Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 121719
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1219 PM CDT SAT APR 12 2014

.UPDATE...
ISSUED AT 1107 AM CDT SAT APR 12 2014

TWO SEVERE STORMS HAVE MOVE OUT OF THE AREA AS THEY MOVE TOWARD
CHICAGO THIS MORNING. WE HAD WIND DAMAGE AND LARGE HAIL WITH THE
SECOND...WHICH BECAME A ELEVATED SUPERCELL OVER STEPHENSON COUNTY
AROUND 9 TO 10 AM TODAY. OUR EARLY MORNING 12Z SOUNDING INDICATES
DEEP LAYER SHEAR IS MORE THAN SUFFICIENT FOR SUPERCELLS
TODAY...BUT OTHER INDICATIONS ALSO SHOW THAT WE A EML/CAPPING DO DEAL WITH
AS WELL. MODELS ARE NOW HOLDING THE FRONT NORTH OF OUR CWA THROUGH
00Z TODAY...WITH THE EML KEEPING ANY STRONG UPDRAFTS NORTH OF THE
FRONT THROUGH THIS EVENING. I HAVE REMOVED ANY MEASURABLE POPS
FROM OUR CWA THROUGH MID AFTERNOON...WHERE THEY REMAIN ONLY IN THE
NORTHWEST. TONIGHT...OUR NORTHWEST STILL LOOKS MOST LIKELY TO SEE
STORMS/HAIL/HEAVY RAIN...BUT THE SOUTHEAST MAY REMAIN DRY. THAT
SAID...WITH STORMS WIDESPREAD TONIGHT ALONG AND NORTH OF THE
FRONT...A COLD POOL COULD EASILY PUSH THE MCS FARTHER SOUTH INTO
THE CENTRAL AND SOUTH CWA. ALL SAID...A TOUGH FORECAST AFTER 00Z
THIS EVENING. ERVIN

&&

.SYNOPSIS...
ISSUED AT 242 AM CDT SAT APR 12 2014

06Z SURFACE ANALYSIS REVEALED TWO MAIN BOUNDARIES IN OR CLOSE TO
THE CWA EARLY THIS MORNING. A STATIONARY FRONT RAN FROM A SURFACE
LOW OVER SOUTH DAKOTA TO JUST NORTH OF HIGHWAY 30. BEHIND THIS
FRONT...TEMPERATURES HAVE BEEN STEADY OR SLOWLY RISING THROUGHOUT
THE NIGHT MAINLY IN THE 50S. AHEAD OF THE FRONT TEMPERATURES HAVE
DROPPED INTO THE 40S. A WARM FRONT WAS LIFTING NORTH ACROSS
MISSOURI WITH THE MAIN SURGE OF MOISTURE EVIDENT BEHIND THE FRONT
WITH DEWPOINTS SOUTH OF IT ALREADY IN THE LOW TO MID 50S. LATEST
RADAR IMAGERY DEPICTED SHOWERS AND A FEW ISOLATED THUNDERSTORMS
MOVING ACROSS NW IOWA ATTIM JUST AHEAD OF SURFACE LOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 333 AM CDT SAT APR 12 2014

ACTIVE DAY IN STORE FOR THE AREA WITH SEVERE WEATHER POSSIBLE
MAINLY DURING THE LATE AFTERNOON AND EARLY EVENING.

CURRENT SHOWERS/ISOLATED T-STORMS OVER NW IOWA WILL TRACK EAST
STAYING MAINLY TO OUR NORTH THIS MORNING AND AHEAD OF STATIONARY
FRONT. NONETHELESS...MAY STILL SEE A SHOWER OR ISOLATED
THUNDERSTORM ALONG AND NORTH OF HIGHWAY 20 THIS MORNING AND HAVE
MAINTAINED CHANCE POPS FOR THIS. MODELS STILL HAVING TROUBLE WITH LOW
LEVEL MOISTURE FIELDS TOO MOIST COMPARED TO REALITY. THE GFS IN
PARTICULAR IS WAY TOO MOIST AT THE SURFACE WITH DEWPOINTS IN THE
60S OVER MOST OF THE AREA AS EARLY AS NOON. DISCOUNTED THIS AND
FEEL THAT DEWPOINTS IN THE MID TO UPPER 50S ARE MORE REASONABLE.

PRIMARY SURFACE LOW WILL TRACK EAST INTO SOUTHERN MINNESOTA DURING
THE DAY PUTTING THE ENTIRE CWA IN THE WARM SECTOR. THIS ALONG WITH
FORECAST SOUNDINGS SHOWING DEEP MIXING AROUND 800MB WILL HELP BOOST
TEMPERATURES WELL INTO THE 70S BY THE AFTERNOON WITH LOCATIONS
SOUTH OF I-80 LIKELY NEAR OR SLIGHTLY ABOVE 80 DEGREES. THESE WARM
AND UNSTABLE CONDITIONS WILL PRIME THE ATMOSPHERE AHEAD OF COLD
FRONT WITH SB CAPE VALUES INCREASING TO 1500 TO 2000 J/KG BY EARLY
AFTERNOON MAINLY ACROSS THE NORTH AND WEST SECTIONS OF THE CWA.
0-6KM SHEAR VALUES IN EXCESS OF 40 KTS WILL BE SUFFICIENT ENOUGH
FOR THE DEVELOPMENT OF SUPERCELLS AS WEAK CAP BREAKS BY LATE
AFTERNOON. HI-RES MODELS SUGGEST CONVECTIVE INITIATION TO OCCUR IN
20-23Z TIME FRAME ACROSS CENTRAL IOWA WITH CELLS PROPAGATING EAST.
THE PRIMARY RISK WILL BE LARGE HAIL WITH ANY STRONG STORM THAT DEVELOPS.
KEPT HIGHEST POPS FOR T-STORMS OVER THE NORTH AND WEST SECTIONS OF
THE CWA CLOSER TO THE ADVANCING COLD FRONT AND BETTER INSTABILITY.

TONIGHT...MAIN SURFACE BOUNDARY TO STALL IN OR CLOSE TO THE CWA
WITH INCREASING CONVERGENCE AND FORCING PROGS ALONG THE BOUNDARY
SUGGESTING SHOWERS AND T-STORMS ONGOING OVER MUCH OF THE CWA. ANOTHER
MID LEVEL SHORTWAVE IS EXPECTED TO RIPPLE UP ALONG THE BOUNDARY
WITH IMPRESSIVE THETA-E ADVECTION AND CONVERGENCE THAT WILL HELP
KEEP PCPN ONGOING. MODEL PWATS INCREASING TO 200% OF NORMAL WITH
AMOUNTS 1-1.3 INCHES SUPPORTS RAIN AMOUNTS AROUND A HALF INCH
LIKELY BY 12Z SUNDAY ESPECIALLY ACROSS THE NORTHWEST SECTIONS OF
THE CWA.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 333 AM CDT SAT APR 12 2014

HEAVY RAIN OF AROUND 1-2 INCHES STILL LOOKS ON TRACK FOR MUCH OF THE
CWA SUNDAY AND SUNDAY NGT... AS AN UPPER LEVEL SHORTWAVE EJECTS
NORTHEAST FROM THE DESERT SOUTHWEST AND ENCOUNTERS DEEP MOISTURE
POOLING ALONG STALLED FRONTAL ZONE WITH PRECIPITABLE WATER VALUES OF
NEARLY 2 STANDARD DEVIATIONS ABOVE NORMAL. STRONG JET DYNAMICS ALSO
COME INTO PLAY WITH MODELS SHOWING COUPLING OF JETS BETWEEN
RIGHT ENTRANCE REGION OF UPPER MIDWEST SEGMENT AND LEFT EXIT REGION
OF SOUTHERN PLAINS SEGMENT WHICH INDUCES DEEPENING SFC WAVE TRANSLATING
ALONG FRONTAL ZONE ENHANCING LOW LEVEL CONVERGENCE. SFC FRONTAL ZONE
NEARLY PARALLEL TO MID LEVEL FLOW OWING TO THE POTENTIAL FOR TRAINING
CONVECTION AND LOCALLY HIGHER AMOUNTS... WHICH COULD YIELD A LOCALIZED
FLOODING THREAT. OTHERWISE... OUTSIDE OF ANY PERSISTENT TRAINING AND
HIGHER RAINFALL AMOUNTS OF 3+ INCHES... MOST AREAS WITH DRY WARM GROUND
SHOULD BE ABLE TO ABSORB THE HEAVY RAINS... BUT WILL SEE RISES ON
RIVERS/STREAMS/CREEKS THROUGH EARLY NEXT WEEK. CONVECTION SHOULD
GRADUALLY DIMINISH TO STRATIFORM RAIN BY SUNDAY EVENING WITH POST-FRONTAL
DEFORMATION BAND AND DEEPLY SATURATED ATMOSPHERIC COLUMN. STILL APPEARS
OVERNIGHT SUNDAY NGT WILL SEE RAIN MIX WITH OR CHANGE TO SNOW FOR A TIME
MAINLY NORTH/WEST OF QUAD CITIES WITH COLD AIR WRAPPING IN ON STRENGTHENING
NORTHERLY WINDS.

MON-MON NGT...LIKELY TO SEE WINTRY MIX OR RAIN CHANGE TO SNOW BUILDING INTO
AREAS FROM QUAD CITIES EAST/SOUTH UNTIL MID MORNING MONDAY BEFORE
PCPN TAPERS OFF. WARM...WET GROUND AND TEMPS ABOVE FREEZING SHOULD KEEP
ANY SNOW ACCUMS MINOR (LESS THAN 1 INCH) AND MAINLY ON GRASSY OR ELEVATED
SURFACES MAINLY NORTH/WEST OF QUAD CITIES. AFTER PCPN EXITS BY MID MORNING
MAY SEE SMALL CHANCE OF SHOWERS (POSSIBLY MIXED WITH SNOW) EXIST INTO
MONDAY PM WITH MODELS TRENDING SLOWER WITH UPPER TROUGH PASSAGE... BUT MAIN
STORY WILL BE WINDY AND RAW CONDITIONS WITH HIGHS WELL BELOW NORMAL AND
ONLY IN THE LOWER TO MIDDLE 40S WHILE WINDS MAKE IT FEEL MORE LIKE
LOWER TO MIDDLE 30S. DECREASING CLOUDS LATE MONDAY CONTINUING INTO MONDAY NGT
WITH HIGH PRESSURE BUILDING IN. WINDS LOOK TO DIMINISH WHICH WILL SET THE
STAGE FOR A COLD NGT WITH LOWS MAINLY IN THE 20S.

TUE-TUE NGT... GENERALLY QUIET AS HIGH PRESSURE BUILDS OVERHEAD THEN SHIFTS
EAST TUE NGT. LIMITED MIXING TO KEEP COOL HIGHS IN THE 40S ON TUESDAY.
WITH INCREASING SOUTHERLY WINDS TUE NGT MAY SEE LOWS IN THE EVENING WITH
TEMPS THEN STEADY TO RISING OVRNGT.

WED-FRI... LARGE RUN TO RUN VARIANCES IN MEDIUM RANGE MODELS LENDS TO
LOWER CONFIDENCE FCST... BUT GENERALLY IT APPEARS AS THOUGH SOME RAIN CHCS
WILL RETURN TO THE REGION ESPECIALLY TOWARD THE LATTER HALF OF THE
PERIOD WITH CONTINUED MOISTURE ADVECTION AND ENERGY ADVANCING EASTWARD FROM
THE ROCKIES THROUGH THE MIDWEST. TEMPS SHOULD MODERATE DURING THE PERIOD
WITH READINGS CLOSER TO NORMAL BY LATE WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1216 PM CDT SAT APR 12 2014

WHILE CONDITIONS WILL BEGIN WITH WIDESPREAD VFR TODAY...THEY WILL
END WITH WIDESPREAD SHOWERS AND THUNDERSTORMS WITH IFR CONDITIONS.
A LARGE COMPLEX OF STORMS WILL DEVELOP IN CENTRAL IOWA AND MOVE
EAST TO NORTHEAST...AFFECTING CID AND DBQ BY MID EVENING...AND
POSSIBLY MLI AND BRL LATE EVENING. OVERNIGHT...SCATTERED SHOWERS
AND STORMS ARE POSSIBLE WITH MVFR/IFR CIGS AND VISIBILITIES IN ALL
LOCATIONS. SUNDAY SHOWS NO IMPROVEMENT AS A LOW PRESSURE MOVES INTO
ILLINOIS. THIS WILL SWITCH WINDS FROM SOUTH TO NORTHEAST...AND
BRING STEADY IFR CIGS TO MOST OF THE AREA WITH WIDESPREAD
MODERATE RAIN. THUNDER WILL ALSO BE POSSIBLE THROUGHOUT THE DAY
SUNDAY BUT IS EXPECTED TO BE LESS INTENSE DUE TO THE WIDESPREAD
NATURE OF THE RAINS.
ERVIN

&&

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

$$

UPDATE...ERVIN
SYNOPSIS...GROSS
SHORT TERM...GROSS
LONG TERM...05
AVIATION...ERVIN






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