772
FXUS63 KDVN 252031
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
331 PM CDT Tue Jun 25 2024

.KEY MESSAGES...

- Heat indices upper 90s to 100+ through early this evening

- Storms likely to develop by evening and increase in coverage
  with a flash flood threat and scattered severe potential

- More storms Thursday Night through Saturday

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 320 PM CDT Tue Jun 25 2024

Through early evening: Hot and humid conditions continue with
heat indices in the upper 90s to as high as 105, as dewpoints
remain well into the 70s. Mesoanalysis indicates a weak slow-
moving frontal boundary that extended from far southern WI to
near Dubuque to Omaha. Confluence along this is largely weak but
SBCAPES were 4500-6000 J/kg and deep player shear was about
30-40 kts. However, the special DVN sounding at 18z/25 showed a
rather stout cap at 850 mb suppressing convection for now.
Closer to the front, there may be enough confluence, along with
plenty of available energy, to develop at least isolated
thunderstorms through early evening. The experimental Warn on
Forecast System (WoFS) indicates this potential for isolated
activity closer to the front. Heavy rainfall and wet microbursts
are the main hazards.

This evening through the overnight hours ~8 pm to 2 am looks to be
the main coverage of numerous thunderstorms, especially along and
south of Interstate 80. A flash flood watch is in effect for
this entire region. A weak short wave arrives from the west
which should enhance the forcing, along with the frontal
boundary continuing to push south across the forecast area.
There is the potential for severe storms and scattered flash
flooding. With PWATs over 2 inches and dewpoints well into the
70s there may be several inches of rain in a short time. The
12z/25 HREF indicated some localized amounts within the
general southern CWA and adjacent area region of 3+ inches,
supporting that potential for heavy rainfall rates (albeit low
confidence on specifically where and may be outside the CWA).
Lows tonight will still be mild from the upper 60s to lower 70s.

Wednesday: Any lingering showers and storms should end in our
southeast counties in the morning. Otherwise, with the passage of
the front, temperatures and humidity levels will lower so some
relief from the heat. Highs will be in the lower to mid 80s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
Issued at 320 PM CDT Tue Jun 25 2024

Wednesday night and Thursday: Dry and very pleasant with highs in
the upper 70s to lower 80s, and lows in the upper 50s to lower 60s.
High pressure will push across the Great Lakes region.

Thursday night through early next week: Global models suggest a
rather strong zonal flow across the northern United States,
suppressing the hot weather well to our south. In this pattern a
couple of low pressure systems will track across the northern Plains
and upper Midwest. The potential for more thunderstorms and heavy
rainfall returns Thursday night through Saturday, and again Monday
into Tuesday. While it is too early to determine the severe
threat or rain amounts, it should be noted the CSU machine-
learning probabilities do indicate an equivalent for a Slight
Risk for severe weather on Friday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1246 PM CDT Tue Jun 25 2024

Numerous showers and scattered thunderstorms are expected to
develop late this afternoon through tonight, mainly south of
Highway 30. CAM`s indicates a line of storms later tonight south
of I-80. For now kept the prob30 but as the storms evolve and
confidence increases then will have to amend to go prevailing. A
slow moving cold front will drop southward through tonight with
winds becoming northwest to north behind the front.

&&

.HYDROLOGY...
Issued at 320 PM CDT Tue Jun 25 2024

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.  The entire stretch of the
Mississippi River, excluding Keokuk and Gregory Landing, is now in a
River Flood Warning.

On the Cedar River, we expect to see some crests upstream tonight.
The forecasts for Vinton and Palo are tracking well with upstream
forecasts, thus leading to the flood warnings being issued today.
Further south, there is less confidence in crests and thus watches
remain in effect.  The overnight crests should help with the rest of
the Cedar forecast.  Warnings for additional sites and refined crest
forecasts are possible these evening or Wednesday morning.

All this said, we expect additional rainfall later in the week. This
is not included in the current forecast.  This rainfall is expected
to fall near the crest on the Cedar.  As such, expect changes to the
crest forecasts later this week based on forecast QPF.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Flood Watch through Wednesday morning for IAZ063>065-067-068-
     076>078-087>089-098-099.
IL...Flood Watch through Wednesday morning for ILZ015>018-024>026-
     034-035.
MO...Flood Watch through Wednesday morning for MOZ009-010.

&&

$$

SHORT TERM...Haase/Friedlein
LONG TERM...Haase
AVIATION...Haase
HYDROLOGY...Gibbs