Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 181727
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
127 PM EDT Tue Jul 18 2017


.AVIATION...

High pressure will push towards the eastern Great Lakes region
through the early evening bringing a continuation of quiet aviation
conditions. Light southerly winds will continue across the area
before the next cold front approaches early Wednesday. VFR conditions
will continue to hold into early Wednesday before lower VFR ceilings
begin to move in over the northern TAF sites. Rain showers look to
hold off until after sunrise across the northern sites, with slightly
better chances for southern TAF sites by Wednesday afternoon.

//DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 344 AM EDT Tue Jul 18 2017

DISCUSSION...

High confidence in the overall weather pattern setting up across
North America for the coming week with large, dominated pressure
systems present. The devils in the details though which currently
leave much to be desired, thus low confidence in smaller scale
features which will play havoc on precip forecast.

Nearly zonal flow will try to amplify with ridge continuing to build
across the southern states, but strong waves in the energetic jet
stream across the north will continue to flatten the ridge until the
end of the week. In the mean time, a strong trough rotating around
the northern Canada low will phase with the already enhanced jet over
Ontario eventually sending a cold front through lower MI Wednesday
and Wednesday night. Not much support for convection over SE MI with
the models as the front is show to weaken as it tracks through the
area, running into a stable and unfavorable airmass. Front looks to
cross mid MI early in the day preventing any diurnal instability from
developing. The front then slows its progress over southern MI as it
becomes aligned parallel to the steering flow. So there is a chance
for storms later in the day for counties closer to the Ohio border
but many "ifs" need to happen for that to occur.

Thermally, the front will bring little relief to temperatures that
have risen into the mid 80s. Persistent westerly flow will continue
to pump warm and moist air in from the Midwest and the strong ridge
nosing up into that region. Temps should linger near seasonal norms
through the weekend.

This front will stall over the Ohio Valley before being lifted back
north Thursday as warm front. Models hinting at a stronger wave
tracking over mid MI Thursday pulling the front north. This could
bring a period of rain to a portion of SE MI, but considering there
will be several shortwaves and possible convective systems upstream
to affect frontal placement, and models have not done well lately
with shortwave placement and timing, find it hard to get too excited
about this scenario right now. Same goes for Saturday which appears
to be the next opportunity for a stronger wave to dig down through
the region per GFS and EURO.  Having said that, the front will look
to linger across mid MI potentially Thursday thru Saturday meaning
there could be several periods of showers/storms possible across the
region. And on a more optimistic note, even with a several day
stretch featuring chance pops, there could be many people that
struggle to find precipitation over this stretch.  Will have to
handle this pattern on a more short term basis as the individual
waves become apparent on satellite and easier to track/time.

MARINE...

Light wind, generally from the south, will continue over all marine
areas today as high pressure drifts into the eastern Great Lakes.
The next frontal system will move through Lake Superior and reach
northern Lake Huron tonight. It will be strong enough to generate
thunderstorms but will only produce a modest northwest wind shift as
it moves through the region and exits western Lake Erie Wednesday
evening. Weak high pressure will follow as the front stalls south of
the Michigan border Thursday and Friday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....JVC
DISCUSSION...DRK
MARINE.......BT


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at www.weather.gov/detroit.



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