Terre Haute, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

660
FXUS63 KLOT 020736
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
236 AM CDT Wed Jul 2 2025

.KEY MESSAGES...

- Small chance (15-20%) for a gusty thunderstorm or two late
  this afternoon/early evening.

- Isolated to widely scattered storms possible Thursday with a
  gusty downburst threat.

- Hot July 4th and Saturday but not as oppressively humid as the
  previous rounds of heat recently (~95-100F heat indices).

- More appreciable thunderstorm chances return Saturday night
  and Sunday with a slowly approaching cold front. There may be
  a few days of quieter weather to start next work week.

&&

.DISCUSSION...
Issued at 236 AM CDT Wed Jul 2 2025

Through Thursday Night:

A surface high will build and expand off to our south and west
today and will commensurately push some warmer 925-850 mb
temperatures into the region today. Expect highs to generally be
about 2 to 5 degrees warmer than yesterday as a result. While
surface dewpoints have settled in the low 60s early this
morning, deep mixing will promote a fairly expansive diurnal
cumulus field later this morning and afternoon. Forecast
soundings suggest that, at least through early to mid afternoon,
Cu should remain fairly limited in vertical extent, with a zone
of warmer 700-600 mb air generally resulting in some degree of
capping amidst limited (conditional) instability. A few
sprinkles can`t be ruled out, but measurable precipitation
chances appear to be under 20 percent.

The upper levels will actually be quite active today with a
series of shortwave troughs and associated vorticity maxima
pushing through seasonably fast northwest flow aloft. One such
vort max is slated to arrive late this afternoon and into the
early evening, and as this occurs, there is some potential that
lingering capping erodes sufficiently (due to cooling 700-600 mb
temperatures) to allow for the development of an isolated
shower/storm. Any coverage still looks quite low though (capped
PoPs around 15-20%), with better coverage relegated north of the
IL/WI state line within the cooler mid-upper level airmass.
Should more developed clusters manage to develop and sustain
across central and southern Wisconsin late in the day, some
additional gusty outflow-driven winds/storms could manage to
sneak into our north/northeast through early evening prior to
the loss of (limited) diurnal instability, but again any
coverage here seems like it`d stay pretty low.

Forecast for tonight remains dry, but watching a mid-level moist
axis and region of ACCAS and ongoing storms within a zone of
steepened lapse rates currently pushing out of eastern South
Dakota. This is tied to a region of increased low-level
WAA/isentropic ascent which is forecast to move towards and
east of the Mississippi River late this evening and overnight.
The signal for this resulting in elevated convection across our
west late tonight was a bit too low to justify the addition of a
precip mention, but will be something to keep an eye on.

Boundary layer moisture is forecast to build a bit into
Thursday, with increasing thicknesses again adding a degree or
three to high temperatures. This deeper moisture, along with
modestly steeper mid-level lapse rates will result in a bit
more instability and less capping compared to today. Forcing
mechanisms look a bit more nebulous though, which supports
holding PoPs in the 20-30 percent range at this time. Deep
layer shear through the typical 5-6 km/lower half storm depth
appear pretty low, under about 25 knots suggesting
pulse/loosely-organized multicell clusters would be the main
storm modes. That said, shear increases markedly just above 6 km
though. As a result, if instability and equilibrium heights end
up being higher than currently advertised, this could increase
the potential for at least transient supercells. For now, the
level 1/5 severe threat appears appropriate, with a locally
strong downburst wind threat from isolated to widely scattered
convection. Activity could potentially linger through the
evening and into early Friday morning as some degree of WAA from
a modest southwesterly LLJ interacts with lingering elevated
instability, mainly north of I-80 and towards southern
Wisconsin.

Carlaw


Friday through Saturday Afternoon:

If any thunderstorms occur overnight Thursday night, it`s possible
isolated activity lingers past sunrise on Independence Day, or
perhaps debris cloud and outflow effects of decayed convection on
the wind field. With the quick building in of an amplified 592
DaM 500 mb ridge into the mid MS Valley, however, pronounced
capping should take hold through the morning.

With 850 mb temps in the upper teens to around 20 Celsius and 925
mb temps into the mid-upper 20s C during peak heating paired
with nearly full sunshine should yield highs into the lower to
mid 90s. Dew points are expected to mix out into the 65-70F
range, keeping peak heat indices at ~95-100F. If mid 90s highs
indeed occur at Chicago-O`Hare and Rockford, it would be the
warmest July 4th since 2012`s record setting 102F highs at both
sites. The only minor exception to the heat will likely be along
the Illinois shore. Modest south-southwest flow and the very
sharp land-lake thermal gradient should be conducive for a
subtle southeasterly lake breeze, capping high temps in the
upper 80s to around 90F along the shore. Friday night will be
warm and muggy but not as oppressive as during the height of the
June 21-23 heat wave.

The trend for Saturday has been a slight slowing of the
anticipated flattening out of the 500 mb ridge (heat dome),
meaning capping has become more likely to hold through much of if
not the entire daytime period. Can`t completely rule out an
isolated thunderstorm in our northwest half or third late in the
day. 850 mb and 925 mb temps may even be a smidge warmer than on
Friday, along with breezy southwest winds gusting to 30 mph.
Finally, the signal for dew points to mix out at peak heating is a
bit stronger than on Friday. Taking all these factors into
consideration, Saturday has the potential to reach the upper 90s
in spots, especially in the Chicago urban heat island. At the
least, mid 90s should be more prevalent than on Friday, especially
near and east of I-39 where any incoming thicker high cloud cover
should arrive after peak heating. With possibly warmer temps but
dew points a tick or two lower on Saturday, the end result should
again be peak heat indices in the ~95-100F range. Ultimately,
while it doesn`t appear likely at this time that we`ll be needing
Heat Advisory headlines, given that this will be a busy holiday
weekend, those with outdoor plans are encouraged to have a plan in
place to avoid heat related illnesses.

Saturday Evening through Tuesday:

As the 500 mb ridge axis flattens out late Saturday, a trough axis
will approach the mid MS Valley to the northwestern Great Lakes
corridor. A slow moving surface low embedded in this trough should
gradually drag its cold front across the area through Sunday
night. With convectively modulated impulses/MCVs likely in play, a
few rounds of scattered showers and thunderstorms are probable
(peak 40-50% PoPs) later Saturday night through Sunday night. Mid
and upper level flow still looks to be muted enough to keep severe
threats on the lower side (but not zero). Sunday will be very
warm and humid but likely not as hot with clouds and/or convection
around.

The signal has increased for the cold front passage and high
pressure building in behind it to scour out moisture and
instability temporarily Monday-Tuesday, which may result in a
quieter start to the work week than entailed by the (~20-50%) PoPs
in our forecast. This will likely take a few more model cycles
to iron out though. A couple days of increased shower and storm
chances may then follow for mid next week.

Castro

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1213 AM CDT Wed Jul 2 2025

Main Concerns:

- Lake breeze wind shift to northeast probable at GYY, possible
  at MDW, and unlikely at ORD this afternoon.

- Isolated TS may track southeast out of WI towards sunset this
  evening.

West winds will develop this morning and then continue the rest
of the current TAF period outside of possible lake influence.
Recent model guidance suggests that GYY remains the most likely
to observe a wind shift in the early afternoon, but even this
is uncertain. The (270-290 deg) westerly wind speeds around 10
kt should be able to provide enough resistance for the lake
breeze to make it out to MDW and particularly ORD. A fairly
robust VFR Cu field should develop on the lake breeze by midday,
but stout capping on forecast soundings makes anything more
than spotty low topped showers unlikely at this time.

A disturbance pushing southeast out of WI late in the day amidst
much less pronounced capping should translate to isolated gusty
TS that may then push into northern IL before dissipating with
sunset. If confidence in this scenario increases, may need to
consider some mention in the RFD TAF with later issuances.

Castro

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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