Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 281631
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1231 PM EDT Fri Jul 28 2017


.AVIATION...

Northeast flow prevails as high pressure builds in from the
northwest immediately behind the passing low presently located
directly overhead. Corridor of increased ascent easily identified on
visible as widespread CU below 5kft. A few showers will be possible
in the Detroit area as this activity pushes south and east over the
next several hours. Otherwise, expect clouds to dissipate giving way
to SKC overnight.

For DTW...Prevailing wind out of the NE quadrant will favor NE
operations through the forecast period.

//DTW THRESHOLD PROBABILITIES...

* High for cigs aob 5kft

&&

.PREV DISCUSSION...
Issued at 1013 AM EDT Fri Jul 28 2017

UPDATE...

A line of showers has developed just east of the international border
on Lake St Clair. The showers are feeding off some remnant lake
moisture, aided by some enhanced boundary layer convergence within
increasing upper level divergent flow. Boundary layer winds will
continue backing toward the north this morning and early afternoon,
with the better low level convergence remaining focused across
Ontario. This should keep these showers east of Monroe and Wayne
Counties through at least early afternoon.

A compact upper low is now churning over west-central Lower Mi, with
the center of the circulation expected to track across Livingston and
Wayne Counties in the 19Z to 22Z time frame. The APX and GRB 12Z
upper air soundings showed mid level temps (around 850MB) to be a
little warmer than early model solutions suggested. Taking this into
consideration, it will likely take until peak daytime heating for any
convective development to be realized directly under the mid level
cold pool. This suggests the best potential for any late afternoon
convection will be confined to Wayne and Monroe Counties. This area
will also experience a little enhanced low level moisture
contribution from the lakes under the NNE flow. These factors suggest
the only update needed to the going forecast will be to decrease pops
slightly from the northern Detroit suburbs and points north.

PREV DISCUSSION...
Issued at 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.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Advisory until 4 AM EDT Saturday for MIZ048.

     Beach Hazards Statement until 10 PM EDT this evening for MIZ049-055-
     063-083.

Lake Huron...Small Craft Advisory until 4 AM EDT Saturday for LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory until midnight EDT tonight for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 AM EDT Saturday for LEZ444.

&&

$$

AVIATION.....JVC
UPDATE.......SC
DISCUSSION...MR
MARINE.......SF


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at www.weather.gov/detroit.



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