Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KDVN 241814
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
114 PM CDT SUN JUL 24 2016

.UPDATE...
Issued at 110 PM CDT Sun Jul 24 2016

At 1 pm the cold front extended from Dubuque to Ottumwa marked by
a band of low stratus and northwest winds behind the front. Ahead
of the front winds were still a bit southerly east of the MS
River. This would be the area that still has a chance for convection
to develop, where the somewhat better low level convergence
exists. In fact, SPC has placed Bureau and Putnam counties in a
slight risk for severe storms, with the main threat damaging
winds, especially considering SBCAPES of 6000 J/KG in northern IL.
However, coverage of storms is in question. The HRRR has been
consistent the past several hours indicating a line of intense
storms moving through southern WI/northern IL this afternoon, with
the western end of the line pushing southward across our far
eastern cwa. Indeed, a line of showers was trying to get started
west of Madison, WI. So, it`s a race between the front continuing
to push eastward and the convection trying to develop ahead of the
front. Will continue to monitor trends.

UPDATE Issued at 1012 AM CDT Sun Jul 24 2016

Cold front was just entering our far nw cwa nearing Independence
and was marked by a band of low stratus near and behind the front,
and northwest winds. Ahead of the front, very warm and humid
conditions existed with 10 am temperatures in the 80s with
dewpoints well into the 70s to near 80. Heat index values were in
the 90s to 103 at many locations, so the heat headlines look good.

Concerning convection: Beginning to look much less favorable for
convection to form with the cold front. Capped atmosphere, 850 mb
moisture transport was from the west, surface winds were veering
southwest, bulk shear was very weak, CAPE gradient was in northern
IL, and water vapor loops show drying spreading in from the west.
Still can`t rule out isolated storms but some of the models are
keying on southern WI/northeast IL for the bulk of the storms
later today. We will continue to monitor.

&&

.SYNOPSIS...
Issued at 330 AM CDT Sun Jul 24 2016

The latest SFC analysis was indicating a cool front acrs central mn
extending back acrs the MO RVR valley and into western KS.
Associated warm front was making a little push northward from
southwestern MN into far northwestern IL. Mid to upper 70 SFC DPTs
away from earlier rain cooled areas were pooling acrs the CWA. SFC
based CAPE was pushing 3500 J/KG acrs southeastern IA but was
currently capped off. Aloft, the current water vapor loop was
indicating a digging upper level wave over southern Manitoba, with a
secondary vort max acrs central MN embedded in cyclonic flow putting
the squeeze on the upper ridge periphery acrs the upper MS RVR
Valley.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 330 AM CDT Sun Jul 24 2016

Today...With all the SFC moisture out there, will have to watch for
at least patchy fog through sunrise. The other thing will be the AC
field seen on the IR imagery acrs northeastern IA ahead of the front
currently in NW IA. With some signs of at least subtle H85 MB
moisture advection and convergence into these areas through 14z to
15z, will keep slight CHC POPs acrs the northwestern into northern
CWA the first half of the morning. The majority of the models are
dry this morning, but a few develop at least isolated elevated
showers and storms in these areas. Will then walk slight to low CHC
POPs east and southeast acrs the rest of the CWA during the rest of
the day as the front sags thru the local forecast area. With a
thermal cap to deal with and marginal frontal convergence, there may
not be much development along this feature during the day, but if a
storm cell could initialize and become surface based with all the
available CAPE/buoyancy and frontal vcnty shear, could easily see a
severe storm develop as well as produce locally torrential rainfall.
Best convective chances may come late in the day acrs the far
eastern CWA...tailing back southwestward into far southeastern IA
and NE MO.

Now for another round of heat. Barring too much convective debris
and cloud cover, have highs around 90 to the lower 90s along and
ahead of the incoming front. These kind of ambient temps as well as
SFC DPTs pooling ahead of the front in the upper 70s to around 80
drive heat index readings back to 100 to 108 or so. The highest
values expected along and east of the MS RVR up into Whiteside
County. Taking into account the accumulative effect of high heat and
humidity the past three plus days, will go with another Excessive
Heat Advisory along and pre-frontal for much of the southeastern two
thirds of the DVN CWA. As for other areas more supportive of heat
advisory conditions as well as neighboring office coordination, will
go with an advisory for Clinton and Jackson Co`s IA into far NW IL
from late morning through early evening.

Tonight...With some signs of at least marginal nocturnal convergence
along the front, will keep low to moderate CHC POPs going acrs the
southern third to quarter of the CWA tonight in the vcnty of the
frontal boundary. Marginal severe storm threat along with locally
heavy rain remain factors in these areas into the overnight. to the
northwest, post-frontal cooling and drier sfc DPT advection to bring
about lows in the mid 60s in at least the northwestern third of the
area.   ..12..

.LONG TERM...(Monday through next Saturday)
ISSUED AT 330 AM CDT Sun Jul 24 2016

High pressure will provide more benign weather to start out the work
week, with a break from thunderstorms along with lower humidity and
near normal temperatures. From midweek into next weekend, a
developing active NW flow aloft will return daily chances for
thunderstorms.

Monday and Tuesday: High pressure rolling through the area will
bring in a more continental airmass. High low level moisture levels
from recent rainfall and mature crops will keep dewpoints at least
in the 60s. This may lead to fog due to light winds and clear skies
under the high Monday night and early Tuesday morning, which is not
currently mentioned, but will need to be considered in later
forecasts. Stayed near a guidance blend with highs from the mid 80s
north to upper 80s south.

Will continue a several day stretch of low confidence thunderstorm
chances Wed through Sat, based on a blend of models with slightly
different timing of shortwaves and frontal systems in this period.
After a minor mid week warming trend, highs are shown trending
slightly cooler late week into the weekend with upper 70s to lower
80s and lows back into the lower to mid 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 110 PM CDT Sun Jul 24 2016

MVFR conds at KCID/KDBQ behind a cold front that at 18z extended
from just east of KDBQ to KOTM and was moving eastward. By late
afternoon conds should become VFR at all taf sites, continuing
through Monday. Any convection that forms ahead of the front
should develop across northern IL. Southwest winds becoming
northwest to north with the frontal passage, with speeds of around
10 knots or less.

&&

.DVN Watches/Warnings/Advisories...
IA...Heat Advisory until 7 PM CDT this evening for Clinton-Jackson.

     Excessive Heat Warning until 7 PM CDT this evening for Des
     Moines-Henry IA-Jefferson-Lee-Louisa-Muscatine-Scott-Van
     Buren-Washington.

IL...Heat Advisory until 7 PM CDT this evening for Carroll-Jo Daviess-
     Stephenson.

     Excessive Heat Warning until 7 PM CDT this evening for Bureau-
     Hancock-Henderson-Henry IL-McDonough-Mercer-Putnam-Rock
     Island-Warren-Whiteside.

MO...Excessive Heat Warning until 7 PM CDT this evening for Clark-
     Scotland.

&&

$$

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


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.