365 FXUS63 KIND 090731 AFDINDArea Forecast Discussion National Weather Service Indianapolis IN 331 AM EDT Tue Sep 9 2025
.KEY MESSAGES...
- Gradually climbing temperatures through the week with near 90 degree highs by Saturday
- Dry weather outside of low rain chances this weekend may lead to continued expansion of drought conditions into next week
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.SHORT TERM (Today and tonight)... Issued at 255 AM EDT Tue Sep 9 2025
Surface high pressure remains near the region providing continued quiet weather conditions. The center of the surface high pressure will be over New England today, shifting northeast throughout the short term period. This will allow for winds to become more southeasterly and thus begin the trend of warming temperatures expected later in the week. The light southeasterly flow and plentiful sunshine should warm temperatures well into the upper 70s today with some locations potentially reaching or exceeding the 80F mark.
Forecast soundings show deep mixing into a dry airmass aloft which will result in low RH values during the afternoon. Fire concerns remain low due to light winds. A subtle upper wave is expected to approach central Indiana late in the day and into tonight. While the airmass will be much too dry for precipitation, some increase in mid- high clouds can be expected as well as dew points increasing by a few degrees. Model soundings also show the column becoming less dry as the wave approaches.
Expect temperatures to quickly fall after sunset due to a decently favorable setup for radiational cooling, although not quite as efficient as the previous few nights. Look for lows generally in the low 50s tonight.
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.LONG TERM (Wednesday through Monday)... Issued at 255 AM EDT Tue Sep 9 2025
Wednesday Through Friday.
The gradual warming trend will continue into Wednesday with broad high pressure across the Ohio Valley persisting and weak to no flow near the surface and aloft. Model soundings show near saturation at the top of the boundary layer Wednesday afternoon which should allow for a sparse diurnal cu field. Weak flow at the top of the boundary layer will limit the mixing out of surface moisture but like previous days, expect min RH values to drop into the 25 to 35 percent range. Afternoon highs should top out in the low to mid 80s Wednesday. Near identical conditions ere expected for Thursday with slightly lower RH values Friday due to the warmer highs which may approach 90 degrees in the west. Concerns continue for slightly elevated fire weather danger with details covered in the fire section at the bottom.
Saturday Through Monday.
Forecast confidence is low this weekend into next week with a wide model spread on the synoptic pattern. The broader pattern has a building ridge across the Central US with the potential for ridge- riding complexes of storms for the weekend, but exact details remain highly uncertain. While there will be some moisture return into the Ohio Valley by Saturday, instability values will be fairly meager, but a strengthening jet across the Upper Midwest will increase shear and create a favorable environment for thunderstorm organization. At this point, confidence is fairly high in at least some thunderstorms across the Great Lakes region, but confidence is low that any reach as far south as central Indiana.
Forecast confidence continues to decrease Sunday into Monday with a wide range of model solutions in how they handle both the ongoing ridge and a deepening upper level low across southern Canada. Currently leaning towards a more persistent pattern with the upper level ridge helping to push the aforementioned low pressure further east into the Northeastern states, but will have to continue to monitor forecast trends. With ensemble output keeping chances of QPF greater than 0.01" at less than 30 percent over the next 7 days, expect to see further expansion in drought conditions and exacerbating fire weather concerns going into the second half of the month.
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.AVIATION (06Z TAF Issuance)... Issued at 130 AM EDT Tue Sep 9 2025
Impacts:
- None.
Discussion:
VFR conditions are expected through the TAF period.
Some cirrus will pass through at times, and perhaps a few cumulus may pop during the afternoon. Winds will be light and variable into the morning and calm at times, but with generally easterly direction. Winds will shift to the southeast 10kt or less by Tuesday midmorning and persisting through much of the day. Dry air should keep any fog at bay overnight.
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.FIRE WEATHER... Issued at 331 AM EDT Tue Sep 9 2025
The lack of any significant rainfall over the last several weeks has resulted in abnormally dry and minor drought conditions to develop across Indiana. With little to no rain in the forecast for the next 7 days, confidence is increasing in an elevated fire weather threat each afternoon as daily min RH values fall into the 20% range. Lowered afternoon dew points each day through next Saturday to the NBM10th percentile to account for such dry conditions and afternoon mixing bringing down even drier air to the surface. The one factor keeping the fire weather threat lower is the lack of wind. Despite deep mixing, very weak low level flow should keep winds under 10 kts through the period. It is worth noting that CPC has placed the majority of the Midwest and Mid Mississippi Valley in a slight risk for extreme heat for Sept 15-18th. If no appreciable rainfall is observed this weekend, the fire weather threat may continue to increase and persist into mid month. Will continue to monitor the extended forecast for increasing fire weather concerns.
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.IND WATCHES/WARNINGS/ADVISORIES... None. &&
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SHORT TERM...KF LONG TERM...White AVIATION...KF FIRE WEATHER...White
NWS IND Office Area Forecast Discussion