907
FXUS63 KDVN 142319
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
619 PM CDT Tue May 14 2024

.KEY MESSAGES...

-  Scattered showers and a few storms(south of I80) will come
   to an end this evening.

- Additional chances for periods of showers and storms are in
  the forecast for late Wednesday night through the upcoming
  weekend, with the most likely initial chances appearing on
  Thursday. But many dry hours in this stretch as well.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 247 PM CDT Tue May 14 2024

Tonight...Clusters of showers and some storms rotating around a low
pressure system near the STL area will continue to diminish and pull
off to the southeast as the evening progresses as that system
migrates up the OH RVR Valley. Some spotty heavy rainfall amounts
over an inch with ponding water possible in the south until then.
Then clearing from the north with northeasterly boundary layer(BL)
fetch cooling things off into the mid 40s north, to lower 50s south.
Some patchy fog possible in the far south after midnight where
clouds clear off the latest.

Wednesday...Upper MS RVR Valley bout of both sfc and upper ridging
will make for a fair Wx day with highs returning back into the 70s.
CU rule parameters suggest ambient cumulus development of at least
scattered coverage acrs the southwestern 2/3`s of the CWA, but
should not be enough to ruin a mostly sunny fcst.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 247 PM CDT Tue May 14 2024

Wednesday night and Thursday...Developing 25 KT H85 MB southwesterly
LLJ ahead of incoming shortwave may try to produce some low to mid
level warm air advection type showers or even a thunderstorm in the
western CWA late Wed night, but the local area looks to lay out in-
between the two main forcing areas of MN into WI, and KS into MO and
there may not be much into the local area until later on Thu. Maybe
a bit of a non-diurnal temp curve before dawn if southeasterly
return flow picks up especially west of the MS RVR. Lows mainly in
the 50s. Thursday the progressive short wave should continue to
generate or increase sctrd showers and some thunderstorms acrs the
area to likely coverage(60-70%), with the better support/forcing
north of I-80 for possibly higher coverage in those areas. Shear and
instability profiles are marginal at best to support a stronger
storm, but a PWAT feed of 1.2 to 1.4 inches will allow for precip
swaths of 0.20 to 0.50 of an inch by Thu evening. Temps in the 70s
Thu despite the clouds and sfc DPTs in the upper 50s to around 60.

Friday and Saturday...Ensemble indicated near split flow with a more
active southern stream from the southern plains to the southeastern
GRT LKS, may help keep most the area dry on Friday, with a low
chance for some of that activity bleeding north enough to get into
the southern CWA by afternoon. The loaded NBM POPs for Friday may be
too high taking into account this scenario. Upstream thermal ridging
edging this way with return flow and the northern stream storm track
taking shape acrs the northwestern high plains into the GRT LKS will
make far a warming Saturday with advected thicknesses supporting
highs in the low to mid 80s acrs much of the fcst area. Lower
confidence in modeling handling of ridge-riding shortwave which
could produce strong convection late Sat and Sat night,
uncertainty anyway how far south this activity may bleed down acrs
the upper MS RVR Valley and possibly advect into the local fcst area
from the north. We may be capped/have a EML shield by then but still
early for these kind of details or confidence in the set up.

Sunday through next Tuesday...Latest suite of medium range ensembles
support a more summer-like regime this period with short waves and
a quasi-stationary sfc boundary laying out on the northern fringe
of the thermal ridge for occasional development of storm clusters
or MCS`s traversing the upper midwest, especially at night induced
by nocturnal LLJ feed of high THTA-E air. Thus the rainfall could
really add up wherever this potential storm track lays out.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 617 PM CDT Tue May 14 2024

A transition to VFR weather is occurring at the start of this
upcoming period, with dry air spreading southwest into the area
north of Interstate 80 already, and will be to the south during
the evening hours. This will result in rapid improvement at CID
and MLI by 01-02Z as cigs scatter out and dissipate, and for
BRL, expect that transition around 04Z tonight. Afterwards,
expect a quiet period through Wednesday, with VFR conditions
prevailing on light northeast winds.

&&

.HYDROLOGY...
Issued at 247 PM CDT Tue May 14 2024

The heavier rainfall overnight was mainly south of I-80 and I-88
with some pockets of lighter amounts south of Moline towards Macomb
as well as in parts of NW MO. The higher totals of 0.75 to 1.5
inches were near and south of Iowa City. To the north, amounts were
mostly under a tenth of an inch.

The flood warning continues for the Wapsipinicon River near De Witt.
It is forecast to have a broad crest near 11.3 feet over the next 36
hours.

There was not much appreciable rainfall upstream of Conesville. The
RFC has the Cedar River at Conesville cresting under flood stage
tomorrow.  The flood watch has been canceled.

The Mississippi River may go over flood stage at Gladstone and
Burlington tomorrow or on Thursday. The flood watches for these
sites continue due to some uncertainty with the pockets of lighter
rainfall that fell overnight and relatively light totals forecast
for today. Will monitor river levels for now.  The current forecasts
take them both just one tenth of a foot over flood stage.

&&

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

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Ervin
HYDROLOGY...14