676
FXUS63 KDVN 261133
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
633 AM 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 /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 633 AM CDT Sun May 26 2024

Widespread showers with some embedded thunderstorms continue
across the area. It appears that the coverage of thunderstorms
is a bit lower than what many of the high-res models were
suggesting, which has helped to limit the MVFR to IFR
conditions. The ongoing precipitation will gradually come to an
end over the next 3 to 5 hours after TAF issuance, but models
are suggesting that ceilings will lower to MVFR/IFR this
morning, with some gradual improvement this afternoon. We are
likely not done with showers and storms though, as a front
sweeps through the area this afternoon and evening. Coverage of
this PM activity remains a bit uncertain, so we will use PROB30
groups to highlight the most likely timing. As the front moves
through, winds will quickly turn more northwesterly this
afternoon.

&&

.HYDROLOGY...
Issued at 850 PM CDT Sat May 25 2024

Flood Warnings continue for many of the tributaries in Eastern
Iowa for flooding ranging from minor to major. A Flood Warning
is in effect for the Mississippi River from Keithsburg
downstream to Burlington for minor flooding, while a Flood
Watch remains in effect for Gregory Landing for the potential
for minor flooding. Some locations will experience flooding for
the next several days and even to a week from now. Please refer
to the latest Flood Statements and Flood Warnings for details.

A storm system is expected to bring numerous showers and
thunderstorms to much of the area later tonight through Sunday
evening. Widespread 3/4 to 1 inch of rain is likely with some
spots possibly receiving around 1.50 inches in any stronger
storms. This may cause higher river levels than currently forecast
at some locations if this amount of rain materializes. After this
system passes off to our east by Sunday night no significant rain
is expected for much of next week.

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Schultz
HYDROLOGY...Haase