Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 172026
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
326 PM EST Tue Jan 17 2017

.DISCUSSION...

Surface wave to exit to the northeast early this evening.  Moist and
milder low level environment left in it`s wake, the evening period
still governed by low-mid level west to southwest flow. Trailing
axis of weak convergence will pivot back into the forecast area
early tonight.  This may allow for some renewed pockets of light
rain or drizzle, particularly north of I-69 as deeper moisture wraps
back around the departing low.  Northern periphery of a progressive
northern stream wave on track to then glance across lower Michigan
overnight. Period of modest deformation forcing will emerge through
the early morning hours.  Brief increase in moisture depth across
the 800-650 mb layer tied to this feature, translating into at least
a chance of light precipitation production all locations.  This
moisture strips out northwest to southeast 07z-10z, likely just
before a slowly cooling thermal profile could become supportive of a
transition to snow.  Persistent high moisture content down low may
transition the precipitation mode to drizzle for a time through mid
morning.  Window for possible freezing drizzle appears narrow as
well, with low temperatures likely bottoming out right at or just
above freezing from the M-59 corridor northward.

Increasing amplitude within the southern stream upper height field
will yield a stretch of relatively benign weather conditions locally
during the remainder of the midweek period.  Cloud trends likely
still an issue, particularly Wednesday as retention of a northwest
to westerly flow maintains a high degree of moisture beneath the
inversion.  Increasing subsidence and dry air advection above will
work to erode this moist layer, particularly by afternoon where some
breaks in the cloud deck may begin to emerge.  Otherwise, looking at
a continuation of above normal warmth, as even neutral temperature
advection of the resident air mass yields afternoon readings of
upper 30s/lower 40s. Combination of rising upper heights and the
emergence of weak warm air advection will nudge temperatures up
another category Thursday.  Daytime readings arriving in the lower
and middle 40s.

An upper level low lifting northward through the Central Plains
on Friday will bring a chance for rain to Michigan as a band of
vorticity and weak surface low lifts northward through the Great
Lakes. Some uncertainty remains among model solutions regarding
PoPs. ECMWF favors a higher chance of rain on Friday with a stronger
wave and surface low lifting northward. GFS/CMC favor lower chance
for rain on Friday with a weaker low. After passage of the wave on
Friday, a trough amplifying in the Plains over the weekend will keep
southerly flow in place over the Great Lakes bringing unseasonably
mild temperatures with highs in the 40s to near 50 through Sunday.
Low pressure developing in the Southern Plains will eject northward
into the Ohio Valley on Monday bringing another chance for rain to
Southeast Michigan as moisture surges northward with warmer air
remaining in place. Model solutions then indicate ridging builds
again early next week over the Eastern US keeping mild conditions in
place.

&&

.MARINE...

A surface low is currently centered over southern Lake Huron and
western Lake Erie and will continue to track eastward away from the
Great Lakes. High pressure will build into the region in its wake
allowing the pressure gradient to relax. Current northeast flow will
becomes southwesterly on Wednesday and will usher in a more stable
airmass over the waters. Winds will remain below 20 knots tonight
and Wednesday before a slight increase toward 25 knots Wednesday
night when the next trough swings through.

&&

.PREV DISCUSSION...
Issued at 1255 PM EST Tue Jan 17 2017

AVIATION...

The center of a low pressure system is current tracking through SE
MI leading to varying conditions across the region. An occluded warm
front is starting to lift north of the MI/OH border which should
bring improving conditions (MVFR) into the afternoon hours, but IFR
conditions will continue for most locations until then. One question
is, will the boundary lift north of PTK or not? Should be close to
the PTK to PHN line. CIGS look to be locked in around 300-400 feet
for the next few hours under the low but could lift near 1000 ft as
drier air moves in with increasing SW flow. Fog has developed north
of the boundary and should persist through about 20Z. Conditions
will deteriorate again this evening as a secondary wave slides
through the area. Expect mostly IFR conditions through tonight.

For DTW... The occluded front is just south of the terminal which
means fog and LIFR cigs will continue another hour or so. Conditions
may then improve to MVFR for a brief period before IFR returns for
the evening and overnight.

//DTW Threshold Probabilities...

* High for ceiling below 5000 ft through the TAF period.

* Low for ceiling and/or visibility below 200 ft/one half mile.

* High in precip type being all rain today.


&&

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

$$

DISCUSSION...MR/JD
MARINE.......DRK
AVIATION.....DRK


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