FXUS64 KHGX 120317
AFDHGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
917 PM CST FRI DEC 11 2009
.AVIATION...
UPDATED KIAH AND KHOU TO PUT VCTS AS RADAR IS SHOWING ISOLATED
LIGHTNING STRIKES IN PCPN MOVING FROM SW TO NE TOWARD TAF SITES.
CIGS AND VSBY SHOULD CONTINUE TO TREND LOWER DURING THE NIGHT AS
PCPN BECOMES MORE WIDESPREAD.
&&
.PREV DISCUSSION... /ISSUED 858 PM CST FRI DEC 11 2009/
UPDATE...
ALL PARAMETERS LEADING TO -SHRA MENTIONED IN PREVIOUS DISCUSSIONS
OCCURRING THROUGH THE LATE EVENING. KHGX VAD WINDS SUPPORT WEAK
WAA PATTERN AS ISENTROPIC GLIDE TURNS SCATTERED LIGHT SHOWERS THIS
EVENING INTO MORE WIDESPREAD LIGHT RAIN EARLY SATURDAY MORNING.
SFC ANALYSIS HAS WESTERN GULF INVERTED TROF/WEAK LOW OFF SOUTH
PADRE ISLAND. THIS FEATURE WILL REMAIN PRIMARILY OFFSHORE...HIGHER
QPF ACROSS FIRST TO SECOND TIER SOUTHERN COUNTIES...AS IT TRANSFORMS
INTO AN OPEN WAVE MID-SATURDAY AND TRAVELS INTO COASTAL LOUISIANA.
BEST MID-LOW LEVEL CONVERGENCE TRAILING BEHIND (WITHIN NEAR 1.2-1.3
PWAT AIR MASS) MID TO LATE SATURDAY MAY KEEP A FEW SCT SHWRS AROUND
POINTS EAST OF THE HIGHWAY 59 CORRIDOR. OVERCAST AND COOL FOR ONE
MORE DAY. 31
PREV DISCUSSION... /ISSUED 556 PM CST FRI DEC 11 2009/
AVIATION...
MAINLY MVFR CIGS ACROSS THE REGION AT 00Z WILL LOWER TO IFR CIGS
AFTER 03Z. EXPECT CIGS TO REMAIN IFR THROUGH END OF TAFS WITH CIGS
LOWERING TO AOB 3 HUNDRED FROM 12-18Z WITH VSBY AROUND 2 MILES.
EXPECT PERIODS OF LIGHT RAIN FROM 02Z-14Z ACROSS THE REGION. WINDS
WILL BE FROM EAST TO NORTHEAST AROUND 10 KNOTS AT NORTHERN TAF
SITES AND LOWERING TO AROUND 5 KNOTS AFTER 18Z. SOUTHERN TAF SITES
WILL SEE WINDS 10 TO 15 KNOTS FROM THE NORTHEAST BECOMING LESS
THAN 10 KNOTS AFTER 18Z.
PREV DISCUSSION... /ISSUED 250 PM CST FRI DEC 11 2009/
DISCUSSION...
PRESSURE GRADIENT ACROSS SOUTHERN ZONES BECOMING TIGHTER IN RESPONSE
TO FALLING PRESSURES OVER THE SOUTH TEXAS COASTAL WATERS. INCREASING
ISENTROPIC LIFT OVERNIGHT WILL RESULT IN GOOD CHANCE OF PRECIPITATION
BOTH NAM12 AND GFS BUFR SOUNDINGS INDICATE VERTICAL PROFILES BECOMING
SLIGHTLY UNSTABLE TONIGHT ABOVE THE COOL LOWER LAYER. HENCE WE INCLUDED
SHRA AND ISOLATED TSRA ESPECIALLY FOR THE MARINE REGION. LOW LEVEL
PRESSURE SYSTEM AND ASSOCIATED UPPER LEVEL DISTURBANCE MOVING EAST OF
REGION LATE SATURDAY RESULTING IN FALLING POPS. NOT MUCH DRYING AT LOW
LEVELS LATE SATURDAY AND INTO SATURDAY NIGHT. PRESSURE GRADIENT
BECOMING RATHER FLAT RESULTING IN LIGHT WINDS. MOS INDICATE GOOD
CHANCE OF FOG INLAND AREAS LATER SATURDAY NIGHT. ONSHORE FLOW WILL
RESULT IN RISING DEWPOINTS AND WITH RELATIVELY COOL SST NEARSHORE
AND BAYS WE SHOULD SEE A GOOD CHANCE OF SEA FOG LATER SUNDAY NIGHT
AND INTO MONDAY MORNING. INLAND AREAS WILL HAVE PATCHY FOG. NEXT
STORM SYSTEM INDICATE STRONGER UPPER LEVEL SUPPORT AND MORE
INSTABILITY (SURFACE BASED). PWATS INCREASING TO ABOUT 1.5 INCHES
AHEAD OF FRONTAL SYSTEM. IF ECMWF IS CORRECT NEXT FRONT MAY BE
QUITE A BIT STRONGER. WE SHALL SEE THE NEXT DAY OR SO IF MODELS
WILL BE IN CLOSER AGREEMENT. 37
AVIATION...
WEATHER CONDITIONS WILL DETERIORATE ACROSS THE TERMINALS THIS AFTN
AND TONIGHT AS ISENTROPIC LIFT INCREASES ACROSS THE AREA. MVFR
CONDITIONS ARE OCCURRING OR IMMINENT AT ALL THE TERMINALS. CEILINGS
WILL LOWER TO IFR LEVEL 00-03Z AND TO LIFR LEVEL AROUND 06Z...WHERE
THEY WILL REMAIN THROUGH MOST OF THE DAY SATURDAY. TOWER AT KIAH IS
LIKELY TO BE OBSCURED FOR MOST OF SATURDAY. LIGHT RAIN WILL DEVELOP
BEGINNING LATE AFTN AND BECOME WIDESPREAD BY EARLY EVENING.
VISIBILITIES OF 2-5SM LIKELY IN THE RAIN. SOME ISOLATED EMBEDDED
THUNDER WILL BE POSSIBLE ESPECIALLY TONIGHT...BUT CONFIDENCE AND
TIMING TOO LOW TO PLACE IN TAFS. NORTHEAST WINDS 5-15 KTS
INLAND...15-20 KTS COAST EXPECTED. 35
MARINE...
SFC ANALYSIS SHOWS 1014 MB SFC LOW OFF THE LOWER TX COAST. PRESSURE
GRADIENT BETWEEN THIS FEATURE AND LARGE SFC HIGH OVER THE
SOUTHEASTERN STATES RESULTING IN A TIGHT PRESSURE GRADIENT AND
MODERATE TO STRONG EAST-NORTHEAST WINDS OVER THE WATERS. BUOY 035
REPORTING 7 FT SEAS THIS HOUR. WINDS ARE EXPECTED TO DIMINISH
QUICKLY LATE TONIGHT/SATURDAY MORNING TO 10-15 KTS AS THE LOW PUSHES
EAST OF THE AREA. HOWEVER...WILL TAKE SEVERAL HOURS FOR THE SWELLS
TO SUBSIDE. WILL EXTEND SCA UNTIL 10Z FOR 00-20 NM WATERS AND UNTIL
18Z FOR 20-60 NM WATERS. TIDES ARE CURRENTLY RUNNING ABOUT 1.5 FT
ABOVE NORMAL ALONG THE COAST. THE MAX LEVEL SEEN SO FAR IS 3.2 FT AT
PLEASURE PIER. WILL REISSUE THE COASTAL FLOOD STATEMENT THROUGH
MIDNIGHT BUT WILL NOT HAVE ANY HIGHLIGHTS IN EFFECT. ONSHORE FLOW
WILL RETURN LATE SUNDAY THROUGH MONDAY WITH 5-15 KT WINDS EXPECTED.
SFC DEWPOINTS IN THE 60S/LOWER 70S WILL OVERSPREAD THE WATERS SUN
NIGHT/MONDAY. SEA FOG IS LIKELY TO BECOME AN ISSUE BY LATE SUNDAY
NIGHT AND CONTINUE UNTIL FROPA OCCURS TUESDAY MORNING. FOG WILL BE
MOST DENSE AT THE UPPER REACHES OF THE BAYS. 35
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 43 54 45 74 58 / 90 40 10 10 10
HOUSTON (IAH) 47 56 48 73 60 / 90 50 10 10 10
GALVESTON (GLS) 54 59 53 69 64 / 90 50 10 10 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL MIDNIGHT CST TONIGHT
FOR THE FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY.
SMALL CRAFT ADVISORY UNTIL 4 AM CST SATURDAY FOR THE FOLLOWING
ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL
OUT 20 NM...WATERS FROM HIGH ISLAND TO FREEPORT OUT 20 NM.
SMALL CRAFT ADVISORY UNTIL NOON CST SATURDAY FOR THE FOLLOWING
ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP CHANNEL
20 NM TO 60 NM...WATERS FROM HIGH ISLAND TO FREEPORT 20 TO
60 NM.
&&
$$
DISCUSSION...31
AVIATION/MARINE...34
