597
FXUS63 KDTX 021808
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
208 PM EDT Thu May 2 2024

.KEY MESSAGES...

- Above normal temperatures continue through the next 7+ days.

- Showers and a few thunderstorms expected tonight with greater
  coverage and intensity Friday afternoon, although severe
  thunderstorms are not expected at this time.

- Low confidence forecast in place through the weekend regarding
  additional showers, then clearing high pressure arrives Sunday
  night into Monday.

- A large low pressure system lifts into the High Plains Tuesday
  and Wednesday lending renewed storm chances, locally.

&&

.AVIATION...

VFR conditions will persist throughout the afternoon and evening
hours with an amplifying ridge overhead and anticyclonic
trajectories. Any lake breeze response will remain muted with a
prevailing southeast wind direction this afternoon already in
advance of the mesoscale forcing. A deep potential vorticity lobe
will pivot across northern Minnesota this evening and tonight
driving a narrowing axis meridional moisture transport across
Southeast Michigan Friday. Precipitation chances begin to increase
after 09Z Friday as southern stream/mississippi River Valley
moisture does lift northward and streamlines immediately in advance
of the northern tier trough. Two specific time windows of concern at
the Detroit terminals, a quick chance for elevated shower activity
between 09-11Z and the potential for some shower/tstorms developing
along a weak cold front Friday afternoon. Confidence in coverage and
occurrence is lower Friday afternoon and did account by a Prob30.

For DTW/D21 Convection...Shower activity is expected to lift
northward out of northern Ohio between 09-11Z Friday with a low
potential for thunderstorms. Additional shower activity with
thunderstorms will develop over portions of Southeast Michigan after
19Z. Low confidence in occurrence at Metro as activity could remain
north and west. Strong to severe thunderstorms are not anticipated
Friday.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms tonight and Friday

&&

.PREV DISCUSSION...
Issued at 424 AM EDT Thu May 2 2024

DISCUSSION...

Morning MSAS MSLP data shows a broadening region of high pressure
across the Upper Midwest while GOES vapor imagery reveals a well
formed circulation along the central Ontario/Quebec border. Lower
Michigan will remain positioned between these two systems, at least
through the morning hours. Given the more diffuse pressure gradient,
weaker winds eventually veer toward the northeast, before taking on
a southeasterly trajectory this afternoon as the ridge migrates
northeastward and breaks down. Today`s flow scheme offers more
seasonable conditions attributed to the advection of cooler lake-
modified air. The coldest readings will be found immediately
downwind of the shorelines where temperatures peak in the 60s. Highs
moderate in the low-mid 70F range across the rest of the forecast
area with southwest extent.

Inbound shortwave troughing tilts negatively and tracks into the
Upper Midwest today with an active LLJ. Latest NWP solutions have
fallen into better agreement regarding dry PoPs for most of
Southeast Michigan during the daylight period. More formidable
ambient dryness provided by the neighboring anticyclonic gyre is now
reflected in forecast soundings, marked by a higher temperature
through the warm nose preceding the surface front and better column
uniformity of dry southwest flow. PWATs continue to trend lower as a
result. Local probabilistic data lends confidence that any showers
that could develop prior to 00Z should remain along the western
fringe of the forecast area. Did adjust PoPs to restrict Slight
Chance mentions west of US-23. Should note that the 02.12Z FV3 and
02.04Z HRRR are the two CAM outliers since both suggest showers
developing earlier and surviving past the demarcated PoP boundary.
Chance for showers and some sub-severe storms increases from west to
east overnight. Lack of instability limits the coverage of any
stronger storms.

Showers will be on-going Friday morning as dewpoints creep up with
the arrival of the surface warm front arrives. There are still
points of uncertainty wrt the triple point location midday which
affects coverage and strength of convective activity. Regardless,
about 250-750 J/kg of MLCAPE should build as the cold/occluded front
works in with some indications of a brief window for SBCAPE
development. This would mainly induce a more robust flare-up during
the afternoon/evening period, but a weakening trend in shear
parameters limit severity. In spite of cloud cover, temperatures
should still top out in the upper 70s for most areas. Most of the
convective activity should depart into Ontario by midnight, but low-
level omega signal indicates some lingering ascent and shower
activity with moist easterly feed.

Low level moisture remains trapped beneath an inversion with weak
gradient wind Saturday. This supports continued stratus and some
sprinkles with perturbed mid-level flow. The abnormal warmth
persists through the weekend while an upper level trough approaches
Sunday warranting continued low-end PoPs. This pushes a cold front
into the region before it stalls just south of the state line Sunday
night. High pressure quickly crosses the Great Lakes Monday offering
the first truly dry day before the low tracks into the High Plains
Tuesday and Wednesday. The aforementioned front then lifts northward
as a warm front lending renewed rain/storm chances midweek with
little evidence of any significant cool-down.

MARINE...

Modest wind speed from the northwest expected through early today as
high pressure builds into the region. Winds establish an easterly
component late today as the high exits the region. A low pressure
system is forecast to track across the northern great lakes Friday.
This will draw a cold front through lower Michigan, bringing
increasing potential for showers and thunderstorms particularly
during the afternoon and evening hours. Winds holding from the
southeast at less than 20 knots in advance of this front Friday.

HYDROLOGY...

Scattered showers and thunderstorms arrive tonight with varying
degrees of coverage through Friday. A cold front moves through Lower
Michigan Friday afternoon/evening which may produce a few robust
thunderstorms containing heavier downpours. Some areas could see in
excess of a half inch of rainfall by Friday night. No major flood
concerns are expected at this time.

&&

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

$$

AVIATION.....CB
DISCUSSION...KGK
MARINE.......MR
HYDROLOGY....KGK


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