Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 230620
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
120 AM CDT THU JUN 23 2016

.UPDATE...
Issued at 120 AM CDT Thu Jun 23 2016

Lingering low level moisture was leading to areas of fog and some
low clouds over the past hour, especially along and east of the MS
river. With light, weakly convergent low level winds over the rest
of the night as the weak lows over west central Illinois and
western Wisconsin gradually fill and shift east to southeast,
conditions will be favorable for fog formation and will continue
to monitor trends. For now, will add mention of fog over the
central and east, where the SREF and HRRR confer on the high
likelihood of fog development.

&&

.SYNOPSIS...
Issued at 304 PM CDT Wed Jun 22 2016

18Z surface analysis has a low near KCIN. A warm front ran southeast
from the low into southeast Iowa and southern Illinois. Several weak
boundaries were south of the warm front across Missouri and southern
Iowa. Dew points were in the 50s across the Great Lakes and upper
Midwest with 60s and 70s from the mid Mississippi Valley to the Gulf
Coast.

&&

.SHORT TERM...(THIS EVENING and Tonight)
ISSUED AT 304 PM CDT Wed Jun 22 2016

The question is when does convective initiation occur. The overnight
storms have created a stable layer of air which so far has prevented
any new convection from developing. Satellite trends show low level
clouds developing on top of the stable air across northern Iowa.

The special sounding done early this afternoon indicates the stable
air is quite deep. Thus the forecast for late this afternoon is
binary. Either no convection will occur OR significant severe
convection develops in the 5 to 7 PM time frame plus/minus an hour.

IF the current RAP trends are correct, convective initiation should
occur 4-6 PM roughly in the highway 20 corridor plus/minus 20 miles.
The individual discrete cells will rapidly grow upscale into an
organized severe thunderstorm complex early this evening and race
east southeast toward eastern Illinois and Indiana.

Based on what is being suggested by the RAP trends, the main severe
threat and thus most of the thunderstorm activity should be done
for a majority of the area between 9 and 10 PM.    ..08..

Later tonight, after the smoke clears, still a low chance at least
for some back building convection to try and tentacle it`s way west-
southwest toward the eastern CWA after midnight, but short range
model solutions all really varying on this potential. Also, before
post-storm llvl northwest flow increases, a chance for some fog at
least in the northeastern CWA before dawn. Lows in the mid 60s in
the northwest, to the low 70s south.

.LONG TERM...(Thursday THROUGH next Wednesday)
ISSUED AT 304 PM CDT Wed Jun 22 2016

Thursday through Friday...weak sfc trof or backdoor front pushing
southwest acrs northeastern and eastern portions of the CWA may
generate some showers along it`s convergent axis in those areas on
Thu. Otherwise a cooler day with highs being held in the 70s in the
north, low to mid 80s still along and south of I80. Clear out and
sfc wind drop off under a ridge of high pressure to make for a
seasonably cool night with lows in the 50s to low 60s. Some chance
for fog or ground fog in recent heavy rainfall areas. Southeasterly
return flow increases into Friday as the ridge migrates into the GRT
LKS...Fri highs in the low to mid 80s with some areas in the west
pushing the upper 80s. Still a low chc for some elevated warm air
advection type showers and storms later Friday night especially west
of the MS RVR.

Saturday and Sunday...A warm and more humid day Sat, with either air
mass type thunderstorms, or like the new 12z ECMWF suggests a warm
frontal type chance to produce some precip. Best dynamics combined
with building heat and humidity for MCS generation appears will take
place further north acrs the eastern Dakotas into MN possibly
tailing down into NW/N.Central IA late Sat afternoon and night. A
cool front associated with another seasonably strong ridge-riding
wave, will look to push southeast acrs the local area later Sat
night into Sunday but in a weakening fashion. Still, some showers
and storms possible of producing locally heavy rain may accompany
the front into the area. A nocturnal strong storm not out of the
question. Will advertise very warm temps again on Sunday, but much
will depend on convective debris and lingering precip during the
day.

Monday through next Wednesday...latest medium range solutions re-
establish broad upper ridging acrs the Rockies, with troffiness
settling down acrs the upper MS RVR Valley into the GRT LKS early
next week. Will advertise mainly dry and seasonable conditions acrs
the local area, but will have to watch the lee of the ridge acrs the
northwestern to central plains and MO RVR Valley that will act as a
storm track, some of which may clip at least the southwestern CWA by
Tue or Wed.    ..12..

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z Thursday NIGHT)
ISSUED AT 120 AM CDT Thu Jun 23 2016

Update...
Low clouds and fog have developed since the 06Z TAF cycle issuance
and appear most likely to impact the DBQ and MLI sites over the
next several hours. With lingering low level moisture and weak
wind fields, there is the potential for dense fog, but for now
have only periods of IFR conditions over the next several hours
in updates for MLI and DBQ. Will closely monitor for possible updates
and addition of fog to CID and BRL to the early morning forecast
periods as there is a potential for IFR or even LIFR conditions
during the 08z to 12z timeframe.

06z discussion...
Thunderstorms have ended over the area, and the storms moving
towards eastern Iowa from the north are beginning to dissipate.
Thus a quiet and mainly VFR 24 hour period is forecast with north
to northeast winds at 5 to 10 kts. Some fair weather cumulus is
likely thursday, with CIGS mainly 3500 ft or higher.

&&

.HYDROLOGY...
Issued at 304 PM CDT Wed Jun 22 2016

Continue to watch the potential for river flooding due to the heavy
rains from early this morning. Have been getting a better idea of
the basin average rainfalls so confidence is increasing in the
forecasts downstream. However, there are some small feeder
tributaries that continue to rise so there remains some uncertainty.
The Cedar River at Conesville has either reached its crest or is
nearing it but there remains a lot of water coming down the channel
so the river will remain high even after it drops below flood stage.
From the confluence of the Iowa and Cedar Rivers and downstream, the
current data has lowered the forecasts a bit, thinking the runoff is
lower due to the ongoing dry conditions to this point and the crops
being able to take in some of the water. Will continue to watch
closely, but will continue the flood watch for these locations until
confidence to upgrade or cancel occurs.

&&

.DVN Watches/Warnings/Advisories...
IA...None.
IL...None.
MO...None.
&&

$$

UPDATE...Sheets
SYNOPSIS...08
SHORT TERM...08/12
LONG TERM...12
AVIATION...Sheets/Ervin
HYDROLOGY...Brooks



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