202
FXUS63 KDTX 140353
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1153 PM EDT Tue May 13 2025

.KEY MESSAGES...

- Above average temperatures persist through the week.

- Scattered showers/thunderstorm chances Wednesday.

- A Slight Risk (2/5) for severe thunderstorms exists Thursday night
  primarily between 11pm and 3 am. The potential for large hail and
  damaging winds appear to be the main threats.

- Cooler and less humid weather is anticipated for next weekend.

&&

.AVIATION...

A downward trend in shower coverage and intensity continues through
the late night on the north fringe of slow moving Ohio valley low
pressure. A wide range of ceiling conditions also follow a nocturnal
transition into more widespread MVFR and then into IFR/LIFR with a
fog component toward sunrise. Any larger breaks of clear sky have
potential to result in a quick drop into IFR given T/Td in the 60s
with only a few degrees of spread. Conditions are slow to improve
during the morning as the surface trough moves toward and then into
Lower Mi during the afternoon to combine again with daytime
instability for another round of showers into Wednesday evening.

For DTW/D21 Convection... An isolated thunderstorm is possible
Wednesday afternoon but with low predictability on timing and
location.

THRESHOLD PROBABILITIES...

* High for ceiling aob 5000 feet through the forecast.

* Low for ceiling/visibility below 200 ft and/or 1/2 SM late
  tonight and early in the morning.

* Low for thunderstorms Wednesday afternoon and evening.

&&

.PREV DISCUSSION...
Issued at 333 PM EDT Tue May 13 2025

DISCUSSION...

An axis of deep moisture with connection to the Atlantic and Gulf is
in place across Southeast Michigan. The PWAT on the 13.12z DTX raob
was 1.40 inches and areawide surface dewpoints are in the 60s. The
next few days, through midday Thursday, will be governed by moist
adiabatic lapse rates that will bring periodic chances for showers
and isolated thunder activity. The most favorable timing for
convective development both today and Wednesday will be with daytime
heating. Light easterly flow with low LCL heights limits much in the
way of convective vigor. It is challenging to offer much temporal or
spatial detail to the precipitation forecast as the EPS interquartile
range of 24 hr QPF at all locations is less than 0.33 of an inch
each of the next few days.

The arrival of the exit region to a strong pacific jet streak will
cause geopotential height falls to impact Southeast Michigan
Thursday night. Latest indications are that midlevel cooling will
occur in advance of the upper level low to result in steep midlevel
lapse rates exceeding 8 C/km. Recent model solutions have been
converging on a UVV signal that suggests the best time period for
thunderstorm activity will fall in the 03-07z time window.
Combination of the lapse rates with rich thetae/moisture from the
surface to 5.0 kft agl is expected to result in very unstable
conditions, CAPES of 2000-3500 J/kg. Despite the late evening to
overnight timeframe, it is important to point out that confidence is
increasing in this magnitude of instability owing to the lapse rates.
The uncertain aspect of the forecast is to what extent the near
surface convective inhibition will erode which will impact both the
coverage of activity and the potential for surface based impacts.
0-6km bulk shear magnitude is forecasted to increase to greater than
40 knots Thursday evening resulting in the potential for mesocyclones
and supercellular storm organization. Will need to monitor forecast
trends as this time period approaches. The latest Swody3 has the
majority of the forecast area in a Slight Risk for severe weather.

Cool northwest flow is likely for next weekend as deep troughing
remains in place over the Great Lakes. Depending on timing of
successive cold fronts or lake breeze boundaries, the temperature
forecast will be up for revision.

MARINE...

A weak pressure gradient continues to maintain lighter southeast
flow through the midweek period with bouts of isolated to scattered
showers and possibly some embedded thunderstorms. A warm front will
then pass over the Great Lakes late Thursday night into Friday,
which will veer wind direction to the southwest and will bring some
more elevated wind speeds and gust potential. Additionally, some
more organized thunderstorms will be possible along the warm front,
centered through Friday morning.

&&

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

$$

AVIATION.....BT
DISCUSSION...CB
MARINE.......AM


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