126 FXUS64 KHGX 211523 AFDHGX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX 1023 AM CDT THU MAR 21 2013 .UPDATE... EARLY MORNING SATELLITE IMAGERY DEPICTING WHAT APPEARS TO BE A SOMEWHAT UNSTABLE REGIONAL ENVIRONMENT...ESPECIALLY OVER THE (NORTH)EASTERN CWA. A MORE MOIST CRP RAOB (IN RELATION TO LCH) WITH A MID-UPPER 60F CONVECTIVE TEMPERATURE...ALONG WITH WEAK RADAR RETURNS MOST LIKELY ASSOCIATED WITH NE CWA LIGHT RAIN... HAS VERY LOW POPS IN THROUGH THE DAY. A PARTLY CLOUDY DAY AS MANY INTERIOR LOCALES WILL REACH THE AVERAGE MIDDLE 70S...AROUND 70F ALONG THE COAST. A WINDY DAY PER A STATE-WIDE 14 MB PRESSURE GRADIENT...ALONG WITH 20 KNOT LOWER LEVEL WIND MIX DOWN (ONCE SURFACE TEMPERATURES WARM INTO THE 70S). 31 && .PREV DISCUSSION... /ISSUED 638 AM CDT THU MAR 21 2013/ DISCUSSION... 12Z TAF DISCUSSION IN AVIATION SECTION. AVIATION... OVERALL EXPECT VFR CIGS THIS AFTERNOON WITH BKN/SCT CLOUD DECKS AROUND 5000FT OR HIGHER. SFC LOW SHOULD CONTINUE TO DEEPEN IN W TX WITH WINDS INCREASING LATE MORNING THROUGH THE AFTERNOON. WINDS DO DIMINISH BUT ONLY TO AROUND 10KTS. OVERNIGHT EXPECT THERE TO STILL BE SOME MIXING AS 35KT LLJ DEVELOPS OVER THE AREA. WITH MOISTURE INCREASING THINK MVFR CIGS LOOK ON TRACK. MODELS ALL SUGGESTING IFR CIGS AND LIFR/IFR VSBY WHICH LOOKS TO PESSIMISTIC GIVEN THE LOW QUALITY OF MOISTURE RETURN FROM THE GULF. POSSIBLE THAT THERE WILL BE A FEW ISO SHOWERS IN THE AREA FRI MORNING BUT JUST NOT CONFIDENT ENOUGH TO PUT IN TAFS. 39 PREV DISCUSSION... /ISSUED 411 AM CDT THU MAR 21 2013/ DISCUSSION... WITH THE SURFACE RIDGE MOVING EAST OF THE STATE THIS MORNING... ONSHORE WINDS WILL RETURN GULF MOISTURE AND WARMER TEMPERATURES ACROSS SE TX TODAY. A TIGHT PRESSURE GRADIENT WILL DEVELOP AND CAUSE BREEZY CONDITIONS TO DEVELOP DURING THE LATE MORNING AND THROUGH THE AFTERNOON. A SHORTWAVE TROUGH WILL MOVE OVERHEAD TONIGHT AND FRIDAY AND MAY HELP TO GENERATE SOME ISOLATED SHOWERS. HOWEVER...A DECENT CAP WILL DEVELOP ON FRIDAY AND LINGER INTO EARLY SATURDAY. THIS SHOULD KEEP A LID ON SHOWER OR THUNDERSTORM DEVELOPMENT. ON SATURDAY AS AN UPPER LEVEL TROUGH DEEPENS OVER THE ROCKIES AND SOUTHERN PLAINS...A STRONG SHORTWAVE TROUGH WILL PUSH INTO TEXAS. COUPLED WITH THIS WILL BE A FRONTAL BOUNDARY SETTING UP ALONG OR JUST TO THE SOUTH OF THE RED RIVER VALLEY. THE GFS ERODES THE CAP OVER SE TX SATURDAY AFTERNOON...ALTHOUGH THE MODEL MAY BE A BIT TOO OPTIMISTIC IN DOING SO. BECAUSE OF THIS SETUP...EXPECT RAIN AND THUNDER CHANCES TO INCREASE ON SATURDAY WITH THE BEST CHANCES OVER THE NORTHERN COUNTIES NEAREST TO THE FRONTAL BOUNDARY. THE MODELS DIFFER ON THE FRONTAL TIMING...WITH THE GFS AND CANADIAN PUSHING THE FRONT THROUGH BY SATURDAY EVENING AND THE ECMWF EARLY SUNDAY MORNING. GIVEN THE FLOW PATTERN ALOFT...THE NAM12 MAY HAVE THE RIGHT IDEA IN PUSHING A DRY LINE IN FROM THE WEST SATURDAY AFTERNOON WITH THE COLD FRONT THEN MOVING ACROSS THE AREA FROM THE NORTH SATURDAY EVENING. AGREE WITH THE DAY 3 SPC OUTLOOK AS THE BUFR SOUNDING FORECASTS DO INDICATE A POTENTIAL FOR AT LEAST ISOLATED STRONG OR SEVERE STORMS MAINLY TOWARD THE FRONTAL BOUNDARY. FOR NOW...WILL GO WITH A 30 PERCENT SOUTH AND 40 PERCENT NORTH FOR SHOWERS AND THUNDERSTORMS ON SATURDAY AND A 20 PERCENT IN THE NORTHEASTERN COUNTIES SATURDAY EVENING. WILL DISCUSS ANY SEVERE THUNDERSTORM CHANCES IN THE HAZARDOUS WEATHER OUTLOOK. WITH THE FRONTAL PASSAGE...THE FIRST HALF OF NEXT WEEK WILL BE DRY. EXPECT A WARMING TREND OVER THE MIDDLE PART OF THE WEEK AS THE WINDS GRADUALLY GO FROM NORTHEAST TO ONSHORE. 40 MARINE... WINDS SHOULD TURN TO THE SOUTHEAST TODAY AND INCREASE. WILL GO AHEAD WITH SCEC FOR THE 0-60NM WATERS STARTING 15Z TODAY GOING TO AT LEAST 03Z/FRI. WINDS SHOULD DROP OFF SOME OVERNIGHT BUT REMAIN AROUND MODERATE LEVELS THROUGH THE WEEKEND. SEAS SHOULD BUILD SOME TODAY IN RESPONSE TO THE WINDS BUT SLOWLY SUBSIDE INTO THE WEEKEND. COLD FRONT SHOULD PUSH OFF THE COAST SAT NIGHT INTO SUN MORNING. GFS SIGNIFICANTLY FASTER THAN THE OTHER MODELS BUT DID A BLEND OF IT WITH NAM/ECMWF. EXPECT SCA CONDITIONS BEHIND THE FRONT SUN INTO SUN NIGHT. NE/E WINDS PERSIST FOR EARLY NEXT WEEK AND MAY HAVE A PERIOD OF PROLONGED SCEC/SCA CONDITIONS. 39 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 77 62 83 63 80 / 20 20 20 20 40 HOUSTON (IAH) 74 61 81 65 81 / 20 20 20 20 30 GALVESTON (GLS) 70 64 75 66 76 / 10 10 20 20 30 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 10 PM CDT THIS EVENING FOR THE FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY... WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL 20 NM TO 60 NM...WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20 TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM. && $$ DISCUSSION...31