124
FXUS63 KDTX 130157
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
957 PM EDT Wed Jun 12 2024

.KEY MESSAGES...

- Warming trend continues through mid-week with high temperatures
  nearing 90 degrees for Thursday.

- Scattered showers and thunderstorms also arrive Thursday. Strong
  to severe storms will be possible during the afternoon and evening
  with damaging winds and large hail the main threats. Southeast MI
  is outlined in a Marginal to Slight Risk from SPC.

- Higher than usual confidence in hot and humid conditions next week.
  Temperatures into the 90s Monday and Tuesday with relatively high
  humidity will likely bring the highest heat indices we have seen so
  far this year.

&&

.UPDATE...

Upstream observational trends this evening suggest the forecast is
in good shape calling for a chance of showers and possibly a rumble
of thunder late tonight and in the morning. The WI/IL convection has
weakened but the parent MCV remains with respectable strength while
set to track across Lower MI. The wave has some representation at
500 mb across the spatial range of model data and appears capable of
strengthening the low level jet with a corresponding increase in
elevated moisture transport and instability late tonight. This
forcing has potential for scattered shower production in its own
right out ahead of any remnant surface based activity approaching
from the upper Midwest. Consensus of hi-res model data carries the
bulk of the upstream storms across Upper Mi and northern Lower MI
along the instability axis. The latest runs of the RAP and NAM also
maintain a couple line segments of convection this far south toward
sunrise. This will be monitored as MUCAPE drops to sub 1000 J/kg
from west to east into SE MI, however lapse rate in the 700-500 mb
layer builds into the 6-7 C/km range toward sunrise, sufficient for
late developing elevated/nocturnal convection. The most favored area
is north of I-69 and mainly within a few hours of sunrise. Activity
dissipates while exiting eastward mid to late morning allowing ample
opportunity for recovery of instability for the anticipated afternoon
round of storms.

&&

.PREV DISCUSSION...
Issued at 713 PM EDT Wed Jun 12 2024

AVIATION...

The late developing but energetic VFR cumulus response across SE MI
will gradually fade in favor of thickening high based convective
debris this evening. A greater component of mid level clouds then
develops after midnight, still VFR, as remnants of ongoing WI/IL and
later MN/WI storms move toward Lower MI. A few of the storm remnants
could survive into the MBS area late tonight, and additional showers
may also develop overhead late tonight and early into the morning,
mainly north of FNT as mid level moisture increases over the central
Great Lakes. VFR mid and high clouds with a stray shower continue
through the morning leading to reloading thunderstorm potential
Thursday afternoon, mainly after 20Z at MBS, spreading southeast
toward DTW during late afternoon.

For DTW/D21 Convection... An approaching low pressure system and
cold front bring a chance of thunderstorms later Thursday afternoon.
There remains a focus of coverage over IL/IN with the northern
fringe brushing DTW after 22Z.

 DTW THRESHOLD PROBABILITIES...

* Moderate for thunderstorms impacting the terminal after 22z
  Thursday.

PREV DISCUSSION...
Issued at 320 PM EDT Wed Jun 12 2024

DISCUSSION...

Clear skies have pushed temperatures into the 80s this afternoon
ahead of the approaching cold front and associated storms moving in
tomorrow. Hi-Res guidance resolves two different chances for rain on
Thursday. The first round comes through early Thursday morning,
beginning as early as 4am. This threat for storms is focused mainly
in the Thumb, where there is potential for the storms to tap in to
some MUCAPE of up to 500 J/kg. By the time the rain moves in, shear
looks to be scarce and a diurnal temperature inversion will be in
place. Currently not expecting any severe storms to develop,
although an occasional rumble of thunder is possible.

The second round on Thursday boasts a greater potential for storms
to develop, but there is still much uncertainty on how everything
will play out. Later in the day Thursday a shortwave trough moves
overtop Michigan, allowing for a bit more divergence aloft than
earlier in the day. That said however, the left exit region of the
trough remains to the northeast, meaning that speaking dynamically,
the best region for storm development is still not quite lined up
with the CWA. Thermodynamics tell a similar story for a different
reason, with the better CAPE and moisture environment staying to the
southwest. ThetaE values range 10-20K greater to the southwest of
Lake Michigan, allowing for the possibility that storms may grow in
the direction of greater moisture rather than developing over
southeast Michigan. MUCAPE values over Michigan reach 1500 J/kg at
their peak, so updrafts still have the possibility to develop with
some help from the cold front. Hodographs look decent for the
development of supercells with the potential to produce hail, and
DCAPE values over 1000 J/kg signify the potential for severe wind
gusts. An isolated tornado can also not be ruled out at this time.
The cold front then passes over Michigan early Friday morning,
ending the severe storms chances.

High pressure takes control behind the front, bringing clear skies
Friday and Saturday along with slightly cooler, more seasonal
temperatures. The next chance for showers comes Sunday evening, when
a shortwave embedded within the development of an upper level ridge
brings some rain to the Great Lakes area. The timing and extent of
these showers is still uncertain, and depends on how the ridge
develops over the weekend.

Confidence continues to stay high on a significant warmup next week.
An upper level high settles in over the Southeast United States on
Sunday creating the aforementioned ridge overtop of the CWA. 500mb
heights have the potential to hit 590dam at peak, allowing for
temperatures 10-15 degrees above climatological normals. Flow is set
up in such a way that will allow for warm, moist mT air from the
Gulf of Mexico to fill in to the Great Lakes, bringing dew points up
into the 70s. Forecasted temperatures currently sit only a few
degrees shy of record highs across the area, and has the potential
to hit record highs if full insolation can be achieved. Ensemble
guidance shows only a handful of runs failing to hit 90 degrees on
Monday, with apparent temperatures reaching into the mid-to upper
90s. The same factors remain in place on Tuesday, with temperatures
and apparent temperatures once again reaching the low 90s and upper
90s respectively. Overnight temperatures stay in the 70s, offering
little relief from the hear. As such, the NWS Heat Risk product
identifies a Major Risk (Level 3/4) of heat related impacts on
Monday and Tuesday, with local pockets of Extreme Risk (Level 4/4)
on Tuesday. Showers are possible for the duration of the event
riding up the trough to the west into the Great Lakes region, which
could provide some brief relief from the heat. Still, much remains
to be resolved on the extent and timing of any rainfall.

A slight though not insignificant cooling trend has developed for
Wednesday. Previous runs looked to maintain the ridge through the
middle of next week, but now look to move it off to the east on
Wednesday. Zonal flow is set to take over, but temperatures will
remain above normal through the rest of the week.

MARINE...

Extremely stable over-lake conditions persist through the remainder
of the day which will promote light winds leading into tomorrow.
Upstream convection west of Lake Michigan will eventually cross the
lake and enter, first over northern Lake Huron, which will bring the
chance for showers and thunderstorms. Coverage and intensity of
activity is expected to wane overnight as it crosses both lakes, but
isolated to scattered coverage cannot be ruled out through southern
Lake Huron into late tomorrow morning. Southwest flow will become
reinforced over the lake through the day tomorrow, veering more
northwesterly late tomorrow night into Friday morning. Gusts 20-25
knots will be possible immediately along the nearshore zones,
especially through Saginaw Bay with the better fetch, however, have
precluded the issuance of any Small Craft Advisories at this time
given how stable the over-lake conditions continue to be. The stable
marine layer should keep the stronger winds aloft as they flow off
the land. Will consider a Small Craft Advisory for the Saginaw Bay
tomorrow afternoon and evening if modeled guidance suggests higher
probabilities of achieving sporadic gusts aoa 22 knots. Wave heights
reach right around the 3 ft mark for the Bay. A cold front and high
pressure builds in on Friday, promoting lighter winds speeds.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

UPDATE.......BT
AVIATION.....BT
DISCUSSION...BC
MARINE.......AM


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