Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 192010
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
310 PM CDT FRI AUG 19 2016

.SYNOPSIS...
Issued at 310 PM CDT Fri Aug 19 2016

18Z surface data has a boundary running from northwest Indiana, to
just north of KDVN and up into the KALO area. The main cold front
ran from northeast Wisconsin to a weak low near KRST, and then into
southeast Nebraska. Dew points were in the 70s from the Great Lakes
to the Gulf Coast ahead of the front. Behind the front dew points
were in the 50s and 60s across the northern and central Plains.

&&

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 310 PM CDT Fri Aug 19 2016

Through late afternoon the more focused convection will be north of
highway 30 an west of the Mississippi. Convection here is taking
advantage of the outflow boundary from the nocturnal convection and
an instability gradient. Across the remainder of the area, isolated
convection will be possible during the warmest period of the day.

This evening more convection will slowly start developing across the
area as forcing ahead of the cold front increases. Some storms may
produce locally heavy rainfall due to their slow movement and the
high moisture content of the atmosphere. After midnight, forcing and
moisture increases significantly across the area. Widespread
convection will develop along the frontal zone and slowly move east
through sunrise that may produce locally heavy rainfall.

Saturday...the cold front sweeps through the remainder of the area
during the morning. Convection will be widespread at sunrise. By
late morning and continuing into the afternoon, the widespread rain
will end from west to east and become more scattered in nature.

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 310 PM CDT Fri Aug 19 2016

Cooler and drier conditions following Saturday`s cold frontal
passage will be the big story from Saturday night through Sunday.
Gradual warmup back to near normal temperatures to follow next week,
with a slow moving frontal system bringing our next chances for rain
from Tue night through Thursday.

Saturday night through Sunday: Initially cyclonic low level NW flow
Saturday night will be advecting cooler and much drier air into the
area. Increasing subsidence overnight should erode any lingering
clouds from SW to NE. Latest guidance backed previous forecast lows
in the lower to mid 50s over most of the area and only minor tweaks
were made. The incoming high pressure ridge rolls through the area
Sunday, causing NW winds to become light by evening. 850 mb
temperatures and MOS support highs only in the lower 70s north
and mid to upper 70s south.

Temperatures moderate back closer to late August normals early next
week, with highs back in the 80s. Sunday night still looks to be the
coolest, with clear skies and light winds leading to lows around 50
to the mid 50s and possibly a few degrees cooler if the timing of
the ridge axis slows some and the airmass remains dry. An increasing
surface pressure gradient building Monday into Tuesday will result
in a breezy period as winds could reach 15 to 25 mph by Tuesday
afternoon.  POPs move back into the forecast Tuesday night with a
possible warm advection wing ahead of the main front kicking off
thunderstorms, which pushes through with higher pops for showers and
thunderstorms Wednesday into Wednesday night. Model agreement and
forecast confidence wanes from Wed onward, with differing depictions
of the timing and placement of a wave of low pressure tracking along
the front. For now, this will require keeping pops from Wed night
into Thu, until this system is better resolved. Confidence is higher
that Friday should be dry with surface high pressure over the area.
This results in highs back in the 70s to near 80, lower humidity
and overnight lows in the 50s Friday night.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
ISSUED AT 1239 PM CDT Fri Aug 19 2016

Mainly VFR conditions with pockets of MVFR will be seen through
06z/20. Convection in central Iowa should move generally east but
should slowly turn more to the southeast following the best
instability. KCID has the best chance of being affected by this
convection with lesser chances at KDBQ/KMLI. After 06z/20
conditions will slowly deteriorate to MVFR as widespread
convection develops along the approaching cold front. Brief IFR
conditions will be possible in the stronger storms.

&&

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

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...Sheets
AVIATION...08



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