Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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200
FXUS63 KDTX 241006
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
506 AM EST Fri Nov 24 2017


.AVIATION...

VFR conditions will prevail through this afternoon with
southwesterly winds increasing as a low pressure system strengthens
the pressure gradient across southeast Michigan. Wind gusts will
reach around 20-25 knots, but shouldn`t reach much higher given the
shallow boundary layer. Mid and high clouds will move in as the low
pressure system nears this afternoon. MVFR ceilings and a few light
rain showers may accompany the cold front later tonight, but do not
anticipate coverage in precipitation to be great enough to mention
this TAF issuance. Winds will gradually veer to the west late
tonight ahead of the the front and then to the northwest tomorrow
morning behind the front.

For DTW...Ceilings below 5000 feet will be possible in the afternoon
as the low pressure system nears and mid to high clouds move into
the region. Greater chances for lower ceilings will be associated
with the cold front arriving late tonight.

//DTW THRESHOLD PROBABILITIES...

* Low for ceilings aob 5000 ft through the afternoon. Medium after
  00Z.

&&

.PREV DISCUSSION...
Issued at 301 AM EST Fri Nov 24 2017

DISCUSSION...

Sfc low pressure over the Ontario/Manitoba border as of 07Z will
track across northern Ontario today ahead of a mid level short wave
impulse traversing the northern plains. Increasing low level
southwest flow across Lower Mi in advance of the associated sfc cold
front will support aggressive low level warming. 925MB temps are
forecast to rise to +7 to +11C by late afternoon, with the warmer
temps actually advecting into the Saginaw Valley region. The low
level warming under a late November sun angle will greatly limit
daytime mixing depths. Nonetheless, mixing should still be enough to
support late afternoon highs in the upper 40s/low 50s (mid 50s
across the Saginaw Valley) under breezy conditions. A region of
showers now tracking into far nrn Lower Mi is tied to a region of
mid level moist isentropic ascent, which will largely pass well
north of the forecast area this morning. There will however be a
notable increase in high level clouds this afternoon.

The aforementioned mid level short wave will track across Lower Mi
tonight. While the better mid level height falls will be north of
the forecast area, some enhanced mid level frontal forcing, aided by
entrance region jet dynamics will impact Se Mi between 03Z and 09Z.
While the forcing looks fairly good, albeit brief, moisture depth
during the period of peak forcing is lacking. Thus just chance type
pops for rain showers (as temps hold in the 40s) will be warranted.

The sfc cold front will be east of Se Mi by daybreak Saturday, with
post frontal cold air advection persisting through the course of the
day as 925mb temps fall back into the -1 to -2 deg range. This will
lead to temps dropping into the 30s during the course of the
afternoon. There is generally good model agreement in showing a
secondary short wave tracking across srn Lower Mi Sat afternoon
within an amplifying longer wavelength trough. Although the better
lake instability will be focused across the nrn lakes, the upper
wave and cold air advection will support increasing cloud depths.
With some degree of low level moisture, these factors suggest at
least a low chance for some light rain/snow showers Saturday.

Relatively cool temperatures will persist Sun into early Monday as
Se Mi resides along the southern periphery of an eastern Canadian
upper trough. Mid level heights will then rise across the eastern US
Monday into Tuesday ahead of a northern stream trough. This will
support highs rising into the 50s again by Tuesday. The 00Z model
suite suggest this wave remaining largely north of Lower Mi, with
minimal cold air advection into srn Mi by midweek.

MARINE...

Gusty southwest winds expected across the Great Lakes region this
afternoon as a low pressure system moves across southern Ontario.
The surface pressure gradient will strengthen and result in
southwest winds of 25-30 knots across Lake Huron. Gusts to gales
this afternoon are expected across the Saginaw Bay and the open
waters of Lake Huron, with the exception of the far northern portion
of the lake west of Presque Isle. Rough waters for small crafts are
likely across nearshore from Port Austin to Port Huron, Lake St.
Clair and western Lake Erie. Winds will shift to the northwest
behind a cold front early tomorrow and remain elevated across Lake
Huron through late tomorrow night.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...Gale Warning from noon today to midnight EST tonight for LHZ462>464.

     Small Craft Advisory until 4 AM EST Saturday for LHZ441>443.

     Gale Warning until midnight EST tonight for LHZ362-363-421-422.

Lake St Clair...Small Craft Advisory from noon today to 4 AM EST Saturday for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from noon today to 4 AM EST Saturday for
     LEZ444.

&&

$$

AVIATION.....AA
DISCUSSION...SC
MARINE.......AA


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