Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 262336
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
636 PM CDT THU MAY 26 2016

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 355 PM CDT Thu May 26 2016

The latest SFC analysis was indicating low pressure with an arching
warm front acrs KS into Southeastern Neb back down into central MO.
A secondary trof was noted up into southwestern IA. A vort max was
noted acrs southeastern CO, with lee side southwesterly steering
flow sprawling out acrs the east central Plains.

&&

.SHORT TERM...(THIS EVENING THROUGH Friday)
ISSUED AT 355 PM CDT Thu May 26 2016

Tonight...will have to have some POPs this evening in the west
central to southwestern CWA for the potential for some of the
showers and storms in the current convectively active zone acrs
northwestern MO/IA border region, to propagate into the local FCST
area...probably into the southwestern and southern third of the
local area. But this activity will have to battle lingering mid
and upper ridge bulge from acrs southeastern IL...up acrs the
upper MS river Valley and thus may get eaten away at or decay
some as it tries to push east late this afternoon and into mid
evening.

But later on tonight, the upper wave currently acrs the southwestern
plains will roll up in steepening southwest flow acrs southwest into
central IA by midnight. This should help whatever congeals(MCS) out
of the current activity to the west/southwest...make it acrs the
local area. It may also spark new development in central Iowa mid
to late evening, which could also then come acrs the area as a
MCS-type feature. MCS forcing tools from the favored 12z run UKMET
and ECMWF target the northwest to northern half of the FCST area
from midnight on into early Friday morning. Other solutions hit
the south half of the CWA again. Although do think the UKMET/Euro
are hitting the right areas(northwest half or north half along and
north of I80)...not sure if there will not be convection in the
south as well and will go blanket Likely POPs after midnight into
Friday morning. With CAPES of 1500 to over 2000 J/KG lingering
well into the overnight, again see the threat of a storm cluster
developing it`s own cold pool and being able to produce damaging
winds. Large hail a secondary threat with marginal deep layer
shear to support bigger stones, but still not out of the question.
With PWATs increasing to 1.5 or even up to 1.7 inches, locally
heavy rain also a good bet with any enhanced storm cluster. A few
swaths of 1-2 inches of rainfall possible by Fri morning, but most
areas from 0.50 to around an inch. Ponding of water on
roads/drainage ditches possible.

Friday...convective system or clusters may still be ongoing through
mid morning, before the wave lifts north. Could have some strong
storms ongoing as well at this time around and a few hours after
sunrise despite the less then optimum time of day. Activity may then
wane into the afternoon and FCST POPs a bit high, but ongoing
southerly flow and moisture convergence may fester new development
as the afternoon progresses. High temps a challenge depending on
extent of convective debris and will do the middle of the road upper
70s to lower 80s.    ..12..

.LONG TERM...(Friday NIGHT THROUGH next Thursday)
ISSUED AT 355 PM CDT Thu May 26 2016

Active weather pattern of almost daily showers & storms the next 7
days with slightly above normal temperatures.

Long term forecast confidence assessment...slightly below average or
fair to poor with timing, coverage and intensity of precipitation
events the main issue.  American models are too moist which impacts
timing and evolution of convective events and propagation.  The most
significant impacts are subsequent events after tonight will be
very suspect.

Overview...Initialization and verification are fair with most
solutions underplaying evolution of developing complex in the
central plains.  Hi-res ECMWF slightly better suggesting a 70/30 mix
with GFS and importance of poor QPF reflection of evolution of
convective systems days 2-7.  Widespread 1 to 4+ rain amounts
expected which may result in water issues by the end of the forecast
period. Precipitable water of 1.5+ over most of the period will
ensure locally heavy rain totals will be an issue.

Friday Night...Local tools support a decent MCS event over at least
NW parts and possibly all CWA with widespread .5 to 1.5+ inches of
rain with some isolated severe of mainly bowing segments of winds to
around 60 MPH.  POPS in the likely category and lows mostly in the
middle 60s.

Saturday...lingering showers and storms with deep and fast south jet
ahead of rotating upper low in south plains moving into the upper
midwest.  Some risk of training of storms for locally higher rain
amounts of 2+ inches possible.  Highs should be mostly around 80
degrees with PM MUCAPES of 1000 to 1500 J/KG for marginal severe
risk in mostly in PM hours.

Saturday night into Sunday...Upper low to rotate northeast across
the region for a probable another convective event.  Timing most
likely for last convective event probably Saturday night with
possibly enough shear and instability for locally severe storms for
later shifts to consider as well as locally heavy rains.  Lows in
the lower 60s with highs mostly in the lower 80s.

Monday and Monday night...mostly dry with a chance of scattered
showers and storms with weak high pressure in southwesterly upper
level flow and slightly drier dewpoints.  Highs in the lower 80s
with mins in the lower 60s and possibly upper 50s.

Tuesday and Wednesday...Next upper level disturbance to impact the
region with poor confidence on timing and location of best forcing.
Large scale regime favorable for decent rains and isolated severe
once again.  Additional rain totals of 1 to locally 2 plus inches
seem reasonable which if get expected widespread rains the next 72+
hours of 1 to 2+ inches should cause water issue on some area
rivers.

Thursday and Friday...Poor confidence with best estimate of weak
high pressure moving in with little or no chance of precipitation.
Highs should be per local thermal tools mostly in the upper 70s to
around 80 or near normal for late May.  Mins mid 50s to around 60
suggested.    Nichols

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z Friday EVENING)
ISSUED AT 636 PM CDT Thu May 26 2016

A large cluster of rain and thunderstorms over western Iowa and NW
MO will likely weaken as it edges slowly east-northeastward this
evening and vicinity wording was used to convey the low confidence
in the complex affecting the terminals. Additional showers and
thunderstorms are possible much later tonight, mentioned with
prob30 groups or vicinity wording from around 09z through about
14z Friday morning. There will be chances for additional scattered
to widely scattered thunderstorms during the day Friday, but the
potential was not great enough to mention in these forecast
periods. Otherwise, VFR conditions will prevail with only brief
MVFR or IFR conditions possible with thunderstorms throughout.

&&

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

$$

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


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