Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 131715
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1215 PM EST Mon Nov 13 2017


.AVIATION...

Low level moisture trapped under an inversion will remain across the
region this afternoon keeping widespread MVFR stratus in place.
Light west wind will continue through the evening before gradually
backing to southwest tonight. Recent model guidance favors low level
moisture remaining firmly in place as winds remain light and ceilings
drop to low MVFR through early Tuesday morning. Potential remains
for some clearing from FNT north but have opted to keep lowering
ceilings in TAFs for both FNT and MBS through early Tuesday morning.
Have also included mention for ceilings to lower to IFR and
visibilities to MVFR late tonight as potential for fog to develop
remains questionable. Stratus is then expected to gradually lift and
scatter on Tuesday morning as mixing and low level warm advection
increases across the region.

//DTW THRESHOLD PROBABILITIES...

* High for cig aob 5kft through tonight. Low for cig aob 1kft late
  tonight. Low for cig aob 5kft Tuesday morning.

&&

.PREV DISCUSSION...
Issued at 1013 AM EST Mon Nov 13 2017

UPDATE...

As of 1010 AM EST...Tweaked forecast based on latest trends in
observations. Overall, forecast looks good with minimal changes
except to update temp and wind trends through the day based on the
latest high-res model guidance. It will continue to be a dreary day
across the region, as moisture remains trapped under a strong
subsidence inversion noted around 850 hPa. Surface high pressure will
continue to build across the region from the upper Midwest, helping
to keep this inversion locked in place. So, expecting a cloudy day
with plenty of low stratus around. A slight uptick in surface winds
should continue to mix out any remaining fog/reductions in visibility
through the rest of the morning hours. Outside of some isolated rain
showers possible over and downwind of Lake Huron, a dry forecast is
expected for southeast Michigan. High temperatures will be limited by
the extensive cloud cover, ranging from the upper 30s to lower 40s.

PREV DISCUSSION...
Issued at 311 AM EST Mon Nov 13 2017

DISCUSSION...

Low clouds socked in across lower Michigan this morning, and it
appears upper level ridge/surface high building in during the day
will not be sufficient to dislodge the low level moisture, with the
00z NAM even suggesting clouds persisting right through Tuesday
morning (see 925 RH). If low clouds do mix out this evening (See
regional GEM/GFS/Hires-NMM-east), then fog could become a concern as
surface winds look to be calm. Good low level warm advection does
not look to get going until very late tonight/Tuesday. Expecting
highs only around 40 degrees with the persistent clouds. Cloud cover
tonight will determine whether we remain above or drop below 30
degrees, and even if low clouds dissipate, some high clouds likely
streaming in after midnight as shortwave/modest 700 mb cold pool
tracks through. Ended up giving more weight toward the NAM solution
and went cloudy for much of tonight, but allowed for partial
clearing right near sunrise (see ARW), and will carry mins in the
upper 20s to around 30 for mins. If clouds hold, temps will
end up being at or above 32 degrees.

Upper level energy/trough moving onshore of the Pacific Northwest
is on track to move through the Central Great Lakes on Wednesday.
Good height falls/moisture advection/isentropic ascent as
50 knot low level jet tracks through early Wednesday. 925/850 mb
progged to reach near 4 C, and temps could make a run toward 50
degrees if the front ends up being slower, but the trends suggests
this will not be the case, and looking at mostly middle 40s
instead. Good agreement with solid/widespread line of showers with
the front during the day. Although, narrowing moisture axis expected
to preclude mention of thunderstorms, as the steep mid level lapse
rates and showalter index filtering with zero over western Ohio
Valley washes out somewhat, per 00z EURO/GFS.

Good shot of cold advection Wednesday evening/night, as 850 mb temps
fall to between -4 to -7 C. However, dry airmass at 700 MB, with low
inversion heights and unfavorable northwest flow, unlikely to see
any Lake Effect making it into southeast Michigan, with airmass
already modifying on Thursday and especially Friday as powerful
upper level low currently over the Gulf of Alaska is booted off to
the east during the mid week period, and tapping into the
subtropical Pacific Jet late in the work week, resulting in a rapid
deepening low pressure system and strong cold front tracking
through the Great Lakes Region over the Weekend. Windy conditions
and snow showers will be possible for the second half of the
weekend, as 850 mb temps look to plummet into the negative lower
teens.

MARINE...

Modest northwest winds today across all marine areas as high
pressure gradually builds into the region.  This high will slide
through the region this evening, with winds then becoming southerly
in it`s wake on Tuesday.  South winds will strengthen late Tuesday
and Tuesday night in advance of a strong cold front.  Winds will
reach 20 to 30 knots during this time, strongest over central
portions of the lake Huron open waters.  Southwest to west winds
will then gust to near-gales for a time over the open waters of
central Lake Huron on Wednesday as the cold front moves through. A
moderate post-frontal northwest wind develops Wednesday night and
Thursday.  This unstable environment will bring a period of higher
wave growth, in excess of 6 to 8 feet at times over the southern
half of the lake Huron basin.  A period of small craft advisory
conditions are likely for elevated wave heights along the lake huron
nearshore waters during this time.

&&

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

$$

AVIATION.....JD
UPDATE.......IRL
DISCUSSION...SF
MARINE.......MR


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