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000
FXUS63 KDVN 170436
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1136 PM CDT THU MAY 16 2013

.SYNOPSIS...
ISSUED AT 325 PM CDT THU MAY 16 2013

SURFACE FRONT EARLY THIS AFTERNOON REMAINED STALLED FROM SOUTHERN OH
AND IN...W-NW ACROSS CENTRAL IL THROUGH THE FAR SE TIP OF IA TO NEAR
OMAHA. TEMPERATURES WERE IN THE 80S OVER MUCH OF THE AREA...WITH THE
FRONT ACTING PRIMARILY AS A MOISTURE BOUNDARY. SURFACE DEWPOINTS
WERE IN THE 60S TO ITS SOUTH...WHILE 40S ENCOMPASSED MOST OF THE
DVN FORECAST AREA TO THE NORTH. AREA RADARS SHOW THIS BOUNDARY LIT
UP WITH SCATTERED THUNDERSTORMS FROM SOUTHERN INDIANA TO NEAR KEOKUK.
IN THE BIGGER PICTURE...A SLOW MOVING UPPER LOW WAS ROLLING INTO
NORTHEAST AR...HELPING MAINTAIN AN AXIS OF GULF MOISTURE AT 850 MB
FROM KS THROUGH MO INTO THE OHIO RIVER VALLEY. TO THE WEST...A
SHORTWAVE AND ACCOMPANYING MCS WAS OVER NORTHEAST NEB. A SECONDARY...
PERHAPS STRONGER STRONGER SHORTWAVE AND THUNDERSTORM COMPLEX WAS
MOVING INTO SW NEB. THESE FEATURES CREATE A CHALLENGING FORECAST
FOR PRECIPITATION CHANCES IN THE IN THE SHORT TERM THROUGH
FRIDAY...THEN ATTENTION TURNS TO A MORE SIGNIFICANT SYSTEM AND
POSSIBLE SEVERE WEATHER OUTBREAK LATE IN THE WEEKEND INTO EARLY
NEXT WEEK.

&&

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 325 PM CDT THU MAY 16 2013

POOR INITIALIZATION AND HANDLING OF CONVECTIVE TRENDS IN BOTH THE SHORT
TERM MODELS AND SYNOPTIC SCALE MODELS...ALONG WITH A COMPLEX
INTERACTION OF LARGE SCALE FEATURES LENDS TO A LOW CONFIDENCE
FORECAST IN THE EVOLUTION OF THUNDERSTORM CHANCES THROUGH FRIDAY.
IN THE SHORT TERM...HIGH RESOLUTION MODELS DEPICT THE FRONT
LIFTING NORTH THIS EVENING IN ADVANCE OF THE NORTHEAST NEB
THUNDERSTORM COMPLEX MOVING INTO NW IA. THE POTENTIAL FOR
SUSTAINED THUNDERSTORMS WILL BE LIMITED BY A WEAK...SUBSIDENT FLOW
ALOFT AND WEAK MID LEVEL RIDGING IN PLACE OVER THE AREA INDUCED BY
THE UPPER LOW PASSING TO THE NORTH THIS EVENING. FOR NOW...WILL
FOLLOW TRENDS FROM 12Z MODELS...THAT WERE LESS BULLISH ON
THUNDERSTORMS ALONG WARM FRONT THIS EVENING...KEEPING SLIGHT
CHANCES GOING THROUGH MID EVENING SOUTH OF I-80. NONE OF THE 12Z
MODELS HAD A DECENT HANDLE ON THE LOCATIONS OF THE MCS COMPLEXES
MOVING THROUGH THE PLAINS AT 18Z. AS EVIDENT BY THE RECENT
OBSERVATION WITH .69 INCHES OF RAIN IN LESS THAN AN HOUR FROM A
SMALL CELL OVER KEOKUK...AND PUBLIC REPORT OF 1.09 IN HANCOCK
COUNTY...WHERE RAIN DOES FALL...LOCALLY MODERATE TO HEAVY RAINFALL
WILL BE POSSIBLE. STORMS LATE THIS AFTERNOON AND EARLY EVENING
WILL WILL BE PULSE TYPE AND SLOW MOVING. LATER TONIGHT...HAVE
POPS RAMPING BACK UP AS THE LEAD SHORTWAVE PASSES TO THE
NORTH...POSSIBLY REINVIGORATING CONVECTION ON THE SURFACE AND 850
MB FRONT OVER THE CENTRAL AND NORTHERN HALF OF THE FORECAST AREA.
OVERNIGHT LOWS WILL RANGE FROM THE LOWER 50S IN THE DRIER AIRMASS
MAINTAINED OVER FAR NW IL...TO THE LOWER 60S ACROSS THE SOUTH.

FRIDAY...THE SECONDARY SHORTWAVE IN WESTERN NEBRASKA ROLLS ACROSS
NORTHERN IA AROUND MIDDAY WHILE THE CENTRAL MS VALLEY LOW PASSES
INTO THE OHIO RIVER VALLEY. THE BULK OF THE FORCING IS AGAIN
DEPICTED NORTH OF THE AREA...BUT ANY LIFT OVER THE FORECAST AREA
WILL HAVE A HIGHER PW AIRMASS TO PRODUCE SCATTERED SHOWERS AND
THUNDERSTORMS...ESPECIALLY DURING PEAK HEATING. SEVERE WEATHER IS
NOT EXPECTED DUE TO A LACK OF SHEAR OR STRONG BOUNDARIES.THE AIRMASS
CURRENTLY ACROSS SOUTHERN IL AND MO WILL BE IN PLACE OVER THE
FORECAST AREA BY AFTERNOON...SUPPORTING HIGHS FROM THE UPPER 70S TO
LOWER 80S WITH HIGHER HUMIDITY AS DEWPOINTS SHOULD BE IN THE UPPER
50S TO LOWER 60S.

.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 325 PM CDT THU MAY 16 2013

...SEVERE WEATHER POSSIBLE SUNDAY AND MONDAY...

FRIDAY NIGHT THROUGH NEXT THURSDAY...
SATURDAY WILL BE A WARM DAY WITH A SHORTWAVE RIDGE ALOFT OVER THE
MIDWEST. MODEL SHOW SURFACE BASED CAPES ARE AROUND 2000 J/KG BUT
TEMPERATURES ALOFT ARE WARM ENOUGH TO KEEP THE AREA CAPPED SO
CONVECTIVE INITIATION IS NOT ANTICIPATED. HIGH TEMPERATURES WILL
RANGE AROUND 80 DEGREES.

SUNDAY...SHORT RANGE MODELS SHOW NEGATIVE TILTED UPPER TROF WITH A
SURFACE LOW OVER THE UPPER MIDWEST THAT WILL LIKELY PRODUCE STRONG
THUNDERSTORMS IN OR NEAR THE FORECAST AREA DURING THE AFTERNOON.
SUNDAY MORNING LOOKS TO BE MUGGY WITH TEMPERATURES RISING INTO THE
MID TO UPPER 80S BY AFTERNOON WITH SURFACE DEWPOINTS CLIMBING INTO
THE LOW TO MID 60S. THESE TEMPERATURES WILL DESTABILIZE THE
ATMOSPHERE AND INCREASE CAPES BETWEEN 2500 TO 3000 J/KG. CURRENT
MODELS INDICATE LATE DAY CONVECTION MAY BEGIN OVER WESTERN IOWA AND
MOVE EAST TOWARD THE MISSISSIPPI VALLEY SUNDAY NIGHT. STRONG OR
SEVERE THUNDERSTORMS WITH HEAVY RAIN ARE LIKELY OVERNIGHT. I WILL
CONTINUE TO CARRY CURRENT FORECAST LIKELY POPS.

MONDAY...LATEST MODELS INDICATE THERE IS AN INCREASING CHANCE FOR
SEVERE THUNDERSTORMS/SUPERCELLS MONDAY AFTERNOON WHEN THE STRONGEST
UPPER LEVEL FORCING OCCURS...ALONG WITH A WELL DESTABILIZED
ATMOSPHERE AND SURFACE FRONT MOVING ACROSS THE AREA. MODEL SOLUTIONS
VARY AS TO WHERE THE LOCATION AND TIMING OF THE BEST SYNOPTIC
FORCING WILL BE...BUT THEY ALL CONTINUE TO MAINTAIN A NEGATIVELY
TILTED TROF OVER THE UPPER MID WEST. THE LOW BECOMES NEARLY
VERTICALLY STACKED AS IT MOVES TOWARD MINNESOTA. WITH A WARM FRONT
HAVING PASSED WELL NORTH OF THE REGION ON SUNDAY..AMPLE MOISTURE
ADVECTION FROM THE GULF OF MEXICO WILL KEEP DEWPOINTS IN THE MID 60S
WITH HIGH TEMPERATURES IN THE MID TO UPPER 70S PRODUCING HIGH CAPE
VALUES. KEEPING LIKELY POPS IN THE CURRENT FORECAST SEEMS REASONABLE.

DUE TO VARYING MODEL SOLUTIONS AND THE LOCATION OF BOUNDARIES LEFT
OVER FROM SUNDAYS CONVECTION...CONFIDENCE IS HIGH SEVERE WEATHER
WILL OCCUR IN OR NEAR THE FORECAST AREA. CONFIDENCE IS LOW AS TO THE
EXACT LOCATION.

TUESDAY THROUGH THURSDAY...CONSENSUS MODEL SOLUTIONS DIVERGE IN
EVOLUTION OF THE CLOSED UPPER LOW BUT THE OVERALL TREND IS FOR THE
SYSTEM TO MEANDER OVER THE MISSISSIPPI VALLEY. WITH WEAK VORT MAXES
ROTATING AROUND THE UPPER LOW AND COOL TEMPERATURES ALOFT THERE WILL
BE A CHANCE OF THUNDERSTORMS TUESDAY AND WEDNESDAY. BY
THURSDAY...THE MODELS MOVE THE UPPER LOW SOUTHEAST AND BUILD A LONG
WAVE RIDGE OVER THE MIDWEST. TEMPERATURES WILL BE AROUND 80 ON
WEDNESDAY BUT WILL BEGIN TO RISE AS AS HEIGHTS CONTINUE TO BUILD

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1134 PM CDT THU MAY 16 2013

A CHALLENGING NEXT 24 HOURS OF AVIATION IS EXPECTED AS WE SEE A
WEAK WARM FRONT GRADUALLY LIFT FROM SOUTHEAST IOWA INTO WISCONSIN FROM
EARLY THIS MORNING THROUGH THIS AFTERNOON. AS THIS
OCCURS...CONDITIONS WILL REMAIN MAINLY VFR ON A WIDESPREAD
NATURE...HOWEVER...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
WILL CONTINUE TO BE A THREAT ALONG THE FRONT. THIS WILL BE MAINLY
THIS EVENING AROUND BRL...AND FROM LATE TONIGHT THROUGH THE
AFTERNOON HOURS FRIDAY AT MLI...CID...AND DBQ. THE COVERAGE OF
STORMS IS NOT WIDESPREAD ENOUGH TO WARRANT MORE THAN A VICINITY
MENTION WITHIN TAF FORECASTS.CONVECTIVE TRENDS WILL BE WATCHED
CAREFULLY...AND UPDATES TO TAFS WILL BE ISSUED AS NEEDED. ERVIN

&&

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

$$

SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...KUHL
AVIATION...ERVIN