Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/15/24

Area Forecast Discussion

National Weather Service Indianapolis IN

 1013 PM EDT Sun Apr 14 2024

.KEY MESSAGES...

- Ongoing River Flooding
- Multiple rounds of showers and storms this week, severe weather
  possible late Tuesday and Wednesday
- Cooling trend late next week

&&

.FORECAST UPDATE...
Issued at 1012 PM EDT Sun Apr 14 2024

No significant changes made to the forecast with this evening`s
update.

IND ACARs soundings and satellite imagery indicate that mid level
capping around 750-800mb and lack of moisture prevented convective
development along a cold front slowly pushing through North Central
Indiana this evening. Latest satellite imagery does show convection
developing along the front further east in Ohio and slowly building
further west. Confidence remains moderate to high that any
convective development should stay east of the IN/OH border as the
front slowly sags southward through the night.

Mainly expecting a wind shift to the northeast behind the front with
lowering humidity values. Lack of cold air behind the front will
allow for another very warm day across Indiana with highs once again
in the upper 70s and lower 80s. Pressure gradient relaxes as well
behind the front as high pressure builds in from the north. Expect
winds tomorrow to be much lighter than they were Sunday with
northeasterly to easterly winds at or below 10 mph.

&&

.SHORT TERM (This evening through Monday)...
Issued at 140 PM EDT Sun Apr 14 2024

With the latest observations and short term model trends, it seems
low-level moisture will be insufficient for convective initiation
this far west at the peak of this diurnal cycle. Most/all of the
convection should be relegated to Ohio and Pennsylvania ahead of the
low-amplitude shortwave perturbation. Further west into Indiana,
wake subsidence will maintain/enhance capping elevated mixed layer.
It does not appear that convection will initiate via frontal
convergence and diurnal destabilization alone, and would need large
scale ascent and/or richer low-level moisture to overcome the
hostile thermal profile.

Some of the most aggressive HREF members do show convective cells
behind the front after the peak of the diurnal cycle. This appears
to be tied to moisture convergence near the boundary and moisture
that is redistributed to the top of the mixed layer, so it may be
the models` attempt at convection that fails due to capping and dry
entrainment. We may see enhanced cumulus near the front and some
glaciation on satellite with isolated brief showers, but sustained
deep convection seems unlikely given our current analysis.

Post-frontal air mass on Monday will be drier but only a few degrees
cooler with light northeasterly winds. The front will stall across
southern Indiana. With ridging and subsidence reinforcing the
capping elevated mixed layer, thunderstorm development should be
isolated Monday afternoon along the front. Richer low-level moisture
will be present near the front, however, so chances of initiation
are better than today. If the front stalls slightly further north
than indicated now, our southernmost counties will be in play for
isolated convection and so we will continue with low probabilities
and "isolated" wording there.

&&

.LONG TERM (Monday night through Sunday)...
Issued at 140 PM EDT Sun Apr 14 2024

Monday night, as warm advection strengthens preceding a mid-latitude
system emerging onto the Plains, some convection will be possible
near and north of the northward-moving warm front. Coverage should
still be limited, however. Any warm advection-driven precipitation
Tuesday morning should shift north of the area by afternoon placing
us fully within the warm sector. Since large scale ascent will hold
back to our west during the daytime, we will lower precipitation
probabilities during the afternoon hours.

Convective evolution upstream with Tuesday`s diurnal maxima is
somewhat uncertain, but should be confined to near the Pacific
front/dryline hybrid within the core of the warm conveyor belt and
narrow rich moisture plume. The degree of upscale growth is in
question but with the current model data it seems probable that a
band of convection will enter Indiana by evening and progress
eastward through the state overnight. Strong mid-upper flow
elongating hodographs and the presence of at least a small amount of
instability will be enough for some severe storm potential
overnight, although convection may tend to outpace the instability
and weaken as it moves into Indiana.

Early on Wednesday, the weakening and increasingly stacked low is
shown in models to be over Wisconsin with a trailing cold front
moving through Indiana during the afternoon. Recent model cycles
have slowed its progression. An axis of low-level moisture preceding
this front coupled with diabatic surface heating should result in
sufficient instability for convection Wednesday afternoon.
Complicating factors from departing convection and wake subsidence,
veering/unidirectional flow as low weakens and isallobaric component
lessens, and frontal timing lead to an unclear picture of severe
storm coverage and magnitude. Nevertheless, the general pattern is
supportive of severe thunderstorms.

A cooler and drier post-frontal air mass will arrive Thursday and
continue into next weekend as a broad trough forms over Canada.
Perturbations within fast westerlies at its southern periphery could
bring low precipitation chances, mainly late Thursday into Friday.
However, deeper moisture will be relegated to lower latitudes so
coverage, intensity, and amounts will be limited.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 736 PM EDT Sun Apr 14 2024

Impacts:

- Wind diminishing after sunset and becoming northerly through the
overnight hours

Discussion:

VFR conditions will prevail into Monday. Wind gusts should gradually
decrease around sunset this evening once mixing slows. A weak cold
front will bring a wind shift to north-northeast through the
overnight hours, however winds are expected to remain light under 10
kts. Adjusted timing of the wind shift a few hours later towards 12z
Monday for KIND, KHUF, and KLAF as latest guidance shows the wind
shift around that time.


&&

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

$$

UPDATE...CM
SHORT TERM...BRB
LONG TERM...BRB
AVIATION...CM