828
FXUS63 KDVN 261738
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1238 PM CDT Sun May 26 2024

.KEY MESSAGES...

- Active weather today, with widespread showers and thunderstorms
  early this morning

- We should largely dry out by this afternoon, but can`t rule
  out isolated to scattered strong to severe storms across our
  north and east

- A change in the flow pattern aloft is expected to bring a period
  of quiet weather for much of the coming week

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 231 AM CDT Sun May 26 2024

Convection is beginning to ramp up across central Iowa as of 2 AM
this morning, ahead of an approaching mid-level shortwave that will
translate across the area this morning. Ahead of the shortwave is a
prominent 45 to 55 kt low-level jet, as evidenced on the DSM and MLI
VAD wind profiler data. Most-unstable CAPE values of around 500 to
1500 J/kg per the HREF ensemble mean and steep mid-level lapse rates
should support the threat for large hail. Soundings indicate a low-
level thermal inversion, so this convection should become more
elevated, so locally strong winds will be secondary threat, but
can`t rule it out entirely with the LLJ and deep-layer shear of
around 30 to 40 knots. We are pretty confident in this convection
ramping up and moving from west to east this morning. More heavy
rainfall is possible with this morning`s activity, given Pwat values
around 1.3 to 1.6. IVT per the ENS ensembles are over 97 percent of
climatology by 7 AM this morning, so water vapor transport will be
supportive of heavy rainfall. NBM probabilities of 1" of rain for
today`s precipitation are around 50 to 70 percent for a large
portion of the region, so ongoing river flooding will only be
exacerbated with this rainfall.

Confidence in showers and storms this afternoon is a bit more
uncertain, as the mid-level shortwave trough and the attendant
surface low crosses the area. There remains some uncertainty on the
track of the low, with the GEFS and ENS ensemble low tracks showing
some slightly different paths, with the GEFS tracks just to the
south of the region, while the ENS paths are more right on top of
us. The LLJ will have shunted off to the northeast, so flow will be
relatively weak, but with higher dew point air lifting northward
today and surface-based CAPE on the order of 1000 to 2000 J/kg, we
can`t rule out more thunderstorms this afternoon, some of which
could be strong to severe, too. The main warm frontal boundary and
instability gradient appears to remain to our south, and the CAMs
depict a strong signal for severe convection down that way, but a
secondary mid-level shortwave appears to graze our northern and
eastern areas, so we will need to keep an eye on at least some
isolated to scattered severe storms this afternoon.

The bulk of the large-scale forcing will move off to the east after
sunset through tonight, with the departure of the mid-level
shortwave trough. We have a dry forecast for this evening, save for
any lingering showers and storms from the afternoon`s convection.
Otherwise, we should have a quiet night, with lows in the 50s.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 231 AM CDT Sun May 26 2024

The long-term period will start off Monday with yet another chance
of showers and an isolated storm moving in from the northwest ahead
of an approaching mid-level shortwave that will dive southeast from
the Dakotas. Mixed-layer CAPE appears to be pretty meager, with
values progged around 500 to 1000 J/kg, so some thunderstorms can`t
be ruled out, but with dew points only in the 50s, severe weather is
not expected. We will have another brief bout of rain chances on
Tuesday as yet another mid-level shortwave dives southeast over the
region.

For Wednesday through Friday, we are looking at something we haven`t
had in a while: an extended stretch of dry and quiet conditions!
Guidance is progging a long-wave ridge over the western CONUS and a
surface high pressure settling across the western Great Lakes region
for much of next week. Temperatures look to be seasonal, with highs
in the 70s for most locations, and lows in the 50s.

Another chance of showers and storms might move in for Saturday, but
there are some timing differences among the guidance at this time.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1232 PM CDT Sun May 26 2024

Some isolated to possibly scattered SHRA/TSRA may occur through
02z/27 across eastern Iowa and northern Illinois. However the
probability of a TAF site being impacted is 10 percent at best.
Otherwise IFR/MVFR conditions will slowly improve to VFR through
03z/27 from southwest to northeast. After 03z/27 expect VFR
conditions as high pressure builds into the Midwest. After
18z/27 and upper level disturbance is expected to generate
isolated to scattered SHRA/TSRA.

&&

.HYDROLOGY...
Issued at 1232 PM CDT Sun May 26 2024

Swaths of 1-2 inches of rain occurred overnight and early this
morning in the headwaters and portions of the channels of the
Wapsipinicon, Cedar and Iowa River basins. This will prolong
high water levels and minor to major flooding on these rivers
from the main channels to the confluence of the Cedar and Iowa
Rivers, and Iowa and Wapsipinicon Rivers with the Mississippi
River. This routed water will also lead to further rises on the
mainstem Mississippi River, with many locations nearing action
stage through midweek from Dubuque (DBQI4) down through Muscatine
(MUSI4) while minor flooding is expected in many locations from
Keithsburg (KHBI4) to Gregory Landing (GGYM7). Please refer to
the latest Flood Statements and Flood Warnings for more details.

The forecast will have chances for sporadic rains over the next
couple of days, but significant rainfall is not expected.
Beyond, it looks to turn more active heading into the first
week of June. The Climate Prediction Center has the area favored
for near normal rainfall June 2-8.

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...08
HYDROLOGY...McClure