Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 252337
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
637 PM CDT SAT JUL 25 2015

.SYNOPSIS...
ISSUED AT 330 PM CDT SAT JUL 25 2015

FRONTAL BOUNDARY /DEWPOINT DISCONTINUITY/ EXTENDS BETWEEN HWY 30
AND I-80. MOISTURE POOLING RIGHT AHEAD WITH DEWPOINTS WELL INTO
THE 70S COMBINED WITH TEMPS NEAR 90 RESULTING IN HEAT INDEX VALUES
AROUND 100 DEGREES. ELSEWHERE...HEAT INDEX VALUES MAINLY AROUND 90
OR IN THE LOWER 90S TO THE NORTH WHERE SLIGHT DRYING IS OCCURRING
POST-FRONTAL WITH DEWPOINTS IN THE 60S... AND ALSO IN THE SOUTH
WHERE LINGERING DEBRIS CLOUDINESS HOLDING TEMPS MOSTLY IN THE MID
80S. MODERATE VERTICAL EXTENT TO CUMULUS NOTED AHEAD OF BOUNDARY
AND MONITORING FOR DEVELOPMENT OF A FEW SHOWERS OR STORMS LATE
THIS AFTERNOON. OTHERWISE...MONITORING CONVECTION OVER PORTIONS OF
SD INTO NE ATTENDANT TO PAIR OF UPPER LEVEL SHORTWAVES. EXPECT
INCREASING SHOWER AND STORM CHANCES LATE EVENING AND ESPECIALLY
OVERNIGHT-SUNDAY AS UPPER LEVEL DISTURBANCE MOVES THROUGH PORTIONS
OF THE REGION.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 330 PM CDT SAT JUL 25 2015

MODERATE CUMULUS AHEAD OF BOUNDARY BEING MONITORED FOR SOME
CONVECTIVE DEVELOPMENT LATE THIS AFTERNOON. ENVIRONMENT IS
CHARACTERIZED BY HIGH TO EXTREME INSTABILITY WITH MLCAPE AND
SBCAPE OF 3500-5000 J/KG... BUT SHEAR IS FAIRLY WEAK WITH 0-6KM
BELOW 25-30 KTS. SHOULD A STORM DEVELOP HOWEVER GIVEN MAGNITUDE
OF INSTABILITY CANT RULE OUT AN ISOLATED SEVERE STORM WITH STRONG
WINDS BEING THE MAIN CONCERN WITH ALSO POTENTIAL FOR LOCALLY HEAVY
RAIN DUE TO SLOWER STORM MOTION AND PRECIPITABLE WATER VALUES IN
EXCESS OF 1.5 INCHES.

TONIGHT...TWO AREAS OF STORM DEVELOPMENT AND POTENTIAL UPSCALE
GROWTH TO MCS EXIST OVER THE PLAINS. ONE EXISTS ACROSS PORTIONS
OF KS/MO... WITH THE OTHER OVER PORTIONS OF SD ATTENDANT TO
APPROACHING STRONGER MID LEVEL SHORTWAVE AND MID LEVEL WARM
ADVECTION. SHOULD THIS ACTIVITY GROW UPSCALE INTO MCS TONIGHT
THEN WOULD ANTICIPATE EVENTUAL PROPAGATION TO SOUTHEAST ON
PERIPHERY OF 850 MB MOISTURE AND THERMAL GRADIENT. THERE IS SOME
UNCERTAINTY ON TRACK AS WEAK 850 MB RIDGING THIS EVENING INTO
THE OVERNIGHT MAY RETARD EASTWARD MOVEMENT AND TAKE BRUNT OF THE
ORGANIZED CONVECTION TO OUR SOUTHWEST. HOWEVER...IF STORMS
TAKE LONGER TO GROW UPSCALE THEN MORE TIME FOR RIDGE TO MOVE
EAST ALLOWING FAVORABLE TRACK ACROSS THE SOUTHWEST THIRD TO
POSSIBLY ONE HALF OF CWA LATE TONIGHT INTO SUNDAY AM. THIS WOULD
BE GRADUAL WEAKENING STAGES WHEN ARRIVING WITH LIMITED SEVERE
RISK. WITH PRECIPITABLE WATER VALUES IN EXCESS OF 1.5 INCHES
WOULD PRESENT POTENTIAL FOR HEAVY RAIN 1-2 INCHES AND THIS COULD
BRING SOME RISK OF LOCALIZED FLASH FLOODING TO SOUTHEAST IA AND
NORTHEAST MO WHERE SOME AREAS HAVE SEEN ALREADY 1-2 INCHES IN THE
PAST 24 HRS. HOWEVER...DUE TO UNCERTAINTY ON UPSCALE POTENTIAL AND
TRACK HAVE OPTED TO HOLD ON FLASH FLOOD WATCH FAR SOUTH BUT PASS
ON TO EVENING SHIFT TO MONITOR TRENDS. AS FOR LOWS TONIGHT...
60S NORTH POST FRONTAL WITH MUGGY 70S TO THE SOUTH. IF WINDS LIGHT
FAR SOUTH THEN CANT RULE OUT SOME FOG DUE TO RECENT RAINFALL.

SUNDAY...POTENTIAL FOR MORE WIDESPREAD SHOWER AND STORM ACTIVITY
SOUTHWEST THIRD TO HALF GRADUALLY WEAKENING... WITH ADDITIONAL
SHOWER AND STORMS AT LEAST SCATTERED COVERAGE ELSEWHERE AS
SHORTWAVE MOVES THROUGH...BUT DEPENDING ON TRENDS TONIGHT POPS
MAY NEED TO BE ADJUSTED UPWARD CENTRAL AND NORTH. TEMPS WILL BE
CHALLENGING DUE TO DEBRIS CLOUDS AND PRECIP. HAVE NUDGED DOWN
A BIT MOST AREAS WITH GENERAL MID 80S... BUT COULD BE LOWER IN
SOME LOCATIONS WHERE CLOUDS AND RAIN LINGER.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 330 PM CDT SAT JUL 25 2015

MAIN FORECAST CONCERN FOR THE LONG TERM ARE THE CHANCES FOR PRECIP
THROUGH TUESDAY....ALONG WITH HIGH TEMPERATURES AND POSSIBLE HEAT
ADVISORY CRITERIA.  AFTER A COLD FRONT MOVES THROUGH ON TUESDAY...WE
SEE A CHANGE IN THE WEATHER PATTERN TO A MORE COOLER...DRIER WEATHER.

SUNDAY NIGHT...DIURNAL CONVECTION WILL LIKELY BE ONGOING ACROSS THE
AREA AT 00Z. AT THE SAME TIME...H5 RIDGING BUILDS INTO THE AREA.  AT
THE SURFACE MODELS TRY TO ADVECT A FRONTAL BOUNDARY INTO THE CWA.
THIS LEADS TO A CHANCE OF POPS THROUGH 06Z UNTIL THE RIDGE CAN
MAKE IT INTO THE AREA. THINK THAT THE SFC BOUNDARY WILL NOT MAKE
MUCH OF A PUSH UNTIL LATER AND WILL BE SOUTH ACROSS THE IA/MO
LINE. CHANCES OF CONVECTION SHOULD WANE AFTER 00Z AS DIURNAL
PROCESSES CEASE. THERE IS A SLIGHT CHANCE OF AN MCS DEVELOPING AND
MOVING ACROSS THE AREA. HOWEVER WITH H5 RIDGING...BELIEVE THAT
DEVELOPMENT WILL BE DIFFICULT.

ON MONDAY THE WARM FRONT SHOULD BEGAN TO MOVE NORTH THROUGH THE CWA.
AT THIS TIME WARM H7 TEMPS MAY HELP TO LIMIT OVERALL COVERAGE OF
CONVECTION AS THE FRONT MOVES NORTH.  AS SUCH HAVE KEPT POPS AT
SLIGHT CHANCE. TEMPS COULD BE WARM AND NEED TO BE MONITORED FOR
POSSIBLE HEAT HEADLINES. WITH THE BOUNDARY IN PLACE ACROSS THE
AREA...HAVE KEPT SLIGHT CHANCE POPS IN. TUESDAY AFTERNOON EVEN
HIGHER H7 TEMPS MOVE IN. THIS WILL EFFECTIVELY CAP US TUESDAY. THE
HEAT DOME SHOULD BUILD. TUESDAY COULD BE ONE OF THE HOTTER DAYS OF
THE YEAR. TUESDAY NIGHT A ROBUST WAVE AND COLD FRONT WILL MOVE
INTO THE AREA. THUNDERSTORMS AND RAIN ARE POSSIBLE WITH THIS
FRONT. AT THIS TIME...DEEP LAYER SHEAR LOOKS WEAK...SO THE THREAT
FOR ORGANIZED CONVECTION LOOKS LOW. PWATS WILL BE CLOSE TO IF NOT
2 INCHES PRECEDING THE FRONT. HEAVY RAIN CANNOT BE RULED OUT FOR
THIS SYSTEM.

WEDNESDAY ON...THE FLOW SHOULD TURN NW.  THIS SHOULD LEAD TO QUIET
WEATHER WITH DRIER AIR AND COOLER TEMPS FOR THE END OF THE WORK
WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 637 PM CDT SAT JUL 25 2015

THUNDERSTORMS ALONG A WEAK SURFACE BOUNDARY OVER EASTERN IOWA
INTO NORTHERN ILLINOIS WILL DISSIPATE AND NOT AFFECT THE TAF SITES
THIS EVENING. OTHERWISE...WINDS WILL REMAIN LIGHT AND MAINLY
NORTHERLY OVERNIGHT WITH LIGHT FOG DEVELOPING DUE TO THE HIGH
MOISTURE LEVELS RESULTING IN MVFR CONDITIONS AFTER MIDNIGHT.
THERE IS A GOOD CHANCE FOR ADDITIONAL THUNDERSTORM COMPLEXES
SUNDAY...BUT CONFIDENCE REMAINS LOW IN THE TIMING AND COVERAGE.
AT THIS TIME...THE MOST LIKELY ONSET OF THUNDERSTORM CHANCES IS
FROM MID MORNING ONWARD...EXCEPT AT BRL...WHERE THUNDERSTORMS WILL
BE POSSIBLE AS EARLY AS SUNRISE. THESE CHANCES HAVE BEEN LIMITED
TO PROB30 MENTION FOR NOW DUE TO THE LOW FORECAST CONFIDENCE.

&&

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

$$

SYNOPSIS...05
SHORT TERM...05
LONG TERM...GIBBS
AVIATION...SHEETS


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