Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 282319
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
619 PM CDT THU APR 28 2016

.AVIATION...
A WARM FRONT WAS WORKING ITS WAY SLOWLY NORTHWARD THROUGH SE TEXAS
THIS EVENING. MVFR TO IFR CONDITIONS HAVE ALREADY DEVELOPED AT 23Z
AND EXPECT THESE CONDITIONS TO BECOME WIDESPREAD BY 05Z. IFR LOOKS
LIKELY AFTER 09Z. THE MODELS LIFT THE CONDITIONS TO VFR BY MIDDAY
ON FRIDAY. THERE IS SOME DISAGREEMENT BETWEEN THE MODEL SOLUTIONS
FOR RAIN AND THUNDER CHANCES ON FRIDAY. BEST CONSENSUS IS LATE IN
THE AFTERNOON THROUGH THE EVENING.

40

&&

.PREV DISCUSSION... /ISSUED 326 PM CDT THU APR 28 2016/

DISCUSSION...
FLASH FLOOD WATCH IN EFFECT FOR AREAS GENERALLY ALONG AND NORTH
OF A LINE FROM WHARTON TO HOUSTON TO GROVETON FRIDAY AFTERNOON
THROUGH EARLY SUNDAY MORNING. HEAVY RAINFALL THREAT INCREASING
FOR FRIDAY AFTERNOON THROUGH SATURDAY NIGHT. SATURATED SOILS
ACROSS THE REGION WILL BE INCAPABLE OF ABSORBING THE HEAVY
RAINFALL. INTENSE RAINFALL RATES WILL BE LIKELY DURING THE WATCH
PERIOD ESPECIALLY LATE FRIDAY AFTERNOON IN THE WEST EXPANDING EAST
AND NORTHWARD FRIDAY NIGHT AND SATURDAY WHICH COULD DIRECTLY
IMPACT THE AREAS HARDEST HIT BY LAST WEEKS DELUGE. RAINFALL RATES
OF 3" PER HOUR ARE WITHIN THE REALM OF POSSIBILITY GIVEN THE
ABUNDANT MOISTURE AND STRONG MOISTURE TRANSPORT INTO THE SYSTEM.
NAEFS ENSEMBLES PAINTING A SWATH OF 99TH PERCENTILE OR GREATER IVT
ACROSS THE REGION 00-12Z SATURDAY.

IN THE SHORT TERM EXPECT THE WARM FRONT TO LIFT NORTHWARD THE
REMAINDER OF THE AFTERNOON AND NIGHT - LEADING TO MOSTLY CLOUDY
TO CLOUDY SKIES WITH A WARM AND HUMID NIGHT. MARINE OBSERVATIONS
CONTINUE TO SHOW DEWPOINTS OF 75 TO 77 WELL SOUTH OF THE WARM
FRONT WHICH IS NEAR THE I-10 CORRIDOR AS OF 18Z.

RAIN CHANCES INCREASE AFTER SUNSET IN THE NORTHWEST TONIGHT WITH
PROXIMITY OF THE WARM FRONT AND SUBTLE S/W MOVING THROUGH NE
MEXICO...RAIN RATES SHOULDN`T BE HIGH BUT CAN`T RULE OUT A
THUNDERSTORM OR TWO. FRIDAY GETS MORE TROUBLESOME WITH MODEL
TIMING DIFFERENCES AND INITIALLY WAS PLANNING TO ISSUE THE FLASH
FLOOD WATCH TO BEGIN AROUND 6 PM FRIDAY BUT AFTER SEEING THE HIGH
RES ARW AND ECMWF HAVE BEGUN THE FLASH FLOOD WATCH EARLIER TO
AVOID MISSING THE THREAT OF THE HEAVY RAINFALL STARTING EARLIER
THAN CURRENTLY EXPECTED. BOTH OF THOSE MODELS ALLUDE TO AN MCS
DEVELOPING AND MOVING INTO THE WESTERN AREAS FRIDAY AFTERNOON.
THOUGH CONFIDENCE ON THOSE SPECIFICS ISN`T VERY HIGH THE
CONFIDENCE OF HEAVY RAINFALL UNFOLDING FRIDAY NIGHT INCREASES
DRAMATICALLY WITH A STRONG LLJ/MASSIVE MOISTURE TRANSPORT ORIENTED
THROUGH THE REGION UNDER AN AREA OF INCREASING DIFFLUENCE. THINK
IT IS STILL TOO EARLY TO TRY TO PINPOINT ANY SPECIFIC AREA BUT
THIS PATTERN IS VERY FAVORABLE FOR HEAVY RAINFALL. SOUNDINGS SHOW
A GOOD DEAL OF DESTABILIZATION 00Z SATURDAY THROUGH 18Z SATURDAY
AND THIS WILL LEAD TO AN INCREASE IN THE RAINFALL RATES AND
INCREASE THE SEVERE WEATHER THREAT AS WELL. GUSTY WINDS AND HAIL
SHOULD BE THE MAIN THREATS OF SEVERE...AND AS WE SAW WITH OUR
EVENT TWO DAYS AGO THE WET GROUND AND STRONG WINDS IS A VERY
DANGEROUS COMBINATION FOR BRINGING DOWN TREES.

AT SOME POINT SATURDAY NIGHT OR SUNDAY WEAK UPPER RIDGING OCCURS
OVER SETX WITH A WEAK PACIFIC FRONT SLOWING AND STALLING (PROBABLY
NEAR THE COAST OR JUST OFFSHORE) WHICH SHOULD HELP TO LESSEN THE
COVERAGE OF STORMS TO THE NORTH BUT COULD FOCUS STORMS MORE TOWARD
THE COAST. THE STALLED FRONT REMAINS A PLAYER IN THE WEATHER
SUNDAY AND MONDAY BEFORE THE NEXT UPPER TROUGH ROTATES THROUGH
MONDAY MORNING-TUESDAY MORNING...BRINGING ANOTHER THREAT OF
WIDESPREAD RAINFALL. THIS IS GOING TO STRONGLY DEPEND ON HOW
WORKED OVER THE ATMOSPHERE GETS IN PRIOR PERIODS AND RECOVERY OF
LL MOISTURE. BY TUESDAY NIGHT THE CONSENSUS OF THE GLOBAL MODELS
IS A STRONGER PUSH OF COOL AIR OUT INTO THE GULF AND THE REGION
GETTING A MUCH NEEDED BREAK FROM THE RAINFALL WEDNESDAY THROUGH
FRIDAY.

45

MARINE...
HAVE RAISED CAUTION FLAGS FOR THE 00-60 NM WATERS BEGINNING AT
6 PM TONIGHT IN ANTICIPATION OF STRENGTHENING SOUTHEAST WINDS
AND BUILDING SEAS DURING THE OVERNIGHT HOURS. SEA HEIGHTS SHOULD
EVENTUALLY REACH 7 FEET OR MORE ACROSS PORTIONS OF THE WATERS...
AND WE`LL LIKELY NEED SMALL CRAFT ADVISORIES. THIS BUILDING SURF
WILL ALSO LEAD TO AN INCREASING THREAT FOR RIP CURRENTS. HIGHEST
TIDE LEVELS SHOULD COME DURING HIGH TIDE TIMES ON FRIDAY AND
SATURDAY...ESPECIALLY CLOSE TO THE HIGHWAY 87 AND 124 CONNECTION
NEAR THE BOLIVAR PENINSULA. MARINERS SHOULD STILL PLAN ON PERIODS
OF SHOWERS AND THUNDERSTORMS OVER THE WEEKEND AS A SLOW MOVING COLD
FRONT TAKES ITS TIME MOVING OFF THE COAST SUNDAY OR SUNDAY NIGHT.
EAST TO NORTHEAST WINDS ARE ANTICIPATED FOR THE FIRST HALF OF NEXT
WEEK.  42

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      74  87  71  84  68 /  50  60  80  70  30
HOUSTON (IAH)              74  87  72  83  70 /  20  40  70  70  50
GALVESTON (GLS)            75  81  76  80  73 /  10  40  50  50  60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...FLASH FLOOD WATCH FROM FRIDAY AFTERNOON THROUGH SUNDAY MORNING
     FOR THE FOLLOWING ZONES: AUSTIN...BRAZOS...BURLESON...
     COLORADO...FORT BEND...GRIMES...HARRIS...HOUSTON...
     MADISON...MONTGOMERY...POLK...SAN JACINTO...TRINITY...
     WALKER...WALLER...WASHINGTON...WHARTON.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 6 AM CDT FRIDAY FOR
     THE FOLLOWING ZONES: 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...43
AVIATION/MARINE...40



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