257
FXUS63 KDVN 122341
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
641 PM CDT Sun May 12 2024

.KEY MESSAGES...

- Periods of showers and storms are likely Monday into Monday
  night with the heaviest rainfall amounts along and south of
  Interstate 80.

- Active weather will continue over the next 7 days as zonal
  flow remains in place across the CONUS.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 211 PM CDT Sun May 12 2024

A cold front sits to our northwest and stretches from Duluth to
Rochester to Sioux Falls South Dakota then west southwestward
into northeast Colorado. Temperatures at 2 PM ranged from 80
degrees Sterling Rock Falls to 85 degrees at Macomb. Scattered
showers and storms have developed across northern Iowa early
this afternoon. Stronger deep layer shear sits to the northeast
in Wisconsin at 30 to 40 knots with 1000 to 1500 J/KG of
surrface based CAPE to our north. These showers and storms are
forecast to sink slowly southeastward through this evening and
gradually dissipate. Model soundings show an inverted-V profile
and think that winds in storms gusting up to 40 to 50  MPH are
the main threat.

The cold front to our northwest is forecast to move into
northern Iowa by 12 UTC on Monday. CAMs show showers and storms
along the front sinking into the area this evening and gradually
dissipating before moving into our area.

A vertically stacked storm system is forecast o trudge from
central Nebraska and Kansas border tonight and into western
Illinois by 12 UTC on Tuesday. Moisture advection head of this
system will slowly saturate the atmosphere with the best lift
and moisture spreading into far northeast Missouri and southeast
Iowa by 12 UTC on Monday and slowly spread northeastward
through the day. This will bring periods of rain showers and
storms through the period. Models show 1.25 to 1.50 inches of
precipitable water through the day on Monday into Monday night
which is 100 to 150 percent of normal. Heavy rain will be
possible as this storm system moves across the area especially
south of Interstate 80. Rainfall amounts will range from up to
0.5 inches north of Interstate 80 to up to an inch south with
isolated higher amounts.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 211 PM CDT Sun May 12 2024

A split zonal flow is forecast to be in place across the CONUS
through the long term period. This will result in a series of
troughs and ridges moving across the area through next weekend.
Models begin to diverge later in the week on the timing and
placement of different features.

Tuesday: Shower chances will continue at least through the morning
hours as the vertically stacked system tracks across central and
southern Illinois. Otherwise, we`ll have breezy NE winds and
seasonable temps in the upper 60s to low 70s.

Wednesday - Saturday: Ridging aloft and surface high pressure is
forecast to build in later Tuesday into Wednesday, leading to a
break in the wet weather. The next system to impact the region
arrives by late Wednesday into Thursday, bringing another round of
widespread rain to the outlook area. Once again there is uncertainty
on how quickly this system pushes to our east. The NBM has a chance
for rain (30-40%) continuing through Friday which is reasonable
given the model discrepancies. Forecast temperatures late in the
week are near to slightly above normal.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 622 PM CDT Sun May 12 2024

Outside of thunderstorms, expect VFR conditions through late
Monday AM before MVFR overspreads the area from the SW. Expect
isolated rain showers through the next 12 hours before they
become more widespread. Better chance for thunder is later in
the period.


&&

.HYDROLOGY...
Issued at 211 PM CDT Sun May 12 2024

The latest update on the local rivers from this morning indicate the
observed river level for the Wapsipinicon River near DeWitt is
rising faster than the previous forecast had indicated, and an
adjustment was made to the forecast river level to now suggest minor
flooding there beginning tonight around 1 AM tonight. We have
continued the Flood Warning for this area given the faster rate of
river rise.

The forecasts for the Cedar and Iowa Rivers continue to be marginal
for reaching minor flooding at Conesville and Marengo, respectively.
Both forecasts have each river just touching the minor flood stage,
so confidence remains low on if they will reach this level or not.
With that said, we will continue the Flood Watches.

As we look forward to tonight, we will begin to ingest more of the
forecast rainfall/QPF for the Monday into Monday night period, so
expect some adjustments to these forecasts. The latest HREF
probability-matched mean QPF values through Tuesday morning are
progging a swath of rainfall in excess of one inch, with some
isolated amounts over two inches, and the swath of heaviest rainfall
has shifted slightly northward closer to the areas impacted by this
river flooding.

&&

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

&&

$$

SHORT TERM...Cousins
LONG TERM...Cousins/Uttech
AVIATION...Gibbs
HYDROLOGY...Schultz