681
FXUS63 KDTX 211727
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
127 PM EDT Tue May 21 2024

.KEY MESSAGES...

- There is a chance of showers and thunderstorms this afternoon.
Potential exists for a line of strong to severe storms to arrive
late tonight. Damaging wind is the greatest threat tonight.

- Warm and muggy conditions with high temperatures in the mid to
upper 80s continue through mid week until a cold front moves through
the region Wednesday.

- There is one more chance for showers/storms Wednesday before a
cooler and less humid air mass follows the front for the late week
period.

&&

.AVIATION...

Morning low stratus has begun rapidly clearing early this afternoon
over the northern portions of the area as a diurnal cu Field expands
in from the south. Uncertainty in thunderstorm potential this
afternoon is still fairly high however a thermal gradient is set up
between PTK and FNT from differential heating today from the
aforementioned stratus lingering in the north. Should convection
develop, it likely will be focused along/near this boundary. Given
some high-res model guidance is picking up on this especially
towards PTK< just enough confidence to switch to a Tempo group. FNT
confidence not high enough to make the change at this point but will
amend as needed this afternoon based on observational trends.
Decaying line of showers and storms possible late tonight/early
Wednesday morning though high uncertainty still exists in how well
this activity can maintain itself as it moves across the state at
the diurnal instability minimum.

For DTW/D21 Convection... There remains a low chance at convection
this afternoon though best potential looks to hold north of DTW
towards PTK/FNT instead. Decaying Midwest convection is expected to
work across the state overnight however given the unfavorable
diurnal timing, high uncertainty how much, if any, reaches Detroit.
That said, even in model outcomes where rain reaches DTW early
Wednesday morning, thunder chances are very limited so have opted
for a Prob30 SHRA mention instead.

DTW THRESHOLD PROBABILITIES...

*  Low for thunderstorms this afternoon and again late tonight.

&&

.PREV DISCUSSION...
Issued at 307 AM EDT Tue May 21 2024

DISCUSSION...

Window of deeper layer stability set to emerge through at least the
first half of the daylight period, as shortwave ridging briefly
governs conditions within the immediate wake of an exiting MCV.
Diabatic heating of resident warmth and humidity more typical of mid
summer will gradually erode this stability through the day,
augmented by renewed moisture advection fixated along a northward
drifting frontal boundary. Ill-defined signal within the model
spectrum regarding late day convective potential in an environment
characterized as modestly unstable but generally lacking in larger
scale forced ascent. Forecast will continue to highlight at least a
lower probability of convective development, targeting a corridor
within the M-59/I-69 region as localized areas of convergence or
differential heating near the frontal zone and subsequent outflow/
lake breeze interaction offer the greatest potential. Plausible for
a few stronger wind gusts to materialize as the degree of
instability offers some water loaded updrafts, but lack of shear
minimizes the opportunity for greater organization and a larger
severe risk through the daylight hours. Highs today again landing
solidly in the 80s.

Attention tonight focused on behavior of convection expected to
organize across the midwest later today. High magnitude forced
ascent featured within the elongated height falls and cold front
attendant to the parent upper Miss valley trough will effectively
drive upscale growth of this activity with a progressive transition
toward a linear mode. The local convective potential and prospective
vigor with this inbound convective line remains highly conditional
on retaining sufficient destabilization, acknowledging the arrival
window within a less favorable period /05z-09z/. A familiar position
locally, which often lends to the greater potential holding just to
the west. General consensus of the hi res model solution space
suggests a gradual weakening trend as the convective line transits
lower Michigan. Strong winds become the main threat should a greater
response arrive locally for the early morning hours.

Trailing cold front arrives Wednesday. Frontal convergence remains
weak as the boundary becomes parallel to the mean flow, but
interaction with a moist boundary layer condition provides a limited
window for convective development. Higher precip chance with
eastward extent, with overall pace of the front relative to daytime
destabilization dictating whether a more organized convective
episode can manifest locally or remain to the east/southeast. Drying
conditions with time through the latter half of the day.

Less active pattern to finish the work week. High pressure arrives
Thursday, beneath lower amplitude mid level west-southwest flow.
Temperatures remain edged on the warmer side of average, but with
notably lower humidity. Similar conditions hold into Friday as upper
ridging migrates the region.

MARINE...

A front has stalled out across southern Michigan and will get pulled
back north as a warm front today. The front will be associated with
a strong low pressure system developing over the Plains that will
lift up to western Lake Superior by this evening. The low will then
send a cold front through the Great Lakes on Wednesday with showers
and thunderstorms possible Tuesday night and Wednesday ahead of it.
Conditions are expected to remain below Small Craft Advisory
criteria tonight through Tuesday, though locally higher winds and
waves will be possible within any thunderstorms. Winds increase out
of the south to 20 to 30 knots ahead of the associated cold front
Wednesday, then veer to the west Wednesday night into Thursday while
remaining gusty to around 25 knots. Less humid air settles in for
the late week as high pressure builds in.

CLIMATE...

Here are the record high temperatures for May 21-22:

May 21st:
Detroit                92 (set in 1977)
Flint                  93 (set in 1921)
Saginaw/Tri-Cities     94 (set in 1977)

May 22nd:
Detroit                90 (set in 1994)
Flint                  91 (set in 1934)
Saginaw/Tri-Cities     89 (set in 1992)

Here are the record high low temperatures for May 21-22:

May 21st:
Detroit                71 (set in 2013)
Flint                  67 (set in 1934)
Saginaw/Tri-Cities     66 (set in 2021)

May 22nd:
Detroit                67 (set in 1941)
Flint                  65 (set in 1977)
Saginaw/Tri-Cities     68 (set in 1977)

&&

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

$$

AVIATION.....KDK
DISCUSSION...MR
MARINE.......MR
CLIMATE......MR


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