IND issues Area Forecast Discussion (AFD) at Aug 5, 1:33 AM EDT
857
FXUS63 KIND 050533
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
133 AM EDT Tue Aug 5 2025
.KEY MESSAGES...
- Showers and storms producing localized flooding will continue to
be focused across southwestern portions of central Indiana for
the next few hours.
- Daily chances for showers and storms continues through Wednesday
then decrease for the second half of this week
- Progressively warmer and more humid conditions by mid to late week
continuing into the weekend
&&
.FORECAST UPDATE...
Issued at 953 PM EDT Mon Aug 4 2025
A concentrated area of showers and thunderstorms driven by a
persistent MCV over western portions of central Indiana will
gradually encounter a more hostile airmass for thunderstorm activity
overnight with showers becoming the predominant precip by 06z. Have
kept pops in the 60-80 percent range for the next few hours for
areas south of I-70 and west of I-65. In this region, areas of heavy
rain and the potential for additional flooding will continue for at
least another several hours.
There have been some minor /1-2 feet/ rises on area creeks and
streams where the heaviest rain has fallen in SW portions of
central Indiana, but as of this discussion flooding has been
confined to low lying/poorly drained areas and some roadways.
With the weakening trend in convection overnight, introduced a
gradual reduction in the pops to 20-40 percent by 06z. Have also
introduced patchy fog towards daybreak across much of south/western
portions of the forecast area the area once mid-high cloud cover
diminishes and as dewpoint depressions fall to at or below 2 deg F.
&&
.MESOSCALE UPDATE...
Issued at 515 PM EDT Mon Aug 4 2025
Surface analysis shows an inverted trough extending along the MS
valley with a low pressure area centered near the OH/MS river
confluence region. Vis and IR satellite imagery indicates presence
of continued cooling cloud tops and the development of an small MCS
with increasing deep moisture/mass convergence the last couple of
hours. PWAT values are on the order of 1.7-1.8 inches in this
region.
Given slow storm motions, moist airmass and ample instability (SBCAPE
1500-2000 j/kg) expectation is that convection and heavy rain threat
will persist for several more hours across western portions of the
forecast area, especially Knox, Daviess and Sullivan counties. The
MCV and attendant heavy rain threat will attempt to push slowly
eastward into a progressively more stable regime over Central
portions of the forecast area thanks to a strengthening cold
pool/mesohigh over IL. However, this combined with a gradual
diminishing instability after 00Z should allow for weakening threat
for thunderstorms and heavy rain in the 00-02Z period.
&&
.SHORT TERM (This Evening through Tuesday)...
Issued at 234 PM EDT Mon Aug 4 2025
Convection continues to move across portions of the lower Wabash
Valley this afternoon on the eastern flank of a near stagnant
inverted surface trough. Storms have been sluggish in their movement
and have seen some gauge reports in excess of 3 inches over parts of
Vigo County to the southeast of KHUF since midday. Localized
flooding remains a concern here in the short term and across much of
the far southwest part of the forecast area with convection
regenerating and moving N/NW. 18Z temperatures were in the mid 70s
to low 80s over all but in the vicinity of KHUF where the heavier
rain has kept temps closer to 70.
The inverted surface trough extending from the lower Wabash Valley
southwest into the lower Mississippi Valley will remain a prominent
feature into Tuesday as it slowly weakens over the region. A weak
trough aloft will extend into the Ohio Valley as well over the next
24 hours...and both of these features will contribute to a threat
for isolated to scattered convection over the entire
forecast area extending into Tuesday.
For the rest of the afternoon...convection is expected to remain
confined to areas south and west of I-74 with a focus across the
lower Wabash Valley between KHUF and Vincennes where current
mesoanalysis shows a bullseye of deeper moisture pooling along the
eastern flank of the trough. PWATs have risen to 1.6 to 1.7 inches
supporting the threat for higher rainfall rates likely to continue
over the next several hours in this zone. Convection also is not
moving fast which is enabling heavier rainfall in short periods as
additional showers generate and train over the same spots.
Convection should decrease in coverage this evening.
Low level moisture drops off quickly northeast across the forecast
area with residual dry air from high pressure to the northeast
continuing to impinge on further expansion of showers into more of
the forecast area. This should continue into the early evening but
moisture advection will gradually expand northward tonight with the
potential for isolated showers and thunderstorms spreading across
the remainder of the forecast area as a result.
Even as the inverted trough weakens Tuesday...low level moisture and
CAPE values rising to around 1500-2000 J/KG will be enough to
generate another round of isolated to scattered convection focused
especially during the afternoon at peak heating. Heavy downpours and
localized flooding from slow moving storms will remain the primary
threat.
Temps...with the continued influx of low level moisture...lows
tonight will hold in the low to mid 60s. There should be less in the
way of cloud coverage on Tuesday outside of convection which should
aid in highs slightly warmer than today in the mid 80s for most.
&&
.LONG TERM (Tuesday Night through Monday)...
Issued at 234 PM EDT Mon Aug 4 2025
Strong ridging aloft will remain anchored over the southern Rockies
and High Plains while a weakness in the flow lingers downstream
across the eastern Midwest and Ohio Valley through midweek. Isolated
to scattered afternoon and evening convection will persist on
Wednesday across the region but as the weakness diminishes and
ridging expands east late week...convective chances will decrease
into the weekend along with an increase in heat and humidity.
A more focused and widespread threat for convection will arrive by
the end of the weekend and into early next week in response to an
approaching cold front dropping out of the upper Midwest and
becoming nearly stationary over the region.
Tuesday Night and Wednesday
A weak but persistent level of troughiness aloft on the lee side of
the ridge will remain across the Ohio Valley through Wednesday
gradually shifting eastward. This will maintain isolated to
scattered convection across especially the southeast half of the
forecast area into Wednesday with a continued risk for slow moving
localized downpours that generally remain subsevere during peak
heating. However any stronger cell with a collapsing downdraft will
carry a localized gusty wind threat.
Highs will climb into the mid 80s Wednesday with humidity levels
slowly ticking up as well as progressively deeper moisture advects
into the region.
Wednesday Night through Monday
Heights aloft will respond to an expansion of the ridging to our
west late this week into the weekend resulting in a resumption of
the late July hot and humid regime albeit with temperatures and
humidity levels not quite as high as experienced last week. Highs
will rise into the upper 80s and lower 90s Friday through Sunday
with dewpoints near or above 70 degrees which could bring peak heat
indices into the upper 90s over the weekend.
The presence of deep low level moisture and ample instability will
keep the risk for isolated afternoon and evening convection in play
but overall daily coverage will decrease with the development of a
mid level cap and the loss of forcing aloft. By late weekend into
early next week...a cold front will shift south towards the region.
While this would provide increased forcing aloft for more widespread
and robust convection... there remain hints in the long range
guidance at the front becoming nearly stationary to our north across
the lower Great Lakes through much of next week as it runs into the
ridging further south. This would keep a warm...humid and unsettled
pattern across the Ohio Valley with any substantial cooldown coming
from a frontal passage being delayed until late next week at the
earliest.
&&
.AVIATION (06Z TAF Issuance)...
Issued at 133 AM EDT Tue Aug 5 2025
Impacts:
- Patchy fog possible this morning at KBMG and KHUF
- Another round of showers with isolated thunderstorms after 18Z.
Discussion:
Rain and thunderstorms are diminishing from HUF to BMG, but
beginning to increase at IND. Thunder hasn't been reported, and
based on radar trends we will keep the mention of thunder out of the
IND TAF through morning. Overall, expect rain showers to diminish in
coverage with time, but remain present to some extent through at
least 12z.
Renewed shower and thunderstorm activity is possible at all
terminals this afternoon as instability increases. Precipitation
should be scattered in nature with less coverage than yesterday.
Maintained PROB30s for showers starting after 20Z. Uncertainly in
coverage and longevity precludes longer duration at this time.
Fog is possible at times this morning and again tonight, especially
in areas that see rainfall followed by clearing.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Crosbie
SHORT TERM...Ryan
LONG TERM...Ryan
AVIATION...Eckhoff
Source: IND issues Area Forecast Discussion (AFD) at Aug 5, 1:33 AM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202508050533-KIND-FXUS63-AFDIND)
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