439
FXUS63 KDTX 171757
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
157 PM EDT Mon Jun 17 2024

.KEY MESSAGES...

- Heat and humidity will affect the area through the week. Excessive
heat warnings and heat advisories are in effect.

- There will be periodic chances for thunderstorms throughout the
week.

&&

.AVIATION...

VFR conditions will prevail the much of this TAF period with daytime
heating and the increased moisture supporting a cumulus field at
around 6kft this afternoon. There remains potential for
afternoon/early evening isolated/scattered thunderstorm development
supported mainly by the diurnal instability. The overall uncertainty
and anticipated pop up nature of activity will preclude mention in
TAFs at this time, but may require an amendment if confidence
increases for any terminal to be affected. Low VFR to possible MVFR
conditions would be possible with any heavier shower/thunderstorm.
Winds will be out of the southwest through this afternoon while deep
mixing is yielding gusts to around 20 knots. Winds back towards the
south for tonight before veering back towards the southwest tomorrow.

For DTW/D21 Convection... There remains a chance for isolated to
scattered showers and thunderstorms to develop this afternoon.
Confidence is not high enough that any D21 terminal will be
impacted, so will not include a tempo group at this time. The favored
time frame for activity is towards 22-00Z. Will continue to monitor
and amend if needed.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms this afternoon and evening.

* Low for ceiling at or below 5000 ft, conditional with convective
  development.

&&

.PREV DISCUSSION...
Issued at 341 AM EDT Mon Jun 17 2024

DISCUSSION...

A compact mid level MCV will traverse Se Mi during the early morning
hours. This wave has been responsible for clusters of strong to
severe convection upstream, with the more robust convective response
occuring closer to the sfc warm front. The passage of this wave and
influx of deep layer moisture and elevated instability will sustain
some degree of convection across Se Mi this morning, particularly
across the southern portions of the forecast area. Elevated
instability will be advecting into Se Mi from the west during the
course of the early morning, which may be enough support isolated
strong to marginally severe convection.

Some building of the mid level height field in the wake of this
mornings MCV will allow respectable diurnal heating to occur. High
temps upstream yesterday were in the lower to mid 90s, which look
reasonable across Se Mi this afternoon. Diurnal mixing will likely
hold sfc dewpoints in the 60s this afternoon which will cap heat
indices in the mid to upper 90s. Forecast soundings across Se Mi
this afternoon/evening are uncapped. Late day convective development
can therefore not be ruled out, especially considering lingering sfc
boundaries expected across Se Mi.

A building mid level ridge across the East Coast over the next
couple days will be responsible for the heat across the southern
lakes. Models have been very consistent showing 500mb heights rising
to 598-600dm as the mid level high becomes centered over the Mid
Atlantic Wednesday into Thursday, while the ridge axis builds
westward across the Ohio Valley and eastern Great Lakes. Thermal
profiles (with 850mb temps of +19 to +21C) across southern Michigan
will be supportive of high temps into the 90s.

There does remain considerable uncertainty as to the timing and
strength of numerous short wave impulses that will be circulating
around the large mid level ridge, especially Tuesday and Wednesday.
These short waves are likely to impact portions or all of Se Mi at
times and will continue to support a chance of showers and
thunderstorms. Moderate to possibly high instability with a little
bit of mid level flow along the northwestern side of the ridge will
support a chance for a few strong to severe storms both Tuesday and
Wednesday. Timing/coverage however remains highly uncertain. Medium
range model ensemble members show increasing spread in the Friday to
Sunday time frame with respect to the breakdown of the mid level
ridge across the Great Lakes resulting from northern stream energy.
This and the increasing potential for convection to bleed into
portions of Se Mi lead to some degree of uncertainty as to temps
late week into next weekend.

The excessive heat watch was issued due to multiple consecutive days
of hot weather as opposed to just one day of possibly breaking a
heat index of 100. This is due to the fact that heat stress worsens
with number of consecutive hot days. Per coordination with
surrounding offices, the heat watch is being replaced with a long
fused head advisory. The exception to this is the urban Detroit and
Flint areas (Wayne, Oakland, Macomb, Genesee Counties) where a
warning is being issued given the more adverse affects of heat on
these urban areas.

MARINE...

A warm and humid airmass will hold over the Great Lakes through the
week, which will support relatively stable near surface lake
conditions. The earlier passage of a warm front has reinforced south
to southwest flow, which will hold through at least the early week
period. Otherwise, there will be a couple of chances for showers and
thunderstorms today. The first through this morning, pending the
evolution of an upstream storm complex, with renewed chances
possible later this afternoon and evening. Additional development is
possible tomorrow, but this is more favored over land or along the
nearshore. Localized stronger wind speeds and gusts around 20 to 25
knots will be possible through the Saginaw Bay into central Lake
Huron with the favorable southwest fetch tomorrow.

HYDROLOGY...

A moist and unstable airmass will be in place across the region
through Tuesday. This will bring the potential of a few rounds of
showers and thunderstorms this morning through at least Wednesday.
Locations which experience strong thunderstorms will have the
potential for rainfall amounts to exceed 2 inches in a short period
of time, leading to urban/low lying flooding. There is too much
uncertainty both the timing and potential for localized heavy
flooding to issue any type of flood watch products at this time.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory until 8 PM EDT Friday for MIZ047>049-053>055-060-062-
     063-068-075-082-083.

     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.....AA
DISCUSSION...SC
MARINE.......AM
HYDROLOGY....SC


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