138
FXUS63 KDTX 281720
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
120 PM EDT Fri Jun 28 2024

.KEY MESSAGES...

- Bit warmer and slightly more humid today with scattered light
showers possible this evening.

- Wider spread showers and a few thunderstorms late tonight into
Saturday morning.

- Muggy daytime Saturday with a chance for scattered storms latter
half of the day ahead of a cold front. Some storms could be severe
with damaging winds and locally heavy rain as main hazards.

- Cool and dry weather for the second half of the weekend into early
next week.

&&

.AVIATION...

Strong 700-650mb thetae advection has led to an abundance of virga
on regional radar mosaic this afternoon. A dry southeasterly feed
will persist throughout the afternoon and into the early evening
hours. There is some model signal that a sprinkle will be possible
beginning after 00Z. Confidence is too low to include this issuance.
Organized deep cyclonic flow will then push into the area after 08Z
tonight. A secondary thetae surge will then bring the chance for
showers and thunderstorms at the Detroit terminals after 08Z. Did
time out a 2 hour tempo for thunderstorm activity between 09-11Z
Saturday. Well mixed westerly flow is forecasted to develop behind a
cold front Saturday afternoon with wind speeds of 15 to 25 knots.

For DTW/D21 Convection...The potential exists for thunderstorm
activity between 09-11Z Saturday morning.

DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling aob 5000 ft Saturday morning.

* Moderate for thunderstorms Saturday morning.

&&

.PREV DISCUSSION...
Issued at 337 AM EDT Fri Jun 28 2024

DISCUSSION...

Influence of Canadian high pressure wanes today as it shifts to the
eastern seaboard. Southerly return flow develops as a result
supporting modest WAA into southern lower MI with 850mb temps
climbing from ~10C this morning to ~14C by this evening. While
altostratocu/cirrus will steadily stream into the area ahead of the
next approaching shortwave(s), advection is expected to be
sufficient to push highs back into the upper 70s across the region,
with a few areas reaching low 80s not completely out of the realm of
possibility.

Lower level southwest flow strengthens late this evening into
tonight as remnant ridging is flattened by an upper trough dropping
out of Canada coincident with the arrival of the lead mid-level
shortwave. Initial moisture within this wave is predominately
elevated (surface Td only rise a few degrees into the low 60s)
likely leading to a mixture of virga and scattered light showers
through the evening given the antecedent dry airmass below 10kft.
Better heavier rain chances look to arrive late tonight into early
Saturday tied the arrival a secondary, stronger shortwave over the
central Great Lakes. By this point, resident dry airmass is expected
to be absent owing to saturation from the first wave. Additionally,
this secondary wave is more favorably timed to tap into the richer
theta-e plume lifting up along the Mississippi supporting dewpoints
behind its attendant warm front pushing through the mid 60s into the
upper 60s by Saturday AM. Overall result is widespread showers with
a few embedded thunderstorms possible as weak elevated instability
creeps in from the south.

Morning rain pushes out of the area by late morning/midday with SE
MI residing within the overall system`s warm sector. Moisture
transport into the region only continues through the day as the
northern edge of the aforementioned Mississippi theta-e plume
reaches southern MI pushing dewpoints into the lower 70s. Model
trends have been more bullish on available instability late
afternoon-evening with mlcapes ranging between 1000-1500 J/kg for
most areas with around 2000 J/kg along the Ohio border to southern
Metro Detroit. With the mid/upper trough transiting overhead, 0-6km
bulk shear values range from 35-45kts offering good potential
organization on any updrafts that manage to develop either along the
cold front that will be advancing southeast out of the the northern
Great Lakes or bubbling up deeper within the warm sector if leftover
stability from morning activity is an insufficient cap- best area
for this looking to be near Lake Erie/stateline. Best window for
convection, including strong to severe storms, is between roughly 20-
02Z. Main threats with these storms would be damaging wind gusts
given Dcape values near 1000 J/kg and low-level lapse rates
exceeding 7 C/km, as well as locally heavy rainfall as PW values
hang around 2 inches. While mid-level lapse rates do leave a bit to
be desired in the 6 C/km range, ample instability and shear will
provide a secondary threat for hail in the strongest updrafts.

Cold front clears the region by early Saturday night ushering in a
significantly cooler, drier airmass with 850mb temps falling to 7-8C
and dewpoints back in the low 50s to upper 40s. Much below normal
highs looking more likely for Sunday even with sunnier skies with
temps struggling to break in the lower 70s. Canadian high pressure
drifts overhead into the beginning of next work week maintaining
this cooler, but pleasant pattern.

MARINE...

High pressure moves off to the east bringing southerly flow of 10-15
knots. Pressure gradient will tighten throughout the day and
increase wind speeds up to 20 knots gusting to 25 over northern Lake
Huron. The next low pressure center moves into the area on Saturday
and brings chances for showers and storms. Winds veer to the north-
northwest on Sunday behind the cold front, maintaining speeds over
20 knots around the nearshore areas of the Thumb and over central
Lake Huron. Due to fetch direction and length, the potential for
waves to meet Small Craft Criteria exists on Sunday.

&&

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

$$

AVIATION.....CB
DISCUSSION...KDK
MARINE.......BC


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.