Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 190453
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1153 PM CDT MON AUG 18 2014

.UPDATE...
ISSUED AT 941 PM CDT MON AUG 18 2014

PRONOUNCED WARM EML /CAP/ ON DVN 00Z RAOB HAS SUPPRESSED ANY STORM
DEVELOPMENT SO FAR... BUT APPROACHING MID LEVEL SPEED MAX AND
UPPER DIFFLUENCE SOUTH OF NORTHERN MN SHORTWAVE TO OVERSPREAD THE
CWA LATE THIS EVE AND OVRNGT. THIS FORCING SHOULD BE SUFFICIENT
TO ALLOW FOR SOME ELEVATED SHOWERS AND STORMS TO DEVELOP LATE THIS
EVE AND OVRNGT... WITH INITIAL ACTIVITY LIKELY FOCUSING OVER
NORTHEAST IA THEN CONTINUED PROPAGATION AND POTENTIAL PERCOLATION
TO THE EAST-SOUTHEAST OVRNGT. COVERAGE OF STORMS REMAINS IN
QUESTION WITH EML AND HAVE KEPT POPS IN CHANCE CATEGORY. DRY AIR
ALOFT AND INCREASING SHEAR ALONG WITH 500-800 J/KG OF CAPE IN
-10C TO -30C ALL FAVOR HAIL WITH STRONGEST STORMS... WITH MAINLY
SUB-SEVERE UNLESS SOMEHOW MANAGE A STRONG ROTATING UPDRAFT IN WHICH
CASE LARGE HAIL AND DAMAGING WINDS POSSIBLE BUT THIS APPEARS WOULD
BE ISOLATED.

&&

.SYNOPSIS...
ISSUED AT 331 PM CDT MON AUG 18 2014

A WEAK NORTH-SOUTH BOUNDARY WAS OVER EASTERN IA THIS AFTERNOON...
WITH ITS ENHANCED LOW LEVEL MOISTURE CONVERGENCE BOOSTING
DEWPOINTS INTO THE LOWER 70S OVER EASTERN IA. A CLUSTER OF SURFACE
LOWS WAS OVER WESTERN MN WITH A TROUGH AXIS REACHING SOUTH INTO
WESTERN IA. AREA RADARS SHOWED THUNDERSTORMS OVER WI IN THE
STRONGER FORCING AHEAD OF A STRONG SHORTWAVE MOVING ACROSS MN. A
CLOSER...MORE ISOLATED STORM WAS OVER NE IA. THESE STORMS WERE
NORTHEAST OF A MORE CAPPED ENVIRONMENT THAT WAS RESULTING IN
CLEAR SKIES OVER CENTRAL AND WESTERN IA.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 331 PM CDT MON AUG 18 2014

DEVELOPMENT OF THUNDERSTORMS TONIGHT IS THE PRIMARY CONCERN. THE
COMBINATION OF A VERY WEAK UPPER LEVEL DISTURBANCE MOVING INTO
WESTERN IA AND THE APPROACHING SURFACE TROUGH SHOULD BE ABLE TO
TRIGGER STORMS OVER THE FORECAST AREA THIS EVENING. THIS PROBABILITY
LOOKS GREATEST NORTH OF I-80 WHERE THE CAP WILL BE WEAKEST. THUS
HAVE HIGH CHANCE TO LOW END LIKELY POPS CENTERED ON THE PASSAGE OF
THIS FEATURE...WHICH WILL PASS SOUTHEAST OVERNIGHT AND POSSIBLY
LINGER STORMS OVER THE EAST INTO AT LEAST TUESDAY AFTERNOON. THE
COMBINATION OF MODEST SHEAR AND DEVELOPING INSTABILITY MAY RESULT
IN DAMAGING WIND AND HAIL...AND AT LEAST MARGINALLY SEVERE STORMS
THIS EVENING AND THE SPC HAS A SLIGHT RISK FOR THIS OVER NW HALF
OF THE FORECAST AREA. HIGHER DEWPOINTS WILL HOLD MINS IN THE MID
60S TO AROUND 70. CONTINUED WARM ADVECTION ALOFT SHOULD RESULT IN
CONTINUED DAY TO DAY WARMING AND HAVE HIGHS TUESDAY FROM THE LOWER
80S NORTH TO UPPER 80S IN THE FAR SOUTH.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 331 PM CDT MON AUG 18 2014

QUIET CONDITIONS WILL BE SEEN ACROSS THE AREA TUESDAY EVENING AS THE
BETTER FORCING REMAINS WEST AND SOUTH OF THE AREA. AFTER MIDNIGHT...
FORCING AND MOISTURE INCREASES A LITTLE WHICH SHOULD ALLOW SOME
SHOWERS AND A FEW THUNDERSTORMS TO DEVELOP ACROSS THE FAR SOUTH AND
SOUTHWEST.

THE OVERALL FORCING SLOWLY WEAKENS WEDNESDAY MORNING BUT ISOLATED
SHOWERS AND A FEW THUNDERSTORMS SHOULD CONTINUE ACROSS THE SOUTHWEST
THIRD OF THE AREA DURING THE MORNING WITH ACTIVITY BECOMING MORE
ISOLATED WEDNESDAY AFTERNOON WITH LITTLE IF ANY FORCING ACROSS THE
AREA.

WEDNESDAY NIGHT FORCING AND MOISTURE INCREASES AGAIN WITH CONVECTION
BREAKING OUT ACROSS THE AREA. BY MIDNIGHT AN ORGANIZED THUNDERSTORM
COMPLEX SHOULD BE ALONG THE IA/MN BORDER THAT DROPS SOUTHEAST INTO
THE AREA. BASED ON THE OVERALL FORCING...THE NORTHEAST TWO THIRDS OF
THE AREA IS MORE FAVORED FOR THE MORE WIDESPREAD RAIN.

THE THUNDERSTORM COMPLEX WILL SLOWLY DECAY THURSDAY MORNING AS IT
MOVES TOWARD INDIANA. AGAIN...THE NORTHEAST TWO THIRDS OF THE AREA
IS MORE FAVORED FOR THE BETTER RAINFALL. BOUNDARIES LEFT OVER FROM
THE NOCTURNAL THUNDERSTORM COMPLEX WILL PROVIDE THE FOCUS FOR
ISOLATED TO SCATTERED CONVECTION THURSDAY AFTERNOON.

THURSDAY NIGHT ON...
THE MODEL CONSENSUS INDICATES THE WEATHER PATTERN SHOULD REMAIN
FAIRLY ACTIVE THURSDAY NIGHT THROUGH SUNDAY WITH SLIGHT CHANCE TO
CHANCE POPS IN EACH PERIOD.

THE OVERALL FORCING SUGGESTS THE POTENTIAL FOR ANOTHER NOCTURNAL
THUNDERSTORM COMPLEX THURSDAY NIGHT INTO FRIDAY. THE POSSIBILITY
EXISTS THAT FRIDAY NIGHT INTO SATURDAY MAY BE DRY.

THE MODEL CONSENSUS SUGGESTS ANOTHER COLD FRONT WILL MOVE THROUGH
THE AREA SATURDAY NIGHT INTO SUNDAY.

SUNDAY NIGHT INTO MONDAY THE MODEL CONSENSUS HAS SLIGHT CHANCE POPS
FOR THE AREA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1148 PM CDT MON AUG 18 2014

CHANCE OF STORMS WILL BE FOUND OVERNIGHT INTO EARLY TUESDAY MORNING
AHEAD OF A PASSING WEAK FRONT AND UPPER LEVEL DISTURBANCE.
BEST CHANCE OF STORMS APPEARS TO BE NORTH OF I-80 WITH GREATEST
NORTH OF HWY 30 AND HAVE A TEMPO AT DBQ FOR A SHORT WHILE
OVERNIGHT....WITH PROB30 AT CID. MORE UNCERTAINTY ON EVOLUTION OF
STORMS FURTHER SOUTH AT MLI AND BRL DUE TO CAP AND WEAKER FORCING
AND HAVE OMITTED ANY MENTION FOR NOW WITH 06Z. DECREASING
SOUTHERLY WINDS AND MOISTURE POOLING AHEAD OF FRONT MAY RESULT IN
ANOTHER ROUND OF FOG OVERNIGHT WITH VISIBILITIES MAINLY MVFR TO
LOCAL IFR. CONDITIONS RETURN TO VFR TUESDAY MORNING AND REMAIN SO
THE REST OF TAF CYCLE WITH WINDS TURNING WESTERLY.

&&

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

$$

UPDATE...05
SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...08
AVIATION...05




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