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