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Area forecast discussion 
National Weather Service Detroit/Pontiac Michigan
658 PM EDT Tuesday Jul 7 2015



Aviation...

With cold front well through area and drier low level air now
working into the area...MVFR ceilings will become lower VFR and then
scatter out from middle to late evening. This will lead to generally
clear skies overnight into midday Wednesday with north winds of 10
knots or so become light east-northeast as high pressure settles over the area.

For dtw...any remaining patchy -dz will end early in the forecast as
ceilings trend to lower VFR and then dissipate altogether after 04z-06z
tonight.

//Dtw threshold probabilities...

* high for ceilings less than 5000 feet through this evening and low
for Wednesday afternoon.

&&

Previous discussion...issued 339 PM EDT Tuesday Jul 7 2015

Short term...through tonight

The cold front is currently completing its passage across Southeast
Michigan...currently aligned along the Detroit River. Some enhanced
moisture behind the front is leading to some light rain and
drizzle...but that will not last long as dry air quickly surges
southeastward across the state. Dewpoints across northern Michigan area
already down below 50 degrees with middle 50s across middle Michigan. Models
advertise the front to slowly take on a more east/west orientation across
the Northern Ohio valley overnight as an area of surface high pressure
builds in across the Great Lakes. The result will be a decent
dewpoint gradient across the area ranging from the upper 40s across
the Saginaw Valley up to the middle 50s near the Ohio border. This will
in turn set the limit to the cooling potential overnight even as
skies clear under a shortwave ridge sliding overhead and surface high
pressure in place...and 925mb temperatures fall to 12c. The big question is
how much are the models over doing the bl moisture behind the front?
Will lean to a drier forecast with mostly clear skies as the visible
satellite is already showing the cumulus field eroding over the up and
northern Michigan.

Long term...

Expansive high pressure currently over the northern plains will take
over during the day on Wednesday as it moves east into the Great
Lakes region. This high will bring a day of drier conditions before
the next low enters back into the picture. Low pressure will be in
the process of moving in from the southwest late Wednesday night
bringing another chance for rain. Better chance for rain will occur
across southern areas of the County Warning Area...especially areas closer to the
Ohio border as the low skirts along Northern Ohio and Lake Erie.
This correlates to where the better instability will be as the system
quickly moves across and off to the east. Current timing of the
heavier rain looks to be Thursday morning...but with timing issues
in the various models this will be narrowed down with later forecast
issuances. This system is expected to bring areas of heavier rain
as the latest soundings are advertising precipitable water values climbing into
the 1.5 to 2 inch range. Rain then diminishes by late Thursday
afternoon as high pressure builds back in over the area lasting
through the overnight hours.

Friday through Monday...strong upper ridge over the southeastern US
will retrograde to the west. The ridge never quite builds all the
way into the Great Lakes...leaving US on the active outer fringes
with periodic disturbances arguing for shower and thunderstorm
chances. Deep-layer moisture will increase into the weekend as well
with precipitable waters at or above 1.5 inches from Saturday Onward. Forecast temperatures look
to be near to slightly above normal.

Marine...

Windy conditions behind the passing cold front will continue to
diminish through the evening as high pressure builds in overnight
and into Wednesday. Small craft advisories remain in effect though
early tomorrow morning for the nearshore waters of Southern Lake
Huron. High pressure...averaging 30.10 inches...will hold through
the day and into the evening on Wednesday before a weak low pressure
system moves across the southern Great Lakes. This low will
increase easterly/northeasterly flow across Lake St Clair and Lake
Erie before winds become light for the remainder of the week.

&&

DTX watches/warnings/advisories...
Michigan...Beach hazards statement until 10 PM EDT this evening for miz049-055-
063.

Lake Huron...Small Craft Advisory until 6 am EDT Wednesday for lhz441>443.

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

$$

Aviation.....Dg
short term...drk
long term....ss/dt
marine.......ss



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