Knox, Indiana Weather Forecast Discussion

108
FXUS63 KIWX 162339
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
739 PM EDT Tue Sep 16 2025
.KEY MESSAGES...
- Remaining warm and dry through Friday with highs in the mid to
  upper 80s.
- Rain shower chances (20-40%) arrive this weekend into early
  next week.
&&
.DISCUSSION...
Issued at 205 PM EDT Tue Sep 16 2025
Expansive upper level ridge to gradually shrink overhead through the
remainder of the week as northern stream shortwave energy through
Ontario/Quebec eventually absorbs a Mid-Atlantic closed low up the
East Coast. The dry and stable column under this upper ridge will
continue to ensure more warm and dry weather locally through Friday.
Some weak moisture flux off Lake Erie in weak easterly flow may once
again support patchy fog/stratus formation toward daybreak along and
east of the Ohio border early Wednesday morning.
The ridge breaks down this weekend into early next week as an upper
trough approaches from the Central US and moisture attempts to
stream northward pre-frontal. This will bring periodic/low
shower chances (20-40%), and non-zero chances for an isolated
storm, back into the fold during this time, with mean ensemble
solutions favoring Sunday into Monday for slightly better rain
prospects (mainly light).
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 738 PM EDT Tue Sep 16 2025
Even though heights are falling, plenty of ridging in between a
trough in the Rockies and another along the Mid Atlantic, allows for
continued dry weather. Prevailing VFR conditions should be had for
the bulk of the period aside from late night/early morning when fog
is possible. Cross-over temps just barely touch, but evening dew
points have been running a little wetter than forecast and NAM FWA
soundings indicate a good inversion forms which may be able to trap
enough moisture for fog. Light east winds today may have been able
to transport marine air inland, but the question is will it be able
to make it far enough westward to FWA. SREF probabilities of less
than 1 mi visibility indicate some chance and aviation visibility
guidance also supports visibility obstructions at that time. Will
just use a tempo group of 2 miles between 11 and 13z there for now.
Cannot rule out some patchy ground fog at SBN, but it`s not enough
to put it in there at this point.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Steinwedel
AVIATION...Roller

NWS IWX Office Area Forecast Discussion