447
FXUS63 KDTX 300906
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
506 AM EDT Mon Sep 30 2024

.KEY MESSAGES...

- Some fog potential early Tuesday morning as moisture is drawn
  north in advance of approaching cold front.

- The next chance of showers and a few thunderstorms will come on
  Tuesday afternoon as this front crosses the area.

- Seasonal temperatures can be expected through the upcoming week.

&&

.AVIATION...

A sharp south to north moisture gradient is present across southeast
Michigan, and with light northeast-east winds continuing today, the
gradient remains in place. This will translate to more clouds and
lower cloud bases across the southern TAFS, with mostly ceiling
free skies over MBS. Moisture flux from Lake Erie will also help add
to the low level moisture, and looking at MVFR cigs over DTW/YIP to
persist much of the day, after the expected IFR cloud deck around
sunrise lifts. Scattering out of the low clouds or lifting into
VFR for the Detroit Metro Area late today/early this evening. The
potential will then exist for dense fog to develop late tonight,
dependent on how much clearing takes place in the evening. At this
point, sct-bkn 2500-5000 foot clouds may persist, and then just
lower through the night with light and variable winds. Would expect
close to a repeat performance to this morning, but better chance
for a visibility reduction with less wind.

For DTW/D21 Convection...Thunderstorms are not expected.

DTW THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet today, medium tonight.

* Very low confidence in cig aob 200 feet and/or vis aob 1/2sm 9-13z
  Tuesday.

&&

.PREV DISCUSSION...
Issued at 301 AM EDT Mon Sep 30 2024

DISCUSSION...

Expansion of stratus so far early this morning has been subdued by
the introduction of drier air working back west into the area from
southern Ontario within northeast to east flow around high pressure.
Moisture flux from the Great Lakes should continue to counteract
this drier air to some degree and lead to greater cloud coverage by
daybreak. Thereafter, low level winds veer to the east and southeast
with time today allowing a better influx of broader moisture into
the area with increasing cloud cover through the morning gradually
mixing out into the afternoon/evening.

Better fog/stratus potential will set up overnight tonight as winds
become southerly and low level moisture poised along the southern
periphery of the Great Lakes works north through the area in advance
of approaching cold front. This front is being driven east into the
region by the southern extension of a rather strong shortwave that
will be sweeping across southern Canada early this week. Given the
northern positioning of this main system, forcing along the front
will diminish from north to south across the forecast area and have
an impact to shower coverage/chances with likely to categorical
coverage expected over the Thumb diminishing to scattered shower
activity further south. Will maintain a mention of thunder as well
large scale lift along the front should counter what are overall
pathetic mid level lapse rates and at least bring the potential for
a rumble or two of thunder.

High pressure will then bring dry conditions on Wednesday and
Thursday with another chance of showers expected on Friday with the
next cold frontal passage. This front will be moisture starved and
the mid level shortwave driving it is of modest amplitude so this
activity should remain minimal. This cold front will be followed by
another by Sunday with similar shower isolated to scattered shower
chances.

High temperatures will oscillate from the mid 70s in advance of the
various cold frontal passages during the upcoming seven day forecast
to mid/upper 60s within minor cold pools that shift over the region
in their wake.

MARINE...

High pressure will continue eastward today while becoming centered
over Quebec and still prevailing over the Great Lakes. The new
position farther east will force the gradient flow to be more
easterly than northeasterly further helping the lakes relax from the
recent elevated winds and waves. Winds will veer to the south on
Tuesday as a cold front connected to a strong low passing well north
of the region over Hudson Bay. The cold front will pass over the
region later on Tuesday producing the chance of rain. Winds will
then flip around to the northwest behind the front heading into
Tuesday night. The colder unstable air may result in gusts up to 25
to 30 knots and elevated wave heights so marine headlines may be
needed.

HYDROLOGY...

A cold front will bring up to one quarter of an inch rainfall to the
area on Tuesday with the greatest coverage expected over the Thumb
region. A few thunderstorms may also bring very localized pockets of
heavier rainfall. There are currently no flooding concerns with this
precipitation.

&&

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

$$

AVIATION.....SF
DISCUSSION...DG
MARINE.......DG
HYDROLOGY....DG


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