Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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117
FXUS63 KDTX 271043
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
643 AM EDT Mon Mar 27 2017


.AVIATION...

Ample low level moisture circulating around a broad sfc low centered
over Lake Huron and enhanced convergence along a sfc trough axis
over SW Lower Mi has sustained frequent intervals of IFR and lower
ceilings and visibilities across the area. The enhanced low level
convergence is also supporting some light showers/drizzle which will
persist over the next couple hours. The sfc trough will hold nearly
stationary across Se Mi through the afternoon. With lingering low
level moisture in place, this will result in a persistence of
stratus/strato cu. Diurnal heating will lead to a slight rise in the
ceilings heights during the course of the day, although bases are
likely to remain MVFR.

For DTW...There has been increasing variability in ceiling heights
upstream, but predominate IFR conditions looks to hold with some
areas of drizzle through 14 or 15Z.

//DTW THRESHOLD PROBABILITIES...

* High for cigs below 5000 feet through the TAF period.

&&

.PREV DISCUSSION...
Issued at 332 AM EDT Mon Mar 27 2017

DISCUSSION...

Surface low is now centered over lower MI as it continues to slowly
lift northeastward through the region. The surface low has been
weakening while the stacked mid level low also weakens into an open
wave. Though the bulk of any precip with the system has ended, we
will remain in a very moisture rich environment through the morning
resulting in patchy fog and isolated light showers in the trailing
trough. Winds becoming more southwesterly are ushering in drier air
which will work northward through the morning drying out the low
levels for a while. The drier air will help raise ceiling heights
today but ample moisture beneath the inversion will take a while to
scour out, and by the time it would later this evening the next
system will already be spreading clouds back into the mid/high
levels. So forecast will remain cloudy.

Will not get much of a break before the next system brings the next
batch of showers to southern lower MI. This next mid level wave
embedded in the active southern stream of the jet is over the
Central Plains and will track through the Ohio Valley Monday night
into Tuesday. Some interaction with a weak northern stream trough
digging down into the Great Lakes is leading to model differences as
to northern extent of the precip shield with this low. There is a
lingering trough axis laid out by the exiting low in conjunction
with the approaching lead band of isentropic ascent which could get
compressed by the sinking northern stream trough. Working against it
all will be the wake subsidence from the exiting low not to mention
all factors being fairly weak. Will continue to hit more on the
deformation forcing tied more closely to the low itself as the main
player with the previously noted features further north being
secondary. Pops will highlight this with chance/likely pops moving
in Monday night closer to the Ohio border with only slight chance
across the I69 corridor.

After this second low passes east Tuesday morning, we`ll see a quiet
stretch the rest of Tuesday through Wednesday night as Canadian high
pressure builds across the region. The high will be centered to our
north keeping us in the cool easterly flow through this time. This
will merely temper the possible warming of the late March sun
keeping temperatures near seasonal averages in the low 50s. With the
northern stream of the jet locking the cold air well to the north,
and the active southern stream skirting us to the south for the most
part, we reside in a region with little thermal adjustments
occuring.

The active southern jet will send yet another trough into the GReat
Lakes late Thursday through Friday night. This is a deeper trough
with stronger surface reflection thus long range models are in fair
agreement so far. Looks like another wet stretch with the low
lifting through southern MI while reaching its mature phase. We can
try to iron out more precise timing with future forecast cycles.

MARINE...

Ample low level moisture associated with low pressure slowly
tracking across Lake Huron this morning will support marine fog on
the lake. A little low level dry air advection in the wake of the
sfc low will aid in scouring out marine fog this afternoon. There
will also be a cold front pushing across Lake Huron from the north
during the afternoon. This front will then slide south across Lakes
St Clair and Erie tonight. An abrupt switch to a northerly wind
direction will occur along this front. High pressure will expand
across the northern Great Lakes Tuesday into Tuesday night. This
will support increasing northerly winds, possibly gusting over 20
knots at times across southern Lake Huron and Lakes St Clair and
Erie. This will support a chance that some small craft advisory
conditions may develop on the southern Lake Huron basin on Tuesday.
Strong high pressure to the north and east of the region will
maintain an easterly wind component into Friday. Low pressure
forecast to lift into the Ohio Valley by Friday will in turn lead to
a tightening gradient and thus increasing winds.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....SC
DISCUSSION...DRK
MARINE.......SC


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



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