558
FXUS63 KIND 130703
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
303 AM EDT Thu Jun 13 2024

.KEY MESSAGES...

- Warming trend continues today with highs near 90F.

- Thunderstorms possible this evening into tonight...with possibly a
  few strong/severe cells north of I-70.

- Hot and humid trend starts Sunday.

&&

.SHORT TERM (Today and tonight)...
Issued at 303 AM EDT Thu Jun 13 2024

Our primary forecast challenge in the short term is convective
activity arriving around 00z this evening.

WINDS and TEMPERATURES

A shortwave and associated cold front are approaching from the
northwest. The shortwave itself looks to pass to our north, but the
cold front sags southward and should arrive early Friday morning.
Warm southwesterly winds could gust up to 20mph today as the MSLP
gradient tightens ahead of the approaching front. In addition to
storm chances, the front will lead to a brief cool down in a pattern
that favors continued warming. Winds turn northwesterly after
frontal passage and colder air gradually filters into the region.
Though Friday may be a bit cooler, it shouldn`t be that much
cooler...only a few degrees at most with highs in the mid 80s as
opposed to near 90 today. Lows Friday night may bottom out near 60
across our northern counties and in sheltered areas or valleys
elsewhere. Temporarily reduced temperatures continue into Saturday
as well with highs in the mid to upper 80s.

CONVECTIVE POTENTIAL AND HAZARDS

Guidance is in fairly good agreement showing convective activity
igniting along the front across SE Iowa and northern Illinois. These
storms should organize into a cluster given high DCAPE and potential
for efficient cold pool generation/growth. Shear vectors are not
boundary-parallel, however, so initial activity may remain discrete
for a few hours before upscale growth occurs. This may also negate
system longevity with southeastward extent as cold pool shear
balance will be harder to achieve. Any resulting MCS may quickly
become outflow dominant as it heads into our CWA from the northwest.
Additionally, model CAPE diminishes quite quickly as one heads south
and east through central Indiana. This all points to a weakening
system as it moves through central Indiana.

In terms of hazards, strong to severe wind gusts are most likely.
The greatest potential being further northwest where storms are
strongest. Severe potential diminishes quickly as one heads south
and east. Still, anywhere from Terre Haute, to Indianapolis, to
Muncie may see a strong wind gust as thunderstorms move through.

Storm timing again looks to be this evening, around 00z near
Lafayette, to as late as 04z by Bloomington. There remains some
variation within guidance but most are within this range. Timing
also depends a bit on convective evolution and how quickly upscale
growth occurs. Lingering rain/cloud cover may hold on to as late as
12z in the MCS`s wake.

&&

.LONG TERM (Friday through Wednesday)...
Issued at 303 AM EDT Thu Jun 13 2024

The primary forecast challenge in the long term is heat and
associated heat related hazards.

SYNOPTIC OVERVIEW

Guidance is in good agreement showing a trend towards east coast
ridging and southwesterly surface flow across Indiana. In a nut
shell, this means a warming trend appears likely. But how much
warming? Ensemble guidance shows rather anomalous ridging from
Sunday onward. In fact, both the NAEFS and ECMWF ensembles show 99th
(or higher) percentile height anomalies at 200b and 500mb. The ridge
depicted within guidance is broad, stretching from the Plains into
the northeastern US and even into the Atlantic Ocean. The
deterministic ECMWF shows 600dm heights by mid-week centered over
Indiana.

Beyond next week, ensemble guidance diverges and shows little to no
coherent signal. As such, little can be discerned synoptically in
the 8-14 period. But sustained ridging into the end of June does not
appear as likely by this point, and a trend back towards normal
weather is favored.

PRECIPITATION

While a strong ridge favors above to much above normal temperatures,
precipitation anomalies can be a bit more of a challenge. Guidance
shows sustained moisture advection from the gulf around the western
edge of an east coast surface high. This may lead to "air mass"
thunderstorms at times once the ridge and heat really settle in.
Additionally, decaying cold fronts may occasionally dip far enough
south to initiate some convection. However, this may not materialize
as the jet stream looks to be far north across Canada. The synoptic
storm track may be simply too far away to bring a front this far
south. This depends on how amplified the ridge becomes. Coincident
with this analysis, CPC 6-10 and 8-14 day outlooks favor warmer than
normal conditions and near-average precipitation. We will carry
slight chance PoPs at times from Tuesday onward to account for pop
up afternoon convective potential within the core of the ridge.

TEMPERATURES

Guidance is in good agreement showing highs reaching at least 90
most of next week. A limiting factor regarding max temperature
potential is moisture advecting from the south. Dew points look to
be high most of next week, with readings 65 to 75 likely much of the
time. This moisture may limit the depth of boundary layer mixing and
therefore max temperature potential. However, it also has the effect
of raising the heat index to potentially excessive levels. The NWS
Heat Risk tool shows major to extreme heat risk for much of the area
Monday onward. Multi-day prolonged heat potential with little
overnight relief adds to the risk by mid to late week.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 606 PM EDT Wed Jun 12 2024

Impacts:

- None.

Discussion:

VFR conditions will continue. Winds may vary slightly during the TAF
period by around 30 degrees or so with the diurnal cycle, but
generally southwesterly. Mixing may be enough for momentum transfer
and gusts up to around 15-20 knots Thursday afternoon.


&&

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

&&

$$

SHORT TERM...Eckhoff
LONG TERM...Eckhoff
AVIATION...BRB