635
FXUS63 KDTX 230947
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
547 AM EDT Mon Sep 23 2024

.KEY MESSAGES...

- Seasonable temperatures through the early and mid week period.

- Showers are likely Tuesday and Tuesday night, with a slight chance
of non-severe thunderstorms.

&&

.AVIATION...

With rain transitioning to drizzle early this morning and a post-
frontal shift to north flow at the surface, lake modification
reinforces the presently saturated low-level environment. This lends
higher confidence in the continuation of a mix of IFR and MVFR low
stratus for a couple more hours before ceilings lift more broadly to
MVFR. Presence of such stratus does favor less fog and visibility
reductions this morning. High pressure influence arrives after 15Z
today which slowly works to dry the boundary layer, but any recovery
to VFR will be brief before ceilings crater back to MVFR/IFR
overnight. The next warm front ensures non-VFR conditions through
Tuesday morning.

For DTW/D21 Convection...A couple rumbles of thunder are possible
Tuesday morning with the approach of another warm front.

 DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet through most of the
  forecast period.

* Low for thunder after 11Z Tuesday.

&&

.PREV DISCUSSION...
Issued at 314 AM EDT Mon Sep 23 2024

DISCUSSION...

Southeast Michigan will reside between high pressure across the
northern great lakes and a stalled frontal zone over the Ohio valley
to start the work week. Higher quality low level moisture left in
the wake of an exiting low pressure system ensures plentiful cloud
cover through at least the first half of the day. Some late day
breaks plausible as ongoing drying in low level northerly flow works
to capitalize on diurnal mixing. Overall moisture quality lacks
depth to suggest a more meaningful rainfall chance is possible, but
can`t rule out a few stray showers mainly across the thumb region.
Notably cooler relative to recent days, but still within the range
of average for late September. Highs upper 60s to lower 70s.

Mid level wave noted on water vapor ejecting across the central
plains early this morning on pace to arrive locally Tuesday. This
trajectory will draw the elevated frontal zone into the area,
establishing a focus for some light shower production as early as
late tonight and Tuesday morning under modest isentropic ascent.
Pockets of showers will continue to manifest late Tuesday into
Tuesday night as the inbound height falls and attendant surface low
impinge on the area. Higher precip probability edged toward the
south given closer proximity to both better moisture depth and
forcing.

Trailing mid level wave will gradually amplify across the region
heading into Wednesday. Depending on the eastward pace of the
frontal zone, this could afford a secondary response. Latest NBM
guidance holding firm with a dry forecast this period. Seasonable
resident thermal profile will continue to mark conditions, with an
elevated dewpoint maintaining a relatively humid environment.
Emergence of deeper layer northwest flow within the backside of the
exiting high amplitude trough will then establish a more meaningful
drying trend Thursday, with low-mid level ridging supporting dry
conditions and a moderating trend to finish the work week. Expansive
closed low positioned south of the area will be influenced by a
tropical system/moisture rotating through the expansive periphery,
eventually opening the door for some impact locally toward next
weekend or early next week as the large scale feature finally
releases eastward.

MARINE...

North-northwest flow will gradually veer to the northeast through
the day today in the wake of a cold front. Modest mixing depths and
a tightening pressure gradient in response to a departing low
pressure system will support sustained winds shy of 20 knots across
Lake Huron, with gusts to or below 25 knots. This will bring
elevated wave heights around the tip of the Thumb, where Small Craft
Advisories are in place.

A ridge will fill back in later this afternoon through early
tomorrow morning, lowering wind speeds and bringing dry weather.
This will quickly be disrupted by a second low pressure system which
moves over central Michigan tomorrow evening to Wednesday morning.
This will bring another round of widespread rain showers, with some
possible thunderstorms.

HYDROLOGY...

Low pressure system tracking through the region will bring a good
chance of showers Tuesday and Tuesday night. Isolated thunderstorms
also possible Tuesday afternoon and evening. Basin average rainfall
between one quarter and one half inch. No flooding expected.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-441.

     Small Craft Advisory from 10 AM this morning to 10 PM EDT this
     evening for LHZ442-443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....KGK
DISCUSSION...MR
MARINE.......AM
HYDROLOGY....MR


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