Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 200141
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
841 PM CDT TUE AUG 19 2014

.SYNOPSIS...
ISSUED AT 329 PM CDT TUE AUG 19 2014

AT 19Z A WEAK COLD FRONT WAS EVIDENT IN SURFACE WIND AND CUMULUS
FIELDS ROUGHLY FROM NEAR KRAC ON LAKE MI W-SW THROUGH KRFD SW TO
JUST EAST OF MOLINE TO NEAR MEMPHIS MO. KDVN SHOWED THIS BOUNDARY
WAS BEGINNING TO LIGHT UP WITH SCATTERED SHOWERS AND THUNDERSTORMS
DEVELOPING ALONG THIS BOUNDARY...MAINLY FROM THE MLI AREA
SOUTHWARD...WITH AN ISOLATED CELL NORTH OF FREEPORT. SLIGHTLY COOLER
AND DRIER AIR WAS FLOWING SOUTHEAST INTO THE AREA BEHIND THIS
BOUNDARY...RESULTING IN DEWPOINTS LOWERING FROM THE MID 60S TO NEAR
70 AHEAD OF THE FRONT TO LOWER AND MID 60S IN ITS WAKE. IN THE UPPER
LEVELS...LOW PRESSURE WAS OVER LAKE SUPERIOR...WHILE A RIDGE AXIS
REACHED FROM NM INTO THE HIGH PLAINS. FURTHER WEST...LOW PRESSURE
WAS OFF THE COAST OF CA...WITH A RESULTING MONSOONAL FLOW INTO THE
ROCKIES.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 329 PM CDT TUE AUG 19 2014

IN THE IMMEDIATE SHORT-TERM...HAVE UPDATED TO GO WITH CHANCE POPS
FOR LATE AFTERNOON INTO EARLY EVENING AS CONVECTIVE TEMPERATURES
HAVE BEEN REACHED AND THE CONVECTION WAS BEGINNING TO FIRE AHEAD
OF THE SLOW MOVING FRONT. BASED ON MUCAPES ABOVE 3000 J/KG AND
0-3 KT SHEAR APPROACHING 30 KTS...SOME OF THESE STORMS COULD
BRIEFLY APPROACH SEVERE LIMITS SOUTH OF A BURLINGTON TO PRINCETON
LINE LATE THIS AFTERNOON AS THE FRONT PUSHES EASTWARD. AFTER THIS
PERIOD...MOSTLY CLEAR AND QUIET CONDITIONS ARE EXPECTED OVERNIGHT
AS SUBSIDENCE BUILDS IN UNDER A WEAKLY CONFLUENT MID LEVEL FLOW
AND THE WEAK SURFACE RIDGE MIGRATING IN FROM THE PLAINS.

WITH THIS WEAK RIDGE AXIS OVERHEAD TOWARD SUNRISE...THE ASSOCIATED
LIGHT WINDS AND LINGERING LOW LEVEL MOISTURE MAY AGAIN LEAD TO AT
LEAST PATCHY FOG...WHICH HAS BEEN INCLUDED IN THE FORECAST.
HOWEVER...CONDITIONS DO NOT APPEAR FAVORABLE FOR DENSE FOG DUE TO
THE DECENT AMOUNT OF MIXING TODAY AND CONTINUED ADVECTION OF A
DRIER LOW LEVEL AIRMASS SEEN ON UPSTREAM SOUNDINGS AT 12Z THIS
MORNING. THE DRIER AIR SHOULD LEAD TO COOLER OVERNIGHT LOWS...FROM
THE LOWER 60S NORTH TO MID 60S SOUTH.

LATE TONIGHT...THE WESTERN EXTENSION OF THE SURFACE BOUNDARY
BEGINS TO LIFT BACK NORTH NORTHEAST WITH AN AREA OF ELEVATED
THETAE CONVERGENCE REACHING THE EXTREME SOUTHWEST TOWARD SUNRISE.
HAVE INCLUDED LOW CHANCES FOR SHOWERS AND THUNDERSTORMS
THERE...SPREADING NORTHEAST AS LOW CONFIDENCE...SLIGHT CHANCES
DURING THE DAY WEDNESDAY. LIGHT SOUTHERLY WINDS AND WEAK LOW LEVEL
CONVERGENCE SHOULD BRING BACK HIGHER HUMIDITY DURING THE DAY WITH
HIGHS SIMILAR TO TODAY IN THE LOWER TO MID 80S.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 329 PM CDT TUE AUG 19 2014

THERE MAY OR MAY NOT BE SOME ISOLATED CONVECTION ACROSS THE AREA
WEDNESDAY EVENING. THE FORCING IS QUITE WEAK SO THE POSSIBILITY DOES
EXIST THAT THE EVENING HOURS WILL REMAIN DRY.

AFTER MIDNIGHT...THE MODELS ARE SUGGESTING A POTENTIAL THUNDERSTORM
COMPLEX MOVING ACROSS ROUGHLY THE NORTHEAST TWO THIRDS OF THE AREA.
THERMALLY THE AREA IS FAVORED BUT RECENT MODEL TRENDS HAVE BEEN TO
DEVELOP THIS COMPLEX A BIT FURTHER NORTH. IF A THUNDERSTORM COMPLEX
DOES DEVELOP AND MOVE INTO THE AREA IT WOULD BE DURING THE PRE-DAWN
HOURS.

IF THE NOCTURNAL THUNDERSTORM COMPLEX FROM WEDNESDAY NIGHT DOES
AFFECT THE AREA...IT WOULD DISSIPATE ACROSS THE AREA THURSDAY
MORNING. ANY BOUNDARIES FROM THIS COMPLEX WOULD PROVIDE THE FOCUS
FOR DIURNAL CONVECTION THURSDAY AFTERNOON. HOWEVER...FORCING
THURSDAY AFTERNOON IS QUITE WEAK SO ANY CONVECTION WOULD BE ISOLATED.

THURSDAY NIGHT INTO FRIDAY THE MODELS ARE AGAIN SUGGESTING A
NOCTURNAL THUNDERSTORM COMPLEX DEVELOPING AND MOVING ACROSS THE AREA
AND DECAYING ON FRIDAY. THE OVERALL FORCING IS STRONGER AND
DEPENDING UPON WHERE THIS COMPLEX FORMS...THE NORTHERN HALF OF THE
AREA WOULD BE MORE FAVORED FOR ANY RAIN.

FRIDAY NIGHT ON...
THE MODEL CONSENSUS HAS SLIGHT CHANCE TO CHANCE POPS IN EACH PERIOD
FROM FRIDAY NIGHT THROUGH TUESDAY.

THE LARGE SCALE ATMOSPHERIC FEATURES INDICATED BY THE MODELS
SUGGESTS AN UNSETTLED WEATHER PATTERN. HOWEVER...THE PATTERN ALSO IS
SUGGESTING WARMER THAN NORMAL TEMPERATURES. SO WHILE THE CHANCE OF
RAIN IS NOT ZERO FROM FRIDAY NIGHT THROUGH TUESDAY...THERE WILL BE
MANY PERIODS OF DRY WEATHER WHICH COULD BE SIX OR TWELVE HOURS IN
LENGTH.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 837 PM CDT TUE AUG 19 2014

EXPECTING MVFR TO IFR VISIBILITIES IN FOG TO DEVELOP OVERNIGHT.
BEST POTENTIAL FOR DENSE FOG AND LOWER VISIBILITIES AT KBRL DUE TO
RECENT RAIN AND MORE FAVORABLE LOW LEVEL MOISTURE.

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...08
AVIATION...RP KINNEY






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