Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 09/24/22

Area Forecast Discussion...UPDATED

National Weather Service Indianapolis IN

 920 PM EDT Fri Sep 23 2022

.Forecast Update...
Issued at 920 PM EDT Fri Sep 23 2022

The lowest condensation pressure deficit and pressure advection on
the 300-305-K surface will pass from around 2am to sunrise time
frame, so this could be when we see some reinvigoration of
stratiform rain across the area. Leading up to this, a preceeding
area of isentropic ascent and gradual low-level saturation has
resulted in trace rainfall amounts across most of central Indiana.
Measurable rain thus far has mostly been confined to rouighly south
of I-70 and west of I-65, where a few locations have receilved up to
0.06". Current radar shows another area of rain in east-central
Illinois capable of another ~trace-0.03" over the next couple of
hours. Another batch, as mentioned above, may bring an additional
few hundredths to a broader area of central Indiana, but overall
totals should mostly remain below 0.10", and for most likely just a
couple hundreths. Warm advection/isentropic ascent regime should
lessen early in the morning bringing an end to the light rain. All
other forecast elements look fine and we`ve only made minor
adjustments to probabilities of measurable based on observational
trends.

&&

.Short Term...(This evening through Saturday)
Issued at 249 PM EDT Fri Sep 23 2022

Early this afternoon, clouds continued to increase and thicken
across central Indiana from the west. Areas of sprinkles and some
isolated showers were across central Illinois and were moving east.
Surface high pressure was across the area, with an upper system
across the northern Plains states.

ACARS and model soundings continue to indicate very dry lower levels
of the atmosphere across the area this afternoon. Some of the rain
moving in from Illinois should diminish, with much of what`s left
not reaching the ground. Will continue with a sprinkles/isolated
shower mention across the west half of central Indiana before 00Z.

Tonight, warm advection ahead of the upper system moving through the
northern states will spread across the area. Moisture in the low
levels of the atmosphere remains quite limited. Expect the clouds to
continue to thicken and lower, and some isolated to scattered
showers will be around in the warm advection pattern. Will mention
sprinkles as well.

Clouds will help keep temperatures warmer than last night, with lows
in the 50s expected.

Isentropic lift will exit the area by early Saturday. Wouldn`t rule
out some sprinkles in the morning, but much of the day looks dry.
Clouds will decrease as lift moves east and drier air works in.
Southwest winds along with sunshine will boost temperatures back
into the 70s.

&&

.Long Term...(Saturday night through Friday)
Issued at 249 PM EDT Fri Sep 23 2022

A broad cut-off upper-level low is approaching from the west today.
As this feature becomes reintegrated into the main belt of
westerlies, Hurricane Fiona is expected to become extratropical and
occlude over maritime Canada. The resulting powerful cyclone will
then slow down and buckle the flow a bit, allowing troughing to
amplify significantly over the eastern US in tandem with ridging out
west. A weak surface reflection of the approaching upper-level wave
will also deepen as the trough amplifies. Northwesterly flow and
weakly unstable air behind this system may lead to a few scattered
showers or perhaps an isolated thunderstorm on Sunday, mainly in our
northeastern counties. Dry air will limit the amount and coverage of
precipitation, however. Steepening lapse rates could also lead to a
rather gusty day on Sunday as strong low-level winds on the back
side of the strengthening low are mixed down to the surface. Gusty
conditions may persist into Monday as well with similar conditions
aloft.

Once that system exits the region, strong surface high pressure will
then move in with continued troughing in the upper levels. The
combination of light northerly surface flow and cold temperatures
aloft will lead to cooler than normal conditions prevailing through
the week. Generally clear skies during this time period will enable
relatively large diurnal temperature swings. Temperatures will
struggle to reach 70 most days, and lows may creep into the upper
30s in a few spots. Despite ideal conditions for radiational
cooling, not currently expecting widespread fog outside of the
usually fog-prone areas (valleys, near rivers, basins and corn
fields). Some diurnal cumulus may develop most days as model
soundings show efficient mixing during the afternoons. Otherwise,
expect sunny and dry but cool weather through Friday.

&&

.Aviation...(00Z TAF Issuance)
Issued at 740 PM EDT Fri Sep 23 2022

Impacts:

* Periodic light rain this evening and overnight; no visibility
  impacts.

* Brief periods of calm or variable wind, especially during the
  evening.

Discussion:

A period of warm advection/ascent will lead to light rain across
portions of the area. Winds may be calm/variable for a period before
more reliably becoming southeasterly through the night. Slight
veering to southwesterly tomorrow afternoon with deeper mixing and
slightly stronger speeds as well as possible gustiness. Otherwise,
VFR conditions are expected to prevail.


&&

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

$$

Update...BRB
Short Term...50
Long Term...Eckhoff
Aviation...BRB