Pierceton, Indiana Weather Forecast Discussion

006
FXUS63 KIWX 051543
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1143 AM EDT Sun Oct 5 2025
.KEY MESSAGES...
- Warm, dry, and breezy conditions will lead to an elevated fire
  danger today.
- Rain is expected Monday night through late Tuesday with
  amounts up to a half-inch possible.
- Much cooler weather returns for the middle of the week with
  lows dipping into the upper 30s.
&&
.UPDATE...
Issued at 1135 AM EDT Sun Oct 5 2025
Fire weather concerns continue to be the near term forecast
issue. Previous forecast remains in good shape with previous
SPS messaging still valid for the remainder of the afternoon.
The combination of diurnal mixing and northward advection of
slightly drier low level air from the Ohio Valley should result
in downward dew point trend over the next few hours. The 12Z
morning RAOB from KILN indicates a continued downward trend of
925mb dew points (+8 deg C). Mixing upstream low level airmass
to the surface would still seem to support minimum afternoon dew
points in the upper 40s to lower 50s, with perhaps slightly
lower dew points across far northeast IN/northwest Ohio where
near sfc soil moisture is at a minimum. The combination of RH`s
from 25 to 35 percent (locally 20 percent possible) and gusty
southwest winds to 15-20 mph (highest gusts to 25 mph across the
northwest) will lead to elevated fire danger this afternoon
with a potential of the spread of field fires. This still
appears to be a short-term threat for this afternoon as low
level moisture advection will overspread the region from south
to north tonight into Monday.
&&
.DISCUSSION...
Issued at 245 AM EDT Sun Oct 5 2025
Elevated fire danger continues to be the primary concern in today`s
forecast. Upper low previously over the Southwest CONUS is now
rapidly lifting toward Ontario with an associated 995mb surface low
and trailing cold front. This cold front will take considerable time
to reach our area given highly meridional flow and parent forcing on
a fast track to the Arctic. However, the important result locally
will be a tightening of low level gradient as 1027mb surface high
remains anchored over the Mid-Atlantic. Boundary layer flow of around
20 kts still anticipated, supporting gusts of 20-25mph at the
surface. Thermal profiles and mixing heights are a touch lower than
yesterday so highs will be a degree or two cooler. However, the
overall profile is also drier as minor theta-e plume evidenced by
yesterday`s robust cu field exits the region. Today will feature
more sun and lower dewpoints. Some upper 40s dewpoints are possible
today, particularly in drought-stricken portions of our E/SE,
yielding RH values right around 25 percent. This in combination
with the wind and recent dry conditions raises concern for fires
to spread quickly, especially field fires with harvest
activities in full swing. Red flag warning criteria requires
sustained winds of at least 20 mph with RH at or below 25
percent for 3 hours, along with 10-hour fuel moisture 8% or
less. We will likely not hit the wind or 10-hour fuel criteria
and even the RH criteria will be tough. Also, the areas with the
strongest winds (NW) are the areas least impacted by the recent
dry spell. However, historically this is a common pattern for
the development and rapid spread of field fires during harvest
season. Will therefore issue an SPS and continue to highlight
the threat in the HWO and social media messaging.
Low level moisture advection finally begins in earnest on Monday as
cold front slowly approaches. More cloud cover and less mixing is
expected, yielding another degree or two drop in highs and an
increase in afternoon dewpoints/RH values. Fire weather is not
expected to be a significant concern on Monday. Still suspect most
of the day will be dry as surface cold front doesn`t arrive until
almost 06Z. However, a few showers will be possible in the 21-00Z
timeframe, particularly in our far NW. Rain chances continue into
late Tue as elevated portions of the front slowly pass with a
secondary shortwave crossing late Tue. There`s still some concern of
a mismatch between better jet dynamics/fgen forcing just to our
north and better moisture/instability to our south. Nocturnal
passage of the surface front doesn`t help our rain chances either.
However, models in reasonable agreement there will be at least
numerous showers around and have therefore maintained high PoP`s
with QPF amounts generally 0.25-0.5 inches (higher far SE).
This won`t put a significant dent in the drought but helpful
nonetheless. A few embedded thunderstorms are possible at times
but overall instability is very meager and severe storms are not
expected.
Sharp cool-down still expected midweek with lows touching the 30s
Wed night. Doesn`t look quite cold enough for a significant frost
threat but there is still some spread in the guidance so will keep
an eye on it. Forecast confidence drops significantly heading into
next weekend as models continue to show wide variations in overall
pattern.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 645 AM EDT Sun Oct 5 2025
Strong ridge will remain over the region today with very
dry/stable profile yielding mostly clear skies. Increasing
gradient will result in SSW gusts of 20-25 kts during the
afternoon.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
UPDATE...Marsili
DISCUSSION...AGD
AVIATION...AGD

NWS IWX Office Area Forecast Discussion