630
FXUS63 KDVN 171747
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1247 PM CDT Tue Jun 17 2025

...18z Aviation Update...

.KEY MESSAGES...

- Multiple rounds of thunderstorms are possible through
  Wednesday. Severe thunderstorms are possible today and
  Wednesday.

- Confidence remains low on the timing and coverage of this
  activity, given slight differences between the models and the
  impacts of previous convection.

- Very warm/hot conditions are becoming more likely this weekend
  into early next week with high temperature in the 90s and heat
  indices near 100.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 248 AM CDT Tue Jun 17 2025

At 2 AM, an MCS continues to dive southeastward across Nebraska
into Kansas with the portion of the line in central Iowa
significantly diminishing. An MCV is visible on radar and in
the surface wind field across central Nebraska. Locally,
temperatures are in the upper 60s to lower 70s with dewpoints
also in the upper 60s to lower 70s.

At 500 MB, there is zonal flow in place across the CONUS. An
initial shortwave is moving into central Illinois this morning
with some models showing subtle shortwave ridging over eastern
Iowa. Within the zonal flow, synoptic models predict that a
pair of shortwaves will move across eastern Iowa, northwest
Illinois and far northeast Missouri. The first wave is subtle
and moves across the Iowa/Missouri border during the afternoon.
CAPE is increasing during this period but 0 to 6 KM shear is in
the range of 15 to 20 knots. This will result in CAPE driven
storms as moisture advection brings dewpoints in the 70s across
the area increasing CAPE across the area. Think that this will
limit organized severe potential with the afternoon storms.
Collapsing cores with storms could cause damaging thunderstorm
wind gusts at the surface. Models show precipitable water values
around 1.50 inches so heavy rain will be possible with any
storms that develop. High temperatures today will be in the mid
to upper 80s.

A second, stronger shortwave is forecast to overspread the the area
tonight with the current timing looking like it will occur after
03 UTC. During this period, 0 to 6 km shear increase to around
30 knots. The area will remain in the warm sector as surface low
lifts into central or eastern Iowa. The NAM is the farthest
south with the surface low bringing it close to the Quad CIties
by 12 UTC on Wednesday while other models bring it to near
Waterloo. The warm sector across the region combined with the
stronger shear will bring the risk of large hail and damaging
wind gusts. Precipitable water increase to 1.70 to 1.80 inches
tonight with more heavy rain possible in storms. Low
temperatures will tonight will be in the mid to upper 60s.

For these reasons, there is a Slight (level 2 out of 5) Risk west of
a curving line from Vinton to Cedar Rapids to Burlington to
Augusta illinois with a Marginal (level 1 out of 5) Risk to the
north and east.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 233 PM CDT Mon Jun 16 2025

We`re not out of the woods with the severe storm threat Wednesday as
the aforementioned upper-level trough translates through the
area. The convective parameter space continues to indicate
hefty amounts of instability, with perhaps some stronger deep-
layer shear thanks to the nocturnal LLJ persisting into the
morning hours. An attendant 850 low does appear to shift to the
northeast early in the day Wednesday, which will likely keep the
severe threat later on in the day to our east. SPC has also
maintained the Slight Risk for severe weather across our far and
east and far southeast areas, with Marginal Risk for locations
southeast of a line from Dubuque, IA to Sigourney, IA. Chances
of showers and storms should remain in the wake of the 850 low
as a few additional PVA impulses move through the area. Overall,
the remainder of the extended period from Thursday through
Sunday looks largely dry, but we can`t rule out a chance of
showers and storms on Friday.

Attention then turns to big-time upper-level ridging for the
upcoming weekend, which will help push the heat dome farther
northward over our area. Both the EC and GEFS ensembles indicate 850
mb temperatures around the 23 to 26 C range, which is near the daily
maximum for the SPC sounding climatology on Saturday. Additionally,
the ECMWF EFI indicates values between 0.7 to 0.9 for high
temperatures, which increases confidence in a hot air mass settling
in. High temperatures likely warming into the 90s both days, with
heat indices possibly reaching 100 degrees F. The LREF exceedance
probability of heat indices of 100 degrees is roughly around 30 to
50%, so we will need to keep an eye on some hot and humid conditions
coming for the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1242 PM CDT Tue Jun 17 2025

Generally a VFR fcst until late this afternoon when sctrd to
isolated showers and thunderstorms pop up and move into the
vicinity of the sites. There will be passing MVFR to IFR reduced
VSBYs` and CIGs with this activity through mid evening, as well
as variable wind gust surges and direction changes from storm
outflow. Sfc wind fields away from the storms will be light and
variable or generally from the west at 4-8 KTs. There may be a
precip lull from late evening to a bit after midnight, when a
second round of sctrd showers/storms or even storm clusters
move into the area from the west/southwest late tonight. These
later night storms will also bring bouts of passing MVFR to IFR
conditions as well as variable higher wind gusts into Wed
morning. With some increase and convergence in LLVL moisture,
there may be low MVFR to IFR CIGs even away from the precip as
well as light fog. Some improvement by late morning as the rain
moves off to the east.

&&

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

&&

$$

SHORT TERM...Cousins
LONG TERM...Schultz
AVIATION...12