Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 020253
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
953 PM CDT TUE SEP 1 2015

.DISCUSSION...
SEE THE UPDATE DISCUSSION BELOW.

&&

.UPDATE...
THE ELONGATED UPPER LEVEL LOW PRESSURE TROUGH WAS OVER SE TX AT
MID EVENING. LOW PRESSURE IN THE FLOW WAS ALSO LOCATED BETWEEN
FREEPORT AND GALVESTON. THE MAJORITY OF THE RAINFALL WAS ALSO
LOCATED OFF TO THE EAST TOWARD THE LA COAST. THE LATEST HIGHER
RESOLUTION MODELS WERE FORECASTING REDEVELOPMENT MANLY ALONG AND
OFF THE COAST LATER TONIGHT...ALTHOUGH THE COVERAGE WAS LESS THAN
PREVIOUSLY ANTICIPATED. SLIGHTLY COOLER TEMPERATURES WERE ALSO IN
PLACE ACROSS THE AREA. BECAUSE OF THIS...UPDATED THE FORECAST AND
REVISED DOWN THE POPS...AND TWEAKED TEMPERATURES.

40

&&

.PREV DISCUSSION... /ISSUED /

DISCUSSION...
00Z TAF DISCUSSION IN AVIATION SECTION.

AVIATION...
UPPER LEVEL LOW OVER SE TX SUPPORTED SCT SHRA/TSRA MAINLY SOUTH
OF KIAH WHICH IMPACTED KGLS THE MOST. SHRA/TSRA ARE PRETTY CLOSE
TO BEING DONE WITH A FEW SHRA W OF KLBX. WILL NOT CARRY ANY
MENTION OF CONVECTION OVERNIGHT FOR THE TAFS AS BOUNDARY LAYER
LOSES HEATING AND HAS STABILIZED WITH CONVECTION.

TOMORROW WILL BE ANOTHER CHALLENGE WITH CONVECTION. TIMING OF
VCSH/VCTS FOR TOMORROW MORNING SIMILAR TODAY WITH ACTIVITY
DEVELOPING ALONG THE COAST AND PUSHING INLAND. HARD TO SAY HOW
MUCH THE ATMOSPHERE HAS BEEN STABILIZED WITH CONVECTION TODAY
SINCE UPPER LOW STILL SHOULD BE IN THE AREA AND PRECIP WATER
VALUES WILL BE HANGING AROUND 2 INCHES. QUITE POSSIBLE THAT
SHRA/TSRA COULD DEVELOP FARTHER INLAND BUT MORE ISO IN NATURE.
TAFS WILL MENTION VCSH DURING THE EARLY AFTERNOON BUT WAIT FOR 00Z
MODEL RUNS TO GET A BETTER HANDLE ON CONVECTIVE TRENDS TOMORROW.

39

PREV DISCUSSION... /ISSUED /

DISCUSSION...
SHOWER AND THUNDERSTORM COVERAGE HAS DECREASED ACROSS SOUTHEAST TEXAS
THIS AFTERNOON. PARTS OF THE AREA...ESPECIALLY IN AND AROUND GALVESTON
ISLAND...SAW SOME LOCALLY HEAVY RAINFALL OF 2 TO OVER 4 INCHES WHICH
LED TO SOME FLASH FLOODING. WHILE THE MID/UPPER LEVEL LOW APPEARS TO
HAVE MOVED OFF TO THE NORTHEAST...ANOTHER CIRCULATION CENTER HAS FORMED
IN/AROUND THE MATAGORDA BAY AREA. SOME SHOWERS AND THUNDERSTORMS HAVE
BEGUN TO DEVELOP IN ASSOCIATION WITH THIS FEATURE...AND THINK WE COULD
SEE SOME MORE DEVELOPMENT THIS EVENING AND OVERNIGHT IN/AROUND THIS
AREA. FOR THE NEXT SEVERAL DAYS...WILL GENERALLY CALL FOR LOWER POPS
WELL INLAND (WHERE MID/UPPER LEVEL HIGH PRESSURE MIGHT BEGIN TO BECOME
THE DOMINATE FEATURE) AND HIGHER POPS NEAR THE COAST AND OFFSHORE (WHERE
BOTH A MID/UPPER LEVEL TROF AXIS AND PRECIPITABLE WATER VALUES AROUND
2 INCHES WILL CONTINUE TO RESIDE). LOCALLY HEAVY RAINFALL COULD DEVELOP
AGAIN WITH THESE FUTURE STORMS...AND CANNOT RULE OUT FUNNEL CLOUD AND/OR
WATERSPOUT FORMATIONS TOO. IT WILL OBVIOUSLY BE WARMER WELL INLAND WITH
LESS CLOUD COVER AND FEWER STORMS...AND NOT AS WARM CLOSER TO THE COAST
AND OFFSHORE WHERE THE BULK OF CLOUDS AND STORMS WILL BE LOCATED. BY
THE END OF THE WEEK AND OVER THE HOLIDAY WEEKEND...IT LOOKS LIKE WE
WILL BE GETTING BACK INTO A MORE DIURNALLY DRIVEN PATTERN OF A CHANCE
OF MAINLY LATE MORNING THROUGH EARLY EVENING SHOWERS AND THUNDERSTORMS.
42

MARINE...
A FEW SHOWERS AND THUNDERSTORMS CONTINUE TO LINGER ACROSS THE MARINE
ZONES THIS AFTERNOON. HIGH RESOLUTION GUIDANCE SHOWS THAT A BRIEF
BREAK IN THIS ACTIVITY WILL BE POSSIBLE THIS EVENING TO LATE TONIGHT
BEFORE AN UPPER DISTURBANCE MOVES OVER THE NORTHWEST GULF OF MEXICO.
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP
ALONG THE COAST EARLY WEDNESDAY MORNING AND REMAIN THROUGH THE DAY
AS THIS HAPPENS... WITH HEAVY RAINFALL AND GUSTY WINDS ACCOMPANYING
THIS ACTIVITY. VISIBILITIES MAY BE LIMITED TO 1 NAUTICAL MILE OR
LESS AT TIMES DUE TO HEAVY RAINFALL. ALSO CANNOT RULE OUT AN
ISOLATED WATERSPOUT THREAT DURING THE DAY WITH AMPLE TROPICAL
MOISTURE AND A LIGHT WIND PROFILE IN PLACE ABOVE THE SURFACE. EXPECT
SHOWERS AND THUNDERSTORMS TO CLEAR THE MARINE AREAS SOMETIME
WEDNESDAY EVENING BUT PERIODS OF SHOWERS AND THUNDERSTORMS WILL
REMAIN WILL POSSIBLE THROUGH THE END OF THE WEEK. OTHERWISE... WEAK
TO OCCASIONALLY MODERATE ONSHORE FLOW IS EXPECTED TO PERSIST INTO
THE HOLIDAY WEEKEND WITH SEAS GENERALLY 1-3 FEET.

HUFFMAN

PREV DISCUSSION...

AVIATION...
FOR THE 18Z TAFS... MAIN AVIATION CONCERNS CENTER AROUND ONGOING
TSRA/SHRA ACTIVITY AT THE TERMINALS WITH ADDITIONAL DEVELOPMENT
EXPECTED AGAIN ON WEDNESDAY.

SCATTERED TO NUMEROUS THUNDERSTORMS ASSOCIATED WITH A MID TO
UPPER LEVEL DISTURBANCE CONTINUE TO MOVE ACROSS THE TERMINALS THIS
AFTERNOON. BULK OF ACTIVITY IS CONCENTRATED NEAR AND NORTH OF CXO
WITH AN ADDITIONAL BROKEN LINE CLEARING THE HOUSTON TERMINALS AND
SOUTHWARD. STARTING TO SEE ADDITIONAL ACTIVITY DEVELOP OVER THE
GULF AND THIS WILL NEED TO BE MONITORED FOR THE COASTAL SITES THIS
AFTERNOON. HAVE VCTS AT ALL TERMINALS THROUGH 21Z AS ACTIVITY
EXITS THE AREA... WITH ANOTHER ROUND OF SHRA/TSRA POSSIBLE AGAIN
EARLY WEDNESDAY MORNING OVER THE COASTAL WATERS AND SPREADING
NORTH INTO THE TERMINALS THROUGH WEDNESDAY AFTERNOON AS THE
AFOREMENTIONED DISTURBANCE DRAWS CLOSER TO THE REGION.

OTHERWISE... LIGHT AND VARIABLE TO LIGHT AND SOUTHERLY WINDS
EXPECTED FOR THE TERMINALS THROUGH THE PERIOD WITH VFR CONDITIONS
OUTSIDE OF TSRA/SHRA ACTIVITY. SOME STRONGER WIND GUSTS
APPROACHING 20 KNOTS WILL BE POSSIBLE IN CONVECTIVE ACTIVITY AS
WELL AS MVFR VISIBILITIES. COULD SEE A FEW HOURS OF MVFR
VISIBILITIES AT CXO AGAIN WEDNESDAY MORNING AS WELL AT CXO... BUT
ONLY INCLUDING A TEMPO MENTION ATTM.

HUFFMAN

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      72  91  73  94  73 /  10  30  20  30  10
HOUSTON (IAH)              72  88  73  92  73 /  20  50  30  40  20
GALVESTON (GLS)            78  87  79  88  79 /  40  60  40  50  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

DISCUSSION...40
AVIATION/MARINE...39



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