Most Recent Area Forecast Discussion (2024)

Area Forecast Discussion
National Weather Service Quad Cities IA IL
639 PM CDT Wed Jul 3 2024

.KEY MESSAGES...

- Showers and thunderstorms are possible on Independence Day as
a warm front lifts north through the area followed by a cold
front. There is a Slight Risk for severe storms for the far NW
CWA with a Marginal Risk for most of the remainder of the CWA.

- A rather active pattern still looks to be on tap through the longer
range, with near daily chances for precipitation somewhere in
or near our forecast area. Saturday may be the best chance at
a dry day, with slight-chance PoPs daily from there.

- Moderate to Major River Flooding continues, with further
changes to river forecasts expected as we transition from
predicted rainfall to observed rainfall over the next 36 hrs.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 250 PM CDT Wed Jul 3 2024

Tonight, dry conditions will prevail as high pressure drifts east
and a low approaches from the plains lifting a boundary into the
southern CWA. Slight POPs are in the southern part of the CWA for
the overnight with chance POPs towards daybreak. Winds will be
nearly calm and with any partial clearing, can`t rule out some
patchy fog, but opted not to mention in grids. Lows will be in the
mid 60s to near 70.

On the Fourth, unfortunately, we will have to deal with chances of
scattered showers and thunderstorms. Some of which could be strong
to severe, as a low develops over southern MN with a cold front pushing
into the western CWA during the late PM and evening. SPC has a Slight
(level 2 of 5) Risk for primarily damaging winds and large hail for
Buchanan and Delaware counties, with a Marginal Risk (1 of 5) for
much of the rest of the CWA. Dew points will rise back into the upper
60s and lower 70s. With some partial sun, temperatures will rise
into the low to mid 80s. MLCAPE will climb into the 1000- 1500 J/kg
range with modest shear, so some organized cells will be possible.
Moisture will be pooling ahead of the front with PWATs increasing
to 1.5 to 2 inches. So, heavy rain will also be possible with any
storm. Areas susceptible to flooding will need to monitor the
situation closely. With many people outside on the holiday,
remember that by definition a thunderstorm produces lightning
and poses a risk as well. When thunder roars, go indoors! A key
to the severe risk will be the degree of destabilization we see
with any clearing. Stay tuned.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 250 PM CDT Wed Jul 3 2024

Thursday night...Closed positively tilted upper low slated to
dig down acrs MN into western WI through early Friday morning,
with somewhat diffluent cyclonic flow sprawling acrs the upper
MS RVR Valley. 40-50 KT effective shear levels and lingering
MUCAPEs enough to continue isolated to sctrd showers and
thunderstorms to move eastward acrs the area well into the
night. More optimum support for stronger storms looks to occur
acrs MN into WI, and especially to the south acrs central MO.
But there may be enough locally to fuel a few strong to severe
storms locally with large hail and gusty downburst winds as the
main threats. But with the low coverage more areas will remain
dry as opposed to get clipped by a passing storm. Pre-wave
southwesterly LLVL flow/fetch will also draw higher THTA-E air
back up acrs the area, noted by a PWAT increase to 1.5-1.8
inches. So localized heavy rainfall will continue to be a factor
to keep in mind, but at very localized swaths. Low temps in the
60s

Friday...Upper low/trof still on track to roll acrs the western GRT
LKS into Sat morning. The associated cool pool aloft and any vort
spokes should generate isolated to wdly sctrd instability showers
possible acrs the area during the afternoon, especially north of I-
80. Ambient cumulus, the chance for a few showers and the cool pool
itself may keep a lid on the temps at below normal levels mainly in
the 70s.

Saturday and Sunday...Broad upper troffiness still looks to reign
acrs much of the upper CONUS this weekend, getting re-enforced acrs
much of the upper midwest by additional northern stream upper waves
propagating out of western Canada and into the mid/upper MS RVR
Valley almost clipper-style. Long range timing these waves still
suggest that Saturday will be dry ahead of this incoming process.
Temps will still look to moderate back into the lower 80s. There may
be a few showers and storms moving into the area Sat night with the
first clipper, but as the upper trof axis slides overhead, late
Sunday and especially Sunday night may be a better chance for sctrd
showers and storms to occur. Seasonable temps in the low to mid 80s
Sunday.

Early next week...Upper jet and synoptic scale feature progs suggest
the longer wave upper trof to linger and even deepen acrs much of
the mid to upper MS RVR Valley this period. This would allow for
wdly sctrd shower and storm development in the afternoon heating
under this feature, with Monday looking prime. Trof axis migration a
bit more off to the east may make for less coverage by Tuesday.
Northwest flow and cooler core nature to the upper trof will
continue to support near seasonable to somewhat below normal temps
this period.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 640 PM CDT Wed Jul 3 2024

VFR conds for much of this taf cycle through Independence Day.
The exeption is the potential for MVFR VIS late tonight into
early Thursday with BR due to calm winds. Then scattered light
showers may move across the taf sites in the morning and early
afternoon. This was covered with a Prob30. Beyond this cycle,
mainly Thursday evening, a cold front is expected to bring a
sct-bkn line of thunderstorms. South winds 10-15 kts for much of
Thursday.

&&

.HYDROLOGY...
Issued at 1211 PM CDT Wed Jul 3 2024

The forecasts along the Mississippi River havn`t changed much from
the previous ones, with many forecast points cresting into the
weekend. Locations from Dubuque to Keokuk are still expected to
crest over their respective Major Flood Stage levels. At Gregory
Landing, a crest in the Moderate category is forecast. The crest is
forecast near Dubuque and Bellevue on July 4th and 5th, with sites
from Fulton to Keokuk seeing a crest between July 6th and 8th.

On the Maquoketa at Manchester, the heavy rains and training
thunderstorms to produce them did not materialize and shifted to the
south of that basin. Thus it is no longer expected to reach the
minor flood stage and the warning has been cancelled.

Also with the rainfall amounts not being quite as high or widespread
as earlier anticipated in some of the more northern basins, several
tributary forecasts have been toned down some. Ongoing river flood
watches and warnings on the Cedar, Iowa, Wapsi, Skunk, and Maquoketa
Rivers have been adjusted accordingly to the rainfall reports from
this morning. But with a few other areas indeed receiving torrential
rainfall a bit further south, the river flood watches for the North
Skunk River near Sigourney and English River at Kalona have been
upgraded to river flood warnings.

Current projections for additional rainfall over the next few days
through the end of the week look more spotty with widespread heavy
rain not likely. This should help maintain the current forecasts
from deviating too much from the most recent forecasts.

&&

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

&&

$$

SHORT TERM...14
LONG TERM...12
AVIATION...Haase
HYDROLOGY...12