FXUS64 KHGX 302119
AFDHGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
319 PM CST MON NOV 30 2009
.DISCUSSION...
A COLD FRONT IS WELL OFF THE UPPER TX COAST THIS AFTERNOON WITH
STRONG NORTHERLY WINDS. COLD ADVECTION REMAINS IN PLACE WITH
CLOUD COVER OVER MUCH OF SE TX. THIS HAS HELD TEMPS IN THE 50S
FOR MOST OF THE AREA TODAY. STRONG FLOW ALOFT HAS PROVIDED ENOUGH
LIFT TO SUPPORT SOME OFF/ON LIGHT RAIN OVER THE AREA. 12Z UPPER
LEVEL ANALYSIS SHOWS A STRONG CLOSED LOW OVER THE BAJA PENINSULA
AND NOW MOVING ACROSS NORTHERN MEX. THE CLOSED LOW SHOULD MOVE
TOWARDS THE BIG BEND/TRANS-PECOS BY TUE EVENING. THIS WILL SUPPORT
THE DEVELOPMENT OF A COASTAL LOW ALONG THE FRONTAL BOUNDARY TUE
MORNING. NE WINDS WILL INCREASE ALONG THE COAST AND POSSIBLY
CAUSE LOCALIZED COASTAL FLOODING. COASTAL FLOOD ADVISORY WILL
PROVIDE THE DETAILS ON HIGHER TIDE LEVELS ESPECIALLY FOR BOLIVAR
PENINSULA. RAIN CHANCES WILL INCREASE DURING THE DAY WITH THE
BEST CHANCES IN THE AFTERNOON AND NIGHT. THE CLOSED LOW WILL BE
ON TRACK TO CROSS TX TUE NIGHT INTO WED MORNING WITH THE BEST QG
LIFT FROM 00Z TO 06Z WED. POPS AT 90 PERCENT LOOK GOOD GIVEN THIS
UPPER LEVEL SUPPORT. THE CLOSED LOW AND MAIN TROUGH AXIS SHOULD
PAS THROUGH BY 18Z WED AND LIKELY BRING AN END TO ANY PRECIP.
THERE MAY BE SOME WRAP AROUND PRECIP OVER THE NORTHERN PARTS OF
THE FORECAST AREA BUT DRIER CONDITIONS ARE EXPECTED BY 00Z THU.
RAINFALL AMOUNTS LOOK TO BE FAIRLY MODEST WITH MOST AREAS BETWEEN
A QUARTER AND HALF INCH DURING THE DAY AND THEN MAYBE A HALF INCH
TO AN INCH OVERNIGHT. THE HEAVIEST RAINFALL WILL BE OFF THE COAST
ASSOCIATED WITH THE COASTAL LOW. ISO THUNDERSTORMS WILL BE
POSSIBLE OFF THE COAST AS WELL.
A DRY FORECAST WILL BE EXPECTED THROUGH THE END OF THE WEEK.
MODEL DIFFERENCES PRESENT THEMSELVES FAIRLY QUICKLY ESPECIALLY ON
FRIDAY. THE 12Z GFS IS A FAR DEPARTURE FROM ITS PREVIOUS RUNS.
THE 12Z ECMWF AND GFS AGREE WITH THE OVERALL SYNOPTIC PATTERN
WITH A LARGE BROAD TROUGH OVER THE MIDWEST STRETCHING INTO THE
PLAINS. THE GFS NOW HAS A POTENT SHORTWAVE COMING ACROSS THE S
ROCKIES INTO TX FRI MORNING. SHOULD THIS REALLY HAPPEN WITH THE
COLD ADVECTION IN PLACE...MOISTURE...FRONTOGENETIC LIFT AND
STRONG QG LIFT...SNOW WOULD BE POSSIBLE. SINCE THIS IS SUCH AN
OUTLIER AND HAS NO OTHER REAL SUPPORT FROM THE OTHER MODEL
GUIDANCE THE FORECAST WILL LEAN MORE ON THE ECMWF WHICH KEEPS A
DRY FORECAST WITH MAYBE SOME PRECIP OFF THE COAST.
REGARDLESS...TEMPERATURES WILL BE ON THE COLD SIDE SO TEMPS WERE
ADJUSTED DOWN TO FALL MORE IN LINE WITH THE 12Z GFS MOS AND 12Z
ECMWF. THE ECMWF DOES BRING RETURN FLOW BACK LATE SAT NIGHT INTO
SUN WHICH IS CLOSE TO THE GFS BUT PERHAPS A LITTLE SLOWER AND NOT
AS AGGRESSIVE WITH ISENTROPIC LIFT. THE FORECAST WILL HOLD WITH
20 POPS FOR THE EARLY PART OF NEXT WEEK.
39
&&
.MARINE...
STRONG NORTH WINDS HAVE DEVELOPED IN THE WAKE OF THIS MORNINGS
COLD FRONT. LOW PRESSURE DEVELOPING EAST OF BROWNSVILLE WILL
SCOOT EAST NORTHEAST THROUGH TUESDAY EVENING. A TIGHT PRESSURE ON
THE NORTH SIDE OF THIS SYSTEM WILL BRING STRONG E-NE WINDS TO THE
COASTAL WATERS. WILL MAINTAIN THE SCA FOR STRONG WINDS AND HIGH
SEAS. OFFSHORE WINDS ARE EXPECTED TO WEAKEN ON THURSDAY BUT
INCREASE AGAIN ON FRIDAY.
TIDE LEVELS WILL AGAIN BECOME AN ISSUE. E-NE WINDS DEVELOPING
LATE TONIGHT AND CONTINUING ON TUESDAY WILL BRING ELEVATED TIDE
LEVELS TO THE COAST. AT THIS TIME...ONLY MINOR COASTAL FLOODING
IS EXPECTED. BUT EVEN A 2 FOOT RISE IN TIDES WILL BRING TIDE
LEVELS UP TO 4 FEET NEAR FREEPORT AND 3.6 FEET AT PORT BOLIVAR.
TIDE LEVELS OF THIS MAGNITUDE WILL CAUSE SOME MINOR COASTAL
FLOODING. STILL SOME UNCERTAINTY WITH REGARD TO THE TRACK AND
INTENSITY OF THE COASTAL LOW SO HAVE OPTED FOR A COASTAL FLOOD
ADVISORY IN LIEU OF A WARNING. NAM WINDS ARE CONSIDERABLY WEAKER
THAN THE GFS AND ECMWF. THE GFS TRACK RECORD WITH COASTAL LOWS
THIS FALL HAS BEEN SUPERIOR TO THE GFS SO WILL USE GFS WIND
FIELDS. 43
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 45 49 42 54 35 / 30 80 90 30 10
HOUSTON (IAH) 47 50 43 55 37 / 30 80 90 20 10
GALVESTON (GLS) 53 55 47 58 44 / 50 80 90 20 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...COASTAL FLOOD ADVISORY FROM 3 AM TO 4 PM CST TUESDAY FOR THE
FOLLOWING ZONES: BRAZORIA...CHAMBERS...GALVESTON...
MATAGORDA.
GM...SMALL CRAFT ADVISORY UNTIL 6 AM CST THURSDAY 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...39
AVIATION/MARINE...43
