326
FXUS63 KDVN 151815
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
115 PM CDT Mon Jul 15 2024

.KEY MESSAGES...

- The heat continues for today and Monday with peak heat indices
  between 100 to 110 F. A Heat Advisory is in effect area-wide
  today until 8 PM but afternoon relief is possible north if
  storms arrive.

- An Enhanced Risk (Level 3 of 5) for severe storms across the
  outlook area. Damaging winds are the primary hazard, but
  tornadoes will also be possible today.

- Moderate to major river flooding continues on the Mississippi
  River with most sites crested. The Rock River is now expected
  to see flooding due to the heavy rains upstream in the past 24
  hours.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 316 AM CDT Mon Jul 15 2024

Today is another day to closely monitor forecasts and warnings!

Our area is set to be impacted by a damaging line of storms
this afternoon and evening, with an abundance of observational
and model data supporting the apex of a severe bowing line,
moving through eastern Iowa and northwest Illinois. SPC has our
area in Enhanced, level 3 of 5, today, focusing primarily on
damaging winds, but also noting a 5% tornado risk, and a low 2%
hail risk.

Today will be hot and humid, and while that will get handled by
an advisory today (though some values may reach warning criteria
in the south), the focus needs to be on severe weather during
the afternoon and evening. This heat will be the pool of energy,
CAPE we need to supply another round of severe storms. However,
this time, we`re dealing with a strong trigger (mid level jet
streak), focusing mechanism (front), and significant shear over
40 kts, and PWAT values over 2 inches and all those factors
really add up to a potential high end event.

The activity in eastern ND early today, will likely drop
southeast into MN, but could trigger a few elevated cells into
eastern Iowa and northern Illinois. Some CAMs do create a
separate event from this activity, but that seems unlikely.
Instead, it looks like air mass recovery will occur quickly
today, with winds becoming southeast and increase to 10 to 15
mph. This is especially true over northern areas, where the
mesohigh from last evening`s storms will be decaying.

I expect storms to fire in central Iowa by mid afternoon, and
will rapidly spread east and southeast. Damaging wind will be a
threat from the onset, but with the backed winds in eastern Iowa
and northern Illinois, STP values may exceed 2 in locations
north of Interstate 80, supporting supercells and tornadoes
during the afternoon and early evening.

By early evening, an established bowing storm segment should be
formed, moving east, with a comma head, and trailing line of
cells. This will lay out a swath of heavy rainfall and wind,
with guidance most supportive of this falling roughly along the
Interstate 80 corridor, then sinking south during the evening.

While the exact position is looking to go through our area, this
event will fall into line once we know the position of backed
winds and initial storms that trigger in central Iowa/northeast
Iowa today. Once they are, the axis of most significant storms
can be identified and communicated.

After 9 PM, the mode of storms looks to become primarily heavy
rain producing multicells storms, with the axis of heavy rain
gradually sinking south through the late evening and overnight.

Rainfall amounts of 1-2 inches will be common with this event,
with some amounts in the late evening training supporting and
additional 1" where training storms occur. Thus, this event
could again impact rivers, especially with any amounts over
northern Illinois, which is dealing with back to back heavy
rainfall events in the past 36 hours.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 316 AM CDT Mon Jul 15 2024

Cooler and less humid air will move into the region behind a
cold front by Tuesday and last through the end of the week.
Overnight lows in the 50s are forecast on several nights, giving
our air conditioning a bit of a break.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1252 PM CDT Mon Jul 15 2024

Main story continues to be on potential for severe storms late
this afternoon through this evening/early tonight. Scattered
storms will develop quickly by the late afternoon near or just
northwest of the area and then grow upscale into one or more
bowing segments. Severe wind gusts are the primary threat and a
few tornadoes are possible. Any storms will bring potential for
brief IFR/LIFR due to visibility reductions and low ceilings.
Mentioned thunderstorm potential in TEMPO groups, but there
remains uncertainty on the exact timing and on the severity of
the wind gusts. Later updates to TEMPOs will likely be needed.

&&

.HYDROLOGY...
Issued at 1111 AM CDT Mon Jul 15 2024

The broad crest on the Mississippi River from Gladstone, IL
(L/D 18) down through Gregory Landing, MO should be completed
within the next 12 to 24 hours.

A significant amount of water is working its way down the Rock
River. This water will slow down and may briefly stop the rate
of fall on the Mississippi River from Rock Island (L/D 15) down
through Gregory Landing for the remainder of the week. By next
weekend and into the following week, the Mississippi River from
Rock Island on downstream will begin falling again.

Tributary Rivers:

The lower Wapsipinicon River near Dewitt, IA will fall below
flood stage this afternoon. Water levels will remain high for
the next several days before they start falling again.

Backwater effects from the Mississippi River will keep the lower
Iowa River just below flood stage for the remainder of the week.

Based on water already in the Rock River basin and forecasted
rainfall over the next 24 hours, the entire length of the lower
Rock River will go into flood. The Joslin and Moline crest
forecasts have jumped into the major flood category based on
the predicted rainfall over the next 24 hours. If the rainfall
is less than expected, then the crest forecasts on the lower
Rock River would be lower.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Heat Advisory until 8 PM CDT this evening for IAZ040>042-
     051>054-063>068-076>078-087>089-098-099.
IL...Heat Advisory until 8 PM CDT this evening for ILZ001-002-007-
     009-015>018-024>026-034-035.
MO...Heat Advisory until 8 PM CDT this evening for MOZ009-010.

&&

$$

SHORT TERM...Ervin
LONG TERM...Ervin
AVIATION...Uttech
HYDROLOGY...08