316
FXUS63 KDTX 180729
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
329 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.

&&

.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 northenr 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.

&&

.PREV DISCUSSION...
Issued at 1157 PM EDT Mon Jun 17 2024

AVIATION...

Thunderstorms finished their evening run leading up to midnight
leaving just a stray shower or rumble of thunder possible during the
late night. There is little else of concern outside of convective
trends under VFR clear to scattered sky condition until a brief
period of fog or haze becomes possible with wet ground now combined
with the already humid air mass. A couple of hours of MVFR
restriction is likely around sunrise even with a 5 to 10 kt wind.
The afternoon then brings more of the same hot, humid, and unstable
conditions along with another pattern of showers and thunderstorms
having even greater organization. Given larger scale mid level
support moving in from the MS/TN valleys, mid afternoon storm
initiation is likely with similar timing across the terminal
corridor which then moves eastward toward Tuesday evening.

For DTW/D21 Convection... A stray shower or rumble of thunder remain
possible late tonight as warm and humid air is now rooted across
Lower MI. A morning pause in convection is expected followed by
another round of storms in the afternoon, likely with greater
coverage across the bulk of D21.

DTW THRESHOLD PROBABILITIES...

* Moderate for thunderstorms mid to late afternoon into Tuesday
  evening.

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


&&

.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.
&&

$$

DISCUSSION...SC
MARINE.......SF
HYDROLOGY....SC
AVIATION.....BT


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