225
FXUS63 KDTX 102005
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
405 PM EDT Wed Jul 10 2024

.KEY MESSAGES...

- The Flood Watch and Flood Advisories are trimmed to now include
  just the area from the I69 corridor into the Thumb region for this
  evening.

- Rain diminishes to scattered light showers after midnight into
  Thursday morning.

- Scattered showers and thunderstorms redevelop during the afternoon
  both Thursday and Friday.

- A period of above average temperatures begins this weekend into
  early next week.

&&

.DISCUSSION...

Mid afternoon observations and model analysis fields indicate near
surface based convection in the Detroit metro area has exited into
Ontario with the surface low remains of Beryl. That leaves the bulk
of deformation forcing to occur across the Thumb region for the
remainder of this event. Radar derived rainfall estimates and
surface reports show the heaviest rain has fallen along and west of
a line from Ann Arbor to Pontiac to Lapeer, including the Flint
metro area where cumulative rainfall from yesterday and today has
led to pockets of residential flooding. The Tri Cities and Thumb
regions meanwhile have been largely spared from excessive rainfall
with reports generally less than 1 inch since midnight. Model
consensus QPF that is now primarily east of the Tri Cities allows
cancellation of the Flood Watch there while continuing for the Thumb
region for up to 1 inch of additional rainfall through 8 PM.

Northerly wind gusting in the 30 mph range is the first sign of the
surface low associated with Beryl exiting into Ontario during late
afternoon and this evening. The other is showers gradually
diminishing around the western fringe of the system`s moisture field
while surface based convection holds across northern and western
Lower MI. Beryl moisture strips away later tonight, especially after
midnight, leaving just low clouds in place despite northerly wind
bringing in a cooler and less humid air mass into Thursday morning.

A smaller scale mid level circulation over the Midwest this
afternoon has northern stream origins from central Canada. It is
unrelated to Beryl but follows closely behind across the Great Lakes
during Thursday until nearly stalling overhead Thursday night into
Friday. This system has a cold core scattered convective appearance
in observations today which projects well to hold into Lower MI
Thursday afternoon and evening. Peak daytime instability generates
surface based CAPE across Lower MI but is projected to remain below
1000 J/kg in the 12Z HREF run, in line with the general thunder
convective outlook. Storm intensity diminishes to showers Thursday
evening and then coverage becomes isolated after midnight under the
lingering mid level circulation. Trends in today`s 12Z model package
slows the exit of this system into Friday afternoon requiring at
least an isolated shower/storm mention in the forecast.

Global/extended model runs offer mostly zonal solutions on the
larger scale mid to upper level flow pattern this weekend. The zonal
flow keeps predictability on the low side for shower/storm activity
but with a steady warming trend indicated in the data through
Sunday.

&&

.MARINE...

Post-Tropical Cyclone Beryl (or the remnants thereof) stream through
the central Great Lakes this evening fueling additional gusty
showers as the low tracks across the Ontario Peninsula. An uptick in
gradient wind is underway given the vicinity of the low pressure
center and strengthening of the surface pressure gradient.
Expectation for evening winds features a backing trend with time
while gustiness increases due to slightly steeper low-level lapse
rates augmented by the approach of a strong cyclonic lower column
wind field. Latest observations suggest additional isolated gusts to
gales may persist across portions of the Lake Huron nearshores, but
the general infrequency precludes an upgrade to Gale Warnings. Gusts
to around 30 knots will be more representative of prevailing
conditions through the evening hours. Further south, gradient winds
veer toward the northwest across Lake St. Clair and Lake Erie
producing Small Craft Advisory winds this evening, therefore the
current headlines will remain in effect. Winds decrease steadily
late tonight and into Thursday with northwest flow becoming weaker
and westerly by the afternoon hours. High pressure attempts to build
into the region Thursday and Friday while weak troughing may produce
some additional showers. Winds/waves hold below criteria through
Saturday and probably through the weekend time-frame.

&&

.PREV DISCUSSION...
Issued at 144 PM EDT Wed Jul 10 2024

AVIATION...

Beryl remnants are continuing to track through the region today
bringing heavy rainfall. MVFR cigs are in place across the CWA, with
showers dropping cigs and visibilities to IFR conditions. Northerly
winds of 20 knots gusting to 30 also remain in place this afternoon.
Winds will back to become more northeasterly through the evening
hours and overnight and begin to drop off in strength as the low
pressure center moves out. MVFR ceilings are set to remain in place
overnight until sunrise tomorrow. Guidance remains muddled on the
post-storm environment tomorrow in terms of clouds. Models are split
as some show viability for a broken MVFR deck while others trend
instead towards a high cloud deck. Have included both in the TAFs
for now but expecting guidance to resolve the situation within the
next couple of cycles to provide a more coherent answer.

For DTW/D21 Convection... Lightning has not been observed in the
showers associated with this system, and it is expected to remain
that way through the evening. Strong cloud cover has significantly
limited instability available for storms to develop further.
However, a stray storm or rumble of thunder is still a possibility,
and trends will be monitored and updates will be provided if
anything more significant does materialize.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms today and this evening.

* High for ceiling aob 5kft today and tonight.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...Flood Watch until 8 PM EDT this evening for MIZ047>049-053>055-
     060>063-068>070-075-076.

     Beach Hazards Statement until 10 PM EDT this evening for MIZ049-055-
     063.

Lake Huron...Small Craft Advisory until 10 AM EDT Thursday for LHZ421-422.

     Small Craft Advisory until 4 PM EDT Thursday for LHZ441>443.

Lake St Clair...Small Craft Advisory until 10 AM EDT Thursday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT Thursday for LEZ444.

&&

$$

DISCUSSION...BT
MARINE.......KGK
AVIATION.....BC


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at www.weather.gov/detroit.