IND issues Area Forecast Discussion (AFD) at Sep 20, 12:07 PM EDT309
FXUS63 KIND 201607
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
1207 PM EDT Sat Sep 20 2025
.KEY MESSAGES...
- Very warm temperatures again today
- Isolated to scattered showers and storms will be around today
through Sunday...with strong gusts possible in storms late Sunday
- Daily chances for showers and a few t-storms next week...while
higher humidity keeps overnights warmer, clouds bring milder days
&&
.FORECAST UPDATE...
Issued at 935 AM EDT Sat Sep 20 2025
Surface analysis late this morning shows a large and broad area of
high pressure over Ontario, extending its influence south and west
to include the east coast, the Ohio Valley and deep south. Low
pressure was found over the Dakotas and over OK. Looking aloft,
water vapor showed a negatively tilted trough from the northern
plains across IA to Indiana. The subsidence that has been persistent
across Central Indiana for quite some time is gone. An upper low at
near the bottom of the trough was found over NE IA. Water vapor
shows plenty of mid and upper level moisture over Indiana within the
trough. Dew points across the area remained high, in the upper 50s
and lower 60s.
Forecast soundings this afternoon suggest that convective
temperatures will be reached this afternoon while shallow
CAPE...values around 800 J/kg...will be available. HRRR suggests as
convective temps are reached by late afternoon, a weak wave pushing
around the trough will trigger some isolated to scattered showers
and storms. Areal coverage appears rather limited at this point, and
most locations will remain rain-free, but confidence is high for at
least a few scattered storms on Radar late this afternoon. Thus will
include 30-40 pops at many spots late this afternoon, but dry
weather will be expected until at least 3pm. Ongoing highs in the
middle to upper 80s appear on the mark.
&&
.SHORT TERM (Today and tonight)...
Issued at 257 AM EDT Sat Sep 20 2025
Central Indiana will remain under the increasing influence of an
upper trough throughout the short term period. Heights will fall
some today. At the surface, a weak front will remain northeast of
the area.
Impulses will bring forcing at times as they move through the upper
trough. These will interact with increasing moisture to produce some
isolated to scattered showers and storms through tonight.
Trends on satellite show that there will be some sunshine today with
breaks in the mid and high clouds. This will allow some instability
to build this afternoon, but it will be low enough that severe
storms are not expected. This instability be what allows the most
coverage of convection.
Tonight, 850mb winds increase some, which could add additional
forcing to the mix.
Uncertainty remains in the timing and strength of the upper
impulses, so confidence in the specific PoPs is lower than desired.
Given all of the above, will keep PoPs no higher than the chance
category. Will generally time the highest PoPs in the afternoon and
then again overnight as 850mb winds increase and moisture deepens.
The expected sunshine today will allow temperatures to peak in the
middle and upper 80s. Clouds and increasing moisture will keep
temperatures in the lower and middle 60s for lows tonight.
&&
.LONG TERM (Sunday through Friday)...
Issued at 257 AM EDT Sat Sep 20 2025
Sunday through Tuesday...
Broad and slowly-progressing troughiness will prevail over much of
the northern CONUS through the early week...with somewhat-organized
group of weaker short waves circulating around the southern side of
a parent axis near Duluth...from the central Plains to the Midwest.
Despite overall unimpressive gradients...central Indiana's proximity
on the southeast quadrant of the wide region of lower heights...will
promote moderate SSW breezes that will slowly increase deep moisture
into the mid-week.
Occasional scattered to at times numerous rain showers should be the
rule...with greatest rain chances in the late Sunday night through
Monday night timeframe...when a linear vort aligned parallel to the
moisture advection slowly pushes east through the region. Mainly
isolated thunder will be favored during PM hours when modest daytime
heating assists convection. Diurnal ranges of 15 degrees or less
are expected between considerable daytime cloudiness and warmer
overnights amid unseasonably high dewpoints near the 65-70F range.
Wednesday and Friday...
Recent model trends are increasing rain chances into the late
week...with the potential for the retracted northern jet to
facilitate two vorts dumbbelling around each other in a broad cut-
off H500 trough centered near the Quad Cities area. While lower
confidence still surrounds the details of this set-up...there is a
good chance the local region stays on the more humid/showery
southeast side of any such cut-off...while positioned close enough
to the spinning vorts to continue chances of at least scattered
showers. Expect occasional isolated thunder chances, with overall
lower chances for storms than the first half of the long term.
Highs in the 70s are most likely. Lower certainty for overnight
lows, dependent on if the humid Gulf fetch is maintained, or if the
cooler cut-off core spins over the region...with this downward trend
in morning minimums to near normal levels more likely towards the
end of the long term.
Low confidence in total rainfall amounts for this upcoming week,
given all of the pattern's moving synoptic parts, and what should be
several, if not numerous rounds of showers. Certainly the potential
for widespread 1.00-2.00 inch totals is present, yet amounts will be
refined as this much-needed rainy forecast is updated into next week.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 1207 PM EDT Sat Sep 20 2025
Impacts:
- Mainly VFR Conditions
- Showers and isolated thunderstorms will be possible 21Z-09Z.
Discussion:
An upper level trough arriving over the area along with forecast
soundings indicating shallow CAPE available this afternoon and
evening will allow for shower developing later today. HRRR shows
scattered shower and storm development this afternoon as convective
temperatures are reached.
As heating is lost this evening broad lift continues and HRRR
suggests continued sct-isolated coverage, but confidence for this is
low for the moment.
Overall will use VCSH groups to cover the best windows for potential
rainfall. Will not mention thunder for the moment due to low
confidence on coverage and timing, rather using updates to address
this when confidence is high.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Puma
SHORT TERM...50
LONG TERM...AGM
AVIATION...Puma
Source:
IND issues Area Forecast Discussion (AFD) at Sep 20, 12:07 PM EDT---------------
If I'm using your data in a way that is against your terms please email the team at "threatweb@pupswoof117.com"! I am a bot who will not respond in the comments at all and is only designed to post RSS feeds!
