Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 270457

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1157 PM EST Sat Nov 26 2016


The cloud forecast for the remainder of tonight is a noisy one with
a plethora of outcomes suggested in the nwp suite. Targeting a
couple of things happening: 1. enhanced pre-existing saturation and
RH at 850-800mb is forcasted to exit the area to the north and east
after 09Z. 2. low level theta e advection is forecasted to push into
west central sections of lower Michigan later tonight. So, expecting
the MVFR cloud that now exists to scatter out and dissipate as the
moisture axis departs to only be replaced north of the Detroit Metro
area as the theta e increases. Probability of lower cloud lingering
at the Detroit sites is less but then raises some question on fog
formation. Surface dewpoints trends and MOS are not overly
supportive of fog and will not go overboard on the mention.

aT DTW...The latest HRRR solutions have backed off on the low cloud
and fog potential at DTW Sunday morning. Better potential for MVFR
cloud will exist north of the terminal and will use a tempo group
for stratus this morning.

//DTW Threshold Probabilities...

* High for ceiling 5000 ft this evening...medium to high for late
  tonight through Sunday morning.


Issued at 305 PM EST Sat Nov 26 2016


Fairly quiet stretch of weather expected for the second half of the
weekend as the upper ridge now over the central CONUS slides into
the Great Lakes. Most challenging aspect of the forecast will be
cloud cover. Expect to see a reduction in clouds this evening as the
surface ridge axis passes over the area. This will weaken and back
flow across the lake and lower inversion heights, allowing clouds to
release from Lake Michigan. Trend can already been seen on satellite
imagery to our west. Latest high-res model data from the
HRRR/RAP/NAM then suggests that the lowering inversion heights will
serve to trap moisture arriving overnight behind a weak warm front.
This moisture is already apparent over Illinois and Missouri, with
surface observations reflecting the presence of low clouds and some
fog. There should be enough of a southerly gradient over Southeast
Michigan overnight to favor stratus over fog, as the ridge center
remains to our south. Cannot rule out a few patches of drizzle, but
will leave out of forecast for now as overall potential and any
impacts (non-freezing) look low. The clouds will keep temperatures
from falling too far from current readings overnight, with mins
expected to settle in the low or mid 30s. Moisture will linger into
tomorrow, with a slow lifting and thinning of cloud bases expected
through the day as mixing improves with the diurnal cycle. Will
stick with some of the cooler numbers in the mid 40s offered by
guidance for max temps.

Longwave trough will become established over much of U.S. Monday, as
energy now along the West Coast and the Gulf of Alaska consolidates.
A strong shortwave embedded within this trough will lift northeast
across Michigan Monday night and Tuesday, while we also become
positioned under strong upper diffluence in advance of strong
subtropical jet streak. Strong low-level jet will pull a good deal
of warm air and Gulf moisture (PW near 1 inch) into the Great Lakes
Monday into Monday night, working with large-scale forcing to
provide steady rain to the area. Drier air will rush into the area
as the low lifts into the northern Great Lakes on Tuesday, ending
chances for precipitation from south to north, but keeping a very
mild airmass in place.

The upper level large low centered over the Northern Plains will
continue to meander over the area for the remainder of the week. In
the meantime, the surface low will be in the process of lifting away
from the area.  This will bring a chance for some showers along with
periods of drier weather through the week even as the region remains
in upper level troughing. Temperatures on both Tuesday and Wednesday
will be above normal as highs reach into the 50s before highs drop
back into the lower 40s for the beginning of December.


Marine conditions will remain favorable as high pressure drifts
across the Great Lakes tonight and then to the east Sunday.
Meanwhile, a large low pressure system will organize over the
central Plains states and then strengthen considerably over the
northern Plains and Midwest Monday through Tuesday. This system will
support a fresh southeast breeze from Lake Huron through western
Lake Erie Monday and likely reaching gales Monday night. The latest
model solutions indicate a deeper layer of instability over Lake
Huron ahead of the warm front/occlusion which could allow gales to
reach 40 knots before the occlusion moves north of the lake Tuesday.
Small craft advisories will likely be needed Monday, mainly for
waves on southern Lake Huron, ramping up to Gale watches now in
effect for all marine areas Monday night into Tuesday. Wind
conditions are projected to improve Tuesday night into Wednesday as
milder air and more stable conditions move over the region.


Lake Huron...Gale Watch from Monday evening through Tuesday afternoon FOR

Lake St Clair...Gale Watch from Monday evening through Tuesday morning FOR LCZ460.

Michigan waters of Lake Erie...Gale Watch from Monday evening through Tuesday morning FOR LEZ444.




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