Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 282308
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
708 PM EDT THU JUL 28 2016


.AVIATION...

Isolated showers firing along local lake boundaries early in the
forecast will likely not affect terminals as activity dissipates
towards sunset. VFR conditions will then prevail into Friday
afternoon. Similar diurnal cumulus/convection will fire again on
Friday afternoon, but confidence in coverage/location remains low.
Will forgo mention in forecast attm, but may consider PROB30 KPTK
south by 20z or so in later forecast. Northeast flow will persist
throughout the forecast between high pressure to the north and a
stalled frontal boundary over the northern Ohio Valley.

For DTW...Northeast flow will drop below 7 knots this evening, but
increase to 8-10 knots again midday Friday. Isolated showers should
dissipate as forecast begins and not affect terminal. Similar
activity will occur on Friday afternoon.

//DTW Threshold Probabilities...

* Low for thunderstorms impacting kdtw through 02z and again after
  20z Friday.

* Low for cigs aob 5kft with aforementioned convective activity.

&&

.PREV DISCUSSION...
Issued at 351 PM EDT Thu Jul 28 2016

DISCUSSION...
Very muddled pattern over the Great Lakes today.  Large closed 500mb
low over northern Quebec has a trough axis extending southwest
through the western Lakes.  In the meantime Large surface high
pressure centered over Manitoba has surface pressure axis extending
into lower Michigan under the low axis. This is producing broad
northeast flow into the area advecting drier boundary layer air.  A
diffuse frontal boundary around 850mb that produced showers across
this area earlier in the day is settling southward with just broken
to scattered clouds.

Challenge with forecast is chances and coverage for any precip the
rest of today through Saturday. Cu build up this afternoon has been
suppressed by drier more stable northeast flow and cirrus passing
overhead from the south.  Cape values range from a 100 joules in the
Thumb to around 1k along the Ohio border were dew points remain in
the upper 60s.  Weak warm air advection in the mid levels has also
been providing weak capping.  Most convection today around the lakes
has been occuring from lake breezes off of lake Michigan. Moderately
strong northeast flow has eliminated lake breeze boundaries over the
area today.  Will still carry small to slight chc the rest of this
afternoon and evening for convection...mainly western and southern
parts of forecast area as any meso convergence could Early break
weak cap.

Tonight through Saturday night models indicate weak pv maxes  to
eject out of trough axis to the west from time to time.  Different
models show different strength, timing and location of pv maxes
ejecting out so will carry small chance all locations through
period. Instability will remain on the low side with best and
deepest moisture across the western and southern periphery of the
forecast area.  Highs will be several degrees lower then todays
Friday and Saturday as northeast flow will remain.

On Sunday, heights will begin to rise slightly as the broad trough
axis shifts east. This will promote a mainly dry forecast, although
with lack of a strong subsidence signal can`t rule out a diurnal
shower/storm or two. More concerted height rises occur Monday
through Wednesday, which will result in a warming trend from the
near-normal values on Sunday. Moisture advection looks to stay out
to the west until at least mid-week, favoring a dry forecast locally.

MARINE...

Small craft advisories remain in effect for persistent fresh onshore
flow and elevated wave heights in the nearshore zones of Lake Huron
through Friday. Maximum wave heights in excess of 6 feet will be
found in the southern basin where fetch will be greatest. Moderate
east to northeast flow will continue through the weekend.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until midnight EDT tonight FOR MIZ048-049-
     055-063.

Lake Huron...Small Craft Advisory until 10 PM EDT Friday FOR LHZ421-422-441>443.

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

$$

AVIATION.....DG
DISCUSSION...DRC/DT
MARINE.......DRC


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