IND issues Area Forecast Discussion (AFD) at Aug 25, 2:20 PM EDT
599
FXUS63 KIND 251820
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
220 PM EDT Mon Aug 25 2025
.KEY MESSAGES...
- Below normal temperatures, low humidity, and dry conditions
persist for at least the next week
- Record low temperatures in the mid to upepr 40s Tuesday and
Wednesday morning
&&
.SHORT TERM (This evening through Tuesday)...
Issued at 220 PM EDT Mon Aug 25 2025
Surface analysis early this afternoon shows strong high pressure
through the Missouri River Valley, with a surface ridge axis nosing
southeast across KY and TN. This strong high pressure system was
dominating the weather across the region. GOES16 shows a large CU
field across Central Indiana, resulting in partly to mostly cloudy
skies. Aloft, water vapor imagery shows a deep upper low over Hudson
Bay and sharp ridging over the western CONUS. This was resulting in
NW flow across Central Indiana, along with subsidence. Dew point
temperatures had fallen to the comfortable upper 40s due to
mixing and subsidence.
Tonight...
The strong surface high to west is expected to build across Central
Indiana overnight as subsidence continues. Forecast soundings show a
dry column through the night. As typically expected, diurnal CU will
be lost as daytime heating diminishes, leading to clear skies across
Central Indiana Overnight.
850mb temps are expected to fall to around 5-6C, leading to some of
the coldest low temperatures in Central Indiana since June. The
record low in Indianapolis on Tuesday is 48. Although Indy should
remain slightly warmer than that due to urban heat island effects,
upper 40s will certainly be found in more rural locations.
Tuesday...
Models suggest the strong cyclone aloft over Hudson Bay will push a
short wave across Central Indiana during the course of the
afternoon. However very dry air within the lower levels along with
continued dominance of the surface high pressure system will result
in only a few passing clouds. Once again, forecast soundings show
mainly a dry column through the afternoon as the wave passes. CU
development is once again expected as the soundings show afternoon
saturation near 6KFT. Thus after a sunny morning, pleasant partly
cloudy skies and low humidity will continue. Given the cool 850mb
temps highs should only reach the upper 60s and lower 70s.
&&
.LONG TERM (Tuesday night through Monday)...
Issued at 220 PM EDT Mon Aug 25 2025
Little to no change made to the long term forecast as high pressure
remains the dominant influence over the region for at least the next
week. Continued below normal temperatures and mainly dry conditions
persist into Labor Day weekend with little to no chances for rain
until early September. Although a couple of weak shortwaves passing
through the area may temporarily enhance cloud cover and perhaps
produce a sprinkle or two, abnormally dry conditions (D0) will
likely spread across much of Central Indiana.
Wednesday and Thursday...
The period begins on a cold note for all of Central Indiana as high
pressure overhead leads to optimal conditions for radiational
cooling Wednesday morning. Low to mid level temperature anomalies
will still be well below normal for this time of year. This combined
with radiational cooling is a prime set up for record lows across
the region. Record low temperatures for this time of year generally
range from the mid 40s to mid 50s. With most locations across
Central Indiana forecast to reach the 40s Wednesday morning, would
not be surprised to have many daily records tied or broken. Coolest
locations dropping into the mid 40s will be across North Central
Indiana and in low lying areas.
While upper troughing remains in place across the Great Lakes
region, surface high pressure shifting south and east of Indiana
briefly switches surface flow around to the south midweek resulting
in a slight warming trend after such a cold start on Wednesday.
Another weak shortwave within the upper flow and associated surface
front become rather diffuse as they sag southward into Indiana on
Thursday. The main energy, lift, and moisture should remain across
northern Indiana and the Great Lakes, while dry antecedent
conditions largely inhibit measurable precipitation locally. The
only impacts from this incoming front will be brief periods of
southerly flow, increasing clouds, and temperatures moderating by a
few degrees. Overall, dry conditions and relatively below normal
temperatures are still expected to persist.
Some patchy radiation fog, perhaps even dense in a few
climatologically favored spots, cannot be ruled out entirely Tuesday
and Wednesday nights as the core of strong high pressure moves
overhead and excellent radiational cooling conditions are present
with mostly clear skies and light winds.
Friday through Labor Day Weekend...
Behind the aforementioned front on Thursday, high pressure becomes
centered over the Great Lakes region once again, keeping conditions
dry and surface flow out of the northeast. While below normal
temperatures are still forecast in the extended range, a slight
warming trends is expected into labor day weekend as the core of
colder air shifts north and east. High temperatures in the mid to
upper 70s expected for Labor Day weekend with the 80 degree mark
possibly creeping into far southern portions of Central Indiana.
High confidence in a dry forecast exists through Sunday, but
uncertainties increase beyond Labor Day as a more active pattern may
return to the region. Long range guidance typically struggles with
these types of synoptic pattern changes, often bringing in
precipitation too quickly and underdoing the amount of dry air in
place. Guidance has pushed back the first day of potential
measurable rainfall with each run over the last week. At the moment,
guidance shows an area of low pressure developing to the west for
the first week of September, but it is too soon to dive into any
further details with such high run to run inconsistencies. For now,
keeping the forecast relatively dry for Labor Day, but expect
forecast updates each day as details become clearer on the evolution
of the large scale pattern change for the eastern half of the CONUS
going into early September.
&&
.AVIATION (18Z TAF Issuance)...
Issued at 1149 AM EDT Mon Aug 25 2025
Impacts:
- VFR Conditions this TAF period
Discussion:
High pressure at the surface and strong subsidence aloft will lead
to continued VFR conditions this TAF period. Diurnal CU is expected
this afternoon and again on Tuesday afternoon, creating BKN VFR
cigs. Skies will be mostly clear at night as heating is lost and
subsidence reigns with good visibility and light winds.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Puma
LONG TERM...CM
AVIATION...Puma
Source: IND issues Area Forecast Discussion (AFD) at Aug 25, 2:20 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202508251820-KIND-FXUS63-AFDIND)
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