283
FXUS63 KDTX 181007
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
607 AM EDT Tue Jun 18 2024

.KEY MESSAGES...

- Hot and humid conditions will persist across most of the area
through the week.

- Chances of thunderstorms will continue each day of the week. Some
of these storms may be strong to severe with locally heavy
downpours.

&&

.AVIATION...

Airmass recovery gets underway this morning after a stormy evening.
Where marginally MVFR fog develops, visibilities should improve
before or shortly after the 12Z TAF issuance. Diurnal cumulus
response expected with high based VFR clouds AOA 5 kft AGL this
afternoon before convection initiates within an unstable/uncapped
airmass. Coverage of storms carries uncertainty with the better CVA
along the edge of the ridge forces storm development further north
(FNT/MBS), but the denser instability reservoir and lake breeze
interactions will have greater influence over the Metro Detroit
terminals. Given those considerations, kept the inherited TEMPO
groups for TSRA with MVFR visibility reductions. Winds generally
remain AOB 10 knots with southerly flow, but strong gusty winds and
microburst potential exists with the deepest convective storms.
Storms are expected to diminish quickly around 00Z this evening.

For DTW/D21 Convection...Another round of storms expected this
afternoon with potential for wet microbursts should stronger storms
develop over/near D21 airspace. Coverage will be scattered in nature.

DTW THRESHOLD PROBABILITIES...

* Moderate for thunderstorms from 19 to 23Z.

* Moderate for ceiling at or below 5000 ft, conditional with
  thunderstorms.

&&

.PREV DISCUSSION...
Issued at 329 AM EDT Tue Jun 18 2024

DISCUSSION...

Amplification of the East Coast mid level ridge will be ongoing
today into Wednesday, with the ridge becoming more elongated as it
stretches across the Ohio Valley during the end of the week. Short
wave energy rotating along the western periphery of this ridge will
advance across western Lower Mi today. Hi res model solutions
generally suggest this will set up a thermal/instability gradient
across the western portions of the forecast area this afternoon.
This and potential lake breeze convergence zones across the eastern
portions of the area will provide enhanced boundary layer
convergence to support additional rounds of convection, mainly this
afternoon and evening. ML Cape values projected near 2k J/kg with
model soundings showing respectable CAPE density within an uncapped
environment will again be supportive of localized strong/severe
convection despite relatively week deep layer shear profiles. The
depth of the warm layer, with PWATs around 1.8 inches will support
some locally high rain totals as well.

Expectations are for temps to be a little cooler today compared to
yesterday given high clouds and the chances for an earlier
convective release. Forecast highs in the low 90s with dewpoints
near 70 will still push heat indices well into the 90s. The humidity
will sustain another warm night tonight as lows will likely hold in
the 70s. Some building/expansion of the mid level ridge across the
eastern lakes will sustain heat and humidity across Se Mi Wednesday.
Timing and coverage of convective development within a moderately
unstable and uncapped atmosphere will play heavily into forecast
highs. Thermal profiles suggest low to mid 90s for highs Wed with
heat indices well into the 90s to around 100. The potential for ML
CAPE values to exceed 2k J/kg with little to no capping inversion
will again support locally strong/severe convection.

A little more elongation in the mid level ridge noted in the 00Z
model suite increases the chances for a southward push of slightly
cooler air from the north on Thursday as high pressure expands
across the northern lakes. Short wave impulses embedded within the
westerly flow with a lingering instability gradient over southern
Lower Mi also looks favorable for additional convection. Therefore,
the heat headlines will extend only through Wednesday evening. A
longer wavelength trough forecast in the northern stream over the
weekend will attempt to drive the front back northward as a warm
front. The potential for convection will however support a low
confidence forecast on temps during the first half of the weekend.
The passage of the mid level trough and associated cold front will
then support cooler and less humid conditions by the end of the
forecast.

MARINE...

Southwest winds will continue to advect hot and humid air into the
Central Great Lakes through the mid week period. High degree of
surface stability with the cooler waters should keep wind speeds
under 25 knots through the rest of the work week. The exception will
be in and near and strong thunderstorms which develop. Timing and
location will be highly uncertain, but the typical peak heating of
the day into early evening hours will be favored. Indications are
the surface frontal boundary will be sinking south Thursday and
Friday as seasonably strong high pressure tracks through Ontario.
This will allow for light northeast/northerly flow (~15 knots) over
Lake Huron. Airmass will remain warm, thus any wave build up with
the longer fetch remains below 4 feet.

HYDROLOGY...

A moist and unstable airmass will be in place across the region
through the end of the week. Scattered thunderstorms are expected
each day this week. The most intense thunderstorms have the
potential to produce rainfall amounts in excess of 2 inches over a
short period of time, resulting in urban and low lying area
flooding. Uncertainty in specifics for both timing and potential for
flooding precludes issuance of a flood watch.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory until 8 PM EDT Thursday for MIZ048-049-054-055-062-
     063.

     Excessive Heat Warning until 8 PM EDT Friday for MIZ061-069-070-076.

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

$$

AVIATION.....KGK
DISCUSSION...SC
MARINE.......SF
HYDROLOGY....SC


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