329
FXUS63 KAPX 131955
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
355 PM EDT Sat Jul 13 2024

.KEY MESSAGES...

- Thunderstorms return tonight into Sunday morning, including
  the potential for a few strong storms.

- Additional pop-up storms possible Sunday afternoon.

- Hot and humid Monday

- Showers and thunderstorm Chances Monday and Tuesday

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 350 PM EDT Sat Jul 13 2024

Pattern Synopsis:

Subtle shortwave ridging will continue to slide east of the northern
Great Lakes tonight as surface high pressure builds closer to the
Atlantic coast. Meanwhile, a potent shortwave/jet max embedded in
the main mid/upper level flow will punch across the upper Midwest
and over the far northern Great Lakes/southern Ontario by Sunday
morning. Favorable ascent aloft generated by this wave will support
a surface cyclone that looks to trek across northern Ontario and
over south Hudson Bay on Sunday.

Forecast Details:

Thunderstorms return tonight into Sunday morning -- Aside from a few
pop-up showers and storms still possible near Whitefish Bay into
this evening, quiet weather is expected across the rest of the area
into tonight. While there is high confidence in much of northern
Michigan seeing showers and storms tonight and Sunday morning, there
is relatively high uncertainty as to how showers/storms will evolve.
Current confidence is that storms will form across parts of
Wisconsin later this afternoon/evening and move across Lake Michigan
into western portions of northern Michigan tonight. A second round
of storms will be possible late tonight/Sunday morning on the heels
of the first round with a potential MCS moving across the upper
Midwest and into the Great Lakes. Buoyancy on the order of 500-1,500
J/kg MUCAPE looks to be in place ahead of both potential rounds,
with relatively weak deep-layer shear around 25-30 kts. A few
storms/segments may be capable of producing damaging wind gusts --
primarily in closer proximity to the lakeshore -- tonight through
Sunday morning. Should multiple rounds of storms train across
specific locations, locally heavy rainfall of 1-2"+ will be possible
and may create ponding on some area roadways.

Additional pop-up storms possible Sunday afternoon -- After morning
showers/storms move out, there is expected to be a lull in precip
chances into the early afternoon hours. Additional development is
still uncertain at this time as it will depend on the
arrival/departure time of aforementioned storms and how quickly
breaks in the clouds can form, allowing for destabilization in the
afternoon. Current thought is that this will occur in time for
additional scattered showers/storms to form across parts of northern
Michigan, primarily east of I-75 where ant lingering outflow
boundaries/lake breeze boundaries can interact. A few strong storms
will be possible in the presence of ~1,000 MLCAPE and ~30 kts of
deep-layer shear to support at least some organization.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 350 PM EDT Sat Jul 13 2024

Pattern Synopsis and Forecast: An anchored upper level ridge over
the western CONUS will continue zonal flow aloft over the northern
Rockies into the northern Plains and Great Lakes region through mid
week. A very warm and wet airmass near the surface currently resides
over the northern plains. This airmass will make its way towards MI,
where surface dewpoints are forecasted to reach into the high 60s
and low 70s for most of the CWA Monday afternoon (some slightly
drier air could be over eastern upper). A cold front will begin to
slide down the Canadian plains along the front range, kicking off
convection over ND/MN Sun afternoon/evening. This will likely induce
shortwaves aloft on the zonal flow, which will help aid convection
Monday afternoon over WI/IL. Some of the northerly winds near the
surface with the initial front could reach the wave and create weak
cyclogenesis as the convection approaches MI. Isolated to scattered
storm chances exist for Monday afternoon and night (due to slight
uncertainty in timing with these features). Best chances for storms
at this time are over northern lower. Skies have a chance for
clearing ahead of storms Monday, which could bump heat indices into
the 90s Monday afternoon. This will be hard to pin down exactly
where will be the hottest due to the uncertainty with cloud cover.

A seasonally deep upper closed low will start to drop south from
eastern Hudson Bay. Clouds and chances for showers will linger
Tuesday. A cold front will move through early Wednesday, brining in
cooler and drier Canadian air. Low to no rain and storm chances for
the end of the work week and next weekend.

Primary Forecast Concerns/Key Messages:  Although the air will feel
heavy and humid Monday afternoon, there is enough uncertainty in
skies that heat indices could remain in the high 80s to low 90s for
most of northern lower. Eastern upper has chances of seeing slightly
drier air Monday, which will keep heat indices lower. Places where
skies can clear could see temperatures quick warm, possibly rising
heat indices into the low to mid 90s. High uncertainty remains on
what Monday`s storm chances will look like. Confident exists in the
environment being capable of producing storms with some severe
attributes (hail and winds) and even higher chances of torrential
rainfall with storms (PW values average around 1.3"  Monday
afternoon). However, forcing that could lead to storm initiation
might be weak by the time they reach northern MI. At this time,
chances for isolate to scattered showers and thunderstorms for
Monday afternoon and night are in the forecast. With these storms a
few could be capable of marginally severe hail and winds. Chances
for storms decreases through the day Tuesday.


&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 211 PM EDT Sat Jul 13 2024

VFR conditions are expected to continue through tonight. Primary
aviation concern will be the arrival of shower and thunderstorm
chances from west to east late tonight that will continue through
Sunday morning. Any strong storms that pass over TAF sites may drop
VSBYs to MVFR/IFR for a time and produce strong wind gusts,
primarily Sunday morning. MVFR CIGs may also work into the eastern
U.P./CIU late in the issuance period.

&&

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

&&

$$

SHORT TERM...DJC
LONG TERM...ELD
AVIATION...DJC