000
FXUS63 KDVN 161740
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1240 PM CDT THU MAY 16 2013

.UPDATE...
ISSUED AT 1218 PM CDT THU MAY 16 2013

SURFACE ANALYSIS FROM 15Z INDICATED THE PRIMARY STATIONARY FRONT
AT THE SURFACE REACHED FROM JUST SOUTH OF SPRINGFIELD IL THROUGH
KEOKUK...THEN W-NW TO NEAR OMAHA. THE REMNANTS OF THE OVERNIGHT
SHOWERS AND THUNDERSTORMS ACROSS THE SOUTH HAVE SINCE ZIPPERED
WEST AND FINALLY DISSIPATED ALONG THIS BOUNDARY OVER S CENTRAL AND
SW IA OVER THE LAST OUR. HOWEVER...NEW DEVELOPMENT WAS INDICATED
BY KILX 88D ALONG THE SURFACE BOUNDARY NEAR KSPI AND VISIBLE
SATELLITE IMAGERY REVEALED AN AGITATED CU FIELD EXTENDING
NORTHWEST FROM INTO FAR NE MO AND THE IA/MO BORDER REGION.

SHORT TERM HIGH RES MODELS AND LATEST TRENDS SUPPORT REDEVELOPMENT
OF SCATTERED SHOWERS AND THUNDERSTORMS ALONG AND NORTH OF THIS
BOUNDARY ACROSS THE FAR SOUTH THIS AFTERNOON. WEAK MID LEVEL
SUBSIDENCE INDUCED NORTH OF THE UPPER LOW OVER NE OK...ALONG WITH
DRY AIR AT 850 MB...HAS LIKELY HELPED DISSIPATE THE MID LEVEL CLOUDS
OVER THE NORTHERN HALF OF THE FORECAST AREA...AND WILL LIKELY KEEP
RAIN CHANCES LOW THERE THIS AFTERNOON. FORECAST THEN BECOMES MORE
COMPLEX TONIGHT AS AN ADVANCING SHORTWAVE AND THUNDERSTORM COMPLEX
ACROSS NORTH CENTRAL NEB CONTINUES TO ADVANCE EASTWARD...BUT WILL
BE HINDERED SOME ITS INTERACTION WITH THE LOW MOVING INTO THE MID
MS VALLEY. FOR NOW...WILL KEEP LOW CHANCES FOR THUNDERSTORMS GOING
OVER THE ENTIRE FORECAST AREA AS THE SURFACE FRONT WASHES OUT AND ADVANCES
NORTHWARD.

&&

.SYNOPSIS...
ISSUED AT 330 AM CDT THU MAY 16 2013

A STATIONARY FRONT IS DRAPED ALONG THE KANSAS/NEBRASKA
BORDER...ACROSS FAR NORTHERN MISSOURI...AND CONTINUING EAST ACROSS
CENTRAL ILLINOIS AND INDIANA.  THIS FRONT SERVED AS THE FOCUS FOR
SURFACE BASED CONVECTION LAST EVENING.  AT 850MB THE FRONT SURFACE
IS JUST A LITTLE WAYS NORTH OF THE SURFACE BOUNDARY...AND IS BEING
NICELY DEPICTED BY THE CONVECTION OVER SOUTHERN IOWA..AND ALSO
CONTINUING EAST INTO ILLINOIS AND INDIANA.  FROM THE 00Z UPPER AIR
ANALYSIS IT ALSO CONTINUES WEST TO NORTHEAST COLORADO...GENERALLY
NEAR OR JUST NORTH OF THE SURFACE BOUNDARY.  THE 850MB ANALYSIS ALSO
SHOWS PLENTY OF LOW LEVEL MOISTURE BEING ADVECTED NORTH AND
IMPINGING ON THE 850MB BOUNDARY...BUT NOT VERY STRONGLY AND IS ONLY
JUST ENOUGH TO PRODUCE THE SHOWERS AND THUNDERSTORMS WE HAVE ON THE
RADAR NOW.   LE

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT THU MAY 16 2013

THE MAIN CONCERN THE NEXT 24 HOURS IS WHERE AND WHEN THE SHOWERS AND
THUNDERSTORMS WILL FORM.

TODAY...EXPECT THAT THIS CURRENT BAND OF CONVECTION IS GOING TO
GRADUALLY WEAKEN TOWARDS SUNRISE...THOUGH IT MAY FLARE A LITTLE
PERIODICALLY.  THEN...EXPECT SOME ISOLATED TO SCATTERED ACTIVITY
ALONG THE BOUNDARY DURING THE MORNING AND EARLY AFTERNOON AS STORMS
SETTLE DOWN AND THEN REFOCUS UPON THE SURFACE BOUNDARY DURING THE
AFTERNOON.  HOWEVER...BY THEN IT WILL BE SLOWLY PUSHING NORTH IN
RESPONSE TO A SHORTWAVE MOVING ACROSS THE PLAINS...AND NEW
CONVECTION FIRING OUT OVER NEBRASKA AND SOUTH DAKOTA THIS AFTERNOON.
SOME MODELS ARE HINTING THAT WE WILL HAVE LITTLE/NO CONVECTION OVER
THE AREA THIS AFTERNOON...BUT CANNOT RULE OUT SOME ISOLATED TO
SCATTERED ACTIVITY AS LOW LEVEL CAPES SHOULD APPROACH 1000-1500 SOUTH
OF THE FRONT AND WEAK LOW LEVEL CONVERGENCE ALONG IT SHOULD SERVE AS
A FOCUS.  DO NOT EXPECT ANY SEVERE STORMS OUT OF THIS...BUT SLOW
MOVING GARDEN VARIETY SHOWERS AND THUNDERSTORMS. HIGH TEMPERATURES
TODAY SHOULD BE FAIRLY CLOSE TO WHAT WE HAD YESTERDAY...IF SLIGHTLY
COOLER SOUTH WHERE MORE CLOUD COVER IS EXPECTED.

TONIGHT EXPECT THAT THE FRONT WILL CONTINUE TO SLOWLY PULL NORTH AS
THE CONVECTION OUT WEST FORMS INTO AN MCS OVER EASTERN SOUTH DAKOTA
AND NORTHEAST NEBRASKA AS WELL.  HAVE KEPT THE SLIGHT CHANCE POPS
GOING OVER THE CWA AS THE FRONT PULLS NORTH..BUT CONFIDENCE IS NOT
VERY HIGH.  IN FACT...THERE IS SOME RISK THAT THE MCS WILL MOVE EAST
AND BEGIN TO MOVE INTO THE FORECAST AREA BY 12Z...ESPECIALLY IF IT
CAN CAUSE SOME ACTIVITY TO ZIPPER ALONG THE FRONT TOWARDS US.
THUS...THE EVENING POPS ARE FAIRLY LOW...BUT HAVE RAMPED POPS UP TO
CHANCE CATEGORY AFTER MIDNIGHT.   MIN TEMPS IN THE 50S AND LOW 60S
CAN BE EXPECTED. HAVE COOLED OFF THE NORTHEAST AS WE MAY GET SOME
LAKE EFFECTS IN THERE AS THE WINDS TURN MORE NORTHEAST.    LE

.LONG TERM...(FRIDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 330 AM CDT THU MAY 16 2013

FRIDAY AND SATURDAY...WILL CONTINUE TO KEEP CHC POPS FOR SHOWERS AND
THUNDERSTORMS ACRS THE CWA ON FRI WITH HIGHEST CHC AXIS ORIENTED
FROM NW-TO-SE ACRS FCST AREA. THIS IN AREA OF WARM AIR ADVECTION
WING ASSOCIATED WITH PROBABLY MCS MOVING ACRS FAR NORTHERN IA...MN
AND INTO WI. STILL A CHANCE FOR THE SOUTHEAST FLANK OF THE MAIN
SYSTEM ITSELF TO GRAZE THE FAR NORTHERN CWA FRI MORNING. ACTIVITY
SHOULD DIURNALLY WANE FRI AFTERNOON. SOME MODERATE AMOUNTS OF
RAINFALL POSSIBLE IN THE FAR NORTHERN CWA OR UNDER WAA WING AXIS.
LULLS OR BREAKS IN THE PRECIP TO ALLOW TEMPS TO WARM TO AROUND 80
BUT THEY MAY STAY COOLER IN THE 70S ACRS THE FAR NORTH IN
LINGERING CONVECTIVE ZONE AND CLOUD DEBRIS...EAST BOUNDARY LAYER
FLOW AS WELL NORTH OF LINGERING LLVL BOUNDARY. LATEST SUITE OF 00Z
MODEL RUNS AND ENSEMBLES CONTINUE TO TREND IN HANDLING OF L/W
UPPER TROF ESTABLISHING ACRS THE ROCKIES EFFECTIVELY ENHANCING
UPPER RIDGING TO TH EAST OF IT ACRS MUCH OF THE MID AND UPPER MS
RVR VALLEY REGIONS THROUGH SAT. THUS AFTER A CHANCE OF LINGERING
SHOWERS/STORMS EARLY FRI EVENING...THE DVN CWA MAY BE MAINLY DRY
THROUGH 12Z SUNDAY. FCST SOUNDINGS SUGGESTING BUILDING CAPPING
WARM WEDGE ALOFT ON SAT WILL ALSO HAMPER AMBIENT HEATING INDUCED
THUNDERSTORMS. LLVL MOISTURE FEED/WARM CONVEYOR UP TO THE LEE OF
SHEARING L/W TROF SUGGESTS THE SIGNIFICANT CONVECTION TO OCCUR
ACRS MAINLY THE CENTRAL INTO NORTHERN PLAINS DURING THE SECOND
HALF OF THIS PERIOD. WITH LACK OF PRECIP..SAT HIGHS WIDESPREAD IN
THE 80-85 DEGREE RANGE EXCEPT ALONG AND NORTH OF THE HWY 20
CORRIDOR.

SUNDAY AND MONDAY...ASSESSING THE LATEST RUNS...INCREASING NEG
TILTED UPPER TROF AND DEEPENING LLVL CYCLONE SOMEWHERE OVER THE
NORTHEASTERN PLAINS OR WESTERN MN THIS PERIOD STILL SUGGESTS A
POTENTIALLY SIGNIFICANT CONVECTIVE EVENT OR TWO MAY OCCUR IN OR
NEAR THE DVN CWA THIS PERIOD. BEST GUESS AT THIS POINT SUGGESTS MUCH
OF THE DAY SUNDAY TO BE DRY AND HEAT UP INTO THE MID TO UPPER 80S
WITH SFC DPTS MAKING IT INTO THE 60S FOR DECENT CAPE VALUES.
AFTERNOON CONVECTION MAY STILL LOOK TO TAKE OFF ACRS WESTERN INTO
CENTRAL IA...THEN LOOK TO PROPAGATE INTO THE DVN CWA SUNDAY NIGHT.
STRONG TO SVR CONVECTION POSSIBLE AS IT ARRIVES...AS WELL AS
LOCALLY HEAVY RAINFALL POSSIBLE OF OVER AN INCH BY MONDAY MORNING.
MONDAY STILL APPEARS A QUESTION MARK VERY MUCH DEPENDING ON WHAT
OCCURS OR LINGERS OUT OF SUNDAY NIGHT. CONVECTIVE DEBRIS AND OUTFLOW
LASTING LONG ENOUGH TO LIMIT INSTABILITY LOCALLY AND SHIFTING
STORM INITIATION JUST OFF TO THE EAST AND SOUTH...OR THE MORNING
DEBRIS CLEARS OFF IN TIME FOR RAPID DESTABILIZATION. THIS WOULD BE
TROUBLE AS SYNOPTICALLY STRONGEST FORCING OF THE PERIOD AND POSSIBLE
SUPERCELL/TORNADIC SET-UP WOULD LOOK TO TAKE PLACE AHEAD OF INCOMING
DRY SLOT ACRS AT LEAST THE EASTERN OF SOUTHEASTERN HALF OF THE DVN
CWA BY MONDAY AFTERNOON AND EVENING. HIGH CHC POPS OR EVEN SOME
LIKELY/S TO CONTINUE FROM SUNDAY NIGHT THROUGH MON...ALTHOUGH PLENTY
OF QUESTIONS CONTINUE BUT THE SIGNALS HAVE BEEN THERE FOR A FEW DAYS
NOW. DRY SLOT ASSOCIATED WITH A STRONG WRAPPED UP SYSTEM MAY BRING
LULL IN THE ACTIVITY LATE MON NIGHT INTO TUE.

TUESDAY AND WEDNESDAY...CLOSED OFF UPPER LOW BEING HANDLED
DIFFERENTLY BY SEVERAL OF THE MEDIUM RANGE MODELS THIS PERIOD...BUT
LONG RANGE SIGNALS SUGGEST IT TO BE BLOCKED OR GYRATE SLOWLY TOWARD
THE MID/UPPER MS RVR VALLEY THROUGH THE END OF THE LONG RANGE FOR
MORE SHOWERS AS IT BECOMES COOL CORE AND INDUCING UNSTABLE PARCELS.
HOW COOL CORE THE CLOSED LOW BECOMES AND WHERE IS VERY MUCH UP TO
DEBATE BETWEEN THE THE VARIOUS SOLUTIONS.    ..12..

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1218 PM CDT THU MAY 16 2013

VFR AND LIGHT SOUTHEAST CONDITIONS TO PREVAIL THIS AFTERNOON
THROUGH FRIDAY MORNING. A STALLED SURFACE FRONT ACROSS FAR SOUTHERN
IA INTO CENTRAL IL WILL BE THE FOCUS FOR SHOWERS AND THUNDERTORMS
THIS AFTERNOON...WHICH MAY IMPACT THE BRL SITE. OVERNIGHT...THERE
IS A LOW CHANCE OF THUNDERSTORMS AT ESPECIALLY CID AND DBQ AS THIS
BOUNDARY ADVANCES NORTHWARD. THIS IS HANDLED WITH PROB30 GROUPS
FOR LATE TONIGHT AND EARLY FRIDAY MORNING IN THE LATEST FORECAST
FOR CID AND DBQ.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...LE
SHORT TERM...LE
LONG TERM...12
AVIATION...SHEETS