Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 10/18/23

Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 1149 PM EDT Tue Oct 17 2023


.AVIATION...

Satellite trends now support clearing for the terminals south of the
Saginaw Valley. Went ahead with a prevailing SCT045 with a TEMPO BKN
the first few hours of the taf period out of respect for the broken
mid cloud still pushing eastward across western portions of the
state.  Forecast soundings continue to show a stout inversion which
may limit the vertical mixing. With cloud top radiation and diurnal
minimum, cloud could fill back in at times for the remainder of the
night. High confidence in mid to high cloud pushing into the area
after 14Z Wednesday.

.DTW THRESHOLD PROBABILITIES...

* Moderate in ceilings below 5000 ft Wednesday.

&&

.PREV DISCUSSION...
Issued at 319 PM EDT Tue Oct 17 2023

DISCUSSION...

An expansive stratus deck continues to hold across most of SE MI
underneath a low-level inversion located between h850-h800, per
ACARS soundings. Diurnal heating has helped reinforce some strato-cu
where breaks have been observed. Continuation of mostly cloudy to
cloudy skies are expected through the evening as a shortwave, now
over northern lower Michigan, drives south across the cwa. Dry
weather prevails tonight and overnight given the dry antecedent
conditions in the mid-levels. Low-level flow flips from west to
southwest following the passage of the wave, cutting off the subtle
advection of lake moisture which will afford the chance for some
overnight clearing. This trend is now observed across far southwest
Michigan, working inland. Lows will hold on in the mid-40s with cloud
coverage but will rapidly drop into the upper 30s to low 40s with
any appreciable periods of clearing.

Shortwave ridging will re-establish across Michigan tomorrow in
advance of the next upper-level wave, which at present time is
progressing across Montana. This wave will traverse southeast across
the Midwest tomorrow and will arrive over Michigan on Thursday.
System relative mid-level isentropic ascent will commence ahead of
this wave Wednesday afternoon and evening, but with the substantial
wedge of dry air below (dew point depression of 22 at 700mb), rain
will be difficult to come by. PoPs are capped at 10% during this time
frame. Rain is expected to fill in from west to east on Thursday
morning (likely after 06Z) along a weak cold front that moves in
between 06Z-15Z. Ample moisture transport is expected ahead and along
the front with the boundary-parallel southwest flow. PW values
briefly peak near 1.00". This will likely result in light widespread
rain for the morning.

The upper-level wave and associated clipper low pressure system will
then bring scattered to numerous rain showers throughout the
afternoon and evening. Breezy conditions will also accompany the
rain, where gusts around 25 mph will be likely, once mixing depths
improve. Once the main wave progresses downstream into
Ontario/Quebec, the upper-level trough still holds through Friday
morning where weak cold air advection under northwest flow will take
place. This brings additional chances for drizzle or light showers
leading into Friday afternoon.

Confidence regarding precipitation chances and coverage decreases
considerably on Saturday. The EPS/GEFS/CMCE ensemble mean place the
Great Lakes within the greater longwave trough pattern, but when
viewing medium range ensembles via cluster analysis, all the GEFS
and every single CMCE member outside of one, all cluster on one
solution. This is unusual four days out and leads one to believe
they are a little too overconfident. Troughing is less pronounced in
this cluster and holds most qpf east of the cwa, outside of light
scattered rain chances. There is higher intramodel spread within the
EPS members, all to do with some degree of stronger amplification of
the trough relative to the ensemble mean. When looking at the
control/deterministic model, a strong wave carves within the trough,
which would bring another round of widespread rain Saturday morning
and afternoon. This uncertainty is represented by 30-40% PoPs on
Saturday at this time, but the widespread rain scenario is viable and
is worth noting. Confidence builds that high pressure affects the
the region Sunday into early next week, which will bring dry weather
and steadily increasing temperature trends.

MARINE...

Area of high pressure to the north is beginning to move out of the
area ahead of the incoming low pressure system. Favorable conditions
will remain in place through the rest of the day today, with light
southwesterly winds and small waves. Winds will increase throughout
the day tomorrow as the low pressure gains control. Winds will peak
between 20-25 knots on Wednesday night into Thursday morning, with
gusts reaching above 25 knots. Small Craft Advisories will likely be
needed for Wednesday night and Thursday. Given the direction of
flow, winds will be the primary concern for this system, but waves
of 4+ feet are well within the realm of possibility. The system will
bring showers to the area as well, beginning on Thursday morning and
continuing through the end of the week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 10 PM Wednesday to 10 PM EDT Thursday for
     LHZ421-422-441>443.

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

$$

AVIATION.....CB
DISCUSSION...AM
MARINE.......BC


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