AFDLCH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LAKE CHARLES LA 553 AM CDT THU MAY 12 2011 .DISCUSSION... WATER VAPOR SATELLITE IMAGERY/UPPER AIR ANALYSIS SHOWED A MEAN TROF ACROSS THE CENTRAL CONUS FLANKED BY A RIDGE TO THE WEST EXTENDING FROM THE BAJA TO THE INTERMOUNTAIN WEST...AND ANOTHER TO THE EAST STRETCHING FROM THE CENTRAL GULF TO THE GREAT LAKES. WITHIN THE MEAN TROF...AN UPPER LEVEL LOW WAS NOTED SPINNING FROM EASTERN CO TWD WESTERN NE/KS. EMBEDDED WITHIN THE MEAN TROF AND TRANSLATING WITHIN THE FLOW AROUND THE UPPER LOW ARE MULTIPLE SMALLER SCALE VORT LOBES. THE LEAD IMPULSE THAT HELPED SPUR CONVECTION LAST NIGHT IS LIFTING OUT THROUGH THE ARKLATEX...WHILE UPSTREAM...ONE IS NOTED MOVING THROUGH SE TX...ANOTHER THROUGH NORTHERN MX/SOUTHERN TX...AND YET ANOTHER IS CROSSING EASTERN NM INTO THE TX PANHANDLE. AT THE SFC...LATEST ANALYSIS CONTINUED TO FEATURE HIGH PRESSURE OVER THE NE GULF...WITH AN AREA OF LOW PRESSURE OVER THE CENTRAL PLAINS THAT FEATURED A DRYLINE EXTENDING TO THE SOUTH THROUGH CENTRAL TX...AND A CDFNT TO THE SOUTHWEST THROUGH THE TX/OK PANHANDLES. TSTM COMPLEX MOVING THRU EAST TX/WRN LA THIS MORNING ON A GENERAL WEAKENING TREND PER LATEST RADAR/SATELLITE IMAGERY...THOUGH SMALL CLUSTER BTWN WOODVILLE AND JASPER IS HOLDING ITS OWN AND THERE CONTINUES TO BE SOME UPSTREAM DEVELOPMENT OVER POLK AND LIBERTY COUNTIES...PERHAPS DUE TO THE SHORTWAVE CROSSING SE TX. SOME HEFTY RAINFALL TOTALS OBSERVED...WITH THE LUFKIN ASOS NETTING AROUND 3 INCHES IN A 4 HR PERIOD. THIS MATCHES UP WELL WITH ESTIMATES FROM THE KPOE 88D...WHICH SUGGESTS THAT A SWATH OF EAST TEXAS TO THE NORTHWEST OF A TOLEDO BEND DAM TO WOODVILLE LINE RECEIVED A WELCOME AND MUCH NEEDED 1 TO 3 INCHES OF RAINFALL. DETERMINING CONVECTIVE EVOLUTION CONTINUES TO BE THE PRIMARY SHORT TERM CHALLENGE...AND IT IS NOT ONE I HAVE A GREAT DEAL OF CONFIDENCE IN GIVEN THE CONSIDERABLE INFLUENCE THAT MESOSCALE FEATURES SUCH AS THE AFOREMENTIONED SHORTWAVES AND CONVECTIVE OUTFLOW BOUNDARIES WILL HAVE. NEVERTHELESS...FROM A SYNOPTIC STANDPOINT...NO SIGNIFICANT CHANGES TO THE PROGGED PATTERN HAVE OCCURRED SINCE YESTERDAY...WHICH DOES LEND AT LEAST SOME CONFIDENCE IN OVERALL RAINFALL PROBABILITIES. ANTICIPATE THAT CURRENT CONVECTION WILL WANE LATER THIS MORNING AS THE SHORTWAVE OVER SE TEXAS LIFTS OUT OF THE AREA. RENEWED DEVELOPMENT TO THE WEST APPEARS LIKELY THIS AFTERNOON...HOWEVER...AS UPSTREAM ENERGY APPROACHES. IN ADDITION...CONVECTIVE OUTFLOWS FROM ACTIVITY THIS MORNING...EVIDENT ON OVERNIGHT RADAR IMAGERY OVER EAST TX INTO CENTRAL LA...MAY ALSO SERVE AS FOCAL POINTS. WITH THAT IN MIND...WILL CARRY SLIGHT CHANCE TO CHANCE POPS FROM SOUTHEAST TO NORTHWEST. BEYOND THIS AFTERNOON...THE UPPER LOW OVER THE PLAINS IS FORECAST TO GENERALLY TRACK TO THE EAST-SOUTHEAST OVER THE NEXT 48 HRS OR SO...REACHING SOUTHEAST MO BY MIDNIGHT FRIDAY. HEIGHT FALLS ASSOCIATED WITH THE APPROACHING TROUGH AXIS AND INCREASING UPPER DIVERGENCE OWING TO FAVORABLE JUXTAPOSITION OF THE POLAR AND SUBTROPICAL JETS IS FCST TO RESULT IN STRONG SYNOPTIC SCALE LIFT OVERSPREADING THE REGION BY LATE TONIGHT INTO FRIDAY. AMID AN UNSTABLE...CAPE AVERAGING 1500 TO 2500 J/KG...AND VERY MOIST ATMOSPHERE CHARACTERIZED BY A PWAT OF 1.5 TO 2 INCHES...150 PERCENT TO TWO STANDARD DEVIATIONS ABOVE NORMAL...EXPECT NUMEROUS SHOWERS AND THUNDERSTORMS TO DEVELOP FROM MIDNIGHT TONIGHT THROUGH FRIDAY AFTERNOON...WITH ACTIVITY BEGINNING TO WIND DOWN FRIDAY EVENING AS A FRONT MOVES THROUGH THE REGION. SPC CONTINUES TO OUTLINE THE AREA IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS...THE WESTERN HALF FOR TODAY AND TONIGHT AND THE ENTIRE AREA ON FRIDAY. BASED ON PROGGED PARAMETERS...THE TORNADO THREAT IS LOW...WITH HAIL/DAMAGING WINDS THE PRIMARY SEVERE WEATHER THREATS. GIVEN THE HIGH PWAT...LOCALLY HEAVY RAINFALL WILL ALSO BE A CONCERN WITH TSTMS . IN FACT...GIVEN THE PROGGED SYNOPTIC SETUP AND QPF PROGS THAT CONTINUE TO GRADUALLY CREEP UP...I AM BECOMING A LITTLE MORE CONCERNED ABOUT A WIDESPREAD HEAVY RAINFALL EVENT. IN DIFFERENT CIRCUMSTANCES...A FFA WOULD BE CONSIDERED...BUT NOT AT THIS TIME GIVEN THE AMBIENT DROUGHT AND HIGH FFG VALUES. IN THE WAKE OF THE FRONT LATE FRIDAY...COOLER AND DRIER AIR WILL PREVAIL THROUGH THE WEEKEND INTO EARLY NEXT WEEK. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE NORTHEAST GULF OF MEXICO UNTIL FRIDAY...WHEN A COLD FRONT IS FORECAST TO SWEEP THROUGH THE REGION. MODEST ONSHORE FLOW WILL PREVAIL AHEAD OF THE FRONT...WITH OFFSHORE FLOW PREVAILING IN ITS WAKE. SCATTERED SHOWERS AND THUNDERSTORMS AHEAD OF AND IN ASSOCIATION WITH THE FRONT...ESPECIALLY FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT. SOME OF THE THUNDERSTORMS COULD BE STRONG TO SEVERE. && .PRELIMINARY POINT TEMPS/POPS... KLCH 86 72 86 62 / 20 50 60 30 KBPT 86 73 89 61 / 30 50 60 30 KAEX 89 70 87 58 / 30 60 60 40 KLFT 89 72 86 63 / 20 50 70 40 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...NONE. TX...NONE. GM...NONE. && $$