019 FXUS63 KIND 082255 AFDINDArea Forecast Discussion National Weather Service Indianapolis IN 655 PM EDT Wed Oct 8 2025
.KEY MESSAGES...
- FROST ADVISORY tonight across our northern counties.
- Patchy frost Tonight and Thursday nights with lows in the mid to upper 30s.
- Dry weather is expected through at least Tuesday, with gradually warming temperatures.
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.SHORT TERM (This evening through Thursday)... Issued at 303 PM EDT Wed Oct 8 2025
Large-scale upper-level troughing and strong surface high pressure will bring some of the coolest nights of the season so far. Surface analysis shows northerly flow and cold air advection today associated with the advancing 1032mb high. Continued cold air advection is expected as we head into tonight.
By sunset, the surface high center should be located roughly over Michigan. Since the high is still a bit to our north, we`ll have a northerly breeze through the night. Therefore, radiational cooling potential may not be fully realized. Still, cold air advection is strong enough and the winds light enough to allow for lows in the mid to upper 30s across our north. Slightly warmer values will be found elsewhere with lows in the upper 30s to low 40s. Some wind- sheltered areas may see some patchy frost tonight. We`ve added frost to the forecast across our northern tier counties from Lafayette to Kokomo to Muncie. Given that it may be the first frost of the season for many of these places, a Frost Advisory will be issued with this forecast update.
As for highs, full sun, dry air, and relatively light winds will allow for a large diurnal spread. Temperatures may tend towards the higher end of guidance and dew points may end up near the bottom. We`ll add more weight to high-res guidance and MOS for temperatures throughout the forecast period. Expect highs in the upper 60s to near 70 on Thursday.
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.LONG TERM (Thursday night through Wednesday)... Issued at 303 PM EDT Wed Oct 8 2025
Continental air masses with good radiative conditions this time of year often have a high temperature bias in models. For low temperatures Thursday night, we used 10th percentile blended guidance to account for this, and also nudged toward NAM 3-km for better terrain representation. Strong subsidence and shallow inversion in model soundings is a classic dew/frost setup, with supportive temperature for frost across roughly the northern half. A few outlying areas could reach freezing. Urban areas are less at risk for frost and for now will not include frost for the core of Indianapolis. One caveat may be cirrus preceding an upstream midlevel wave, but current timing appears to have minimal impact to the radiative cooling process other than perhaps slowing it slightly toward sunrise.
Weak thermal ridging preceding the upstream shortwave trough will bring our temperatures back to around normal Friday. There has been a trend of this wave closing/deepening over the Great Lakes Friday a little more substantially than earlier model cycles, and then drifting south before dampening. This may nudge a cooler air mass a little deeper into Indiana this weekend which could slightly counter what would otherwise be an overall warming trend. This may be especially true if post-frontal stratus is extensive. There may be enough ascent and midlevel moisture for low coverage / low QPF showers, late Friday into Saturday depending on the behavior of the aforementioned midlevel wave. At this time, probabilities of measurable rainfall amounts are 031- 035-038>042.
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SHORT TERM...Eckhoff LONG TERM...BRB AVIATION...50
NWS IND Office Area Forecast Discussion