Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/15/22

Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 838 PM EST Wed Dec 14 2022

.UPDATE...

A rapidly northward moving short wave now approaching the bootheel
of Missouri will lift into srn Lower Mi by 12Z Thurs. The development
of an enhanced (70 knot) LLJ preceding this wave has begun to
support a more notable deep layer moisture surge into Indiana and
southern Ohio. This moisture transport will extend into Se Mi
overnight in advance of the mid level short wave. Excellent mid level
isentropic ascent within an increasingly difluent upper wind field
will support widespread rain overnight. Recent model trends suggest
the time period of rain will likely be brief as mid level dry air
will arrive aggressively from the south around and shortly after
12Z.

Forecast concerns this evening are with the duration of any freezing
rain at the onset of precip overnight, mainly from the M 59 corridor
and points north. Sfc temps are in the low 30s in this region but
dewpoints are in the low 20s (even a few upper teens) with east flow
sustaining a feed of low level dry air. This places sfc wet bulb zero
temps in the mid/upper 20s as of 01Z. Analysis of latest HRRR, RAP,
NAM model soundings suggest that the increase in the easterly winds
overnight will actually sustain enough of a shallow mixed layer to
hold sfc temps at or just above freezing even at the onset of rain,
with temps slowly rising thereafter as rapid moistening raises sfc
dewpoints/wet bulb temps. So the current forecast will be maintained
which just carries just a brief mention of freezing rain at the onset
of rain overnight. Although wind speeds/gusts have been slow to
rise this evening, regional observations and latest hi res guidance
remains supportive of the current wind advisory across the north half
of the forecast area tonight.

So in short, no major forecast changes will be made this evening.
There will only be some minor adjustments to temps and the onset of
rain based on latest observations and hi res guidance.


&&

.PREV DISCUSSION...
Issued at 551 PM EST Wed Dec 14 2022

AVIATION...

A rapid deepening of low pressure as it tracks from the Lower Ohio
Valley into Wisconsin tonight will drive a plume of deep layer
moisture into Se Mi overnight. This will result in widespread rain
across Se Mi. There may be an hour or two time period where the
precip initially begins as freezing rain at MBS due to wet bulb
cooling affects before low level warm air advection drives sfc temps
above freezing. The other TAF sites are expected to be above
freezing at the start of the precip, thus rain is expected. Ceiling
heights will lower overnight as the rain moves into Se Mi, with
upstream observations and model guidance suggesting IFR conditions
developing prior to daybreak Thursday. The deepening of the sfc low
combined with strong high pressure anchored over Quebec will result
in increasing east winds during the night. Model soundings and
probabilistic guidance suggests gusts over 35 knots at times. At
this time, a more conservative approach to wind gusts (at or below
30 knots) will be maintained given some concerns that the onset of
rain and wet bulb cooling may support a boundary layer that is more
stable than suggested by model soundings.

For DTW...The onset of rain is projected to start between 06 and 07Z
tonight, with the rain really tapering off after 12Z Thurs. Once the
rain begins, there will be a rapid drop in ceiling heights as the
low levels rapidly cool and moisten. The east winds are likely to
peak between 07Z and 10Z before rainfall stabilizes the low levels
and the east/southeast gradient weakens.

 DTW THRESHOLD PROBABILITIES...

* High in ceilings below 5000 feet overnight through Thursday
  evening.

* High that precipitation will be all rain tonight and Thursday
  morning.

* High that the east winds will exceed crosswind thresholds between
  midnight and 5 AM.

PREV DISCUSSION...
Issued at 354 PM EST Wed Dec 14 2022

DISCUSSION...

Remnants of mid level ridging wane through the evening as the strong
system off to our west inches closer to southeast Michigan.
Conditions remain dry through a majority of the evening, with 850-
500MB dry layer holding firmly in place per ACARS soundings and
surface dewpoint depressions +5 C or greater. That said, mid level
moisture will be on the increase as increasingly favorable dynamics
set up over the Ohio Valley resulting in thickening high cloud.
Temperatures hold in the low to mid 30s under the increasing cloud
coverage before precipitation moves in late tonight.

From a CONUS perspective, the mid-level circulation has remained
firmly parked over the northern Plains today. GOES-16 mid-level
water vapor imagery shows a well-defined shortwave feature pivoting
cyclonically around this cutoff low, which will be the focus for
precipitation late tonight through mid-day Thursday over southeast
Michigan. Robust synoptic ascent due to the advection of this
vorticity reservoir and divergence on the nose of the upper level
jet synchronize to result in surface cyclogenesis over the lower
Ohio Valley early this evening. With ample Gulf moisture available,
precipitation becomes increasingly organized to our south and
spreads into lower Michigan tonight on the nose of the upper level
jet. Leading edge of precipitation should quickly saturate the
residual dry layer below, with steadier precipitation overspreading
the majority of the cwa late tonight and lasting through the morning
hours tomorrow.

Refined PoPs slightly with a ramp up period for precipitation onset,
with the leading edge of the precipitation shield reaching
Lenawee/Monroe counties mid-evening. Steady precipitation then fills
into the cwa overnight as the aforementioned surface low occludes
back into the main circulation feature over the upper Midwest. For
areas south of I-69, precipitation type will be all rain as surface
temperatures remain above freezing for the overnight hours. North of
I-69, pockets of freezing rain will be plausible initially as
effects of wet bulb cooling are more prevalent. This will be a
relatively short window as a steady influx of warmer southeast flow
and higher precipitation intensity raises temperatures above the
freezing mark prior to the morning commute. Short duration limits
ice accumulations to a few hundredths, highest for the Tri Cities,
corresponding to some slick spots on bridges/overpasses early
tomorrow morning. Will hold off on winter weather headlines given
limited duration and marginal accumulations/impacts with this event,
but will continue to monitor surface and road temperatures closely
for any overachievement.

Energetics of this system also result in an increasingly organized
wind field setting up over the cwa. Impressive 60+ knot low level
jet centered in the lowest 2.0-4.0 kft agl moves into southeast
Michigan overnight, topped by a sharp inversion layer. Drier
boundary layer conditions north of I-69 result in slightly more
unstable profiles and mixing potential. Therefore, gusts approaching
45 mph will be possible overnight into the morning hours tomorrow
which has prompted the issuance of a Wind Advisory for northern
locales. Elsewhere, gusts of 35-40 mph will be possible.

Moisture gradually gets stripped away daytime Thursday as the dry
slot surges overhead, thus pushing precipitation chances into Lake
Huron/Ontario by midday. Gradual passage of the occluded front
initiates a period of cold advection throughout the low levels,
drastically shifting thermal profiles and retracting the warm nose
aloft. Loss of deeper layer moisture inhibits any substantial
precipitation for the late week period into this weekend, although
recycled moisture and weaker ribbons of vorticity circulating around
the mid-level low pressure center will trigger additional light
precipitation chances. With a cooler airmass in place (highs
struggle to reach the freezing mark), snow will be the dominant
precipitation type although any accumulation will be light without
any main forcing mechanism. Cooler weather remains in place through
early next with highs settling in the 30s with the cutoff low
eventually being replaced by zonal flow aloft.

MARINE...

East-southeast winds strengthen going into this evening in response
to the tightening gradient as strong low pressure approaches the
western Great Lakes. Gales become possible across all waters by late
evening-early tonight with strong gales (45kts) expected to develop
after midnight over Lake Huron. Peak wind gusts look to occur during
early/mid Thursday morning (~4-10am) with strongest gusts likely
over northern Lake Huron given the more favorable fetch. Gusts over
this area (mainly north of Presque Isle) could touch lower end storm
force. For now, have maintained current Gale Warnings however will
continue to monitor trends if an upgrade to a Storm Warning would be
warranted in future forecast updates. Widespread precipitation will
accompany this system with initial chances spreading northeastward
across the central Great Lakes this evening into Thursday. Low
pressure weakens late Thursday into Friday but doesn`t fully vacate
the region until late weekend as it gradually wobbles across the
Great Lakes. As a result, rain/snow chances as well as more modest
(15-25kt) wind linger to finish out the week.

HYDROLOGY...

Widespread precipitation will expand across southeast Michigan late
tonight and persist into early Thursday as a broad low pressure
system approaches the region. While a brief period of light snow
and/or freezing rain may occur at the onset, the bulk of this
precipitation will fall as liquid rain. Rainfall amounts generally
between 0.50" and 0.75", with some localized higher amounts south of
I-96, are expected before the widespread rain moves out by mid day Thursday.
Flooding concerns are not anticipated at this time.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Wind Advisory until 10 AM EST Thursday for MIZ047>049-053>055-
     060>063.

     Lakeshore Flood Advisory until 10 AM EST Thursday for MIZ049-055-
     063.

Lake Huron...Gale Warning until 10 AM EST Thursday for LHZ421-422-441>443.

     Small Craft Advisory until 10 PM EST this evening for LHZ421-
     441>443.

     Gale Warning until 4 PM EST Thursday for LHZ361>363-462>464.

Lake St Clair...Gale Warning until 10 AM EST Thursday for LCZ460.

Michigan waters of Lake Erie...Gale Warning until 10 AM EST Thursday for LEZ444.

     Small Craft Advisory until 10 PM EST this evening for LEZ444.

&&

$$

UPDATE.......SC
AVIATION.....SC
DISCUSSION...MV
MARINE.......KDK
HYDROLOGY....MV/TF


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