Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 191026
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
626 AM EDT MON SEP 19 2016

.AVIATION...

Pockets of shallow fog resulting in fluctuating visibility
restrictions across the SE Michigan airspace this morning.  Existing
conditions will lift at all terminals through 14z as daytime heating
ensues.  Otherwise, the ambient deep dry layer will hold firm
through the daylight period, well downstream of a weak cold front
slipping into northern Lower MI.  Strong stability across the lowest
layers suggest limited potential for Cu development, leaving plenty
of open sky through the day.  Modest southwest flow will emerge
today in the wake of exiting high pressure.  Inbound weak cold front
will bring a very low potential for a shower or thunderstorm
tonight. This probability currently remains too low to mention at
any terminal.  While the southwest gradient will remain stronger
than that noted tonight, potential will exist for some degree of
shallow fog development again Tuesday morning.

//DTW Threshold Probabilities...

* None

&&

.PREV DISCUSSION...
Issued at 404 AM EDT Mon SEP 19 2016

DISCUSSION...

Light winds and clear skies under surface high pressure has allowed
areas of fog to form again this morning. The character of this fog
over the next several hours should be similar to last night, with
transient fog causing rapid fluctuations in visibility. Band of high
clouds over western Michigan will track east through the remainder
of the early morning. Upstream surface observations have shown some
improvement to visibilities as the high clouds work across, and
expect similar trends here.

Energy embedded within a longwave trough encompassing much of Canada
will split early in the forecast period, with one large upper wave
passing east across Ontario and Quebec, and another dropping into
the Pacific Northwest. Energy riding along the base of this first
wave will track from the Northern Plains and across the Northern
Great Lakes late today and tonight, riding along a 140kt upper jet
pushing the northern U.S.. Surface ridge over Southeast Michigan
will sink southward today as a cold front associated with the system
to our north gradually progresses south. The front should push
through Southeast Michigan during the overnight hours, per GFS/Euro
solutions. GEM/NAM/NMM remain slower with the frontal passage, and
this could warrant some consideration for lingering pops into
Tuesday. Upper support for the front (upper height falls, upper
divergence ahead of jet) looks to remain north of the area, and
given frontal passage outside of daytime heating hours, will
maintain inherited low-end pops. Improved mixing ahead of the front,
mostly sunny skies, and H850 temps of 15-17C should provide a warm
day with highs in the low to mid 80s. This is 10-13 degrees above
normal.

Surface high pressure will become centered over Lower Michigan by
late afternoon Tuesday, and remain overnight in response to building
heights over the Plains. This should bring dry and stable conditions
(unless the front slows down...see paragraph above) into Wednesday.
Temperatures will not cool too much behind the front, especially as
southerly flow is quick to become reestablished by Wed. Max temps
both days should run fairly close to 80 degrees.

Upper low will remain over Hudson Bay and Quebec from mid-week into
the first part of the weekend. A fairly large shortwave looks to be
guided across Ontario Thursday into Friday, sending a cold front
slowly southward through Michigan per latest Euro/GFS. A few waves
with tropical Pacific origins are expected to lift up into the Great
Lakes ahead of another upper low working through the western U.S.,
and track over the frontal boundary. At this time, models have the
front placed to our north as this occurs, which would focus the
heavier rain to our north.

MARINE...

Southwest winds will strengthen today in the wake of high pressure
drifting to the east.  The strongest gradient will exist immediately
in advance of a cold front, focusing some stronger gusts over
portions of northern and central Lake Huron through the daylight
period.  Wind speeds up to 20 knots can be expected across the
corridor.  A weak cold front will drop across the area tonight,
bringing low chances for showers and possible a thunderstorm.  Winds
behind this front will shift to west and weaken by midday on
Tuesday.  Light southerly winds in place Wednesday as high pressure
shifts across the region.

&&

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

$$

AVIATION.....MR
DISCUSSION...HLO
MARINE.......MR

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



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