Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 260453
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1153 PM CDT WED MAY 25 2016

.UPDATE...
Issued at 1153 PM CDT Wed May 25 2016

Storm cluster over NW MO and a separate linear complex from NW IA
to east central NE will continue east-northeastward overnight,
but likely encounter less favorable environmental conditions by
the time they reach the forecast area between 3 and 6 am. Latest
convective allowing models show this occurring with the HRRR
mainly impacting the northern half of the area and others not as
precise and possibly cwa-wide. Will keep slight to low end chance
pops in place for late night/early morning thunderstorms as
confidence is not yet high enough to being increasing pops.

&&

.SYNOPSIS...
Issued at 340 PM CDT Wed May 25 2016

The latest SFC analysis was indicating a low pressure system acrs
extreme southeastern SD...with main associated warm front now
adjusted to the north of the local area into southern MN into WI.
The latest water vapor imagery was indicating a vort max acrs
northeastern IA into MN, flaring up the showers and storms acrs MN
into WI ATTM. A trailing lobe was seen jutting down acrs the local
area helping induce the sctrd showers and storms currently in NW
IL. Another upper wave embedded in broad southwesterlies was noted
out acrs NEB.

&&

.SHORT TERM...(THIS EVENING THROUGH Thursday)
ISSUED AT 340 PM CDT Wed May 25 2016

Will keep isolated to low CHC pops acrs the far northeastern
CWA/NW IL through 02z or so for lingering activity or some short
lived new development of showers and storms in those areas, but
good chance that most everything will be east of the CWA this
evening as the main upper wave pushes toward northern WI/U.P. of
MI. Then we may have a mid evening lull or just an isolated
shower/storm west of the MS river thru midnight. Then as the
above mentioned NEB wave rolls acrs the northwest half of IA
toward midnight, several solutions suggest enough elevated THTA-E
feed and convergence to lee of the vort max to spark at least some
scattered showers and storms acrs western into central IA as the
evening progresses...with some of this making it acrs the local
area from the west especially after midnight.

Currently there does not appear to be enough support for a full
blown MCS barreling it`s way acrs the area, but we may have more
in the way of some storm clusters to go along with the isolated to
sctrd showers/storms, especially south of I80 late tonight. Will
increase Chance POPs after midnight, but with lack of confidence
in coverage and the way it has been going lately, do not want to
try and nail down areas of likely POPs. See little in the way of
any severe storm threat especially after midnight, but there could
be locally heavy rain of over a half inch where a more enhanced
storm cluster manages to propagate over.

Thursday...after whatever convective debris there is clears in
the morning, a bout of both sfc and upper ridging should make the
day mainly dry. Will lean toward warm temps of mid to upper 80s
banking on some insolation even if filtered some by cirrus. More
sun than currently expected along with mixing potential could make
for more widespread upper 80s with even a 90 degree reading a good
bet. Convective spawning grounds, which could be explosive, looks
to take place late Thu afternoon and early evening to the west
acrs the east central plains and southern MO river Valley. ..12..

.LONG TERM...(Thursday NIGHT THROUGH next Wednesday)
ISSUED AT 340 PM CDT Wed May 25 2016

Thursday Night...Southwest flow aloft with little in the way of
divergence over E Iowa/W Illinois. The main jet streak associated
with the Southwest longwave trough will be located over the southern
plains. Lower in the atmosphere, convergence on the nose of the 850
mb low-level jet is focused across E Nebraska and SW Iowa.

MCS ingredients are favorable over central/eastern Nebraska and SW
Iowa where southerly 850mb flow converges beneath broad 300mb upper
divergence zone. For E Iowa/W Illinois, where conditions are less
favorable, PoPs are in the 50-60% range. Currently, widespread
showers and storms are not expected.

Friday...Upper jet streak moves through the Central Plains, well
west of E Iowa/W Illinois. Models have a series of embedded
vorticity maxima crossing the Upper Mississippi River Valley through
the day; however, confidence is low on whether these form and where
they track as they are convectively induced mesoscale features (PV
anomalies) in the models. PoPs are around 60%...so at least
scattered coverage looks likely. Highs are forecast in the lower
80s; dewpoints in the mid 60s will make it feel muggy.

Thunderstorm potential: Moderate instability on the order of 1500-
2500 J/kg MUCAPE but weak 0-6 km bulk shear is an environment
conducive for an isolated strong storm but an overall low severe
threat.

Saturday...Weak upper level disturbance interacting with humid
airmass could result in isolated to sct storms.  At this time,
chances for measurable rain for any one location remain low at 40-
50%. Forecast highs are in the upper 70s to lower 80s.

Sunday...Models differ on timing and strength of shortwave crossing
the Upper Midwest. Low end 20-30% PoPs for now until details become
more clear. General synoptic setup does not look favorable for
widespread convection. Highs are forecast in the lower 80s on avg
with dewpoints in the lower/middle 60s.

Monday through Wednesday...Above average temps continue. Weak
pressure fields would prevent significant moisture advection, either
positive or negative. Therefore, dewpoints in the 60s are forecast
along with chances for isolated to sct storms. Uttech

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z Thursday NIGHT)
ISSUED AT 1153 PM CDT Wed May 25 2016

Organized thunderstorm complexes over NW MO, eastern NE and
western IA will continue eastward, possibly reaching the
terminals between 09z and 12z in a weakening fashion. Confidence
is not yet high enough to go beyond vicinity wording for showers
at CID, MLI and BRL, while a tempo group was included at DBQ.
Thursday, a break between systems is likely in the morning, then
another round of showers and thunderstorms is possible from late
afternoon though evening, which is advertised with prob30 groups
for now. Otherwise, conditions will be predominantly VFR
throughout with light south to southwest surface winds.

&&

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

$$

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



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