Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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687
FXUS63 KDTX 182333
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
633 PM EST Thu Jan 18 2018


.AVIATION...

Quiet aviation period during the next 24 hours for middle of January
standards. VFR conditions are anticipated throughout with dry air in
place. Vigorous shortwave maximum will push dig east of the central
Great Lakes this evening which will open the door for a greater
southwest trajectory to winds in the lower troposphere. This will
advect any residual higher theta e content from Lake Michigan
northward. Southeastern Michigan will remain in relatively close
proximity to the jet stream axis aloft, which will keep high cloud
over the region. For this reason, went fairly bullish on opaque high
cloud.

/DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 348 PM EST Thu Jan 18 2018

DISCUSSION...

Steady southwest wind will continue to lift temperatures through
another stage of the warming trend that will carry into the weekend.
Conditions will also remain dry through Saturday leaving cloud
trends as the main variable in the forecast to go along with
temperature refinement. Afternoon observations indicate a mix of
lake effect stratocu and high clouds associated with the upper
circulation moving across the northern Great Lakes. The high clouds
will move eastward with the system during early evening only to be
replaced by the cirrus expanding across the Plains today. Meanwhile,
southwest low level flow will maintain a favorable fetch across Lake
Michigan for stratocu production mainly into the Tri Cities region
but also possibly redeveloping toward the I-69 corridor. The main
question is how long boundary layer temperatures will be cold enough
for cloud production. There is usually a decrease as low level warm
advection lifts 925 mb temps above 0C over top of relatively cold
water this late in the season. However, at least partly cloudy
conditions will be required in the forecast due to the high clouds
through Friday morning, possibly trending toward mostly cloudy
during the afternoon. After morning lows around 20, these clouds
will likely cap high temperatures to the mid and upper 30s Friday
afternoon.

Moderate southwest low level flow and associated warm advection will
continue Friday night through Saturday, augmented by enhanced
surface gradient as low pressure across James Bay. Gulf modified air
off high pressure over the SE states will enter the picture by then,
moving northward across melting snow cover. Daytime satellite
imagery today indicates snow on the ground as far south as Arkansas
which will add to boundary layer moisture while melting off. Model
and MOS dewpoint projections take surface readings into the lower
and mid 30s by Saturday afternoon as stratus coverage expands over
the region which look like reasonable solutions. The difficult
aspect of this portion of the forecast will be temperature trends
Saturday night into Sunday morning. Continued southwest flow and
warm/moist advection will battle the diurnal cooling trend for
dominance and potential for temperatures to drop below freezing. It
will be a close call for the possibility of freezing drizzle,
especially in the typically colder locations of the Thumb region.

Significant increase in upper mass gradient will get underway Friday
into Saturday as east Pac jet energy releases into the northern tier
of the US against the southern periphery of the tropospheric polar
vortex Hudson Bay/northern Quebec. Trailing energy will dig into the
southwest United States Saturday through Sunday, prompting a lee
cyclogenesis episode as strong right entrance support steadily
matures through the weekend and becomes increasingly focused over
the Great Lakes region. Light warm advection/overrunning type precip
will be possible as early as Sunday morning as the low-level jet
responds and moves up the developing frontal slope. Surface cyclone
is then progged to lift from the Lower Missouri River Valley to The
Straits by Monday into early Tuesday. Strong model support that SE
Michigan will remain on the warm side of this system, supporting
temps on the milder side for late January. There is potential for
pre-fropa temps on Monday to make a run toward 50 degrees over the
southern portion of the area before showers and possibly t-storms
along the front shift through the area. Cold lake temps/ice on Lake
Erie suggest usual caveats with northward progression of the surface
portion of the warm front. Will leave out t-storms and remain more
conservative, low to possibly mid 40s, with temps for now. Per the
norm, a brief snow-fzra-rain transition is possible as the warm
front lifts through Sunday.

MARINE...

Persistent southwest flow will continue into the weekend. Winds look
to top out around 30 knots over central Lake Huron Friday evening,
but will diminish as we head into the Weekend as warm air leads to
stable profiles. A deepening low moving into the western Great Lakes
on Sunday will cause winds to become easterly and increase, but
still probably holding around 30 knots Sunday night into Monday, with
rain during this period as well.

&&

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

$$

AVIATION.....CB
DISCUSSION...BT/JVC
MARINE.......SF


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