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857
FXUS63 KDTX 181650
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1250 PM EDT Wed Oct 18 2017


.AVIATION...

A broad surface high pressure system in association with very dry
low to mid-levels will continue to promote SKC conditions through
the afternoon and evening. Additionally, a strong low pressure
systems situated and moving east across Manitoba into Ontario will
continue to promote southwesterly winds, with diurnal mixing
producing gusts between 20 - 25 kts during daylight hours.

During the mid to late morning hours, a weak cold front will then
push through Michigan, veering winds from SW to WSW. Conditions will
remain too dry for any precipitation to form, however, there may be
enough low-level forcing to produce a BKN cloud deck at 2.5 - 3 kft
over MBS as the front quickly pushes through. Weaker forcing across
the Metro airports will bring the possibility to see high cirrus
during the morning hours.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 345 AM EDT Wed Oct 18 2017

DISCUSSION...

Quiet weather pattern through the upcoming weekend as ridging aloft
and at the surface reside over the region for the most part. Some
slight eastward drift with the surface ridge centered to our SE will
occur as a mid level shortwave passes over Wednesday night into
Thursday, but it looks to build back west for the weekend. Next
notable system doesn`t look to arrive til Sunday into Monday.

Today will largely be dry and sunny as shortwave ridging split flow
region slides over the state immediately in advance of a weak
trough. Very dry airmass and subsidence region will keep the skies
clear. Will get some gusty winds as the gradient between the
approaching trough and surface ridge tightens/compresses overhead.
One limiting factor to winds will be the low mixing heights which
are forecast to rise to around 3kft. Most model soundings show this
cap gusts off around 25-30 mph but a couple higher gusts can`t be
rules out. Temperatures today will again rise to around 10F above
normal which is around 70F. As mentioned in the previous discussion,
temperatures slightly over achieved and the thermal profile looks to
warm slightly over yesterday so should only add to the confidence of
achieving these temperatures with the warm SW flow.

The strength of the ridge will steer the next upper level wave well
north of the Great Lakes through northern Ontario and James Bay. The
weakening cold frontal trough extending southward from this system
will sweep across Lower MI Wednesday night into Thursday. Little
fanfare with the trough as the airmass is so dry and surface ridge
still remains in place. Looks like at best we`ll see a period of
enhanced cloud cover with the trough but that should be about it.
Highs will fall back into the mid/upper 60s in responds to the weak
thermal trough as well.

Surface high builds back over the area Friday into the weekend,
still positioned for us to receive a favorable SW flow. Upper level
ridge amplifies over the eastern conus in response to the strong
trough coming ashore the west coast. Though the trough looks to
fracture as a potential 140+ kt jet surges east through southern
Canada, a cold front should track across lower MI sometime Sunday
into Monday bringing the next chance of showers. With the jet
quickly refocusing back to our north, warm westerly flow will
continue behind the front keeping near normal temps across southern
MI.

MARINE...

A pressure gradient between surface high pressure slowly moving east
through the Ohio Valley and low pressure in central Canada will
maintain gusty southwest winds through the midweek period. Small
craft advisories are again in effect today and tonight for Saginaw
Bay and the nearshore waters of Lake Huron from Port Austin to
Harbor Beach. Southwest winds will then diminish slightly this
evening below 20 knots before maintaining around 20 knots over Lake
Huron on Thursday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 10 AM EDT Thursday for LHZ421-422-441.

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

$$

AVIATION.....AM
DISCUSSION...DRK
MARINE.......CB


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