National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KDTX 221658
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1258 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.

&&

.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.

&&

.PREV DISCUSSION...
Issued at 1033 AM EDT Mon Apr 22 2024

UPDATE...

In accordance with neighboring offices, a Red Flag Warning has been
issued for Midland, Bay, and Saginaw counties for today. Main factor
in issuance is the dry fuel in that part of the state. Daytime
heating pushing temperatures into the mid-60s today coupled with
drier air moving in and dropping dew points below 30 degrees this
afternoon brings RH values down just enough to meet criteria. Winds
southwest at 15 mph also increases the fire risk today. Dew points
increase beginning at 0Z tonight ahead of rain showers tomorrow
coupled with temperatures dropping below 50 tonight bring the area
safely out of Red Flag Criteria overnight.

PREV DISCUSSION...
Issued at 351 AM EDT Mon Apr 22 2024

DISCUSSION...

A weak backdoor cold front is now working southward through
Southeast Michigan this morning. Windspeeds actually become calm
behind the front whereas much of Southeast Michigan has carried a
light southwest to west wind overnight. The Frost Advisory remains
in effect until 8 AM as there should be a good amount of cooling yet
this morning with surface dewpoints running in the mid to upper 20s.
Differential anticyclonic vorticity advection occurring over the
Ohio River Valley will then allow surface high pressure to extend
northward and strengthen over the Central and Eastern Great Lakes.
This will allow for a reemergence of southwesterly wind of 10 to 20
mph today.

The arrival of an upper level jet streak concurrent with the
increase in midlevel warm advection will support synoptic scale
ascent through the Central Great Lakes late tonight. Forecasted
isentropic analysis and plan view of RH progs suggests the depth of
favorable moisture late tonight will be compromised. The best of sub
700mb moisture is forecasted to reside across the Saginaw Valley
northward to the Straits, whereas better midlevel moisture tracks
through Metro Detroit. Expectations are for a band of light showers
or sprinkles to pass through between 09-12Z before modest
convergence axis then settles and stalls out Downriver to the Ohio
border by late morning. Did take the opportunity to try and time out
the initial shower activity late tonight and introduce a dry period
Tuesday morning. Combination of convergence with progressive
evolution to zonal upper level jet axis is forecasted to result in
an ageostrophic response and zone of frontogenesis very close to the
Ohio Michigan stateline during the day on Tuesday. Hires model
consensus keeps much of the Michigan side dry while a frontal wave
brings prevailing stratiform rain to northern Ohio. The ECMWF is
offering a differing solution that does clip the southern forecast
area for a period of time 12-18Z Tuesday. The last piece to this
Tuesday system will be the deep trough axis and height falls that
dig southward into Southeast Michigan between 21-06Z Tuesday
afternoon/night. Forecast soundings and moisture progs show a drier
airmass is now expected which will offer some slight instability
during the late day period due to the dry adiabatic lapse rates. So,
confidence has increased in a better potential for modest
thunderstorm activity. Marginal instability will exist with MUCAPES
of 250 J/kg or less. A possibility with convective activity late
Tuesday will be small hail as freezing heights will be low at
approximately 5.0-6.0 kft agl. One of the more interesting aspects
of this system will be the potential for a strong wind response late
Tuesday night across the Thumb. The potential will exist for north
winds of 30 to 40 mph for a time, particularly along the Lake Huron
shoreline. Storm total QPF amounts from late tonight through Tuesday
night are expected to be 0.25 to 0.33 inch.

Low level cold advection and strongly anticyclonic flow trajectories
will result in high stability over the region Wednesday through the
day Friday. The narrative for this quiet period will be the
potential for cold temperatures Wednesday morning and again Thursday
morning. The signal is quite high that temperatures across all of
the forecast area will be down into the 20s Thursday morning. Will
likely need a Freeze Warning for Wednesday night/Thursday morning
for Southeast Michigan. The other curiosity for Thursday, is what
sort of lake breeze response will occur off of the Lake Huron/Lake
St Clair aggregate into Downtown Detroit. Difficult to say given the
pervasive southeast wind direction that should be in place during
the afternoon. So may not see an actual lake breeze release, but
conditions are likely to be chilly, regardless, with dewpoints in
the 20s Thursday evening.

From this vantage point, the Friday to Saturday period is a forecast
of low predictability as models are trying to resolve how a deep
trough will migrate into and then eject out of the western United
States. A very high amplitude to this trough brings very low
confidence in temporal details with the latest model trends now
supporting two separate, strong low pressure centers. Confidence is
relatively high in an unsettled, wet period Friday night and
Saturday with a strong warm advection response targeting the region.
Latest indications suggest the warm air advection will remain
progressive across the region Friday night. The difficulty will be
trying to pin down dry periods on Saturday as downstream ridge
amplification should occur in advance of the trailing Southwest
United States PV anomaly.

MARINE...

A ridge axis gets displaced toward the east this afternoon as a
closed upper low over Saskatchewan merges with an adjacent jet into
The Dakotas. This backs winds south-southwesterly downstream with
enhanced flow across Saginaw Bay and Lake Huron. The warm advective
regime limits gust potential to below 25 knots. The low then crosses
into central Ontario late tonight providing a marked uptick in
gradient flow. Speeds should reach Small Craft Advisory criteria
after midnight for Saginaw Bay before becoming more widespread across
most of the central Great Lakes on Tuesday. This system also yields
a period of showers and a few thunderstorms. A cold front then drops
through Tuesday night leading to brisk northerly flow on Wednesday
with some low-end potential for on-shore gales.

&&

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

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

$$

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


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