Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 140744
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
344 AM EDT Thu Sep 14 2017

.DISCUSSION...

Main concern to start the morning is the development of dense fog
across parts of the area. Widespread dewpoints in the upper 50s and
lower 60s, clearing skies, and calm to light winds are providing a
good environment for fog development. Dense fog has already
developed along the I-69/I-75 corridors and southwestward into
Lenawee County where less cloud cover has allowed better radiational
cooling. Have issued a Dense Fog Advisory through this morning for
these areas and it may need to be expanded if fog develops further
to the east.

The heavier shower activity associated with the remnants of Irma
remained to the south through the night. The circulation will
progress further eastward throughout today as a weak upper ridge
takes over. A few leftover clouds are expected to clear throughout
the afternoon as a surface high pressure builds to our southeast.
Forecast high temperatures will be similar to yesterday with many
locations in the mid to upper 70s, which is at or above normal for
this time of year.

Fog could be a possibility late Thursday night into Friday morning.
Conditions look to be favorable again for development as the
elevated dewpoints and light winds will remain with overnight
temperatures forecast to drop into the mid to upper 50s. Will go
ahead and introduce some patchy fog into the forecast. Otherwise,
gorgeous weather is in the forecast heading into the weekend with the
upper ridge in place. Warming temperatures at 850mb will lead to
high temperatures increasing into the 80s for most locations for
Saturday and Sunday. A shortwave trough crossing the northern plains
on Sunday will shove a cold front through the Great Lakes and bring
with it our next chance for rain. Best chances at the moment look to
be later Sunday evening and overnight as the front pushes through.
Some lingering showers behind front are also possible through the
morning hours on Monday. Temperatures for Monday will drop out of the
80s and back into the mid to upper 70s in the wake of the front.

The cloud cover associated cloud cover and rain chances associated
with the front are not expected to stick around long as we again
will be under the influence of upper ridging. Temperatures will be
trending warmer again into midweek. Models diverge a bit on the upper
level pattern and how they handle the upper trough over the western
CONUS during this time as well. Depending on which one plays out, we
could see some more rain chances around mid week. Will keep rain chances
on the dry end until there is more agreement.

&&

.MARINE...

With the large upper level low pressure system now pushing east of
the region, ridging will again take hold of the central Great Lakes
for the end of the week and weekend. A low pressure system will then
develop over the high Plains leading to a strengthening pressure
gradient over the western and central Great Lakes by this weekend.
Some uncertainty exists with regards to timing of gusty southerly
winds. At this time, southerly winds are expected to increase into
the 10 to 20 knot range by Saturday, particularly for those offshore
waters across the central and northern Lake Huron basin. Shoreline
areas appear to remain around the 10 knot threshold at least for the
next few days.

&&

.PREV DISCUSSION...
Issued at 1203 AM EDT Thu Sep 14 2017

AVIATION...

The mid and high cloud distribution will continue to govern the pace
of fog development during the night. A band of mid clouds is
expected to dissipate in the MBS area and allow radiational cooling
to accelerate toward sunrise. Meanwhile, only scattered coverage
over the FNT to PTK area is expected to allow earlier development
which could lead to borderline IFR/LIFR restriction by sunrise. A
typical cycle of improvement will then follow through late morning
transitioning to VFR during afternoon into Thursday evening.

For DTW... Scattered coverage of high clouds could allow an earlier
start to fog formation, although meaningful coverage of mid clouds
and even stratus is expected to return from the northwest flank of
Irma remnants. This casts uncertainty on timing and density of fog
through mid morning with borderline MVFR/IFR restriction most
favored before late morning improvement begins.

//DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 feet or less late tonight through
  mid afternoon.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Dense Fog Advisory until 10 AM EDT this morning for MIZ060-061-068-
     069-075-082.

Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

DISCUSSION...AA
MARINE.......CB
AVIATION.....BT


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