702
FXUS63 KDTX 170339
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1139 PM EDT Thu May 16 2024

.KEY MESSAGES...

- Numerous showers late tonight and into early Friday morning.

- Chance of thunderstorms Friday afternoon.

- Very warm this weekend through early next week. Increased chances
for thunderstorms Monday night into Wednesday morning next week.

&&

.AVIATION...

Increasing lower VFR cigs in the 5-10kft range will occur into the
overnight with eventual scattered showers (and possibly an isolated
thunderstorm or two) late tonight into early Friday morning. By
Friday morning, MVFR cigs will be more likely even as showers move
east of the region. Additional showers/isolated thunderstorms will
be possible late in the day as well (20z-02z). Light southeast to
south flow will veer to southwest Friday and then become light and
variable Friday night.

For DTW/D21 Convection... An isolated thunderstorm is possible
within a broader area of showers late tonight. The storms will be
elevated and weak but capable of a brief lower visibility downpour
through Friday morning. A second window for a thunderstorm or two
will occur 21z-01z Friday afternoon/evening. Again, locally heavy
downpours will be the main concern (and the exception).

DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 ft or less late tonight and Friday
  morning.

* Low for thunderstorms late tonight into early Friday morning and
  then again by late Friday afternoon/early evening.

&&

.PREV DISCUSSION...
Issued at 301 PM EDT Thu May 16 2024

DISCUSSION...

Weak afternoon destabilization and inbound height falls across
Western Lower Mi is forecast to initiate scattered convection across
SW Lower Mi late this afternoon/evening. Remnants of this convection
may advance into Se Mi this evening before surface based instability
wanes with the loss in daytime heating. Mid level troughing now
advancing into the northern and western Great lakes will track
across Lower Mi late tonight through Friday morning. Overall, system
relative isentropic ascent is forecast to be stronger from the thumb
region and points north toward daybreak Friday, and much weaker
across the rest of the forecast area. A plume of deep layer moisture
(precipitable water values just over an inch) preceding the mid
level trough axis and steepening mid level lapse rates (weak
elevated instability) will still support scattered to numerous
coverage of showers and isolated thunderstorms late tonight/early
Fri morning. The increasing cloud coverage and low level moisture
advection (sfc dewpoints rising into the 50s) will suppress
nocturnal cooling, leading to min temps in the 50s.

Lingering early morning convection will give way to decreasing cloud
cover in the wake of the surface trough axis late Fri morning into
the afternoon. Recent 12Z model guidance suggests the strongest push
of mid level subsidence and subsequent capping will hold off until
Fri aftn/evng as mid level negative vorticity advection arrives from
the northwest. Lingering sfc troughing over Se Mi combined with sfc
dewpoints near 60F and daytime temps well into the 70s will support
increasing daytime instability, suggesting some scattered convective
development perior to the mid levels becoming capped. Model
soundings suggest 0-1KM ML Cape of 800 to 1500 J/kg, focused along
the sfc trough axis over the eastern half of the forecast area. Bulk
shear parameters of only 20-25 knots will limit the risk for strong
to severe convection. There does however appear to be a narrow
window of opportunity Fri aftn prior to the strengthening of the mid
level cap when convective downdraft potential may be supportive of
isolated strong/severe thunderstorms.

Mid level ridging will dominate Lower Michigan through the weekend.
Despite rising mid level geopotential heights on Saturday, an
easterly component to the sfc winds off the lakes and the strength
of the mid level subsidence will limited mixing potential to a
degree, suggesting afternoon highs from the upper 70s to around 80
(with cooler readings near Lake Huron). Further building of the mid
level ridge toward the end of the weekend and a shift to a more
southerly wind trajectory will push afternoon highs into the lower
to mid 80s across most of the forecast area on Sunday.

Persistent low level SSW flow will ensure well above normal
temperatures into early next work week, with high probabilities for
highs both Monday and Tuesday into the 80s. The 12Z deterministic
solutions indicate a short wave trough ejecting out of the southwest
across the Great Lakes Mon night, supporting a chance for
convection. A more amplified wave is then forecast to eject out of
the longer wavelength western US trough across the Great Lakes in the
late Tues to early Wed time frame. This will be a more dynamic
system, thus supporting greater shower/thunderstorm chances. There
is certainly a severe weather potential, predicated to a degree on
whether the dynamics can line up with peak instability.

MARINE...

A weak low pressure system lifts across Lake Superior tonight,
sending a dissipating front across the central Great Lakes overnight
into early Friday. Despite the overall weak system, a disturbance
aloft will help provide enough forcing for scattered to numerous
showers with isolated non-severe storms to develop after midnight
and into early Friday. A weak ridge then fills into the area
Saturday into Sunday, promoting continued light winds and mainly dry
conditions. The next disturbance moves into the area Monday night
into Tuesday with slightly stronger southerly winds along with
scattered showers and thunderstorms.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....DG
DISCUSSION...SC
MARINE.......TF


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