948
FXUS63 KDVN 111046
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
546 AM CDT Thu Jul 11 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms today, although low
  confidence in coverage and timing. Slow movement will bring
  risk of flash flooding with training storms.

- Becoming very warm and humid this weekend and into next week,
  with heat indices in the upper 90s and low 100s. Heat
  headlines may eventually be needed Sunday and Monday.

- Ring of fire pattern early next week may bring strong/severe
  thunderstorms close to the forecast area and relief from the
  heat.

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

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 320 AM CDT Thu Jul 11 2024

Scattered showers and isolated thunderstorms have been ongoing
for much of the night north of I-80. This was due to the
pivoting upper low overhead that was centered over Johnson
county at 3am. Due to the slow movement of storms, some
impressive rain amounts over 1.5" in 1 hr or 2" in 3 hrs based
on spotters and radar estimates were reported. A flash flood
warning was issued for northern portions of Linn and Benton
counties early this AM for these totals. In addition to the
storms, patchy areas of fog with visibilities under a mile have
developed mainly south of I-80 where clouds have cleared. Some
localized dense fog was also observed outside our office here at
DVN. 00z models and CAMs have performed poorly this morning and
have relied on nowcasting, particularly with storm placement.

Early This Morning...areas of fog will continue to expand
through 6am, with visibilities under a mile at times. Some
localized dense fog may occur so motorists should use caution
and use low beams if they encounter dense fog. Visibilities will
quickly improve after 7am.

Today...upper low to track across the area this morning, with
additional showers and storms expected through the afternoon
hours. The activity early this AM was occurring in the
700-500mb mean RH gradient per SPC Mesoanalysis. Based on this
and the latest CAMs that have started to catch on to what
actually is occurring, the highest coverage this afternoon would
be in west central and north central IL and this is where
chance PoPs were added. With high PWs still in the 1.3-1.5"
range and slow storm motions under 15 mph, another quick 1-2"
rain may occur in very narrow swaths. Some localized 3" amounts
not out of the question as well. Rain rates between
0.75"-1.5"/hr can be expected in the strongest cells. Deep layer
shear values less than 20 kts will preclude any severe
potential, although NST values over 1 across west central IL may
allow for funnels to occur this afternoon. Highs today were
lowered some and will a degree or two cooler than yesterday,
with highs topping out in the lower 80s.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 320 AM CDT Thu Jul 11 2024

Friday...strong upper level ridge begins to dampen some across
the western CONUS, but keeps us in northwest flow aloft.
Depending on which model you look at, there will be several
waves that top this ridge and move into the northern Great
Plains. The 1st one of interest would arrive as early as Friday
night if the 00z NAM is correct. Moisture will be lacking and
have maintained a dry forecast for now on Friday.

This Weekend...more upper level waves will move through the
flow in a "ring of fire" like pattern. Models still in
disagreement timing these waves and any associated impact (MCS
track?) to the CWA. The 00z models keep the main wave well to
our north across MN/WI on Sunday and thus a dry forecast for our
area. However, building heat will be seen with 850mb temps
rising into the 23-26C range. This will boost temps into the 90s
and combined with dewpoints in the low 70s (perhaps even higher
due to mature corn crop), will push afternoon heat indices into
the upper 90s and low 100s, especially on Sunday. The warmest
readings will be seen south of I-80 in the afternoon and a heat
headline may be needed.

Early Next Week...after another very warm and humid day Monday
with possible heat headlines, a cold front will move through
late Monday night into Tuesday. This will likely bring some
strong storms to our area and relief from the heat. This will be
something to monitor in later forecasts. Beyond Tuesday,
temperatures will be cooler with highs only in the low to mid
80s.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 535 AM CDT Thu Jul 11 2024

Shallow ground fog to impact BRL/MLI through 13z this morning
with LIFR vsbys at BRL. An upper level wave will continue to
push east into northern IL today, with scattered
showers/isolated thunderstorms developing late
morning/afternoon. Hi-res models suggest this to occur right
over MLI by midday and have included VCTS wording for now.
Confidence is too low to include thunder mention at BRL. Light
winds to turn easterly this afternoon and then go calm
overnight tonight with clearing skies. Some MVFR fog is
possible late in the period and have included mention.


&&

.HYDROLOGY...
Issued at 124 PM CDT Mon Jul 8 2024

Precipitation in the next few days, especially in Iowa, is expected
to be dry or very light. Thus, routed flow will continue on all of
our rivers.

The Mississippi River is currently cresting at major levels upstream
of Camanche, IA, and near crest through Illinois City.  The crest
may take 1 to as much as 3 days to pass. From Le Claire to
Burlington, the respective crests will commence within the next 1 to
2 days.

Keokuk is now forecast to crest within Moderate Flood category
beginning Friday.  Gregory Landing is forecast to remain near 19.5
feet through the week.

Tributary Rivers:


The Cedar River at Cedar Rapids crested below flood stage and will
fall over the next several days.

On the Cedar River at Conesville, minor flooding will continue. It
will see a secondary crest near 14.4 feet Wednesday night into
Thursday.

The Wapsipinicon River at Dewitt is forecast to remain in
moderate flooding category through late on Friday.

The Iowa River at Oakville is seeing high water levels due to
backwater affects from the Mississippi River. It is forecast to
remain near 11.4 or 11.5 feet through midweek and then rise to near
12.1 feet late Thursday into Friday.

&&

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

&&

$$

SHORT TERM...Gross
LONG TERM...Gross
AVIATION...Gross
HYDROLOGY...Gunkel