Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 241737
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1237 PM CDT FRI JUL 24 2015

.UPDATE...
ISSUED AT 921 AM CDT FRI JUL 24 2015

HAVE UPDATED THE FORECAST TO INCREASE POPS SIGNIFICANTLY THIS
MORNING ACROSS THE HIGHWAY 20 CORRIDOR AND SOUTHWARD ALONG THE
WESTERN COUNTY WARNING AREA BORDER. STRONGEST STORMS CONTINUE TO
BACKBUILD IN N CENTRAL IA ALONG THE BETTER ELEVATED MOISTURE
INFLOW TO THE WEST WITH SHORT TERM CONVECTIVE MODELS SUGGESTING
THIS PROCESS MAY CONTINUE WITH STORMS PROGRESSING S-SE THROUGH THE
MORNING WEST OF AN INDEPENDENCE TO WASHINGTON LINE ALONG THE
MUCAPE AND ELEVATED MOISTURE GRADIENT. EAST OF THIS LINE...
CLOUDS...RAIN AND A FEW LIGHTNING STRIKES APPEAR TO BE THE MAIN
IMPACTS.

&&

.SYNOPSIS...
ISSUED AT 352 AM CDT FRI JUL 24 2015

SEVERAL LINES OF CONVECTION WAS OCCURRING ACROSS MN AS FAR SOUTH
AS THE MN/IA BORDER NORTH OF ALGONA. MUCH OF THIS ACTIVITY WAS
MOVING DUE EAST AND WAS LINED UP WITH THE MOIST AXIS WHERE PWAT`S
WERE NEAR 2 INCHES...ALONG WITH THE STRONGEST LOW LEVEL MOISTURE
TRANSPORT.

3 AM TEMPERATURES ACROSS THE DVN CWA WERE IN THE 60S WITH CIRRUS
BLOWOFF FROM THE MN CONVECTION STREAMING SOUTHEAST INTO THE CWA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 352 AM CDT FRI JUL 24 2015

FORECAST FOCUS ON WARM AND MORE HUMID CONDITIONS WITH A CHANCE OF
THUNDERSTORMS.

TODAY...A STRENGTHENING CAP AND CONVECTIVE TEMPERATURES OF 100
DEGREES WILL ESSENTIALLY SUPPRESS CONVECTION. OPERATIONAL MODELS
ARE DRY TODAY EXCEPT FOR THE FAR NW CWA. THE HRRRX MESO MODEL
TAKES THE MCS ALONG THE IA/MN BORDER SOUTHEAST INTO OUR FAR NW
LATER THIS MORNING...BUT IN A DECAYING FASHION. AS OF NOW THE
CONVECTION WAS MOVING MAINLY EAST SO WILL MONITOR RADAR TRENDS.
I WILL HAVE SMALL POPS TODAY IN OUR FAR NW IN CASE THE HRRRX IS
RIGHT. FORECAST SOUNDINGS INDICATE VERY LITTLE MIXING WITH WEAK
WINDS SO THIS SHOULD KEEP TEMPERATURES IN CHECK...DESPITE 850 MB
TEMPERATURES PUSHING TO 20+C. FOR NOW I WILL HAVE AFTERNOON HIGHS
IN THE RANGE OF 85 TO 90. DEWPOINTS WILL GRADUALLY CREEP UP INTO
THE UPPER 60S TO LOWER 70S THIS AFTERNOON...POSSIBLY MID 70S IN
OUR FAR WEST. HEAT INDEX VALUES WILL PUSH INTO THE MID TO UPPER
90S IN THE FAR SW COUNTIES.

TONIGHT...LOW CONFIDENCE IN CONVECTIVE TRENDS WITH THE
ECMWF/CANADIAN-NH IS MAINLY DRY WHILE THE GFS/NAM IS WETTER.
FORECAST SOUNDINGS INDICATE A DECENT CAP WITH THE MCS GENERATION
TOOL SUGGESTING THE BETTER FORCING IS IN OUR FAR SW CWA. FOR NOW I
WILL HAVE 30 TO 40 POPS AND HOPEFULLY THE MODELS WILL COME INTO
BETTER AGREEMENT. NONETHELESS...THIS WILL BE A WARMER AND MUGGIER
NIGHT COMPARED TO THE PAST SEVERAL NIGHTS. LOWS SHOULD BOTTOM OUT
AT AROUND 70 AT MOST LOCATIONS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 352 AM CDT FRI JUL 24 2015

SATURDAY...LOW PRESSURE TRACKING THROUGH WESTERN ONTARIO WILL
DRAG A WEAK COLD FRONT INTO E IOWA/W ILLINOIS BY MIDDAY. ISOLATED
TO SCATTERED SHOWERS/THUNDERSTORMS WILL LIKELY BE ASSOCIATED WITH
THE FRONT BUT WIDESPREAD ACTIVITY IS NOT FORECAST.

CONVECTIVE POTENTIAL...ENVIRONMENTAL SETUP SUGGESTS ISOLATED
STRONG OR SEVERE STORMS ARE POSSIBLE BUT MESOSCALE DETAILS REMAIN
UNCLEAR. INSTABILITY WILL BE MODERATE TO HIGH BUT SHEAR WILL BE
LOW AND FORCING FOR ASCENT WILL BE WEAK. 850MB WINDS ARE FORECAST
TO BE VERY LIGHT THROUGH THE DAY...WHICH FURTHER SUPPORTS THE
ISOLATED STORM SCENARIO. THE NOCTURNAL LLJ DOES STRENGTHEN
SATURDAY NIGHT AND COULD IGNITE A CONVECTIVE COMPLEX OVER SOUTH
DAKOTA/NEBRASKA/W IOWA...POSSIBLY APPROACHING E IOWA/W ILLINOIS
LATE AT NIGHT INTO SUNDAY MORNING.

HIGH HEAT INDICES...LOW-LEVEL WAA WILL INCREASE 850MB TEMPS INTO
THE LOWER TO MIDDLE 20S CELSIUS RANGE. DEWPOINTS WELL INTO THE 70S
AND TEMPS IN THE UPPER 80S TO POSSIBLY LOWER 90S FAR SOUTH EQUATES
TO SATURDAY AFTN HEAT INDICES PEAKING BETWEEN 95-105 F ON AVG. IT
WILL FEEL VERY HUMID AND HEAT ADVISORIES WILL MOST LIKELY BE
NECESSARY OVER ROUGHLY THE SOUTHERN TWO-THIRDS OF THE DVN CWA.

SUNDAY...APPEARS THE BEST CHANCE FOR SHOWERS AND THUNDERSTORMS
ACROSS THE FORECAST WILL OCCUR ON SUNDAY. HAVE 50-60 POPS ACROSS THE
AREA...THE 60 POPS ARE FOCUSED OVER THE SOUTHERN TWO-THIRDS OF THE
CWA. LOWERED TEMPS A FEW DEGREES BELOW CONSENSUS BECAUSE OF MORE
WIDESPREAD CLOUD COVER FORECAST COMPARED TO SATURDAY...HIGHS ARE
FORECAST TO BE IN THE LOWER TO MIDDLE 80S FOR MOST OF THE CWA.

CONVECTIVE POTENTIAL...SYNOPTICS ARE WEAK BUT MODELS ARE SHOWING
A SUBTLE SHORTWAVE TROUGH/VORTICITY MAX EMERGING FROM THE CENTRAL
PLAINS THEN TRACKING INTO MN/IA/WI/IL BY THE MORNING...POSSIBLY
LINGERING INTO THE EVENING. A SLIGHTLY MORE ORGANIZED 850MB
HEIGHT GRADIENT WILL LEAD TO A STEADIER 850MB FLOW/WAA AND A QUASI-
STATIONARY SFC FRONT MAY STILL BE DRAPED FROM NW TO SE THROUGH E
IOWA/W ILLINOIS BOTH OF WHICH WOULD PROVIDE SOME ADDITIONAL FORCING
FOR ASCENT. LATEST SPC OUTLOOK FOR SEVERE STORMS IS A MARGINAL RISK
FOR SEVERE STORMS. HOWEVER...THE BALANCE OF SHEAR/INSTABILITY MAY
WARRANT AN UPGRADE OF THIS OUTLOOK IN FUTURE UPDATES...SOMETHING TO
MONITOR TODAY/TONIGHT.

MONDAY...FORECAST HIGHS ARE IN THE MID 80S/UPPER 80S. CHANCES FOR
SHOWERS/STORMS ARE ONLY BETWEEN 20-30 PERCENT...MOST AREAS WILL
LIKELY REMAIN DRY THROUGH THE DAY.

TUESDAY...UNSEASONABLY STRONG UPPER LOW DEVELOPING ACROSS
SASKATCHEWAN/MANITOBA/ONTARIO WOULD PULL VERY WARM AIR ALOFT OVER
THE MIDWEST...SETTING UP ANOTHER DAY OF HIGH HEAT INDICES. BOTH THE
GFS/ECMWF HAVE 1000-500MB THICKNESSES ABOVE 582 DAM.

WEDNESDAY AND THURSDAY...QUIET PERIOD AS HIGHS FALL INTO THE LOWER
TO MIDDLE 80S AND DEWPOINTS DROP INTO THE 60S.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1237 PM CDT FRI JUL 24 2015

CLUSTER OF THUNDERSTORMS DROPPING SOUTH THROUGH EAST CENTRAL IA
WILL MOVE OUT OF CID AND DBQ EARLY AFTERNOON...AFFECTING MLI AND
BRL WITH WEAKER SHOWERS AND ISOLATED THUNDERSTORMS AROUND MID
AFTERNOON. OTHERWISE...LIGHT WIND FIELDS WILL EXIST WITH VFR
CONDITIONS. THERE IS A LOW POTENTIAL FOR ADDITIONAL THUNDERSTORMS
TONIGHT THROUGH SATURDAY MORNING AS A WEAK SURFACE FRONT MOVES
THROUGH...BUT WITH A HIGH LEVEL OF UNCERTAINTY AND EXPECTED LOW
COVERAGE...THESE ARE NOT MENTIONED IN THE FORECASTS. INCREASING
LOW LEVEL MOISTURE WILL LIKELY LEAD TO AT LEAST MVFR FOG INCLUDED
AT ALL SITES FOR THE OVERNIGHT PERIOD.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...HAASE
SHORT TERM...HAASE
LONG TERM...UTTECH
AVIATION...SHEETS



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