Friday, October 22, 2010

Area Forecast Discussion - South Central/Southwest Missouri

FXUS63 KSGF 220811
AFDSGF

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
311 AM CDT FRI OCT 22 2010

DISCUSSION...
/ISSUED 255 AM CDT FRI OCT 22 2010/

SHORT TERM (TODAY THROUGH SUNDAY)...

COMPLEX SHORT TERM FORECAST ON TAP...WITH A VARIETY OF FORECAST
CONCERNS...INCLUDING MULTIPLE ROUNDS OF SHOWERS/THUNDERSTORMS AND
SEVERE WEATHER POTENTIAL OVER THE NEXT 48 HOURS.

WATER VAPOR IMAGERY EARLY THIS MORNING NICELY DEPICTS LARGE UPPER
LOW SPINNING NEAR THE FOUR CORNERS REGION...WITH LEAD SHORTWAVE
TROUGH AND ASSOCIATED SHOWER AND THUNDERSTORM ACTIVITY LIFTING NORTH
OVER NORTHERN AND WESTERN OKLAHOMA AND SOUTHWESTERN KANSAS. EXPECT
HIGH CLOUD COVER FROM THIS ACTIVITY TO CONTINUE TO STREAM INTO THE
CWA FROM THE SOUTHWEST THIS MORNING. SHORT TERM MODEL PROGS SUGGEST
THAT LARGE SCALE ASCENT FROM AFOREMENTIONED LEAD WAVE SHOULD BEGIN TO
AFFECT THE WESTERN PORTIONS OF THE CWA BETWEEN ABOUT 12Z AND
15Z...WITH AN AREA OF RAIN AND EMBEDDED THUNDER WORKING INTO THE
CWA FROM THE WEST.

BY LATER THIS AFTERNOON AND TONIGHT...BROAD REGION OF 500 MB
HEIGHT FALLS BEGIN TO OVERSPREAD THE AREA AS VORT CENTER LIFTS
NORTHEAST ACROSS THE PLAINS AND 300MB JET BEGINS TO NOSE INTO THE
REGION. THIS SHOULD RESULT IN EXPANSION OF PRECIPITATION OVER ALL
BUT THE EXTREME SOUTHEASTERN CWA. DESPITE FAVORABLE SHEAR
PROFILES...INSTABILITY LOOKS TO BE QUITE WEAK TODAY ACROSS THE
CWA...SO NOT PARTICULARLY CONCERNED ABOUT SEVERE WEATHER THREAT
THIS AFTERNOON.

AS WE HEAD INTO TONIGHT AND ESPECIALLY ON SATURDAY...FORECAST
CONFIDENCE IS ACTUALLY A BIT LOWER THAN LAST NIGHT...DESPITE BEING
24 HOURS CLOSER. LATEST MODEL SUITE IS DEPICTING A PRONOUNCED LAG
IN THE EASTERLY PROGRESSION OF THE 500 MB TROUGH AXIS...KEEPING IT
NEUTRALLY IF NOT SLIGHTLY POSITIVITY TILTED OVER TIME...AS WELL AS
DELAYING ITS FINAL PASSAGE UNTIL LATE SUNDAY. THIS DOES LEND SOME
INCREASED UNCERTAINTY IN THE SEVERE WEATHER POTENTIAL ON SATURDAY.
CURRENT THINKING IS THAT AREA OF SHOWERS/THUNDERSTORMS THAT COME
THROUGH THE CWA TONIGHT WILL BE SLOWLY MIGRATING EAST BY SATURDAY
MORNING. STILL HAVE SOME QUESTION AS TO DEGREE OF CLEARING LATE
MORNING/EARLY AFTERNOON SATURDAY...BUT IF THAT IS ABLE TO HAPPEN TO
SOME DEGREE...GUIDANCE SUGGESTS THAT COMBINATION OF SURFACE DIABATIC
HEATING AND INCREASE IN SURFACE DEWPOINTS WILL RESULT IN RELATIVELY
NARROW AXIS OF 800-1500 J/KG OF MLCAPE FORMING ALONG AND EAST OF A
DRYLINE THAT SHOULD BE SITUATED FROM NEAR TOP TO ICT. BULK SHEAR
VALUES STILL QUITE IMPRESSIVE...WITH 40-50 KTS OF 0-6 KM BULK SHEAR
PROBABLE. LATEST GUIDANCE DOES SUGGEST THAT SHEAR VECTORS MAY BE A
LITTLE MORE PARALLEL TO SFC BOUNDARY...SUGGESTING THAT CONVECTION
MAY TAKE ON THE FORM OF CLUSTERS/BOWING SEGMENTS AS OPPOSED TO
PURELY DISCRETE SUPERCELLS. WITH THAT IN MIND...TORNADO THREAT MAY
BE A TAD LOWER THAN INITIAL THOUGHT...THOUGH 0-1 KM SRH VALUES STILL
EXPECTED TO BE MORE THE SUFFICIENT FOR A FEW TORNADOES TO FORM...
ESPECIALLY WITH ANY CELLS THAT ARE ABLE TO REMAIN DISCRETE FOR A
LONGER PERIOD OF TIME. IN ADDITION TO THE CONDITIONAL TORNADO
THREAT...STRONG AMBIENT WIND FIELDS AND LOW FREEZING HEIGHTS WILL
YIELD A WIND AND LARGE HAIL THREAT.

AS CONVECTION MOVES EAST ACROSS THE U.S. 65 CORRIDOR SATURDAY
NIGHT...EXPECT IT TO LARGELY OUTRUN INSTABILITY AXIS AND LOSE
MUCH OF ITS LUSTER. AS MENTIONED EARLIER...500 MB TROUGH LOOKS TO
HANG BACK UNTIL SUNDAY NIGHT. WITH REGION REMAINING IN AREA OF
LARGE SCALE LIFT ON SUNDAY...BELIEVE THAT CONVECTION WILL REMAIN
POSSIBLE THROUGH SUNDAY EVENING ACROSS THE CWA. SEVERE POTENTIAL
IS MOST CERTAINLY NOT NON-ZERO...BUT IS RATHER AMBIGUOUS AT THIS
POINT...OWNING TO QUESTIONS ABOUT DEGREE OF INSTABILITY THAT WILL
BE PRESENT DURING THE DAY ON SUNDAY. IF...AND ITS A BIG IF...
INSTABILITY IS ABLE TO DEVELOP...THEN SEVERE THUNDERSTORM
POTENTIAL WILL BE PRESENT ONCE AGAIN. DEGREE OF LINEAR FORCING
WITH SFC BOUNDARY SWEEPING ACROSS THE REGION WOULD SUGGEST THAT
ANY CONVECTION THAT IS ABLE TO FORM WOULD BE LINEAR IN NATURE.

BOXELL

LONG TERM (SUNDAY NIGHT THROUGH THURSDAY)...

00Z MED RANGE MODEL OUTPUT MAINTAINS AN ACTIVE WEATHER PATTERN
ACROSS THE CONUS. THE PATTERN EXPECTED IS NOT OVERLY AMPLIFIED AS
DISTURBANCES WILL RIDE THROUGH THIS FAST FLOW EVERY COUPLE OF
DAYS. THERE IS PRETTY DECENT AGREEMENT WITH THE TIMING OF
SYSTEMS...AND ONLY MODEST CHANGES IN POPS WERE MADE WITH THIS
FORECAST. GREATEST CHANGE TO THE GOING FORECAST IS A LESS
AMPLIFIED TROUGH AFFECTING THE AREA FROM MID TO LATE WEEK...
RESULTING IN A WARMER FORECAST FOR WED/THUR. OVERALL...TEMPERATURES
WILL BE AT OR ABOVE AVERAGE FOR LATE OCTOBER WITH LOWS IN THE
40S/50S AND HIGHS IN THE 60S/70S.

GAGAN

&&

AVIATION...
/ISSUED 1206 AM CDT FRI OCT 22 2010/

A SCATTERED TO MID LEVEL BROKEN DECK WILL REMAIN OVER THE AREA TONIGHT
AS MID LEVEL MOISTURE INCREASES WELL AHEAD OF A STORM SYSTEM COMING
OUT OF THE DESERT SOUTHWEST. MID TO HIGH LEVEL CLOUDINESS WILL CONTINUE
TO INCREASE FRIDAY AS THE STORM SYSTEM TRACKS INTO THE PLAINS. SOUTH
TO SOUTHEAST SURFACE WINDS WILL ALSO BE ON THE INCREASE WITH GUSTS
OVER 20 KTS BY FRIDAY AFTERNOON. A LOWER DECK ALONG WITH AN INCREASING
CHANCE FOR SHOWERS AND THUNDERSTORMS CAN BE EXPECTED FRIDAY NIGHT WITH
MVFR CONDITIONS POSSIBLE.

FOSTER

&&

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

$$

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