181 
FXUS63 KIND 131739
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
139 PM 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.

&&

.FORECAST UPDATE...
Issued at 948 AM EDT Thu Jun 13 2024

The forecast remains in good shape with only minor adjustments needed 
to match observations. Current satellite imagery shows mostly clear 
skies across central IN as surface ridging remains in place. Expect 
quiet weather conditions to persist for much of today before a 
complex of storms begins to approach this evening. More details on 
the potential for storms is provided in the short term discussion. 
Additional updates on thoughts for timing and the threat of damaging 
wind gusts or severe hail will be sent out in the afternoon forecast 
package. 

Increasing southerly flow and plentiful sunshine will lead to warmer 
temperatures in the upper 80s to possibly low 90s in a few spots. 
Today will likely end up being the warmest day of the day so far. 
Thankfully dewpoints are going to remain in the 50s for most 
locations so heat indices should remain below 90F. Still make sure 
to stay hydrated and take breaks if you are outdoors this afternoon 
as it will be hot.

&&

.SHORT TERM (Today and tonight)...
Issued at 304 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 304 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 (18Z TAF Issuance)...
Issued at 137 PM EDT Thu Jun 13 2024

Impacts:

- Thunderstorms arriving after about 03z tonight.
- Lingering MVFR ceilings in the wake of shower/storm activity 
  possible Friday morning.

Discussion: 

VFR conditions expected through this afternoon. Generally 
southwesterly winds with occasional gusts 15-20 knots can be 
expected.

A cold front approaching from the northwest will trigger 
thunderstorms across northern Illinois this evening. These storms
should then progress southeastward into Indiana tonight. The main
forecast challenge will be storm intensity, as most guidance 
shows weakening with time. Still, nearly all members of guidance 
depict shower/storm activity affecting most terminals. Will 
include a tempo group for thunderstorm at LAF and IND, where 
greater intensity storms may occur. Will mention VCTS south for 
BMG where weakening allows for a bit more ambiguity in terms of 
impacts.

Showers/storms should be mostly out of the area between 08-10z. 
Lingering MVFR ceilings are possible in the wake of the storm 
complex Friday morning, but should clear out later in the day.

&&

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

$$

UPDATE...Melo
SHORT TERM...Eckhoff
LONG TERM...Eckhoff
AVIATION...Melo