Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 182048
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
348 PM CDT THU SEP 18 2014

.DISCUSSION...
TODAY`S HIGHEST RAINFALL RATES OF NEAR 5 INCHES PER HOUR OCCURRED
OVER WESTERN AND SOUTHERN HARRIS...NORTHERN GALVESTON...NORTHERN
MONTGOMERY AND SOUTHERN SAN JACINTO COUNTIES. OF COURSE...MANY
LOW LYING AREAS/STREETS QUICKLY WENT UNDER WATER AS THIS RAIN
FELL ON AN ALREADY SATURATED / URBAN LANDSCAPE. AFTER ABOUT THREE
PLUS HOURS OF MERGING SLOW-MOVING TRAINING MODERATE/HEAVY RAIN
(ISOLATED THUNDERSTORMS) CLUSTERS...THERE WILL BE A SHORT LULL
ACROSS MANY OF THOSE AREAS. AS THESE COUNTIES SLOWLY DRAIN AND THE
ATMOSPHERE RE-CHARGES...THERE ARE NUMEROUS RAIN/STORM CELLS GATHERING
ALONG A WEAK CENTRAL TEXAS BOUNDARY AND THESE WILL LIKELY EXPAND
BACK TOWARDS THE EAST AND INITIATE A GOOD ROUND OF NORTHERN CWA
RAINFALL THROUGH THE LATE AFTERNOON INTO MID EVENING HOURS. A
SHORTWAVE DISTURBANCE DIVING DOWN INTO CENTRAL TEXAS WILL ENHANCE
THIS FAR INTERIOR ACTIVITY. NEAR ZERO STORM MOVEMENT WITHIN THIS
GREATER THAN 2.3 INCH PWAT AIR MASS EQUATES TO VARIOUS COMMUNITIES
DEALING WITH EXCESSIVE RAINFALL INTO THE OVERNIGHT HOURS. GRANTED...
THOSE FAR NORTHERN COUNTIES FROM BRAZOS EAST OVER INTO MADISON
AND HOUSTON COUNTIES HAVE NOT SEEN AS MUCH 24-48 RAINFALL AND THEIR
UPPER LEVEL SOIL LAYERS ARE NOT VERY SATURATED...BUT IF THE RAIN
RATES THAT OCCURRED IN HOUSTON AND SURROUNDING COUNTIES OCCURS...THEN
NORTHERN FA FLOODING WILL OCCUR. THIS NORTHERN ACTIVITY IS FORECAST
TO SLOWLY SAG SOUTHWARD OVERNIGHT AND MERGE WITH RE-DEVELOPING SOUTHERN
FORECAST (+)RA CLUSTERS FROM AS EARLY AS AROUND FRIDAY MIDNIGHT AND
PERSIST THROUGH THE EARLY AFTERNOON. NEEDLESS TO SAY...THE FLOOD WATCH
AS BEEN EXTENDED. BUFFALO BAYOU-DOWNTOWN HAS RECENTLY COME OUT OF
BANKS WITH RUN-OFF...A REMINDER THAT IT IS BEST TO KEEP ABREAST
OF THE LATEST HYDRO PRODUCTS FOR FUTURE UPDATES UPON LOCAL BAYOU
WATER LEVEL TRENDS.

ONCE THIS `CHAPTER` OF PRECIPITATION COMES TO AN END SOMETIME LATE
FRIDAY INTO EARLY SATURDAY MORNING...THE NEXT AREA TO MONITOR FOR
RETURN RAIN WILL BE CLOSER TO THE COAST AND POINTS SOUTHWESTWARD.
THE RECENT BETTER LOWER LEVEL CONVERGENCE OF OFFSHORE SOUTHEASTERLIES
RUNNING INTO INLAND EASTERLIES WILL TURN MORE UNI-DIRECTIONAL SOUTHEAST.
STILL HOLDING ONTO THE IDEA THAT A WEAK BACKDOOR FRONT WILL MOVE
IN FROM THE SABINE AND SHUNT THE HIGHER MOISTURE TOWARDS THE COASTAL
BEND SATURDAY MORNING. UPPER RIDGING IS FORECAST TO NEVER REALLY
GAIN A REAL FOOTHOLD OVER EASTERN TEXAS...WITH AN UNSETTLED NEAR-
COASTAL SCENARIO UNFOLDING WITHIN THE NWP SOLUTIONS. GENERALLY LOWER
HEIGHTS AND A VICINITY OFFHSORE INVERTED TROUGH FORMING IN THE
SURFACE PRESSURE FIELD...ALONG WITH RANDOM WAVES MOVING UP FROM
THE FAR OFFHSORE WATERS...ALL LEAN THE FORECAST TO LOW RAIN
CHANCES ACROSS THE SOUTHERN THIRD OF THE CWA THROUGH LATE SUNDAY.
SOUTHWESTERN U.S./NORTHERN MEXICO UPPER RIDGING IS FORECAST TO
EXPAND A BIT FURTHER EAST TO BEGIN THE NEXT WORK WEEK. THIS HAS
RAIN CHANCES FALLING TO JUST SLIGHT NEAR THE COAST...UNDER SLIGHT
INLAND. MONDAY THROUGH FRIDAY RAIN CHANCES WILL REMAIN SLIGHT TO
LOW CHANCE ALONG THE COAST AND GULF THROUGH THE REMAINDER OF THE
PERIOD BASED UPON THE UNSETTLED NATURE OF THE GULF`S OVERLYING
ATMOSPHERE...THE 20 TO 40 POPS ISOPLETHES WILL MIGRATE INLAND
EACH DAY PAST MID-WEEK DUE TO INTERIOR WARMING INTO THE UPPER
80S...SURPASSING PROGGED LOW-MID 80F CONVECTIVE TEMPERATURES. 31

&&

.MARINE...
LOW PRESSURE OVER NORTHER MEXICO WILL PRODUCE A SOUTHEAST WIND
TONIGHT. HIGH PRESSURE TO THE NORTH OF TEXAS AND WEAK LOW PRESSURE
OVER NORTHERN MEXICO WILL ALLOW AN EAST WIND TO DEVELOP ON FRIDAY
AND PERSIST THROUGH EARLY NEXT WEEK. WEEKEND MARINERS CAN EXPECT
SLIGHTLY ELEVATED SEA HEIGHTS DUE TO THE PROLONGED EASTERLY FETCH.
WINDS SHOULD SLOWLY DECREASE ON MONDAY AS THE PRESSURE GRADIENT
BEGINS TO RELAX. A COLD FRONT WILL APPROACH SE TX ON TUESDAY BUT
WILL PROBABLY STALL NORTH OF THE COASTAL WATERS. EAST WINDS WILL
PERSIST THROUGH FRIDAY AND GRADUALLY STRENGTHEN TOWARD THE END OF
THE WEEK AS THE PRESSURE GRADIENT. A PERSISTENT EASTERLY FETCH WILL
ALLOW TIDE LEVELS TO SLOWLY INCREASE THROUGH THE WEEK. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      73  88  71  91  73 /  70  50  20  30  20
HOUSTON (IAH)              75  86  72  90  74 /  60  70  20  30  20
GALVESTON (GLS)            77  86  79  88  79 /  60  60  30  30  30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...FLOOD WATCH UNTIL MIDNIGHT CDT TONIGHT FOR THE FOLLOWING ZONES:
     BRAZOS...BURLESON...GRIMES...HOUSTON...MADISON...POLK...
     TRINITY...WALKER...WASHINGTON.

     FLOOD WATCH THROUGH FRIDAY MORNING FOR THE FOLLOWING ZONES:
     AUSTIN...BRAZORIA...CHAMBERS...COLORADO...FORT BEND...
     GALVESTON...HARRIS...JACKSON...LIBERTY...MATAGORDA...
     MONTGOMERY...SAN JACINTO...WALLER...WHARTON.

GM...NONE.
&&

$$

DISCUSSION...31/43



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