000
FXUS63 KDVN 181802
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
102 PM CDT TUE JUN 18 2013

.UPDATE...
ISSUED AT 639 AM CDT TUE JUN 18 2013

CLUSTER OF SHOWERS AND THUNDERSTORMS ASSOCIATED WITH THE UPPER
LEVEL SHORTWAVE OVER SOUTHERN MN WAS ABOUT TO CROSS OVER FROM MN
INTO N CENTRAL IA AT 6 AM. A MORE RECENT DEVELOPMENT IS AN AREA OF
SHOWERS AND A FEW THUNDERSTORMS OVER CENTRAL AND SW IA THAT APPEAR
TO BE OCCURRING AHEAD OF A SEPARATE MID LEVEL SHORTWAVE MOVING OUT
OF NEB AND SD. THIS IS ON A PATH TO MOVE ACROSS THE SOUTHERN HALF
OF THE FORECAST AREA THIS MORNING AND WILL UPDATE SHORTLY TO RAISE
POPS ACCORDINGLY.

&&

.SYNOPSIS...
ISSUED AT 330 AM CDT TUE JUN 18 2013

SURFACE ANALYSIS INDICATED A BACKDOOR COLD FRONT MAKING ITS WAY
SOUTHWEST ACROSS THE FORECAST AREA EARLY THIS MORNING FROM KMLI TO
KIOW AT 07Z. THIS WAS IN THE PROCESS OF MERGING WITH THE WEST TO
EAST LOW LEVEL MOISTURE BOUNDARY THAT HAS BEEN IN PLACE SINCE
YESTERDAY MORNING ACROSS SOUTHERN IA AND NORTHERN IL. AT THE
INFLECTION POINT...THERE WAS A WEAK AREA OF LOW PRESSURE PRESSURE
NEAR GALESBURG. NORTHEAST WINDS WERE PULLING IN A SLIGHTLY COOLER
AND DRIER AIRMASS INTO THE NORTHERN HALF OF THE FORECAST AREA.
ALOFT...A STRONG SHORTWAVE WAS EVIDENT ON SATELLITE WV IMAGERY OVER
S CENTRAL MN EMBEDDED IN THE NW FLOW ALOFT. STRONG FORCING AND LOW LEVEL
CONVERGENCE ENHANCED BY THE SURFACE BOUNDARY THAT RAN FROM THE
QUAD CITIES NW INTO SW MN...WAS RESULTING IN AN AREA OF
THUNDERSTORMS AND EVEN AN EMBEDDED SUPERCELL EARLY THIS MORNING
ACROSS SOUTH CENTRAL MN...SEEN ON AREA RADARS DIVING S-SE TOWARD
NORTHERN IA.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT TUE JUN 18 2013

INITIAL CHALLENGE IS CONVECTIVE TRENDS IN THE SHORT TERM AS THE MN
SHORTWAVE AND VORT MAX REACH INTO EASTERN IA THIS MORNING...THEN THE
TIMING AND COVERAGE OF SHOWERS AND THUNDERSTORMS AS THE UPPER SYSTEM
MOVES QUICKLY THROUGH THE AREA TODAY. FOCUS THEN TURNS TO QUIET AND
COOL CONDITIONS OVER THE REGION TONIGHT.

THE COMPACT VORT MAX OVER SW MN IS TAKING AIM ON NORTH CENTRAL IA
AROUND SUNRISE...THEN EAST CENTRAL IA AND NW IL FROM MID TO LATE
MORNING. WHILE THE MID LEVEL LIFT DIVES SOUTHEAST...SURFACE THROUGH
850 MB CONVERGENCE FIELDS...ENHANCED BY THE NW TO SE BOUNDARY DRAPED
ACROSS THE AREA...SUGGESTS A MORE SOUTHWARD MOVEMENT OF THE
CONVECTION IN THE NEAR TERM. THE BOUNDARY IS SHOWN BECOMING MORE
DIFFUSE AND CONTINUING TO DRIFT S-SW AS STRONG SURFACE HIGH PRESSURE
BUILDS INTO THE UPPER GREAT LAKES. WILL ANTICIPATE THE CURRENT
CLUSTER OF THUNDERSTORMS TO REACH INTO THE FAR NW BEFORE 8 AM...THEN
OVERSPREAD MUCH OF EASTERN IA AND FAR NW IL LATE THIS MORNING AND
EXIT TO THE SOUTHEAST WITH THE EXITING WAVE AROUND MID AFTERNOON.
HAVE HIGH CHANCE POPS IN PLACE TO COVER THIS. SOME OF THE STORMS
AT THE ONSET COULD POTENTIALLY HAVE SMALL HAIL AND GUSTY WINDS
OVER EASTERN IA. HOWEVER...ANY POTENTIAL FOR STRONG TO SEVERE
STORMS SHOULD THEN DIMINISH AS LOW LEVEL CONVERGENCE FIELDS WEAKEN
AND MID LEVEL LAPSE RATES AND THETAE LAPSE RATES BECOME MORE
STABLE BY MIDDAY. THE GREAT LAKES AIRMASS OVERSPREADING THE AREA
THIS AFTERNOON SHOULD LIMIT HIGHS TO THE 70S TO NEAR 80.

TONIGHT...SHORTWAVE RIDGING AND HIGH PRESSURE BUILDING OVER LOWER MI
WILL RESULT IN MOSTLY CLEAR AND RELATIVELY COOL CONDITIONS. THIS
AIRMASS HAS TEMPERATURES AND DEWPOINTS IN THE 30S AND 40S NORTHERN
PORTIONS OF MN...WI AND UPPER MI EARLY THIS MORNING. EVEN WITH
CERTAIN MODIFICATION...WIDESPREAD MINS IN THE LOWER 50S AND A FEW
UPPER 40S LOOK REALISTIC ACROSS AT LEAST THE NORTHERN HALF OF THE
FORECAST AREA. HAVE KEPT THE SOUTH IN THE UPPER 50S TO AROUND 60.
THIS WOULD BE NEARLY 10 DEGREES BELOW MID JUNE NORMALS.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 330 AM CDT TUE JUN 18 2013

DRY CONDITIONS WILL BE SEEN ACROSS THE AREA ON WEDNESDAY AS HIGH
PRESSURE MOVES EAST OF THE AREA AND SOUTHERLY RETURN FLOW DEVELOPS.

WED NIGHT THE MCS AND LIFT TOOLS INDICATE A RESPECTABLE MCS WILL
DEVELOP IN WESTERN MISSOURI/EASTERN KANSAS. THE RESPECTIVE TOOLS ARE
MIXED AS TO HOW FAR EAST IT WILL GET BY SUNRISE. THE POSSIBILITY
DOES EXIST THAT THE EXTREME WESTERN/SOUTHWEST PARTS OF THE CWFA MAY
SEE SOME SHOWERS AND POSSIBLY A THUNDERSTORM AROUND DAWN.

THE MCS THAT DEVELOPS WED NIGHT WILL SLOWLY DECAY AS IT MOVES ACROSS
THE CWFA ON THURSDAY. CURRENTLY...THE BETTER RAIN CHANCES ARE OVER
THE WESTERN HALF OF THE CWFA DURING THE MORNING. OUTFLOW BOUNDARIES
LEFT OVER FROM THIS CONVECTION WILL THEN PROVIDE THE FOCUS FOR
DIURNAL CONVECTION ACROSS THE CWFA DURING THE AFTERNOON/EVENING
HOURS.

THURS NIGHT THE QUESTION BECOMES WHERE WILL THE NEXT MCS FORM AND
GO. THE MCS TOOL INDICATES SOME RESPECTABLE WAA WILL OCCUR THAT
SHOULD BE ENOUGH TO GENERATE SOME SHOWERS. ANY WEAK VORT MAX TOPPING
THE RIDGE WOULD SUPPLY JUST ENOUGH LIFT TO DEVELOP THUNDERSTORMS
WITH THE WEAK LLJ.

FRIDAY ON...
THE BIG PICTURE FROM THE MODELS SHOWS THE MCS PATTERN REDEVELOPING
ACROSS THE MIDWEST AND THE CWFA IS EITHER CLOSE TO OR IN THE ACTIVE
MCS TRACK. HOWEVER...THERE IS DISAGREEMENT AMONG THE MODELS
REGARDING PLACEMENT AND MOVEMENT OF INDIVIDUAL FEATURES IN TIME AND
SPACE.

FOR THE FRIDAY THROUGH MONDAY TIME PERIOD THE MODEL CONSENSUS GIVES
SCHC/CHC POP EACH DAY. WHERE CONVECTION DEVELOPS AT NIGHT WILL
AFFECT WHERE IT DEVELOPS THE FOLLOWING DAY. THERE WILL BE DRY
PERIODS DURING THIS TIME FRAME. HOWEVER...THESE DRY PERIODS WILL NOT
BE REASONABLY KNOWN MORE THAN 6 TO 12 HOURS AHEAD OF TIME.    ..08..

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1258 PM CDT TUE JUN 18 2013

VFR CONDITIONS TO CONTINUE THROUGH AT LEAST 20/00Z. WEAK HIGH
PRESSURE OVER THE GREAT LAKES ARE BRINGING SEASONABLY COOL
TEMPERATURES AND FAIR SKIES. LIGHT NE WINDS THIS PM WILL SHIFT TO
THE SE WEDNESDAY. AREA VISIBILITIES WILL STAY WELL ABOVE 7 MILES.

NICHOLS

&&

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

&&

$$

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