041
FXUS63 KIND 281615
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
1215 PM EDT Fri Jun 28 2024

.KEY MESSAGES...

- Increasing clouds and humidity today
- Rain and storms return Friday night into Saturday
- A few strong to potentially severe storms possible Saturday

&&

.FORECAST UPDATE...

- Partly Sunny and warm this afternoon

Surface analysis late this morning shows strong high pressure
centered over upstate NY. This high was influencing the weather
across the eastern third of the country, including Indiana. The high
was providing southeasterly flow across Central Indiana. Surface low
pressure was found over NB. Warm and moist southerly flow was found
streaming northward through the Mississippi river valley, where
abundant cloud cover was found. A large area of showers and
thunderstorms were found over MN/IA and western MO. Water vapor
imagery showed a mainly zonal flow in place across the CONUS, with a
wave of moisture in place from the southern plains to MN and WI. Dew
points across central Indiana were mainly in the upper 50s and lower
60s.

ACARS soundings this morning shows a dry mid level in place across
Central Indiana, with saturation aloft, indicative of the high
clouds passing within the flow aloft. Through the afternoon, the low
pressure system to the west is expected to make slow progress
northeastward, limiting any impact across Central Indiana. Models
suggest that the strong high to the east will slow that approach,
allowing only the passage of high clouds across Central Indiana
through the day as seen on GOES16. Forecast soundings today show a
mid level inversion, with convective temperatures in excess of 90
degrees. Thus with the high cloud cover convective temps will not be
reached. We will look for partly sunny skies this afternoon with
highs in the middle to upper 80s. Overall, ongoing forecast handles
all of this well.

&&

.SHORT TERM (Today and tonight)...
Issued at 201 AM EDT Fri Jun 28 2024

We continue in the synoptic pattern of low-amplitude shortwave
troughs periodically passing to our north, causing a north-south
slosh of richer moisture. Humidity was fairly low yesterday but will
return today. The mixing process may slow the return some, but
once mixing subsides a northward flux of rich moisture should
accelerate.

All of this is in response to the next upstream shortwave trough.
Convection is ongoing now from the northern Plains into the northern
Mississippi Valley, fed by ongoing warm/moist advection. Although
its easterly track will bring it into a comparatively more stable
environment later today, one or more MCVs may evolve and move into
Indiana. Midlevel clouds and some light precipitation would be the
most likely outcome late this afternoon.

Continued moisture advection into the evening and overnight should
result in an increase in coverage of convection and/or maintenance
of upstream convection from the diurnal temperature maximum.
CAPE/shear values would be marginally supportive of severe storms,
especially for any well-organized cold pool-driven systems that
made it this far east.

&&

.LONG TERM (Saturday through Thursday)...
Issued at 201 AM EDT Fri Jun 28 2024

Saturday and Saturday Night

The long term will begin fairly active with rain expected along with
the potential for a few strong to severe thunderstorms. Overall the
the next week will consist of a prototypical low amplitude, meridional
pattern with broad high pressure entrenched over the southern CONUS
pushing the upper level waves over the northern 48.

The first wave in this pattern will approach from the west late
Friday into Saturday, with a push of moisture upstream of the upper
trough. The moisture push will help induce weak low level diabatic
height depressions. The result will be broad lift in a buoyant warm
sector with scattered to numerous showers and thunderstorms across
the Mid-Mississippi Valley Friday night.

By the time this source of lift reaches central Indiana, diurnal
cooling will have capped much of the low level moisture. Still
showers and isolated thunderstorms will likely push through Saturday
morning. As solar heating increases in the late morning to early
afternoon, greater surface based instability may allow for a few
thunderstorm updrafts to intensify enough for strong to severe
gusts/hail. Some ensemble members are picking up on a slower
progression of this initial wave, of which would increase the severe
threat slightly by providing a more untouched and buoyant atmosphere.

Following this initial wave, a more potent source of lift along an
advancing cold front will work its way into the region. However,
There is still a lot of uncertainty on if there will be enough
instability for thunderstorms to initiate on the progressing
boundary. If thunderstorms do develop there will be a damaging wind
threat with a very dry low to mid level layer, leading to high DCAPE
values, but at this time this looks unlikely.

Sunday Through Thursday.

The aforementioned low amplitude meridional pattern will continue
through the the rest of the long term. Initally, the will lead to
cool, calm conditions with surface high pressure and upper level
troughing for Sunday and Monday. This should allow for generally
clear skies and highs around 80 along with the near surface flow
veering towards northerly to northwesterly.

The next phase of the this pattern will arrive mid week, with broad
ridging developing aloft. This will push highs back to around 90 by
Wednesday. Periodic rain chances will coincide with increasing
temperatures as weak low level waves pass through the region.
Thunderstorms will also be possible mid to late next week within
these wave passages.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 1215 PM EDT Fri Jun 28 2024

Impacts:

- VFR expected for much of the TAF period.
- Showers with isolated TSRA possible after 07Z.

Discussion:

Clouds over IL and MO will continue to increase and thicken this
afternoon, however cigs will remain VFR through most of the period.
Low pressure over NB is expected to advance northeast and push a
cold front across Central Indiana late tonight and early Saturday
morning. Forecast soundings suggest a nearly saturated column as the
front approaches and passes through Central Indiana. HRRR also shows
an area of showers passing with the approaching dynamics and cold
front overnight and early on Saturday. Thus confidence is high for
showers passing across Central Indiana late tonight and early on
Saturday, however confidence on specific timing and locations is
low. Thus will include a large window of VCSH late tonight. Have
used a tempo group on Saturday morning as the best forcing is
expected to pass.

Although a thunderstorm will be possible, the time of day and
limited instability are unfavorable for convection. For now have
left thunder out due to low confidence.

&&

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

$$

UPDATE...Puma
SHORT TERM...BRB
LONG TERM...Updike
AVIATION...Puma