Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 222000

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
300 PM EST Sun Jan 22 2017


The inverted surface trough that is parked over the region is
forecasted to remain overhead until Monday night. High ambient lower
tropospheric moisture with nothing in the dry air advection
department supports continued concern for continuation of fog
through the overnight. There has been some modest improvement in
surface visibilities in some places, with little to no improvement
in others. The Dense Fog Advisory had been extended earlier until
Monday 15Z. No changes to the headline will be made this forecast

Tonight...Models have been enjoying the impressive inverted low
level trough and associated high moisture/low level convergence by
generating light QPF tonight. Forcing is almost nonexistent aloft,
with no upper level jet streak. System relative isentropic motion is
unquestionably that of isentropic downglide during the next 12-18
hours over southeastern Michigan. Some weak ascent is progged over
portions of Ontario and Lake Erie corresponding to a narrow corridor
of maximum low to midlevel theta e. However, during the tonight
period this will remain to the east of the area, largely stalling
where it is now in current regional mosaic. As a result, decided to
clean up the forecast by removing PoPs and inserting areas of
drizzle instead.

Monday...In agreement with previous forecast reasoning for a High
PoP low QPF type event early Monday. Jet forcing again remains low
favoring little to no shot at deep lift. However, midlevel axis of
greater deformation will support deeper moisture and neutral lapse
rates in the 800-700mb layer. Latest in-house probabilistic
information suggests a moderate to high probability of .10 of liquid
by late Monday for the Detroit Metro and eastern CWA, low to
moderate to reach .10 for the north and western cwa.

Monday night and Tuesday...Shortwave ridging work through the region
in advance of the developing low pressure system over the central
Plains. Any precipitation that remains Monday night will be
inconsequential with limited forcing limited to orphaned low level
convergence. Temperatures Tuesday will be fairly similar to Sunday-
Monday with above average readings in the lower 40s.

Low pressure continues to trek across the Great Lakes region on
Wednesday bringing a continuation to rain and snow showers to the
area.  Unsettled weather will continue into the remainder of the
week into the weekend as the region remains under longwave
troughing.  Northwesterly winds then bring in cooler temperatures on
Thursday with temps dropping back to normal after being above normal
at the beginning of the week.



Dense fog advisory has been extended through Monday morning. There
has been little improvement in visibilities over the waters and
conditions are expected to deteriorate once again overnight. Winds
will remain fairly light while keeping an easterly component tonight
but will increase slightly in response to low pressure tracking
south of the region. As a result, waves will remain below 5 feet
through the next couple days.



Persistent dense fog is showing some signs of thinning this
afternoon with some nearby obs showing vsby greater than 1SM, and in
some cases in northern OH and extreme SE MI 10SM. Will have to watch
this southern edge of the fog shield to see if it can shift
northward at all. Winds will increase slightly this afternoon out of
the east/northeast which should help conditions improve across most
of the area, even if only for a few hours. Even with slight
improvement to IFR (possible MVFR) vsbys this afternoon, cigs should
remain in the IFR/LIFR range. Any improved conditions will
deteriorate back to LIFR tonight as dense fog fills back in. Some
light rain may start lifting into the region Monday morning. Will
continue a pessimistic forecast til observations suggest otherwise.

For DTW...Clear skies are not far away, as far north as Monroe, but
indications are that this will not lift into the terminal. Current
0SM should not last much longer as we should see some improvement
for a couple hours this afternoon, but atmosphere remains primed to
tank again tonight.

//DTW Threshold Probabilities...

* High for cigs aob 5kft.

* Medium for cig and vsby below 200 ft and 1/2sm through 20Z.
  High again tonight.


MI...Dense Fog Advisory until 10 AM EST Monday FOR MIZ047>049-053>055-

Lake Huron...Dense Fog Advisory until 10 AM EST Monday FOR LHZ361>363-421-422-

Lake St Clair...Dense Fog Advisory until 10 AM EST Monday FOR LCZ460.

Michigan waters of Lake Erie...Dense Fog Advisory until 10 AM EST Monday FOR LEZ444.




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