Expert Forecast Opinion

067
FXUS63 KDTX 301903
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
303 PM EDT Wed Apr 30 2025

.KEY MESSAGES...

- Periodic showers and some embedded thunderstorms will track across the
area late tonight through Thursday. The potential exists for an
isolated strong to severe thunderstorm to develop during the late
afternoon and evening hours.

- A lower chance for showers will exist on Friday.

- Cooler conditions develop Saturday.

&&

.DISCUSSION...

Existing low-mid level ridging encapsulating the region late this
afternoon will maintain influence through the evening hours,
ensuring deep layer dryness holds within low level easterly flow.
Noted increase in high based cloud during this time, as the initial
stages of the moistening process commences within a broader pattern
of mid level warm/moist advection emerging downstream of the
southern plains mid level wave set to eject across the region on
Thursday. Increasing magnitude of the advective process under
sustained moist isentropic ascent within strengthening mid level
southwest flow will bring a high probability of showers starting
late tonight and continuing into early Thursday. Sufficient
reduction of stability atop of the low level stable layer will
maintain some embedded elevated thunderstorm potential, affording
some brief heavier downpours.

Surface warm front clears the area mid afternoon (outside of the
Saginaw valley), providing a limited window for very modest boundary
layer destabilization ahead of the trailing cold front through the
evening hours. This process governed primarily by improving low
level moisture quality as dewpoints climb above 60 degrees.
Temperature recovery likely to remain much more restricted, owing to
lingering cloud concerns within this narrow time frame. Highs
targeted to peak around 70 degrees. This will contain prospective
MLCAPE to perhaps 500-700 j/kg at most, with a portion of the
solution space offering little if any. Background environment does
feature a strong unidirectional deep layer wind field, so a more
organized cell or two could emerge 20z-00z should greater
instability develop and establish deeper updrafts.

Northern stream shortwave energy noted on water vapor ejecting
southeast out of northwest Canada will consolidate just upstream
over the next 48 hours. This will establish a broader longwave
trough with greater dynamics fixated within the base as height falls
intersect favorable upper jet dynamics. Initial period of height
falls set to arrive locally Friday into Friday night. General trend
across the model solution space toward potentially more unsettled
conditions this period, owing to the possibility for a more
organized window of deeper forced ascent to materialize. Modest
upward adjustment made to precipitation chances, with further
refinement likely as confidence in placement and magnitude of
governing ascent become more defined. Temperatures to end the week
parked near average - highs low to mid 60s.

Broad region of high pressure establishes greater influence for the
weekend period. This occurs as ongoing large scale height falls to
the south detach from the mean flow and support the development of a
cutoff closed low over the southern Ohio valley. Lingering potential
for shower development may carry into early Saturday, but otherwise
a dry and stable pattern locally this period within a generally cool
north/east low level flow south of the high. Behavior of the upper
low then dictates conditions heading into early next week. Any
northward wobble of the broad, cyclonic periphery will increase
potential for unsettled conditions to return.

&&

.MARINE...

High pressure continues to drift across the central Great Lakes
through tonight maintaining tranquil marine conditions. The next low
then lifts out of the mid-Mississippi River Valley towards lower MI
early Thursday. Its attendant warm front lifts through the southern
half to 2/3rds of the region Thursday morning supporting widespread
showers and a return to southwest 10-15kt flow for areas south of
the front- winds stay east-northeast and slightly stronger closer to
15-20kts for areas north. A few thunderstorms are possible Thursday
evening-early night mainly from central Lake Huron-south where the
warmer, more unstable air resides. An isolated strong storm also is
possible focused towards Lake Erie. Low peels away late Thursday
night dragging a cold front across the region setting up cooler west
to northwest winds though these winds aren`t expected to get above
20kts as the gradient rapidly weakens. A secondary cold front is
drawn south through the area daytime Friday however with the still
relatively weak gradient and high pressure on its heels, no
appreciable increases to wind strengths are anticipated as more
uniform north-northwest flow is established.

&&

.HYDROLOGY...

Periodic showers with a few embedded thunderstorms will accompany a
low pressure system into region late tonight and Thursday. Chance of
rain will continue through early Thursday night, as a trailing cold
front moves through. Forecast rainfall totals are trending downward,
with a broad area of 0.25" to 0.50" amounts expected for areas
generally south and east of a Flint to Sandusky line. Higher amounts
upwards of 0.75" to 1.25" remain possible northwest of this line,
particularly within localized areas that see thunderstorms. Highly
localized flooding in low-lying and/or flood prone locations will be
possible in these locations.

&&

.PREV DISCUSSION...
Issued at 103 PM EDT Wed Apr 30 2025

AVIATION...

High pressure moves east from the Great Lakes while reaching back to
maintain control of conditions over SE Mi for the rest of today and
this evening. A lake breeze augmented easterly wind is the weather
highlight in the otherwise benign pattern of increasing high clouds.
The high clouds are the first sign of the next low pressure system
organizing across the southern and central Plains which brings
steadily lower conditions into SE Mi late tonight through Thursday.
VFR is expected to hold through much of the night as the initial
round of showers struggle to overcome low level dry air over the
region. This is followed by the primary moisture surge toward sunrise
as the surface low reaches northern IL and the warm front moves
toward the southern Mi border. Showers become widespread across the
area during Thursday morning but have greater intensity north of PTK
with a rumble of thunder possible. Ceiling drops into MVFR and then
IFR as the surface low and warm front move across southern Lower Mi.

For DTW... VFR continues under increasing high clouds this afternoon
and evening and then drops below 5000 ft late tonight. Showers
increase coverage from the south late tonight with a rumble of
thunder possible Thursday morning.

DTW THRESHOLD PROBABILITIES...

* High for ceiling at or below 5000 feet after 09Z Thursday.

* Low for thunder after 12Z Thursday.


&&

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

$$

DISCUSSION...MR
MARINE.......KDK
HYDROLOGY....MR
AVIATION.....BT

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