Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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375
FXUS63 KDTX 181101
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
601 AM EST Wed Jan 18 2017


.AVIATION...

Ongoing mid level subsidence will persist through the duration of
the morning in the wake of an upper wave now passing southeast of
Toledo. The resultant deepening subsidence inversion and ample low
level moisture will maintain low clouds through the day. Morning
observations suggest the low level moisture is enough to support
some fog and sub 500 ft ceilings. Daytime heating should offer some
improvement in ceiling heights, but likely not enough to push them
into the MVFR category. There is a good deal of uncertainty as to
whether or not clearing will occur tonight. The majority of model
solutions suggest either persistence of low clouds or rapid
development of fog following any brief clearing.

For DTW...Ceilings upstream across the I-94 corridor have dropped to
300 and 400 ft. These lower clouds are expected to push into metro
to some degree by 12Z. Winds should hold at 8-10 knots from the west-
southwest as the center of sfc high pressure remains well south.

//DTW Threshold Probabilities...

* High for ceilings below 5000 ft through the TAF period.

* Low for ceilings and/or visibility below 200 ft/one half mile this
  morning and tonight.

&&

.PREV DISCUSSION...
Issued at 321 AM EST Wed Jan 18 2017

DISCUSSION...

Mild stretch of weather to continue...

Upper wave/500 MB low exiting the Ohio Valley this morning, with
good post wave subsidence occuring over southern Lower Michigan.
Unfortunately, forecasted soundings maintaining low clouds/moisture
trapped underneath subsidence inversion right through Tonight, and
with all the standing water and soaked ground across southeast
Michigan, this is the direction the forecast will be skewed. With
clouds holding, temps likely not doing much better than around 40
degrees.

Pronounced Upper level ridge axis (500 mb heights between 564-566 DAM)
will be overhead tomorrow, and NAM soundings still maintaining low
clouds, but with the inversion based around 1 kft, will favor the
low clouds mixing out and dissipating, although forecasted 950 mb
RH still muddled when comparing the GEM/GFS/NAM. Maxes could end
up anywhere where from mid 40s to best case scenario mid 50s based
off 925 mb temps of 7 C, but ultimately mixing is expected to come
up short of that level, and favoring upper 40s to near 50 degrees.
Assuming the low clouds clear out, there should be an increase in
high clouds as the elongated upper level low currently over the
Four Corners Region advances northeast into the Central Plains.

Very strong upper wave/Jet streak (100 knots at 500 mb) tracking
through far southern California will act as kicker system, helping
to shear apart the upper level system over the central Conus. None-
the-less, the stretched out trough axis and plentiful gulf moisture
lifting north into the Great Lakes region on Friday appears to be
sufficient to generate rain showers, as 00z Euro indicating 850 mb
dew pts around 7 C range, close to record climatology territory for
mid January.

Previously mentioned strong jet/upper wave to lift up through the
Plains over the weekend, maintaining the mild/deep layer southwest
flow over southeast Michigan into Sunday morning, and good
shot for Detroit to hit 50 degrees both Saturday and Sunday, as 925
mb temps reach or exceed 10 C per 00z EURO. We have already had 2
days (Jan 11-12) exceeding 50 degrees, which is the mean number days
for the month of January. Looking further at climatology records, 5
days of 50+ for the January (which looks doable) is fairly rare,
occuring about once out of every 10 years.

MARINE...

An elongated trough axis extending across Lake Huron in the wake of
the departing surface low will support light winds early this
morning. Sfc high pressure will then expand across the Ohio Valley
today, placing the Great Lakes within strengthening southwest flow
during the afternoon into tonight. Strong over-lake stability will
limit mixing potential, thus keeping winds near the lake surface
subdued in comparison to winds aloft. The gradient will however
still support some gustiness to the winds this evening, mainly from
Saginaw Bay into the middle of Lake Huron. Gusts in this region may
reach 25 knots at times. The high pressure will then build into the
eastern Great Lakes region on Thursday, leading to weakening winds
across the lakes. Light southeast winds will develop Thurs night and
persist through the day Friday in advance of a surface trough
lifting into the region from the Ohio Valley.

&&

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

$$

AVIATION.....SC
DISCUSSION...SF
MARINE.......SC


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