086 
FXUS63 KLSX 050016
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
616 PM CST MON FEB 4 2013

.SHORT TERM...
ISSUED AT 303 PM CST MON FEB 4 2013
(TONIGHT)

COLD FRONT STILL OVER FORECAST AREA AS OF 20Z...MAINLY ALONG AND 
SOUTH OF PARIS ILLINOIS TO SPRINGFIELD MO LINE. SO COLDER AIR AND SC 
DECK IS SLOW TO MOVE INTO NORTHERN PORTIONS OF FORECAST AREA. THUS 
TEMPS HAVE WARMED UP A BIT MORE THAN ORIGINALLY FORECAST...SO 
ADJUSTED HOURLY TEMPS FOR THE EVENING HOURS.

OTHERWISE...SURFACE RIDGE TO BUILD IN OVERNIGHT WITH TEMPS DROPPING 
INTO THE 20S. CURRENT SATELLITE PICS SHOW THAT SC DECK THAT IS 
MOVING INTO NORTHERN PORTIONS OF FORECAST AREA IS A BIT DIURNALLY 
DRIVEN...WITH IT THINNING OUT A BIT QUICKER...BUT HIGH CLOUDS 
CONTINUE TO STREAM SOUTHEAST TOWARDS FORECAST AREA...SO WILL LEAVE 
SKIES PARTLY TO MOSTLY CLOUDY OVERNIGHT. RAIN THAT HAD DEVELOPED 
OVER SOUTHERN MO/SOUTHERN IL EARLIER TODAY HAS MOVED AWAY FROM 
FORECAST AREA...SO SHOULD SEE DRY CONDITIONS TONIGHT.

BYRD

&&

.LONG TERM...
ISSUED AT 303 PM CST MON FEB 4 2013

(TUESDAY-THURSDAY)

NO MAJOR CHANGES TO GOING FORECAST AS 12Z GUIDANCE IS MAINTAINING 
GOOD RUN TO RUN AND MODEL TO MODEL CONSISTENCY WITH UPCOMING 
SYNOPTIC TRENDS OVER THE CENTRAL CONUS...AND TRANSITION OF UA 
PATTERN TO ZONAL FLOW LOOK BY MIDWEEK.

THERE ARE TWO SHORTWAVES THAT ARE PROGGED INTO THE REGION DURING THE 
SHORT TERM.  THE FIRST WILL BE PASSING TO OUR N TOMORROW...AND WHILE 
IT MAY BRING A FEW CLOUDS TO N SECTIONS OF THE CWA PRECIP THREAT 
WITH THIS FEATURE SHOULD REMAIN WELL TO OUR N.  HOWEVER...THE 
DYNAMICS ASSOCIATED WITH THE NEXT SHORTWAVE SHOULD PASS DIRECTLY 
OVER OUR AREA LATE WEDNESDAY NIGHT AND THURSDAY BRINGING THE ENTIRE 
AREA A THREAT OF SHOWERS.  MODELS HAVE DEVIATED VERY LITTLE WITH THE 
SPEED OR INTENSITY OF THIS SYSTEM...SO WITH THE PROGGED MOISTURE 
RETURN HIGH CHANCE/LOW LIKELY POPS STILL SEEM REASONABLE. NAM
LOOKS A BIT FAST WITH THE EWD PROGRESSION OF THE PRECIP ACROSS
THE AREA...AND HAVE FOLLOWED THE SOMEWHAT SLOWER TREND WHICH IS
MORE IN LINE WITH MODEL CONSENSUS AND ENSEMBLE MEANS.

AS CAN BE SEEN BY THE TEMPERATURE TRENDS OF THE PAST FEW DAYS AND 
NIGHTS...AND ESPECIALLY TODAY...THE PASSAGE OF EACH SHORTWAVE HAS 
BROUGHT ABOUT FAIRLY DRAMATIC AMS CHANGES TO THE REGION.  AND WHILE 
THE NEXT TWO SHORTWAVES WILL ALSO BRING SOME SWINGS IN TEMPS...THE 
TRANSITION TO A MORE ZONAL FLOW PATERRN WILL MEAN THAT THE 
PENETRATION OF THE COLD AIR BEHIND EACH SHORTWAVE WILL BE MUCH LESS 
DRAMATIC....AND OVERALL TEMPERATURES WILL BE TRENDING ABOVE AVERAGE.

(FRIDAY-MONDAY)
MAIN CONCERN IN THE MEDIUM RANGE CONTINUES TO BE LARGE STORM SYSTEM 
THAT IS PROGGED TO WORK FROM THE WESTERN U.S. INTO THE NATIONS 
MIDSECTION DURING THE WEEKEND.  MODELS CONTINUE TO TREND A BIT 
SLOWER WITH EWD PROGRESSION OF THIS SYSTEM SO WILL KEEP SATURDAY 
DRY...AND ALLOW SHOWERS AND THUNDERSTORM TO OVERSPREAD THE REGION 
SATURDAY NIGHT AND SUNDAY.   

AMS AHEAD OF THIS SYSTEM WILL BE MODERATING NICELY...AND HAVEN'T 
GONE WARMER DURING THE WEEKEND DUE TO INCREASING CLOUDS ON 
SATURDAY...AND RAIN THREAT ON SUNDAY. 

TRUETT

&&

.AVIATION...
ISSUED AT 546 PM CST MON FEB 4 2013

COLD FRONT HAS MOVED SE OF THE TAF SITES EARLY THIS EVNG WITH
N-NWLY SFC WINDS AS THE SFC RIDGE EXTENDING FROM NERN KS NE
THROUGH WI BUILDS SEWD INTO OUR AREA. THE SFC WIND WILL BECOME
LIGHT LATER THIS EVNG AND INTO THE OVERNIGHT HOURS AS THE SFC
RIDGE AXIS SHIFTS SWD THROUGH OUR AREA. THE SFC WIND WILL BECOME
S-SWLY BY EARLY TUE MRNG AS THE SFC RIDGE WEAKENS AND SHIFTS S-SE
OF OUR AREA AND A COLD FRONT APPROACHES. THE SFC WIND WILL VEER
AROUND TO A NWLY DIRECTION TUE AFTN AFTER FROPA. A BAND OF MVFR
CLOUDS AROUND 1500-2000 FT IN HEIGHT OVER NERN MO W CNTRL IL WILL
ADVECT SEWD INTO THE ST LOUIS METRO AREA LATER THIS EVNG. MORE
PATCHY MVFR CLOUDS ACROSS NWRN MO MAY ALSO IMPACT COU AS WELL.
THESE MVFR CLOUDS SHOULD ADVECT SE OF UIN AND COU LATE TGT AND SE
OF THE ST LOUIS METRO AREA EARLY TUE MRNG LEAVING JUST SOME
MID-HIGH LEVEL CLOUDS OVER THE AREA.

SPECIFICS FOR KSTL...BAND OF MVFR CIGS...AT 1500-2000 FT SHOULD
ADVECT SEWD INTO STL AROUND 0130-0200Z TUE. WITH A NOCTURNAL INVERSION
THESE CLOUDS MAY NOT SCATTER OUT TIL EARLY TUE MRNG. OTHERWISE
JUST MID-HIGH LEVEL CLOUDS FOR LATE TGT AND TUE. N-NWLY SFC WIND
WILL WEAKEN THIS EVNG AS THE SFC RIDGE MOVES SEWD THROUGH OUR
AREA...THEN BECOMES SWLY TUE MRNG AND STRENGTHENS AS THE SFC
RIDGE SHIFTS SE OF STL AND A COLD FRONT APPROACHES. THE SFC WIND
WILL VEER AROUND TO A NWLY DIRECTION BY LATE TUE AFTN AFTER FROPA...
THEN DIMINISHES TUE EVNG.

GKS

&&

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

$$

WFO LSX