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000
FXUS63 KTOP 171137
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
637 AM CDT FRI MAY 17 2013

...UPDATE TO AVIATION...

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT FRI MAY 17 2013

UPPER SHORTWAVE TROF EMBEDDED SLIDING THROUGH THE UPPER RIDGE OVER
THE STATE ATTM...BROUGHT A FEW CLOUDS TO THE WEST COUNTIES AND SOME
LIGHT SPRINKLES CENTRAL.  TEMPERATURES HAVE APPROACHED DEWPOINTS
WITH SOME LOWER MVFR STRATUS DEVELOPING OVER THE FAR EASTERN
COUNTIES.

MAY BE A STRUGGLE TO GET LOWER CLOUDS AND FOG FARTHER WEST AND NORTH
GIVEN MID LEVEL CLOUD DEVELOPMENT...AND LIGHTNING WINDS IN THE
ADVECTIVE LAYER. WILL KEEP PATCHY FOG FOR THE EASTERN TWO THIRDS
THROUGH 12Z. AFTER OVERNIGHT LOWS NEAR 60...SHOULD GET HIGH
TEMPERATURES INTO THE LOWER TOWARD MIDDLE 80S AS THE UPPER RIDGE
CONTINUES TO MOVE EASTWARD OVER THE CENTRAL US AND KEEP PRECIP
CHANCES IN CHECK JUST ONE MORE DAY.  67

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 400 AM CDT FRI MAY 17 2013

AN ACTIVE PERIOD LOOKS TO BE ON TAP FOR MOST OF EASTERN KANSAS THIS
WEEKEND ...WITH SUNDAY LIKELY BEING THE MORE ACTIVE OF THE TWO DAYS.
A VERY POTENT NEGATIVELY TILTED MID LEVEL TROUGH WILL SLOWLY SWING
THROUGH THE AREA THROUGH THE WEEKEND BRINGING AT LEAST ONE VERY
ACTIVE DAY OF STRONG TO SEVERE THUNDERSTORMS.

BY THIS WEEKEND A STRONG SURFACE LOW ASSOCIATED WITH THE
PREVIOUSLY MENTIONED H5 TROUGH WILL FORM OVER THE HIGH
PLAINS...BRINGING A STRONG SURGE OF GULF MOISTURE INTO THE CENTRAL
PLAINS AND PUTTING EASTERN KANSAS SOLIDLY IN A WARM/MOIST SECTOR
CHARACTERIZED BY TEMPS IN THE 70S-80S WITH DEWPOINTS IN THE MID TO
UPPER 60S. STARTING WITH SATURDAY A STRONG CAPPING INVERSION WILL
BE IN PLACE OVER THE FORECAST AREA THROUGHOUT THE DAY...MAKING
DIURNALLY DRIVEN WARM SECTOR THUNDERSTORMS VERY UNLIKELY. WHAT MAY
BE A CONCERN FOR SATURDAY NIGHT WOULD BE THE POTENTIAL FOR A FEW
THUNDERSTORMS TO GO UP ON THE DRY LINE IN SOUTH CENTRAL KANSAS
DURING SATURDAY AFTERNOON/EVENING AND ADVECTING EASTWARD. SHORT
RANGE HI-RES MODELS SEEM TO BE INCREASINGLY CONVERGING TOWARD A
SOLUTION THAT INDICATES A COUPLE OR FEW STORMS WILL GO UP IN SC/C
KANSAS. SHOULD THESE STORMS FORM AND HOLD TOGETHER OVERNIGHT THEY
WOULD BRING A CHC/SCHC FOR OVERNIGHT SHOWERS AND THUNDERSTORMS TO
AREAS OF EASTERN KANSAS. GIVEN THAT THERMAL PROFILES ARE VERY
CAPPED THE THUNDERSTORM ACTIVITY WOULD LIKELY HAVE TO BE ELEVATED
SHOULD IT BE ABLE TO OVERCOME THE VERY WARM LOW/MID LEVEL TEMPS.
SEEING AS THOUGH A SCENARIO IN WHICH STRONG STORMS ARE ABLE TO
OVERCOME THAT CAPPING INVERSION KEPT POPS VERY LOW FOR THE
SATURDAY NIGHT PERIOD.

THE FOCUS THEN SHIFTS TO SUNDAY...WHICH WOULD BRING THE MORE LIKELY
PERIOD FOR STRONG TO SEVERE THUNDERSTORMS FOR MOST OF EASTERN
KANSAS. AS SOUTHERLY FLOW CONTINUES TO BRING RICH GULF MOISTURE INTO
THE FORECAST AREA IT WILL PRIME EASTERN KANSAS FOR ROBUST CONVECTION
SUNDAY AFTERNOON. FORECAST SOUNDINGS FOR THE FIRST HALF OF SUNDAY
LOOK RATHER CAPPED OFF DUE TO THE WARM TEMPERATURES BETWEEN 700 AND
800 MB. HOWEVER AS THE DAY PROGRESSES THE STRONG NEGATIVE TILT
TROUGH WILL MOVE INTO THE AREA BRINGING A LARGE AMOUNT OF LARGE
SCALE ASCENT AS WELL AS COOLING MID LEVELS...WHICH WILL ACT TO
INCREASE LAPSE RATES AND ERODE THE CAP. EXPECT ML CAPE VALUES ON
SUNDAY TO TOP 2500 J/KG...AND MAY REACH AS HIGH AS 3500 J/KG AHEAD
OF THE APPROACHING TROUGH. ONCE STORMS FIRE THEY WILL HAVE QUITE A
BIT OF INSTABILITY AND 0-6 KM SHEAR OF AROUND 30 TO 40 KTS. THESE
PARAMETERS WILL BE CONDUCIVE TO SUPERCELL DEVELOPMENT...WITH
STRONG WINDS AND LARGE HAIL BEING THE PRIMARY SEVERE WEATHER
THREATS FOR SUNDAY. REGARDING THE TORNADO THREAT...IT DOES SEEM
LIKE THERE WILL BE ENOUGH LOW LEVEL SHEAR TO BRING ABOUT A TORNADO
THREAT FOR SUNDAY...ESPECIALLY IN THE WARM SECTOR. NAM 0-1 SRH
VALUES FOR SUNDAY AFTERNOON IN THE PROXIMITY OF WHERE STORMS WILL
FIRE IS IN THE 100-150 J/KG RANGE...WHICH IS ENOUGH TO WARRANT A
TORNADO THREAT. SOME MITIGATING FACTORS TO HAVING A TORNADO THREAT
IS THE FACT THAT THE LOW LEVEL HODOGRAPHS ARE NOT EXCEEDINGLY
CURVY...AND IN FACT ARE RATHER STRAIGHT AS THE WINDS INCREASING
WITH HEIGHT ARE EITHER UNIDIRECTIONAL OR PERHAPS A LITTLE BACKED
WITH HEIGHT. ANOTHER MITIGATING FACTOR FOR TORNADO OCCURRENCE IS
THAT WITH THE STRONG FORCING ENTERING THE AREA STORM COVERAGE
COULD BE RATHER LARGE...MAKING STORM SEEDING SOMEWHAT PROBLEMATIC
FOR WIDESPREAD TORNADO OCCURRENCE. GIVEN THE FACT THAT BOTH
AGGRAVATING AND MITIGATING FACTORS WILL BE PRESENT FOR SUNDAY WILL
MENTION THE POSSIBILITY OF AN ISOLATED TORNADO OR TWO...BUT CANNOT
GET EXTREMELY CONCERNED ABOUT WIDESPREAD TORNADOES AT THIS POINT.

THE AREA MOST LIKELY FOR HIGH IMPACT SEVERE WEATHER ON SUNDAY WOULD
LIKELY BE ACROSS THE EASTERN HALF OF THE FORECAST AREA...AND EVEN
MORE SO ACROSS AREAS ALONG AND SOUTHEAST OF THE KANSAS TURNPIKE.

STORMS WILL LIKELY GROW UPSCALE IN COVERAGE AND PROBABLY FORM AN MCS
WHICH WILL THEN MOVE OUT OF THE AREA AND TO THE EAST BY SUNDAY
NIGHT...BRINGING A BRIEF END TO CONVECTIVE CHANCES BEFORE ANOTHER
ROUND OF STORMS BECOMES POSSIBLE ON MONDAY.

EXTENDED FORECAST (MONDAY THROUGH THURSDAY)...

00Z ECMWF INDICATES THAT A RATHER NON PROGRESSIVE COLD FRONT WILL NOT
QUITE CLEAR THE AREA MONDAY NIGHT...LEAVING PART OF THE FORECAST
AREA IN THE WARM SECTOR FOR MONDAY. WHILE THE STRONGER SEVERE
WEATHER THREAT WILL LIKELY RESIDE SOUTH AND EAST OF THE FORECAST
AREA...AT LEAST THE SOUTHEASTERN 1/3 OF THE CWA WILL REMAIN IN AN
ENVIRONMENT SIMILAR TO SUNDAY...SO WILL HOLD ON TO SEVERE WEATHER
CHANCES FOR FAR NORTHEAST AND EAST CENTRAL KANSAS FOR MONDAY...WITH
STRONG WINDS...LARGE HAIL...AND PERHAPS AN ISOLATED TORNADO OR TWO
BEING THE THREATS. WILL ELABORATE ON MONDAY`S THREAT MORE AS IT
APPROACHES.

FOR TUESDAY AND WEDNESDAY ALL OF THE FORECAST AREA SHOULD GET A
REPRIEVE FROM THE THUNDERSTORMS AS THE COOLER/DRIER AIR WORKS ITS
WAY INTO THE AREA. TEMPERATURES SHOULD BE CLOSE TO SEASONAL NORMS
WITH HIGHS IN THE 70S AND LOWS IN THE 50S THROUGH THE WEEK. NEXT
CHANCE FOR STORMS COULD COME LATER IN THE WEEK...TOWARD THE WEEKEND
AS SOUTHERLY RETURN FLOW COMES BACK TO THE AREA...WITH SOME WARM AIR
ADVECTION ELEVATED THUNDERSTORMS AFFECTING AREAS WEST OF HERE...THEN
MOVING IN LATE IN THE WEEK.

JL

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 625 AM CDT FRI MAY 17 2013

TOP/FOE BOTH HAVE LOW CLOUDS AND REDUCED VISBY MOVING INTO THE
AREA ATTM. THINK IT WILL WARM UP ENOUGH AS THE SUN COMES UP TO
RAISE THE CIGS UP AND SCATTER IT OUT...ALTHOUGH A FEW MODELS
SUGGEST IT STAYS CLOUDY MUCH OF THE DAY. THINK THE DECK IS TOO
SHALLOW AND SUN TOO STRONG FOR THIS AND WILL SCATTER OUT AROUND
14/15Z.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...CRAVEN
LONG TERM...LEIGHTON
AVIATION...67