Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 211752
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1252 PM CDT MON APR 21 2014

.UPDATE...
ISSUED AT 627 AM CDT MON APR 21 2014

RADAR TRENDS INDICATES THE ATMOSPHERE IS SLOWLY MOISTENING. WHERE
CONVECTION HAS DEVELOPED/PERSISTED OVERNIGHT...DEW POINTS ARE IN
THE 50S. AREAS THAT ARE DRY GENERALLY HAVE DEW POINTS IN THE 40S.

BASED ON CURRENT RADAR/MOISTURE TRENDS...THE BETTER PRECIPITATION
CHANCES WILL BE OVER THE NORTHWEST THIRD TO 40 PERCENT OF THE
AREA. HOWEVER...BASED ON THE NOW DISSIPATING CELL THAT DEVELOPED
SOUTHWEST OF THE QUAD CITIES...ANY RESPECTABLE FORCING ACTING ON A
LAYER OF ELEVATED MOISTURE SHOULD BEGIN DEVELOPING SHOWERS. THUS
NEW CONVECTION COULD BEGIN DEVELOPING AT ANY TIME THIS MORNING
FURTHER EAST.

THE BETTER CHANCES FOR CONVECTION AND THUNDERSTORMS STILL LOOK TO
BE MAINLY DURING THE AFTERNOON HOURS. THE BETTER CONVECTION WILL
BE ASSOCIATED WITH THE COLD FRONT BUT SCATTERED CONVECTION AHEAD
OF THE FRONT CANNOT BE RULED OUT.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 309 AM CDT MON APR 21 2014

CONVECTION OVERNIGHT HAS BEEN MAINLY CONFINED TO THE FRONTAL ZONE
NORTH OF THE AREA. HOWEVER...NEW CONVECTION HAS DEVELOPED IN THE
UNSTABLE AIR ACROSS IOWA AND MISSOURI WHERE DEW POINTS WERE IN THE
50S. RADAR DOES SHOW CONSIDERABLE VIRGA ACROSS SOUTHEAST IOWA INTO
WESTERN ILLINOIS.

BASED ON THE OVERALL SYNOPTIC SET UP...NEW CONVECTION THAT HAS
DEVELOPED WEST OF A KIIB TO KOTM LINE SHOULD BECOME MORE WIDESPREAD
IN COVERAGE THROUGH SUNRISE. SO AREAS WEST OF A KDBQ TO KIRK LINE
HAVE THE BEST CHANCE AT SEEING SOME RAIN BY SUNRISE.

DAYTIME HEATING IS EXPECTED TO ALLOW THE CONVECTION TO PERSIST AND
BECOME MORE WIDESPREAD DURING THE MORNING HOURS. THE EXTREME EASTERN
PARTS OF THE CWFA MAY REMAIN DRY THROUGH MID DAY.

WHEN THE COLD FRONT SWEEPS THROUGH THE AREA THIS AFTERNOON...
CONVECTION SHOULD BE THE MOST PROMINENT ALONG WITH THUNDERSTORMS. A
SOMEWHAT BROKEN LINE OF CONVECTION SHOULD DEVELOP ALONG THE COLD
FRONT WITH MORE SCATTERED CONVECTION AHEAD OF IT. CONVECTION SHOULD
SHUT DOWN FAIRLY QUICKLY FROM WEST TO EAST DURING THE AFTERNOON ONCE
THE MAIN COLD FRONT MOVES THROUGH.

SOME LINGERING CONVECTION SHOULD PERSIST OVER ROUGHLY THE EASTERN
THIRD OF THE CWFA DURING THE EARLY EVENING BEFORE ENDING. THE LATE
EVENING AND OVERNIGHT HOURS LOOK TO BE DRY AS CANADIAN HIGH PRESSURE
BUILDS INTO THE MIDWEST.


.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 309 AM CDT MON APR 21 2014

THE LONG TERM FORECAST WILL BEGIN WITH COOL AND DRY WEATHER TUESDAY
THROUGH EARLY WEDNESDAY...FOLLOWED BY A RATHER DYNAMIC COLD FRONTAL
PASSAGE/LOW PASSAGE THURSDAY.

WITH SUN TUESDAY...WE SHOULD CLIMB BACK TO THE UPPER 50S NORTH TO
MID 60S SOUTH...ALL IN ALL NOT A BAD DAY BUT NONE THE LESS COOLER
THAN THE PAST FEW DAYS. TUESDAY NIGHT...SHORT WAVE RIDGING SHOULD
ALLOW FOR A RADIATIONAL COOLING NIGHT OF LOWS IN THE MID 30S
NORTHEAST TO LOWER 40S SOUTHWEST. AN INCREASE IN MID AND HIGH CLOUDS
IS LIKELY TOWARD EARLY WEDNESDAY AS THE NEXT SYSTEM SPREADS MOISTURE
ACROSS THE PLAINS. MODELS NOW BRING THE FRONT ACROSS THE CWA DURING
THE MID MORNING TO EARLY AFTERNOON HOURS WITH STRONG FORCING. IT
SEEMS LIKELY THAT WE WILL NOT HAVE A BREAK BETWEEN ANY WEDNESDAY
NIGHT CONVECTION/DISSIPATING CONVECTION AND ANY NEW DEVELOPMENT
THURSDAY. THUS...IT SEEMS OUR THREAT FOR SEVERE WEATHER IS LOW DUE
TO A LACK OF LOWER LEVEL INSTABILITY. RAINFALL CONTINUES TO LOOK
LIGHT TO MODERATE...GENERALLY A HALF INCH OR LESS GIVEN THE
PROGRESSIVE NATURE OF THE SYSTEM AND LESS THAN IDEAL DIURNAL TIMING.
COVERAGE DOES LOOK HIGH ENOUGH THURSDAY TO CONTINUE WITH LIKELY
POPS.

IN THE WAKE OF THE SYSTEM THURSDAY...WE WILL CONTINUE TO HAVE LOWER
POPS IN FOR THURSDAY EVENING. THE GFS HAS SOME MORE ENERGY ON THE
BACK SIDE OF THE COLD FRONT FOR POTENTIAL SHOWERS...WHILE THE ECMWF
IS DRY. THESE POPS COULD EASILY BE REMOVED ON THE NEXT SHIFT IF THE
GFS LOSES THIS FEATURE.

FRIDAY INTO SATURDAY MORNING APPEARS DRY...AND FROM THERE ON...THE
EXTENDED COMPUTER MODELS VARY INCREDIBLY. WHILE FRONTAL POSITIONS
AND QPF CERTAINLY DRAW ONES ATTENTION TO THE DIFFERENCES BETWEEN THE
00Z GFS AND 00Z ECMWF...THAT IS NOT THE SOURCE OF THE VARIATION. IT
ALL COMES DOWN TO HOW EACH MODEL HANDLES THE ENERGY ON THE SYSTEM
THURSDAY AS IT MOVES TOWARDS THE EAST COAST. ALL MODELS HAVE A
CLOSED LOW MOVING OVER SOUTHEAST CANADA FROM FRIDAY THROUGH THE
WEEKEND. HOWEVER...THE GFS CONTINUES TO PRODUCE A VERY STRONG CUT
OFF LOW FROM THIS PROCESS. AN UPPER LOW SO STRONG IS PLACES THE
CONUS INTO A FULL OMEGA BLOCK...WITH STRONG SUBSIDENCE THROUGH DAY
10 OVER THE UPPER MIDWEST. IT ALSO KEEPS VERY COLD AIR CIRCULATING
AROUND THAT LOW...RESULTING IN DRY...COLD...MOSTLY SUNNY SKIES.  THE
GEM AND ECMWF DO NOT PRODUCE SUCH A DEEP CUT OFF LOW. THUS...WITHOUT
A STRONG CUT OFF...THEY SHOW A MORE PROGRESSIVE SYNOPTIC FLOW...WITH
A DEEP UPPER TROF EMERGING INTO THE PLAINS BY NEXT WEEKEND. FROM
THAT POINT ON...THE ECMWF CREATES VERY WET SCENARIO...WHICH WOULD BE
LIKELY SHOULD ITS HANDLING OF THE EAST COAST WHOPPER UPPER LOW...OR
MORE PROPERLY...LACK THERE OF...BE CORRECT.  FOR NOW...WE HAVE A
COOL FORECAST SATURDAY THROUGH SUNDAY...WITH MODERATE CHANCE POPS
FOR RAIN AND SOME THUNDER SOUTH.
ERVIN

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1242 PM CDT MON APR 21 2014

MORE WIDESPREAD VFR CONDITIONS CONTINUE THROUGH MID AFTERNOON
AHEAD OF AN INCOMING COLD FRONT...ALTHOUGH WITH EMBEDDED SCATTERED
SHOWERS AND A FEW THUNDERSTORMS THAT WILL PRODUCE BRIEF PERIODS OF
MVFR TO POSSIBLY IFR CONDITIONS AS THE STORMS AND HEAVIER SHOWERS
PASS BY THE TERMINALS. ACTIVITY WILL BECOME MORE WIDESPREAD AT MLI
AND CONTINUE TO BE WIDESPREAD AT BRL THROUGH LATE AFTERNOON. WEST
TO SOUTHWEST SFC WINDS UNTIL THE FRONTAL PASSAGE THIS EVENING. A
PERIOD OF A FEW HOURS OF MVFR CIGS ALONG AND JUST BEHIND THE FRONT
EVEN IN AREAS WITHOUT RAIN...THEN NORTHWEST WINDS WILL INCREASE TO
10-15KTS EARLY TO MID EVENING BEHIND PASSING FRONT AND SCOOP CIGS
BACK UP TO VFR. CLEARING THEN TO COMMENCE FROM NORTHWEST-TO-
SOUTHEAST AS THE EVENING PROGRESSES. CLEAR SKIES LATE TONIGHT AND
TUE MORNING WITH ONGOING NORTHWEST TO NORTH WINDS OF 10-15+KTS. ..12..

&&

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

$$

UPDATE...08
SYNOPSIS...08
SHORT TERM...08
LONG TERM...ERVIN
AVIATION...12






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