FXUS63 KLSX 292344
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
544 PM CST SUN NOV 29 2009

.DISCUSSION...
/344 PM CST SUN NOV 29 2009/

PCPN DEVELOPMENT TODAY HAS BEEN VERY DISAPPOINTING...WITH LIMITING 
STREAMLINE INDICATED NOT FAR BEHIND THE CDFNT. THE CDFNT HAS NOW 
PUSHED ALMOST TO A KMTO-KFAM LINE WITH DECENTLY STRONG CAA JUST 
BEHIND IT...BUT ONLY FOR A RELATIVELY NARROW RIBBON...WHICH WILL 
HELP SHOVE TEMPS DOWN INTO THE 40S SHORTLY AFTER FROPA. EXPECT ANY 
NEW PCPN AFTER 00Z TO BE E OF THE FA AND AFFECT THE FAR SRN FA FROM 
SLUG OF PCPN IN NERN OK AND NWRN AR. KEPT TOKEN SLIGHTS IN FOR THE 
KSLO AREA.

MONDAY AND TUESDAY WILL BE MILD DAYS...ESPECIALLY TUESDAY...WITH 
DEEPENING MIXED LAYER MONDAY AFTERNOON AND REMAINING ON THE DEEP 
SIDE FOR EARLY DECEMBER THANKS TO ABUNDANT SUNSHINE AND 
UNIDIRECTIONAL FLOW. STRONGLY FAVORED THE WARMER MAV MOS TEMPS 
DURING THESE DAYS FOR MAXES AND EVEN IN SOME CASES WENT A COUPLE 
DEGS HIR. 

REGARDING THE SYSTEM TO AFFECT OUR AREA WEDNESDAY/WEDNESDAY NIGHT... 
MODELS CONTINUE TO FAVOR A BIT MORE SLY SOLN THAN WHAT WE SAW 24HRS 
AGO. AGAIN ALL OF THIS HINGES ON MODELS ABILITY TO RESOLVE THE NRN 
KICKER WHICH WILL NOT COME ONSHORE UNTIL THE 12Z RUNS ON MONDAY AT 
THE EARLIEST...AND PERHAPS NOT UNTIL THE 00Z RUNS MONDAY EVENING. 
BUT THE LATEST TRENDS ARE INDICATING THAT THE NRN KICKER WILL HAVE 
MUCH OF ITS ENERGY STAY TO THE N THUS DELAYING A FUSING OF THE NRN 
AND SRN STREAMS AND THIS WILL TEND TO DELAY AND KEEP TO THE S THE 
MAIN SRN STORM. WITH ALL OF THIS IN MIND...HAVE MAINTAINED THE 
PREVIOUS FORECAST WITH RESPECT TO PCPN PROBS AND KEEPING THE MAIN 
NRN EXTENT JUST S AND E OF THE STL METRO AREA ALTHOUGH THE NAM IS 
HINTING AT A FINGER OF PCPN EXTENDING FURTHER NW THRU THE STL METRO 
AREA...THIS IS A RESULT OF THE VERY TRICKY PHASING OF THE TWO 
STREAMS AND SO CONFIDENCE ON THIS FEATURE NOT VERY HIGH ATTM. PCPN 
FORECAST IS BASED SANS THIS PCPN FINGER SINCE THIS IS MORE OF A 
MESOSCALE FEATURE AND SKILL IS LOW AT THIS POINT IN TIME. ONE OTHER 
TREND OF NOTE BETWEEN THE 12Z RUNS TODAY AND WHAT WE SAW FROM THE 
00Z LAST NIGHT AND 12Z YESTERDAY IS THAT THE DELAY OF THE SRN STORM 
BY JUST A TAD WILL ALLOW THE LO LEVEL COLD AIR TO SEEP A BIT MORE 
SEWD AND WILL RESULT IN HIR PROBS FOR FROZEN PCPN OUT OF WHAT PCPN 
WE WILL SEE. SO IN SUMMARY...MAINTAINED THE MORE SLY NRN EDGE OF THE 
DEF ZONE PCPN FOR LATE WEDNESDAY AFTN/WED NIGHT BUT THE END RESULT 
APPEARS TO BE A QUICKER CHANGEOVER TO SNOW IN WHAT WE DO GET. 

FOR THE EXTENDED PERIOD (THURSDAY - SUNDAY)...IN THE WAKE OF THE 
STORM SYSTEM THE MODELS ARE IN REASONABLY GOOD AGREEMENT THAT A DEEP 
MID LEVEL TROF WILL BUILD INTO THE UPR MIDWEST AND GRTLKS REGIONS 
AND REMAIN THRU THE END OF THE WORKWEEK. THIS WILL KEEP THINGS COLD 
WITH PERSISTENT CLOUDS AND A FEW FLURRIES INTO THURSDAY WITH THE 
CLOUDS/PCPN CHCS LOOKING MORE DOUBTFUL HEADING INTO FRIDAY. NEXT 
WEEKEND STILL LOOKS COMPLETELY UP IN THE AIR AS THE MODEL SPREAD 
REMAINS VERY LARGE...PRIMARILY OVER THEIR HANDLING OF A STRONG NRN 
STREAM WAVE INTO WRN CANADA. WILL FALL BACK TO THE GFS ENSEMBLE MEAN 
SOLUTION WHICH TEMPERS THIS FEATURE BETWEEN THE SPECTRUM OF 
POSSIBILITIES AND YIELDS INSTEAD A MORE NEUTRAL ZONAL FLOW PATTERN 
OVER THE CNTRL CONUS WITH TEMPS SLOWLY MOVING BACK TOWARDS CLIMO 
VALUES. SATURDAY/S PCPN EVENT STILL LOOKS IFFY EVEN WITH THE MORE 
AGGRESSIVE OPERATIONAL GFS OUTPUT AND HAVE MAINTAINED A DRY FCST FOR 
NOW.

TES

&&

.AVIATION...
/540 PM CST SUN NOV 29 2009/

FOR THE 00Z TAFS...FEW CHGS MADE TO PREV SET OF TAFS SINCE TRENDS
APPEAR ON TRACK. CDFNT AND ASSOCIATED LGT PRECIP HAVE ALREADY
PUSHED S OF THE TAF SITES...LEAVING TIMING OF MVFR CIGS AS THE
PRIMARY CONCERN. THIS TASK IS COMPLICATED BY HIGHER CLDS STREAMING
NEWD ACROSS MO/IL WHICH HAVE OBSCURED THE LOWER DECK IN RECENT IR
SATELLITE IMAGES. BASED ON SFC OBS AND EARLIER SATELLITE
IMAGERY...MVFR DECK ACROSS NRN MO/SRN IA EXPECTED TO REACH STL/SUS
BY 02Z AS IT SINKS SWD TONIGHT. AS HIGH PRES CONTINUES BUILDING IN
TO THE REGION...SKIES WILL CLR AND WINDS WILL BACK WLY TO WSWLY ON
MON MORNING.

KANOFSKY

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&

$$

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