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000
FXUS63 KDVN 142243
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
543 PM CDT TUE MAY 14 2013

.UPDATE...
ISSUED AT 539 PM CDT TUE MAY 14 2013

ISOLATED SHOWERS AND STORMS HAVE FORMED OVER NORTHEAST IOWA
THROUGH CENTRAL IOWA ALONG THE FRONT. THIS CONVECTION IS SUPER
HIGH BASED...AND MUCH MORE LIKE FRONT RANGE STORMS OUT WEST.
THUS...A VERY DEEP INVERTED V SOUNDING ENVIRONMENT IS ALLOWING THE
RELATIVELY PUNY CONVECTION TO PRODUCE ISOLATED SEVERE WIND GUSTS
OVER NORTHERN IOWA AT THIS TIME. I HAVE ISSUED AN SPS FOR
THIS...AS IT MAY CONTINUE TO PRODUCE THIS CHALLENGING
WIND THREAT AS IS ENTERS THE CWA IN THE NEXT TWO HOURS. POPS HAVE
BEEN PLACED TO ACCOUNT FOR THE BAND OF CONVECTION...BUT HELD TO 20
PERCENT COVERAGE.

ERVIN

&&

.SYNOPSIS...
ISSUED AT 224 PM CDT TUE MAY 14 2013

UPPER RIDGING WITH LOTS OF VERY WARM AND DRY AIR ALOFT IS MOVING
OVER THE MIDWEST WITH TEMPERATURES AT 2 PM IN THE MID/UPPER 80S
OVER AREA WITH AROUND 90F IN THE FAR WEST ON SW-W WINDS OF 5 TO 15
KTS. SURFACE AND UPPER AIR ANALYSIS SHOW THIS LOBE OF VERY WARM
AIR TO MOVE SOUTH OF AREA NEXT 12-24 HOURS WITH SURFACE FRONT TO
PASS OVER AREA TONIGHT WITH A RETURN TO MORE SEASONABLE
TEMPERATURES. UPSTREAM ENERGY IN PACIFIC SHOWS REGION TO RETURN TO A
BATTLE-ZONE OF AIRMASSES WITH MORE UNSETTLED WEATHER OF STORMS
MORE TYPICAL OF LATE SPRING.

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 224 PM CDT TUE MAY 14 2013

TONIGHT...WEAK COOL FRONT TO SLIDE ACROSS REGION BETWEEN MIDNIGHT
AND 7 AM. MAIN ISSUE IS ISOLATED STORMS THAT MAY FIRE ALONG FRONT
LATER TONIGHT. LOTS OF DRY AIR ALOFT AND HIGH LCL/S SUGGEST RISK
OF GUSTY WINDS AND POSSIBLY "HEAT BURSTS" NW OF THE AREA. IF
OCCURS...THE ENVIRONMENT OVER MISSOURI RIVER VALLEY TO NEAR OUR
AREA IS FAVORABLE. JAMESTOWN ND HAD 51 KTS EARLY THIS AM WITH A
STORM. MINS TONIGHT TO FALL INTO THE UPPER 50S FAR NORTH TO THE
MIDDLE 60S OVER SOUTHERN 1/2 OF THE AREA. HAVE 20 POPS TO COVER
RISK OF ELEVATED SHRA AND TSRA AND IS THE MAIN CHALLENGE FOR LATER
SHIFTS.

WEDNESDAY...NORTHERN HALF OF AREA TO RETURN TO NEAR TO SLIGHTLY
ABOVE NORMAL TEMPERATURES IN THE UPPER 70S WITH MODEST HUMIDITY AND
MOSTLY SUNNY SKIES. SOUTHERN HALF...ESPECIALLY SOUTH OF HIGHWAY
34 CORRIDOR TO HAVE HIGHS IN THE LOWER 80S WITH LOWER 60 DEWPOINTS
AND 20 TO 40 PERCENT POPS OF SHRA AND TSRA. AN ISOLATED STRONG
STORM MAY FORM ON TOP OF INVERSION AROUND 10 K AGL THAT COULD
PRODUCE HAIL AND GUSTY WINDS TO NEAR SEVERE FOR LATER SHIFTS TO
REASSESS. THIS IS SUGGESTED VIA INTERNAL GRAVITY WAVES THAT MAY
OCCUR LATE TONIGHT AND WEDNESDAY...RELATED TO ANY STORMS AND EVEN
HEAT BURST POTENTIAL. A VERY NON-HYDROSTATIC ENVIRONMENT THAT
COULD SUPPORT THIS TO OCCUR.

NICHOLS



.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 224 PM CDT TUE MAY 14 2013

THE SIGNAL FROM ALL THE MODELS IS A MUCH MORE ACTIVE WX PATTERN WILL
BE DEVELOPING OVER THE NEXT 7-10 DAYS. THE ATMOSPHERE IS TAKING ON A
MORE LATE SPRING ASPECT TO IT. AS SUCH...NON LINEAR PROCESSES ARE
TAKING A MORE ACTIVE ROLE IN DETERMINING SENSIBLE WX.

WEDNESDAY NIGHT THE FRONTAL BOUNDARY WILL BE ACROSS THE FAR SOUTHERN
PART OF THE CWFA. A RESPECTABLE THETA E GRADIENT IS IN PLACE SO
CONVECTION THAT DEVELOPS WED AFTERNOON WILL LINGER INTO THE EVENING.
WEAK FLOW THAT DEVELOPS WED NIGHT MAY BE ENOUGH TO ALLOW NEW
CONVECTION TO DEVELOP ACROSS THE SOUTHERN HALF OF THE CWFA THROUGH
SUNRISE THURSDAY.

THE FRONTAL BOUNDARY WILL REMAIN ACROSS THE FAR SOUTHERN PARTS OF
THE CWFA ON THURSDAY. DIFFERENTIAL HEATING WILL ALLOW CONVECTION TO
PERSIST THROUGH THE DAY ACROSS THE SOUTHERN HALF OF THE CWFA AND
POTENTIALLY BECOME MORE NUMEROUS DURING THE AFTERNOON.

THURS NIGHT/FRIDAY...INTERNALLY THE MODELS ARE INDICATING A
RESPECTABLE MCS SHOULD DEVELOP IN NORTHWEST IOWA/SOUTHWEST MN. NEW
CONVECTION SHOULD RIPPLE DOWN AN ELEVATED MOISTURE/THERMAL BOUNDARY
INTO THE NORTHERN PART OF THE CWFA AFTER MIDNIGHT. THETA E LAPSE
RATES TURN NEGATIVE WITH A MARGINAL INCREASE IN WINDS/MOISTURE SO
ISOLATED/SCATTERED CONVECTION SHOULD BE SEEN ACROSS THE ENTIRE CWFA
THURSDAY NIGHT.

FRIDAY...RETURN FLOW STRENGTHENS A BIT MORE. THERE SHOULD BE SOME
NOCTURNAL CONVECTION ACROSS THE CWFA DURING THE MORNING. DIURNAL
HEATING WILL ALLOW NEW CONVECTION TO DEVELOP DURING THE DAYTIME.

FRIDAY NIGHT ON...
THE MODEL CONSENSUS HAS A VERY ACTIVE WX PATTERN ACROSS THE MIDWEST
THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. THE MODELS ARE ALSO
STARTING TO SIGNAL A STRONGER POTENTIAL FOR ORGANIZED CONVECTION AND
WITH ORGANIZED CONVECTION...THE POTENTIAL FOR STRONG TO SEVERE
STORMS WILL BE ON THE INCREASE.

FRIDAY NIGHT THROUGH SATURDAY NIGHT THE MODEL CONSENSUS HAS SCHC/CHC
POPS ACROSS THE AREA. A NEGATIVELY TILTED SYSTEM WILL BE COMING OUT
OF THE ROCKIES AND DEEPER MOISTURE WILL BE STREAMING NORTH FROM THE
GULF.

SUNDAY/SUN NIGHT THE MODEL CONSENSUS HAS CHC/LIKELY POPS. THIS TIME
FRAME WILL BE INTERESTING. THE SYSTEM WILL BE FURTHER EAST AND THERE
ARE INDICATIONS OF STRONG TO POSSIBLE SEVERE CONVECTION DEVELOPING
DURING THE DAY IN WESTERN IOWA THAT MOVES EAST DURING THE AFTERNOON
AND EVENING.

MONDAY INTO TUESDAY...THE MODEL CONSENSUS HAS SCHC/CHC POPS. THERE
ARE DIFFERENCES IN THE MODEL SOLUTIONS ON WHERE THE CUT OFF LOW WILL
DEVELOP. HOWEVER...ALL AGREE THAT ACTIVE WEATHER WILL CONTINUE
ACROSS THE AREA. ORGANIZED CONVECTION WILL BE POSSIBLE ON MONDAY
AHEAD OF AN APPROACHING COLD FRONT.

08

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1230 PM CDT TUE MAY 14 2013

CONDITIONS TO REMAIN VFR THROUGH THE PERIOD. FAIR SKIES AND WARM TO
VERY WARM TODAY AHEAD A WEAK COOL FRONT THAT WILL PASS OVERNIGHT.
SOUTHWEST WINDS OF 5 TO 15 KTS WILL SHIFT TO THE NORTHWEST BETWEEN
15/08-13Z WEDNESDAY. A FEW ISOLATED THUNDERSTORMS MAY FIRE ALONG
THE FRONT OVERNIGHT AT ALL TERMINALS. THESE MAY LAST INTO WEDNESDAY
THAT WOULD ONLY POSSIBLY IMPACT BRL TERMINAL AFTER 15Z. THE CHANCES
ARE TOO SMALL TO INCLUDE IN THE TAF FORECASTS AT THIS TIME.

NICHOLS


&&

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

$$

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