Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251917

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
317 PM EDT MON JUL 25 2016


Latest water vapor imagery shows good drying and subsidence taking
hold of lower Michigan, under confluent upper level northwest flow,
which will allow for surface high to build over the area Tonight.
None-the-less, dew pts are still a bit elevated (AOA 60 degrees),
and thus cooling tonight coming off the high temperatures around 90
degrees will be somewhat sluggish, but should still fall into the 60-
65 degree range (outside of urban heat island of detroit),
approaching normal values. With marginal near surface moisture, fog
can`t be totally ruled out, but coverage/risk too low to include in
zones. Dry airmass (pw values around 1 inch)/850-700 mb theta-e
trough will persist through tomorrow, providing seasonably warm day,
as highs expected to reside in the upper 80s/near 90 based on 850 mb
temps of 17-18 C.

Upper level low/circulation currently over northern Manitoba will
track into Eastern Canada over the next couple of days, helping to
drive a cold front/moisture gradient south into southern Lower
Michigan late Tuesday Night into Wednesday, providing chance of
showers and thunderstorms as showalter index looks to be solidly
negative, with k indices in the mid 30s. The boundary looks to be
mostly hung up north of M-59, right into Thursday. Thus, northern
areas stand the best chance to see activity. Limited moisture, with
MLcapes perhaps reaching 1500 J/kg in narrow swath, per 12z nam, but
0-6 km bulk shear looks to be only around 20 knot (per 12z euro),
mitigating severe chances. Detroit will have another opportunity
to tack on another 90 degree day south of the front with
favorable westerly flow and 850 mb temps aoa 18 C.

A shortwave tracking through the midwest during the mid week period
will attempt to draw north the tropical wave in the Gulf of Mexico,
likely sneaking into the eastern Ohio valley late in the work week,
but rain shield may miss southeast just to the south. Regardless,
the shortwave coming out of the midwest and general modest height
falls over the Great Lakes region will support chance pops late in
the week into Saturday. The 12z euro is one of the most aggressive
solutions with the amplification of the low at the surface and
aloft, and is thus slower to exit the Central Great Lakes over the
weekend. This would have implications on temperatures (cooler),
but at this point will be carrying temperatures near normal, as
Canadian and especially the Gfs indicating significantly warmer
850 mb temperatures (mid teens), which would lead to warmer
temperatures than currently forecasted (especially by Sunday).



West winds will become less gusty during the early evening with loss
of daytime heating. The center of surface high pressure will build
into the central Great Lakes region on Tuesday. Surface winds will
remain relatively light and variable throughout Tuesday. Favorable
boating conditions are then anticipated for much of the remaining
work week. A very weak frontal boundary will slip into the central
Lake Huron basin by late Wednesday before stalling. This boundary
may become a focus for some isolated to scattered showers and
thunderstorms late Wednesday and Thursday.


Issued at 141 PM EDT Mon Jul 25 2016


A weak jet axis will become increasingly organized over portions
of the Ohio River Valley and southern Great Lakes region late
today. This will force the dewpoint gradient south of lower
Michigan by tonight and support less humidity. Expect fair weather
cumulus to dissipate by sunset with clear skies through the
overnight with some potential for thin cirrus to pass along the
Michigan and Ohio border. A stable surface anticyclone is
forecasted to become centered over the central Great Lakes on
Tuesday. A light and variable wind is anticipated.

//DTW Threshold Probabilities...

* Fair weather cumulus cloud bases to lift above 5000 ft agl this


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



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