Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251741

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
141 PM EDT TUE OCT 25 2016


Diurnal cu field underway under with the inversion around 4kft
holding CIGS around 3-4kft. This will persist through the afternoon
and should quickly scatter out this evening. Skies will clear out in
the lower levels but cirrus streaming in from upstream will keep
some upper level clouds around. Northwesterly winds will weaken
tonight while becoming easterly by morning. Clouds will be
increasing while CIGS lower as the next low pressure system tracks
just south of the MI border. The warm front remaining to our south
will lead to overcast skies and increasing easterly flow. Start time
for precipitation looks to remain outside the current taf window.

For DTW...Winds will continue to bounce around from 300-340 this
afternoon for a couple more hours. High pressure overhead will cap
off the winds around 7 to 8 knots before decreasing this evening.
Diurnal CU around 4kft will take us into the evening hour with a
rapid decline in coverage after 23Z.

//DTW Threshold Probabilities...

*  high confidence in cigs aob 5000 ft this afternoon.


Issued at 313 AM EDT Tue OCT 25 2016


A cold start to the day, as temperatures currently reside in the 30s
under mostly clear skies. Surface High/Ridge axis over Western Great
Lakes this morning to slide East today as upper level ridge builds
through Tonight. A back door cold front attempts to sink south from
northern Lake Huron this morning as strong high (1037 MB) builds
over northwest Ontario, and looking at more low clouds across
northern half of the cwa, underneath/closer to the cold pool (-4 to
-5 c at 850 mb), as just about every model (rap/nam/gfs/hrrr)
indicating saturation at 850 mb sinking south during the day before
mixing out. 925 mb temps ranging from 1.5 C north to 4 C toward the
southern Michigan border suggestive of highs in the upper 40s to
lower 50s, in line with latest MAV guidance.

Upper level energy working through the Rockies this morning, and
there has emerged some differences for Wednesday, as bulk of the
upper level energy/pv drops into the southern Mississippi River
Valley. Subsequently, the surface low over the Midwest is not
forecasted to be as strong. Still plenty of trailing upper level
support and moisture advection to support developing rain Wednesday
evening/night, but 00z nam draws into question the daytime hours of
Wednesday, as the 700 mb front becomes active just over the north
third of the cwa, with no precipitation associated with the 850 mb
fgen indicated for southern two thirds of the cwa. The NAM Looks to
be an outlier compared to Canadian/GFS/Euro, as those solution also
show an active 700 mb zone with about 5.5 g/kg of specific humidity,
but slicing right through the center of southeast Michigan,
supportive of widespread rainfall by the afternoon hours. Also, with
the weaker low, less of a surge of warm air, and a low track south
of the Michigan border, potential precipitation type issues still
lurking along/north of I-69. With that said, still will favor all
rain with easterly flow coming off the mild waters of southern
Lake Huron, as raw surface temps (per colder euro/gfs solutions)
forecasted to reside predominately in the upper 30s to lower 40s.
As the low passes east Wednesday Night, more of a northerly
drainage wind (less influence from Saginaw Bay) setting up across
Tri-Cities Region could make for a close call with respect to wet
snow mixing in before rain tapers off. Even during the day on
Thursday, cold cyclonic flow with 850 mb temps of -4 C could
support convective showers of graupel with the steep low level
lapse rates as highs reside in the 45 to 50 degree range.

For the weekend, model consensus splits the upper level energy, and
looking at two weaker low pressures sliding through the Great Lakes
Region, which is a significant deviation from last night`s single
stronger low tracking through. With the energetic Pacific flow still
well offshore, still time for additional model adjustments, as
Canadian solution is much faster and weaker compared to Euro/GFS.
Also, Hurricane Seymour in Pacific could have a modest influence as
it interacts with the strong upper wave/trough approaching
California Thursday night.


Cold northwest flow will maintain unstable conditions across area
waterways today.  Small craft advisory conditions will persist
during this time for all near shore waters of Lake Huron including
outer Saginaw Bay.  Gusts of 25 to 30 knots will be common across
the open waters, but winds are expected to remain below gale force.
Winds and subsequently waves will gradually diminish late today and
tonight as high pressure builds into the region.  Winds will
increase out of the east Wednesday and Wednesday night as low
pressure lifts toward the region.  Strongest winds expected
Wednesday night and early Thursday, where gusts of 25 to 30 knots
are again expected.  While the potential for a period of near gale
force is still possible over portions of the open waters, the
current forecast maintains gusts below gales at this time.


A low pressure system tracking from the central Plains through the
northern Ohio Valley will result in a widespread rainfall event
locally Wednesday through Thursday.  The heaviest rainfall will
occur late Wednesday into Wednesday night.  Rainfall will taper off
in both intensity and coverage on Thursday.  The current forecast
calls for a broad area of rainfall amounts around three quarters of
an inch.


Lake Huron...Small Craft Advisory until 8 PM EDT this evening FOR LHZ421-441>443.

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



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