Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 241056
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
556 AM CDT Mon Jun 24 2019

.UPDATE...
Issued at 555 AM CDT Mon Jun 24 2019

Increased pops early this morning mainly along and east of the MS
River in advance of a weak upper level disturbance pushing across
the area. By mid morning this should move east of the dvn cwa.

&&

.SYNOPSIS...
Issued at 310 AM CDT Mon Jun 24 2019

Finally a quiet night across the dvn cwa with the rain falling
across MN. Early morning temperatures were in the 60s to lower 70s.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 310 AM CDT Mon Jun 24 2019

Possible severe storms this afternoon.

Today: A sharp upper level trough currently in eastern NE will
push across eastern IA/northern IL this afternoon into early this
evening, basically the time frame of 1 to 7 pm. Skies should be
mostly cloudy/partly sunny but enough breaks for sunshine should
push SBCAPES to 2500 J/kg, along with freezing levels at 10,500 ft
agl and steep lapse rates. Sfc dewpoints will be in the lower to
mid 60s. However, deep layer shear is moderate at best. With the
better forcing arriving during the afternoon heating there is the
risk for severe storms (isolated supercells) that would produce
damaging winds and large hail. The sfc-1km shear is quite weak for
tornadoes so this threat appears very low but not zero. The main
area of concern is roughly along and north of Interstate 80 where
the better forcing/moisture convergence will exist. This is where
SPC has a marginal/slight risk. By early evening the activity
should be shifting off to our northeast and east. I will have
likely pops this afternoon in our northern counties. With deep
mixing west winds should gust to around 30 mph especially this
afternoon. Highs will be in the lower to mid 70s.

Tonight: Subsidence in the wake of the trough will allow for a
mostly clear night with lows in the lower 60s at most locations.

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 310 AM CDT Mon Jun 24 2019

Initial focus is on the potential for severe storms Tuesday. The
main story through the rest of the extended forecast will be the
building heat and humidity, especially toward the weekend as an
upper level ridge builds over the plains.

Tuesday: A weak surface boundary is expected to setup roughly along
the IA/MO border during the day. The entire area will also be the
focus of returning low level moisture around high pressure that sets
up over the southeast U.S.  This may send surface dewpoints back
into the upper 60s, possibly well into the 70s over much of the
forecast area by afternoon, along with surface temperatures reaching
well into the mid to possibly upper 80s. With steep mid level lapse
rates due to cool temperatures aloft and a returning feed of high
thetae on southwest winds, MUCAPES may push well into the 3000 j/kg
plus range. This would be favorable for strong to severe storms by
afternoon and especially in the evening, when a subtle upper level
shortwave in the zonal flow is progged to push through. This may
trigger at least isolated storms in the afternoon, then a more
organized storm complex across the southern half of the forecast
area in the evening, with a smaller complex suggested by some
convective allowing models further north along the highway 30
corridor.

SPC has nearly the entire forecast area outlooked in a
marginal risk, and a slight risk for areas south of I-80 corridor
from the Quad Cities westward. The main storm threats would be
damaging wind, large hail and locally heavy rainfall. For now, pops
are kept in the chance range with widespread low QPF, but both may
need to be increased in later forecasts if this setup is maintained.

Wednesday through Saturday: After a zonal upper level flow through
midweek, an upper level ridge builds over the plains with an
associated dome of hot air. The local area will be on the edge of
this, providing highs well into the 80s throughout with dewpoints at
least into the 60s and possibly lower 70s. There will be low
probabilities for thunderstorms each day, but the best chance at
this time looks to be Thursday night, where model consensus has a
shortwave passing through the region and chance pops.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 555 AM CDT Mon Jun 24 2019

After 12z/24 conditions will slowly deteriorate to MVFR cigs.
After 18z/24 conditions will improve to VFR with diurnal SHRA/TSRA
possible as the next upper level disturbance approaches from the
Plains. SW-W winds becoming gusty during the afternoon with gusts
to 30 knots. Later this evening skies become clear and winds
diminish to less than 10 knots.

&&

.HYDROLOGY...
Issued at 1200 PM CDT Sun Jun 23 2019

With another night of rainfall past, confidence is increasing that
significant additional rises will NOT occur early this week on
the Mississippi and tributary rivers. Additional rainfall amounts
of 0.25 to 0.75 inches are forecast today through Monday, and this
is not expected to exacerbate the current flooding situation.

On the Mississippi River, most points steadied out temporarily in
response to the recent rain. Minor short term rises occurred from
the Quad Cities to Muscatine due to the heavier rains of 1 to 1.5
inches that fell in the past day along and just south of the
Interstate 80 corridor. For the next 1 to 2 days, most points will
hold nearly steady before continuing to fall. Some minor rises
are possible at Keokuk and Gregory Landing before the recession
resumes.

On the tributary rivers, in bank rises are occurring on many
points along the Wapsi, Des Moines, Iowa, Cedar, Skunk, and Fox
Rivers. These rises will be short-lived with low chances of
additional heavy rain over the next several days. The LaMoine at
Colmar will start a rapid drop below flood stage early this week,
while the Des Moines at St. Francisville is forecast to remain
above flood stage this week with continued high outflow from Lake
Red Rock.

The biggest uncertainty with the river forecasts later this week
and into next week revolves around the potential for heavy
rainfall in the upper Mississippi basin, well to the north.
Widespread 2 to 3 inch amounts are currently forecast for this
area. However, the rainfall events are expected to be spaced out
enough to dampen the effects downstream in our area. The most
likely scenario for the mainstem Mississippi locally later this
week and next, is for periods of a slower recession or nearly
steady levels. This heavy rain to the north is NOT currently
expected to cause any significant new rises. On the tributaries,
additional rises cannot be ruled out if particular basins are
impacted with pockets of heavy rain, but the overall risk for
additional significant flooding appears to be low into next week.

With the inherent uncertainty in predicting these events, it will
be crucial for decision-makers to stay up to date with the latest
information.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

UPDATE...Haase
SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Sheets
AVIATION...Haase
HYDROLOGY...RP Kinney


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