464
FXUS63 KDVN 152316
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
616 PM CDT Wed May 15 2024

.KEY MESSAGES...

- Scattered showers and a few storms late tonight and Thursday.

- Highs warming into the 80s for several days ahead.

- Depending on where a developing storm track lays out, it could
  be a potentially wet pattern across the region next week with
  several rounds of heavy rain possible.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 250 PM CDT Wed May 15 2024

Tonight...Smoke layer in the north seems to be thinning and starting
to get flushed back northward with return flow aloft. Late tonight
and tomorrow`s weather maker short wave showing up nicely on water
vapor imagery acrs the central plains into the eastern Dakotas. This
system will approach later tonight but initially be battling dry air
and associated leeside WAA type precip may erode or stay aloft as it
tries to move in this evening and even portions of the overnight.
But eventually some spotty or sctrd light showers/sprinkles and even
an isolated thunderstorm should make into portions of the area if
not to a little before dawn, especially west of the MS RVR. Temps
falling into the 50s for lows overnight under shallow inversion, but
increasing southeasterly to south return flow may make for pre-dawn
non-diurnal trends especially west.

Thursday...The incoming short wave with southwesterly 20 KT moisture
feed vectors aloft ushering in 1.2 to 1.4 inch PWATs will make do to
column saturation with showers and a little bit of embedded thunder
blossoming and becoming a bit more widespread, but that may occur
more acrs the east or along and east of the local DVN fcst area
during the morning, depending on wave propagation speed. Also of
interest, if there is not that much substantial morning activity and
related debris, diurnal heating may set the stage for sctrd
thunderstorms developing along the front more Thu afternoon into
early evening in a narrow SBCAPE ribbon. In this scenario, storm
layer shear of 30-40 KTs and 1000+ MUCAPEs may support some stronger
storm cells along the front capable of marginally severe hail and
wind gusts, especially north of I80 acrs far eastern IA into
northwestern IL. But a better, more organized area for strong storms
looks to be more acrs southeastern WI in LLVL backed wind field near
the main warm front. Will have varying amounts of POPs through the
day. High temps in the low to mid 70s, with some areas pushing the
upper 70s away from the clouds/precip.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 250 PM CDT Wed May 15 2024

Friday...A day of somewhat discrepancy, but the majority of ensemble
blends suggest that this day may be mainly dry or a few light
showers skirt acrs the far southeastern CWA. Will adjust any POPs
that way and ignore the outlier GFS which slow rolls a southern
stream cut-off upper low far enough north for occasional rains acrs
much of the area Friday into Saturday. Away from the rains and
thicker cloud cover, thermal profiles support highs in the upper 70s
or even around 80.

Saturday and Sunday...Medium range model synoptic scale pattern
trends still point to a building thermal ridge out west, with a
ridge-riding vigorous shortwave digging down into the northwestern
GRT LKS by Sat evening. Currently indicated pre-system warm draw
supports highs in the mid 80s(50-75 percentile). Associated sfc
front squeezing into the area from the west-northwest may provide
forcing focus for shower and thunderstorm development late Sat
afternoon and evening, but the feature will be battling a EML and if
anything goes, it may be spotty and elevated in nature. In the wake
of the passing front, Sunday looks fair and warm(upper 70s-low 80s).
Medium range ensembles then continue to lay out lower amplitude
thermal ridge and northern fringe storm track somewhere acrs the
midwest or upper midwest. Where this storm highway and possible
quasi-stationary west-to-east sfc front aligns will be a big
implication to what areas will be suspect to occasional storm cluster
or MCS development and propagation. A few ensemble solutions such as
the ECMWF start with the track developing overhead and an MCS as
early as Sunday night into Monday morning. Sunday night will
probably be a start of the need for POP chances almost every period
into the mid week.

Monday through next Wednesday...Building upon thoughts in the
previous paragraph, a thermal ridge containing Gulf fed rich THTA-E
air and it`s northern fringe will be the focus for occasional storm
cluster or MCS development(most likely at night thanks to convergent
LLJ feeds) and then propagation paths overnight and into the
following day this period. But still uncertainty on how far north
or south this storm track lays out is still there, plus the fact
that one storm complex and resulting debris lay out will affect the
set-up for the next day, something the models don`t handle well
especially that far out. Thus plentiful POPs will have to ride early
to mid week, despite that there will also be plenty of dry hours in
between.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 612 PM CDT Wed May 15 2024

A VFR night is in store tonight across all of eastern Iowa and
northwest Illinois, as dry air remains in place, though rain
showers will approach the region towards morning from the west.
These showers and storms will be weakening and dissipating as
the move into eastern Iowa during the 10z to 14z time frame
Thursday, and by mid morning, may be very widely scattered. This
leads to lower than normal confidence in any MVFR cigs
developing during the middle of the warm season day coming up,
despite some increase in dewpoints to near 60. I`ve inclined to
go with a scattered to broken lower VFR cig around 3500 ft
during the afternoon hours, rather than the model forecast of
2500 ft cigs. Anyhow, some shower activity remains possible into
the afternoon, with isolated thunderstorms possible as well, but
coverage is too low to include in any TAF at this time.

&&

.HYDROLOGY...
Issued at 1006 AM CDT Wed May 15 2024

Changes: None

Discussion:

River flood warnings continue for the lower Wapsipinicon River
near De Witt and for a portion of the Mississippi River from
Gladstone, IL through Burlington, IA.

The lower Wapsipinicon River near De Witt is just coming off a
broad crest. The forecast has it dropping below flood stage
Thursday afternoon.

For the Mississippi...the river continues to rise from New
Boston, IL through Gregory Landing, MO. With the exception of
Gladstone and Burlington, the river is forecast to crest below
flood stage. At Gladstone and Burlington, the river will crest
just above flood stage Thursday night.

The lower Cedar River near Conesville is nearing a crest just
below flood stage. The river will hold just below flood stage
through tonight before beginning a slow fall on Thursday.

An active weather pattern is expected across the area through
next week. While rainfall amounts are somewhat uncertain, any
heavy rainfall would minimally prolong high river levels on
tributary rivers in eastern Iowa and on the Mississippi south of
New Boston, IL.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Ervin
HYDROLOGY...08