Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 280452
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1152 PM CDT FRI MAY 27 2016

.UPDATE...
Issued at 1151 PM CDT Fri May 27 2016

The surface boundary that stalled over eastern IA this evening and
resulted in a several hour long period of nearly stationary storms
and resulting heavy rainfall has since washed out. This has
occurred as the next wave of thetae advection and upper level
forcing was lifting northeast out of MO spreading rain and
embedded thunderstorms back northward across the area. Widespread
additional rainfall amounts over a half inch are likely, generally
west of the MS river over the next several hours. Focused heavy
rainfall, needed for additional flash flooding does not look
likely as this system should progress northward with rain
decreasing over the next several hours.

&&

.SYNOPSIS...
Issued at 330 PM CDT Fri May 27 2016

The latest SFC analysis was indicating a weak wave acrs central
IA...connecting into a warm frontal boundary arching up into
south central WI. South to southeast sfc flow into this boundary
was pooling mid to even upper 60 Dpts acrs the local area, but
these higher moisture levels and cloud cover keeping a lid on
afternoon ambient temp warming as well as SBCAPES. This sfc
wave/boundary feature acrs eastern IA a refection of a remnant MCV
rolling northward up along and east of the MS RVR Valley, with
isolated to sctrd showers and a few thunderstorms on its northern
flank. Other sfc troffiness and low pressure was noted acrs the
west central plains. Aloft...besides the MCV, another vort max was
noted upstream acrs northern AR in steep south-southwest steering
flow.

&&

.SHORT TERM...(THIS EVENING THROUGH Saturday)
ISSUED AT 330 PM CDT Fri May 27 2016

Tonight...Expect the isolated to sctrd showers and storms in the
north half of the DVN CWA to move north or diminish early in the
first period as the MCV rolls up into WI. But then eyes turn to the
vort max to the south acrs the Ozarks. As this feature propagates
toward the area, expect an increase of showers and embedded
thunderstorms to move in from the same direction(south-to-north) as
the night progresses. This activity already forming and taking place
acrs northern AR into the southern third of MO. Rather widespread
areas of showers and embedded storms should make it up to just south
of the I80 corridor by 10-11 PM CDT, and continue to spread north to
the Hwy 20 corridor by 1 AM CDT or so. Projected shear, instability
and saturation profiles all suggest a very marginal threat for any
type of severe weather tonight. But with PWATs of 1.5 to 1.6+
inches, some locally heavy rainfall will be possible. Progressive
nature to the more enhanced cells should limit any one area really
getting hit hard with heavy enough rain to produce flooding, and
most areas will get from 0.25 to 0.75 of an inch of rainfall by Sat
morning. Expect another night of rain cooling, sub-guidance sfc
dpts, or storm outflow to produce low temps generally below most of
the guidance lows, so will go with low to mid 60s.

Saturday...after some lingering showers exit the Hwy 20 corridor,
the rest of the morning will look to be a lull period with little or
no shower/storms acrs the local area as the overnight upper level
wave shears out acrs MN and WI. But cyclonic southwesterlies
pivoting acrs IA around the main wave acrs the MO RVR Valley will
then look to spark more sctrd showers and storms acrs the local FCST
area by Sat afternoon. With more clouds/LLVL moisture/ convective
debris in mind, will go with highs in the upper 70s to lower 80s and
limit the SBCAPES to 1500 to 2000 J/KG by afternoon. Vertical
deep shear profiles also look limited by Sat afternoon, thus
another marginal severe weather threat day. But if more insolation
occurs than currently expected and can boost higher temps/CAPES
during the afternoon, can`t rule out at least an isolated strong
to severe storm in the local area with damaging winds the main
threat.   ..12..

.LONG TERM...(Saturday NIGHT THROUGH next Friday)
ISSUED AT 330 PM CDT Fri May 27 2016

Main focus is with upcoming Memorial Day holiday forecast.
Overall, the signal appears to be toward limited precip chances
and mostly dry. Having said that, Saturday night harbors the best
opportunity for measurable rain with passing upper level trough,
although still kept at just moderate chances given boundary layer
stabilization, waning jet dynamics and weak positive vorticity
advection. Sunday will have just a small chance during the
afternoon mainly over northeast Iowa and northern Illinois in
lingering cyclonic flow on backside of departing shortwave. Highs
Sunday expected to be in the upper 70s to lower 80s. On Monday,
Memorial Day, another weak disturbance and diurnal heating should
bring about scattered showers and storms during the afternoon,
with the best chances /30-40 percent/ west of the Mississippi
River. Highs on Memorial Day look to be a tad warmer and mainly
around 80 to lower 80s.

Tuesday through Friday...confidence is poor on main features
especially late week with substantial run to run model
differences, more notable with GFS. GFS has a closed low over the
central plains by late week, with moisture streaming northward and
upper diffluence for continued day to day storm chances last half
of the week. Meanwhile, the ECMWF has the low over western
Ontario, which would place the region in drier northwest flow.
This would favor weak high pressure and pleasant conditions for
the region to start June. Forecast is attempting at a blend with
pops adjusted down to slight chance while temps nudged down to
near seasonal normals in the upper 70s to around 80.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z Saturday NIGHT)
ISSUED AT 1151 PM CDT Fri May 27 2016

A wave of widespread rain and embedded thunderstorms will continue
to lift north through the terminals over the next several hours.
Initial VFR conditions should lower to MVFR as the air saturates.
Current thinking is the rain should exit northward by sunrise,
leaving several hours of MVFR ceilings Saturday morning, followed
by VFR conditions through the day with light southerly winds.
Another round of showers and thunderstorms is likely from around
mid afternoon through early evening, which is handled with low
confidence prob30 wording for now, then vicinity wording Saturday
evening.

&&

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

$$

UPDATE...Sheets
SYNOPSIS...12
SHORT TERM...12
LONG TERM...05
AVIATION...Sheets



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