Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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711
FXUS63 KDVN 261715
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1215 PM CDT Fri May 26 2017

...HYDROLOGY UPDATE...

.UPDATE...
Issued at 951 AM CDT Fri May 26 2017

MCV associated with the nocturnal convection is helping to
maintain and grow the convection moving into eastern Iowa.
Satellite trends show cloud tops cooling with lightning data
increasing, especially on the south side of the convective
complex.

The forecast has been updated to reflect higher pops associated
with the mcv as it moves across the area.

The question now becomes how much diurnal convection will develop
late this morning/afternoon with the higher cloud cover. Likewise,
the increased cloud cover then brings into question high
temperatures for today. Will continue to evaluate this but max
temps may have to be lowered for part of the area.

&&

.SYNOPSIS...
Issued at 330 AM CDT Fri May 26 2017

West-southwesterlies acrs the mid-CONUS will usher a few ridge-
rising waves through the region today and again on Saturday. These
systems may produce a few rounds of precip acrs the local area, with
warming temps in between the episodes of shower/storms. Then the
upper jet shifts for re-establishing long wave troffiness acrs the
upper Midwest into the western GRT LKS for a return to cooler temps
with occasional shower chances early next week.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Fri May 26 2017

Latest run HiRes models and 00z guidance continue to vary in
handling of incoming wave(now seen on latest water vapor loop acrs
southeastern NE-northeast KS)and precip scenario it will produce
acrs the area today. This feature producing areas of showers/
storms currently acrs northeastern KS into NW MO, but main
circulation is juts north of that activity and will continue to
roll east-northeast and follow a ridge-line acrs the central and
northern CWA from late morning into early afternoon. This wave
will encounter lingering mid and upper level ridging, as well as
fcst sounding indicated cap generally at the H7 MB level as it
chugs it`s way through the area. Thus why that a few solutions
such as the 00z NAM and NAMNEST, don`t produce much acrs the area
except some weak elevated showers or stratifying out showers with
an embedded rumble or two of thunder through mid afternoon before
the wave rolls eastward. Others, such as the 4KM WRF and HRRR runs
develop strom clusters acrs the central and southern CWA in
building CAPE fields in higher sfc DPT feed, with a few storms
possibly strong along prime convergent zone along and just south
of the I80 corridor from the Quad Cities and eastward, with these
storms then propagating east-southeast acrs west central IL into
central IL as the afternoon progresses.

Feel with lift and trajectory of the incoming vort max, will go with
a solution similar to the latest HRRR which brings remnants of the
northern portion of the upstream shower/storm cluster into the
western and southwestern CWA by mid morning, then diurnal
inflammation to more robust shower and thunderstorms from late
morning and into mid afternoon generally from the Quad Cities and
points south and southeast, including the eastern I80 corridor and
west central IL. If CAPES can get close to at least 1200 to 1500
J/KG, a locally strong storm capable of gusty wind bursts and hail
will be possible. Then of course will have to watch pre-system warm
frontal like feature and localized llvl southeasterly sfc flow and
enhanced shear in the VCNTY for and isolated weak tornado threat.
But again, hail and wind primary concerns fro any stronger storm.
Further to the north of those areas, thunder may be more embedded or
isolated with a more stratifying out shower regime. Localized heavy
downpours as well, with isolated rainfall amounts of three quarters
of an inch, to around an inch possible along paths of enhanced storm
clusters in the central and southern CWA. Otherwise most areas to
get anywhere from 0.10 to around a half inch of rainfall by late
afternoon.

High temps a challenge today as well, with cloud cover and building
inversion aloft tempering true warm up potentail. But any breaks in
cloud cover or less clouds occur than currently expected, the
airmass supports temps in the upper 70s to near 80. Will go with a
happy medium blend of low to mid 70s for most areas, with the
potentail of several spots being cooler or warmer than those values.

Tonight... the wave to progress to the east by early evening, taking
most of the precip chances with it. another bout of ridging moves
acrs tonight, with decreasing east winds and clearing skies. This
may foster some fog formation especially in areas that get some
better rainfall totals earlier in the day Friday. Hard to define
more optimum locations at this point, but feel at least patchy fog
mention worthy and will just blanket the whole area for now mainly
after 3 AM CDT.   ..12..

.LONG TERM...(Saturday through next Thursday)
ISSUED AT 330 AM CDT Fri May 26 2017

Generally slightly below normal temperatures with chances of showers
and storms mostly on Saturday.

Long Term Forecast Confidence Assessment...Fair or Average with
coverage and intensity of showers and storms on Saturday main issue.
Local forcing tools suggest best forcing and instability to our
south resulting in low or no risk of severe storms and heavy
precipitation with mostly spottier light to moderate amounts.
Temperatures in northwest flow suggest mins with light winds may be
3 plus degrees too mild.

Saturday and Saturday night...high chance to low likely POPS late PM
and evening with MUCAPE AOB 1000 J/KG.  With best forcing to our
south thus low risk of strong to severe storms possible due to
modest instability with hail to around penny size and some gusty
winds over 40 MPH mainly south of I-80. Highs 75 to 80F reasonable
if get full sunshine and mins Saturday night mostly 55 to 60F due to
clouds and lingering chances of precipitation.

Sunday through Friday...persistent northwest flow to result in fair
to mostly fair skies with low or no chances of precipitation with
surface and upper high pressure.  Highs mostly upper 60s to mid 70s
with mins mostly low to middle 50s with some upper 40s possible with
clear skies and light winds supporting good radiative cooling
conditions for favored low lying areas. This is overall about 5
degrees below average for this period.  Nichols

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
ISSUED AT 651 AM CDT Fri May 26 2017

Decaying stratiform band of showers with a little embedded
thunder will move northeast through the TAF sites this morning,
and may stay mainly VFR if it keeps in a decreasing mode. But
with a circulation still approaching the area by late morning
from the southwest, there will be the risk of more sctrd showers
and thunderstorms developing acrs the area and lasting through at
least mid to late afternoon before moving off to the east. These
showers/storms will bring passing bouts of MVFR to possibly IFR
conditions from reduced VSBYs and lowering CIGS if they can make
it over a TAF site. A stronger storm possible in the VCNTY of MLI
and BRL this afternoon. Then clearing with light northeast to east
sfc winds tonight could allow for MVFR to IFR fog to develop in
the VCNTY of most of the TAF sites after Midnight.


&&

.HYDROLOGY...
Issued at 1216 PM CDT Fri May 26 2017

Flooding is occurring, or is forecast to occur over the next week
along most sites along the Mississippi River. This is due to routed
flow from heavy rainfall that occurred in MN and WI over the past
week.

Bellevue continues to have a low confidence forecast just touching
flood stage Monday and remains in a flood watch. Dubuque Lock and
Dam 4 is forecast to touch moderate flooding, but confidence is not
high enough to change the warning to higher category flooding.
Otherwise, flood warnings for minor to moderate flooding continues
at all other sites except Keokuk.

&&

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

$$

UPDATE...08
SYNOPSIS...12
SHORT TERM...12
LONG TERM...Nichols
AVIATION...12
HYDROLOGY...Sheets



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