369
FXUS63 KDTX 060847
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
447 AM EDT Sun Apr 6 2025

.KEY MESSAGES...

- Seasonally cold weather is forecast Monday and Tuesday. Snow
showers are likely Monday.

- The next chance for precipitation, rain and snow, is Wednesday
night and Thursday.

&&

.AVIATION...

Diffuse high pressure remains in control today, supporting vfr
conditions. Winds speeds will continue to decrease through the
morning while maintaining north to north-northeast flow. Wind
direction then turns variable by the afternoon before flipping
southwesterly late tonight.

.DTW THRESHOLD PROBABILITIES...

* None

&&

.PREV DISCUSSION...
Issued at 320 AM EDT Sun Apr 6 2025

DISCUSSION...

An amplifying short wave forecast to dive into the Minnesota
Arrowhead late today will force low level ridge amplification
downstream across Lower Mi. This will ensure dry conditions across
Se Mi today. Ongoing northerly flow along the southern edge of the
expanding sfc high has been sustaining weak low level cold air
advection into Se Mi during the night. The flow will weaken during
the day as the sfc high expands further into Lower Mi. Despite some
lingering mid/high clouds, especially across the south, early April
diurnal insolation will boost afternoon highs well into the 40s over
most of the area despite the resident cool airmass overhead.

Continued amplification of the mid level short wave is forecast as
it advances into Lower Mi late tonight/Monday. The associated sfc
low is forecast to track across nrn Lower Mi late tonight and Lake
Huron Monday morning. Strengthening southwest flow across Se Mi in
advance of the associated surface cold front will limit nighttime
radiational cooling, warranting min temps in the 30s. The compact
nature of the positive PV anomaly within good baroclinicity will
elicit a strong dynamic response as this mid level wave crosses the
region Monday. The more focused ascent will be located over Lake
Huron. Strong albeit brief forcing will accompany the associated
cold front across Se Mi during the day. Sub 1000 ft wet bulb zero
heights will support snow as the favorable precip type, although
lingering boundary layer warmth in the south will at least warrant a
mention of a rain/snow mix. The brevity of the stronger forcing and
somewhat limited available moisture will keep liquid equivalent QPF
mainly under a tenth of an inch. Steep lapse rates through both mid
level cold air advection and diurnal heating may however result in a
few brief bursts of higher intensity snow showers. The rates may be
enough to support some minor accums before warm ground temps melt
anything that sticks.

The mid level short wave will carve out a long wave trough across
the eastern Great Lakes Monday into Tuesday. The post frontal cold
air advection on Monday will actually be quite good for April as
850mb temps plunge into the negative teens by Monday night. The
gradient flow will hold min temps in the 30s, however wind chill
readings will fall into the low teens. For most of the day Tuesday,
low level cyclonic to neutral flow and a shallow layer of moisture
will sustain ample diurnal clouds. While some peaks of sun are
likely, the airmass will be so cold that daytime highs on Tuesday
will only be in the 30s to around 40, some 15 degrees below seasonal
averages.

Although there is general agreement that a compact short wave
impulse will emerge from the northern Rockies and track across the
southern Great Lakes/Ohio Valley region Wed night into Thursday,
there is ample spread among ensemble members with respect to the
timing and strength of this system and the northward extent of the
better forcing. While there are some solutions that indicate robust
mid level frontal forcing directly over Se Mi, uncertainty remains
high this far into the forecast. Given the thermal profile across Se
Mi will be within the rain/snow threshold, this system will be one to
monitor over the next few forecast cycles.

MARINE...

Pronounced surface ridge will lead to light winds today before a
clipper system tracks through on Monday, producing a period of snow
and rain showers. Even colder air will follow this system. As the
low tracks through Lake Huron, there is high confidence in a period
of north-northwest gales over much of the open waters of Lake Huron.
However, the gales look to be short lived for any particularly
marine zone as the low races east in the afternoon, and will hold
off on a Gale Watch. There are also significant differences with the
strength/deepening of the low as well. Regardless, small craft
advisories will likely be needed over at least the nearshore waters
of lake Huron, as the unstable low level profiles promote good wave
growth in excess of 6 feet over the southern Lake Huron Basin. Winds
will slowly diminish Monday night into Tuesday as sprawling high
pressure arrives Tuesday night, leading to light winds for
Wednesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 4 AM Monday to noon EDT Tuesday for
     LHZ421-422.

     Small Craft Advisory from 10 AM Monday to noon EDT Tuesday for
     LHZ441>443.

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

$$

AVIATION.....AM
DISCUSSION...SC
MARINE.......SF


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.