158
FXUS63 KDVN 270527
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1227 AM CDT Fri Jun 27 2025

.KEY MESSAGES...

- Additional heat headlines may be needed this weekend,
  particularly on Sunday.

- With a wet pattern across the area and a daily risk of showers
  and thunderstorms capable of producing heavy rainfall, area
  rivers are expected to see rises. Refer to the hydrology
  section for more information.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 211 PM CDT Thu Jun 26 2025

Hot and humid conditions were observed across the area, with
heat indices around 2 PM this afternoon around the 95 to 102
degree range, and temperatures hovering around 90 degrees for
most locations. We are keeping an eye on a line of showers and
storms that have developed over central Iowa ahead of a cold
front that will eventually cross our area by this evening into
the overnight hours, albeit in a decaying fashion after midnight
tonight. Before then, some air mass convection is progged by
some of the CAMs late this afternoon as instability builds to
the tune of 1500-2500 J/kg MLCAPE. Although deep-layer shear
appears to be quite meager (<25 knots), steep low-level lapse
rates and high Pwats to around 2 inches should support the
threat for locally strong winds due to wet microbursts. SPC has
maintained a Slight Risk (level 2 of 5) for severe weather for
areas along and northwest of a Sigourney Iowa to Galena Illinois
line, with a Marginal Risk (level 1 of 5) for severe storms
elsewhere in our CWA. Along the Highway 20 corridor, low-level
shear appears to be stronger due to a more veering wind profile
instead of a uni-directional profile farther south, so a brief
tornado can`t be ruled out across our far north.

Friday looks to be largely dry, with the line of showers and storms
diminishing to only a few showers by sunrise. CAM guidance suggests
very little in the way of additional activity along the front as it
sweeps through the CWA. Also, the front should help usher in some
cooler conditions, with high temperatures warming to the upper
70s north to the middle 80s south.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 226 PM CDT Thu Jun 26 2025

Friday night through Monday
Assessment...Very high (>90%) of heat and humidity continuing.

Heat and humidity builds back in for the weekend with Sunday
being the hottest day. It is possible for heat indices to once
again warm to above 100 degrees F as temperatures warm to near
90 degrees with lower to middle 70s dew points. LREF exceedance
probabilities of heat indices of 100 degrees or more are around
10 to 30% - something to keep an eye on.

With the heat dome back into the area for Sunday, the question
becomes will a weak upper level disturbance approaching the area
generate diurnal convection. The model consensus suggests this with
a 30 to 50% coverage Sunday afternoon/evening.

An approaching front on Monday (associated with the pattern change
aloft) raises questions regarding the rain potential. Several
deterministic model runs suggest very little in the way of rain.
However, there are several members from the respective ensemble runs
that generate rain. Thus, the model consensus is biased toward
the ensembles but the areal coverage for any rain is only
20-40%.

Monday night through Wednesday
Assessment...medium (40-60%) confidence on near normal temperatures.
Low (<25%) confidence on rain chances.

The pattern change to west-northwest flow aloft will help keep
temperatures around or slightly above normal. With the heat dome
suppressed southward, the more tropical moisture that would
fuel storms is not present. Thus, the deterministic model runs
and nearly all of their respective ensemble members have dry
conditions Monday night through Wednesday.

However, there are weak disturbances in the flow aloft moving
through the area Tuesday and Wednesday. Thus, we cannot fully
rule out the possibility of a rogue storm developing during the
diurnal heating cycle on Tuesday and Wednesday. If this were to
occur, areal coverage would be under 10 percent.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1221 AM CDT Fri Jun 27 2025

Widespread showers and thunderstorms are now ending except near
BRL, where another wave of showers and thunderstorms will
continue through 07Z tonight. An isolated shower or brief
thunderstorm could occur as far north as MLI in this same
period. Otherwise, a dry period will now continue through
Friday evening, as a slow moving cold front arrives.
Unfortunately, it looks like stratus will build in before the
front reaches our area, and this will linger through much of
Friday morning. Cigs as low as 500 ft are possible, but most
sites will see 1500 to 2500 stratus cigs through the morning.
The front does not have much of strong push of air to it, as
west to northwest winds only reach 6-10kts during the day. VFR
weather is expected by noon in all areas though as the strong
summer sun increases mixing through the drier air aloft.

&&

.HYDROLOGY...
Issued at 212 PM CDT Thu Jun 26 2025

Forecast crests along portions of the Cedar River have trended lower
into next week due to less rainfall anticipated over the next 24
hours, particularly across the upstream section of the basin
(northwest of Vinton). Additional rounds of heavy rainfall over the
weekend into early next week could result in changes to the timing
and magnitude of the forecast crests. However, the latest river
level forecasts are only accounting for forecast rainfall (QPF) over
the next 24 hours. Confidence has increased enough at Marengo along
the Iowa River to potentially reach Minor flood stage by this
weekend, so have issued a River Flood Watch for this site

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...08/Schultz
AVIATION...Ervin
HYDROLOGY...Uttech