Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 311144
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
644 AM CDT SUN AUG 31 2014

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

&&

.AVIATION...
BAND OF SHRA WITH A FEW ISOLATED TSRA EMBEDDED CONTINUES TO LIFT
SLOWLY NORTHWARD ALONG THE US 59 CORRIDOR. HI RES MODELS INDICATE
THIS ACTIVITY WILL CONTINUE TO SPREAD NORTHWARD THROUGH THE DAY
AND FILL IN FURTHER EAST. BEST COVERAGE AND TSRA CHANCES LOOK TO
REMAIN ALONG AND WEST OF INTERSTATE 45 WITH COVERAGE DIMINISHING
BY LATE AFTERNOON. LOW CLOUDS REDEVELOP AFTER MIDNIGHT WITH MVFR
CIGS POSSIBLE BY DAYBREAK ON MONDAY. 38

&&

.PREV DISCUSSION... /ISSUED 439 AM CDT SUN AUG 31 2014/

DISCUSSION...
ALTHOUGH THERE WAS PLENTY OF TROPICAL MOISTURE AND LIFT FROM AN
UPPER LEVEL TROUGH AXIS...THE MAJORITY OF CONVECTION FORMED IN THE
GULF OF MEXICO AND MOVED INTO E TX AND SW LA. LAKE CHARLES ENDED
UP WITH 7.87 INCHES OF RAIN FOR YESTERDAY. THERE IS A SIMILAR
ENVIRONMENT IN PLACE TODAY WITH TROPICAL MOISTURE STILL OVER MUCH
OF SE TX AND UPPER TX COAST. THE TROUGH AXIS IS SLOWLY WEAKENING
BUT STILL COULD BE A FOCUS FOR CONVECTIVE ACTIVITY. BOTH 00Z
LCH/CRP SOUNDINGS SHOWED 2.2 INCHES OF PRECIP WATER AND GOES
SOUNDER DATA ALSO DEPICTS A SWATH OF TROPICAL MOISTURE STRETCHING
SW TO NE ACROSS THE TX COAST. BASED ON WATER VAPOR IMAGERY TROUGH
AXIS SHOULD BE MOVING OUT OF THE AREA AS UPSTREAM SHORT WAVE
TROUGH MOVES ACROSS THE ROCKIES AND INTO THE PLAINS LATER
TODAY/TONIGHT. THIS SHOULD ALSO HELP ADVECT TROPICAL MOISTURE OVER
THE REGION THIS MORNING AND AFTERNOON. HI RES MODELS WRF-
ARW/RAP/HRRR DEVELOP CONVECTION ALONG THE UPPER TX COAST AND MOVE
IT INTO THE COASTAL COUNTIES AROUND 12Z THIS MORNING. RADAR
ALREADY SHOWING SOME SHOWER ACTIVITY FROM MATAGORDA BAY AND
OFFSHORE. THIS SEEMS TO BE MATCHING THE TRENDS IN THE SHORT RANGE
HI RES MODELS. THE NAM/GFS/ECMWF ALSO SUPPORT THE IDEA OF A SWATH
OF PRECIP EMBEDDED WITHIN MAIN TROPICAL MOISTURE AXIS. DECIDED TO
KEEP MENTION OF 60 POPS. AGAIN WITH THIS MUCH MOISTURE STRONGER
STORMS WILL BE CAPABLE OF 1-2 INCHES OF RAIN AN HOUR. ACCUMULATED
PRECIP TOTALS FROM 06Z HRRR SHOW SWATH OF 2-4 INCHES OF RAIN BY
21Z THIS AFTERNOON SO ISOLATED HIGHER AMOUNTS OF RAIN WILL BE
POSSIBLE. MODELS DO INDICATE RAINFALL COMING TO AN END LATE
AFTERNOON AND EVENING SO DECREASED RAIN CHANCES FOR THE AFTERNOON.

OVERALL MOISTURE TRENDS IN NAM/GFS KEEP NEARLY 2 INCHES OF PRECIP
WATER OVER THE TX COAST THROUGH THE MIDDLE OF THE WEEK. A TROPICAL
WAVE IN THE NW CARIBBEAN SHOULD BE MOVING ACROSS THE YUCATAN TODAY
AND TOMORROW. NHC GIVES THIS WAVE A 50 PERCENT CHANCE OF BECOMING
A TROPICAL CYCLONE OVER NEXT 5 DAYS. ITS BEST CHANCE TO DO SO PER
LATEST MODEL GUIDANCE WILL NOT BE UNTIL IT EMERGES IN THE GULF.
EVEN THEN ONLY THE NAM REALLY DEVELOPS THE SYSTEM INTO A CLOSED
CIRCULATION. THE GFS/ECMWF KEEP IT AS AN OPEN WAVE WHICH HAS BEEN
WAY MORE CONSISTENT THAN THE NAM. OVERALL IMPACT TO TX WILL BE TO
KEEP A FETCH OF DEEP MOISTURE OFF THE GULF IN PLACE. THIS SHOULD
ALLOW FOR DAILY RAIN CHANCES FOR THE NEXT WEEK WITH DAY TIME
HEATING DRIVING CONVECTIVE TRENDS. COVERAGE IN CONVECTION WILL BE
THE REAL ISSUE AS GLOBAL MODELS ESTABLISH A BROAD ELONGATED UPPER
LEVEL RIDGE OVER MUCH OF THE SOUTHERN U.S. THE STRENGTH OF THE
RIDGE IS ALSO A QUESTION SO DIFFICULT TO GAGE HOW MUCH SUBSIDENCE
WILL BE OCCURRING DUE TO THE RIDGE. WITH THESE FACTORS IN MIND THE
FORECAST WILL KEEP AT LEAST SOME MENTION OF THUNDERSTORMS EACH
DAY. IT LOOKS LIKE THE HIGHER RAIN CHANCES WILL BE TUE/WED AS THIS
IS WHEN TROPICAL MOISTURE FROM THE TROPICAL WAVE MAY IMPACT THE
AREA. FORECAST WILL GO WITH 30/40 POPS FOR THESE DAYS WITH 20 POPS
FOR THE REST OF THE WEEK.

TEMPERATURES FOR THE WEEK WILL BE ABOVE NORMAL BUT STILL THE MORE
TYPICAL SUMMER TIME TEMPERATURES. MIN TEMPS IN THE MID/UPPER 70S
WILL BE EXPECTED WITH MAX TEMPS IN THE LOW/MID 90S. TEMPS WILL BE
GREATLY INFLUENCED BY CONVECTION AND RESULTING CLOUD COVER. AS IT
STANDS...WITH 100F NOT EXPECTED FOR A HIGH TEMPERATURE AT KCLL OR
KIAH TODAY...THE STREAK OF NOT REACHING 100F FOR A HIGH
TEMPERATURE CONTINUES INTO SEPTEMBER. HOPEFULLY IT STAYS THAT WAY
FOR THE REST OF THE YEAR.

39

MARINE...
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP THIS
MORNING ACROSS THE COASTAL WATERS AS DEEP TROPICAL MOISTURE MOVES
BACK INTO THE REGION. EXPECT ONSHORE FLOW TO PERSIST THROUGH MUCH
OF THE UPCOMING WEEK. WIND SPEEDS WILL INCREASE LATE MONDAY NIGHT
INTO TUESDAY AND CAUTION FLAGS MAY BE NEEDED FOR THE COASTAL
WATERS. 38

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      94  76  95  76  95 /  20  10  20  10  20
HOUSTON (IAH)              91  77  93  77  93 /  40  10  30  20  30
GALVESTON (GLS)            88  81  89  82  89 /  60  10  30  30  40

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

DISCUSSION...39
AVIATION/MARINE...38



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