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000
FXUS63 KDTX 100359
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1159 PM EDT Tue Apr 9 2024

.KEY MESSAGES...

- A stray shower or thunderstorm remain possible near the Canadian
border during late afternoon as a weak cold front crosses SE
Michigan.

- Dry weather and slightly cooler temperatures move in with weak
high pressure Wednesday.

- A large low pressure system is on schedule to move in with a
prolonged period of rain showers through late week. Showers increase
coverage and intensity Wednesday night with the heaviest rain
continuing through Thursday and Thursday night.

- Windy and colder conditions accompany rain showers that linger
through Friday. Temperatures struggle to rise out of the 40s.

&&

.AVIATION...

Widespread VFR conditions are expected throughout much of period,
through 00Z Thursday. The next low pressure system will bring
northward moisture transport, MVFR conditions and rain after 00Z
Thu. Northwest winds today will become southerly during the daytime
Wednesday, backing out of the southeast for Wednesday evening.

For DTW...VFR tonight and Wednesday. MVFR with rain is expected to
move into DTW by 03Z Thursday.

.DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 357 PM EDT Tue Apr 9 2024

DISCUSSION...

A cold front crossing the area sharpened up just enough for the
formation of a modest line of showers by late morning. Hourly
mesoanalysis revealed steep 700-500mb lapse rate near 8 C/km as a
tipping point for activation while the 850 mb theta-e ridge made up
some ground on northward progress ahead of the front. Surface
analyses also indicate a similar northward move carrying Td into the
lower to mid 50s. This gives the initially elevated frontal
convection a chance to tap into surface based CAPE near 1000 J/kg at
the last moment before the front exits into Ontario by sunset.

After the cold front, respectable low level cold advection lasts
much of tonight leaving the thermal trough SW-NE over Lower Mi by
sunrise Wednesday. This will bring high temperatures down several
degrees from today, although guidance is still lower to mid 60s vs
lower to mid 50s normal readings for early April. Mid level
subsidence and surface high pressure ensure dry weather and a mostly
sunny morning until high clouds thicken during the afternoon which
also keep temperature overachievement in check.

The increasing clouds Wednesday afternoon lead to a gradual south to
north onset of rain showers Wednesday evening which mark the
beginning of a rainy pattern expected to cover much of the late week
period. Today`s cold front extends southward to the Texas low
pressure system projected to move up the MS River valley Wednesday
and Wednesday night while the leading frontal zone remains highly
organized and moisture rich. The northward track of the system
returns strong moisture transport back into Lower Mi ahead of the
surface low and mid level wave. If there is a model trend in the 12Z
cycle it is slower northward timing by a few hours, although
dprog/dt on bulk 500 mb features shows very good run-to-run
consistency on the depiction of initial phasing with the northern
stream. After that, consensus of deterministic model solutions show
a transition from moisture transport/isentropic lift to a NW flank
deformation pattern over Lower Mi Thursday into Thursday night. This
occurs with a deep and plentiful moisture supply that is borderline
tropical in nature as shown by 850 mb Td near +10C and 700 mb Td
well into the lower single digits. Occurrence of a 1 to 2 inch QPF
axis is likely but with a location highly dependent on the eventual
character of mid level wave phasing and surface low track.
Preponderance of model evidence suggests greater intensity of the
low pressure system with a farther north/west track while keeping in
mind the usual suspicions of over-development due to QPF/diabatic
heating "feedback". A dry slot induced break in coverage is then
projected for much of Thursday leading into the wrap-around
occlusion phase Thursday night, again assuming the more intense
negative tilt solution holds in upcoming forecast cycles.

The week finishes up with windy and sharply colder conditions as
this large low pressure system exits the region Friday. It`s not
cold enough for snow, but readings stuck in the 40s with 40 mph wind
gusts will feel like winter. This leads to a relatively quick
temperature recovery this weekend as zonal large scale flow returns
to the Great Lakes region.

MARINE...

Weak frontal boundary has generally stalled from Georgian Bay to
Harbor Beach to Adrian, with a gradual eastward drift expected
through the evening. Afternoon peak heating window is ongoing, so
isolated shower and thunderstorm potential is still in play for
southern Lake Huron, Lake St. Clair and western Lake Erie through
sunset. Lightning will be the main concern with any storms. High
pressure then fills in Wednesday but is short-lived as a stronger
low pressure system lifts into the Great Lakes from the Gulf
Thursday and Friday, drawing a plume of deep moisture and widespread
rain into the area both days. Seasonable warmth of the airmass keeps
conditions stable through Friday, but as winds shift northwest
Friday afternoon, expect gusts to tap into their full potential with
increasing confidence in a period of gales latter half of Friday.

HYDROLOGY...

A large low pressure system will bring widespread soaking rain to
the Great Lakes from Wednesday night through Thursday and Friday.
Intervals of moderate to locally heavy rainfall are likely,
particularly from late Wednesday night through Thursday night. Total
rainfall in excess of 1 inch is expected, with upwards of 2 inches
possible should repeated rounds of higher intensity rainfall move
across the same locations. This amount of rain will lead to rises on
area rivers and ponding on roadways. While widespread flooding is
not expected, minor flooding of prone urban and poor drainage areas
will be possible.

&&

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

$$

AVIATION.....CB
DISCUSSION...BT
MARINE.......MV
HYDROLOGY....BT


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