FXUS63 KDVN 191745
Area Forecast Discussion
National Weather Service Quad Cities IA IL
1245 PM CDT Tue Jun 19 2018
Issued at 330 AM CDT Tue Jun 19 2018
The latest sfc analysis was indicating the main frontal boundary was
draped generally from west-to-east from along the western IA/MO
border region, to near Fairfield-Galesburg locally, and eastward
acrs north central Indiana. Isolated to sctrd clusters of shower and
thunderstorms continued to move along and north of this feature acrs
IA into WI/northern IL early this morning, with most of the
convective allowing models weakening the current strong activity out
acrs western IA as it moves east toward the local area toward
sunrise. Otherwise, the 00z model runs continue to show at wet
pattern for the central plains and acrs the Midwest for the rest of
the week, between the current boundary lay-out and then the
approaching slow-rolling upper low during the mid to late week
.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Tue Jun 19 2018
Today...The Hwy 20 corridor is water logged and rain sensitive,
especially the NW IL counties where 2-5 inches of rain has fallen
overnight. But besides a few passing isolated to widely sctrd storm
clusters early this morning, expect the heavy re-development of
showers and thunderstorms along and north of the front from midday
and especially this afternoon as upstream short wave propagates
eastward acrs IA. The frontal placement suggests this occurrence
would generally occur along and south of the I-80 corridor, and away
from the recently hard hit areas. Thus will hold off any flash flood
watch for now, although still expect secondary isolated to sctrd
showers/storms to move along the Hwy 20 corridor later this
afternoon and overnight would could produce a localized hydro-
aggravation to any ongoing flooding, just not a widespread threat.
As for the areas that receive a more widespread storms coverage south
of I80, Precipital waters(PWATs) of 2+ inches indicate an ongoing
threat of very heavy rainfall and at high rates. These more southern
areas can take a round or two of heavy rain without a widespread
flooding threat, but like last night in the north, any repeated
storms forming and then tracking along the boundary acrs the same
areas(training)may still produce localized flash flooding or at
least urban and small stream flooding. Another day of high CAPEs but
low bulk shear profiles, at least where most of the storms are
expected to occur, preclude much of a severe weather threat. But
there could be isolated wet microbursts, or if a storm cluster were
to manage to form a cool pool or partial bowing segment in the heat
of the afternoon to early evening for some damaging winds. Have
adjusted the POPs higher around the vicinity and just north of where
the frontal boundary is expected to be this afternoon. As for high
temps today, large bust potential in many areas depending on cloud
cover/convective debris, and boundary placement. But even for the
areas that are allowed to heat up, while they may be hot and muggy,
heat index readings are expected to remain below headline criteria.
Tonight...Much will depend on what coverage and where the convective
re-development occurs today, as to what lays out for tonight.
secondary boundaries and the main front itself may be sctrd acrs
much of MO into southern IA and western IL. Vertical soundings show
another marginal southwest 20 KT or so low level jet that may
impinge on and over these features, and will just have to go with
mainly widespread chance POPs acrs much of the area and can't define
a higher corridor of opportunity for now. But early hunches are that
northern MO into far southern IA and into west central IL may be
more favored again for nocturnal development and convective activity
focus. This could limit the sensitive northern areas to more widely
sctrd to isolated showers/storms which would be helpful to reduce
any flash flood/flooding threat tonight. Lows in the low 60s north,
to the low 70s in the far south. ..12..
.LONG TERM...(Wednesday through next Monday)
ISSUED AT 335 AM CDT Tue Jun 19 2018
The main themes of the long term period are continued wet conditions
through late week, along with cooler temperatures.
Wednesday through Friday: A slow moving upper low will push through
the region, with showers and storms expected area-wide. The severe
weather threat will be low. However, most areas will likely receive
at least an inch of rain, with locations along/south of Interstate
80 currently favored for averages of 2-3 inches. Breaks between
rounds of rain may be enough to preclude a widespread flash flood
threat, but this will likely become more of a concern after several
days of decent rainfall. A more significant impact is expected on
area rivers. See hydrology discussion below for more details. Expect
a cooling trend with a swing back to below normal temperatures.
Highs Thursday and Friday should be in the 70s.
Saturday through Monday: Little or no rainfall is expected over the
weekend in the wake of the upper level system. The ECMWF and GEM are
advertising another system late Monday. Temperatures will rebound
slightly toward normal, with afternoon highs in the upper 70s to low
.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
ISSUED AT 1240 PM CDT Tue Jun 19 2018
MVFR/VFR conditions with scattered convection will continue
through 00z/20 with localized LIFR conditions at KDBQ. After
00z/20 the models are unclear as to what will happen. The
scattered convection potentially will grow upscale into another
organized TSRA complex with the potential for IFR/MVFR conditions
Issued at 330 AM CDT Tue Jun 19 2018
Expect an extended period of wet weather across the area this week.
There is high confidence on storms occurring. Widespread amounts of
1-3 inches, possibly higher, are expected through Friday. Although
confidence in rainfall placement and timing remains low, areas along
and south of Interstate 80 are currently favored for the higher end
of the rainfall range.
As a result, at least within bank rises on area rivers will be seen
across eastern Iowa and northwest Illinois. Rivers that are already
high or in flood may see water levels rise again.
The crest on the lower Iowa river is currently working through
Conesville continues to slowly fall.
Dewitt will rise slightly for the next two days before falling.
Rock and Pecatonica rivers...
Joslin, Moline, and Como are forecast to rise to near or just above
flood stage this week. Freeport will continue a sharp rise over the
next day but is forecast to crest below flood stage.
LONG TERM...RP Kinney
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