135 
FXUS63 KLSX 180723
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
223 AM CDT FRI MAY 18 2012

.SHORT TERM...
ISSUED AT 222 AM CDT FRI MAY 18 2012
(TODAY AND TONIGHT)

BEAUTIFUL STRETCH OF WEATHER CONTINUES ACROSS THE LOWER MISSOURI AND 
MID MISSISSIPPI RIVER VALLEYS. TODAY WILL MARK THE TENTH DAY 
WITHOUT PRECIPITATION. THIS IS IMPRESSIVE SINCE A PURE STATISTICAL 
AVERAGE OF CLIMATE DATA OFFERS ALMOST A 40 PERCENT CHANCE OF 
PRECIPITATION FOR ANY 24 HOUR PERIOD THIS TIME OF YEAR.

TODAY AND TONIGHT...
UPPER LEVEL RIDGE PARKED OVER MISSOURI AND ILLINOIS WILL ACT TO 
DIVERT THE STOUT MID/UPPER LEVEL DISTURBANCE OVER WESTERN KANSAS TO 
THE NORTH OF THE CWA TODAY. OTHER THAN SOME CIRRUS IT APPEARS THAT 
THERE WILL BE PLENTY OF SUNSHINE AND WINDS WILL BECOME MORE 
SOUTHERLY AS THE SURFACE RIDGE SLOWLY BEGINS TO LOOSEN ITS GRIP ON 
THE REGION. MOS GUIDANCE NEARLY IDENTICAL WITH MID TO UPPER 80S FOR 
HIGH TEMPERATURES THIS AFTERNOON AND LOWER TO MIDDLE 60S TONIGHT FOR 
LOWS. THIS RETREATING SURFACE HIGH PATTERN ROUTINELY FAVORS SLIGHTLY 
COOLER TEMPERATURES IN THE EASTERN OZARKS WHERE DECOUPLING OCCURS IN 
THE SHELTERED VALLEYS. HAVE THEREFORE KNOCKED A FEW DEGREES OFF THE 
MOS GUIDANCE...WITH UPPER 50S FORECAST.

CVKING

&&

.LONG TERM...
ISSUED AT 222 AM CDT FRI MAY 18 2012
(SATURDAY THROUGH THURSDAY)

THIS WEEKEND... 
UPPER LEVEL RIDGE WILL SLOWLY MOVE EAST...ALLOWING SOUTHWEST FLOW
ALOFT TO DEVELOP FROM THE PLAINS INTO OUR REGION ON SATURDAY.
TEMPERATURES EXPECTED TO REMAIN WARM AS 850MB TEMPS RISE ABOVE
+15C WITH A PERSISTENT SOUTHERLY SURFACE WIND. A STRONG SHORTWAVE
WILL FLATTEN THE UPPER FLOW ACROSS THE MIDDLE OF THE COUNTRY ON
SUNDAY...SENDING A COLD FRONT ACROSS THE CWA. HIGH TEMPERATURES ON
SUNDAY WILL HINGE ON THE SPEED OF THE FRONT. IT APPEARS THAT AT
THIS POINT THAT THERE WILL BE ENOUGH TIME ON SUNDAY FOR
TEMPERATURES TO RISE INTO THE MIDDLE AND UPPER 80S ACROSS EAST
CENTRAL/SOUTHEAST MISSOURI AND CENTRAL/SOUTHWEST ILLINOIS AHEAD OF
THE FRONT. SUFFICIENT INSTABILITY AHEAD OF THE FRONT AND SHORTWAVE
WILL AID IN SCATTERED SHOWERS AND THUNDERSTORMS DEVELOPING ACROSS
THE CWA DURING THE AFTERNOON HOURS. LACK OF SHEAR APPEARS TO LIMIT
THREAT OF A WIDESPREAD SEVERE THUNDERSTORM OUTBREAK.

NEXT WEEK...
FRONT CLEARS THE CWA BY 12Z MONDAY WITH PRECIPITATION THREAT ENDING 
ON MONDAY AS 1020MB HIGH PRESSURE CENTER BUILDS INTO THE MIDWEST. 
TEMPERATURES RETURN TO NORMAL OR MAYBE SLIGHTLY BELOW NORMAL EARLY 
NEXT WEEK...BEFORE MODERATING BACK ABOVE NORMAL BY MIDWEEK.

PRECIPITATION CHANCES NEXT WEEK WILL DEPEND ON THE STRENGTH AND 
ORIENTATION/LOCATION OF THE UPPER LEVEL RIDGE THAT IS FORECAST BY 
MEDIUM RANGE MODEL GUIDANCE TO BUILD OVER THE CENTER/EASTERN UNITED 
STATES BY WEEKS END. THE 00Z GFS AND ECWMF INITIALLY HAVE SOUTHWEST 
FLOW OVER MISSOURI THURSDAY AND FRIDAY...WHICH FAVORS LOW CHANCE 
POPS ACROSS NORTHEAST MISSOURI AND WEST CENTRAL ILLINOIS.

MEMORIAL DAY WEEKEND...
LATEST MODEL GUIDANCE SUGGESTS A VERY WARM AND DRY HOLIDAY WEEKEND 
AS A MASSIVE SUMMER-LIKE UPPER LEVEL RIDGE SETS UP SHOP ACROSS THE 
EASTERN HALF OF THE CONUS. TEMPERATURES IN THE 90S LOOK LIKE A GOOD 
BET FOR THE UNOFFICIAL FIRST WEEKEND OF SUMMER.

CVKING

&&

.AVIATION...
ISSUED AT 1035 PM CDT THU MAY 17 2012

RELATIVELY WEAK SELY SFC WINDS WILL CONTINUE LATE TGT WITH THE
SFC RIDGE EXTENDING FROM ERN MI AND WRN NY SW THROUGH ERN MO.
S-SELY SFC WINDS CAN BE EXPECTED ON FRI INCREASING TO 9-10 KTS AS
THE SFC RIDGE MOVES SLOWLY EWD. JUST SOME CIRRUS CLOUDS THIS
PERIOD AS WEAKENING SHORTWAVE NOW OVER WRN KS MOVES NEWD AND
APPROACHES NWRN MO LATE TGT AND FRI MRNG. MAY ALSO HAVE FEW
DIURNAL CUMULUS CLOUDS FRI AFTN IN COU AND THE STL METRO AREA AS
LOW LEVEL MOISTURE GRADUALLY INCREASES FROM THE S.

SPECIFICS FOR KSTL...LIGHT SELY SFC WIND LATE TGT WILL INCREASE
TO AROUND 9 KTS FRI AFTN. JUST SOME CIRRUS CLOUDS THIS PERIOD WITH
FEW DIURNAL CUMULUS CLOUDS POSSIBLE FRI AFTN.

GKS

&&

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

$$

WFO LSX