Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 191914

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
314 PM EDT Mon Mar 19 2018


Northeast gradient is casting the typical Lake Huron springtime lake
shadow across the CWA with temperatures rising into the 40s across
the south while struggling into the mid 30s in the north. This will
continue to be the case tonight into Wednesday as the northeasterly
gradient intensifies with low pressure tracking across the Ohio
Valley and expansive high pressure over northwest Ontario. Dry
boundary layer flow will ensure clear skies this afternoon and again
on Tuesday while the nocturnal inversion may prove sufficient for
trapping some lake enhanced moisture by Tuesday morning, though any
boundary layer cloud development will likely be low in coverage and
short in duration. Raw NAM12 is always the preferred guidance for a
well-mixed nocturnal boundary layer, so no complaints with its low
to mid 20s depictions tonight. Highs on Tuesday mainly a persistence
forecast with some adjustment near the Ohio border for increasing
cloud cover during peak heating as low pressure tracks well to the
south. Despite sunshine, Tuesday will be deceptively cold as the
stout gradient keeps wind chills in the 20s and possibly upper teens
in the Thumb, particularly over the extensive snowpack there.
Virtually no change on Wednesday as flow slightly weakens and backs
to northerly with low pressure shifting to the east coast.

Strong upper ridging will move in on Thursday as amplified longwave
trough moves off to the east coast. This will extend lower
Michigan`s pattern of quiet weather through the end of the week as
high pressure dominates. Thermal trough lingering over the Great
Lakes (850 mb temps hovering around -10C) will keep high temps below
average in the lower 40s, while mostly clear skies and dry air will
allow overnight lows to dip into the mid 20s. Next chance for
precipitation remains on Saturday, though recent model runs have
started to trend farther south with the Ohio Valley system. The Euro
and GFS now show nearly all precipitation missing us to the south,
while the Canadian suggests we will receive a glancing passage of
the northernmost extent of the precip shield. Have kept chance PoPs
in the forecast as we continue to monitor how this system evolves
over the week. Increased pressure gradient will lead to a breezy
Saturday afternoon and evening. Quiet weather in store for Sunday
and Monday as ridging aloft persists and high pressure over Quebec
allows cool and dry air to filter in from the northeast.



The persistence of high pressure across northern Ontario will
sustain northeast winds across the Great Lakes into Wednesday. A
strengthening of the gradient will occur overnight as low pressure
tracks across the TN Valley. The airmass will be cold enough to
support wind gusts in the 25 to 30 knot range on Tuesday. The high
pressure will expand into the western Great Lakes on Wednesday,
causing the winds to back toward the north. Winds and waves will
slowly diminish late Wed into Thurs has the high expands across the
region. The persistent northeast winds will sustain small craft
advisory conditions into Wednesday night. Some of the strongest
winds will be Tuesday across Saginaw Bay where the northeast winds
will be channeled through the bay.


Issued at 139 PM EDT Mon Mar 19 2018


Northeast winds will persist at the terminals through the TAF period
and beyond as high pressure holds nearly stationary to the north of
the Great Lakes. A developing sfc trough over the Upper Ohio Valley
late tonight into Tues morning will support an increase in the
northeast gradient. This increased gradient overnight will inhibit
nocturnal decoupling in the boundary layer, thereby sustaining some
degree of gustiness to the sfc winds through the night. Funneling
down Saginaw Bay will continue to sustain the strongest NE winds
across MBS this afternoon through Tues. There remains some
indications in the model soundings that the moisture flux off Lake
Huron may result some strato cu development overnight. The degree of
dry air now advecting across Lake Huron from Ontario does however
reduce the probabilities for much if any overnight strato cu
development off the lake. For this reason, just a scattered low
cloud deck will be added at MBS overnight (given that the Saginaw
Valley is downstream of a longer fetch off the lake/bay).

For DTW...Recent observations and model guidance suggests a slight
backing of the winds from the ene to ne this afternoon.


* None.


Lake Huron...Small Craft Advisory until 2 AM EDT Thursday for LHZ421-441>443.

     Small Craft Advisory until 4 PM EDT Wednesday for LHZ422.

Lake St Clair...NONE.
Michigan waters of Lake Erie...Small Craft Advisory until 8 AM EDT Wednesday for LEZ444.




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