Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 220358

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1158 PM EDT Wed Mar 21 2018


Dry northerly flow will sustain VFR conditions through Thursday. A
lingering canopy of bkn mid level cloud will linger tonight, but
skies will remain clear across the lowest 10k ft. Clearing skies
then for Thursday under gradually building high pressure. A somewhat
variable wind of carrying a northerly component overnight will shift
definitely out of the northwest by Thursday morning. Winds remain
modest from the northwest through the daylight period.

For DTW...North-northwest winds overnight gradually becoming
northwesterly Thursday /320-330 degrees/. Winds speeds below 7 kts
overnight, nudging up near 10 kts during the day.


* None.


Issued at 340 PM EDT Wed Mar 21 2018


Closed geopotential height anomaly over the Ohio Valley and Mid-
Atlantic has maintained an influence on the wind field over the
Central Great Lakes today as north northeasterly flow of 20 to 25
knots has been commonplace. Trailing shortwave and jet energy into
the rear portions of the upper level low, resulted in a relatively
strong inverted trough back into portions of western Ohio earlier.
All forecast information supports this surface trough stripping out
this evening.

For tonight, low level dry air will become increasingly entrenched
across the region with sustained northeasterly flow in place. More
quiet weather. There is probably some question of high and mid cloud
potential for tonight with modeled RH showing a corridor of some
saturation advection west to east the latter half of the night.
However, integrity and transparency of ac/high cloud is very much in
doubt gauging from upstream cloud this afternoon.

Sustained northeasterly flow behind the large east coast low
pressure system will allow for deep column cold air advection over
southeastern Michigan on Thursday. Not necessarily colder near the
surface, but degree of cooling in the midlevels will support very
stable conditions. Differential height rises locally will support
some increased surface ridging over the state by late Thursday but
not enough to dissipate the northerly gradient flow. Generally
preferred MOS with a cooler blend given good amount of insolation.
Slowly evolving pattern over North America the latter half of the
week brings a virtual persistence forecast on Friday. Only real
question is how far the surface high will move eastward. With
dominant northern Canada surface high staying still, preference is
for below normal temperatures again on Friday.

Temperatures on the cool side remain through the weekend. Highs in
the 30s and lower 40s with overnight lows in the 20s. Strong high
pressure over Canada will continue to dominant the weather pattern
with northeast to easterly flow at the surface. A low pressure
system will move out of the plains and into the Ohio Valley on
Saturday, but current path keep the precip south of the Michigan
border. So things look to remain dry for the weekend with the high
pressure in control and a mid/upper level ridge passing over.

A long wave trough begins to set up across the western US next week
and will bring the next shot of precipitation to southeast Michigan.
Precipitation is forecast to arrive Tuesday afternoon. Temperatures
will also be on the increase to starting Monday and continuing
through midweek. High temperatures will begin to increase into the
50s for much of the area by midweek.


Moderate northeast winds will continue through the afternoon hours
as low pressure departs to the southeast. Gusts 25-30 knots will be
possible at times, especially across southern Lake Huron. These
winds will continue to lead to elevated waves and hazardous
conditions for small craft along the nearshore waters of Lake Huron
and outer Saginaw Bay into tonight. High pressure will begin to
build across the region from the upper Midwest tonight allowing for
the flow to slacken and back more to the north and northwest heading
into Thursday. Light to moderate northerly flow will continue into
Friday before veering to the northeast this weekend as low pressure
passes by to the south.


Lake Huron...Small Craft Advisory until 2 AM EDT Thursday for LHZ421-422-441>443.

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



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