Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
FXUS63 KDTX 172349
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
749 PM EDT MON OCT 17 2016
A firm south-southwest wind will mark conditions through the
overnight period, as gradient flow continues to strengthen. While
mixing potential will be capped to some degree of nocturnal
stability, there will be an increasing gust component by the early
morning hours on Tuesday. Gusts will reach into the 25 to 30 knot
range. Outside of some lingering stratus across MBS, skies are
expected remain mostly clear into the early morning. Clouds then
thickening into a lower VFR /CIGS 3500 to 5000 ft/ in advance of a
cold front for mid-late morning. Very limited potential for showers
with this frontal passage, on track to move across the region
Tuesday afternoon. Both wind speed and gustiness will diminish as
winds shift to westerly with the frontal passage.
For DTW...Mostly clear skies across the lowest 5000 ft into the
early morning. Inbound ceilings below 5000 ft now over Wisconsin
expected to enter the airspace after 10z. South-southwest winds
expected to strengthen overnight, with increasing gust frequency.
Gusts into the 25 to 30 knot range during the morning period.
//DTW Threshold Probabilities...
* Medium for ceiling 5000 feet or less after 10z.
Issued at 339 PM EDT Mon OCT 17 2016
Record setting warm and moist October airmass in place across
southeast Michigan based off upper air climatology, as 12z dtx
sounding indicated 14 C dew pt at 850 mb, with Green Bay checking in
at 16 C. Fortunately, warm air in the mid levels (temperatures
reaching 10 C at 700 mb) is moving into southern Lower Michigan
late this afternoon/this evening as upper level ridge builds over
Central Great Lakes, which will provide a nice cap through
Tonight. Exception being toward Tri-Cities region, closest to the
rapidly deepening cyclone lifting through the U.P. and departing
warm front. Another mild night (65 to 70 degrees) as strong low
level jet will be in place, with enough turbulence/mixing to
maintain surface winds in excess of 10 knots, and probably closer
to 20 knots later tonight.
Low level convergence/shallow frontal circulation with cold front
tomorrow may be able to generate some showers, but pronounced
dry slot at 700 mb (20 to 30 C dew pt depressions) should help limit
coverage. On flip side, NAM soundings indicating solid cape density
centered around 5 KFT, and thus any showers will be taping into some
very strong wind fields (50+ knots), and wind gusts in excess of 45
mph are possible if any convective showers do infact develop.
With the warm start to the day and residual warm airmass in place
(15 C at 850 MB/19 at 925 MB), still possible DTW could sneak in 80
degrees in if the front is a bit slower, otherwise mid to upper 70s
across the cwa as low level cold advection takes hold during the
Western Confluent upper level flow allowing surface high to build
into Southern Lower Michigan Tuesday Night, and could see some fog
development if surface dew pts hold in the 50s, as airmass still
looks to be on the warm side with 1000-500 mb thicknesses in the
558-564 dam range.
Any morning fog around, coupled with surface high (1019 mb)
lingering through the day will limit mixing depths, along with some
high clouds arriving from the southwest, holding maxes at or below 70
degrees, but still well above normal (upper 50s/lower 60s).
On Thursday, medium-range progs suggest the upper trough transiting
the central CONUS will become negatively tilted somewhere around the
Great Lakes/Ohio Valley. Surface low will develop along the SW/NE
oriented baroclinic zone, with precipitation along the cold side of
the boundary and within the right entrance region of a strong upper
jet. ECMWF and CMC are showing a classic track for widespread
precipitation over Southeast Michigan, while the GFS continues to
develop further east. However, significantly more GEFS members result
in precip than at this time yesterday, lending more confidence to a
wetter solution, especially for the southeast half of the forecast
area where likely PoPs are in the forecast. In the wake of this
system, the thermal trough will be over the region, likely resulting
in below-normal temperatures Friday and Saturday, but likely with
mainly dry weather. Likely a bit warmer by Sunday.
Low pressure over Iowa will move toward Lake Superior and deepen
considerably during the night. This will cause southwest wind to
strengthen accordingly and pull unusually warm air northward over
Lake Huron and lower Michigan. The warmth is expected to be adequate
for a profile stable enough to prevent frequent gale force wind
gusts over the open waters of Lake Huron. Stability is more in
question near the shoreline and over land areas and this will be
monitored for trends that support an upgrade to a short-fused gale
warning. Saginaw Bay would be the most suspect area depending on how
wind gust trends develop upstream over central lower Michigan during
the evening, and even farther upstream over Lake Michigan. Small
Craft Advisories are in effect for all marine areas for gusts
otherwise expected to reach 25-30 knots.
Confidence is higher that gales will be reached over northern Lake
Huron once the associated cold front sweeps through toward sunrise.
Colder air moving over the open waters will help produce the
unstable conditions needed for frequent gusts in the 35-40 knot
range. The gale watch has been upgraded to a warning for that area
through mid Tuesday afternoon. Westerly wind will continue into
Tuesday night but weaken considerably as high pressure builds into
the southern Great Lakes and holds through Wednesday.
Lake Huron...Small Craft Advisory until 4 PM EDT Tuesday FOR LHZ421-422-441>443.
Gale Warning from 6 AM to 4 PM EDT Tuesday FOR LHZ361-362.
Lake St Clair...Small Craft Advisory until 4 PM EDT Tuesday FOR LCZ460.
Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EDT Tuesday FOR LEZ444.
You can obtain your latest National Weather Service forecasts online