424
FXUS63 KDTX 261105
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
605 AM EST Thu Dec 26 2024
.KEY MESSAGES...
- Patchy fog, mist, drizzle, and spotty light rain will continue
across the area today. There is potential for slick roads in the
Saginaw Valley and Thumb this morning due to pockets of light
freezing mist/drizzle.
- Light rain arrives late Friday, marking the start of a mild and
rainy weekend with highs reaching the 50s on Saturday.
- Decreasing temperature trend brings temps closer to seasonal
normals to start the new year.
&&
.AVIATION...
An elevated warm front setting up over the region will maintain
saturated low-level conditions much of today with low stratus,
patchy mist/fog, and pockets of drizzle especially this morning.
Early morning observations range from MVFR for terminals near/east
of I-75, to LIFR along the M-59 corridor and across west and mid MI.
Ceiling heights will trend lower early as additional moisture pools
in, with prevailing lower MVFR to IFR/LIFR likely through the
afternoon. Drier air will then work in from the south late this
afternoon and evening causing ceilings to lift and trend toward VFR
tonight into Friday morning. Light surface wind holds from the
southeast through the period.
DTW THRESHOLD PROBABILITIES...
* High for ceiling at or below 5000 feet today.
* High for any precip to fall as rain today.
* Low for ceilings at or below 200 feet and visibility at or below
1/2 SM this morning.
&&
.PREV DISCUSSION...
Issued at 335 AM EST Thu Dec 26 2024
DISCUSSION...
A mid-level ridge is building directly overhead this morning with
500mb heights just north of the Great Lakes exceeding 2 standard
deviations above the norm for this time of year. Beneath the ridge
is a stable thermodynamic profile with abundant moisture in place
from the surface up to the 700-850mb layer. A disorganized shortwave
tracking just south of the IN/OH border within the base of the ridge
is driving an elevated warm front north into the area with moisture
depth increasing from south to north through the rest of the
morning.
The warm/moist advection has been sufficient to lower the stratus
base and result in some patches of sprinkles, drizzle, and fog early
this morning. Air temps and dew points are sitting in the lower to
mid 30s across the area with the Saginaw Valley and Thumb with
readings right near freezing at press time. This will be a target
for potential freezing drizzle early this morning before dew points
rise above freezing. Rate of any precip is expected to stay light
enough to keep ice accumulation minimal but a few slick spots on
overpasses will be possible. This leads into another grungy late
December day with overcast skies and continued patchy
fog/mist/drizzle possible through the day into tonight as the
elevated warm front begins to wash out over the area. Temperatures
will reach the mid to upper 30s (Thumb/Saginaw Valley) to lower 40s
(near the Ohio border) today before settling into the lower to mid
30s overnight.
A closed southern stream upper low will eject from the southern
Plains into the Great Lakes on Friday, weakening through the day as
it encounters the ridge still holding in place across eastern North
America. The surface low lifts north across Wisconsin late Friday
night, holding us within mild and drier southeast flow through the
day. Confidence is increasing on later arrival of the main slug of
moisture within the wing of isentropic ascent, with latest guidance
holding the better chances after 21Z when the 40 kt LLJ arrives at
the stateline. After another day of steady 1000-850mb thickness
increases, surface temps will reside in the upper 30s to lower 40s
ensuring an all-rain outcome. An arc of showers will track south to
north across the area late Friday afternoon into the overnight,
bringing rainfall totals on the order of 1 to 2 tenths of an inch.
The dry slot may begin to cut into shower coverage after midnight
but then a second shortwave quickly follows behind the first to
bring additional shower chances through parts of Saturday. Very mild
air builds in within the veering southerly flow with highs well into
the 50s likely on Saturday.
Arrival of a strong Pacific jet streak over the PNW leads to
consolidation of the upper air pattern by this weekend, with a
longwave trough easing in from the Plains around Sunday. This will
bring another chance of rain as a low or frontal wave tracks
somewhere between the southern Great Lakes and Ohio Valley. Much of
the ENS and GEPS ensemble membership favor a more amplified, slower
trough that allows much of the moisture transport to become directed
to our south and east. The GEFS members generally favor a lower
amplitude trough that pulls the cold conveyor closer to the Great
Lakes, offering a higher QPF scenario. Ensemble mean QPF data
suggest another few tenths of an inch will be possible in this
window. Cooler air arrives behind this system with high temperatures
trending back into the 40s to start the week.
MARINE...
Western periphery of a high pressure system will continue to
influence the Great Lakes today which will maintain lighter south to
southeast flow. Low pressure derived from ArkLaTex will then travel
north, impacting the Great Lakes area by late tomorrow into the
early weekend. Arrival of the system will strengthen the pressure
gradient, boosting wind gusts to around 20 to 25 knots across Lake
Huron, while bringing increasing chances for rain showers. There
will be additional chances for a second low pressure system to
impact the Great Lakes again on Sunday, but confidence is lower
regarding the final track of this system.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....TF
DISCUSSION...TF
MARINE.......AM
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