998
FXUS63 KDTX 140749
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
349 AM EDT Fri Jun 14 2024

.KEY MESSAGES...

- Mainly dry today with just a few isolated thunderstorms possible
  this afternoon.

- Seasonable temperatures are expected today and Saturday before much
  warmer conditions take hold for most of next week.

- Temperatures climb into the mid to upper 90s Monday through
  Wednesday with max daily heat indices breaking 100F for many areas.

&&

.DISCUSSION...

Southeast Michigan resides within the basal portion of a longwave
trough today while the synoptic pattern is expected to amplify with
time. The upstream ridge axis approaches the 60N latitude mark (near
Northwest Territories, Canada) while a weak mid-level shortwave
perturbation works through the composite trough digging into the
central Great Lakes. This offers a period of minor height falls,
locally, and northerly flow trajectories as a cold frontal boundary
moves through. H8 temps decrease throughout the day, into the single
digit range (Celsius), bringing relief from the previous day`s heat
with modest cumulus response once a deep mixed-layer develops to
above 7 kft AGL.

Steep low-level lapse rates with cooler thermodynamic profiles lend
a period of surface-based instability with afternoon CAPE values
near 300 J/kg and 50+ knots of 0-6 km bulk shear. However, the
convective response still ought to be rather muted given the lack of
meaningful ThetaE advection. Forecast soundings reveal an inhibiting
magnitude of dryness through the boundary-layer with evidence of
weak capping near 12 kft AGL. Overall, did make adjustments to PoPs
to account for isolated shower/storm development via broad-brushed
Slight Chance mentions as the main arc of CVA passes through aloft
after 16z. Should any storms develop, severe weather is not expected,
but overachieving gusts pose the primary conditional threat given
the enhancements to negative buoyancy through strong evaporative
cooling potential. Highs track closer to climatological normals today
(upper 70s to around 80F) while clear skies emerge overnight helping
readings drop into the 50s.

The inflection point in the synoptic pattern crosses Lower Michigan
Saturday morning resulting in column stabilization through active
subsidence. A shift to anticyclonically curved trajectories causes
low-level winds to veer ENE drawing in cooler Canadian air across
Lake Huron. With no precip concerns and highs generally in the 70s
(outside Metro Detroit), conditions Saturday will likely be the most
comfortable through at least the next week in advance of a
significant heatwave. 500 mb ridge marked by a geopotential height
center of 593 dam situates over northern Georgia Sunday. Local flow
shifts southwesterly with time while a ridge-running shortwave
feature cruises through the Great Lakes. Discrepancies exist within
the NWP model space wrt to the magnitude of associated rainfall, but
variance is rather low regarding the placement. Most of the activity
should remain north of M-46 Sunday evening with the GFS being the
outlier given its southern footprint. Sunday also marks the
initiation of the big heat wave next week as daytime highs top out in
the upper 80s along/west of I-75 (cooler numbers further east).

The anomalously potent ridge for mid June builds north as mean
column thickness values increase. Medium range solutions highlight
areas of H8 temps in excess of 22C by 18Z Monday which aligns with
the 99th percentile per the NAEFS and GEFS. Highs are now forecast
to climb into the upper 90s for most urbanized locations while
outlying areas easily peak in the mid 90s. In spite of a light breeze
around 10 mph and afternoon dewpoints mixing out to the mid 60s,
heat indices likely break 100F for several hours Monday afternoon.
Heat Advisories or Excessive Heat Watches/Warnings will probably be
needed in some form next week since the ridge only strengthens as the
week progresses (albeit with eastward translation). 500 mb heights
climb to 597 dam over Appalachia Tuesday before migrating northeast
over Manhattan/Long Island where the heat dome maximizes at
approximately 600 dam. EPS/CMCE/GEFS are all on-board with highs
soundly in the 90s through Thursday with the only chance for relief
dependent on the track/timing of any (remnant) MCS activity rolling
in off The Plains. Isolated diurnal thunderstorm activity may also
crop up across the CWA given MUCAPEs regularly in excess of 2000
J/kg. Overnight lows should also be quite warm starting Monday
night, remaining above 70F each night.

&&

.MARINE...

A warm air mass continues to reside over the cooler waters,
producing stable over-lake conditions. This will continue to
minimize the stronger wind gusts mixing down to the surface,
relative to the over-land nearshore zones. That said, isolated wind
gusts around 25 knots will still be possible immediately along the
land-lake interface with the southwest flow in place, especially
into inner Saginaw Bay with the ideal fetch. These stronger wind
gusts will diminish after sunset.

Otherwise, redeveloping showers and thunderstorms, some strong, will
be possible this evening, focused mainly across central Lake Huron
and locations south. Northern Lake Huron will still be susceptible
to storms, some strong, through the late afternoon.  Wind gusts to
or in excess of 34 knots and small hail will be the main threats
with any strong to severe thunderstorm development. The passage of a
cold front late tonight into tomorrow morning will veer wind
direction from southwest to northwest as high pressure builds in
behind the front. This will bring lighter winds to the Great Lakes
by tomorrow morning, lasting into the end of the week.

&&

.PREV DISCUSSION...
Issued at 1157 PM EDT Thu Jun 13 2024

AVIATION...

The hybrid cold front/outflow boundary is settling through central
Lower MI at forecast issuance. The boundary focuses clusters of
showers and thunderstorms supported by the broad mid level trough
covering the upper Midwest and Great Lakes. A stray thunderstorm
lingers through the late night mainly east of the terminal corridor
across the Thumb region. The surface front/boundary then continues
moving north to south across the area with questions still raised on
the scope of any low cloud coverage. Late evening observations
support model projections that still have clouds developing overhead
rather than moving in with the boundary. Other than a short period
of MVFR ceiling, timing the wind shift may be the weather highlight
until early in the morning. Inbound high pressure and associated
northerly boundary layer wind bring low level dry air into the
region through the afternoon while another mid level wave carries in
mid to high level clouds. Any ceiling is well above 5000 ft late in
the day into Friday evening.

For DTW/D21 Convection... Isolated thunderstorms are possible toward
the northern reach of D21 but not at DTW late tonight. Dry weather
is expected late tonight through Friday evening.

 DTW THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less late tonight and early in the
  morning.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

DISCUSSION...KGK
MARINE.......AM
AVIATION.....BT


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