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afddtx

Area forecast discussion
National Weather Service Detroit/Pontiac Michigan
350 am EDT Fri Jul 28 2017

Discussion...

A cooler and drier environment now entrenched across Southeast
Michigan, this transition sustained via persistent low level
northeast flow immediately downstream of building high pressure.
Strong mid level circulation remains forecast to rapidly transit the
region during the daylight period. The underlying DCVA and cold
pool dynamics tied to this system will present at least a low
probability for convective development, particularly with
southeastward extent. However, the high degree of deep layer drying
certainly casts doubt on the prospects of seeing a greater response.
Recent hi-res guidance suggest the greater potential will reside
just to the south and east, where some localized convergence may
capitalize on a weakly unstable late day environment - MLCAPE below
500 j/kg. Ultimately, looking at a limited window for possible low
end coverage during the early-mid afternoon period, before renewed
mid level drying overwhelms a marginally moist cloud layer.
Afternoon temperatures will arrive on the cooler side of average,
with readings broadly distributed across the 70s - coolest in The
Thumb given the onshore flow.

High pressure will remain anchored over the northern Great Lakes
throughout the upcoming weekend. The presence of deep layer
subsidence and persistent north to northeast low level flow ensures
dry and stable conditions will hold throughout the period. Plenty
of sunshine and lower humidity will yield pleasant summertime
conditions for the last weekend in July.

Sprawling high pressure will remain tucked beneath low amplitude and
loosely organized upper level northwest flow during the early next
week. Gradual airmass modification under slowly building heights
will bring highs back into the lower and middle 80s during this
time. Dry conditions will hold, reinforced by transient shortwave
ridging through Tuesday. As height falls begin to carve out a
broader longwave trough across southern Canada, this may allow a
frontal boundary to ease into the region by Wednesday/Thursday. Next
shot for rainfall during this time.

&&

Marine...

Moderate northeast flow between 20 to 25 knots will develop over the
nearshore waters today, and small craft advisories remain in effect,
as significant wave heights up to five feet and maximum wave heights
near seven feet are expected over the Southern Lake Huron basin.
Northeast winds will be lighter tomorrow, and very light on Sunday
as high pressure settles overhead.

&&

Previous discussion...
issued at 1201 am EDT Fri Jul 28 2017

Aviation...

Question remains what sort of potential exists for stratus
development tonight in a low level cold air advection regime. Models
show some saturation potential in the 2.5 to 5.0 kft agl layer
overnight, but with largely dry ambient conditions at the near
surface and no rainfall to speak of, confidence remains low for
stratus development. Boundary layer gradient flow will increase from
the northeast late, which also dampens any shot at fog. Interesting
pv anomaly is shown to dig right across lower Michigan Friday which
is almost always a cause for concern. However, in this particular
case, limitations on moisture should keep a lid on ascent.

//Dtw threshold probabilities...

* low for cigs at 5kft after 09z Friday morning.



&&

DTX watches/warnings/advisories...
Michigan...Beach hazards statement from 8 am EDT this morning through this
evening for miz049-055-063-083.

Lake Huron...Small Craft Advisory from 8 am this morning to 4 am EDT Saturday
for lhz421-422-441>443.

Lake St Clair...Small Craft Advisory from noon today to midnight EDT tonight for
lcz460.

Michigan waters of Lake Erie...Small Craft Advisory from noon today to 4 am EDT Saturday for
lez444.

&&

$$

Discussion...mr
marine.......sf
aviation.....Sf

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