Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 291737
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1237 PM CDT FRI AUG 29 2014

.DISCUSSION...
SEE AVIATION FOR 18Z TAF ISSUANCE.

&&

.AVIATION...
SHOWERS AND THUNDERSTORMS CURRENTLY ON THE RADAR THIS AFTERNOON
HAVE REMAINED MOSTLY SCATTERED BUT HIGH RES MODELS CONTINUE TO
SHOW COVERAGE FILLING IN. FORECAST SOUNDING FOR THIS AFTERNOON
SHOW PWAT VALUES AROUND 2.00" WITH K INDEX VALUES APPROACHING 35.
GIVEN INSTABILITY...MOISTURE...AND LIFT FROM AN UPPER LEVEL
DISTURBANCE INCREASING COVERAGE MAKES SENSE. OVERNIGHT THERE WILL
BE A BREAK IN THE ACTIVITY BEFORE ANOTHER UPPER LEVEL DISTURBANCE
MOVES FROM SOUTHWEST TO NORTHEAST OVER THE WATERS TOMORROW MORNING.
MODELS ARE IN DISAGREEMENT WITH THE POSITION OF THE DISTURBANCE.
AS OF NOW LOOKS LIKE HIGHEST RAIN CHANCES WILL BE EAST OF THE TAF
SITES. IN HEAVIER SHOWERS AND THUNDERSTORMS...EXPECT REDUCTIONS IN
VISIBILITY WITH SOME GUSTY WINDS. 23/99

&&

.PREV DISCUSSION... /ISSUED 1019 AM CDT FRI AUG 29 2014/

DISCUSSION...
LITTLE CHANGE HAS BEEN MADE TO THE FORECAST PACKAGE FOR THE MORNING
UPDATE. EAST TO WEST ORIENTED LINE OF SHOWERS AND THUNDERSTORMS IS
CURRENTLY MOVING NORTHWARD ACROSS THE INTERSTATE 10 CORRIDOR...AND
ANTICIPATE MORE DEVELOPMENT (POSSIBLY AREA WIDE) AS THE DAY PROGRESSES
UNDER AN UNSTABLE AIR MASS. SO FAR TODAY...ACTIVITY HAS BEEN MOVING
PRETTY FAST RESULTING IN ONLY A COUPLE SPOTS HAVING RADAR ESTIMATED
RAINFALL TOTALS OVER ONE INCH. STILL LOOKS LIKE BETTER COVERAGE LATE
TONIGHT AND ON INTO TOMORROW AS DEEPER MOISTURE PUSHES NORTHWARD INTO
THE HGX AND LCH AREAS. 12Z NAM MODEL HAS PORTIONS OF OUR AREA IN THE
RRQ OF A 250 MB JET DURING THIS TIME PERIOD...AND IF THE DEEP SURGE
OF MOISTURE DOESN`T EDGE TOO FAR OFF TO OUR EAST THEN PARTS OF SOUTHEAST
TEXAS COULD BE IN DANGER OF SOME LOCALLY HEAVY RAINFALL AND POSSIBLE
FLOODING. THE EASTERN THIRD OR SO OF OUR AREA ALREADY HAS HIGH POPS
AND LOCALLY HEAVY RAINFALL IN THE FORECAST.  42/99

PREV DISCUSSION... /ISSUED 632 AM CDT FRI AUG 29 2014/

DISCUSSION...
SEE AVIATION FOR 12Z TAF DISCUSSION.

AVIATION...
CHALLENGING FORECAST THIS MORNING WITH REGARD TO COVERAGE AND
DURATION OF CONVECTION. SHOULD SEE MORE ACTIVITY ACROSS INLAND
AREAS TODAY AS TROPICAL MOISTURE CONTINUES TO STREAM ONSHORE AND A
REMNANT BOUNDARY FROM THUNDERSTORMS ACROSS NORTH TEXAS MOVES INTO
THE REGION. THINK WE WILL SEE A BIT OF A BREAK FOR THE EVENING
HOURS BEFORE ACTIVITY REDEVELOPS ACROSS THE SOUTHERN HALF OF THE
REGION. 38

PREV DISCUSSION... /ISSUED 457 AM CDT FRI AUG 29 2014/

DISCUSSION...
ATMOSPHERIC CONDITIONS ARE LOOKING MORE FAVORABLE FOR HEAVY
RAINFALL TONIGHT INTO SATURDAY MAINLY FOR E AND SE TX. UPPER LEVEL
ANALYSIS SHOWS AN UPPER LEVEL TROUGH OVER THE C PLAINS AND A WEAK
UPPER LOW OVER S TX WHICH HAS REMAINED QUASI-STATIONARY THE LAST
DAY OR TWO. UPPER LEVEL TROUGH SHOULD PROVIDE SOME STEERING
CURRENTS FOR THE UPPER LOW AND EXPECT IT TO MOVE TOWARDS THE UPPER
TX COAST TONIGHT. THIS UPPER LOW IS ALSO PROVIDING FLOW FOR
TROPICAL MOISTURE TO ADVECT TOWARDS THE NW GULF FOR TONIGHT. IR
IMAGERY ALREADY SHOWS VERY DEEP CONVECTION ASSOCIATED WITH THIS
TROPICAL MOISTURE OVER THE C GULF. THERE IS ALSO A LINE OF STORMS
OVER N TX ASSOCIATED WITH THE UPPER TROUGH OVER THE PLAINS WHICH
SHOULD CONTINUE TO WEAKEN. THE 00Z CRP/LCH SOUNDINGS SHOW 2-2.2
INCHES OF PRECIP WATER. MOISTURE IN THE GULF HAS PW VALUES
APPROACHING 2.5 SO THERE WILL BE CERTAINLY PLENTY OF MOISTURE FOR
THUNDERSTORM ACTIVITY. THERE ARE ALREADY SOME STORMS PUSHING
INLAND WITH DEEPER MOISTURE IN PLACE.

GIVEN THAT THERE WILL BE PLENTY OF MOISTURE/INSTABILITY/LIFT IN
THE ATMOSPHERE...THINK 50/60 POPS LOOK GOOD FOR RAIN CHANCES TODAY
AND THEN INCREASING TO 70/80 PERCENT FOR SAT MORNING. THE
GFS/ECMWF STILL KEEP A GOOD AMOUNT OF MOISTURE AND RESULTING
PRECIP OVER E TX INTO SW LA. THE NAM HOWEVER REMAINS CONSISTENT
SHOWING HIGH PRECIP AMOUNTS OVER PORTIONS OF SE TX FOR SAT
MORNING. THIS STILL RAISES THE CONCERN FOR HEAVY RAINFALL AND
POSSIBILITY OF FLOODING. THINK THE HIGHEST RAIN CHANCES WILL BE
MAINLY EAST OF I-45 AND ALONG THE COAST. THESE AREAS COULD PICK UP
1-3 INCHES OF RAIN VERY EASILY WITH THAT MUCH MOISTURE OVER THE
REGION. HOURLY RAIN RATES COULD REACH THOSE LEVELS ALONE. POSSIBLE
THERE COULD BE POCKETS OF 2-4 INCHES OF RAIN WHICH WOULD THEN
APPROACH FLASH FLOOD GUIDANCE NUMBERS. RIGHT NOW WILL HOLD OFF ON
A FLOOD WATCH BUT IF THERE ARE GOOD RAINFALL AMOUNTS DURING THE
DAY TODAY... MAY NEED A WATCH FOR THE SATURDAY MORNING PERIOD.
THIS WILL NEED TO BE MONITORED CLOSELY.

THUNDERSTORM CHANCES DO TAPER OFF SAT NIGHT INTO SUN. PRECIP WATER
VALUES WILL STILL BE AROUND 2 INCHES AND COULD SUPPORT SCT
THUNDERSTORM ACTIVITY. FORECAST LOOKS GOOD WITH 40/50 POPS AND
LOCALLY HEAVY RAINFALL COULD BE POSSIBLE AGAIN. THE MODELS ALSO
HAVE THE UPPER LEVEL TROUGH PUSHING EAST WITH ANY TROUGH AXIS
SHEARING OUT. UPPER LEVEL RIDGING SHOULD TAKE OVER MON INTO TUE
AND INCREASE SUBSIDENCE OVER THE REGION. THERE SHOULD HOWEVER BE
JUST ENOUGH DEEP MOISTURE TO WARRANT KEEPING AT LEAST SOME MENTION
OF THUNDERSTORM CHANCES. THERE MAY BE A TROPICAL CONNECTION FOR
DEEP MOISTURE REMAINING OVER THE AREA AS A TROPICAL WAVE MOVES
INTO THE S GULF FROM THE YUCATAN ON MON/TUE TIME FRAME. GFS/ECMWF
KEEP THIS TROPICAL SYSTEM DISORGANIZED WHICH THE CANADIAN MAKES
IT A HURRICANE. REGARDLESS THE SYSTEM MOVES INTO MEXICO WITH
REALLY ONLY TROPICAL MOISTURE AFFECTING SE TX. AS SUCH THE FORECAST
WILL KEEP MENTION OF 20 POPS THROUGH THE MIDDLE OF THE WEEK WITH
THE THOUGHT THERE COULD BE A DAY OR TWO WITH BETTER THUNDERSTORM
CHANCES DEPENDING ON AMOUNT OF MOISTURE AND SUBSIDENCE FROM THE
RIDGE.

TEMPERATURE FORECAST WILL BE TOUGH THE NEXT COUPLE OF DAYS WITH
CONVECTION EXPECTED. FARTHER INLAND EXPECT HIGH TEMPS TO REACH THE
MID 90S ESPECIALLY NEXT WEEK. TEMPS MAY REMAIN IN THE 80S FOR MUCH
OF THE DAY TOMORROW DEPENDING ON CONVECTION. MIN TEMPS IN THE
MID/UPPER 70S LOOKS ON TRACK WITH RAIN COOLED TEMPS IN THE LOW 70S
POSSIBLE WITH THUNDERSTORMS MOVING THROUGH THE AREA.

39

MARINE...
MODERATE EAST SOUTHEAST WINDS MAY WEAKEN BRIEFLY AROUND MIDDAY
BEFORE PICKING UP AGAIN FOR THE EVENING AND OVERNIGHT HOURS. HAVE
EXTENDED SCEC THROUGH THE REMAINDER OF THE MORNING AND IT WILL
LIKELY BE REQUIRED FOR TONIGHT INTO EARLY SATURDAY. AN UPPER LEVEL
DISTURBANCE ACROSS THE WESTERN GULF OF MEXICO WILL KEEP ONSHORE
WINDS IN PLACE THROUGH THE WEEKEND WITH SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS THE COASTAL WATERS. 38

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      75  90  75  94  76 /  30  40  20  40  10
HOUSTON (IAH)              76  87  76  92  77 /  50  70  50  50  10
GALVESTON (GLS)            79  85  81  89  82 /  60  80  50  50  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 1 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...42
AVIATION/MARINE...23



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