Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 291127
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
627 AM CDT Mon May 29 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 AM CDT Mon May 29 2017

At 2 AM CDT...Upper Midwest under westerly flow with surface high pressure
from Plains moving in. Temperatures are in the mid/upper 50s with mostly
clear skies. Upstream energy supports cool and dry conditions for late
May the next 3 days with isolated PM showers or isolated popcorn storm.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Mon May 29 2017

Short Term Forecast Confidence Assessment...good or above average.
Main issues are how gusty winds get today with possibly isolated
PM shower or brief storm along and north of highway 30.

Today...a chamber of commerce day good BL mixing supports breezy winds
of 15 to 25 MPH in the afternoon with some isolated gusts near 30 MPH
along and north of highway 30. Convective temperature of 70-72F may
be reached north if dewpoints stay near 50F which may be too high with
mixing. This with cold air aloft may spawn isolated showers or brief
rumbles of thunder along and north of highway 30. If dewpoints mix
out and thus are lower then convective temperatures likely will not
be reached. Highs today should be upper 60s far north to middle 70s
central and south.

Tonight...clear to mostly clear and seasonably cool with light westerly
winds. The light winds should allow for decent decoupling for mins
near lower ends of guidance with upper 40s common north to lower 50s
south.

.LONG TERM...(Tuesday through next Sunday)
ISSUED AT 330 AM CDT Mon May 29 2017

Tuesday and Wednesday...Broad upper trof will continue it`s reign
acrs the upper Midwest and GRT LKS for the first part of this
period, before elongating/de-amplifying more to the east. Tuesday
appears to be another deep mixing day up to at least H75 MB to help
make for breezy conditions and make the most out of thermal profiles
to boost highs into the upper 60s in the north, to the low to mid
70s along and south of I80. Another vort spoke embedded in cyclonic
flow aloft, and diurnal instability to produce isolated to widely
scattered showers and possibly a thunderstorm by afternoon. Then a
passing bout of llvl ridging to make for a clear and seasonably cool
night Tue night into Wed morning. Wednesday a dry sunny day under
lingering ridging with somewhat below normal high temps. Southerly
return flow starts to organize up the plains late Wed and into Wed
night. A low chance for some elevated warm air advection induced
showers and storms bleeding into the far western CWA late Wed
night/early Thu morning, with several 00z model runs giving
credence to the lingering ridge axis and backing off on precip
arrival through 12z Thu.

Thursday and Friday...Latest trends on the 00z run medium range
models suggest a potentially unsettled WX pattern setting up to end
the week with. They generally suggest organizing and retreating warm
frontal-like llvl baroclinicity to lay out nearly parallel to
cyclonic west-northwesterlies aloft, somewhere from the western MO
RVR valley to the southern GRT LKS. Increasing warm moist conveyor
wrapping around western flank of broad southeast Atlantic ridge
complex, and streaming north up the plains and MS RVR Valley, will
impinge on this frontal feature for a shower and thunderstorm focal
point. The models suggest increasing shower/storm activity acrs the
area as Thu and especially Thu night progresses.

Nocturnally enhanced LLJ processes may even induce enhanced storm
clusters or MCS activity from acrs IA and over to the southern GRT
LKS Thu night into Fri morning. Some chance of severe storms and
swaths of heavy rainfall along this potential convective axis. What
ever happens Thu night will affect Fri and Fri night, and the models
probably not handling the potentail scenario well at this point.
Lingering convective debris, outflow boundaries and the main front
itself will all be players on shower/storm redevelopment and
placement later Fri. High temps for Fri a real "crap shoot" at this
point as well. Interesting that both the 00z ECMWF and GFS are
hinting at backdoor-like llvl high pressure dumping down the
northwestern GRT LKS and putting the associated llvl northeasterly
flow "squeeze play" on the warm front to make it quasi-stationary
from SD, down acrs IA and into central IL and IN Fri night. Thus
this could be the zone of more shower-storm development Fri night
into early Sat.

Saturday and Sunday...Little confidence this period after a
potentially muddled early Sat, as model descrepancies grow with mean
synoptic scale evolution over the weekend. The 00z ECMWF suggests a
more amplified Omega block forming as the GRT LKS troffiness
dominates and shunts upstream upper ridge further to the west acrs
the plains. The Euro also more bullish with llvl backdoor ridging
scouring things out to the west and southwest including the local
CWA, for a mainly dry Sat afternoon through Sunday. But the trade
off is cooler than normal east to northeast flow for the rest of the
weekend. The 00z GFS not nearly as blocked and progresses an
upstream wave acrs the upper Midwest late Sat and into Sunday for
more precip chances through the long range. The 00z GEM sides more
with the GFS. Latest H5 MB geopotential height trends lean toward
the ECMWF. So as a happy medium for now, will keep POPS through
Saturday but dry things out by Sunday. Will also go with cooler
temps by the second half of the weekend.     ..12..

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 623 AM CDT Mon May 29 2017

VFR conditions to prevail the next 24 hours. Some FEW-SCT clouds with
bases aoa 5k AGL next 24 hours. Westerly winds of 10 to 15 MPH will
gust to near/over 25 MPH at times this afternoon. There is a low risk
of a -shra/-tsra at DBQ/CID terminal between 19-24Z this PM but coverage
and confidence are too low to even mention at this time. Worst case
is still looking at cigs AOA 5K AGL and visibilities AOA 4 Miles.

&&

.HYDROLOGY...
Issued at 330 AM CDT Mon May 29 2017

The Mississippi at Burlington was upgraded to Major category
flooding Sunday evening, as the forecast confidence increased
enough with routed flow that levels will reach or exceed 18 feet
this Wednesday night or early Thursday morning.

Otherwise, flood warnings continue for most other sites along the
Mississippi River for minor to moderate flooding. Flood watches
remain in effect at Bellevue (BLVI4), and Keokuk (EOKI4), where
forecasts indicate levels reaching or just exceeding flood stage
this week. Forecast confidence remains on the low side with these
two sites. If Bellevue L&D 12 continues it`s upward creep, the call
on a warning or not will have to be made today, with it forecast to
touch flood stage by this Monday evening. But it is also showing
signs of peaking out now into this morning just below the flood
stage. The watch will continue for now.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

SYNOPSIS...Nichols
SHORT TERM...Nichols
LONG TERM...12
AVIATION...Nichols
HYDROLOGY...12



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