Springfield, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

433
FXUS63 KILX 201715
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1215 PM CDT Sun Jul 20 2025

.KEY MESSAGES...

- Periods of thunderstorms this morning and especially this
  evening into tonight will be capable of generating intense
  rainfall leading to flash flooding. There is a level 3 of 4
  (moderate) risk for excessive rainfall for much of central IL,
  centered near I-72. A Flash Flood Watch is also in effect.

- These storms may also produce severe weather, mainly from
  damaging winds, though there is a nonzero chance of large hail
  and tornadoes as well. There is a level 2 of 5 (slight) risk.

- A heat wave will impact the region beginning Tuesday, with the
  worst conditions Wednesday and Thursday. Both days, there is a
  40-60% chance heat indices surpass 110 degrees.

&&

.DISCUSSION...
Issued at 202 AM CDT Sun Jul 20 2025

***** HEAVY THUNDERSTORMS THIS MORNING *****

MRMS regional radar mosaic shows several clusters of thunderstorms
scattered across Iowa, Nebraska, northern Kansas, and northern
Missouri at 2am. Though there are considerable differences in
specifics of where, when, and how strong this activity will be by
the time it reaches us, the 00z CAMs generally suggest these areas
of storms will drift towards us throughout the morning. Given the
deep moisture in place across the region (PWATs 2-2.3 inches), and
strong southwesterly moisture transport feeding into these storms,
it seems they`ll produce heavy rain, though thankfully the greatest
overlap in the 00z CAMs in location of heaviest rainfall is near the
I-74 corridor this morning - an area that missed out on much of
yesterday`s rain. Nonetheless, with individual CAMs spitting out
isolated amounts over 2 inches (most of which falling in around an
hour) - reflected in the HREF`s LPMM - we feel there may be some
localized hydrological issues in urbanized areas. In addition, we
could see there being some gusty to locally damaging winds
accompanying the strongest storms, particularly if a linear segment
materializes. SPC has much of the area outlooked in a level 2 of 5
(slight) risk.

***** HEAVY RAIN, FLOODING RISK, TONIGHT *****

Along the remnant ouflow boundary from this morning`s storms, strong
moisture transport (200-300 gm/kg/s, if you believe the 00z NAM) in
an already extremely moist airmass characterized by a deep warm
cloud layer of 13-14 kft will foster development of efficient rain-
producing storms by late evening-early overnight period. While
Corfidi upshear vectors are running ~ 16-23 kt in forecast
soundings, which is a little higher than what would be considered
conceptually ideal (i.e., <15kt)for slow-stationary storm motions
in backbuilding storms, we cannot ignore the signal for pockets
of very high precip amounts in the 00z CAMs given the extremely
moist environment. Dictated by mesoscale factors not yet apparent
in our observations (and forecast very differently by each highres
model) uncertainty is high in the location and magnitude of
heaviest rainfall and whether it may impact infrastructure.
However, each 00z HREF member has pockets of over 4 inches of
rain, and a couple members have bullseyes of 8+ inches, in some
portion of our CWA south of the I-74 corridor where some locations
saw over 3 inches of rainfall yesterday; consequently, WPC has
placed the area in a level 3 of 4 (moderate) risk for excessive
rainfall and we felt that there`s enough potential for significant
flooding impacts to pull the trigger on a Flood Watch for our
entire area. Stay tuned to the forecast for updates, have multiple
ways to receive warnings, and remember to never attempt driving
through a flooded roadway.

***** HUMID, INCREASINGLY HOT TOWARD MIDWEEK *****

An upper level ridge will slowly shift into the region towards the
middle of the work week, with heat indices increasing Tuesday and
peaking Wednesday into at least Thursday. While guidance shows more
and more of a signal for at least slight (20%) chances for diurnally
driven convection, subsidence under the ridge`s influence should be
sufficient to delay convective initiation (and limit general
coverage) long enough each day that temperatures have the
opportunity to warm into at least the low 90s, with ET from well-
watered crops surging dewpoints into the 78-82 degree range. This
will result in heat indices in the 105-115 degree range. As heat is
the number 1 weather cause of death in the U.S., we`d like to
continue encouraging folks to plan any outdoor activities outside
the hottest portion of the day (11am-7pm), and even consider
canceling them/moving them indoors. For those who do end up
outside in the heat, stay hydrated, take breaks in the shade (or
better yet, AC), and remain vigilant for any signs of heat
illness in yourself and others. Model spread remains vast and
hence uncertainty high in the duration of this heat, though
promising signs of the ridge shifting east or at least weakening
slightly as a shortwave trough approaches from the northwest do
appear this weekend.

Bumgardner

&&

.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1213 PM CDT Sun Jul 20 2025

Unsettled weather will be in play across central Illinois with a
chance of precip through much of the period. While current
activity is currently in a downward trend in both intensity and
coverage, anticipate storms will redevelop late this afternoon or
evening with a west-to-east oriented line or possibly two setting
up across central Illinois. Storms training over the same area may
lead to a prolonged period of storms on or near station, though
exact timing and location details remain uncertain. Outside of the
precip chances, anticipate VFR conditions this afternoon to lower
to MVFR and eventually IFR overnight. Light and variable winds
currently in place should eventually favor a northeast direction
around 10 kt this evening and overnight, veering to an easterly
direction Monday morning.

Deubelbeiss

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday morning for ILZ027>031-036>038-
040>057-061>063-066>068-071>073.

&&

$$