Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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818
FXUS63 KDTX 260710
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
310 AM EDT FRI AUG 26 2016

.DISCUSSION...

Sfc high pressure will expand from the upper midwest across the
Great Lakes region today under building mid level heights. The low
level anticyclone will affectively suppress the moisture and
instability reservoir south across the Ohio Valley. Much drier low
level air has been slowly filtering into the forecast area in the
wake of last evenings fropa. Diurnal mixing will sustain this dry
air in the boundary layer, making today much less humid than
yesterday. While there is a decent moisture gradient along the
front, the thermal gradient is quite weak. Afternoon mixing depths,
especially within the drier boundary layer, will thus be able to
push afternoon highs into the 80s. The forecast will carry just
partly sunny skies today in light of recent satellite imagery which
show a good deal of high clouds streaming into the area from the
southwest. In fact, these clouds may be rather opaque at times
today. Despite the dry air and sfc high overhead, these high clouds
may limit the degree of nighttime radiational cooling enough to
support min temps just in the 60s tonight.

An influx of deep layer moisture and instability will be transported
into the Upper Mississippi Valley/wrn Great Lakes tonight into
Saturday as a result of strengthening southwest low level flow. This
will precede a mid level trough traversing the northern plains. Low
level convergence and moisture transport is then forecast to shift
into the northern Great Lakes Sat afternoon and evening, likely
driven by a convectively induced mid level short wave impulse.
Southeast Michigan will see a little more influence from the mid
level ridge parked over the Mid Atlantic, which will sustain low
level dry air through much of the day and result in rather shallow
mid level lapse rates. So just a low chance of some late day showers
will be carried in the forecast. Moisture depth is forecast to
increase Sat night as the low and mid level flow veers more westerly.
Weak mid level frontal forcing and height falls associated with the
aforementioned mid level trough as it rotates across the nrn Great
Lakes, combined with the ample moisture and weak instability, will
support better chances for showers/tstms Sat night. Mid level dry
air advection and capping is shown by the 00z model suite to
overspread srn Mi on Sunday, supporting a dry forecast past mid
morning. Model soundings suggest decent mixing under westerly flow
and lack of cooler air infiltrating srn Mi will support highs into
the 80s again Sunday.

Warm and dry conditions will persist to start the work week with a
mid level ridge across the Ohio Valley. The medium range model suite
are showing an amplification in the height field across noam next
week. A sfc cold front is forecast to move from north to south
across the area on Tuesday, associated with a northern stream mid
level impulse tracking across nrn Ontario. Mid level trough
amplification forecast across ern Canada late in the week suggests
cooler air will overspread the Great Lakes during the end of the
forecast period.

&&

.MARINE...

West-Northwest winds of 10 to 15 knots early this morning over lake
huron will become light and variable this afternoon, continuing
through tonight. A light southeast wind looks to develop on
Saturday, along with a low chance of showers and thunderstorms as
low pressure tracks through the Northern Great Lakes, allowing for
winds to shift to the west-southwest over the second half of the
weekend.

&&

.PREV DISCUSSION...
Issued at 1153 PM EDT Thu AUG 25 2016

AVIATION...

Post frontal westerly flow will bring slightly cooler and less humid
air into SE Michigan during the night. The main effect of this will
be mitigation of fog and low clouds to support VFR through the
night and upcoming day. Some lingering high clouds will follow
the departing entrance region of the upper jet into the northern
Great Lakes before high based cumulus develops during afternoon
into Friday evening. Dry conditions will continue through Friday
night as high clouds thicken while weak surface high pressure
builds over the northern Great Lakes.

//DTW Threshold Probabilities...

* none.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...SC
MARINE.......SF
AVIATION.....BT


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