Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 111909

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
309 PM EDT Wed Oct 11 2017


Radar mosaic indicating rapid diminishing trend in coverage and
intensity of rain over Southeast Michigan as deformation shifts east
and increasingly sheared nature of the wave disrupts better elevated
theta-e advection. Steady rain will completely exit the area within
the next few hours, leaving behind a stout NE flow regime and an
abundance of trapped low-level moisture. Mixed conditions at the
surface will support a low ceiling that will keep overnight lows
elevated around 50 degrees. In addition, lower-level shear atop the
inversion and convergence within NE flow, particularly along the
glacial ridge, may result in periods of drizzle through the night.
Thus, introduced a low pop and dz to the forecast.

Rapid exit of today`s low pressure will allow for a very quick
transition to a return flow pattern by early Thursday as a deep, but
progressive trough forces low and mid-level winds to back to
southerly. Extensive low cloud canopy to the south will lift back
into the area with a weak fgen component evident on the returning
theta-e gradient. This will present a transient threat for brief
light showers lifting from SE to NW through Thursday. Agree with
previous forecast reasoning that QPF/duration of any showers on
Thursday will be brief. Extensive clouds will also suppress
temperatures in the upper 50s away from the lake shadow/along the
ridgeline and low 60s across far eastern portions of the CWA.

Lee cyclone will begin to organize Friday into Friday night as
height falls spread over the Front Range. Thermal field will rebound
substantially on Friday with 850mb rising into the low teens.
Diminishing cloud trend south of the warm front will support highs
reaching potentially reaching 70 degrees. Quality of moisture
transport oriented roughly parallel to the frontal zone will increase
Friday night into Saturday producing the beginnings of a warm
frontal rain band which may not waver much in location during its
stay through the weekend.

WAA is expected to persist throughout the day on Saturday as noted
in the 850 mb thermal profile, where temperatures averaging 12 C
Saturday morning push to an average of 16 C by Sunday morning. This
surge of warmer air will provide enough forcing to produce rain
showers and thunderstorms across central Michigan, including the
Flint, Saginaw, and Thumb regions, through Saturday. Rain and
thunderstorm chances are still possible across northern Metro
Detroit suburbs, however, PoP values will remain sub-50 percent
through Saturday (and near 0 - 20 percent for counties bordering the
Ohio) as models have been fairly consistent with placement of the
line of precipitation over the past couple of day. Precipitation
chances will increase across the Metro Detroit area early Sunday
morning into the afternoon as low pressure pushes across northern
lower Michigan into southern Ontario throughout Sunday, dragging a
cold front behind it.

Prior to the cold front pushing through the state, WAA and periods
of sunshine will allow temperatures to peak in the low to mid 70s
across Metro Detroit, with northern suburbs north of I-69 expected
to see mild temperatures in the mid to upper 60s. During and after
the passage of the front, wind gusts are expected to pick up into
the 20 - 25 mph range, as a well mixed layer starts to tap into
stronger winds aloft. Wind gusts will then diminish early Monday
morning as a broad surface high pressure system builds into the
Great Lakes, with dry conditions and seasonal temperatures making a
return for the first half of next week.



Strong northeast winds of 20-25 knots, with isolated gusts to gale
force through this afternoon, will gradually subside tonight as the
low pressure system exits off to the east. Brief high pressure will
build in its wake for Thursday and Friday, before a slow-moving
frontal boundary approaches the region this weekend with another
round of rainfall. Winds will become southeasterly by late Thursday,
and continue veering to southwesterly on Friday ahead of the frontal

Small craft conditions will persist through much of tonight across
Saginaw Bay, the southern nearshore waters of Lake Huron, St. Clair,
and Lake Erie mainly for waves of 3-5 feet as lingering wind wave
energy persists. Across the open waters of Lake Huron, wave heights
will be as high as 7 feet at times through this evening. More
favorable boating conditions will return for Thursday and Friday as
winds turn to the southeast, although waves of 3-5 feet will persist
along the exposed nearshore waters of the Thumb region.



Rainfall will continue to taper off into this evening across
Southeast Michigan, as low pressure system both at the surface and
aloft exits to the east. Additional rainfall amounts of under a
quarter of an inch are possible through this evening. Generally dry
weather is expected Thursday and Friday. A slow-moving frontal
boundary looks to impact the region this weekend with multiple
rounds of rain and possible thunderstorms, with low pressure
development along the front potentially enhancing rainfall totals.
Rainfall amounts in excess of one inch will be possible across much
of southeast Michigan this weekend.


Issued at 306 PM EDT Wed Oct 11 2017


MI...Lakeshore Flood Advisory until midnight EDT tonight for MIZ048.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ443.

     Small Craft Advisory until 4 AM EDT Friday for LHZ441-442.

     Gale Warning until 10 PM EDT this evening for LHZ421-422.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.




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