Saturday, July 24, 2010

Area Forecast Discussion - South Central/Southwest Missouri

FXUS63 KSGF 241525
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1025 AM CDT SAT JUL 24 2010

..MESOSCALE CONVECTIVE DISCUSSION...
..18Z RAOB PLANNED...

UPDATE...

THE MESOSCALE ENVIRONMENT ACROSS THE AREA THIS MORNING LOOKS
FAVORABLE FOR THUNDERSTORM DEVELOPMENT DURING THE LATE MORNING
INTO THE AFTERNOON. THE PRIMARY THREAT WILL BE SEVERE WIND GUSTS.

CURRENTLY...SKIES ARE MOSTLY CLEAR OVER ALL OF SOUTHWEST MISSOURI
AND SOUTHEAST KANSAS AHEAD OF A FRONTAL BOUNDARY THAT IS ADVANCING
INTO THE AREA FROM THE NORTHWEST. THERE ARE A FEW LOWER LEVEL
CONVECTIVE CLOUDS FORMING OVER SOUTHEAST KANSAS...BUT STABLE WAVE
FEATURES WITHIN THE CLOUD COVER INDICATE THAT SOME CAPPING IS IN
PLACE TO THE WEST. THE 12 SGF SOUNDING INDICATES A CONVECTIVE
TEMPERATURE OF AROUND 91 DEGREES...A TEMPERATURE THAT COULD BE
REACHED AS EARLY AS NOON. THE TOP SOUNDING INDICATES MORE CAPPING
IN PLACE DIRECTLY AHEAD OF THE FRONTAL BOUNDARY...HOWEVER ELEVATED
CONVECTION HAS BEEN ABLE TO FIRE ABOVE THE CAPPING INVERSION WITH
ASSISTANCE FROM PRESSURE ADVECTION.

THESE OBSERVED FEATURES MATCH WELL WITH RUC INITIALIZATIONS. RUC
INDICATES WIDESPREAD INHIBITION VALUES ON THE ORDER OF 100 J/KG AHEAD
OF THE FRONT. FORECAST VALUES STEADILY ERODE THROUGH THE MORNING
AND DIMINISH TO NEAR ZERO BY 19Z. THIS MATCHES WELL WITH THE
CONVECTIVE TEMPERATURES FROM THE OBSERVED SOUNDINGS. MLCAPE VALUES
THIS AFTERNOON ON THE ORDER OF 3000 J/KG ARE EXPECTED OVER CENTRAL
MISSOURI AHEAD OF THE FRONTAL BOUNDARY.

INSTABILITY WILL DEFINITELY BE SUFFICIENT FOR VIGOROUS CONVECTIVE
DEVELOPMENT THIS AFTERNOON ALONG AND AHEAD OF THE FRONTAL FORCING.
STORM TYPE IS THE MORE CHALLENGING FORECAST. WIND SHEAR IN GENERAL
IS LACKING. THE MAIN UPPER LEVEL DYNAMICS ASSOCIATED WITH THE FRONT
HAVE PUSHED WELL TO THE EAST...LEAVING THE FRONTAL BOUNDARY TO OUR
NORTHWEST WITHOUT STRONG UPPER LEVEL SUPPORT. 15 TO 20 KTS OF DEEP
LAYER SHEAR WILL BE AVAILABLE ALONG THE FRONTAL BOUNDARY. THIS COULD
SUPPORT SOME STORM ORGANIZATION. ANY STRONGER UPDRAFTS THAT DO FORM
COULD PRODUCE HAIL...BUT FREEZING LEVELS REMAIN NEAR 17KFT AND LAPSE
RATES IN THE HAIL GROWTH ZONE ARE NOT OVERLY FAVORABLE. EASTERLY
STORM MOTIONS OF AROUND 15 KT OUT AHEAD OF THE FRONTAL BOUNDARY MAY
BALANCE WELL WITH THE FORECAST 10 KT SOUTHEASTERLY MOTION OF THE
FRONTAL BOUNDARY. THIS WOULD FAVOR STORMS REMAINING ALONG THE
MECHANISM OF FORCING AND WOULD PROMOTE STRONGER MULTICELL
STRUCTURE. ANY MULTICELLS THAT DO ORGANIZE ALONG THE FRONT
WILL...GIVEN THE PWAT VALUES APPROACHING TWO INCHES IN CONJUNCTION
WITH A 4 TO 5 DEGREE DEWPOINT SPREAD NEAR 700MB...HAVE THE POTENTIAL
TO PRODUCE SEVERE WIND GUSTS.

KARDELL

&&

DISCUSSION...

MAIN FOCUS IN THIS FORECAST PACKAGE WILL DEAL WITH HOT AND MUGGY
CONDITIONS AGAIN THIS AFTERNOON...THEN ATTENTION TURNS TO
AN APPROACHING COLD FRONT AND ASSOCIATED SHOWER AND THUNDERSTORM
CHANCES THIS AFTERNOON INTO THE START OF THE WORK WEEK.

AN UPPER LEVEL TROUGH IS CURRENTLY PUSHING EAST ACROSS THE
NORTHERN PLAINS EARLY THIS MORNING. THIS TROUGH WILL CONTINUE TO
PUSH EAST INTO THE GREAT LAKES REGION TODAY. AS THIS FEATURE
PUSHES EAST IT WILL FLATTEN THE RIDGE AND WEAKEN THE CAP THAT HAVE
BEEN PARKED OVER THE REGION THE LAST FEW DAYS. IT WILL ALSO PUSH A
COLD FRONT TOWARDS THE AREA...THAT CURRENTLY EXTENDS FROM EAST
CENTRAL COLORADO TO THE NORTHEAST THROUGH PORTIONS OF NEBRASKA AND
IOWA EARLY THIS MORNING.

A HOT AND MUGGY AIRMASS WILL REMAIN IN PLACE AHEAD OF THE FRONT AS
DEWPOINTS WILL REMAIN IN THE LOW TO MIDDLE 70S. THE COLD FRONT
SHOULD BEGIN TO APPROACH THE NORTHERN PORTIONS OF THE CWA LATE
THIS AFTERNOON INTO THE EVENING HOURS...WHICH WILL BRING
INCREASING CLOUD COVER AND CHANCES FOR THUNDERSTORMS TO THE AREA.
THINK THE ARRIVAL OF THE FRONT AND ASSOCIATED CLOUD COVER AND
CONVECTION MAY BE LATE ENOUGH TO ALLOW HEAT INDEX VALUES TO NEAR
HEAT ADVISORY CRITERIA ACROSS THE NORTHERN CWA. THE FRONT SHOULD
HAVE LITTLE EFFECT ON TEMPERATURES AND HEAT INDEX VALUES ACROSS
THE SOUTHERN CWA THIS AFTERNOON. THEREFORE...WILL LET THE CURRENT
HEAT ADVISORY RIDE AS IS FOR THE ENTIRE AREA THROUGH THIS AFTERNOON.
IT IS POSSIBLE THE FRONT AND ITS ASSOCIATED CLOUD COVER AND
CONVECTION PUSHES SOUTH A LITTLE FASTER WHICH COULD LIMIT
TEMPERATURES SOME ACROSS THE NORTHERN CWA.

THE FRONT IS EXPECTED TO BE THE FOCUS FOR THUNDERSTORMS ACROSS THE
AREA LATE THIS AFTERNOON INTO THE EARLY EVENING HOURS....WITH THE
BEST CHANCES ALONG AND NORTH OF THE INTERSTATE 44 CORRIDOR. WIND
SHEAR WILL REMAIN ON THE WEAK SIDE ACROSS THE AREA...AS THE BETTER
SHEAR WILL BE NORTH OF THE AREA CLOSER TO THE UPPER LEVEL TROUGH.
TEMPERATURES IN THE 90S AND HIGH LOW LEVEL MOISTURE WILL RESULT IN
AN UNSTABLE AIRMASS AS MLCAPE VALUES OF 3000 TO 4000 J/KG ARE
EXPECTED. THERE WILL BE THE POTENTIAL FOR A FEW STRONG TO SEVERE
STORMS ALONG AND NORTH OF THE INTERSTATE 44 CORRIDOR THROUGH
SUNSET. THE MAIN HAZARD EXPECTED WITH THIS ACTIVITY WILL BE STRONG
WIND GUSTS...MAINLY ASSOCIATED WITH ANY LINE SEGMENTS THAT CAN
DEVELOP. THE LACK OF DEEP LAYER SHEAR WILL LIMIT THE SEVERE HAIL
RISK...HOWEVER GIVEN THE EXPECTED AMOUNT OF INSTABILITY CANNOT
RULE OUT A SMALL HAIL RISK. PRECIPITABLE WATER VALUES WILL BE ON
THE HIGH SIDE AS VALUES AROUND TWO INCHES ARE EXPECTED. AS A
RESULT HIGH RAINFALL RATES WILL BE POSSIBLE WHICH COULD LEAD TO
THE POTENTIAL FOR HEAVY RAINFALL AND LOCALIZED FLOODING WITH THE
STRONGER STORMS. THE LOW LEVEL JET IS EXPECTED TO REMAIN ON THE
WEAK SIDE OVERNIGHT TONIGHT...SO EXPECT THE THUNDERSTORM ACTIVITY
AND SEVERE POTENTIAL TO WEAKEN AND DISSIPATE AFTER SUNSET INTO THE
OVERNIGHT HOURS.

A FEW PULSE THUNDERSTORMS WILL ALSO BE POSSIBLE ACROSS THE AREA
THIS AFTERNOON AHEAD OF THE FRONT...AS A RESULT OF INCREASED MID LEVEL
MOISTURE SPREADING INTO THE AREA AND THE CAP WEAKENING.

THE FRONT SHOULD REMAIN OVER THE AREA ON SUNDAY AND SHOULD BE THE
FOCUS FOR ADDITIONAL THUNDERSTORM CHANCES...WITH THE BEST CHANCES
DURING THE AFTERNOON AS INSTABILITY INCREASES WITH THE HEATING OF
THE DAY. THE FRONT WILL ALSO RESULT IN COOLER TEMPERATURES ACROSS THE
AREA SUNDAY INTO THE START OF THE WORK WEEK. THE FRONT IS EXPECTED
TO THEN LIFT BACK TO THE NORTH AND KEEP THUNDERSTORM CHANCES IN
THE FORECAST INTO TUESDAY.

THE REMNANTS OF TROPICAL STORM BONNIE MAY ALSO AID IN SHOWER AND
THUNDERSTORM CHANCES ACROSS THE AREA EARLY NEXT WEEK. EXPECT THE
UPPER LEVEL DISTURBANCE ASSOCIATED WITH BONNIE TO MEANDER ACROSS
PORTIONS OF THE SOUTHERN PLAINS AND EVENTUALLY WASHING OUT THROUGH
THE MIDDLE OF NEXT WEEK...AS THIS FEATURE WILL BE UNDER THE UPPER
LEVEL RIDGE WITH NOTHING TO PUSH IT OFF TO THE EAST. THIS FEATURE
WILL HELP TO FEED GULF MOISTURE INTO THE AREA...WHICH COULD RESULT
IN THE POTENTIAL FOR PULSE TYPE THUNDERSTORMS EACH AFTERNOON
THROUGH THE MIDDLE OF NEXT WEEK. THE UPPER LEVEL RIDGE IS EXPECTED
TO BUILD BACK OVER THE AREA DURING THE MIDDLE OF THE WEEK
RESULTING IN A RETURN TO THE WARMER CONDITIONS.

WISE

&&

AVIATION...

FOR THE 12Z TAFS...BAND OF CONVECTION CURRENTLY DEVELOPING ALONG
FRONTAL BOUNDARY FROM NORTH CENTRAL KANSAS INTO SOUTHEAST IOWA AND
NORTHERN ILLINOIS. FRONT IS EXPECTED TO DROP SOUTH TODAY AS STRONG
SHORTWAVE SHIFTS EAST FROM THE UPPER MISSISSIPPI VALLEY INTO THE
GREAT LAKES. CONVECTION SHOULD CONTINUE ALONG THE FRONT AS IT
MOVES INTO THE AREA AND WILL GO WITH VICINITY WORDING IN TAFS FROM
THE LATE AFTERNOON THROUGH THE MID EVENING. CONVECTION SHOULD
DIMINISH AFTER SUNSET BY LATE EVENING WITH LOSS OF HEATING AND
DECREASING INSTABILITY. FOR NOW HAVE KEPT VFR CONDITIONS GOING IN
THE TERMINAL FORECASTS BUT MVFR OR IFR CONDITIONS MAY DEVELOP IF
THUNDERSTORM DIRECTLY AFFECTS FORECAST POINT.

LINDENBERG

&&

SGF WATCHES/WARNINGS/ADVISORIES...
MO...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR MOZ055>058-066>071-
077>083-088>098-101>106.

KS...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR KSZ073-097-101.

&&

$$


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