NWS Forecast Discussion

FXUS63 KDTX 271103

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 AM EDT Sun May 27 2018


Main aviation concern for the TAF period will be ongoing MVFR/IFR
fog at TAF onset, which should dissipate 13-14z. Cluster of
thunderstorms over central Lower Michigan could brush KMBS with
showers/brief thunder before exiting 13z-14z. For the remainder of
the day, increasing low/midlevel heights, fairly strong capping
inversion around 700 hPa, and deep LFC heights will limit
thunderstorm potential today despite ample surface moisture and
instability. The exception may be terrain-based convection that forms
in northern lower Michigan this afternoon, potentially drifting
southward into KMBS, where VCTS is carried after 18z. Strong
low/midlevel heating should limit any widespread cloud cover, but
patchy diurnal cumulus will still be possible. Light and variable
flow will become south/southwest 5-10 knots.

For DTW...MVFR/IFR fog continues through 13-14z, otherwise VFR.
Thunderstorm potential limited further north with capping inversion
around 700 hPa limiting convective potential.


* None.


Issued at 353 AM EDT Sun May 27 2018


A mid summer air mass is firmly in place over SE Michigan judging by
surface dewpoint in the lower to mid 60s across the area. This along
with clear sky and light wind is resulting in areas of fog and
patchy dense fog to start the morning that will quickly burn off
during early morning. Plentiful morning sun also helps lift
temperatures quickly into 80s on the way to highs in the upper 80s
near the shorelines to lower 90s interior. The records listed below
are easily in reach at FNT and DTW but more of a challenge at MBS,
especially if late afternoon cumulus and isolated convection develop
as advertised. The plan is to still hold off on headlines for heat
but continue cautionary information in DSS messaging. Surface
dewpoint projections hold in the mid 60s which prevents heat index
from exceeding the temperature by more than a couple degrees and also
allows min temps to settle back into the 60s tonight.

Early morning radar composite indicates clusters of convection over
northern Lower Michigan, on the southern flank of the short wave
moving through Lake Superior and northern Ontario. This feature is
producing some slightly enhanced nocturnal moisture transport which
could brush the Tri Cities and Saginaw Bay before sunrise. After
that, model soundings agree on a mixed layer building to at least
800 mb. This is a high based LFC that explains why many of the CAMs
produce isolated convection during late afternoon. The timing and
location fits in nicely with the inherited entry level chance POP
from the Tri Cities across the Thumb region where lake breeze
focusing will be possible. The area is also a landing zone for any
development off the higher terrain of northern Lower Michigan under
neutral NW flow aloft that is not quite able to completely cap off
the mid levels. The neutral upper level height pattern leads to a
wider range of CAPE forecasts among the models due to variations in
mid level lapse rate. Lower end values of MLCAPE around 1000 J/kg
and MUCAPE around 1500 J/kg are preferred with the expectation that
convection will not be completely capped off but warmer air aloft
will be a limiting factor. Isolated storms would then be capable of
high LFC/precip loaded downburst wind and locally heavy rainfall
through about mid evening.

Warm and humid conditions tonight will lead to another round of near
record high temperatures for Memorial Day. Temperatures will be
enhanced by the bubble of warmer air around 850 mb brought in by the
upper ridge as it builds from the central Plains into the southern
Great Lakes. Model soundings and 850 mb temperature projections
around 20C offer a little more confidence on a capping inversion
established closer to the ridge axis. Highs in the lower 90s look
solid to wrap up the holiday weekend.

There has been model agreement on a weak cold front backing into
Lower Michigan Monday night and Tuesday which remains in this
forecast cycle. The front is associated with a wave moving well
north of the area through northern Ontario and Quebec but which
ushers in a surge of high pressure and easterly flow during Tuesday.
The boundary will be dry with the possible exception of some
convective remnants Monday night and the following high pressure
will bring some cooler air into the region, especially in the Tri
Cities and Thumb region due to onshore flow. The high struggles to
hold off remnants of Alberto which are shown in long range models
moving rapidly into the Great Lakes during Wednesday.


Light southerly flow will continue into today as an area of weak low
pressure and attendant frontal boundary draped across the central
Great Lakes washes out. Higher pressure will then begin to build
into the region from the Ohio Valley into Memorial Day. Favorable
boating conditions will occur the remainder of the holiday weekend
with the exception of widely scattered thunderstorms this afternoon
and Monday afternoon/evening, mainly across central Lake Huron and
Saginaw Bay. Boating conditions will then begin to deteriorate
heading into the midweek period as the remnants of Subtropical Storm
Alberto move into the region.


Here is a list of record high temperatures for
this holiday weekend.

Today, May 27th:

Detroit                91 (set in 1941)
Flint                  90 (set in 1987)
Saginaw/Tri-Cities     94 (set in 1911)

Monday, May 28th:

Detroit                95 (set in 2012)
Flint                  93 (set in 2012)
Saginaw/Tri-Cities     92 (set in 1977)



Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.




You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.

NWS DTX Office Area Forecast Discussion