Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/26/22

Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 703 PM EST Sun Dec 25 2022

.AVIATION...

Conditions start a transition away from the holiday weekend winter
storm and toward the northern Plains low pressure system. This
system brings still meaningful aviation weather but with much less
intensity compared to the last few days. For tonight, light lake
effect snow showers or flurries remain favored in the PTK to FNT
area while MVFR ceiling holds across the remainder of SE Mi. A
notable clearing line near the IN/OH border will be monitored,
however cloud layer wind projections remains too westerly to allow
it much northward progress. That window of opportunity is shortened
even more by the Plains system as it reaches IL in the morning while
sweeping more low clouds into the region. A surface trough of low
pressure extends northward from the Ohio valley low to serve as a
broad focus for stratus while system moisture brings a chance of
light snow up to near DTW and PTK. Some seeding of lake effect is
also possible but would remain closer to Lake Michigan in the weak
low level wind field. Overall, the potential for snow and wind are
secondary to cloud restriction through the day and into Monday
evening.

For DTW... Lake effect snow is reduced to flurries at the terminal
this evening while MVFR ceiling holds late tonight and Monday. There
is low probability that a clearing line near the Ohio border this
evening moves northward toward DTW early in the morning, a trend that
will be monitored for a short window of more optimistic cloud
conditions. A period of light snow then remains possible as the next
low pressure system arrives over IL by late morning. Only trace
amounts of snowfall are expected, if any.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less through Monday.

&&

.PREV DISCUSSION...
Issued at 329 PM EST Sun Dec 25 2022

DISCUSSION...

Radar mosaic continues to show a roughly 60 mi wide swath of
flurries to light snow extending from around I94 up to I69, with the
slightly better snow rates wedged between the W-E I96/696 corridor
up to I69. Given the just recently observed subtle signs of snow
production slowing down over the west side of the state and with
latest ACARS soundings holding onto supersaturation w.r.t ice through
4kft over SE MI, flurries to light snow activity is expected through
00-06Z tonight. Ongoing activity will gradually push northward as
dry air works into the state border. Expect new accumulations up to a
half-inch centered between m59 to I69. Better subsidence will squash
moisture depths late tonight and overnight, decreasing lake effect
snow chances.

Advanced Layered Precipitable Water and water vapor imagery exhibits
a mid-level shortwave now in place over North Dakota with deep layer
Pacific moisture up through 500 mb which is aiding in the production
of light snow on the leading edge of the wave. This shortwave and an
associated surface low reflection is projected to path southeast
into Iowa and Illinois late tonight before wrapping around into the
northern Ohio River Valley by tomorrow morning. Moist system
relative isentropic ascent between h750 to h650 will take place over
southern Michigan in response to the approaching wave which will
bring the chance (30-40%) for renewed light snow showers favored
around or just north of the MI/OH border. Modest lake
enhancement/convergence will also bring renewed lake effect snow
chances around or just north of the I69 corridor through the early
evening. Latest guidance hints at more favorable lake effect
trajectories centered in the afternoon and evening. This wave is
entering a region of very dry mid-level air and the lift remains
subtle with the wave, so any precipitation observed will be light
with around a dusting up to a half-inch of new accumulation by late
tomorrow afternoon for any snow observed.

Mid-level flow turns zonal heading into the midweek period following
the departure of the wave. Surface high pressure over the Plains
will wash out into the Gulf by Tuesday afternoon as a secondary high
pressure system starts to root over the western Atlantic. This will
usher in warmer west CONUS temperatures across the Midwest and Great
Lakes by the middle of the week. Longwave amplification across the
western CONUS will also take place during the middle of the week as
a strong 150 knot jet core initially comes onshore around Baja
California. Downstream amplification of the ridge over the Great
Lakes will result in warmer than normal temperatures filling in
across the region Thursday through at least early next week.

EPS ensemble means pull in h850 temperatures of 5-7C between 18Z Wed
and 12Z Sun. Confidence is only increased regarding a significant
warm up event from perusing the cluster phase space analysis, which
shows excellent convergence of the four clusters vs. mean average by
00Z Fri. Unsurprisingly, 500 mb variance increases with time through
the New Year, however even when factoring in the cooler subset of
ensemble, the signal is still very strong that warmer than normal
temperatures are likely. Temperature highs hitting 50+ are
increasingly likely for Friday/Saturday, at least near the border and
into the Metro Detroit. Any overnight lows in the 40s, which are
currently in the ongoing forecast for Fri & Sat morning, would
challenge minimum high temperature records. Rain chances also become
increasingly likely with the warmer temperatures as gulf moisture
flows into the region. Overall, there is extremely high confidence
for above normal temperatures late this week into early next week,
with moderate confidence for above normal precipitation (rain).

MARINE...

Inversion heights remain high across the lakes this afternoon as
broad cyclonic flow and a very cold air mass persist across the
central Great Lakes. This is resulting in continued unsettled marine
conditions through this afternoon and evening with elevated wave
heights bringing Small Craft Advisories to the nearshores of the
Thumb and lingering gales across northern Lake Huron. The favorable
fetch of northwesterly flow out through the Straits will allow bands
of lake effect snow to continue streaming across northern Lake
Huron. There should be a noticeable drop off in gales across the
northern lakes by 10 pm this evening and should finally conclude
this long duration wind event over these past few days. Inbound high
pressure to the south of will help bring much lighter winds for
Monday and most of Tuesday, but some chances for snow across Lake
Huron will remain. Next chance for elevated wind gusts will come
Tuesday night with gusts out of the southwest across northern Lake
Huron to around 30 knots.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.

Lake Huron...Gale Warning until 10 PM EST this evening for LHZ361-362.

     Small Craft Advisory until 4 AM EST Monday for LHZ421-441.

Lake St Clair...None.

Michigan waters of Lake Erie...None.

&&

$$

AVIATION.....BT
DISCUSSION...AM
MARINE.......AA


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