557
FXUS63 KDTX 250032
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
832 PM EDT Fri May 24 2024

.KEY MESSAGES...

- Showers and thunderstorms move in tonight largely after midnight
and continue into Saturday morning. An isolated storm may become
severe with strong winds or hail.

- Dry weather returns Saturday afternoon through Sunday morning.

- Showers are likely again with a chance of thunderstorms Sunday
afternoon and Sunday night.

- The Memorial Day outlook calls for cool temperatures with showers
likely Monday and Monday night.

&&

.AVIATION...

Relatively high amplitude shortwave ridging will result in VFR
conditions throughout the evening. Southeasterly flow trajectories
will maintain a dry feed in the lowest 6.0 kft agl through
approximately 09Z tonight. A zonal upper level jet exit region will
cut into Southeast Michigan early Saturday morning knocking down
heights and allowing for large scale ascent. Still some question on
coverage of shower and/or thunderstorms across Southeast Michigan in
the 9-12Z timeframe but cyclonic absolute vorticity advection in the
same time window is expected to result in convective development
overhead. Did roll the Prob30 group into a TEMPO and will monitor
00Z trends to assess likelihood of thunderstorm activity. Heavy
rainfall is expected with the convection, no strong or severe
weather. A period of MVFR ceilings is expected across Southeast
Michigan sometime between 09-15Z.

For DTW/D21 Convection...Arrival of large scale forcing is expected
to result in initiation/development overhead of showers and possible
thunderstorms between 09-12Z. Included shower mention at this time
and will assess for TSRA.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms overnight tonight (9-12Z)

* Moderate for ceilings aob 5kft by early tomorrow morning.

&&

.PREV DISCUSSION...
Issued at 335 PM EDT Fri May 24 2024

DISCUSSION...

Active weather this Memorial Day weekend and beyond for southeast
Michigan. Many opportunities for precipitation ahead, and warmer
than average temperatures hang around for the weekend before a
cooling trend begins with the start of the week.

The main focus of the forecast for today are the storms projected to
move in overnight tonight. Due to the timing of storms passing
between 06-12Z, the storms will weaken after sunset and become
unlikely to produce severe weather due to overnight surface cooling
leading to a near-surface temperature inversion. Should a parcel be
forced upward, PWATS around 1.25-1.5 inches, MUCAPE nearing 1000
J/kg, and 30 knots of shear could potentially help sustain the
updraft and produce some rain and/or small hail. Any developing
storms are unlikely to be severe, but an isolated severe storm
remains possible. SPC keeps a general thunderstorm risk in place for
this system.

Near-zonal flow aloft behind this system briefly brings back clear
skies on Saturday behind the front. Temperatures in the upper 70s,
reaching 80 on Saturday, cooling off slightly to the mid to upper
70s Sunday. While these temperatures are only slightly above the
climatological average and are not unreasonable for this time of
year, those sensitive to heat should prepare an effective cooling
method and plan to stay hydrated for any outdoor Memorial Day
festivities over the weekend.

Widespread showers and storms return Sunday evening as a longwave
upper level trough brings a low pressure system into the area from
the southwest. The system will begin to occlude as it begins to
impact the area, so much will be determined on how far north that
occlusion point reaches. Thunderstorms and severe weather are a
possibility with this system, currently expected to move through
between 0Z and 12Z Monday. SPC gives a Marginal risk for severe
weather for the southern portion of the CWA. WPC also has a Marginal
risk for excessive rainfall on their Day 3 Outlook, meaning between
a 5-15% risk of rainfall exceeding flash flood criteria. Guidance
has yet to agree on rainfall totals for southeast Michigan, with
deterministic models ranging from two tenths to to inches, but
ensemble runs put mean QPF values just over a half inch.

As the low pressure moves out, the potential for light showers to
form exists Monday, fueled by cold conveyor belt wrapping around the
low. Temperatures continue to drop Monday as cloud cover makes
reaching the 70s difficult. Longwave trough remains in place through
the middle of the week, dropping daily high and low temperatures
into the 60s and 40s respectively, while also bringing more chances
for some minor showers caused by some shortwaves embedded within the
larger trough.

MARINE...

An upper level ridge exits the Great Lakes this evening as a low
pressure system works northward into south-central Canada. Gradient
winds take on an easterly trajectory while a strengthening low-level
subsidence inversion limits gust potential. Gusts may approach 25
knots across Saginaw Bay, but will forego a Small Craft Advisory
given the infrequency of higher gusts. A shortwave feature shearing
off the parent upper level feature to the west progresses into the
central Great Lakes tonight and Saturday morning as a secondary
surface low develops along the primary system`s cold front. This
presents an opportunity for thunderstorms and locally higher
winds/waves through Saturday morning. The strongest dynamics are
expected to depart before thermodynamic profiles become more
favorable for mechanical mixing processes, therefore no headlines
are anticipated. An occluded low then tracks across Wisconsin and
The UP Sunday night which drags a potent LLJ across the waterways.
More showers and storms are expected, some of which may be strong to
severe. Potential also exists for Small Craft Advisory conditions as
early as Sunday evening, marked by gusts approaching 30 knots and
occasional waves near 5 feet.

&&

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

$$

AVIATION.....CB
DISCUSSION...BC
MARINE.......KGK


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at www.weather.gov/detroit.