568
FXUS63 KDTX 081926
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
326 PM EDT Mon Jul 8 2024

.KEY MESSAGES...

- Isolated to widely scattered showers and thunderstorms from Flint
to Saginaw/Thumb this evening before shifting south into the rest of
the region tonight.

- Remnants of Beryl begin to impact Southeast Michigan Tuesday
afternoon. Moderate to heavy rain continues through the day
Wednesday before it finally departs daytime Thursday. Some flooding
is possible dependent on where heaviest rain sets up.

- A prolonged period of above average temperatures is expected to
start this weekend and continue into early next week.

&&

.DISCUSSION...

Diffuse frontal boundary continues sag into southern lower MI this
evening with associated weak low level convergence resulting in
scattered showers/storms being confined to the Flint/Saginaw
Valley/Thumb areas. The parent mid-level trough skirts the region
during this time as it tracks over northern lower MI leading to
increasing deeper layer shear, pushing into the 30kt range, offering
potential for a stronger storm or two. Limiting factor for this
outcome however remains the weak convergence along the boundary as
well as very modest available instability with latest CAMs
struggling to generate more than 500-700J/kg of MLCAPE. Scattered
rain chances eventually expand southward across the rest of the
region tonight as the boundary pushes further southeast supported by
a compact mid-level shortwave riding along it out of the Midwest
into the southern Great Lakes. Additionally, this wave brings with
it a portion of higher theta-e airmass that is just to our south
maintaining some weak elevated instability to support thunder
chances throughout the overnight period. Latest model runs are more
bullish on frontal progression with most now advertising this front
clearing east of the Metro Detroit area by late morning offering a
brief end to precip chances before the arrival of the lead edge of
Beryl remnants latter half of Tuesday.

Focus remains on what would then be Tropical Depression Beryl as it
lifts into the Ohio Valley/Great Lakes for the midweek period.
Confidence in this system reaching SE MI, rather than taking a more
common deflected easterly track to our south, is increasing with the
12Z runs continuing to show its the center tracking somewhere between
northern OH and the central portion of the CWA (ie I-69). This is
resultant from a faster system speed lending to a delayed
interaction with the northern stream shortwave until Wednesday,
which is keeping a more westerly track in play (this is especially
apparent between the 00Z and new 12Z Euro). This faster arrival
leads to the initial deformation arm reaching the southern portions
of the area by Tuesday afternoon. Core of tropical moisture then
arrives overhead by Tuesday night with PWATs exceeding 2" as the
main precip shield likewise overspreads the region with a prolonged
period of moderate, to at times heavy, rain persisting throughout
the day Wednesday. Another consequence in the later wave
interaction, is a slowing of Beryl as it pushes east/northeast
likely resulting in a slower departure with the northwest
deformation axis lingering over the area, particularly the Thumb,
through at least the first half of the day Thursday. In terms of
potential amounts, some uncertainty remains due to the westerly
trend in track which is making the axis of heaviest rainfall a
moving target. That said, an average 1-3" looks likely over all of
SE MI from Tuesday afternoon to Thursday morning, with the highest
amounts in that range favored south of I-69 currently. Locally
higher amounts (near or above 4") are possible dependent on any
mesoscale rain banding, though spatial predictability of these
features is very low this far out.

Upper troughing follows to close out the work week keeping
temperatures slightly below average in the upper 70s to lower 80s.
Upper flow eventually trends more zonal by this weekend allowing a
hotter, humid airmass confined over the Plains to partially spill
east into the Great Lakes. Highs during this timeframe likely reach
the upper 80s with some 90s being possible especially by early next
week.

&&

.MARINE...

Southerly wind around 10 knots in place today, allowing for warm
moist air to be advected in. This setup brings chances for scattered
showers and storms tonight, mainly over northern Lake Huron. Shower
chances will continue overnight into early Tuesday morning for
southern Lake Huron, Lake St. Clair, and Western Lake Erie. Cold
front will pass over the area Tuesday veering winds to the north.
Wind speeds will remain around 10 knots, with gusts to 15-20 knots.
Remnants of Beryl are then set to move in and bring heavy rain to
the area Wednesday and Thursday. The center of the low pressure is
forecasted to move overtop the CWA or Lake Erie Wednesday evening.
Northeast flow will remain in place over Lake Huron, with wind
speeds persisting at 10-15 knots gusting to 20. High winds
associated with this system are not a concern at this time.

&&

.HYDROLOGY...

The remnants of Beryl will move into the area between a strong ridge
of high pressure over the southeast CONUS and a re-expanding upper
level wave positioned just to the west. This system will begin to
impact the Great Lakes Tuesday afternoon with the remnant low
pressure center then tracking over/near the area through Wednesday
night into early Thursday morning. Track still carries some
uncertainty with a slight westward shift noted in latest model runs,
though its center tracking somewhere between I-69 and northern Ohio
looks most favored at this time. On average, 1 to 3 inches of
rainfall looks likely over all of SE MI in this scenario between
Tuesday afternoon to Thursday morning. Highest amounts in this range
most favored south of I-69 currently. Locally higher totals, pushing
or exceeding 4 inches, will be possible however the exact location
of this carries low predictability.

Flooding concerns would be likely with amounts of this magnitude
with a Flood Watch likely in a coming forecast update when a bit
more certainty in track/heavy rain positioning comes into picture.

&&

.PREV DISCUSSION...
Issued at 103 PM EDT Mon Jul 8 2024

AVIATION...

A stationary front will remain draped across Southeast Michigan
through Tuesday. Isolated showers and thunderstorms will be possible
along this boundary throughout the forecast period. The greatest
likelihood for activity this afternoon and evening will be at MBS
and FNT. The focus for new development will shift south overnight
into Tuesday across the Detroit airspace. Coverage will be very
limited in time and space through midday Tuesday.

For DTW/D21 Convection...Thunderstorms are not expected across the
airspace this afternoon and evening. A very low potential exists
overnight through the daylight hours of Tuesday (peaking at a 20
percent chance - Tuesday midday).

DTW THRESHOLD PROBABILITIES...

* Low for ceilings at or below 5kft tonight and Tuesday.
* Low for thunderstorms overnight and Tuesday.


&&

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

$$

DISCUSSION...KDK
MARINE.......BC
HYDROLOGY....KDK
AVIATION.....Mann


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