Thursday, October 21, 2010

Area Forecast Discussion - South Central/Southwest Missouri

FXUS63 KSGF 211637
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
1137 AM CDT THU OCT 21 2010

..UPDATE TO AVIATION...

SHORT TERM (TONIGHT THROUGH SATURDAY NIGHT)...

THE MAIN FORECAST CHALLENGE FOR THE SHORT TERM WILL BE INCREASING
CHANCES FOR SHOWERS AND THUNDERSTORMS...AS WELL AS THE POTENTIAL
FOR SEVERE STORMS ON SATURDAY.

CURRENTLY...A SURFACE RIDGE AXIS EXTENDS FROM THE EASTERN
DAKOTAS...SOUTH THROUGH WESTERN MISSOURI AND INTO THE LOWER
MISSISSIPPI VALLEY. IN THE UPPER LEVELS...WEAK HEIGHT RISES WILL
OVERSPREAD THE REGION TODAY...AS THE SURFACE RIDGE AXIS SLOWLY
SLIDES EAST. DRY WEATHER AND SLIGHTLY ABOVE NORMAL TEMPERATURES
ARE EXPECTED THROUGH TONIGHT...WITH A GRADUAL INCREASE IN HIGH
CLOUDS.

BIG CHANGES ARE THEN ON THE WAY FOR THE LATE WEEK PERIOD AS A
STRONG UPPER LEVEL LOW BEGINS TO PULL NORTHEAST OUT OF THE DESERT
SOUTHWEST. WITH THE LOW QUICKLY TAKING ON A NEGATIVE TILT...STRONG
UPPER LEVEL DIFFLUENCE WILL BEGIN TO OVERSPREAD THE AREA LATE IN
THE DAY. WILL INITIALLY HAVE TO WATCH FOR THE REMNANTS OF
OVERNIGHT SHOWERS AND THUNDERSTORMS PUSHING NORTHEAST OUT OF
OKLAHOMA FRIDAY MORNING. BETTER CHANCES FOR SHOWERS AND A FEW
THUNDERSTORMS MAY THEN COME LATE FRIDAY ACROSS SOUTHEAST KANSAS AND
WESTERN MISSOURI AS LOW LEVEL ISENTROPIC UPGLIDE BEGINS TO BECOME
JUXTAPOSED WITH THE UPPER LEVEL DIFFLUENCE. THE BEST DEEP
TROPOSPHERIC ASCENT STILL APPEARS LIKE IT WILL OCCUR FRIDAY
NIGHT...ESPECIALLY ACROSS EASTERN KANSAS AND THE WESTERN HALF OF
MISSOURI. LIKELY POPS WERE MAINTAINED ACROSS THIS AREA...WITH
CHANCE POPS ACROSS FAR SOUTH CENTRAL MISSOURI.

AS WOULD BE EXPECTED THREE DAYS OUT...THERE ARE STILL QUITE A FEW
QUESTIONS REGARDING SEVERE STORM POTENTIAL ON SATURDAY. THE FIRST
QUESTION WILL BE HOW QUICKLY THE FRIDAY NIGHT SHOWERS AND
THUNDERSTORMS CAN SHUNT EAST...ALLOWING FOR THE ATMOSPHERE TO
DESTABILIZE. THE SECOND QUESTION WOULD THEN BE WHERE AND WHEN
ADDITIONAL...LIKELY-SURFACE BASED...CONVECTION WOULD FIRE. MODELS
CONTINUE TO INDICATE A SECONDARY VORTICITY LOBE SWINGING AROUND
THE SOUTHERN FLANK OF THE UPPER LEVEL LOW LATER IN THE DAY ON
SATURDAY. IF THIS HAPPENS...IT IS QUITE POSSIBLE THAT WE SEE A DRY
LINE SURGE ACROSS KANSAS AND OKLAHOMA. CONVERGENCE ALONG THE DRY
LINE AND HEIGHT FALLS OVERSPREADING IT FROM THE WEST SHOULD BE
ENOUGH TO GET MORE STORMS GOING. KINEMATIC FIELDS WOULD SUGGEST
STORMS MOVING EAST NORTHEAST OFF THE DRY LINE. MODELS CONTINUE TO
PROG 0 TO 6 KM BULK SHEAR VALUES IN THE 40 TO 50 KNOT RANGE...WITH
A GOOD CROSS COMPONENT TO THE DRY LINE. IF ENOUGH INSTABILITY CAN
THEREFORE BE REALIZED...SUPERCELLS WOULD BE THE LIKELY STORM MODE
FROM SATURDAY AFTERNOON INTO SATURDAY EVENING. HODOGRAPHS WILL
ALSO INCREASE IN SIZE BY SATURDAY EVENING AS A LOW LEVEL JET
STRENGTHENS AND VEERS INTO THE REGION. THIS WOULD MAKE ALL MODES
OF SEVERE POSSIBLE...INCLUDING TORNADOES. AGAIN...THERE ARE A LOT
OF QUESTIONS YET TO BE ANSWERED...SO KEEP UP WITH THE FORECAST.

SCHAUMANN

&&
LONG TERM (SUNDAY THROUGH WEDNESDAY)...

BY THE START OF THE EXTENDED PERIOD...A SECONDARY UPPER TROUGH
SHOULD BE WORKING ITS WAY THROUGH CENTRAL MO...WITH PRECIP
ALONG/AHEAD OF IT. BEST CHANCES FOR PRECIP SHOULD BE DURING THE
DAY SUNDAY...WITH RAIN ENDING RATHER QUICKLY BY LATE EVENING AS
NEG VORT ADVECTION DOES ITS WORK. VERY STRONG 160 KT+ UPPER JET
LOOKS TO PUNCH ITS WAY ACROSS THE CENTRAL U.S. BY
TUESDAY...RESULTING IN SWIFT BUT ZONAL FLOW ACROSS THE CONUS.
PATTERN LOOKS TO AMPLIFY AT THE END OF THE PERIOD...WITH CLOUD
COVER INCREASING AHEAD OF APPROACHING UPPER TROUGH...AND POTENTIAL
FOR AN IMPRESSIVE COOL DOWN BY NEXT WEEKEND.

BOXELL

&&

AVIATION...

FOR THE 18Z TAFS...STILL LOOKING FOR VFR CONDITIONS THROUGH THE
PERIOD. CHANGES ARE ON THE HORIZON HOWEVER AS AN UPPER LEVEL
SYSTEM BEGINS TO LIFT OUT OF THE DESERT SOUTHWEST AND INTO THE
HIGH PLAINS BY 18Z FRI. GOOD UPPER LEVEL DIVERGENCE WILL BEGIN TO
TAKE PLACE OVER EASTERN KANSAS AND WESTERN MISSOURI AND WILL SEE
AN INCREASE IN MID/UPPER LEVEL MOISTURE ALONG WITH A POSSIBILITY
OF SCATTERED HIGH BASED SHOWERS. FOR NOW WILL LEAVE PRECIPITATION
OUT OF TAFS AS A LARGE COVERAGE IS NOT EXPECTED DUE TO THE DRY LOW LEVELS.

LINDENBERG

&&

FIRE WEATHER...

LOW LEVEL WINDS WILL INCREASE OUT OF THE SOUTHEAST ON FRIDAY AS
SURFACE LOW PRESSURE STRENGTHENS OVER THE HIGH PLAINS. DESPITE THE
SOUTHEAST WINDS...MOISTURE WILL BE SLOW TO INCREASE ACROSS CENTRAL
MISSOURI. WITH MINIMUM RELATIVE HUMIDITIES EXPECTED TO DROP INTO
THE 25 TO 30 PERCENT RANGE FRIDAY AFTERNOON...THERE IS AN ELEVATED
FIRE WEATHER CONCERN EAST OF HIGHWAY 65.

SCHAUMANN

&&

SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

$$

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