Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
081
FXUS63 KDTX 181746
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1246 PM EST Wed Jan 18 2017


.AVIATION...

Low level moisture/stratus continues to be locked in under inversion
across the area. A weak surface trough has been in place along
the glacial ridge from ARB-PTK-BAX. Along this line and to the
north ceilings have remain below 1kft along with visbys 4 to 6
miles. This mainly effecting PTK and FNT. Other taf sites have
improved slightly in visibility and ceilings from diurnal heating.
Mid level ridging will slowly work overhead by Thursday afternoon.
This warming will strengthen low level inversion but also bring
increasing subsidence and drier air aloft. Could see some breaking
up of stratus overnight, however, any clearing will likely lead to
increased radiational fog. So any taf site tonight that receives
fair amount of clearing will end up with denser fog. IFR
conditions will likely start improving towards end of taf period
as drier air and stronger subsidence will bring more clearing
Thursday afternoon. Wind flow will start off from the west around
10kts but back slightly and decrease this afternoon through
period.


For DTW...downsloping off of glacial ridge has helped ceiling rise
to or slightly above 1k ft and will likely remain like this into the
night.  Some partial clearing possible overnight which will lead to
some fog development.  The more clearing, the denser the fog
formation.  So may end up being bkn-ovc ceilings around 1k ft with
mvfr fog or sct-bkn ifr ceilings and fog.   Conditions will
gradually go vfr Thursday afternoon. Winds will begin westerly
around 10kts but back slightly while decreasing later this
afternoon.

//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
  tonight and Thursday morning.

&&

.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.....DRC
DISCUSSION...SF
MARINE.......SC


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.