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000
FXUS63 KIND 140500
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
100 AM EDT Sun Apr 14 2024

.KEY MESSAGES...

- Mostly Clear and Mild tonight.
- Partly cloudy and warmer on Sunday; Breezy
- Chance for an afternoon and evening shower or storm mainly east on
  Sunday.
- Ongoing River Flooding
- Multiple rounds of showers storms next week, severe weather
  possible Tuesday and Wednesday
- Cooling trend late next week.

&&

.FORECAST UPDATE...
Issued at 715 PM EDT Sat Apr 13 2024

A low-amplitude shortwave trough within the polar jet is seen in
water vapor channel imagery over Saskatchewan now and will pass
through the Great Lakes early tomorrow. Preceding this will be
strengthening low-level flow across our area and modest moisture
advection leading to warmer conditions tonight. Midlevel clouds from
the wave`s modest moisture connection and ascent will pass through
late tonight and early tomorrow. Statistical, raw, and blended
guidance are clustered fairly tightly for temperatures tonight, so
no adjustments are needed. Our temperature forecast tomorrow is at
about the 75th percentile which given warm plume advecting in and
mixing is reasonable.

Looking at the latest model data for tomorrow`s convective
potential, there is little change in our thinking, but perhaps
slightly more pessimistic. The aforementioned wave will nudge a
weakly baroclinic cold front into central Indiana, but forecast
soundings show a capping elevated mixed layer present. With
ascent/cooling from aforementioned shortwave already having passed,
the only mechanism for convective development would be (1) enough
moistening and heating of the PBL, which does not look sufficient
given the magnitude of the EML, and/or (2) frontal convergence.
Since LCL-LFC layer winds are parallel to the front keeping parcels
from detraining away from mesoscale ascent and convective-scale
repeated moistening/cooling, it`s possible that isolated
thunderstorms could develop. Longevity is likely to be limited given
the hostile thermal environment and any convection that does form
would diminish with loss of diabatic surface heating by mid-evening.

&&

.SHORT TERM (This evening through Sunday)...
Issued at 253 PM EDT Sat Apr 13 2024

Synopsis:

Surface analysis this afternoon shows high pressure centered over
the Gulf Coast, with a ridge axis extending north across western KY
and the Wabash Valley to Lake Michigan. This was resulting in dry
westerly flow across Central Indiana. GOES16 shows clear skies
across Indiana and much of the region due to the ongoing subsidence
with the approach of an upper ridge exiting the Rockies. Dew points
were dry, mainly in the 30s. Meanwhile a weak surface low, failing
to produce any precipitation and little cloud cover was found over
the Dakotas.

Tonight...

Quiet, dry weather is expected tonight. The surface ridge over the
Wabash is expected to continue to drift east, reaching Appalachia
and the east coast by Sunday. Warmer southerly flow is expected to
develop overnight on the backside of the ridge. Furthermore a
moderate pressure gradient aloft is expected to develop, allowing
for some mixing to persist overnight. Meanwhile aloft, northwest
flow is expected to remain in place as ridging aloft remains over
the Plains states, continuing to provide some subsidence, keeping
the mid and lower levels dry. Forecast soundings reflect this, only
showing some high clouds passing overnight within the upper flow,
Thus have trended the forecast toward a partly cloudy sky. Since
warm air advection and some mixing will remain in play, a mild night
is expected with lows falling only to the middle and upper 50s

Sunday and Sunday Night...

Quiet weather is expected to start the day as conditions from the
previous night remain relatively unchanged. The weather feature of
concern on Sunday afternoon and Sunday evening will be related to
the previously mentioned Dakota surface low. This feature is
expected to pass well north of Central Indiana overnight, reaching
NY state by Sunday afternoon. As this occurs, a weak cold front is
expected to sag southward, trailing the low. This weak front looks
to have limited moisture, and really appears to be a cusp like
feature on the tail of weak cold front.

Forecast soundings on Sunday afternoon and Sunday evening suggest
attainable convective temperatures resulting in CU development.
However a mid level inversion remains in place. Farther aloft,
elevated CAPE around 1000 J/KG will be present above the cap. Pwats
appear near 1 inch are available should the cap break, but the
inversion appears strong. Aloft no forcing is available to help add
a lifting element. Thus any showers/storms will be mainly driven by
weak lower level convergence and daytime heating. The cap should be
weakest in parts of far eastern Central Indiana during the afternoon
and early evening. HRRR suggests some development across the eastern
parts of the forecast area at that time. Overall, confidence is low
for this event, but given the weak signal, small chc pops during the
afternoon and evening appear reasonable.

Given the southerly flow and mixing expected through the course of
the day, as well as plentiful sunshine and heating through early
afternoon, highs in the upper 70s to lower 80s will be possible.

On Sunday night after any of the precipitation ends, partly cloudy
skies will linger as weak high pressure from the north once again
settles across the area. A significant change in air mass is not
expected, leading to another night of low temperatures on Sunday
night in the upper 50s to around 60.

&&

.LONG TERM (Sunday night through Saturday)...
Issued at 253 PM EDT Sat Apr 13 2024

Monday through Wednesday...

Look for the long term period to start off relatively quiet as a
weak cold front settles near far southern portions of central
Indiana by daybreak Monday. This may keep highs slightly cooler than
Sunday, but dewpoints in the mid 40s to low 50s behind the front
should be more noticeable. Greater PBL moisture over far southern
counties could promote isolated showers and thunderstorms once
sufficient daytime heating occurs. If storms develop, moderate
destabilization combined with effective bulk shear around 25-35 kts
support a few strong-severe storms. The main threats would be
damaging wind gusts or large hail. Confidence in this severe
potential is low at this time because of questions regarding
convective coverage due to weak forcing and where the front stalls.
Expect any diurnally driven convection to dissipate during the
evening hours.

Rain chances increase late Monday night into Tuesday as a surface
low associated with a negatively tilted trough approaches the
region. Strong diffluence aloft and isentropic ascent/warm air
advection suggest showers and storms are likely during this
period. There is a chance some of these storms could be strong to
severe, but the greater severe threat appears to be from Tuesday
evening into Wednesday as a somewhat narrow corridor of stronger
low- level theta-e advection occurs ahead of a cold front moving
in. Strong deep-layer shear and destabilization from warm-moist
advection supports the potential for severe weather well into the
overnight hours. Some uncertainties still remain in exact details.
These finer details should become clearer over the next 24-36
hours once higher resolution models begin to resolve this setup. A
strong pressure gradient from the aforementioned system
traversing the region will result in windy conditions Tuesday and
Wednesday. Increasing southerly flow is going to help keep
temperatures above normal.

Thursday onward...

Precipitation chances linger through the extended period due to
broad upper troughing. The best chance for additional rain looks to
be late Thursday as another cold front moves through. Temperatures
dropping into the 30s raises the concern for frost by late week
though winds look to remain elevated at this time. Highs are
expected to drop into the 50s for many areas on Friday with cold air
advection over central IN.

&&

.AVIATION (06Z TAF Issuance)...
Issued at 1259 AM EDT Sun Apr 14 2024

Impacts:

- Non-convective low level wind shear during the night

Discussion:

A low level jet will bring low level wind shear conditions to the
sites tonight which will end not long after 13Z as mixing commences.
50kt winds will exist within the jet.

VFR conditions are expected through the period. Some mid and high
clouds will move in during the first several hours of the period,
then diurnal cumulus will pop up in the afternoon. These will
persist into the evening hours. Any isolated convection this
afternoon and evening should remain east of the sites.

&&

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

$$

UPDATE...BRB
SHORT TERM...Puma
LONG TERM...Melo
AVIATION...50