Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/13/24

Area Forecast Discussion

National Weather Service Indianapolis IN

 920 PM EDT Tue Mar 12 2024

.KEY MESSAGES...

- Partly Cloudy and Mild through Wednesday

- Showers and storms likely at times Wednesday night into Thursday
night.

- Conditional severe weather threat on Thursday afternoon and night.

- Much colder early next week with sub-freezing temperatures.

&&

.FORECAST UPDATE...
Issued at 920 PM EDT Tue Mar 12 2024

The elevated fire danger has ended with sunset and winds dropping
off. Otherwise, an upper wave, currently over the Ozarks, will move
into the Wabash Valley toward daybreak. Would not completely rule an
isolated shower out, over the Wabash Valley, toward daybreak
associated with that feature, but with Hi-Res soundings showing very
dry air in place in the lower and mid levels, confidence is too low
to put low PoPs in the grids. The bigger story will be temperatures
as southwest winds have dropped off, dew points were in the 30s and
soundings are showing an inversion setting up. That said IR
satellite and obs were indicating plenty of cirrus around. This and
the light southwest winds should keep temperatures from dropping any
further than the mid to upper 40s. The big temperature and dew point
spreads will assure fog does not form.

&&

.SHORT TERM (This evening through Wednesday)...
Issued at 239 PM EDT Tue Mar 12 2024

Synopsis:

Surface analysis early this afternoon shows a large area of strong
high pressure centered over over AL, with a ridge axis extending
northeast near the Appalachians. Weak low pressure was found over
the UP of Michigan. This was resulting in moderate southwest surface
flow across Central Indiana due to a moderate pressure gradient.
GOES16 shows only some high CI across Indiana associated with a weak
upper wave passing through the Ohio Valley.  Overall the high
pressure system to the southeast was in control of our weather.
Radar across the region was quiet. Dew points in Central Indiana
were quite dry, in the mid to lower 30s. Water Vapor imagery shows
an upper short wave over eastern Kansas.

Tonight...

Another quiet, mild night is ahead.

The large, dominating high pressure system to the south will
continue to maintain overall control  of our weather, as it slowly
drifts east. Meanwhile the upper level weather system over the
plains is expected to drift to the Ohio Valley late tonight, along
with a weak area of low pressure, this system is currently not
producing any precipitation and is not expected to as it arrives
across our state.  ACARS soundings continue to show a very dry
column across Indiana. This will prevent this system from having any
impact other than the passing of some high clouds. Forecast
soundings remain dry overnight as time heights show a bit of lift
with the approach of the weak wave. Still, everything remains
moisture starved. Thus will aim for just a partly cloudy and mild
night. As heating is lost any gusty winds across the area will
subside, but warm southerly flow is expected to persist. Thus will
trend lows toward the upper 40s to near 50s.

Wednesday...

In the wake of the overnight shortwave, ridging aloft is
expected to once again build across Indiana and the Ohio Valley.
This is expected to lead to continued subsidence through the day.
Forecast soundings do not become saturated, although convective
temperature may be reached resulting in some scattered CU. Thus
partly cloudy skies.

Meanwhile at the surface, southerly flow with a moderate pressure
gradient will remain in place. This will keep some gusty wind
conditions in place across Central Indiana again Wednesday, although
as the gradient appears a bit weaker, gusts may only reach 10-20
mph. Warm air will continue to arrive on southerly winds, allowing
for good mixing and heating once again. Look for highs around 70 or
in the lower 70s.

&&

.LONG TERM (Wednesday night through Tuesday)...
Issued at 239 PM EDT Tue Mar 12 2024

Wednesday Night Through Friday.

Rain chances will gradually begin to increase Wednesday night as a
warm front pushes northward with the parent upper level trough
tracking from Kansas into the Great Lakes Region. Models have come
in better agreement with the track of the parent low pressure system
with central Indiana well within the warm sector for the duration of
the event. Best chances for rainfall will be towards daybreak
Thursday and across the northern counties which will be closer to
the warm front during the period of best forcing. Even with robust
cloud cover Thursday, the warm antecedent airmass combined with
robust southwest flow will be more than enough to bring
temperatures to near 70.

Forecast details with this system Thursday afternoon into Thursday
night remain quite fluid with a lot of uncertainty as to how the
overnight/early morning convection will impact the severe weather
threat later into the day.  The LLJ will be maximized over central
Indiana during the afternoon and evening hours but the better
instability will be further to the south and west where the better
lapse rates are expected. Thus a conditional severe weather risk is
expected for Thursday afternoon with marginal ingredients for severe
weather but will be dependent on mesoscale factors that are very
uncertain at this time. The better severe weather risk will
generally be in the western to northwestern portions of the area
based on the expected CAPE axis with the best shear across northern
Indiana.

The current expected scenario would be fairly dry and quiet
conditions from daybreak through early afternoon with convection
generally across the warm front in northern Indiana through the
afternoon hours with additional strong to possibly severe weather
during the overnight as any storm complexes over Illinois where the
better daytime instability will be would be potentially moving into
Indiana. Primary threats with this conditional risk would be
damaging winds and large hail with the greater tornado threat across
Missouri and Illinois. The cold front associated with the system
looks now to move through during the daytime hours Friday with
additional showers and storms but the best forcing and isentropic
lift will be across Kentucky into Tennessee which will help to limit
the QPF and associated flood potential.

Saturday Through Tuesday.

Somewhat cooler but still generally near to above normal
temperatures are expected for the weekend with a very strong upper
level low over southern Canada and a strong jet stream overhead.
Subtle waves within the broader trough may bring precipitation to
the Great Lakes region but confidence is low at any given point with
ensembles showing a wide range of potential solutions. At this time
the period where confidence is highest for any snow looks to be late
Sunday night into early Monday but with the robustness of the cold
air aloft and steep lapse rates this could easily be a situation
where sprinkles/flurries are more widespread than currently
expected. Where confidence is higher is that early next week will
end up much colder once the trough moves further to the east and
polar air works into the area. Sub-30 degree temperatures look
likely Monday night and/or Tuesday night with the potential for a
hard freeze which could cause issues for plants after a very warm
week this week.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 644 PM EDT Tue Mar 12 2024

Impacts:

- Very small chance of a thunderstorm after 09z at KLAF
  and KHUF

Discussion:

There is a very small chance that an upper wave and weak instability
could trigger an isolated thunderstorm at either KLAF or KHUF 09z-
12z, otherwise, should only see high and possibly mid clouds through
the TAF period. Wind gusts should end at or very shortly after
issuance time with winds generally from the southwest to 10 knots or
less.


&&

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

$$

UPDATE...MK
SHORT TERM...Puma
LONG TERM...White
AVIATION...MK