Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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334
FXUS63 KDTX 182253
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
653 PM EDT Sun Aug 18 2019

.AVIATION...

Line of convection has developed along the near surface trough axis
upstream. These storms will affect the Detroit regional terminals
and Flint in the first couple hours of the forecast. Winds will snap
around to the west in the wake of the front for a few hours before
relaxing back to southwest overnight. Enough moisture will remain
locked into the boundary layer to support nocturnal fog and low cloud
development. A cold front will slide south through the region Monday
morning - flipping winds to light northerly during the morning
hours. Post-frontal clouds are expected across the southern
terminals but should remain VFR.

For DTW...line of thunderstorms should begin to affect the western
areas of the DTW airspace after 00z with the main window of
affecting the terminal in the 01z-02z window. Light fog and low
cloud development is expected after midnight. Lingering ceilings
below 5kft are likely Monday.

.DTW THRESHOLD PROBABILITIES...

* Moderate for ceilings aob 5kft tonight and Monday.

* High for thunderstorms 01-02Z.

&&

.PREV DISCUSSION...
Issued at 319 PM EDT Sun Aug 18 2019

DISCUSSION...

The numerous showers and thunderstorms which worked through
southeast Michigan this afternoon (a few severe), helped drop
temperatures into the 70s, leading to a significant stabilization of
the airmass (see 19z SPC mesoscale analysis). Thus, confidence is
low that activity with the actual cold front will be severe, not to
mention the coverage of activity is in question this far north. At
least, the 17z Rap looks to be trending in the right direction (less
activity). None-the-less, still a short window to destabilize (lower
80s) before sunset, and the upper level dynamics/shear (50 knots of
effective shear) needs to be respected as it sweeps through around
00z. On the flip side, could be in the shadow of the organizing
thunderstorm complex developing over central Indiana into Ohio where
the max instability (MLcapes of 2500 J/kg) presently resides, which
should help mitigate our severe chances as well.

Strong upper level low (545 DAM at 500 MB) over northern Manitoba
will be the main influence/director to our weather over the several
day, as it swings through Ontario during the mid week period,
supporting a significant cool down.

An extension of trough axis will be lifting through the northern
Great Lakes tonight, with 500 MB heights beginning to rebound over
southern Lower Michigan on Monday. Thus, the cold front that slips
through southeast Michigan tonight, will more or less wash out. With
the lingering low level moisture, especially with the rainfall from
this afternoon, and weak surface convergence, some fog and/or low
stratus development appears possible late tonight.

500 MB heights rise to around 588 DAM on Monday, but still enough
residual low level moisture/850 MB Theta-e and instability around to
support low chance pops along/south of I-94.

Pseudo zonal upper level flow with upper level energy/PV coming out
of the Rockies and tracking through Midwest Monday night. It appears
the potential thunderstorm complex will track off to the southeast
during Tuesday and miss the state. This will also help cut off some
of the moisture advection ahead of the cold front, which tracks
through late Tuesday night or Wednesday. Thus, a dry frontal passage
remains possible.

Warmer temperatures, with highs in the 80s, will remain in place on
Wednesday before cooler temps come back for the remainder of the
week.  By Thursday, 850mb temps will be back in the single digits. A
slight chance of precipitation also remains in the forecast
Wednesday afternoon, as a wave passes over.  The rest of the
forecast period going into the weekend will feature pleasant
temperatures and dry weather as high pressure settles in over the
region.

MARINE...

A low pressure system lifting through lake Superior this afternoon
will pull a cold front through the region this evening. This front
may produce another round of thunderstorms this evening before
pushing east of the area. Southwesterly winds will veer westerly
behind this front tonight and to the northwest on Monday as a
secondary front drops through the region. Winds will be strongest
this evening out of the southwest with gusts reaching 25 knots.
Though cooler air will advect in behind the front tonight, high
pressure building in will weaken the gradient and prevent stronger
gusts tonight and Monday. Though mostly a dry forecast beyond
tonight, additional showers and thunderstorms will continue to be
possible over Lake Erie and St. Clair with the frontal boundary
stalling nearby.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Small Craft Advisory until 4 AM EDT Monday for LHZ421-422.

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

$$

AVIATION.....Mann
DISCUSSION...SF/SP
MARINE.......DRK


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at www.weather.gov/detroit.



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