-level flow through Wednesday, allowing for warm,moist
advection to continue with no major frontal passages. In turn, a
very moist boundary layer characterized by dewpoints in the mid
60s to low 70s is expected to stick in place for at least
several days. Combined with this will be the potential for high
temperatures to climb into the low to mid 90s Tuesday and
Wednesday, and mid 80s to low 90s beyond that this week.
Furthermore, overnight lows staying in the upper 60s Monday
night and low to mid 70s Tuesday night will offer little relief
from the early week heat. The main caveat and source of
uncertainty at this time continues to be the potential for
convection/convective debris impacting high temperatures through
the middle of the week, as the full potential of high
temperatures may not be realized should storms form near/across
the region during the afternoon hours.

Chances for showers/storms at times this week -- As mentioned above,
there will be chances for showers/storms at various times this week.
However, pinpointing any precise timing and locations is highly
uncertain at this time. Aforementioned moisture-rich boundary layer
will lead to ample buoyancy to support thunderstorm chances most
days -- especially during the afternoon and evening with peak
heating. There is an expected lack of more defined forcing
mechanisms to trigger convection across the region, but any subtle
forcing may be enough to trigger pop-up storms at times through the
duration of the work week.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 704 AM EDT Mon Jun 17 2024

Currently VFR conditions at all terminals with skies generally SKC -
FEW250 and winds AOB 10kts and VRB. Winds will become SW/W with
occasional gusts at a few terminals. High uncertainty with afternoon
VCSH/VCTS, however environment is favorable for a few ISO TSRA/SHRA
which could come close to northern lower terminals. Slightly higher
confidence over eastern upper terminal VCSH. Brief MVFR/IFR cigs and
vis could be seen near TSRA/SHRA. Chances should move out of region
by end of the period.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert until midnight EDT tonight for MIZ020-025-
     026-031.
MARINE...None.

&&

$$

UPDATE...MSB
SHORT TERM...ELD
LONG TERM...DJC
AVIATION...ELD