105
FXUS63 KDVN 242341
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
641 PM CDT Mon Jun 24 2024

...Updated for 00z Aviation...

.KEY MESSAGES...

- Active next 36 hours with thunderstorms, some strong to severe
  and heavy rain expected.

- Actual evolution of storms and timing is uncertain and falls
  into 3 different scenarios explained below.

- Quiet conditions expected Wednesday and Thursday before
  another round of storms moves in for Friday and Saturday

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 1236 PM CDT Mon Jun 24 2024

Active period expected as hot and humid air will serve as the energy
for strong to severe thunderstorms through the short term.  A couple
different scenarios are possible with the storms in the next 6 to 30
hours.  Questions about storm mode and evolution and thus threats
abound at the time of this issuance, however a few things are known.
First, there is a warm front draped from Bismarck, ND southeast to
Dubuque. Also, the largescale flow is curved back to the SE and into
our area as well.  These two knowns suggest that convection to our
north in the next 6 to 30 hours will dive south and into our area.
The better chance for severe storms will likely be in the next 6 to
24 hours, before we transition to more of a flash flood threat.

Scenario 1: A MCV across Minnesota is expected to continue moving
southeast towards the the CWA this afternoon into the early evening.
Storms could redeveloped near this MCV. With an extremely
unstable warm sector, and deep layer shear of 30 to 40kts storms
should continue to build. If they do redevelop, expect storms
to become cold pool dominant as a severe MCS barrels south
towards us in the early evening. With current environment, would
not be surprised to see widespread 70 MPH gusts with some
embedded higher gusts. This one is the least likely to occur,
however if it does, it will likely lead to the most severe
weather.

Scenario 2: Thunderstorms redevelop this afternoon across
western MN. Supercells initially will turn into a MCSs with a
strong cold pool. This system will track south and east towards
our area later this evening and into the overnight. How far west
this activity is will be tied to the left over cloud cover over
MN and the CAP to our SW. Do believe that this system will
track further SW and more into our CWA if this occurs. This
would bring severe winds to the area later in the overnight. As
these storms move out of the area, some OFBs would be left.
Storms would redevelop then in the late afternoon and into the
evening on Tuesday. While initial storms could lead to severe
winds, this will turn quickly into a slow moving storm
environment and flash flooding will be likely.

Scenario 3: No storms develop until Tuesday.  While this seems to be
the less likely solution, it is still plausible.  In this case, a
cold front tied to convection across WI and eastern IL, will stall
across the area.  Daytime heating, along with the boundary will lead
to showers and storms forming. Deep layer shear is lower, so strong
to severe storms will be short lived before transitioning to a heavy
rain and flash flooding threat.  Right now, this threat is maximized
along and south of I80.  That could change though.

Regardless of what happens, we expect impactful weather through the
next 36 hours.

As far as heat goes, with thunderstorm potential through the
period, high temperature forecast will be tricky. Tomorrow has a
high bust potential. As such, will hold off on any heat advisory
at this time.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 206 PM CDT Mon Jun 24 2024

Active pattern is expected to continue through the rest of the
long term. While there appears to be a break in showers and
storms Wednesday and Thursday,it does not look like a completely
dry forecast. We remain aligned in the track for ridge riders.
Any of these could produce showers and storms. Late in the week,
another more robust system is expected to affect the area. This
will bring what appears to be a MCS into the area Friday
morning. While there could be strong to severe storms, what does
seem more likely is the chance for heavy rain. This will just
add to the flooding across the area.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 635 PM CDT Mon Jun 24 2024

Location of 850/700 mb thermal gradients, and west to east
instability gradient across the region is favorable for the
propagation and development of storms into the region tonight
into Tuesday morning. However, the timing/location remain quite
uncertain and will be dependent on just how organized storms
become upstream into portions of Minnesota and Wisconsin. As a
result, this precludes from going any higher than PROB30 mention
at most sites late tonight into Tuesday morning. Will continue
to monitor upstream convection trends this evening and update
should more favored corridors/location and timing become more
apparent. In the very near term, the general indication is that
convection into SW Wisconsin will continue east-southeast and
pass mainly east of the terminals through this evening. But,
will need to watch for any backbuilding toward DBQ terminal.
Also, watching for potential development in south central
Minnesota. Should this occur in the next few hours, then the
potential for storms to impact the terminals would increase and
arrive sooner than mentioned. Otherwise, any residual boundaries
and an approaching cold front may lead to additional storms
developing Tuesday PM/evening. However, too much uncertainty on
location/timing for any mention at this time as this potential
will be largely tied to what occurs overnight and Tuesday AM.

Conditions in any storms will be MVFR to IFR, but outside of
storms are expected to remain VFR. Winds will be gusty at times
tonight into Tuesday AM to around 20 kts. Have kept mention of
LLWS overnight through mid morning Tuesday with a strengthening
nocturnal LLJ to 50 kt around 2kft agl.

&&

.HYDROLOGY...
Issued at 929 PM CDT Sun Jun 23 2024

No significant changes for the Cedar River basin this evening
with the new forecasts. The rise on the Cedar River at Cedar
Rapids has been slowed some and still may reach 14 ft or
Moderate flood stage early Friday.

For the Mississippi, flood watches have been converted to flood
warnings for Dubuque Lock and Dam, Camanche, and Rock Island
Lock and Dam sites this evening. Additional warnings can be
expected in the coming days.

.Previous Discussion.

The Mississippi River is expected to reach flood stage at
multiple locations, including the Rock Island gage, by the
middle of this week. Long term we expect the Mississippi to
reach Moderate and/or Major flood stages the week of the Fourth
of July, with the crest at the Rock Island gage possibly
reaching just over 18 feet early on the Fourth of July.
However, a larger margin of error should be taken into
consideration when forecasting precipitation amounts and
locations in the 7-10 day timescale. Watches are currently out
for most of the Mississippi River and warnings will follow in
the next few as a clearer picture is drawn on what
precipitation and routed water we have coming downstream. In the
latest forecast package, we have opted to upgrade Gladstone and
Burlington to a River Flood Warning, aided by the recent
rainfall north of the area.

The Rock River is also expected to reach flood stage in Joslin,
with an increase noted into Action Stage at Moline. A River Flood
Warning has been issued for Joslin in this latest forecast
package, which is forecast to hit flood stage tomorrow
afternoon. We will continue to see additional rainfall through
this coming week, which may lead to further fluctuations in the
river levels. If heavy rainfall is seen, then increases can be
expected.

&&

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

&&

$$

SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...McClure
HYDROLOGY...Gross