Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 280930
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
430 AM CDT THU AUG 28 2014

.DISCUSSION...
SFC ANALYSIS THIS MORNING SHOWS LOW PRESSURE OFF THE LOWER TX
COAST WITH A SHEARED AND WEAK UPPER LEVEL LOW PER LATEST WATER
VAPOR IMAGERY. SFC TROUGH EXTENDS NE ALONG THE TX GULF COAST AND
A FOCUS FOR SCT SHOWERS AND THUNDERSTORMS. SOME OF THIS ACTIVITY
HAS MOVED INLAND ALONG THE UPPER TX COAST. THE ACTIVITY SEEMS TO
BE RUNNING INTO DRIER AIR FARTHER INLAND. HIGHEST MOISTURE CONTENT
SEEMS TO BE JUST ALONG THE COAST LOOKING AT GOES SOUNDER PRECIP
WATER IMAGERY. WITH THAT IN MIND...KEPT 40/50 POPS IN THE FORECAST
FOR TODAY ALONG THE COAST WITH POPS DECREASING RAPIDLY FARTHER
INLAND. MESOSCALE MODELS WRF-ARW/TX TECH WRF AND RAPID REFRESH ALL
CONTINUE TRENDS OF CONVECTION DEVELOPING LATER TODAY INLAND WITH
DAY TIME HEATING AND AS HIGHER MOISTURE SLOWLY PUSHES INLAND. THIS
SEEMS TO BE IN LINE WITH CURRENT FORECAST UPDATE. AS WILL BE THE
CASE THE NEXT COUPLE OF DAYS...STRONGER STORMS WILL BE MONITORED
FOR LOCALLY HEAVY RAINFALL. RAIN RATES OF 1-2 INCHES AN HOUR WITH
NOT BE OUT OF THE QUESTION.

THUNDERSTORM CHANCES WILL CONTINUE THROUGH THE WEEKEND WITH A
GROWING CONCERN OF HEAVY RAINFALL FRIDAY INTO SATURDAY. WATER
VAPOR IMAGERY SHOWS AN AREA OF THUNDERSTORMS IN THE SOUTHERN GULF
NORTH OF THE YUCATAN THAT IS SUPPORTED BY HIGH TROPICAL MOISTURE
PER GOES SOUNDER DATA. GFS/NAM/ECMWF SEEM HAVE RESOLVED THIS
FAIRLY WELL AND FORECAST THIS MOISTURE TO REACH THE UPPER TX
COAST LATE FRI INTO SAT. DURING THIS TIME AN UPPER LEVEL TROUGH
NOW IN THE ROCKIES WILL MOVE ACROSS THE PLAINS WITH THE TROUGH
AXIS PUSHING THROUGH TEXAS. THE NAM AT LEAST ALSO STILL RESOLVES
SOME VORTICITY FROM THE UPPER LOW NOW OVER LOWER TX COAST AND
BRINGS THAT FEATURE NORTHWARD OVER SE TX LATE FRI INTO SAT. THE
GFS AND ECMWF SHOW SIMILAR FEATURES BUT WEAKER. LAST FEW RUNS OF
THE NAM HAVE REALLY HIT SE TX HARD WITH HIGH QPF AMOUNTS
SUGGESTING THE POSSIBILITY OF HEAVY RAINFALL AND FLOODING. THE
GFS/ECMWF KEEP MOST OF THE MOISTURE AND HEAVY RAINFALL FARTHER
EAST INTO SW LA. THE FORECAST WILL KEEP 50/60 POPS BUT CONCERNED
THAT HIGHER RAIN CHANCES MAY BE NEEDED IF THE NAM CONTINUES ITS
TREND AND GAINS SUPPORT FROM THE GFS/ECMWF SOLUTIONS.

RAIN CHANCES DO TAPER OFF SUN THROUGH TUE AS HIGHER MOISTURE
MOVES OUT OF THE AREA AND THE TROUGH AXIS LIFTS NORTHEAST. THERE
IS ANOTHER SHORT WAVE TROUGH MOVING ACROSS THE N PLAINS SUN INTO
MON WITH WEAKLY AMPLIFIED UPPER LEVEL FLOW. THIS SHOULD ALLOW FOR
A FAIRLY FLAT UPPER LEVEL RIDGE TO DEVELOP TUE/WED NEXT WEEK WITH
THE PATTERN BECOMING MORE ZONAL. THE FORECAST KEEPS SOME 20 POPS
IN THE FORECAST FOR ANY CONVECTION THAT DEVELOPS WITH DAY TIME
HEATING BUT ANY THUNDERSTORM ACTIVITY SHOULD BE FAIRLY ISO AT THIS
POINT WITH SUBSIDENCE FROM THE RIDGE. PRECIP WATER VALUES DROP TO
AROUND 1.7-1.9 OR JUST ENOUGH TO SUPPORT A STORM OR TWO.

GFS/CANADIAN AND ECMWF ALSO BRING A TROPICAL WAVE INTO THE S GULF
AND BAY OF CAMPECHE BY TUE. THERE MAY BE SOME TROPICAL
ORGANIZATION TO THE SYSTEM FOR THE MIDDLE OF NEXT WEEK. THE SYSTEM
HAS BEEN CONSISTENTLY FORECAST TO MOVE INTO THE MEXICO COAST BUT
COULD STILL ALLOW FOR MOISTURE TO TRACK NORTHWARDS INTO TX. ECMWF
KEEPS THE SYSTEM AS AN OPEN WAVE WHILE GFS/CANADIAN ARE STRONGER.
AT THIS POINT THERE SHOULD NOT BE ANY IMPACT TO THE TX COAST EVEN
IF THE SYSTEM BECOMES A TROPICAL CYCLONE. NHC GIVES THIS SYSTEM A
20 PERCENT CHANCE OF TROPICAL DEVELOPMENT ONCE REACHING THE NW
CARIBBEAN.

39

&&

.MARINE...

MODERATE SOUTHEAST WINDS WILL CONTINUE TODAY ACROSS THE SE TX
COASTAL WATERS NORTH OF A WEAK LOW PRESSURE AREA THAT WILL MOVE
INLAND LATE TODAY ACROSS SOUTH TEXAS. SCATTERED SHOWERS AND
THUNDERSTORMS WILL CONTINUE THE NEXT SEVERAL DAYS AS WELL AS TIDE
LEVELS AROUND 1 FOOT ABOVE NORMAL. WILL HAVE A CAUTION STATEMENT
FOR THE OFFSHORE ZONES THROUGH MID-DAY WITH 15-20 KT WINDS AND 5
TO 6 FOOT SEAS...EXPECT WINDS TO RELAX SOME THIS AFT...BUT LIKELY
INCREASE AGAIN TONIGHT. 33


&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      95  75  94  75  91 /  30  20  50  30  40
HOUSTON (IAH)              92  75  91  75  88 /  40  30  50  40  60
GALVESTON (GLS)            88  81  89  80  86 /  50  30  50  60  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 2 PM CDT THIS
     AFTERNOON 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...39
AVIATION/MARINE...33


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