Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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320
FXUS63 KDVN 250003
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
703 PM CDT FRI JUN 24 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 328 PM CDT Fri Jun 24 2016

Latest SFC analysis was indicating high pressure occupying the
western GRT LKS, while south to southeast return flow was noted
streaming north up the plains and MO RVR Valley. Aloft, broad
ridging was pumping up acrs much of the plains and upper MS RVR
Valley to the lee of digging trof acrs the northwestern Rockies.
Water vapor imagery was indicating a few weak vorts riding the ridge
acrs the central plains into MN.

&&

.SHORT TERM...(THIS EVENING THROUGH Saturday)
ISSUED AT 328 PM CDT Fri Jun 24 2016

Tonight...Most 12z run models continue to amplify the upper ridge
acrs the region, while at the sfc the high continues to migrate
eastward allowing for increasing southeasterly return flow into
early Sat morning. There are some signals of at least a marginal 15-
20 KT LLJ with some convergence inducing an elevated warm air
advection wing acrs the fcst area from the southwest after midnight.
Most of the 12z models have trended dry overnight probably taking
into account the ridge amplification aloft and will keep the fcst
dry as well. But can`t rule out these elevated nocturnal processes
producing something in the far west to southwest...maybe just some
AC. Otherwise besides some higher level debris clouds off the vorts
to the west/northwest, a mainly clear night. Lows generally in the
mid to upper 60s.

Saturday...the airmass currently out acrs western IA and the MO RVR
Valley will adjust east acrs the local area tomorrow...highs in the
upper 80s to low 90s, with a few sites pushing the mid 90s. Even
taking into account some dry down mixing in increasing south to
southeast boundary layer flow, sfc DPTs will still rise into the
upper 60s to low 70s. Combined with the ambient temps, these type of
DPTs will produce afternoon heat index readings in the mid to upper
90s, and a few around 100.

With latest fcst soundings suggesting convective temps around 90 or
in the lower 90s, there could be some buoyancy driven isolated to
wdly scattered pop up showers and thunderstorms Sat afternoon and
into the early evening. Weak to marginal shear profiles suggest not
much of a severe storm threat during this period, with storms not
being able to sustain for long and collapse back in on themselves.
Suppose an isolated downburst wind type occurrence possible under
a collapsing cell, but confidence low in this ATTM. Brief heavy
and localized downpours possible before the cells die off. More
areas will stay dry Saturday through 00z than experience a
shower/storm.     ..12..

.LONG TERM...(Saturday NIGHT THROUGH next Friday)
ISSUED AT 328 PM CDT Fri Jun 24 2016

Saturday night into Sunday - Lingering and weakening frontal system
will move through the area late Saturday night into Sunday producing
showers and thunderstorms.  But ingredients, including diurnal
timing, are not favorable for organized severe weather.  Model
agreement is fairly good here.  The front/clouds should clear most
of the CWA by afternoon allowing temps to rebound to very warm
levels with heat indicies in the 90s in many spots.

Monday through Wednesday - Surface high pressure under northwest
flow becomes the dominant pattern early next week.  Warm temps
Monday will cool a bit Tuesday-Wednesday with a reenforcement of
cooler Canadian air.

Model solutions differ a bit Wednesday night into Thursday with the
12Z GFS wrapping up a closed 850/700 mb low to our southwest, while
the ECMWF keeps the system an open wave, both embedded in the
northwest flow. Deterministic 12Z GFS is stronger than the GFS
ensemble mean, the latter of which is more in line with the 12Z
ECMWF. Thus have kept PoPs in the chance category at this time.
Friday looks to be a return to near normal summer weather - a little
warm, a little humid, and a low chance of storms meaning most areas
will be dry.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z Saturday EVENING)
ISSUED AT 652 PM CDT Fri Jun 24 2016

Looking for a few hours of MVFR visibilities late tonight/Saturday
morning as winds become light and dewpoints increase slightly to
narrow the temp/dewpoint spread. Visibilities should improve
by 13Z or 14Z with the boundary layer becoming mixed by mid
morning. May get some winds of near 20kts to mix to the surface in
the afternoon and also expecting SCT to BKN skies by early
afternoon at 4-5k ft for much of the forecast area. In addition,
there could be isolated to widely scattered showers or
thunderstorms in the afternoon, but confidence in the occurrence
or location is too low to add into the forecasts at this point.

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...Wolf
AVIATION...Brooks



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