024
FXUS63 KDVN 180005
AFDDVN

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

.KEY MESSAGES...

- Multiple rounds of thunderstorms are possible through
  Wednesday, with a few severe storms possible tonight and
  Wednesday. Another chance(low)in the north Thursday night.

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

- Hot conditions are becoming more likely by this weekend into
  early next week, with high temps in the 90s and heat indices
  into the 100`s.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 229 PM CDT Tue Jun 17 2025

Tonight...Looking at satellite data including water vapor imagery,
one upper level wave/MCV was seen swirling acrs southwest into
central IA ATTM, and another larger SW acrs central NE into northern
KS. The closest wave upstream should spark isolated to sctrd showers
and thunderstorms acrs the local area as it encounters diminished
EML and 1000-2000 J/kg MLCAPEs. Shear profiles and low to mid layer
lapse rates are marginal at best, thus don`t see much of a
widespread severe threat this evening. But 1000+ DCAPEs in place
make for a chance of gusty storm outflow winds up to 50 MPH. Growing
PWATs to around 1.8" also support locally heavy downpours at high
rates until the storm collapses on itself. Then there may be a lull
in the activity from late evening to a little past midnight, before
the next approaching wave out of the central plains starts to roll
this way. This wave will look to utilize an increasing 30+ KT
southwesterly LLJ to induce more sctrd thunderstorms or storm
clusters moving in from the west/southwest late tonight into Wed
morning. A few models even indicate an MCS moving acrs the area late
tonight. Again shear and lapse rates seem not to be there to support
much a severe threat late tonight, with locally heavy rain and some
marginal wind gusts the main threats into Wed morning. PWAT`s
growing to 2 inches may allow for some swaths of 1-2 inches of
rainfall by mid Wed morning, and wouldn`t rule out some urban and
small stream flooding in areas that get hit by a couple rounds of
storms. Overnight lows held up in the mid to upper 60s even taking
into account rain-cooled outflow.

Wednesday...Will have to walk ongoing storm clusters/MCS acrs the
area during the morning to midday with the main upper wave. Again
heavy rainfall will occur with this activity until it moves out. This
system will flare up to stronger levels Wed well off to the east of
the local area of concern. Cloud cover and convective debris should
keep temps down in the 70s during the day. With the main upper trof
axis still progressing acrs the area, many models/CAMs are
developing more sctrd showers and storms acrs the area Wed afternoon
and evening in the wake of the morning system. Some uncertainty on
how much heating and instability there will be to develop more
storms, and it may be just some following showers into the evening.
The upper trof axis will progress off to the east Wed evening,
taking the shower support with it. Overnight low temps generally in
the lower 60s, and will bank on enough west sfc wind flow and
short nights to prevent fog formation acrs the heavy rainfall
areas.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 229 PM CDT Tue Jun 17 2025

Thursday...Both sfc and upper ridging should make this day mainly
dry and warming with diminishing convective debris. Inverted-V
profiles on fcst soundings up over H85 MB show good mixing/warming
potential back into the mid to upper 80s for much of the area.
Latest ensembles suggest brunt of upstream heat dome/upper ridge to
adjust up the plains and MO RVR valley. With the ridge`s leeside
west-northwesterlies steering flow from the northern plains into the
southeastern GRT LKS, a possible ridge-riding short wave may ignite
convective clusters or MCS type development acrs the northern plains
into MN, with some chance for some of this activity to bleed down
southeastward enough to clip the northern or northeastern DVN CWA
late Thu night into Friday morning. Or it could remain totally north
of our area of concern. Of course quite a bit uncertainty with this
scenario at this time but will have to maintain Thu night chances.

Friday...Another day that depends on what can occur during the
previous period and if any convective debris or lingering storms can
make it down acrs the area Friday morning into midday If we do have
debris or lingering storms out of Thu night, the majority of the
model solutions flush this activity back north or erode it with
ongoing ridge building and warming thermal column depth. Incoming
EML and ridging should make for a mainly dry and hot end to the
week. Lack of any debris or early enough day erosion will allow a
return to the 90s Friday.

Saturday through Monday...The latest suite of medium range ensembles
still paint a hot weekend into early next week period as bulk of a
large thermal ridge engulfs the midwest into eastern OH RVR valley.
Latest synoptic scale feature and thermal gradient alignment suggest
the ring of fire around the northern periphery of the upper ridge to
lay out to the north in a normal deep summer fashion from the
northern plains, over to the eastern GRT LKS. There may be a low
chance 20-30 percent for some of this activity to bleed down south
enough to make it into the northern CWA late night, if even in a
decaying fashion. Sunday night into Monday morning may be one such
window. Otherwise it will take for the ridge to break down and shift
east to allow increased precip chances by mid next week. As for the
heat, currently projected H85 temps suggest highs in the low to mid
90s for much of this period. If sfc DPTs can make it into the upper
60s to mid 70s, there will be headline-able heat index readings into
the triple digits.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 705 PM CDT Tue Jun 17 2025

Forecast concerns for the terminals...

- Scattered showers with embedded thunderstorms this evening.

- Period of dry weather tonight before another round of
  scattered showers and thunderstorms returns Wednesday morning.

- MVFR ceilings to develop late tonight and persist through
  Wednesday morning. Some IFR ceilings possible as well.


An upper disturbance and weak front will continue to support
scattered showers with isolated embedded thunderstorms through
03-04z this evening. While additional showers and storms are
trying to develop further to the west in central IA, they are
expected to diminish prior to reaching the TAF sites. Therefore,
a period of dry weather is expected overnight before another
upper disturbance brings the next round of showers and
thunderstorms through the terminals Wednesday morning. Given
that the instability on Wednesday is forecast to be notably
weaker than today, suspect the coverage of thunder will be
more spotty (around 20-30% coverage) in nature so have opted to
maintain the PROB30 mention for this potential at this time.
Showers and any storms will gradually move east of the terminals
after 20z Wednesday with mostly dry conditions expected
thereafter. However, isolated showers may linger through
Wednesday evening.

Outside of the rain, winds will become more variable overnight
before settling into a east-southeast direction Wednesday
morning. Directions will then become northwesterly Wednesday
afternoon as the rain ends with speeds in the 5-10 kt range
through the forecast period. Finally, ceilings this evening will
remain VFR with cloud bases around 10000-15000 ft but are
expected to gradually lower into the MVFR range by Wednesday
morning as a surface low develops and rain returns. Furthermore,
some guidance continues to hint at the possibility for IFR
ceilings to develop in spots (15-20% chance) but given this is
lower confidence have decided to handle with a SCT010 to SCT012
mention for now. Regardless, ceilings are expected to rise back
to VFR as rain tapers Wednesday afternoon.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Yack