Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 211650

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1250 PM EDT FRI OCT 21 2016


Ongoing low level cold air advection will sustain a deep low level
inversion through the day. The flux of moisture off Lake Huron
within the N-NE flow is supplying ample cloud cover to the region.
Given slightly rising inversion heights, cloud bases will trend
slightly upward during the afternoon and evening. There will however
continue to be areas of MVFR based clouds within more organized lake
bands, impacting mainly FNT and PTK. The low level flow will back
slightly toward the N-NW this evening into the overnight. This will
cut off the lake connection to Central Lower Mi and will allow an
opportunity for clearing to overspread much of SE MI inland from
Lake Huron. There is still uncertainty as to the extent and
timing of this clearing. The ongoing expansion of clouds suggests
perhaps a late evening clearing.

For DTW...Recent observations have shown a trend toward a more
northerly wind direction (350-360 deg). The well mixed boundary
layer will support gusts up around the 20 knot range during the
afternoon. The loss of daytime heating this evening (21-23Z) will
result in a decrease in wind speed and a backing of the wind
toward the NW.

//DTW Threshold Probabilities...

* Moderate in ceilings below 5000 ft this afternoon and evening. Low
  overnight and Sat morning. Moderate Saturday afternoon.


Issued at 335 AM EDT Fri OCT 21 2016


Steady expansion of high amplitude troughing into the region today.
The ensuing reduction in mean thicknesses will translate into a step
downward in the thermal profile relative to recent days.  Cold air
advection under prevailing north-northeast flow will sustain a
favorable environment for inland penetration of moisture off Lake
Huron. This will supplement the existing 3000 to 4000 ft of
moisture depth tucked beneath a stout inversion based near 850 mb.
Given the advective component and increasing mid level cyclonic
flow, this should support renewed expansion in shower coverage
through the afternoon hours. Highest precipitation chances
certainly allocated for the thumb region, but recent hi res
guidance points to the potential for inland penetration as far
west as the Flint-Howell corridor. Limited insolation potential
given the extensive cloud cover will contribute to a notably
cooler day, as will a firm and intermittently gusty north wind.
Highs in the vicinity of 50 degrees.

Upper trough axis exits to the east tonight, with a backing low
level flow eventually pivoting the Lake Huron moisture plume largely
offshore. With that said, some perpetuation of the existing stratus
may continue well into the night given the existing low level
thermal troughing.  This lends some uncertainty as to the potential
nocturnal cooling response.  In addition, surface ridging is
displaced too far to the west to yield a more favorable light wind
field. Thus, continue to favor a low temperature distribution
that leans on the warmer side of the model guidance spectrum. This
places the coldest locales in the mid 30s.

Deep west-northwest flow Saturday as upper heights slowly begin
to recover. Eastward propagation of a residual ribbon of Lake
Michigan moisture augmented by diurnal heating likely translates
into a solid expansion in stratocu. Limited overall diurnal
temperatures response despite a modestly mixed profile and at
least partial sun. Temperatures a touch warmer relative to
Friday, with highs 50 to 55.

Solid pattern of warm air advection emerges for Sunday, as low level
southwest flow briefly takes hold immediately downstream of the next
inbound short wave and cold front.  This process will nudge readings
back up to around 60 degrees. Limited moisture availability and
simply a glancing shot of forcing seemingly translates into
minimal potential for rainfall with this frontal passage Sunday
night. A dry post-frontal airmass will then tilt on the cooler
side of normal early next week.


Much colder airmass in place over the Great Lakes Region, with
strong northerly winds between 20 and 30 knots Today and Tonight
as low pressure deepens along the mid Atlantic and northeast
coast. Small craft advisories remain in effect for nearshore waters
of Lake Huron. Winds will remain strong tomorrow but will be out of
the northwest, with frequent gusts to around 30 knots over the open
waters. if the low over new England is a bit farther west and
stronger, gale force winds could develop with the deep mixing.
Winds look to slowly diminish Saturday night ahead of the next weak
low which moves through on Sunday...allowing for winds to drop at or
below 15 knots.


Lake Huron...Small Craft Advisory until 4 AM EDT Sunday FOR LHZ441>443.

     Small Craft Advisory until 10 PM EDT Saturday FOR LHZ421-422.

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



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