584
FXUS63 KDVN 012337
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
637 PM CDT Sun Jun 1 2025

.KEY MESSAGES...

- Smoke aloft from Canadian wildfires will continue to stream southward
  over our region through Monday. Some of the smoke could mix
  down to the surface and lead to reduced air quality at times,
  especially Monday afternoon.

- An active pattern returns Tuesday through Thursday, bringing
  high chances (70-90%) for widespread showers and storms. Some
  storms could become strong to severe Tuesday, although
  uncertainty remains on the details and overall potential.

- Largely beneficial rainfall is expected later this week, with
  most of it falling Tuesday and Tuesday night. Flooding threat
  should remain minimal, except if copious rainfall occurs over
  urban areas.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 207 PM CDT Sun Jun 1 2025

High pressure over the western Great Lakes will continue to dominate
over the region for the rest of today, keeping conditions dry under
hazy sunshine. Current geocolor satellite imagery continues to show
an expansive area of smoke aloft over the upper Midwest from
Canadian wildfires, which should only persist over the region
through the day Monday as a longwave upper-level trough loiters over
the northeastern CONUS. On the western side of this trough,
northerly flow aloft is ushering all of this smoke southward. Both
the RAP and HRRR smoke models suggest that not a lot of smoke is
expected to mix down to the surface today due to a lack of deep
boundary layer mixing, but some deeper mixing to around 800 mb per
the 01.12z NAM and GFS on Monday could lead to some mix-down of the
smoke, which could result in minor reductions in air quality.

In terms of temperatures, high temperatures will likely be a hair
cooler than what some guidance indicates due to the smoke, but
warmer than average conditions are still expected. Tonight`s lows
should only dip to the middle to upper 50s for most. Monday`s highs
should be very warm, thanks to the aforementioned high pressure
departing the region, leading to southerly return flow/warm air
advection. The latest ECMWF EFI for high temperatures on Monday is
now showing a larger footprint for values between 0.8 to 0.9 than
previous runs, with a few isolated spots exceeding 0.95. This
suggests a pretty strong signal for very warm conditions Monday.
850mb temps in the mid to upper teens C will help push highs into
the upper 80s, with a few locations potentially reaching around 90
degrees. However, with dewpoints only in the mid 50s to near 60, the
heat indices will closely match the air temperature.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 207 PM CDT Sun Jun 1 2025

For Tuesday through Thursday, a more active pattern is expected as
an upper-level trough and attendant cold front approaches the
region. Abundant moisture from the Gulf should advect higher PWAT
values around 1.7 to 2.0 inches per the GEFS ensemble plumes by
Tuesday afternoon. This first trough should phase in with a southern
stream trough coming from the southwestern CONUS, arriving on
Thursday. Combined, these two waves will result in a prolonged
period of rainfall chances Tuesday through Thursday (though not a
complete washout), with a soaking rainfall expected across the area.
Chances of rain will be highest Tuesday PM into Wednesday (70-90
percent). Looking at a 72-hr period from Tuesday through Thursday,
NBM exceedance probabilities of one inch or more of total rainfall
is between 60 to 80 percent and between 30 to 50 percent for two
inches or more. Although we are outlooked for a Slight Risk (level 2
of 4) for excessive rainfall/flash flooding in eastern IA into west-
central IL and northeastern MO by WPC, thinking that the flooding
threat will be mainly isolated to urban areas as already-planted
crops/fields should be able to soak up the moisture pretty
efficiently. However, if copious rainfall occurs over urban areas,
there could be some street flooding, especially in areas of poor
drainage.

In terms of severe weather potential during this active period, the
main focus continues to be on Tuesday as we are currently outlooked
by SPC in a Slight Risk (level 2 of 5) for most of the CWA. While
the various ML guidance paints a Slight Risk equivalent for severe
weather for most of the CWA, uncertainty remains on the northward
extent of the severe potential with this system as mid-level lapse
rates appear to be fairly meager (<6 C/km), and the degree of
boundary layer heating could be limited within the plume of higher
moisture air. It`s possible that the Slight Risk could be cut back
for our CWA, but we will see how/if subsequent outlooks change.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 626 PM CDT Sun Jun 1 2025

Eastern Iowa TAF sites sit on the western edge of high pressure
centered across Illinois, Indiana, and western Iowa. Clouds are
mostly around 25000 ft with smoke across the area from wildfires
in Canada. The smoke is not expected to make it to the surface
and reduce visibility. Winds are forecast to become light and
variable this evening before increasing to 10 knots by 16 UTC
on Monday with gusts up to 20 knots through the afternoon.
Conditions are forecast to be VFR through the period.

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Schultz/Uttech
AVIATION...Cousins