FXUS63 KLSX 080040
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
640 PM CST MON DEC 7 2009
.DISCUSSION...
/219 PM CST MON DEC 7 2009/
MAIN CONCERN CONTINUES TO BE WITH THE SIGNIFICANT WINTER STORM THAT
WILL AFFECT THE AREA TOMORROW INTO WEDNESDAY. GLOBAL MODELS ARE
SHOWING GOOD AGREEMENT WITH THE STORM...SHOWING AN ALMOST IDENTICAL
PATH OF THE 850MB LOW FROM SRN KS THRU CNTRL MO INTO NERN IL ON
TUESDAY NIGHT. THIS KEEPS THE SRN EDGE OF THE HEAVIEST SNOW BAND
ACROSS THE NRN CWA. HAVE ENOUGH CONFIDENCE TO UPGRADE TO A WINTER
STORM WARNING FROM THE FAR NRN PART OF THE CWA...WITH A ONE COUNTY
WIDE ADVISORY JUST TO THE SOUTH.
AFTER A DRY EVENING...PRECIPITATION CHANCES WILL INCREASE OVER THE
NWRN PART OF THE CWA OVERNIGHT AS LARGE SCALE ASCENT INCREASES AHEAD
OF THE SHORTWAVE TROUGH. CHANCES WILL ALSO INCREASE OVER THE FAR
SRN PART OF THE CWA AS LOW LEVEL MOISTURE CONVERGENCE RAMPS UP
AHEAD OF A BROAD 35KT LOW LEVEL JET. HAVE LIKELY OR CATEGORICAL
POPS ACROSS THE CWA AS AFOREMENTIONED FORCING SPREADS ACROSS THE
AREA AND CONTINUE THESE HIGH POPS THROUGH WEDNESDAY AS CLOSED LOW
RACES ACROSS THE AREA. BEST CHANCE TOMORROW NIGHT WILL BE OVER THE
NRN CWA WHERE MID LEVEL FRONTOGENESIS IN THE DEFORMATION ZONE WILL
BE THE STRONGEST...WITH LESSER CHANCES IN THE DRY SLOT TO THE
SOUTH OF THE LOW. SUBSIDENCE SETS IN VERY QUICKLY ON WEDNESDAY IN
THE WAKE OF THE LOW...THOUGH KEPT SCT -SHSN/FLURRIES GOING IN THE
LOW LEVEL CYCLONIC FLOW.
PRECIPIATION TYPE IS STILL IN QUESTION AS LOW LEVEL JET BRINGS QUITE
A BIT OF WARM AIR INTO THE SYSTEM. MADE NO BIG CHANGES TO GOING
WEATHER TYPE...GOING WITH MAINLY SNOW IN THE FAR NW WHERE AMOUNTS
SHOULD CLIMB INTO THE 4-8 INCH RANGE WITH A RAPID TAPERING TO THE
SOUTHEAST OF THERE WHERE SLEET...RAIN OR EVEN SOME FREEZING RAIN
WILL TAKE AWAY FROM THE SNOW TOTALS. HAVE ONE INCH SNOW
ACCUMULATION NORTH OF A COU-PPQ LINE. THIS AGREES WELL WITH THE
MAJORITY OF ANALOGS ON THE SLU/CIPS WEBSITE.
KEPT THE SAME IDEA OF WINDY CONDITIONS SETTING IN LATE TUESDAY NIGHT
AND WEDNESDAY NIGHT AS SFC LOW CONTINUES TO DEEPING. KEPT BLOWING
SNOW OVER WARNING AREA...AND MAY NEED TO CONSIDER A WIND ADVISORY
OUTSIDE OF GOING HEADLINES. WEDNESDAY LOOKS LIKE A RAW DAY AS WIND
CHILLS RAPIDLY FALL.
NOT MUCH CONFIDENCE WITH THE FORECAST LATE THIS WEEK INTO EARLY NEXT
WEEK AS MOST OF THE MODELS ARE NOT CONSISTENT WITH TIMING SHORTWAVE
TROUGHS THROUGH QUASI-ZONAL FLOW. HAVE KEPT JUST SLIGHT CHANCES FOR
RAIN/SNOW GOING FRIDAY INTO SATURDAY AND AGAIN SUNDAY NIGHT AND
MONDAY AS THERE IS NOT ENOUGH AGREEMENT TO INTRODUCE MENTIONABLE
PRECIPITATION IN THE EXTENDED AT THIS POINT. TEMPERATURES ARE A
BLEND OF GOING TEMPS...HPC GUIDANCE AND THE GEFS MEAN MOS.
BRITT
&&
.AVIATION...
/612 PM CST MON DEC 7 2009/
FOR THE 00Z TAFS...LOW LEVEL CLOUD COVER OF 1000-1500 FT IN UIN
AND 1500-2000 FT IN COU SHOULD CONTINUE TGT...WHILE THE 2500 FT
CEILING IN STL/SUS MAY GO SCT AT TIMES TGT. AS LOW-MID LEVEL WAA
INCREASES ACROSS THE CWA THROUGH THE NGT LGT SNOW SHOULD MOVE INTO
UIN AROUND 12Z TUE OR SHORTLY AFTER...WITH A MIX OF MAINLY LGT
SNOW AND SLEET IN COU AROUND 14Z TUE AND IN STL/SUS BY 15Z TUE. AS
THE LOW LEVELS CONTINUE TO WARMUP THROUGH THE DAY THE
PRECIPITATION TYPE WILL LIKELY CHANGE TO RAIN IN STL/SUS BY 18Z
TUE AND TO RAIN OR A MIX OF RAIN...SLEET AND SNOW IN COU. AT UIN
THE SNOW WILL CHANGE TO SNOW AND SLEET BY 18Z TUE. THE CLOUD
CEILING WILL LOWER TO AROUND 800FT BY 14-15Z TUE AS THE BNDRY
LAYER SATURATES. LGT SFC WNDS WILL STRENGTHEN LATE TGT AND THROUGH
THE DAY ON TUE BACKING AROUND TO A NELY DIRECTION TGT AND AN ELY
DIRECTION ON TUE.
GKS
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WARNING FROM 6 AM TUESDAY TO NOON CST WEDNESDAY FOR
KNOX-LEWIS-MARION-SHELBY.
WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO NOON CST WEDNESDAY
FOR MONROE-RALLS.
IL...WINTER STORM WARNING FROM 6 AM TUESDAY TO NOON CST WEDNESDAY FOR
ADAMS IL.
WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO NOON CST WEDNESDAY
FOR BROWN IL-PIKE IL.
&&
$$
WFO LSX
