311 FXUS64 KHGX 111809 AFDHGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 1209 PM CST FRI JAN 11 2013 .DISCUSSION... 18Z TAF DISCUSSION BELOW. && .AVIATION... AS THE NEXT STORM SYSTEM APPROACHES FROM THE WEST...CEILINGS WILL LOWER TO MVFR WHILE LOWER LEVEL SOUTHERLIES STRENGTHEN. MVFR DECKS WILL PERIODICALLY LOWER INTO IFR DURING THE OVERNIGHT HOURS WITH -SHRA DEVELOPING OVER THE MARITIME AND ADVANCING INLAND. NORTHERN- MOVING SHOWERS...WITH MORE CONSISTENT IFR CEILINGS VERY EARLY SATURDAY MORNING...(NEAR)SURFACE MODERATE SOUTHERLIES VEERING WITH HEIGHT TO SOUTHWEST A FEW THOUSAND FEET UP. THE LOWER LEVEL JET WILL SIGNIFICANTLY STRENGTHEN LATE SATURDAY MORNING INTO AFTERNOON ...WITH THE THREAT FOR ~35-40 KNOT 2K FT WINDS. THUS...LATE PERIOD LLWS IS NOT OUT OF THE QUESTION. NEAR IFR TO MVFR DECKS THROUGH SATURDAY MORNING WITH A HIGHER PROB OF MORE PERSISTENT CENTRAL AND NORTHERN TERMINAL RAIN. 31 && .PREV DISCUSSION... /ISSUED 1002 AM CST FRI JAN 11 2013/ DISCUSSION... FORECAST IS IN GOOD SHAPE...AND NO MORNING UPDATE IS NEEDED. SOUTHEAST WINDS ARE RETURNING TO THE AREA...AND EXPECT THEN TO GRADUALLY INCREASE AS THE DAY PROGRESSES. TEMPERATURES SHOULD WARM INTO THE 70S UNDER INCREASING CLOUD COVER. 42 PREV DISCUSSION... /ISSUED 525 AM CST FRI JAN 11 2013/ DISCUSSION... SEE AVIATION FOR 12Z TAF DISCUSSION AVIATION... ONSHORE FLOW WILL REDEVELOP THIS MORNING IN RESPONSE TO SURFACE HIGH PRESSURE MOVING OUT INTO THE SOUTHERN PLAINS. THIS WILL ALLOW MOISTURE TO RETURN TO THE REGION WITH CIGS BUILDING BACK QUICKLY THROUGH THE AFTERNOON AND LOWERING TONIGHT. HAVE TRENDED A BIT ON THE OPTIMISTIC SIDE OF THE GUIDANCE FOR NOW AS MOST SITES ARE ADVERTISED IFR OVERNIGHT. DO NOT WANT TO GO THAT AGGRESSIVE ON MOISTURE RETURN THIS FAR OUT BUT IF TREND CONTINUES LATER FORECASTS WILL LIKELY HAVE TO ADJUST DOWNWARD TO IFR CIGS FOR THE LATE EVENING THROUGH OVERNIGHT HOURS. GUIDANCE ALSO RATHER BULLISH WITH FOG POTENTIAL BUT FEEL THAT WINDS SHOULD STAY UP ENOUGH TO LIMIT THIS THREAT EXCEPT ALONG THE COAST. 38 PREV DISCUSSION... /ISSUED 410 AM CST FRI JAN 11 2013/ DISCUSSION... WEAK SFC TROUGH PUSHED THROUGH SE TX YESTERDAY BRINGING SOME DRIER AIR TO THE AREA. THIS WILL BE SHORT LIVED AS SFC LOW SHOULD DEEPEN OVER THE PLAINS IN RESPONSE TO A LEAD SHORT WAVE TROUGH WITHIN A DEVELOPING LONG WAVE TROUGH OVER THE WESTERN U.S. SHOULD HAVE CLOUDS AND MAYBE A SHOWER OR TWO THIS AFTERNOON BUT NOT ENOUGH TO REALLY DESERVE MENTION IN THE FORECAST. MAX TEMPS TODAY AND TOMORROW SHOULD BE BACK INTO THE 70S...WELL ABOVE NORMAL. NAM/GFS/ECMWF/SREF SEEM TO BE ALL RELATIVELY SIMILAR FOR THE WEEKEND FORECAST. DEEP LONG WAVE TROUGH MOVES EAST A LITTLE BIT WITH A SECOND SHORT WAVE TROUGH COMING INTO THE S PLAINS LATE SAT. SFC LOW SHOULD FORM ON FRONTAL BOUNDARY OVER NE TX LATE SAT WITH TRAILING COLD FRONT PUSHING INTO THE REGION SAT NIGHT INTO SUN MORNING. COLD FRONT SHOULD REACH HOUSTON AROUND MIDNIGHT AND THEN OFF THE COAST BEFORE 12Z (6AM) SUN. BOUNDARY LAYER WINDS BECOME A BIT MORE VEERED FROM THE SW WITH SW FLOW ALOFT. MOST OF THE UPPER LEVEL FORCING SHOULD BE NORTH OF THE AREA BUT MAY BE ENOUGH WEAK DIVERGENCE FROM THE JET TO SUPPORT THUNDERSTORM ACTIVITY MAINLY SAT NIGHT. MAY HAVE AT LEAST SOME CAPPING ALONG THE COASTAL PLAIN TO TRIM POPS BACK TO THE SW OF HOUSTON TOWARDS VCT. THE COMBINATION OF CAPPING AND WEAK INSTABILITY SHOULD LIMIT OVERALL THUNDERSTORM ACTIVITY AND LIKELY HAVE MORE SHOWERS THAN ANYTHING. THE MAIN FORECAST CHANGE WAS TO INCREASE POPS TO AROUND 50/60 PERCENT FOR THE AREA WITH FROPA. COLD FRONT LOOKS TO BE SHALLOW PER NAM/GFS BUFR FORECAST SOUNDINGS. MODELS HOLD ONTO SOME SOUTHERLY 850MB FLOW WITH ISENTROPIC LIFT AT 290K/295K LEVELS. WHILE THERE SHOULD BE SOME SHOWERS AND THUNDERSTORMS ALONG THE FRONT...THINK BULK OF PRECIP WILL BE POST FRONTAL WITH THE ISENTROPIC LIFT OVER SHALLOW FRONTAL BOUNDARY. THINK SHOWERS/STRATIFORM RAIN WILL HOLD ON FOR SUN INTO MON. THIS MEANS SUN/MON COULD BE COLD RAINY WINTER DAYS BUT NOT EXPECTING ANY ELEVATED THUNDERSTORMS WITH THE LACK OF INSTABILITY. OVERALL UPPER FLOW WILL BE AMPLIFIED WITH A BROAD DEEP TROUGH OVER THE ROCKIES AND PLAINS. FRONT STILL SHOULD PUSH INTO THE GULF BUT EXPECT JET DYNAMICS TO SUPPORT ISENTROPIC LIFT UNTIL DRIER AIR FILTERS INTO THE REGION. THINK THIS BEGINS TO HAPPEN ON TUE ALTHOUGH THE ECMWF STILL HOLDS ONTO PRECIP. DRIER AIR SHOULD HELP CLEAR OUT CLOUD COVER FOR MID WEEK AND ALSO LOWER MIN TEMPS. AT LEAST SOME CLOUD COVER WILL KEEP MAX TEMPS FROM WARMING TOO MUCH FOR EARLY/MID WEEK. GFS/ECMWF DO DIFFER FOR THE END OF NEXT WEEK. BY WED/THU MAIN UPPER TROUGH BEGINS TO MOVE EAST LEAVING BEHIND EITHER A CLOSED LOW (ECMWF) OVER THE S ROCKIES/W TX OR A SHEARED OUT LOW (GFS). BOTH MODELS PUSH THIS LOW/SHEARED TROUGH OVER THE AREA WED NIGHT INTO THUR WITH THE ECMWF HAVING MUCH MORE PRECIP. FORECAST GOES MORE WITH A BLEND OF THE TWO MODELS KEEPING 20/30 POPS WED/THU NEXT WEEK. TEMPS WILL BE TRICKY SINCE ECMWF PUSHES A FRONT THROUGH AND THE GFS DOES NOT. WILL STICK WITH GFS FOR NOW TO KEEP SOME CONSISTENCY WITH PREVIOUS FORECAST. 39 MARINE... SURFACE LOW PRESSURE CURRENTLY ACROSS SOUTHEASTERN COLORADO WILL MOVE INTO THE SOUTHERN PLAINS TODAY ALLOWING WINDS TO BECOME ONSHORE AS THE PRESSURE GRADIENT BEGINS TO TIGHTEN. WINDS WILL STRENGTHEN THROUGH THE DAY ON SATURDAY LIKELY REQUIRING A SCEC ACROSS THE COASTAL WATERS AND PERHAPS AN SCA FOR THE FAR OFFSHORE WATERS. A COLD FRONT WILL MOVE OFFSHORE AROUND DAYBREAK ON SUNDAY. ADVISORY CONDITIONS EXPECTED IN THE WAKE OF THE FRONT WITH STRONG NORTH WINDS AND BUILDING SEAS. 38 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 64 76 44 48 34 / 20 40 60 50 20 HOUSTON (IAH) 64 76 51 52 41 / 30 30 60 60 40 GALVESTON (GLS) 63 71 56 57 44 / 20 30 60 60 40 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ DISCUSSION...42 AVIATION/MARINE...31