880
FXUS63 KDTX 161706
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
106 PM EDT Wed Apr 16 2025

.KEY MESSAGES...

- Dry weather today and Thursday with temperatures falling into the
  mid to 20s to lower 30s tonight.

- Warm front brings showers and possible thunderstorms Thursday
  night, leading to a much warmer day on Friday with highs in the
  70s.

- There is a slight risk of severe thunderstorms Friday evening, but
  exact timing of a cold front will be the key, as much of Friday
  looks to be dry and capped.

&&

.AVIATION...

High pressure influence has manifested across the terminals this
afternoon providing a marked improvement in ceilings as MVFR
stratocumulus has since scattered-out. This leaves a sparse/patchy
cumulus field for the rest of the diurnal cycle as upper-level
stability/subsidence maintains a dry atmospheric column into
Thursday. Northwesterly winds gusting 20-25 knots decrease
significantly by this evening, becoming light and variable late
tonight into Thursday. A period of SKC is expected before high
cirrus starts to spill in Thursday morning while maintaining VFR
conditions through the TAF period. Surface flow organizes from the
south-southeast Thursday as surface ridging departs ahead of inbound
low pressure moving across The Plains.

.DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 352 AM EDT Wed Apr 16 2025

DISCUSSION...

Highly confluent upper level flow/subsidence in place today, leading
to very dry airmass, with PW values dipping just below 0.2 inches,
approaching record low values for mid April. The mid april
insolation will help boost temps into the lower 50s. However, with
late day dew pts in the lower 20s and the ridge axis arriving by
midnight, a cold night is expected as calm winds and clear skies lead
to temps in the mid 20s to lower 30s. An increase in high clouds
late tonight could disrupt the radiational cooling slightly.

Big pattern reversal to take place over the Rockies, as the upper
level ridge is replaced by significant upper level wave/trough
descending south from western Canada, merging with upper level
low/energy off the California. Strong southwest low level jet
exiting the Central Plains on Thursday will transport a good deal of
moisture into southern Lower Michigan, with the deep moisture/850 MB
Theta-E ridge arriving Friday morning. Excellent moisture advection
with the warm front Thursday night should bring widespread showers as
850 MB dew pts reach and slightly exceed 10 C. Although, the
heaviest activity likely remains northwest of the CWA as the low
level jet core appears to be just a bit to far to our west. Based
off the 00z Euro ensembles, the highest probability (90 percent) for
rainfall to exceed a tenth of an inch of rain is over Tri-Cities
region and over Huron county, with a 15-20 percent chance to exceed
half an inch, per Euro ensembles.

The forecast for Friday is even more uncertain, as the strength of
the surface low tracking near/along Wisconsin/Illinois, northeast
into central/northern Lower Michigan by evening is in question, as
seen in the Euro ensemble members. The overall weakening trend
appears to be the consensus however. Excellent mid level (700-500
MB) lapse rate coming out of the Midwest with K indices lowering
into the mid negative single numbers, coupled with a high degree of
wind shear (0-6 KM shear of 50+ knots) draws concern for severe
storms, with the potential late day/early evening timing. However,
the mid levels are warm (9 C at 700 MB) and very dry, and southeast
Michigan should be capped for much of Friday. Likely will need to be
close and north of the surface low track to support
showers/thunderstorms, and right now that looks to be north of M-46.
Thus, the Detroit Metro area looks to get into the warm sector with
good southwest low level flow and with 850 MB temps potentially
reaching 13 C, high temperatures around 80 degrees become in play,
but low clouds may struggle to dissipate which would hinder the
maxes.

The associated cold front to swing into southeast Michigan toward
midnight, and the airmass should be stabilizing (MLcapes 1500-2000
late afternoon...cut in half), but with 50 knots of flow at the 850
MB level, damaging wind gusts are possible if the front comes through
faster. Operational 00z Euro is even a bit slower with the front and
would limit severe storms. With that said, SPC day 3 outlook
indicates a slight chance of severe thunderstorms for southeast
Michigan.

Cooler for Saturday as 850 MB temps lower into the low single
numbers behind the front and as high pressure builds through the
northern Great Lakes. This high will give way to another strong low
pressure system tracking through the western Great Lakes Sunday
night, bringing another round of showers and possible thunderstorms
to end the weekend.

MARINE...

Gradient over the central Great Lakes continues to weaken this
morning as low pressure pushes into eastern Quebec and surface high
pressure builds in from the Midwest. Gale Warnings have been allowed
to expire across the bulk of the region though a few borderline
gales could still linger over north-central Lake Huron early this
morning where the gradient is slowest to loosen. Otherwise, NW winds
maintain a steady weakening trend through the rest of today as high
pressure becomes fully established. Said high drifts directly
overhead tonight offering a period of light and variable winds going
into Thursday morning. Southeast winds then increase latter half of
Thursday in response to the next low lifting out of the central
Plains towards the Great Lakes. Milder airmass supports stronger
overlake stability which is expected to keep gusts at or below
25kts. Low tracks through Friday-Friday night bringing widespread
rain and the chance for thunderstorms, including severe storms, in
advance of its attendant cold front late Friday evening.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-422-
     441>443.

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

$$

AVIATION.....KGK
DISCUSSION...SF
MARINE.......KDK


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at www.weather.gov/detroit.