469
FXUS63 KDVN 131801
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
101 PM CDT Sat Jul 13 2024

.KEY MESSAGES...

- The Heat Advisory for today was expanded to the north to
  include counties roughly along the I-80 corridor; peak heat
  indices of 100 to 105 F are expected and the advisory is in
  effect until 8 PM.

- The heat continues for Sunday and Monday with peak heat
  indices between 100 to 110 degrees.

- Organized thunderstorms are possible late today and/or tonight,
  with an MCS moving southeast/south. This could bring gusty
  winds, and heavy rainfall. The next chance for organized
  storms is focused on Monday night`s cold frontal passage.

- Moderate to major river flooding continues on the Mississippi
  River with most sites crested or cresting in the coming days.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 222 AM CDT Sat Jul 13 2024

Light winds, temperatures in the lower 70s, and dewpoints rising to
the upper 60s to lower 70s are found across the area early today,
substantially warmer than yesterday at this time. Mid clouds are
noted on satellite over our area, but as of 2 AM, no showers have
developed in this mid level WAA regime. We`ll watch conditions, but
for now, the chances for morning storms remains under 20%.

Today will focus on the building heat and humidity, but all eyes
will be focused north of our area, as we watch southeastward moving
convection in the Dakotas and Minnesota. There are two scenarios
playing out today.  One, the heat builds in, and so does the EML,
resulting in hot, dry conditions through Monday. This is roughly 1/2
of available guidance.   The other, which at the moment is supported
by satellite/radar, shows several convective clusters moving
southeast towards northern Illinois by this evening. This would
generally arrive in our CWA after 7 PM, but could bring a wind gust
threat to our northern counties.  During the evening and overnight,
as a LLJ is aimed directly at our area, around 35 to 45 kts, the
cold pool could slowly propagate southwestward, resulting in a heavy
rain swath over our northern 1/2 of the CWA.  WPC and SPC are both
on board with this second scenario, which is supported by the
northwest flow aloft, diffluent thickness over our area, and LLJ
position.  It`s important to realize, that we often get a
significant convective event as significant heat waves build in, so
this potential should be no surprise.  Cells would continue to move
quickly during the overnight activity southeastward, but the
convective axis of storms would slowly shift southward, thus a
period of training is expected as the line slowly drops south.

Sunday, after any storms move out early, it appears the heat will be
in place through Monday, with only very low chances for thunder in
the far north.  Highs in the upper 80s to lower 90s are forecast,
with dewpoints in the lower to mid 70s. Heat indices both days
are forecast in the 97 to 104 range. Both Sunday and Monday,
850mb temperatures are forecast to be 24 to 27C, which is
strongly supportive of excessive heat.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Issued at 222 AM CDT Sat Jul 13 2024

Monday night, the cold front will move into our area, with storms
possible along it, and just post frontal. Models continue to show a
strong EML, but the frontal position could serve to erode that with
time, especially after dark. The ample CAPE over 3000 J/KG would
support strong storms, as would the increasing shear from the
westerly flow aloft.  For now, pops are in the 30-50% range Monday
night, due to the potential of the EML holding back storm
formation.


Tuesday is a transition day into the far cooler air in the
extended. Highs will be rather warm, but with decreasing
humidity and gusty winds, the heat stress will be decreasing
through the day.

Wednesday though Saturday continue to look very pleasant, with highs
in the 70s to low 80s, and lows in the 50s!

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1255 PM CDT Sat Jul 13 2024

Expect VFR to prevail this afternoon and evening with steady S
to SSW winds between 10 - 20 kts. There is a chance for
scattered showers and storms later this afternoon through
tonight which could lead to brief MVFR/IFR. Confidence is very
low on the coverage and timing, so left thunder out of the TAFs
for now.

&&

.HYDROLOGY...
Issued at 938 AM CDT Sat Jul 13 2024

The crest on the Mississippi River is now between Keithsburg,
IL and Gladstone, IL (L/D 18). Upstream of New Boston (L/D 17)
river levels continue to fall. New Boston and Keithsburg are
just starting to show signs of falling. As the broad crest
continues to attenuate, areas from Gladstone downstream to
Gregory Landing should begin a very broad crest over the next
day or two.

Tributary Rivers:

On the lower Cedar River near Conesville, IA, minor flooding
continues. Over the next 24 to 36 hours the flooding is forecast
to end.

The lower Wapsipinicon River near Dewitt, IA will remain in
moderate flood through mid-day Sunday before falling into minor
flood. A fairly rapid drop in water levels will commence Sunday
afternoon and night as backwater effects from the Mississippi
River decrease.

Minor flooding continues on the lower Iowa River at Oakville due
to backwater effects from the Mississippi. With the broad crest
on the Mississippi now just south of Keithsburg, IL, water
levels on the lower Iowa River will slowly fall to and then
remain around flood stage over the next four days.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Heat Advisory until 8 PM CDT this evening for IAZ063>065-067-
     068-076>078-087>089-098-099.
IL...Heat Advisory until 8 PM CDT this evening for ILZ015-016-
     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