NWS Forecast Discussion
FXUS63 KDTX 250357
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EDT Sun May 24 2020
Remnants of a surface trough/weak front stalled over southern Lower
Michigan during the evening and resulted in a notable gradient in
surface dewpoint toward central Lower. The boundary moves back north
during the late night with little fanfare other than some patches of
VFR ceiling around 5000 ft. The warm and humid air mass produces a
few hours of MVFR fog around sunrise which quickly dissipates by mid
morning. Dry conditions then continue until mid afternoon when
scattered showers and thunderstorms are again possible. A diffuse
wave aloft promotes a favorable uncapped thermal profile during peak
heating, however lake breeze convergence zones are about the only
surface features available to focus convection. Storms really can`t
be ruled out anywhere across SE Michigan but the lake breeze
presence adds some confidence for the DTW corridor up to PTK. The
mid to late afternoon Prob group remains the best forecast approach
for now until instability decreases again Monday evening.
For DTW... VFR clear continues for a few more hours before high
clouds increase coverage toward sunrise. These clouds are not
expected to disrupt formation of MVFR fog in the warm and humid air
mass across the region. It dissipates quickly by mid morning with
dry conditions until a chance of thunderstorms mid to late
DTW THRESHOLD PROBABILITIES...
* Moderate for ceiling 5000 ft or less this afternoon.
* Low for thunderstorms this afternoon.
Issued at 307 PM EDT Sun May 24 2020
An increasingly mixed low level southwest flow now entrenched
locally. This process effectively drying the boundary layer as a
weak surface trough/wind shift axis transits southeastern sections.
Recent radar trends do show a few weak returns now over portions of
Lenawee/Washtenaw counties, suggesting a limited window thru 21z for
development downstream, but with prospects of greater convective
expansion/vigor likely compromised by a warm/stable mid level
profile. Otherwise, a benign evening ahead, simply characterized as
humid within a gradually fading diurnal cu field. The elevated near
surface moisture content does give pause for possible fog
development overnight under increasing low to mid level ridging.
Model signal here remains mixed, with a dewpoint depression that
perhaps remains just high enough to keep the response very
shallow/minimal. Lows tonight upper 50s to mid 60s.
A gradual northwest expansion of higher upper heights into southeast
Michigan will commence through the early week period. The resident
above average thermal profile will respond accordingly, applying an
additional upward trend in temperatures across a deep layer. This
translates into widespread highs of mid to upper 80s both Monday and
Tuesday, with the elevated dewpoints netting heat indices near 90.
The inherent capped mid level environment continues to cast
uncertainty on convective chances through this period. Greatest
potential on Memorial Day likely tied to the northward pace and
track of a weak wave now noted on water vapor lifting across
southern IL. Recent model guidance does suggest some form of this
energy and/or associated convection that emerges upstream may
attempt to ease into lower Michigan during the daylight period.
Forecast will continue to highlight a generic low end chance mention
targeting main peak heating window through this period. Lack of
meaningful wind magnitude throughout the column minimizes severe
potential, primarily offering some brief heavy downpours should a
few multi-cell clusters ultimately materialize.
Gradual height falls will commence from the northwest with time
through the midweek period, this process easing an attendant frontal
zone across the lower peninsula. Conditions likely unchanged through
the Wednesday period, as upper ridging remains a fixture for all but
perhaps far northern sections. An improving overall forcing field in
combination with gradually lower mid level temperatures as upper
heights drop will offer greater potential for convective development
- particularly Thursday. Given the underlying moist/unstable
environment, a slowly advancing frontal slope parallel to the mean
flow could bring a stripe of heavier rainfall depending on the
southward pace of the front. Upper trough projected to swing through
Friday will effectively nudge this boundary south, leaving a drier
and more seasonable environment in place heading into next weekend.
Prolonged southwest winds through Thursday, as upper level ridge and
surface high sets up along the East Coast. With the warm airmass,
near lake stability will be high, limiting mixing and holding winds
under 20 knots. Typical summer-like unstable airmass will promote a
chance of showers and thunderstorms from time to time through
Wednesday, before a cold front arrives Thursday, bringing widespread
showers and thunderstorms which could last into Friday morning
before the front clears the Central Great Lakes and winds shift to
Lake Huron...Dense Fog Advisory until noon EDT Monday for LHZ361-362.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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NWS DTX Office Area Forecast Discussion