Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 252030
AFDDVN

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

.SYNOPSIS...
ISSUED AT 245 PM CDT SAT JUL 25 2015

FRONTAL BOUNDARY /DEWPOINT DISCONTINUITY/ EXTENDS BETWEEN HWY 30
AND I-80. MOISTURE POOLING RIGHT AHEAD WITH DEWPTS 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 305 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 ADUSTED 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 305 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 CHC 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
SCHC.  TEMPS COULD BE WARM AND NEED TO BE MONITORED FOR POSSIBLE
HEAT HEADLINES.  WITH THE BOUNDARY IN PLACE ACROSS THE AREA...HAVE
KEPT SCHC 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 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1241 PM CDT SAT JUL 25 2015

AN UPPER LEVEL DISTURBANCE AND FRONTAL BOUNDARY DRAPED ACROSS THE
AREA WILL SERVE AS THE FOCUS FOR CHANCES OF SHOWERS AND STORMS
MAINLY LATER THIS EVENING THROUGH SUNDAY MORNING. UNCERTAINTY
EXISTS AS TO COVERAGE WHICH IS LARGELY RELATED TO WHETHER OR NOT
THE CONVECTION IN THE PLAINS GROWS UPSCALE INTO AN ORGANIZED
COMPLEX OF STORMS. THUS...HAVE LIMITED PRECIP MENTION TO ONLY
PROB30 GROUPS FOR NOW AT MOST SITES HIGHLIGHTING MOST FAVORED
TIMING OF LATE TONIGHT INTO SUNDAY MORNING. HOWEVER AT BRL SIDED
TOWARD TEMPO GROUP WHERE BETTER SIGNAL FOR PRECIP EXISTS WITH
FRONT AND ALSO BEING MOST FAVORED LOCATION FOR TRACK SHOULD
ORGANIZED CONVECTION DEVELOP. ANTICIPATE CONDITIONS TO LOWER INTO
MVFR TO IFR IN FOG AND PRECIPITATION LATE TONIGHT AND SUNDAY
MORNING. LIGHT NORTHERLY WINDS EXPECTED TO VEER EASTERLY TONIGHT
INTO SUNDAY MORNING.


&&

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

$$

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


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