319 FXUS61 KRLX 111804 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 204 PM EDT FRI JUN 11 2010 .SYNOPSIS... AN UPPER LEVEL DISTURBANCE DRIFTS ACROSS THE FORECAST AREA SATURDAY...LEADING TO SCATTERED THUNDERSTORMS AND LOCAL DOWNPOURS && .NEAR TERM /THROUGH SATURDAY/... S/W TRACKING ACROSS NRN PORTIONS OF THE FORECAST AREA HAS KICKED OFF SOME CONVECTIVE SHOWERS. THESE ARE DISSIPATING AS THE REACH INTO SE OH ZONES. ELSEWHERE...ACROSS WESTERN WV AND EASTERN KY...NOTED SOME CONVECTIVE ACTIVITY DEVELOPING INVOF OF WARM FRONT THAT LIES ALONG SUBTROPICAL RIDGE. HIGH PW VALUES LIE JUST TO OUR SW AND ARE PROGGED TO CREEP INTO FORECAST AREA OVERNIGHT AS WEAK CLOSE LOW LIFTS NE OUT OF THE OZARK PLATEAU. THIS FEATURE WILL SERVE AS THE FOCUS FOR CONVECTIVE DEVELOPMENT FOR THE NEXT 24 HOURS ACROSS THE FORECAST AREA. BOTH NMM AND GFS MODELS SHOW DIFFERENCES IN HANDLING THE PROGRESSION S/W WORKING NORTHEAST ACROSS SUB-TROPICAL RIDGE...BUT THE GFS HAS SHOWN A LITTLE MORE RUN TO RUN CONSISTANCY. FOR TIMING PRECIP ONSET USED A BLEND...BUT LEANED CLOSER TO TIMING OFFERED BY THE GFS. FOR TEMPS...WITH CLOUDS IN PLACE...KEEP MOST AREAS ABOVE GUIDANCE VALUES FOR OVERNIGHT MINS. WENT SLIGHTLY BELOW GUIDANCE FOR MAX TEMPS SATURDAY DUE TO CLOUD COVER AND PRECIP. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... ALL MODELS INDICATING UPPER LOW COMING OUT OF LOWER MISSISSIPPI VALLEY...GETTING CAUGHT UP IN THE WESTERLIES AND TRACKING ACROSS THE FCST AREA SAT AFTN AND EVNG. ALL OF THE MODELS ALSO INDICATING INTENSE RAINFALL ALTHOUGH ITS HISTORY OF PRODUCING FLOODING SHOULD NOT BE DUPLICATED HERE ON ACCOUNT OF ITS FASTER MOVEMENT. VERY WARM AND MOIST AIR AHEAD OF THIS SYSTEM...ALONG WITH IDEAL DIURNAL TIMING SHOULD LEAD TO RATHER STRONG THUNDERSTORMS...A FEW GOING SEVERE NOT OUT OF THE QUESTION. CLOUD SHIELD OUT AHEAD OF COMPLEX IN THE MORNING MAY LIMIT HEATING INDUCED INSTABILITY AND INDEED MODELS DO NOT O OVERBOARD WITH THIS. FLOW AND SHEAR DO LOOK FAVORABLE INCLUDING SOME TURNING WITH HEIGHT. WHAT IS RIDICULOUS IS THE FCST PWATS WHICH PEAK AOA 2.25 IN. WHILE THE SYSTEM WILL BE MOVING...DOWNPOURS MAY BE HEAVY ENOUGH FOR FLASH FLOODING ON THE SCALE OF AN HOUR OR TWO. THE SEVERE THREAT WILL LIKELY PRECEDE THE WATER THREAT...WITH THE HARD RAIN OCCURRING IN THE STABLE COOL POOL. WILL CONTINUE HIGHLIGHTING SEVERE AND WATER THREATS IN HWO. SYSTEM IS GONE SUNDAY...BUT CONTINUED VERY WARM AND HUMID S TO SW LOW LEVEL FLOW AND WNW FLOW WITH EMBEDDED RIPPLES ALOFT SHOULD LEAD TO CONVECTION AGAIN SUN AFTN. GIVEN DECENT FLOW AND BUOYANCY...THERE WILL LIKELY BE SOME SEVERE THREAT ONCE AGAIN SUN AFTN. QUESTION FOR SUN NT AND MON IS WHETHER A COLD FRONT MOVES S THROUGH THE AREA SUN NT...WITH DRIER CONDITIONS FOR MON...AS ALLEGED BY THE NAM12. OTHER MODELS KEEP FRONT HUNG UP TO THE N. BELIEVE FRONT SHOULD MAKE SOME PROGRESS INTO THE AREA AND THEN EVENTUALLY BECOME HUNG UP. EDGED HIGHS BACK A BUT FOR SAT WITH SYSTEM MOVING THROUGH AND LEANED HIGHS UP A BIT SUN WITH A BIT MORE SUNSHINE...AND ON MON WITH SLIGHTLY LESS AGGRESSIVE COLD FRONT. ALSO EDGED LOWS UP A BIT IN MOST CASES ALONG WITH SOME OF THE DEW POINTS. && .LONG TERM /TUESDAY THROUGH THURSDAY/... AGREED WITH HPC THAT THERE IS A LARGE AMOUNT OF SPREAD BETWEEN THE MODELS...THEREFORE FOLLOWED HPCS REASONING AND FOLLOWED THE ECMWF DUE TO THE CONSISTENCY IN ITS MODEL SOLUTIONS. HOWEVER...KEPT POPS AT OR BELOW THE CHANCE RANGE TO REFLECT THE UNCERTAINTY BETWEEN THE MODELS. RAIN WILL CONTINUE THROUGH MONDAY EVENING AS THE COLD FRONT SLOWLY DRIFTS SOUTHWARD AND STALLS OUT SOUTH OF TENNESSEE...SOME OF THESE SHOWERS COULD PRODUCE HEAVY DOWNPOURS ESPECIALLY SINCE PW VALUES WILL REMAIN NEAR 2 INCHES. THE AREA WILL BE DRY THROUGH LATE TUESDAY AFTERNOON AS AN UPPER LEVEL RIDGE TAKES HOLD OVER THE SOUTHEAST US. THE NEXT CHANCE OF RAIN ARRIVES LATE TUESDAY AFTERNOON AS MOISTURE ASSOCIATED WITH A WEAKENING LOW PRESSURE SYSTEM MIGRATES AROUND THE UPPER LEVEL RIDGE AND INTO THE TRI-STATE AREA. EXPECTING A SOMEWHAT DIURNAL PATTERN AS FAR AS THUNDERSTORMS ARE CONCERNED...BUT AT THIS TIME THE PROBABILITIES OF RAIN AND STORMS ARE CHANCE TO SLIGHT CHANCE THROUGHOUT THE REMAINDER OF THE EXTENDED FORECAST. TEMPERATURES THROUGHOUT THE EXTENDED WILL BE RELATIVE STEADY WITH HIGHS IN THE LOW TO MID 80S AND LOWS AROUND 60...WITH LOWER TEMPERATURES EXPECTED IN THE HIGHER TERRAIN. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... GENERAL VFR CONDITIONS FOR MOST AREAS THIS AFTERNOON...EXCEPTION BEING ALONG THE OH RVR VALLEY WHERE SOME CONVECTIVE ACTIVITY DEVELOPING. ACTIVITY SHOULD SUBSIDE AFTER SUNSET WITH VALLEY FOG EXPECTED BY MORNING. REMNANTS OF AR CONVECTIVE COMPLEX PROGGED TO MOVE ACROSS SE OH AND NRN WV TO START THE DAY SAT. THIS FEATURE WILL PRODUCE AREAS OF MVFR AND LOCL IFR CONDITIONS SPREADING WEST TO EAST. AFTER 18Z SATURDAY... IFR POSSIBLE IN THUNDERSTORMS INTO SATURDAY NIGHT...FOLLOWED BY LOW CLOUDS AND FOG INTO EARLY SUNDAY MORNING ESPECIALLY FOR AREAS THAT RECEIVE RAIN. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$