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000
FXUS63 KDTX 221950
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
350 PM EDT Mon Apr 22 2024

.KEY MESSAGES...

- Warming trend continues today with dry and sunny conditions.

- Showers arrive late tonight with possible thunderstorms Tuesday
afternoon and evening.

- Strong winds of 30 to 40 mph will be possible in the Thumb late
Tuesday night and Wednesday.

- Dry and cool weather is expected Wednesday and Thursday

- Periodic rain and/or thunderstorm chances are expected to develop
late Friday through the upcoming weekend as an upper level trough
pushes across the region. Low confidence exists in the timing of
rain activity.

&&

.DISCUSSION...

Dry air from the surface to 500hPa dominates, with the exception of
a low-level diurnal cumulus deck that will soon dissipate. Mostly
sunny skies have pushed temperatures up into the mid-60s today, with
dew points around 30. Red Flag Warning remains in effect as the
combination of aforementioned dry air and southwest winds of 15mph
have kept the risk in place. The warning is in effect until 8pm
tonight, at which point dew points are expected in increase as
temperatures cool overnight.

Positively tilted upper level trough supports the further
development of a low pressure system bringing precipitation to the
area. The first band is expected to move in Tuesday morning,
bringing light rain across the CWA supported by a cold front. Dry
airmass fills in behind the front further north, while a larger rain
band clips the southern part of the CWA, mainly staying south of I-
94.

Southeast Michigan will be at the southern edge of an area of strong
frontogenesis as the low tracks eastward Tuesday night, producing
rain along a second, stronger cold front. SPC has issued a Marginal
Risk for the northern half of the CWA for this fropa. Freezing
heights will be low and lapse rates will be steep, prompting the
possibility for hail to approach severe limits, should any severe
storms appear. Wind is also a concern, with strong low level flow
and low stability potentially allowing gusts up to 50mph to mix
down. The appearance of severe storms seems unlikely due to low CAPE
values coupled with high shear, but should a stronger updraft
develop, it is possible that a storm could turn severe. Storm total
QPF for the entire area is around 0.25 across much of the CWA, with
greater values up to 0.4 inches possible near the Michigan/Ohio
border.

The aforementioned front drops through the CWA Wednesday night, with
wind gusts ramping up in its wake especially near the Lake Huron
shoreline where subdued frictional effects and warmer lake waters
lead to a stronger low level jet and more efficient mixing potential
respectively. The expectation is for gusts to briefly ramp up to 35-
40 mph overnight, highest gusts in the Thumb, and only gradually
subside through Wednesday morning.

By mid morning Wednesday, the cold front will be well south of the
state line, establishing a period of deep isentropic downglide and
increasing column stability locally. A low amplitude shortwave
trails behind the main trough axis to keep stratus trapped below the
subsidence inversion in the morning before clearing out Wednesday
afternoon. Period of mid-level height rises and surface high
pressure will maintain overall benign conditions Wednesday through
Friday, although thermal troughing with H8 temperatures in the
negative single digits will support below normal highs in the low
50s Wednesday and mid 50s on Thursday. Coldest temperatures expected
Thursday morning with lows in the 20s. Freeze headlines look
increasingly likely for Wednesday night-Thursday morning.

Meanwhile, the next major weather system ejects out of the Four
Corners region late Thursday with a northeastward trajectory toward
the upper Midwest for the weekend. Southeast MI will reside between
departing high pressure to the east and the upstream low to support
deep southwest return flow. Effective moisture transport thus ensues
with over 90% of CMCE/EPS/GEFS members forecasting PWATs above an
inch by Saturday. Models continue to struggle with large-scale
feature placement and amplitude, although SE MI looks to reside
within the broader area of warm advection. Setup thus looking
favorable for periods of rain and possible thunderstorms late Friday
into the weekend alongside warming temperatures that comfortably
climb into the 70s late this week.

&&

.MARINE...

A ridge axis gets shoved toward the Mid-Atlantic this evening as an
unbalanced speed max extends across north-central CONUS. This forces
downstream surface winds over the central Great Lakes to veer south-
southwesterly with enhanced flow across Saginaw Bay and Lake Huron.
The warm advective regime limits gust potential to around 25 knots
but some areas could exceed 30 knots over the open waters. Surface
low pressure associated with the aforementioned disturbance then
crosses central Ontario and northern Lake Superior late tonight and
Tuesday yielding renewed gradient flow. Small Craft Advisory
criteria winds and waves arrive after midnight for Saginaw Bay
before spreading to the rest of the nearshore zones by sunrise, thus
the advisory has been issued until 4 PM Tuesday. The system also
yields a period of showers which may include some thunderstorms
later in the day, especially along the secondary frontal boundary.
Colder post-frontal air filters in Tuesday night leading to brisk
northerly flow. Some low-end potential for gusts to gales exists
while lapse rates remain steep and forecast soundings are well-mixed
as the LLJ clips central Lake Huron. Benign marine conditions
expected Thursday with high pressure in control, at least through
Friday morning.

&&

.PREV DISCUSSION...
Issued at 1258 PM EDT Mon Apr 22 2024

AVIATION...

Upper clouds will thicken late in the day as a ridge of high
pressure shifts east of the region. Increased southwesterly flow
between this departing ridge and an approaching cold front will
bring a steady increase in moisture late tonight into Tuesday with
light showers working into the area 08z-10z and persisting for 4 or
5 hours. Ceilings through 18z Tuesday should remain lower VFR. Wind
gusts near 20 knots are expected this afternoon with 20-25 knot
gusts again from late tonight through Tuesday within the tightening
pressure gradient.

DTW THRESHOLD PROBABILITIES...

* Low for ceilings aob 5kft late tonight, medium on Tuesday.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Red Flag Warning until 8 PM EDT this evening for MIZ047-048-053.

Lake Huron...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LHZ441>443.

     Small Craft Advisory from 1 AM to 4 PM EDT Tuesday for LHZ421-422.

Lake St Clair...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LEZ444.

&&

$$

DISCUSSION...BC/MV
MARINE.......KGK
AVIATION.....DG


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