Severe Thunderstorm Warning 141, NWS Topeka, KS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
640 PM CDT WED JUL 14 2010

.UPDATE...

UPDATED FOR 00Z AVIATION.

&&

.DISCUSSION...

SEE PREVIOUS DISCUSSION.

&&

.AVIATION...

VFR CONDITIONS WILL LARGELY PREVAIL THROUGH THE TAF PERIOD.
EXCEPTION WILL RESIDE WITH ANY CONVECTIVE ACTIVITY IMPACTING TAF
SITES OVERNIGHT INTO TOMORROW...ALTHOUGH PREDICTABILITY IS TOO
LOW FOR TEMPO GROUP ATTM. BEST CHANCES FOR VICINITY CONVECTION
WILL BE AFTER 04-06Z...WITH CHANCES CONTINUING INTO THU.

BLAIR

&&

.PREV DISCUSSION... /ISSUED 325 PM CDT WED JUL 14 2010/

DISCUSSION...

HOT AND HUMID CONDITIONS CONTINUE TODAY ACROSS THE AREA WITH HIGH
TEMPS IN THE MID 90S IN THE EAST AND UPPER 90S WEST. DEWPOINT
TEMPS ARE IN THE MID TO UPPER 70S AND BRINGING DANGEROUS HEAT
INDICES OF 105 TO AROUND 110 ACROSS MOST OF THE AREA. SOME MIXING
HAS BROUGHT TDS DOWN A FEW DEGREES FAR WEST KEEPING THE NUMBERS
ACROSS THE AREA GENERALLY IN ADVISORY CRITERIA. WEAK CONVECTION
ONGOING ACROSS NEBRASKA ATTM WITH STRONGER FRONT BACK WESTWARD.

WILL LET ADVISORY GO AS SCHEDULED AROUND 9PM WHEN HEAT INDICES
SHOULD BE FALLING. CONCERN BEYOND THE HEAT WILL BE CHANCES FOR
STRONG CONVECTION THIS EVENING AND OVERNIGHT AS FRONT MOVES INTO
THE AREA. FACTORS IN FAVOR FOR STRONG TO SEVERE STORM DEVELOPMENT
ARE STEEP LAPSE RATES BETWEEN 800-600MB AND NEARLY 2 INCHES OF PW
IN THE MORNING SOUNDING. HOWEVER SHEAR IS WEAK...AND CURRENT
CONVERGENCE ALONG THE FRONT IS ALSO. FLOW ALOFT IS WESTERLY AND
PARALLEL TO THE FRONT...AND APPEARS TO LACK A SYNOPTIC FEATURE TO
TRIGGER STORMS IN OUR AREA. BETTER CHANCE WILL LIKELY BE FOR
STORMS TO DEVELOP IN NEBRASKA AND PROPAGATE SE INTO OUR CWA...BUT
WILL ENCOUNTER A WEAK LLJ THAT CONTINUES TO WEAKEN IN THE
OVERNIGHT HOURS. FOR SENSIBLE WX FCST KEPT LIKELY POPS FOR 0-6Z
HOURS ACROSS THE NORTH AND SPREAD THOSE SOUTH AND EAST AFTER
MIDNIGHT. STORMS COULD BRING STRONG WINDS AND HAIL...AND WITH
STRENGTH OF THE MID LEVEL LAPSE RATES AND ENHANCED STRETCHING CAN
SEE A SMALL TORNADO THREAT AS WELL. SPEED OF THE FRONT WILL
LIKELY BE ACCELERATED BY STORM OUTFLOWS AND WILL MAKE TRUE
POSITION DIFFICULT TO DISCERN FOR THURSDAYS WEATHER. MORE CLOUDS
OR EARLY RAIN MAY DECREASE THE HEAT THREAT AND WILL NOT CARRY AN
ADVISORY AT THIS TIME. WILL HAVE HIGHS IN THE UPPER 80S TO LOWER
90S EAST TO WEST ACROSS THE AREA.

THE SURFACE FRONT SETTLES INTO THE OZARKS THURSDAY NIGHT AND
FRIDAY. SURFACE HIGH PRESSURE WILL BUILD ACROSS THE CENTRAL
PLAINS TAKING THE EDGE OFF THE RECENT HOT AND HUMID WEATHER.
HOWEVER...HIGH TEMPERATURES WILL STILL REACH THE LOWER TO MID 90S
WITH PRECIPITABLE WATER VALUES LINGERING AROUND AN INCH TO AN
INCH AND A HALF.

THE SURFACE HIGH BUILDS TO THE EAST WITH THE SOUTHWEST UPPER
LEVEL RIDGE BUILDING INTO THE PLAINS. A SURFACE TROUGH ACROSS THE
HIGH PLAINS WILL DEEPEN WITH THE APPROACH OF AN UPPER TROUGH
DIGGING ACROSS THE NORTHERN PLAINS. SOUTHERLY FLOW WILL INCREASE
IN RESPONSE TO A TIGHTER PRESSURE GRADIENT ACROSS THE REGION
LIFTING A WARM FRONT NORTH THROUGH THE PLAINS.

THIS FRONT IS EXPECTED TO LINGER ALONG THE NEBRASKA BORDER. THE
GFS AND ECMWF DEPICT UPPER FLOW TRANSITIONING TO THE NORTHWEST.
SHORTWAVES MOVING THROUGH THIS FLOW INTERACTING WITH THE FRONT
AND AN UNSTABLE AIRMASS WILL BRING THE POTENTIAL OF AN MCS
SUNDAY. ADDITIONAL THUNDERSTORMS WILL BE POSSIBLE MONDAY BEFORE
BOUNDARY LIFTS NORTH OF THE AREA MID WEEK.

67

&&

.TOP WATCHES/WARNINGS/ADVISORIES...HEAT ADVISORY UNTIL 9 PM WEDNESDAY FOR KSZ008-KSZ009-KSZ010-
KSZ011-KSZ012-KSZ020-KSZ021-KSZ022-KSZ023-KSZ024-KSZ026-KSZ034-
KSZ035-KSZ036-KSZ037-KSZ038-KSZ039-KSZ040-KSZ054-KSZ055-KSZ056-
KSZ058-KSZ059.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TOPEKA KS
421 AM CDT WED JUL 14 2010

KSZ008>012-020>024-026-034>040-054>056-058-059-151000-
REPUBLIC-WASHINGTON-MARSHALL-NEMAHA-BROWN-CLOUD-CLAY-RILEY-
POTTAWATOMIE-JACKSON-JEFFERSON-OTTAWA-DICKINSON-GEARY-MORRIS-
WABAUNSEE-SHAWNEE-DOUGLAS-LYON-OSAGE-FRANKLIN-COFFEY-ANDERSON-
421 AM CDT WED JUL 14 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL...NORTH
CENTRAL AND NORTHEAST KANSAS.

.DAY ONE...TODAY AND TONIGHT

AFTERNOON HEAT INDICES IN THE 105 TO 100 DEGREE RANGE ARE EXPECTED
TODAY AND A HEAT ADVISORY REMAINS IN EFFECT THROUGH EARLY EVENING.

THUNDERSTORMS ARE POSSIBLE LATE THIS AFTERNOON IN FAR NORTH
CENTRAL KANSAS AHEAD OF AN APPROACHING COLD FRONT. THUNDERSTORMS
ARE EXPECTED TO BECOME MORE WIDESPREAD THIS EVENING AND TONIGHT AS
THE FRONTAL BOUNDARY MOVES ACROSS THE AREA. SOME OF THE STORMS MAY
BE SEVERE WITH DAMAGING WINDS...LARGE HAIL AND ISOLATED TORNADOES
ALL POSSIBLE.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORM CHANCES WILL CONTINUE THURSDAY AND THURSDAY NIGHT
ACROSS THE OUTLOOK AREA. THUNDERSTORMS WILL AGAIN BE POSSIBLE
NEAR THE NEBRASKA BORDER ON MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS AFTERNOON AND TONIGHT.

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