National Weather Service Raw Text Product

260 
FXUS64 KHGX 180129
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
829 PM CDT SUN APR 17 2016


.AVIATION...
SHOWERS AND THUNDERSTORMS DEVELOPING IN A SWATH FROM NEAR BYY-BAY
CITY TO LVJ-PEARLAND TO CLL-COLLEGE STATION WHERE LL CONVERGENCE
APPEARS TO BE MAXIMIZED. BROAD DIFFLUENCE ALOFT WITH A MOIST
SOUNDING TO NEAR 600 MB WITH ONGOING DEEP CONVECTION. HAVE MADE
SOME CHANGE TO TAFS TO HIGHLIGHT THE PREVAILING NATURE OF STORMS
THROUGH THE NEXT 12-24 HOURS. GUIDANCE IS ALL OVER THE PLACE ON
WHERE THE HEAVIEST RAINFALL WILL OCCUR AND TIMING...AM EXPECTING
THE SWATH OF STORMS TO CONTINUE AND PROBABLY SLOWLY SHIFT FURTHER
NW AND N WHICH WILL KEEP MOST TERMINALS IMPACTED BY AT A MINIMUM
SHOWERS AND PROBABLY TSRA AT TIMES. SOUNDING FROM TAMU CLL JUST
CAME IN AND IT IS JUICY...1.8 PW/K INDEX 40/CAPE 1650 AND 0-1KM
SRH OF 200. THINK THAT BIG IMPACTS FROM STORM CLUSTERS MAY OCCUR
AFTER 12Z FOR IAH/HOU (AFTER THIS EVENINGS). CIGS SHOULD LOWER
OVER THE EVENING AND MVFR WILL PREVAIL BETWEEN 1000-2000FT. LOWER
CIGS/VISBY WITH STORMS. 

45

&&

.PREV DISCUSSION... /ISSUED 358 PM CDT SUN APR 17 2016/ 

DISCUSSION...
RECENT THINKING IS THAT...WITH ALL OF THE METEOROLOGICAL 
INGREDIENTS IN PLACE...THE (FLASH) FLOOD THREAT IS STILL ALIVE
AND WELL FROM THIS EVENING THROUGH TUESDAY. THE SLOW CHURNING
BROAD UPPER LOW CENTERED OVER THE FOUR CORNERS REGION IS THE
WESTERN LOW IN WHAT HAS BECOME AN OMEGA BLOCKING PATTERN. THE
NEAR ZERO MOVEMENT OF THE WESTERN ATLANTIC LOW...WITH A CENTRAL
CONUS RIDGE WEDGED IN BETWEEN THESE TWO LOWS...WILL ULTIMATELY BE
THE IMPETUS TO WHAT IS SHAPING UP TO BE AN ACTIVE 36 HOURS. AS
MENTIONED ABOVE AND IN PREVIOUS AFDS...ALL OF THE ELEMENTS THAT
YOU NEED FOR FLASH FLOODING LEADING TO RIVER FLOODING ARE IN
PLACE. SECONDARY THREATS WILL BE DAMAGING STORM DOWNBURST WINDS
AND HAIL. UNLESS THIS DOWNSTREAM RIDGE AND ATLANTIC LOW SUDDENLY
DECIDE TO SHEAR OUT AND RELEASE THIS BLOCKING FLOW PATTERN...HIGH
RAINFALL WILL NOT BECOME A MATTER OF 'IF' BUT OF 'WHEN AND WHERE'.
AS OF NOW THE RECENT HIGH RESOLUTION MODELING HAVE BEEN OF LITTLE
TO NO HELP...CONFIDENCE IS GREATEST THAT EITHER A CENTRAL TEXAS
FORMING MCS OR LARGE SCALE NORTH TO SOUTH QLCS WILL DEVELOP SOMETIME
MONDAY. TRAINING THUNDERSTORMS WILL LIKELY PRODUCE 2 TO 3 INCH PER
HOUR AMOUNTS...LOCALLY UPWARDS OF 3 TO 4 INCHES (AS EVIDENCED BY
THIS AFTERNOON'S CLUSTERING OVER THE BASTROP/SMITHVILLE AREA). THUS
..WITH SLOW STEERING VECTOR MOTION...IT WILL NOT TAKE MUCH TIME
TO PRODUCE GREATER THAN 8 INCH AMOUNTS OVER THOSE AFFECTED COUNTIES.
THIS EVENT COULD COMMENCE AS EARLY AS THIS EVENING AND PERSIST
THROUGH MID WEEK. SINCE THIS SCENARIO WILL BECOME MORE MESO-DRIVEN
IN TIME...THE FINER DETAILS OF THE TIMING AND LOCATION OF THE HIGHEST
RAINFALL WILL COME WITH SHORT TERM FORECASTS WHILE CLOSELY MONITORING
RADAR/RAINFALL RATES.

THE UPSTREAM RIDGE BREAKS DOWN GOING INTO MIDWEEK...ALLOWING SOUTHWESTERLY
/DIFFULENT FLOW ALOFT TO BECOME MORE ZONAL WEDNESDAY. A COLD FRONTAL
PASSAGE INTO A SOMEWHAT RE-CHARGED RESIDENT AIR MASS (1.4-1.5 INCH
PWATS) WILL PICK THURSDAY'S RAIN CHANCES BACK UP TO HIGH CHANCE-
LOW LIKELY PROBABILITIES. BACKING HIGH PRESSURE WILL DESCEND DOWN
FROM THE SOUTHERN PLAINS AND BEGIN FEW DAYS OF DRY WEATHER GOING
INTO THE WEEKEND. DAY-TO-DAY TEMPERATURE FORECASTS WILL FOLLOW A
NEAR SIMILAR DIURNAL CURVE...UPPER 60 TO LOW 70 DEW POINTS WILL
MAINTAIN HIGHER HUMIDITY LEVELS THROUGH FRIDAY MORNING...OR BEFORE
THE THURSDAY BOUNDARY PASSAGE. DAILY MINIMUMS TEMPERATURES WILL
GENERALLY BE IN THE MID-UPPER 60S WITH DAILY MAXIMUM TEMPERATURES
IN THE UPPER 70S TO NEAR 80 F.

MARINE... 
A COASTAL FLOOD WARNING REMAINS IN EFFECT FROM PORT OCONNOR TO
HIGH ISLAND AS TIDE LEVELS REMAIN 1.5 TO 3.0 FEET ABOVE NORMAL.
THIS WILL BRING WATER LEVELS TO NEAR 4 FEET IN A FEW PLACES AT
HIGH TIDE. HWY 87 HAS BECOME WATER COVERED AT TIMES AND TODDVILLE
ROAD HAS BEEN WATER COVERED AT TIMES. WINDS ARE EXPECTED TO BECOME
SE AND GRADUALLY DECREASE ON MONDAY AND THREAT FOR COASTAL
FLOODING SHOULD BEGIN TO DIMINISH DURING THE DAY.

A TIGHT PRESSURE GRADIENT BETWEEN LOW PRESSURE OVER SW TX AND HIGH
PRESSURE TO THE EAST WILL MAINTAIN MODERATE TO STRONG E-SE WINDS
TONIGHT. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE GULF
WATERS AND ADJACENT BAYS THROUGH 12Z MONDAY AND MAY NEED TO BE
EXTENDED FOR THE GULF WATERS ON MONDAY MORNING. SEAS WILL RANGE
BETWEEN 6 AND 9 FEET TONIGHT. WINDS SHOULD DROP BELOW ADVISORY
CRITERIA ON MONDAY NIGHT AND SPEEDS WILL SLOWLY FALL THROUGH THE
END OF NEXT WEEK.

IN ADDITION TO THE WINDS...WAVES AND ELEVATED TIDES...MARINE
REPORTS INDICATE  SOME LIGHT SEA FOG WITH VISIBILITIES BELOW 3
MILES IN A FEW LOCATIONS. STRONG WINDS SHOULD PROVIDE ENOUGH
MIXING TO LIMIT THE FOG THREAT AND MAINTAIN VSBY AOA 3 MILES. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      68  75  66  78  66 / 100 100  90  60  20 
HOUSTON (IAH)              70  77  67  77  67 /  90  90  90  70  30 
GALVESTON (GLS)            70  75  70  75  70 /  60  70  80  80  30 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...FLASH FLOOD WATCH THROUGH TUESDAY MORNING 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.

     COASTAL FLOOD WARNING UNTIL 1 PM CDT MONDAY FOR THE FOLLOWING 
     ZONES: BRAZORIA...CHAMBERS...GALVESTON...HARRIS...MATAGORDA.

GM...SMALL CRAFT ADVISORY UNTIL 7 AM CDT MONDAY FOR THE FOLLOWING 
     ZONES: GALVESTON BAY...MATAGORDA BAY.

     SMALL CRAFT ADVISORY UNTIL 11 AM CDT MONDAY 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...41
AVIATION/MARINE...45