872
FXUS63 KDTX 071946
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
346 PM EDT Tue May 7 2024

.KEY MESSAGES...

- There is a chance of isolated to scattered strong to severe
thunderstorms south of a Midland to Port Huron line this evening,
the greatest chances are along/south of the I-94 corridor.

- Damaging winds, large hail and isolated tornadoes are the severe
weather risks.

- Warm and breezy conditions are expected Wednesday, followed by
cooler conditions with a chance of rain Thursday.

&&

.DISCUSSION...

Previous forecast reasoning offered by Area Forecast Discussions
issued earlier today remains valid. Initial arc of elevated shower
activity forced by lead system relative isentropic ascent and 850-
600mb thetae advection is now lifting northward through Southeast
Michigan. After this initial evaporative cooling response, will be
monitoring for the surface temperature and dewpoint recovery to
gauge for the potential of surface based, severe thunderstorms
between 6-11 pm local time. As forecasted, dewpoints have been slow
to rise and will have to overcome a due easterly trajectory off of
Lake Erie. A strong convergence bullseye on the nose of a deep
kinematic field and upper level diffluence is forecasted to
lift/pivot directly into portions of south central and southeast
Michigan this evening. Quality of large scale forcing is expected to
result in numerous to widespread showers and thunderstorms after. 22Z
The main threat this evening will be a potential for a tornado
(mainly for areas south of I 94) conditional to surface instability.
The secondary threat with thunderstorm activity (all areas) this
evening will be large hail. Modest midlevel lapse rates of 6-6.5C/km
should limit hail diameter potential, but any non-hydrostatic force
provided by mesocyclones could cause for hail diameters to exceed 1
inch. Again, the time period for potential severe weather is between
6-11 pm.

The zonal gradient orientation in the wake of the upper level trough
release will then set the stage for a relatively breezy day on
Wednesday. West winds of 20 to 30 mph. Little to no northward
advections will yield a sneaky warm day Wednesday with a dry, well
mixed boundary layer. No humidity to speak of but sunny
conditions and temperatures reaching the middle 70s to low 80s.

A very complex upper level height configuration is then expected to
develop for the Thursday and Friday time frame. An atypical
elongated trough axis is expected to reside in a largely west to
east fashion from the Central Plains to the Central Great Lakes. Not
a whole lot of confidence to be garnered from the setup as various
shortwaves digging southward from central Canada will have the
opportunity to disrupt the troughing. As it stands, Southeast
Michigan looks to be in a fairly close proximity to deeper
deformation forcing. Coupled jet forcing is also expected to eject
trough providing for an ageostrophic response and increased
frontogenesis. PoPs for Thursday are in the numerous to likely
category for much of the area and is warranted.

Various, lobes of modest planetary/potential vorticity are
forecasted to dig through Southeast Michigan for this upcoming
weekend. Given the trajectory, the predictability to the timing of
the shortwaves may prove difficult, but current trends suggest
Saturday is the most likely of time periods for precipitation.
Temperatures will be strongly dependent on cloud cover, with
current forecast suggesting temperatures of approximately 5 degrees
below normal.

&&

.MARINE...

Warm front tied to Midwestern low pressure continues to lift into
the central Great Lakes this afternoon supporting widespread showers
as well as scattered thunderstorms into this evening. A few strong
to severe storms are possible for areas south of Port Huron with all
hazards on the table. System`s cold/occluded front crosses the
region overnight setting up modest (~15-20kt) westerly flow for
Wednesday. Secondary low development over the Ohio Valley Wednesday
night results in a turn to northeasterly flow locally. Marginally
cooler airmass is drawn south, combined with the still tightened
gradient, is expected to allow for peak gusts 20-25kts over the
central portion of Lake Huron with near 30kts possible over Saginaw
Bay (lesser gusts over the remainder of the region). Additional
showers are also likely daytime Thursday before the low vacates.

&&

.PREV DISCUSSION...
Issued at 217 PM EDT Tue May 7 2024

AVIATION...

A line of decaying showers/storms is moving into Southeast Michigan
this afternoon. An influx of low-level moisture brings cloud bases
just above MVFR during the afternoon. Monitoring storm potential for
this evening as low pressure tracks across Lower Michigan bringing a
warm front, higher dewpoints, and strong shear with energetic jet
winds aloft. Limiting factor for storm development/growth tied to
questionable instability which struggles to become surface based as
storms move in from the west. Timing for most of this convective
activity falls between 6 PM and 9 PM with a slightly earlier start
at MBS. Clouds try to scour out after midnight offering potential
for a bit of MVFR fog as the humid airmass cools. Breezier day
Wednesday with afternoon gusts in excess of 25 knots and VFR
conditions.

For DTW/D21 Convection...

Scattered to numerous thunderstorms expected this evening with
potential for some strong storms capable of 40+ mph gusts, hail
larger than a half inch, and possibly a tornado or two within the
vicinity. Scattered discrete storms are favored early before
multicellular clusters move through later in the evening. Storms
move from west to east at 40 mph between 6 PM and 9 PM.

DTW THRESHOLD PROBABILITIES...

* High for thunderstorms 23-02Z this evening.

* Medium for ceiling at or below 5000 feet today, high during
  evening, then low overnight.


&&

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

$$

DISCUSSION...CB
MARINE.......KDK
AVIATION.....KGK


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