Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000 FXUS64 KHGX 011813 AFDHGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 113 PM CDT MON SEP 1 2014 .DISCUSSION... 18Z AVIATION DISCUSSION. && .AVIATION... AFTERNOON CONVECTION BEGINNING TO BLOSSOM OVER VARIOUS METRO SITES...MORNING SUN ENERGY WITHIN A HUMID AND UNSTABLE AIR MASS TO KICK ACTIVITY OFF. MORE PRONOUNCED INFLUENCE FROM THE EASTERN UPPER RIDGE WILL KEEP COVERAGE TO A MINIMUM AS COMPARED TO RECENT DAYS. PRIMARILY VFR...A FEW HOURS OF NON-METRO OVERNIGHT TUESDAY MORNING MVFR WITH A RETURN CHANCE FOR AN HOUR (OR TWO) OF IFR CEILINGS. SIMILAR CONVECTIVE BEHAVIOR TUESDAY WITH A HIGHER CHANCE OF MORE AREAL EARLY DAY SHRA/EARLY AFTERNOON -TSRA COVERAGE AS A HIGHER SLUG OF MOISTURE COMES ONSHORE NORTH OF A BAY OF CAMPECHE TROPICAL WAVE/WEAK CIRCULATION. 31 && .PREV DISCUSSION... /ISSUED 1025 AM CDT MON SEP 1 2014/ UPDATE... SEE MORNING UPDATE. .DISCUSSION... 12Z SOUNDING DATA SHOWS PW VALUES BETWEEN 2.00 AND 2.10 INCHES AND CONVECTIVE TEMPS IN THE MID/UPPER 80S. 850MB MOISTURE LEVELS HAVE DROPPED A LITTLE FROM YESTERDAY BUT IT STILL LOOKS PLENTY MOIST. AT 700 MB...A WEAK TROUGH EXTENDS FROM TEXARKANA TO SAN ANTONIO WITH SLIGHTLY DEEPER MOISTURE NOTED AROUND THE ARKLATEX. AT 250 MB...UPPER LEVEL RIDGING LOOKS A BIT STRONGER AND SUBSIDENCE FROM THE RIDGE IS EDGING EVER CLOSER TO SE TX. WIDELY SCATTERED SHRA/TSRA WILL BEGIN TO DEVELOP WITH HEATING. PREV FCST HAS ALL THIS COVERED SO NO UPDATE IS REQUIRED AT THIS TIME. 43 && PREV DISCUSSION... /ISSUED 628 AM CDT MON SEP 1 2014/ .DISCUSSION... SEE AVIATION FOR 12Z TAF DISCUSSION. .AVIATION... IFR CIGS HAVE OVERSPREAD THE NORTHERN TAF SITES THIS MORNING BUT SHOULD BEGIN TO IMPROVE QUICKLY AFTER SUNRISE. LIGHT SHRA OFFSHORE APPROACHING GLS AND SHOULD GRADUALLY SPREAD INLAND THROUGH THE MORNING HOURS. LESS MOISTURE TO WORK WITH TODAY BUT COULD STILL SEE SOME ISOLATED ACTIVITY INLAND. INSTABILITY HIGH ENOUGH TO GO WITH VCTS THROUGH THE EARLY AFTERNOON FOR METRO AREA TAF SITES. ANOTHER ROUND OF MVFR/IFR CIGS POSSIBLE AGAIN EARLY TUESDAY. 38 && PREV DISCUSSION... /ISSUED 432 AM CDT MON SEP 1 2014/ .DISCUSSION... LOW PRESSURE IN THE PLAINS SHOULD DEEPEN TODAY AND SUPPORT STRONGER SE WINDS AT THE SFC. TROPICAL MOISTURE HAS DECREASED SOME ACROSS THE AREA BUT PRECIP WATER VALUES STILL REMAIN AROUND 1.9-2 INCHES PER SOUNDINGS AND GOES SOUNDER DATA. UPPER LEVEL TROUGH OVER THE PLAINS WILL PULL TOWARDS THE GREAT LAKES WITH A TRAILING SHORTWAVE MOVING ACROSS THE C PLAINS BY THIS AFTERNOON. UPPER LEVEL RIDGE IS IN THE PROCESS OF BECOMING MORE ESTABLISHED OVER THE AREA AS HEIGHTS SHOULD RISE TODAY. UPPER LEVEL RIDGE SHOULD REMAIN BROAD AND FLAT ACROSS THE SOUTHERN U.S. INTO TUE/WED. IR SATELLITE IMAGERY OVER THE CARIBBEAN SHOWS A TROPICAL WAVE MOVING OVER THE YUCATAN THIS MORNING. THIS WAVE SHOULD EMERGE INTO THE BAY OF CAMPECHE TONIGHT INTO TUE. THE GFS/ECMWF AGREE WITH KEEPING THE TROPICAL WAVE AN OPEN WAVE MOVING TOWARDS THE MEXICAN COAST. THE NAM AND CANADIAN CLOSE OFF A CIRCULATION WITH THE POSSIBILITY OF A TROPICAL STORM FORMING BEFORE LANDFALL TUE NIGHT INTO WED. CANADIAN IS MOST AGGRESSIVE. NHC GIVES THE SYSTEM A 60 PERCENT CHANCE OF TROPICAL CYCLONE DEVELOPMENT THE NEXT 48HRS AND 70 PERCENT CHANCE OVER NEXT 5 DAYS. THE ENVIRONMENT IS AT LEAST LOOKING MORE FAVORABLE FOR DEVELOPMENT. LATEST FORECASTS HAVE ALL BEEN VERY CONSISTENT WITH BRINGING THE SYSTEM REGARDLESS OF STRENGTH INTO THE MEXICO COAST. GREATEST IMPACT FROM THIS SYSTEM ON THE TX COAST WILL BE INCREASING SEAS AND TROPICAL MOISTURE. WHILE THE UPPER LEVEL RIDGE WILL BE IN PLACE...THERE STILL SHOULD BE PLENTY OF MOISTURE FOR THUNDERSTORM CHANCES TUE/WED SO WILL KEEP 30/40 POPS IN THE FORECAST WITH 50 POPS ON TUE. LOCALLY HEAVY RAINFALL WILL AGAIN BE POSSIBLE WITH INTENSE RAIN RATES IN STRONGER STORMS. THE REST OF THE WEEK WILL BE A BATTLE BETWEEN SUBSIDENCE FROM THE UPPER LEVEL RIDGE AND CONVECTION DEVELOPING DUE TO DAY TIME HEATING WITH THE TROPICAL MOISTURE. FORECAST WILL AT LEAST KEEP 20 POPS FOR THE OF THE WEEK INTO THE COMING WEEKEND. UPPER LEVEL RIDGE WILL REMAIN STRETCHED OVER TX WITH WEAKLY AMPLIFIED ALMOST ZONAL JET STREAM FLOW ACROSS THE NORTHERN HALF OF THE U.S. MAIN DIFFERENCES IN THE GFS/ECMWF FOR THE EXTENDED FORECAST IS A BACK DOOR FRONT COMING INTO THE AREA PER THE ECMWF. THIS WILL STILL BE DIFFICULT TO DO SINCE THE PATTERN IS STILL WEAKLY AMPLIFIED AND THE RIDGE MAY BE STRONG ENOUGH TO KEEP THE FRONT OUT OF THE AREA. 39 && .MARINE... ISOLATED SHOWERS WILL CONTINUE ACROSS THE COASTAL WATERS TODAY. EXPECT ONSHORE WINDS TO PERSIST THROUGH MUCH OF THE WEEK WITH SPEEDS INCREASING BEGINNING LATE TONIGHT AS PRESSURES BEGIN TO LOWER ACROSS THE BAY OF CAMPECHE. MAY NEED CAUTION FLAGS AS EARLY AS TONIGHT BUT LIKELY BEGINNING ON TUESDAY. APPROACHING SWELLS WILL BRING WAVE HEIGHTS UP BY ANOTHER FOOT OR TWO ACROSS THE OFFSHORE WATERS BY WEDNESDAY. 38 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 77 94 76 94 75 / 10 30 20 20 10 HOUSTON (IAH) 77 91 76 92 76 / 20 50 20 30 10 GALVESTON (GLS) 81 88 81 89 81 / 30 40 20 30 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ DISCUSSION...42 AVIATION/MARINE...31

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