779
FXUS63 KDVN 220826
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
326 AM CDT Wed May 22 2024

.KEY MESSAGES...

- Dry conditions for most today, with seasonable temperatures
  and comfortable humidity. There is a slight chance (15%) of a
  shower/storm along of north of Hwy 20 in Iowa this afternoon.

- Active weather returns by Friday and again early next week
  with increasing shower and thunderstorm chances. There is a
  Marginal Risk (level 1 of 5) for severe weather on Friday.

- The Cedar, Iowa, Skunk, and the Wapsi rivers are expected to
  rise with some sites going into flood in the next 3-4 days
  due to the recent 2-5 inch rainfall upstream.


&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 305 AM CDT Wed May 22 2024

Very active weather in the past 18-24 hrs was observed across
the area. Several reports of large hail, high winds over 80 mph,
downed trees and powerlines, semi-trailers overturned, and
roofs blown down were reported last evening. Early morning GOES
16 water vapor imagery shows the system responsible for all this
was located over western Lake Superior. The main cold front
associated with this system was slow to exit the area tonight
and just now has pushed into northeast IL. Winds have also
remained up overnight gusting over 30 mph at times.

Today...a much needed quiet day is in store for the region,
with weak high pressure moving into the mid-Mississippi valley.
Forecast models all suggest that the low clouds overhead will
begin to diminish by 9am giving way to mostly sunny skies by
late morning. Deep mixing today will result in afternoon highs
topping out in the middle 70s, with comfortable humidity.

A weak upper level wave currently over Nebraska will track
across Iowa today, bringing an increase in mid and high level
clouds by late afternoon. The latest RAP/HRRR runs even suggest
some showers could develop over northern IA and clip areas along
and north of Hwy 20. After collaboration with DMX/ARX have
added some slight chance (15%) PoPs for this possibilty, but
most will stay dry today.

Tonight...high pressure overhead and clear skies will set the
stage for a pleasant late May evening. Overnight lows will drop
into the upper 40s and low 50s.


&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 305 AM CDT Wed May 22 2024

Thursday...quiet and dry conditions will be seen with 850mb
temps warming to 13C and southeast return flow boosting
afternoon temperatures into the upper 70s and low 80s.

Thursday night-Friday...00z models and their ensembles all show
a strong upper level wave moving into the northern Great Plains,
with diffluent flow developing over the Midwest. Another cold
front will track east across Iowa with strong moisture
transport expected ahead of it (PWs increasing to 1.5") into
the local area. Sufficient shear and instability will present a
risk for some stronger storms to develop in the warm sector
which may again be over the local area. For this reason, SPC has
a Day 3 Marginal (level 1 of 5) risk for severe weather across
the entire outlook area. Timing of the fropa will be critical as
to what impacts may be seen Friday. The 21.00z run of the MPAS
Ensemble shows a wide range of solutions ranging to a few
storms, a large line of storms, and no storms. Needless to say
more details need to be ironed on before Friday. Stay tuned.

This Weekend and Memorial Day...00z ensemble data continues to
show Saturday as a cooler and drier day across the CWA. Highs
in the 70s and lows in the 50s are forecast. The latter half of
the weekend and into the holiday is trending more active with
two main waves moving through. Will maintain the daily chance
PoPs through Monday night, but my confidence in each period
seeing rainfall is low and some dry hours should be seen. One
thing is for certain, it does not appear to be a hot and humid
Memorial Day.


&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1227 AM CDT Wed May 22 2024

MVFR cigs and gusty west winds near 30 kts will continue early
this AM in the CAA regime behind departing system. Expect
conditions to improve to VFR a few hours around sunrise at all
sites. Some additional gusts over 20 kts are forecast this
afternoon before decreasing again after 23z. A weak upper level
wave will track across Iowa this afternoon with only an increase
in clouds is expected at this time.

&&

.HYDROLOGY...
Issued at 1259 AM CDT Wed May 22 2024

Watch/Warning Changes Last Evening:

Upgraded the Iowa River at Marengo to Moderate flood and added the
Cedar River at Conesville in a Flood Watch. No changes to the Wapsi
and Skunk River.

Discussion:

Rainfall in the past 24 hours was highest in the Iowa and Skunk
river basins near their headwaters where radar estimates and
automated gauges reported 2 to 5 inches. The Cedar and Wapsi also
received 1.5 to 3 inches in the upper portions of the basins.
Because of this, the Iowa River at Marengo and the Skunk River near
Sigourney have the best chances of reaching Moderate Flood by the
end of the week. Will likely see some attenuation in the routed flow
upstream and expect some changes to the forecast in the coming days.
Elsewhere confidence is lower in reaching flood stage and Flood
Watches were continued.  The crest on the Wapsi and Cedar Rivers may
be delayed slightly in future forecasts.

&&

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

&&

$$

SHORT TERM...Gross
LONG TERM...Gross
AVIATION...Gross
HYDROLOGY...Gross