949
FXUS63 KDVN 251037
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
537 AM CDT Fri Jul 25 2025

...Updated for 12z Aviation...

.KEY MESSAGES...

- Chance of showers and storms today mainly south of Hwy 30,
  increasing coverage tonight into Saturday AM with heavy
  rainfall and localized flooding potential particularly south
  of I-80. Gusty winds are also possible with a Marginal Risk
  or level 1 of 5 for severe weather for parts of the area.

- Heat builds back in Sunday through Tuesday, potentially
  dangerous, but there will also be episodes of storms making
  for a challenging temperature forecast and low confidence on
  the spatial extent and magnitude of the heat (day to day
  evaluation needed).

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 320 AM CDT Fri Jul 25 2025

Baggy/messy surface pattern noted early this morning across the
region. In general there appears to be a couple of boundaries,
one across our north /quasi-stationary/ a demarcation between
somewhat drier air across parts of the dakotas through MN/WI
and very moist/humid air across much of our region, with a
second boundary /outflow enhanced/ suggested further south
across MO through central IL. Water vapor imagery shows several
vorticity maxima some convectively enhanced (MCVs) from sw KS
and OK panhandle into IL with weak w/sw flow on the northwest
periphery of the Bermuda high off the SE Coast.

The main challenge over the next 24-48 hours will be trying to pin
down the timing/track of these perturbations and subsequent
narrowing of corridors and timing of greatest precipitation chances.
Overall, water vapor doesn`t look too promising for much of a gap
in precipitation, but trends early this morning look to suggest a
waning of coverage for a time later this morning and early afternoon.
By mid to late afternoon into early evening we may see a bit of an
uptick with at least scattered convection focusing mainly south
of I-80, as vorticity maxima into nw MO moves in. Cloud cover may
limit instability a bit, and with environmental shear fairly
weak and tall/skinny CAPE suggests the primary threat will be
with locally heavy rain with somewhat slow moving convection within
an anomalously moist airmass with 2.1 inch PWAT sampled on 00z
DVN raob which is above 90th percentile and nearing daily max
per SPC climatology. But, can`t also completely rule out some gusty
winds with any precip loading. Will need to keep tabs on any
potential for more prevalent/persistent cloud breaks owing to
greater instability and/or any augmented vertical wind shear aided
by the vort max to perhaps bring a bit more threat for wind.
Otherwise, it`s primarily a torrential rain and localized flood
threat that really should ramp up tonight into Saturday morning
along with a burgeoning convective footprint, aided by what looks
to be a fairly decent MCV currently lifting up into sw KS in conjunction
with the 2"+ PWATs. Can`t rule out needing a Flood Watch for flash
flood concerns, but too much uncertainty at this time dependent on
how the convection evolves today to help define a corridor for the
greatest concern for flash flooding. Right now, in general this would
appear to be south of I-80. Some weakening/diminishing in coverage is
once again likely late Saturday AM into early afternoon, with more
redevelopment (scattered coverage) Saturday mid to late afternoon
along and especially east of the Mississippi River with some potential
for strong gusty winds, dependent upon degree of cloud cover and instability.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 320 AM CDT Fri Jul 25 2025

Saturday night and Sunday models support some amplification of the
upper ridge overhead. The building heights aloft and lack of
any appreciable forcing may limit storm coverage and support
more diurnally induced widely scattered activity. This upper
ridge and increasing heights aloft will also bring a return of the
heat. With corn sweat in prime-time, we`ll see some very humid
to oppressive conditions with dew points likely in the mid/upper
70s and possibly 80 in spots. This will bring the potential for
dangerous heat index readings exceeding 100 to around 105 degrees
across much of the area, provided convection and cloud cover stay
limited to allow highs to top out in the upper 80s to around 90.

Monday through Wednesday, the pattern looks to become quite
conducive for periodic storm complexes with an attendant heavy rain
and severe weather threat, as the ridge is suppressed further
to the south allowing our region to reside in the action zone or
`ring of fire` with main belt of westerlies strengthening and
shifting southward through the Northern Plains and Upper Midwest.
This timeframe will also hold the potential for a continuation
of dangerous heat and humidity, but this will likely be a day to
day evaluation because of the uncertainty with temperatures given
the active pattern and potential for rounds of convection.

Beyond mid-week though there are signs pointing to a cooler and
somewhat drier pattern for late next week, as we see a bout
of northwest flow attendant to an eastern Canada low.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 529 AM CDT Fri Jul 25 2025

Patchy shallow fog will result in fluctuating visibility potential
from LIFR to MVFR at the start of the period for CID, and
possibly DBQ where clouds have thinned. Otherwise, predominantly
MVFR to VFR conditions are expected today through this evening
with spotty shower and storm activity most favored near BRL and
lower confidence elsewhere. Showers and storms are expected to
then increase in coverage after 04z/26th through the end of the
TAF period and immediately beyond, particularly at BRL, MLI and
CID with bouts of MVFR to IFR conditions expected in the stronger
activity.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...McClure
LONG TERM...McClure
AVIATION...McClure