Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 180821

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


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

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.



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.


Issued at 1152 PM EST Tue Jan 17 2017


IFR conditions will prevail overnight as a shortwave works across
area and brings period of -RA/-DZ, especially KPTK south. Any light
rain showers will largely end by 12z, but stratus will only slowly
edge up into MVFR on Wednesday. West winds 10 knots or less will
back to southwest on Wednesday afternoon.

For DTW...Ceilings between 500-800 feet will improve to 1500 feet on
Wednesday and with any luck improve further into Wednesday evening.
Several hours of light rain showers can be expected overnight with
passage of shortwave. Vsbys may drop to IFR in -RA/BR for a time.

//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.

* High in precip type being all rain/drizzle overnight.


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



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