FXUS63 KLSX 221334
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
734 AM CST TUE DEC 22 2009

.UPDATE...
/732 AM CST TUE DEC 22 2009/
UPDATED FORECAST TO PUT SOME FOG INTO THE GRIDS FOR THE NEXT FEW
HOURS. LOOKING AT THE LIFR STRATUS CONTINUE TO EXPAND NORTH...AM
HAVING MY DOUBTS THAT WE WILL BE ABLE TO GET OUT OF THE 30S EAST
OF THE MISSISSIPPI RIVER TODAY. WILL DEFER THAT DECISION TO
DAYSHIFT.

CVKING

&&

.DISCUSSION...
/514 AM CST TUE DEC 22 2009/

PRIMARY CONCERN THIS FCST PD IS LARGE STORM SYSTEM EXPECTED TO 
IMPACT THE CENTRAL US THROUGH FRIDAY.

EAGERLY ANTICIPATED 22/00Z WEST COAST RAOB SAMPLING OF DVLPG STORM 
SYSTEM HAS RESULTED IN FEW CHANGES TO THINKING ON LARGE SCALE PATTN 
EVOLUTION...ALTHOUGH CONCERNS REMAIN THAT FCST TIMING MAY BE TOO 
QUICK GIVEN BLOCKED PATTN ACROSS FAR ERN CANADA. WATER VAPOR IMAGERY 
SHOWS AN ELONGATED SHEAR ZONE AND HIGHLY MERIDIONAL FLOW ALONG THE 
WEST COAST WITH SEVERAL EMBEDDED VORTICITY MAXIMA. SRN SHORTWAVE IN 
THIS TRAIN WAS DIGGING SWD INTO SOCAL AT 10Z...AND IT IS THIS FEATURE 
THAT WILL BE RESPONSIBLE FOR A VARIETY OF WEATHER ACROSS THE CENTRAL 
US AS IT EVOLVES OVER THE NEXT FEW DAYS. AS THE SYSTEM CROSSES THE 
ROCKIES...SFC LOW WILL DVLP OVER NM/TX AND MOVE NEWD. 

EXPECTING RAIN SHOWERS TO DEVELOP TONIGHT WITH WAA ALOFT AND DVLPG 
SFC BDRY STRETCHED ACROSS THE AREA BUT HEAVIEST RAINFALL WILL HOLD 
OFF UNTIL TOMORROW AND THU. THERE WILL BE PLENTY OF MOISTURE TO WORK 
WITH AS GULF AIR IS TRANSPORTED NWD WITH SREF/NAM/LOCAL WRF 
SHOWING STEADILY INCRSG PW VALUES THROUGH THU. WIDESPREAD PW VALUES 
OF TWO STANDARD DEVIATIONS ABOVE THE MEAN CLIMATOLOGICAL VALUE FOR 
MO IN DECEMBER POINT TO POTENTIAL FOR HEAVY RAINFALL...ESPECIALLY ON 
WED NIGHT INTO THU WHEN MODELS DEPICT A ROBUST 50+ KT LLJ. HAVE 
ISSUED AN ESF FOR FLOODING CONCERNS AS RAIN WILL FALL ON FROZEN 
GROUND BUT LATER SHIFTS MAY NEED TO CONSIDER A FLOOD WATCH. 

THERE IS SOME CONCERN FOR DRY SLOTTING ON THU NIGHT INTO FRI. ANY 
REMAINING PRECIP WILL CHANGE TO SNOW BEHIND THE CDFNT AS THE SYSTEM 
PULLS AWAY ON THU NIGHT AND FRI. BEHIND THE SYSTEM...TIGHT PRES 
GRADIENT WILL CAUSE STG GUSTY WINDS ON FRI. NO CHANGES PAST 00Z
SAT.

KANOFSKY

&&

.AVIATION...
/521 AM CST TUE DEC 22 2009/

FOR THE 12Z TAFS...
TRICKY CLOUD FORECAST THIS MORNING WITH LIFR CEILINGS LURKING TO
THE SOUTHEAST OF KSTL AND KSUS. HAVE INCLUDED A TEMPO FOR THESE
CEILINGS BUT AM NOT CONFIDENT TO GO PREVAILING YET. WILL JUST HAVE
TO WATCH AND SEE OVER THE NEXT HOUR OR SO. THEN FOCUS TURNS NORTH
AS LOW CEILINGS ARE BUILDING SOUTH TOWARD KUIN. OTHERWISE...A
GENERAL LOWERING AND THICKENING TREND SHOULD COMMENCE THIS
AFTERNOON WITH WARM ADVECTION AHEAD OF WELL ADVERTISED STORM
SYSTEM. WIND WILL REMAIN EAST-SOUTHEAST.

CVKING

&&

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

$$

WFO LSX