Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 172307
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
707 PM EDT Tue Oct 17 2017

.AVIATION...

SE Michigan remains in between surface high pressure over the Ohio
Valley and a track of low pressure systems through far northern
Ontario, north of Lake Superior. The primary aviation impact will be
continued moderate southwest wind between the systems tonight
through Wednesday. Boundary layer decoupling will allow the
gustiness to subside tonight but is expected to return by late
Wednesday morning. Gusts near 25 knots will once again be likely
through Wednesday afternoon. Conditions will otherwise be VFR in
varying coverage of high clouds.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 329 PM EDT Tue Oct 17 2017

DISCUSSION...

Wind gusts of 20 to 30 mph and overachieving temperatures this
afternoon are a nod to uninhibited insolation and efficient boundary
layer growth. Gusts briefly exceeded 35 mph at KMBS courtesy of
modest downsloping within SW flow. Forecast highs for this aftn were
raised to the upper 60s away from the glacial ridge, but have
already reached 70 in many locations by 19z. Grids for the remainder
of the evening have been updated accordingly.

Vigorous wave is noted on IR coming onshore near Seattle this
afternoon. In response, lee cyclogenesis is underway in the prairie
of AB/SK. This cyclone will track across south-central Canada
through Wednesday, lifting toward James Bay by Wednesday night and
ensuring a stout southwest gradient through tomorrow. Mixed
conditions will contain lows to the 40s tonight while 850mb temps
rise from 8C readings early today to 11C on Wed. Conditions
otherwise unchanged, so the forecast is modified persistence - went
warmer than all available guidance for highs - about 2 degrees
warmer than today, or low 70s.

Orphaned cold front attendant to the James Bay low will ease through
the area Wed night into early Thurs. Continued tranquil weather
through this time as paltry moisture along the front leads to
nothing more than a low coverage of aftn cu on Thurs. Highs once
again mid to upper 60s.

Surface and upper level ridging will be in place over the Great
Lakes Friday and Saturday, thanks to Pacific energy digging an
amplified trough over the western CONUS. This will lead to continued
mostly sunny skies Friday and temperatures warming well above
average into the lower 70s both days. Clouds will begin to move in
Saturday as a shortwave lifts through.

Long range model guidance diverges on the timing of the upper trough
impacting the Great Lakes: the GFS brings the next chance of rain on
Sunday afternoon, while the ECMWF brings this moisture to the region
early Monday. Will continue to monitor in the coming days as to
exact timing of this disturbance moving through, but regardless of
timing, a cool and showery start to next week is expected as this
trough is forecast to deepen and linger over the Great Lakes through
at least mid week.

MARINE...

A pressure gradient between surface high pressure slowly moving east
through the Ohio Valley and low pressure in central Canada will
maintain gusty southwest winds through the midweek period. Small
craft advisories remain in effect through this evening for Saginaw
Bay and the nearshore waters of Lake Huron from Port Austin to
Harbor Beach. Southwest winds will then diminish slightly this
evening below 20 knots before increasing to 20-30 knots again on
Wednesday across much of Lake Huron.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
DISCUSSION...JVC/TF
MARINE.......JD


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



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