Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 291218
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
718 AM CDT FRI MAY 29 2015

.UPDATE...
CANCELED PART OF THE FLASH FLOOD WATCH AND ADJUSTED POPS FOR THE
MORNING.

&&

.DISCUSSION...
WILL CANCEL WESTERN PARTS OF THE FLASH FLOOD WATCH AND ADJUST POPS
LOWER OVER THE WEST FOR THIS MORNING. NEW ZONES OUT SHORTLY. 43

&&

.PREV DISCUSSION... /ISSUED 639 AM CDT FRI MAY 29 2015/

DISCUSSION...
SEE THE 12Z AVIATION DISCUSSION BELOW.

40

AVIATION...
THE LEADING EDGE OF THE DIMINISHING SQUALL LINE WAS LOCATED FROM
KUTS TO THE HOUSTON METRO SITES TO KLBX AT 1130Z. EXPECT THESE TO
CLEAR THROUGH THE SITES BETWEEN 12Z AND 1230Z...AND THEN KGLS BY
13Z. RAIN OCCURRING IN THE TRAILING COLD POOL SHOULD LAST THROUGH
MID MORNING AT THE LATEST. THE RAP13 MODEL DID A DECENT JOB WITH
THE SYSTEM. THE MODEL KEEPS THE POTENTIAL FOR TSRA AT KGLS AND
KLBX THROUGH MIDDAY AND THE POTENTIAL FOR REDEVELOPMENT LATER
THIS AFTERNOON OVER THE OTHER INLAND SITES. VFR EXPECTED TONIGHT
BUT THERE IS AN OUTSIDE CHANCE FOR MVFR CONDITIONS TO DEVELOP.
NEXT BEST CHANCES FOR RAIN AND THUNDERSTORMS WILL BE SATURDAY
AFTERNOON AS A FRONTAL BOUNDARY SINKS SOUTHWARD OF THE RED RIVER
VALLEY.

40

PREV DISCUSSION... /ISSUED 420 AM CDT FRI MAY 29 2015/

DISCUSSION...
FEEL A FLASH FLOOD WATCH IS WARRANTED WITH THE SLOW MOVING
BOUNDARY AND TRAINING OF STORMS. RAINFALL RATES ARE NOT THAT
IMPRESSIVE BUT CONCERNED THAT TRAINING WILL YIELD SOME HIGHER
TOTALS. THE POTENTIAL FOR FLASH FLOODING EXISTS THIS MORNING. THE
WATCH WILL EXPIRE AT NOON.

AT 3 AM...AN OUTFLOW BOUNDARY WAS APPROACHING SE TX WITH SCATTERED
TO NUMEROUS SHRA/TSRA MOVING ACROSS THE WESTERN ZONES. 1-2 INCHES
OF RAIN HAS ALREADY FALLEN ACROSS PARTS OF COLORADO AND WASHINGTON
COUNTIES. THE OUTFLOW BOUNDARYS EASTWARD MOVEMENT HAS SLOWED BUT
STILL EXPECT IT TO PUSH E-SE AND CROSS ALL OF SE TX BY 10-11 AM.
THAT SAID...CLOUD TOPS ARE WARMING AND THE COLD POOL IS LOSING ITS
PUNCH AND HAVE SOME CONCERN THAT THE BOUNDARY COULD STALL OVER THE
AREA AND SERVE AS A FOCUS FOR AFTN CONVECTION. NOT SURE HOW THIS
WILL ALL PLAY OUT. SHORT TERM GUIDANCE HAS PERFORMED WELL
OVERNIGHT BUT THEY DIVERGE WITH WHAT HAPPENS THIS AFTN. THE RAP
HAS WIDESPREAD DEVELOPMENT OVER ALL OF THE AREA...WHILE THE HRRR
KEEPS THINGS QUIET THIS AFTN AND MATCHES UP WELL WITH THE TEXAS
TECH WRF. THE NMM KEEPS THINGS QUIET WITH A CLUSTER OF STORMS
DEVELOPING THIS EVENING WHILE THE ARW MATCHES UP BETTER WITH THE
RAP. BOTH THE GFS/NAM HAVE PW VALUES NEAR 1.80 INCHES THIS AFTN
WITH NO CAPPING AND CONVECTIVE TEMPS IN THE LOWER 80S. FEEL ONCE
THE OUTFLOW BOUNDARY REACHES THE COAST...SUBSIDENCE IN ITS WAKE
WILL KEEP THINGS QUIET FOR MUCH OF THE AFTN WITH SOME
REDEVELOPMENT VERY LATE IN THE AFTN. MUCH DEPENDS ON WHETHER THE
OUTFLOW REACHES THE COAST OR HANGS UP ACROSS SE TX.

SATURDAY STILL LOOKS TO BE THE WETTEST DAY OF THE WEEKEND. PW
VALUES REMAIN AROUND 1.80 INCHES AND UPPER LEVEL WINDS REMAIN
BROADLY DIVERGENT. A WEAK COLD FRONT WILL ENTER SE TX AND CROSS
THE AREA SATURDAY NIGHT AND CLEAR THE COAST EARLY SUNDAY. THE
FRONT WILL SERVE AS A LOW LEVEL FOCUS FOR ADDITIONAL SHRA/TSRA.
COULD GET SOME TRAINING ON SATURDAY WITH THE FRONT SO THE
POTENTIAL FOR LOCALLY HEAVY RAIN IS POSSIBLE. SHRA/TSRA WILL
CONTINUE SAT NITE WITH PW VALUES BETWEEN 1.7-1.8 INCHES. DRIER AIR
WILL WORK INTO SE TX ON SUNDAY IN THE WAKE OF THE FRONT WITH PW
VALUES FALLING TO 1.6 INCHES BY 18Z AND 1.4 INCHES BY 00Z. UPPER
LEVEL WINDS BECOME CONFLUENT BY 00Z SO FEEL RAIN CHANCES WILL
REMAIN HIGH IN THE MORNING WITH CONSIDERABLY DRIER CONDITIONS
DEVELOPING FROM NORTH TO SOUTH IN THE AFTN. PW VALUES ON MONDAY
ARE PROGGED TO FALL BELOW AN INCH SO IT LOOKS LIKE A LONG AWAITED
DRYING TREND WILL BEGIN NEXT WEEK.

NEXT WEEK...SE TX WILL LIE BETWEEN A DEVELOPING UPPER RIDGE OVER
WEST TX AND AN UPPER LEVEL TROUGH OVER THE EASTERN U.S..CAN`T RULE
OUT ISOLATED TO SCATTERED SHRA/TSRA BUT THE OVERALL TREND FOR NEXT
WEEK LOOKS DRIER WITH SEASONAL TEMPERATURES. 43

MARINE...
THE LOW-LEVEL JET FEEDING INTO THE SQUALL LINE MOVING FROM THE HILL
COUNTRY TO SOUTHEAST TEXAS WAS MIXING DOWN AND KEEPING WINDS AT
CAUTION CRITERIA EARLY THIS MORNING. THE MODEL CONSENSUS IS FOR THE
WINDS TO GRADUALLY DIMINISH TODAY AND SATURDAY. IF ANOTHER LINE OF
STORMS DEVELOP FRIDAY NIGHT OR SATURDAY...WINDS COULD BECOME HIGHER
THAN FORECAST OVER THE GULF WATERS AND BAYS. HOWEVER...WITH A COLD
FRONT MOVING INTO SOUTHEAST TEXAS...A RELAXED SURFACE PRESSURE
GRADIENT SHOULD LEAD TO DIMINISHED WINDS AS FORECAST BY THE MODELS.
CONDITIONS ARE EXPECTED TO IMPROVE FOR NEXT WEEK STARTING ON SUNDAY.

40

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      86  70  83  67  83 /  70  20  60  50  40
HOUSTON (IAH)              87  71  86  69  84 /  60  20  60  60  50
GALVESTON (GLS)            84  76  84  74  84 /  40  20  30  40  50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...FLASH FLOOD WATCH UNTIL NOON CDT TODAY FOR THE FOLLOWING ZONES:
     AUSTIN...BRAZORIA...BRAZOS...BURLESON...CHAMBERS...
     COLORADO...FORT BEND...GALVESTON...GRIMES...HARRIS...
     HOUSTON...JACKSON...LIBERTY...MADISON...MATAGORDA...
     MONTGOMERY...POLK...SAN JACINTO...TRINITY...WALKER...
     WALLER...WASHINGTON...WHARTON.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 10 AM CDT THIS MORNING
     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...43



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