225
FXUS63 KDTX 150743
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
343 AM EDT Mon Jul 15 2024

.KEY MESSAGES...

* An active period of thunderstorms occurs this morning and again
  Monday night into Tuesday morning as another thunderstorm complex
  tracks into the Great Lakes from Wisconsin.

* Isolated damaging wind gusts, large hail, and localized flooding
  are possible with any thunderstorms this morning and Monday night.
  Storm motion is west to east at 40 mph for both events.

* A break in thunderstorm activity this afternoon allows
  temperatures to rise toward highs near 90 with maximum heat index
  in the mid 90s.

* A slow moving cold front keeps showers and thunderstorms in the
  forecast for Tuesday, especially as potential for strong to severe
  thunderstorms and flooding rainfall linger Tuesday morning.

* There is a chance of showers Wednesday in a much more benign
  pattern.

* High pressure brings cooler and less humid weather into the region
  for the late week period.

&&

.DISCUSSION...

Storms ongoing across Lower MI are on the lead flank of a mature MCV
reinforced by the convective system that originated in southern WI
last evening. That MCS is now tracking along the larger scale
instability gradient into northern IN after grazing SW Lower MI. The
parent MCV over Lower MI is enhancing backed flow out ahead of the
center in support of a pseudo elevated warm front and the resulting
eastward extension of storms. The enhanced wind profile is also
shown to beef up effective bulk shear into the 30-40kt range in
hourly mesoanalysis while MUCAPE holds in the 1000-2000 J/kg range.
DCAPE of 1000-1500 J/kg combined with sub 1000 J/kg surface based
CAPE are used in this case as a sign there is at least some wind
gust access to the surface vs a stronger inversion for any storms
with greater organization. Elevated instability is also adequate for
hail approaching 1 inch while the leading banded structure makes
flooding an increasing component of hazards (see Hydrology section)
until the parent MCV exits into Ontario by noon.

Subsidence trailing in the wake of the morning MCV bolsters
predictability on a dry forecast for this afternoon. Early exit of
the system allows a cloud decrease and temperature recovery post
morning rain cooled boundary layer conditions. Afternoon high
temperatures make a run toward 90 combined with Td around 70 for max
heat index in the mid to upper 90s, below Heat Advisory threshold
but still oppressive for a few hours late this afternoon.

The hot and humid air in place sets the stage for the next
convective system on schedule for tonight. Consensus of 00Z hi-res
and regional model solutions point to another post midnight event
for SE MI. Surface based storms are projected to initiate along a
stronger cold front moving into the upper Midwest this afternoon
which then grow upscale again into a mature MCS across Lower MI
tonight. Damaging wind is the primary hazard for severe intensity
storms in SE MI, however heavy rainfall and flooding show increasing
potential. The cold front follows closely behind the convective
system Monday night but stalls overhead Tuesday morning as larger
scale mid level height falls occur over the northern Plains and
upper Midwest. A combination of storm outflow and the larger scale
cold front could become the focus for new storm development on the
heels of the MCS as an extension of nocturnal/low level jet forcing
through Tuesday morning.

The cold front finally exits into Ontario and Ohio by Tuesday night
followed by a chance of showers as the mid level trough swings
through the Great Lakes Tuesday night and Wednesday. It is a much
more benign setup compared to recent days as cooler and less humid
air fuel standard intensity showers with low end rainfall amounts. A
broad area of surface high pressure follows with a high
predictability pattern of dry weather for the late week period.

&&

.MARINE...

An unsettled pattern is in-place to start the workweek with storms
inbound from a MCS that originated over the Upper Mississippi Valley
last evening. Locally higher winds/waves and some hail are possible
this morning before the convective activity dissipates/departs into
southern Ontario. The afternoon hours look to be rather quiet and
quasi-stable before a secondary wave combines with an influx of low-
level moisture which helps sustain another organized line of
nocturnal storms. Once again, hazardous marine conditions will be
driven by the evolution and intensity of storms as they cross the
local waterways. A cold front slides into the region Tuesday with
some low-end potential for surface convergence and convective
redevelopment before the front clears through and brings about an
airmass change. Dry and cool air driven by strong ridging over the
Upper Midwest then offer more favorable boating conditions. A
longwave trough over Canada descends on the region Wednesday with
modest NNW flow and a few showers followed by thermal troughing
Thursday.

&&

.HYDROLOGY...

An active pattern of thunderstorms this morning and again Monday
night and Tuesday morning present a risk for flooding across SE
Michigan. Numerous thunderstorms this morning are capable of brief 1
inch per hour rainfall rate. Totals in the 1 to 2 inch range are
possible with locally higher amounts where multiple storms track
over the same location. A break in activity is anticipated this
afternoon and evening until another round of thunderstorms moves in
late Monday night into Tuesday morning. This system will be capable
of similar rainfall rates and totals added on to what occurs this
morning. Roads, urban locations, and other flood prone areas will be
most vulnerable to this heavy rainfall along with rivers that are
already elevated from heavy rainfall last week. Stay updated on the
latest forecasts as new information helps identify specific areas of
flooding concern around southeast Michigan.

&&

.PREV DISCUSSION...
Issued at 1203 AM EDT Mon Jul 15 2024

AVIATION...

The apex of the MCS is moving over Chicago into southwest IN early
tonight with the northern extension of this complex likely to move
through southwest lower Michigan. Latest model guidance continues to
show portions of this system lasting into southeast Michigan, but in
a much more weakened state as environmental conditions are less
favorable for MCS maintenance with further eastward extent. Showers
and thunderstorms with the MCV on northern end of the complex will
move through by around 08Z with showers and thunderstorms further
weakening post sunrise. After convection comes to an end, lower VFR
to possible MVFR clouds should linger into the afternoon with a
period of dry conditions. Mixing depths by early tomorrow afternoon
bring potential for gusts up to 20 knots.

For DTW/D21 Convection...A thunderstorm complex has developed
upstream across WI and IL this evening and will move across Lower
Michigan through the early morning hours. Showers and thunderstorms
should be able to make it into southeast Michigan, but in a
weakening state. Moderate confidence exists in thunderstorm arrival
to D21 airspace by around 08Z with activity lasting through about
12-13Z. Strong wind gusts will be the main threat.

DTW THRESHOLD PROBABILITIES...

* Medium for thunderstorms early this morning.

* Medium for ceilings aob 5,000 feet mid/late morning and afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.

&&

$$

DISCUSSION...BT
MARINE.......KGK
HYDROLOGY....BT
AVIATION.....AA


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at www.weather.gov/detroit.