793
FXUS63 KDTX 210550
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
150 AM EDT Tue May 21 2024

.KEY MESSAGES...

- Additional storms are possible this afternoon into the evening.
  Damaging wind is the greatest threat.

- 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...

Outside of a very sparse rain shower, rain chances have abated in
the wake of a passing upper-level wave. Nighttime satellite
highlights extensive coverage of low-level stratus that has
developed in the wake of the wave, presently situated over west-
central Michigan. hi-res model guidance highlights low-level stratus
spreading inland, extending into KMBS and possibly into KFNT, where
MVFR to IFR cigs will be possible. This stratus deck will further be
reinforced from a strengthening low-level inversion, which would
maintain coverage into the morning hours. Sunshine will lift and
scour out any stratus development by the late morning.

For this afternoon, diurnally heating will provide the chance for
shower and thunderstorms development, but confidence remains very
low regarding timing and coverage potential. KPTK to KFNT have some
signal for development in model output, where a PROB30 has been
introduced.

For DTW/D21 Convection...

Outside of a stray shower, generally dry conditions are expected
overnight. The chance for a shower or storm will return this
afternoon and evening, but confidence is very low regarding coverage
and timing.

DTW THRESHOLD PROBABILITIES...

*  Low this morning, low this afternoon and evening.

*  Low for aob 5000 feet this morning.

&&

.PREV DISCUSSION...
Issued at 440 PM EDT Mon May 20 2024

DISCUSSION...

The early afternoon convective cluster followed the warm front
supported instability gradient along and north of the I-69 corridor
this afternoon. Hourly mesoanalysis showed 0-6 km bulk shear
sneaking up to around 30 knots as the storms increased coverage,
just enough for some forward propagation and sporadic wind damage as
the storms matured. The southward moving outflow then became the
focus of a secondary development capable of its own sporadic wind
damage and large hail before exiting into Ontario at press time.

Yet another round of storms is on schedule to affect Lower/SE Mi
this evening as upstream activity develops eastward. Mid afternoon
satellite imagery clearly shows the outflow reinforced warm front
beginning to recover northward or at least hold a position near the
M-59 to I-96 corridors for the late afternoon. Surface pressure
falls associated with the inbound MCV will be sufficient to draw
instability northward into SW Lower Mi late in the diurnal cycle
while the mid level circulation further supports organized
convection. Maintenance of instability then becomes more
questionable after midnight as the surface low slips through central
Lower Mi. The surface low is a tracer for MCV support that carries
the remaining convective clusters into Lake Huron before sunrise.

The MCV subsidence wake appears as a substantial short wave ridge in
model data to start off Tuesday. The effective frontal boundary
sinks back south as well to leave conditions dry for the morning
before a transition to return flow moisture transport occurs in the
afternoon. Scattered showers and a stray thunderstorm are possible
through the evening as the surface warm front sharpens up ahead of
the next Midwest low pressure system. The southern stream
circulation in today`s Pacific coast trough has good model agreement
on a track into the Midwest where it deepens substantially by
Tuesday night. The leading cold front becomes the subject of the
next round of severe thunderstorm potential for our area, although
the latest model trends exhibit a strong nocturnal limiting factor
for eastward longevity. The 12Z HREF hi-res members show good
agreement on a convincing weakening trend across Lower Mi late
Tuesday night. This is a surprising solution given how strongly
forced the pattern is on the background of the larger scale low
pressure system. The SPC Slight/Marginal risk combo nicely depicts
the decreasing potential for severe intensity into Wednesday
morning.

MARINE...

A stalled boundary extends from southern Lake Huron to southern Lake
Michigan with a mid level system rippling along it. This helped
touch off a afternoon round of storms.  Additional mid level support
this evening will lead to another round of storms reaching the
eastern lakes around midnight. The front will linger Tuesday which
could help another round of storms in the afternoon. A stronger
surface low will then lift northeast through northern Michigan
Tuesday night into Wednesday, pulling a cold front through the
region leading to yet another round of storms Wednesday. 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 20th through
May 22nd:

May 20th:
Detroit                91 (set in 1977)
Flint                  92 (set in 1934)
Saginaw/Tri-Cities     93 (set in 1977)

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 20th
through May 22nd:

May 20th:
Detroit                68 (set in 1934)
Flint                  65 (set in 1939)
Saginaw/Tri-Cities     70 (set in 1975)

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.....AM
DISCUSSION...BT
MARINE.......DRK
CLIMATE......BT


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