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FXUS63 KDTX 291855

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
255 PM EDT Thu Sep 29 2022


Sprawling high pressure centered over Lower Michigan with the center
checking in at 1036 MB this morning (still holding around 1034 MB
this afternoon). 12z DTX showed a good subsidence inversion, with
very dry mid level air as 700 MB dew pt depression came in at 45 C.
Some low level moisture, enhanced by the Great Lakes, remains trapped
underneath the inversion. In fact, low clouds are still hanging
around at press time over Central/Southern sections of the CWA,
holding high temperatures near 60 degrees. Further lowering of
inversion heights should dissipate these clouds, but the 12z NAM is
still indicating high RH (~85 percent) values at the 925 MB level.
With the near surface flow becoming easterly overnight, Lake Erie
will become a player for areas toward the Ohio border, in addition to
Lake Huron for northern areas. Otherwise, favorable radiating night
and still some modest surface moisture (indicated by current dew pts
in the upper 30s to lower 40s) which will likely be conducive for
areas of fog (locally dense) as temperatures reach those values.
There is a weak upper level wave coming out of the Midwest which
could lead to some high clouds, but probably limited on the extent
and not much of a factor.

A stronger upper level wave looks to be slowly tracking through
Western Great Lakes tomorrow and into Lower Michigan Friday night.
Not expecting an impact to sensible weather however, as high degree
of low level static stability will be in place with 850 MB moisture
confined to Mid Atlantic States/southern Ohio. Remnants of Ian/500
MB low progged to reach the Central Appalachians by Saturday, and it
appears the return of a massive/strong high pressure building along
the southern Ontario/Quebec border will be sufficient to keep us dry
through the Weekend into early next week. Fairly tight pressure
gradient will allow for northeast winds over the weekend, peaking in
20-30 mph range, with the afternoon hours being the favored time
frame with the deepest boundary layer mixing.

Medium range models then suggest an amplified trough/strong 500 MB
low sweeping into Eastern Canada for the end of the work week,
delivering a very healthy cold shot, as 850 MB temps progged to
lower to -4 C in the Thursday/Friday time-frame per Euro.



Quiet marine conditions continue through remainder of the work week
as high pressure drifts directly over the central Great Lakes.
Light, largely variable winds shift to the northeast and increase in
strength over the course of Saturday in response to the remnants of
Ian advancing into the Mid-Atlantic states. Tightened local pressure
gradient will support peak gusts up in the 25-30kt range,
particularly over central Lake Huron, late Saturday. Winds gradually
weaken to finish the weekend/start the next week as Ian`s remnants
move back east out over the Atlantic.


Issued at 145 PM EDT Thu Sep 29 2022


Despite high pressure building southeast across the airspace with
strong subsidence aloft, a pesky inversion around 4 kft has allowed
remnant low-level moisture to be trapped in lingering light
northeast flow across much of the region. Lingering stratus deck
continues to slowly erode from northwest to southeast, with trends
continuing to show erosion over the next 1-3 hours as daytime
heating gradually wins the mixing battle. SKC eventually takes over
this evening and through tonight before fog becomes an increasing
concern with falling temps and decreasing dewpoint depressions
towards sunrise in prototypical early fall high pressure radiational
cooling environment. Friday will then see gradual increase of
streaming high clouds from remnants of Ian passing by way off to the

For DTW...Stratus/thick stratocu deck around 4kft looks to continue
holding on for at least another hour or two with continued erosion
of the low-level moisture proceeding from west to east into the mid-
afternoon hours. IFR fog will be possible towards daybreak.


* High for ceilings aob 5kft through mid afternoon. Low into the

* Low for ceiling 200 ft and/or visibility 1/2 SM towards sunrise
Friday morning.


Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.



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