Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 291852
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
252 PM EDT SUN MAY 29 2016
Convection has been developing this afternoon along a prefrontal
trough axis, extending from the cntrl thumb region down to
Jackson/Hillsdale counties as of 19Z. A special 18Z DTX sounding
showed fairly steep lapse rates, particularly in the low levels.
Moisture however was quite lean. This resulted in mixed layer CAPE
of less than 500 j/kg on the 18Z sounding. The agitated cu field
along this prefrontal trough axis and deepening convection
suggests a little better moisture pooling along this boundary.
This trough axis will push east across the area through 21 or 22Z
and will be the main focus for convection. The actual sfc cold
front will trail the frontal trough a couple hours, but will
likely just provide an isolated shower/thunderstorm at best given
the drying boundary layer following the prefrontal trough. The
steep lapse rates and deep layer of dry mid level air will make
hail a concern with any storm this afternoon and will also support
the potential for strong convective downdrafts, providing a chance
for strong wind gusts.
Post frontal cold air advection tonight will be rather weak as the
remnant mid level trough rapidly dampens as it lifts northeast of
Lake Superior. The post frontal cloud cover across Wisconsin this
afternoon has a large diurnal component, which will diminish during
the course of the evening. So skies will undergo a clearing trend
across Se Mi during the night. Despite this, the w-nw gradient will
suppress nocturnal cooling enough to hold nighttime mins in the 60s.
Daytime mixing depths will compensate for the slightly cooler low
level airmass on Memorial Day and will support afternoon highs into
the low, possibly mid, 80s. Sfc dewpoints will be down in the 50s,
so humidity levels will be much lower in comparison to the last
several days. Model soundings suggest a sct to bkn afternoon cu
field. Building mid level heights during the afternoon will suppress
afternoon convective cloud depths and will hinder anything other
than perhaps a brief sprinkle or isolated light shower.
Mid level heights will continue to build across the Great Lakes Mon
night into Tuesday in reponse to a deepening upper low rotating into
the Dakotas. This will support strengthening high pressure across
the nrn and ern Great Lakes, maintaining dry conditions through at
least Tues night. The orientation of the sfc high will result in
light e-ne winds across the forecast area on Tuesday. So while
inland locations should push 80 for Tues aftn highs, locals near the
lakes will be cooler. This will be more notable near Lake Huron
where the lake modified air will keep temps several degrees cooler
than those farther inland.
Tuesdays high pressure should hold through most of Wednesday with
only a slight chance of showers or thunderstorm development.
Although temperatures will remain in the 80s over much of SE
Michigan...humidity on Wednesday is expected to remain in the
comfort zone. As developing low over the plains continues to migrate
toward the Great Lakes...a broad/moist southwesterly flow will ensue
along with increasing chances of showers/thunderstorms Wednesday
night through Thursday. Cold front pushes through on Friday leaving
cooler temperatures in its wake. High temperatures in the 70s Friday
and continuing through the weekend.
A trough axis, preceding the main cold front this afternoon will
sustain scattered thunderstorms across southern Lake Huron and Lakes
St Clair and Erie, some of which may be strong. Farther north, the
better chances for showers and thunderstorms will be in the evening
with the passage of a cold front. The front will be rather weak and
will only result in a gradual veering of the wind field toward the
west by Monday morning. The post frontal gradient will be rather
weak by Monday, so winds across the lakes will remain relatively
light and variable. High pressure will strengthen across the eastern
Great Lakes on Tuesday and will support east-northeast winds on the
lakes. The northeast winds may become gusty as they are funneled
down Saginaw Bay. A stronger cold front is forecast to cross the
region Wednesday night into Thursday, providing the next chance for
thunderstorms as likely resulting in some periods of increased
Issued at 140 PM EDT Sun May 29 2016
An approaching cold front will be a focusing mechanism for showers
and thunderstorms this afternoon. CU field has developed in advance
of the front over western and central lower Michigan but has been
restricted further east due to lingering cirrus thus far. The front
will swing through this afternoon and exit into Ontario by this
evening. Though hires models mostly agree there will be some
convection along the front, none are too keen on widespread develop
as shallow moisture and low level cap appear to keep storms in
check. None the less, with storms in and around southeast MI,
included a three hour window of VCTS for all sites. Some stronger
storms may become severe with strong winds and large hail. Best
chance for storms appears to be north of PTK in the thumb,but all
sites have some risk of seeing a storm or two. Afternoon winds will
gust to around 20 knots with deep diurnal mixing and will once again
drop off around sunset. After the front passes, drier air will try
to clear the skies tonight through Monday.
FOR DTW...Showers and thunderstorms are just beginning to initiate
over central lower Michigan so it will be a few hours before
reaching the terminal. Best window for possible activity will be
from about 20-23Z. Should see mostly VFR conditions outside of any
cells that track near the terminal. Skies will try to clear out
overnight as drier air advects in behind the front.
//DTW Threshold Probabilities...
* Low for ceilings at or below 5000 FT outside of thunderstorm
* Low for thunderstorms affecting DTW/D21 airspace today.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
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