Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 02/26/23

Area Forecast Discussion

National Weather Service Detroit/Pontiac MI

 557 PM EST Sat Feb 25 2023


.AVIATION...

Ongoing low level warm air advection within west-southwest flow is
quickly reducing the Lake Mi moisture flux, a trend that will
continue into the evening. While the most recent ACARS soundings
still have a respectable moisture layer trapped under a deep
inversion, satellite trends over the last hour have really been
showing an acceleration of clearing upstream across SW Lower Mi and
NW Indiana. Increased winds along the inversion is perhaps allowing
for better mixing of dry aloft into the cloud layer. Given the
current trends, the clearing of the low clouds will be bumped up to
the 01Z to 03Z time frame in the TAFs. There will be a shallow near
sfc stable layer which will keep some of the stronger winds (30-
40kts) aloft overnight, holding sfc winds around 10 knots with a few
gusts around 20 knots possible.

DTW THRESHOLD PROBABILITIES...

* None.

&&

.PREV DISCUSSION...
Issued at 330 PM EST Sat Feb 25 2023

DISCUSSION...

Subsidence will work into the area late today into tonight behind
exiting mid level disturbance. This should lead to slowly eroding
cloud cover, but southwest to west flow downwind of Lake Michigan
will slow this clearing process to some degree from this evening
into the overnight before an increasingly mild and dry airmass
within expanding shortwave ridge (and coincident surface ridge)
leads to mainly sunny skies on Sunday. With the gradual clearing
overnight, expect temperatures to drop off into the 20s in most
locations with recovery well into the 40s in many areas on Sunday
given the dry and sunny conditions.

The surface ridge maintains its influence on the area into Sunday
night with temperatures falling back into the lower to mid 20s in
calm and initially clear conditions. This will set the stage for the
next significant storm system. This upper low, now positioned off
the southern California coast, will eject quickly into the midwest
and western Great Lakes late Sunday night into Monday. A notable
surge of moisture will overspread the region in advance of this
system with an expanding area of rain encroaching on southern lower
MI during the pre-dawn hours Monday morning and then engulfing the
whole area during the morning/early afternoon.

The initial dry and cold low level conditions associated with the
lingering surface ridge will lead to an initial period of freezing
rain on the front edge of this precipitation shield as evaporative
cooling maintains surface temperatures at over below freezing during
the morning and in some cases afternoon within persistent southeast
flow in advance of the strong surface cyclone that matures to our
west as this southern stream shortwave ejects into the general area.

Northern portions of the forecast area will be most susceptible to
freezing and/or frozen precipitation as not only will the initial
conditions be coldest, but the introduction of milder air as winds
veer to the south will be most delayed. Cold air will be deep enough
to bring some sleet and/or snow into the mix from M-46 north before
a change to freezing rain occurs. Accumulations should remain at an
inch or less.

Further south, freezing rain will change to rain as temperatures
climb into the 30s. Light glazing will be most prevalent in the M-59
to I-69 corridors where some spots may receive up to a tenth of an
inch of ice. Any freezing rain south of this area will be very
limited in duration as surface temperatures climb above freezing
quickly early Monday morning. Overall, with temperatures climbing
into the upper 30s to mid 40s by midday and afternoon, slick
conditions will have a limited duration.

Dry conditions will develop Monday night and Tuesday as high
pressure builds into the area behind this filling system as it
continues into eastern Canada/New England. With a more or less zonal
upper level flow pattern setting up once this system passes, rather
mild conditions will persist with temperatures in the upper 30s to
mid 40s again Tuesday and perhaps 40s to 50s Wednesday as another
weaker low pressure system encroaches on the area. Positioning of
this fast moving system will be difficult to pinpoint, but generally
expect increased precipitation changes again Wednesday.

This midweek shortwave will be ejecting quickly eastward out of a
progressive upper level trough over the western CONUS. At this time,
the next major shortwave working in off the Pacific ocean looks to
dig fairly far south and eject across the southern plains/lower
Mississippi Valley late in the week. If this forecast trajectory
remains consistent, this system will bypass lower MI to the south
around the periphery of high pressure that settles into the area in
the wake of the Wednesday system. Unfortunately, confidence will
remain relatively low for this currently Day 7 forecast until the
evolution of the the earlier week systems comes to fruition.

MARINE...

Southwest winds increasing to 20 to 30 knots this evening ahead of a
cold front will flip to the west by Sunday morning, with solid post
frontal cold advection to tap into wind speeds of 25 to 30 knots,
especially across the northern half of the Lake Huron on Sunday. In
fact, with some channeling and even deeper cold air north of around
and north of Presque Isle, gusts of 30-35 gusts appear likely for a
short period Sunday morning, but with just brief gusts to marginal
gales expected, will not be issuing a gale warning.

Still looking at a strong low pressure system tracking through the
Central Great Lakes early next week. Although high pressure is
retreating over Eastern Canada, should be enough of a gradient to
support easterly winds gusting 30-40 knots on Monday over the bulk
of Lake Huron, and will be issuing a gale watch. Precipitation drag
could end up being a hindrance. The other issue is as the center of
the low tracks through Central/Southern Lake Huron around Midnight
Monday, wind speeds will drop off significantly for several hours
(~6 hrs) before ramping back up to potential gales for Tuesday
morning as cold air sweeps in behind the low. The low is also
weakening as it exits the Great Lakes region. The bulk of European
ensembles are much farther south, with the low tracking close to
Port Huron/far southern Lake Huron. This would result in the north
third/half of Lake Huron having a shorter window of lighter winds,
and thus a bit higher confidence in northwest gales on Tuesday. The
south half and especially the nearshore waters is a complicated
forecast, as even the  first episode of easterly gales on Monday is
not a slam dunk, as confidence in the duration exceeding 3 hours is
not terribly high. And as mentioned, if the low track does in fact
end up farther south, the outgoing wind forecast for early Tuesday
morning is likely too high. Will leave Gale watch out Inner Saginaw,
otherwise will keep it simple and issue long duration gale watch for
rest of Lake Huron 15z Monday-22Z Tuesday to capture the 2 episodes
of gales. Highest confidence, and greatest magnitude of wind looks
to be the easterly gales over the north third of Lake Huron on
Monday, as peak gusts could even potentially sneak just above 40
knots.

HYDROLOGY...

A strong low pressure system will bring widespread precipitation to
all of SE MI on Monday. It appears rain will be the predominate type
for the Metro area south to the MI/OH state line. Further north, the
precipitation will begin as snow, sleet and freezing rain in the
morning and change to rain as temperatures warm into the afternoon.
Some snow accumulation will be possible across the far northern
portions of the Tri-Cities and northern Thumb. Liquid equivalent
precipitation is expected to range between half an inch and three
quarters of an inch with localized one inch amounts possible. This
will result in very minor flooding within poor drainage areas and
some rises on area rivers.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from Monday morning through Tuesday afternoon for
     LHZ361>363-421-441>443-462>464.

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

$$

AVIATION.....SC
DISCUSSION...DG
MARINE.......SF
HYDROLOGY....DG


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.



Area Forecast Discussion

National Weather Service Indianapolis IN

 928 PM EST Sat Feb 25 2023

.Forecast Update...
Issued at 928 PM EST Sat Feb 25 2023

Small patch of low stratus over NW sections late this evening,
beneath a shallow inversion, under the influence of broad surface
high pressure, that extended from the South to the northern Plains.

Meanwhile, cirrus was also moving overhead well in advance of the
Pacific coast system. Temperatures were falling slightly faster than
HiRes and with mainly only high clouds and light to calm winds,
lowered overnight lows a degree to the upper 20s to mid 30s.

&&

.Short Term...(This evening through Sunday)
Issued at 316 PM EST Sat Feb 25 2023

* Warming trend back to above normal temperatures

* Dry through the rest of the weekend

.This evening and tonight...

Latest surface analysis shows an area of high pressure centered over
Southern Missouri slowly moving eastward resulting in light westerly
flow across Indiana Saturday afternoon. GOES16 satellite imagery
reveals an area of low stratus and cumulus clouds extending
southwest from Michigan to Illinois and Indiana and slowly
shrinking. Subsidence under the high has resulted in a strong low
level inversion trapping moisture just above the surface. This area
of lower clouds is evidence of the trapped moisture; however drying
is taking place in this thin saturated layer as daytime mixing
occurs. While clear skies remain over Indianapolis, 19z IND ACARS
soundings still show the inversion in place just under 1 km agl.
With high pressure remaining the dominant weather influence tonight,
expect the inversion to persist into the overnight hours. RAP cross
sections reveal low level moisture remaining in the boundary layer
overnight, so would not be surprised to see continued lower clouds
across Western and Northern Indiana through tonight. Temperatures
overnight fall into the lower mid 30s across Central Indiana. With a
small dew point depression at the surface, confidence further
increases in lower clouds remaining where higher moisture remains
trapped near the surface.

Weak mid level shortwave also passes by to the north overnight,
briefly increasing the surface pressure gradient and low level winds
over the northern half of the state. Winds may pick up to 10 to 15
mph after 03z for the northern portion of the forecast area along
with a slight increase in cloud cover. Overall, quiet weather
persists across the state with lows dropping into

.Sunday...

Zonal flow pattern aloft transitions into ridging in response to a
developing trough in the Plains on Sunday. At the surface, high
pressure continues eastward with southerly return flow setting up
across the region by Sunday afternoon. Warm air advection ahead of
the developing Plains system already begins to influence the are
tomorrow as temperatures aloft begin to climb above 0C and toward
+10C by late Sunday night. Due to subsidence under the high, the
inversion will likely persist through tomorrow as well, limiting
afternoon mixing to under a kilometer. Limited mixing plus high
pressure directly overhead will keep winds very light through the
period as well. While a warmer airmass advects in aloft, those
warmer temperatures will struggle to mix down to the surface due to
the inversion. Still expecting highs to make it into the mid to
upper 50s with abundant sunshine earlier in the day. High clouds
stream in aloft during the later afternoon and evening hours and
continue to lower Sunday night. With continued warm air advection
and clouds, expect temperatures to remain elevated Sunday night in
the 40s to near 50.

&&

.Long Term...(Sunday night through Saturday)
Issued at 316 PM EST Sat Feb 25 2023

Temperatures throughout the long term period will be above normal
with highs oscillating from the 50s to 60s and lows from the 30s to
40s as a couple of systems move across the region.

Models continue to be pretty consistent with this upcoming system
leading to decent confidence at least with with precipitation and
gusty winds. An upper low will move in from the southwest and
southern plains reaching the Great Lakes region by early Monday.
This system will bring precipitation chances starting in the SW as
early Monday due to isentropic lift along the warm front moving
northward. The surface low itself and the associated cold front will
enter the forecast area Monday morning to early afternoon. The best
chances for rain and storms will be from early morning Monday into
midday with slight chances of thunder embedded during the daylight
hours. Storm total QPF continues to be about half an inch to an inch
which shouldn`t cause many issues in terms of flooding. The main
story with this system will be the increased gradient winds set to
move in along and behind the cold front. A LLJ, with a centroid of
60-70 kts at 850 mb will pass overhead which should mix down to the
surface from prior to sunrise throughout the rest of the day with
surface wind gusts potentially getting to around 50 mph at times and
sustained winds near 30 to 35 mph. Within storms and showers
themselves, some stronger to damaging winds could be embedded,
especially across the SE midday if instability creeps in. This
potential for damaging winds has prompted a risk of severe storms
from SPC. Non-thunderstorm winds will drop some by monday night and
will further weaken through the day Tuesday.

Temperatures will dip some Tuesday behind the cold front but are
expected to rebound quickly by Wednesday as southern to southwestern
surface flow returns. There is a small chance of some precipitation
in the far SE late Wednesday into Thursday from a wave but much of
the moisture should keep to the south of the area. Otherwise, a
surface high moving in behind the early week system should allow
for a quiet midweek.

At the end of the period, there remains quite a bit of variability
between models thus leading to quite a bit of uncertainty. A low
should move in from the plains, tracking somewhere between the Ohio
and Tennessee Vallies, but the path and timing of the system remains
highly uncertain. If it ends up further north, central Indiana
could see precipitation for the end of the week and may
potentially contain a mix of winter weather. But if it stays
further south, the weather could stay dry but bring in slightly
cooler temperatures to the area.

&&

.Aviation...(00Z TAF Issuance)
Issued at 522 PM EST Sat Feb 25 2023

Impacts:

- MVFR ceilings possible at KLAF and KHUF this evening,
otherwise, VFR flying conditions and WSW winds less than
10 knots expected through Sunday

Discussion:

GOES 16 visible satellite was showing shrinking stratus deck over
the upper Wabash Valley. There is some concern that this could
result in lingering MVFR stratus this evening for KLAF and KHUF.
Otherwise, high pressure and fast WNW upper flow ahead of potent
west coast system will result in passing cirrus. Meanwhile, modest
surface pressure gradient will keep WNW winds less than 10 knots.


&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

Update...MK
Short Term...CM
Long Term...KH
Aviation...MK