621
FXUS63 KIWX 041426
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
926 AM EST Tue Nov 4 2025

.KEY MESSAGES...

- Very low humidity is expected this afternoon and anyone
  planning burns should exercise caution.

- The next chance of light rain arrives early Friday.

- Much colder temperatures are expected early next week and snow
  is possible but it is far too early to pin down exact amounts
  or locations.

&&

.UPDATE...
Issued at 921 AM EST Tue Nov 4 2025

Fire weather concern is still the primary near term forecast
issue today. Morning RAOB from KILX indicates some impressive
dry low level air, with 925 mb dew points near -10 deg C. Based
on this observational data, the potential does seem to be in
place for dew points to drop into the mid/upper teens in some
locations. This could produce some localized minimum afternoon
relative humidities in the 15 to 20 percent range. Still some
uncertainty in magnitude of low level mixing today, but will
continue to monitor trends for possibility of SPS elevated fire
weather risk this afternoon. Wind speed magnitudes should be
limited to the 10 to 15 mph range which should hopefully prevent
a higher end fire weather concern from taking shape.

&&

.DISCUSSION...
Issued at 338 AM EST Tue Nov 4 2025

Fire wx is the main concern again today as very dry airmass has
settled into the area with surface dewpoints in the low/mid 20s
south and around 30F north. Winds are switching around to the
southwest but this will provide little relief during the day given
modest mixing to around 850mb (limited somewhat by increasing
mid/upper level clouds). Anticipate low 20s dewpoints everywhere by
the afternoon which leads to RH values around 25 percent given highs
around 60F. Luckily wind speeds are much lighter today (sustained
only around 10 mph) which will limit the fire wx threat. However,
anyone planning to burn leaves (or anything) today should still
exercise caution in light of the recent dry conditions.

The next jet streak and attendant midlevel wave dives into the Great
Lakes early Wed. With a track very similar to Monday`s system, our
area remains in the unfavorable right exit region. Best CVA and
upper jet dynamics will bypass us to the N/NE. Held onto some NBM
slight chance PoP`s north as (similar to Monday) can`t rule out some
brief sprinkles in the north but overall no impact. SW winds ahead
of the system get a bit breezy tonight and lows will only be in the
mid/upper 40s as a result. After a breezy and warm day on Wed with
highs in the mid 60s south, CAA drops lows back into the low 30s for
Wed night. The seesaw pattern starts over again on Thu with
increasing southerly winds/WAA pushing highs back to near 60F and
lows Thu night only in the 40s.

We finally get a more favorable track for the next trough slated to
arrive early Fri. This trough dives much further south and is able
to capitalize on some better (though still not great) low level
moisture/instability. Some isolated thunderstorms are possible but
certainly no severe threat. Even rainfall amounts will likely be
limited to around a quarter inch given quick-moving nature of this
system. Still, it is better than nothing given ongoing extreme
drought in our SE.

Another system is then expected on Sat night and this one could mark
the arrival of the first truly cold air of the season. While
deterministic runs show general agreement, ensemble guidance still
shows a fair amount of spread, particularly in subtle but important
differences heading into Sun/Mon. At this point, bulk of the
synoptic precip Sat night is expected to be rain, though some snow
can`t be ruled out in heavier rates across the north if the more
southern track verifies. Cold air doesn`t really arrive until late
Sun into Mon. This is when lake effect snow is likely to some degree
but exact locations and amounts will depend on subtle variations in
flow trajectories and instability profiles that are impossible to
resolve six days out. Suffice it to say, any raw model snowfall maps
should be met with a high degree of skepticism at this time
range.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 614 AM EST Tue Nov 4 2025

Surface winds will be relatively light at the start of the TAF
period; however, stronger low level winds will eventually mix
down and cause surface winds to increase and become gusty. Low
level wind shear will develop as momentum transfers down toward
the ground. For this reason, have included wind shear late in
the TAF period at both terminals. Otherwise, VFR conditions will
prevail.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 8 PM this evening to 4 AM EST
     Thursday for LMZ043-046.

&&

$$

UPDATE...Marsili
DISCUSSION...AGD
AVIATION...Marsili