Updated:
30-Nov-1999 4:00pm
NWS Forecast Discussion
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FXUS63 KDTX 251625
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1225 PM EDT Sat Mar 25 2023
.AVIATION...
Strong low pressure tracking through southeast Michigan early this
afternoon and through Central Lake Huron early this evening. Winds
will be quickly ramping up at the start of the taf period, with
gusts of 34-44 knots expected later today out of the southwest-west,
highest gusts over southern taf sites which are more entrained in
the warm sector. The good mixing will support improvement in cigs
back into MVFR. Mid level dry slot looks to limit precipitation
amounts over the southern taf sites, but northern tafs will have
some deformation snow to work through, but limited/light
accumulation (less than an inch) with some melting and weakening
trend expected.
As the low exits, there looks to be a tremendous amount of subsidence
which will attempt to completely dry out the low levels, and will
continue with the inherited tafs indicating low clouds mostly cleared
out tonight. However, low level cold advection tonight into tomorrow
morning will likely be sufficient for MVFR cigs to return to at
least MBS and probably FNT. Exact timing and areal coverage remains
in question however. Would not rule out the low clouds reaching PTK
as well.
For DTW...Southwest winds gusting aoa 40 knots later this afternoon
looks good with winds veering around to the west toward evening. A
gradual drop in winds will occur for the rest of the evening and
overnight as low exits the Central Great Lakes region.
DTW THRESHOLD PROBABILITIES...
* High for cigs at or below 5 kft through evening, then low.
* High for precipitation type as rain through mid afternoon.
Moderate for rain/snow mix late afternoon/early evening.
* Low to moderate for crosswind thresholds late afternoon into the
evening.
&&
.PREV DISCUSSION...
Issued at 1030 AM EDT Sat Mar 25 2023
UPDATE...
Running forecast still largely on track with only some minor
adjustments needed this morning. KDTX 25.12Z RAOB sounding shows an
impressive inversion just above 900mb which has largely prevented
the 45-55kt LLJ winds to be able to mix down to the surface. Given
ASOS/AWOS wind observations thus far across the CWA have struggled
to get much higher than ~20kts, have nudged down gusts through the
remainder of the morning into the 15-25kt range. Stronger gusts (in
excess of 40mph) can still be expected by afternoon into the evening
as the low continues to deepen and lift toward the Thumb/Lake Huron
leading to trailing CAA increasing mixing depths/efficiency.
Occasional gusts around 50mph remain possible focused toward the
Ohio border where strongest flow aloft will reside. Other change to
forecast was lowering highs across the southern half of the region
back into the mid to upper 40s as ample cloud cover and off-and-on
shower activity has damped the rate of diurnal warming. Shower
activity wanes over the rest of the morning as the respectable
low/mid level dry slot seen on satellite WV imagery works into SE
MI. Some additional rain/snow showers still possible on the backedge
of the low this afternoon-evening, mainly over areas north of M-59,
however any accumulations will be minor (dusting to half inch) given
the drier airmass that will be rapidly advecting into the region.
PREV DISCUSSION...
Issued at 430 AM EDT Sat Mar 25 2023
DISCUSSION...
Highly dynamic wave lifting through the Mid-Mississippi Valley will
continue its north-northeastward trajectory this morning taking aim
at Lower Michigan. KDTX 25.00Z RAOB revealed a particularly dry low-
level airmass, but strengthening east-southeasterly flow AOB 5 kft
AGL continues to support intense ThetaE advection this morning as
the lead edge of the elevated warm front makes inroads from south to
north. ASOS/AWOS along/south of the I-69 corridor indicate the
efficacy of the moist conveyor and forced ascent as the column
quickly saturates causing rapid development/lowering of cloud bases
and expanding showers. Monitoring p-type with early showers as wet-
bulbing has led to a few indications of brief snow, but high-
confidence remains that the main axis of FGEN-driven precip will
fall in the form of rain with moderate intensity at times.
Governing wave continues to deepen with a +135 knot 300 mb jet
streak racing into the Ohio Valley by 12Z as the latest
deterministic models suggest the surface low drops to 991 mb INVOF
the MI/OH/IN border. Initial burst of gusty winds arrive as the 925
mb low makes progress into Southeast Michigan, but warming of 850 mb
temps to nearly 8C along the I-94 corridor ensures stable
thermodynamic profiles. Can still expect a few gusts near 30 mph as
25-35 knot flow descends down below 1.5 kt AGL, therefore lowered
morning gusts through the duration of the easterly composed winds.
The surface low then minimizes near 987 mb as it exits north of The
Thumb by 18Z with trailing southwest cold/dry advection. Coverage of
showers diminishes greatly with the arrival of the dry slot as an
area of 40-55 knot 925 mb LLJ winds work through. Main timeframe for
the Wind Advisory will be focused between 17Z and 04Z. Did extend
the advisory northward into The Thumb with a slightly delayed start
time to account for the secondary low-level wind response on the
back edge of the system as supported by latest NWP solutions.
Occasional gusts to 50 mph are possible across the composite
advisory area this afternoon and/or early tonight.
As for snowfall, the most likely area is favored over portions of
Midland and Bay counties given colder profiles and 2m temperatures
only peaking in the mid-upper 30s. The wet/melting low SLR character
of morning snow should exhaust most of the QPF and favor
grassy/elevated surfaces for areas that can accumulate up to around
an inch of slush. Under the cold advection and deformation component
of this disturbance, forecast soundings support an all-snow
situation along/north of M-59, but the lack of PWAT by this time
should keep any light accumulations to less than a half inch thanks
to the progressive departure of the wave. One important thing to
note with the outgoing forecast is the sharp gradient in low-level
Theta through Midland and Bay counties. Cannot rule out a scenario
in which precip remains all-snow on the front end with limited
diurnal warming that results in 5+ inches of snowfall, mainly along
the northern third of the aforementioned counties. 00Z
UKMET/GFS/NAM/NAM3km lean toward this potential outcome, even when
accounting for a reduction of SLR from the 10:1 output. Given the
mixed-confidence and small areal coverage of this higher-end
scenario, opted to leverage the milder model data at this time.
Drier and seasonable with diminishing gradient wind Sunday as a
diffuse pressure field briefly emerges. Low-amplitude wave will
transit the Ohio Valley late Sunday night and into Monday with a
resurgence of colder air affording a chance for light accumulating
snowfall. Low confidence pattern Tuesday until high pressure arrives
Wednesday with backing flow and weak warm advection. Synoptic
ridging arrives Thursday with strong height rises and much warmer
conditions.
MARINE...
An area of low pressure over southern Indiana will lift
northeastward over southeast Michigan this morning before passing
over southern Lake Huron this afternoon and into Quebec by tonight.
The system will bring rain and snow to the region through the day
and into tonight. Snow will be more prevalent across northern Lake
Huron through the day while points southward will be mainly rain
through the event. Much attention will be the wind as the deepen
system offers gale force winds starting early this morning and
lasting til late tonight. Gale Warnings are in effect for all marine
zones with high end gales likely at times due to the strength of the
low. The early portion of the Warning will be for strong easterlies
that lift through ahead of the warm front, and then later in the day
as the low passes right over central Lake Huron, the winds flip
around to the northwest across northern Lake Huron, and west-
southwest to the south but still at gale force. Will see strong
gales at times to around 40 knots for Lake St Clair and Lake Erie in
the afternoon and local wind probabilities continue to increase for
max wind potential. The strong westerly gales across Lake Erie will
also lead to a Low Water Advisory this afternoon through tonight.
Winds relax late tonight with high pressure building back into the
region. High pressure will hold through Sunday but may get dislodged
by a weak system moving across the southern Great Lakes Monday.
HYDROLOGY...
A strong low pressure system lifting from the Ohio Valley into Lower
Michigan brings widespread rainfall this morning. Coverage is
expected to diminish during the afternoon hours with the intrusion
of drier air. Rainfall totals of a half inch to an inch are expected
by tonight with peak rates near a half inch per hour possible during
the morning timeframe. Any flood threat will be isolated and minor,
consisting of water ponding on area roadways and poor drainage areas.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 2 AM EDT Sunday for MIZ049-054-055-062.
Wind Advisory until midnight EDT tonight for MIZ063-069-070-075-076-
082-083.
Lake Huron...Gale Warning until 4 AM EDT Sunday for LHZ361>363-421-422-441>443-
462>464.
Lake St Clair...Gale Warning until 4 AM EDT Sunday for LCZ460.
Michigan waters of Lake Erie...Gale Warning until 4 AM EDT Sunday for LEZ444.
Low Water Advisory until 5 AM EDT Sunday for LEZ444.
&&
$$
AVIATION.....SF
UPDATE.......KDK
DISCUSSION...KGK
MARINE.......DRK
HYDROLOGY....KGK
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.