Pontiac, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

932
FXUS63 KDTX 080913
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
513 AM EDT Tue Apr 8 2025

.KEY MESSAGES...

- Winter-like temperatures and wind chills today and tonight.

- A mix of rain and snow is expected over much of the area late
  Wednesday through Thursday.

- Warmer temperatures are forecast this weekend.

&&

.AVIATION...

The Southeast Michigan terminals will be positioned between a
surface low to the northeast and a ridge of high pressure building
southeastward into the lower Ohio Valley from the eastern Plains
today. This leads to a corridor of confluent cyclonic west-northwest
flow that cold advects across the Great Lakes region. Expect
sustained lake moisture release along the western Lake Superior to
northern Lake Michigan connection that feeds VFR boundary-layer
stratocumulus clouds. Additionally, a few rounds of lake effect snow
showers/flurries are expected, although specifics on positioning
remain less resolved. Higher confidence in the lack of long-duration
banding and unlikely overachievement in rates which should hold
visibility to VFR, but a brief drop to MVFR cannot be completely
ruled out at any one terminal. Main timeframe for snow showers will
be between 21Z and 01Z.

Morning gustiness is on the decline as lower column winds drop below
20 knots which limits afternoon gust potential, even as mixing
heights lift into the 5 kft to 7 kft AGL range. Some clearing
expected tonight with the initial attempt at departure of governing
longwave troughing.

.DTW THRESHOLD PROBABILITIES...

* Medium for ceiling at or below 5000 feet early this afternoon.

* High for precipitation type as snow with any evening lake effect.

&&

.PREV DISCUSSION...
Issued at 310 AM EDT Tue Apr 8 2025

DISCUSSION...

Early morning wind chill readings will primarily be in the 10 to 15
degree range, providing a very winter-like feel for this early April
day. The arctic air now spilling across the region will bring 850mb
temps to -14 to -15C by daybreak. The airmass is cold enough to even
generate some lake clouds across the region. There will at least be
some shallow moisture to persist into the afternoon, leading to some
occasional strato cu. Model soundings suggest the moisture, albeit
shallow, will reside within the regime for dendrites. So a few
flurries/light snow showers can not be ruled out, limited by the
very dry air now residing in the low levels. Large high pressure now
extending across the western Great Lakes will advance to the east
today amidst increasing mid level confluence. This larger scale
subsidence will at least support intervals of sun today. Even with
early April insolation, the airmass overhead is so cold that high
temps are likely to only range from the mid 30s to lower 40s (a
solid 15 degrees below seasonal averages). A weakening gradient
tonight will lead to some optimal radiational cooling potential into
the overnight before mid/high clouds begin to increase late,
warranting nighttime lows from the upper teens to mid 20s.

Elevated isentropic ascent will increase late tonight and through
the day Wednesday within the entrance region of an upper jet streak,
resulting in ample cloud cover. Despite some rebounding of the low
level thermal fields, the cloud cover will keep Wed highs in the
40s. Initially, very dry low level air will limit precip at least
through early Wed afternoon.

Numerous short wave impulses cascading across the Midwest will
support an amplification in a mid level trough over the northern
Ohio Valley/southern Great Lakes region Wed night into Thursday.
Variance among deterministic solutions and their ensemble members
the last several model runs have led to uncertainty as to the degree
of amplification of this system, particularly with respect to whether
this will evolve into a compact closed low or remain more of an open
progressive wave. Recent trends are leaning toward a more closed
system. There is still however ample spread with respect to the
intensity and persistence of the corresponding mid level
frontogenetical forcing/deformation. Given wet bulb zero heights will
primarily below 1000 feet, the strength of the ascent and degree of
boundary layer cooling will play largely into a rain vs wet snow
event, especially Wednesday night when daytime heating will not be
at play. Given there remains a respectable degree of model spread on
precip amounts and types, a general ensemble mean approach will be
maintained. This will support the higher precip chances (with 24
hour liquid equip amounts of .25 to .5 inch) late Wed into Thursday
across the southern half of the forecast area, with a general
rain/snow mix. Lessor amounts will be forecast across the north.
There is the potential for some minor snow accumulations (an inch or
two) if a slightly stronger/colder solution pans out. The expectation
for east-southeast winds off western Lake Erie, where water temps
are in the low 40s, will keep the more favorable precip type across
Monroe and Wayne Counties as rain or rain/melting snow.

MARINE...

Northwest winds will continue to diminish further today as the
pressure gradient continues to slacken with high pressure over the
Western Great Lakes sliding east. Winds become light over the
Central Great Lakes Tuesday night into Wednesday.

Light to moderate southeast to northeast winds then develop with a
flat surface low tracking through the Ohio Valley Wednesday night-
Thursday bringing snow/wintry mix and rain to the Central Great
Lakes. Although northeast winds in the Thursday-Friday time frame
appear to only to out around 20 knots, the prolong nature and
unstable low level profiles could be enough for waves building above
4 feet across the southern Lake Huron basin and impacting the
nearshore waters.

&&

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

     Small Craft Advisory until noon EDT today for LHZ422.

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

$$

AVIATION.....KGK
DISCUSSION...SC
MARINE.......SF


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