Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 122343

Area Forecast Discussion
National Weather Service Quad Cities IA IL
643 PM CDT Fri Jul 12 2024


- Isolated to scattered showers and thunderstorms are possible
  overnight into Saturday morning, and again Saturday night.

- Becoming hot and humid this weekend and into early next week,
  with heat indices in the upper 90s and low 100s. Heat
  headlines have been issued in the south for tomorrow
  afternoon, and will likely eventually be needed for Sunday and
  Monday for portions of the area as well.

- Ring of fire pattern second half of the weekend into early
  next week may bring strong/severe thunderstorms close to the
  forecast area and temporary relief from the heat. Then there
  will be longer lasting relief in the form a significant cold
  front by mid week.

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


Issued at 251 PM CDT Fri Jul 12 2024

Tonight...Southeasterly return flow continues to west of GRT LKS sfc
ridge, with higher sfc DPT fields noted off to the west and south of
the area ready to slosh this way through tomorrow. The latest sfc
analysis and MSAS were indicating a west-to-east oriented quasi-
stationary boundary acrs northern KS and northern MO, which will
look to trend into a retreating warm front with increasing southerly
flow push later tonight and especially Saturday. A low chance for an
isolated pop-up shower or storm in initial somewhat elevated WAA
push in the cumulus field along and south of the CWA this evening.
For now will keep silent POPs for this, and focus on the elevated
warm air advection(WAA) wing later tonight after midnight for
isolated to wdly sctrd showers and storms. Enough mid layer MUCAPEs
of 1500-2500 J/kg and lapse rates of 6.5+ C/km to maybe support an
isolated stronger elevated storm capable of hail. Any activity that
may develop should then linger into Sat morning. Southeasterly sfc
winds and increasing DPTS will make for milder overnight lows in the
mid 60s inn the northeast, to the lower 70s southwest.

Saturday...The warm front will try to retreat through the CWA, with
enhancing EML behind it. Will carry low CHC POPs for most of the day
for the chance for an isolated storm developing either sfc based
near the front or elevated again anywhere. Of course if something
would be able to get sfc rooted, there would be a severe threat.
Locally heavy rain also a factor. With high temps in the lower 90s
and sfc DPTs pooling in the low to mid 70s, heat index values of 100
to 103+ degrees are being fcst now in the southwest third of the DVN
CWA Sat afternoon into early evening, and have issued a Heat
Advisory for those areas. A quicker sfc front retreat may warrant a
further north expansion of the headline if the next shift
or two deems it worthy.


Issued at 251 PM CDT Fri Jul 12 2024

Saturday Night...Broad west-northwesterlies acrs the upper Midwest
and an embedded short wave or MCV feature will look to ignite a heat
dome-riding MCS acrs the eastern Dakotas, MN or into WI. Thermal
thicknesses or gradient profiles such as H85 MB 18-21C angle from SD
to northern IL/southern LK MI which could be the track of any mature
or organizing MCS into Sunday morning. It could just miss our CWA to
the northeast, but LLJ feed may allow it to back build into the
northeast and eastern fcst area by Sunday morning. Damaging winds
and heavy rainfall would be a threat from any mature piece of this
complex making down into the area, if it can battle a probable EML
and get sfc rooted with a cold pool. Besides this potential, there
may be sctrd secondary elevated showers/storms further to the south
acrs IA into IL feeding on southwesterly 20-30 KT LLJ feed. Will
continue to massage POPs to account for all this. Overnight lows
holding up in the 70s.

Sunday...As long as convective debris or storm outflow boundaries
don`t interfere, this day still shaping up to be a mid 90s ambient
temps with sfc DPTs in the low to mid 70s making for Heat index
readings in the 100-15+ range and the eventual need of a heat
advisory. Latest medium range model/ensemble trends now adjust the
more ideal storm track thermal ribbon to the north with EML capping
to the south acrs our area Sunday night. Thus we could be largely
dry with the flattened flow to the north and in-between short waves,
as opposed to another late night/nocturnal MCS.

Monday and Tuesday...Monday looking like another heat advisory day
especially if we have a lack of local convective activity out of
Sunday night. Some signs of a more vigorous short wave and steering
flow buckle from the north that may allow a better chance for either
storms to move in from the northwest late Monday afternoon and
night, or possible develop over head. In either case enough buoyant
energy to fuel strong to severe storms and heavy rain if they do
indeed manage to make into the fcst area. This buckling or
amplifying northwest flow to be the start of an air mass regime
change that sweeps a significant cool front down through the region
from the north on Tuesday, which may fire more storms along this
FROPA process on Tuesday. High temps a challenge this day depending
on FROPA timing, cloud cover and precip chances.

Wednesday and Thursday...With the cold frontal passage looking to
occur now on Tuesday, while storms re-fire along to southward
pushing boundary to the south of the area, we may be under the
influence of cooling northerly flow now on Wednesday. Still some
chance of over-running showers in the south, and maybe afternoon
instability isolated shower development further to the north under
lingering cyclonic flow aloft. But overall this will be the
beginning of a cooler, dry and less humid weather regime as Canadian
high pressure is allowed to dump down the upper to mid MS RVR Valley
and western GRT LKS. High temps in the 70s to low 80s with scoured
out humidity(besides corn evapo-transpiration input) look on tap for
the late week period.


Issued at 631 PM CDT Fri Jul 12 2024

High pressure is forecast to shift farther to the east through
the TAF period which will result in VFR conditions through the
period. Winds will turn to the south after 12 UTC Saturday with
a few gusts up to 20 knots after 18 UTC. Scattered showers and
thunderstorms are possible after 09 UTC but confidence is low
on the timing and placement.


Issued at 1043 AM CDT Fri Jul 12 2024

The crest on the Mississippi River is between New Boston, IL
(L/D 17) and Keithsburg, IL. Areas upstream of New Boston
through the Quad Cities are coming off a a broad crest. From
Keithsburg, IL downstream to Gregory Landing, MO a broad crest
will commence over the next 0.5 to 1.5 days.

Tributary Rivers:

On the lower Cedar River near Conesville, IA, minor flooding
continues as water levels continue to fall.

The lower Wapsipinicon River near Dewitt, IA will remain in
moderate flood through Saturday. A fairly rapid drop in water
levels will commence Saturday 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. Once the broad crest
on the Mississippi gets downstream of Keithsburg, IL, water
levels on the lower Iowa River will slowly begin to fall.


IA...Heat Advisory from 1 PM to 8 PM CDT Saturday for IAZ076>078-
IL...Heat Advisory from 1 PM to 8 PM CDT Saturday for ILZ025-026-
MO...Heat Advisory from 1 PM to 8 PM CDT Saturday for MOZ009-010.