Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 310914
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
414 AM CDT FRI JUL 31 2015

.DISCUSSION...
OVERNIGHT CONVECTION OVER THE BRAZOS VALLEY CONTINUES TO
DIMINISH AS IT EXITS THE FORECAST AREA... WITH VERY WARM
TEMPERATURES PERSISTING ACROSS SOUTHEAST TEXAS EARLY THIS MORNING.
SURFACE ANALYSIS AT 05Z SHOWED A PLUME OF 75+ DEGREE DEW POINTS
DRAPED ALONG THE TEXAS COAST AND EXTENDING INTO NORTHEAST
LOUISIANA. THIS... COMBINED WITH LEFTOVER CLOUDS FROM LAST NIGHT/S
STORMS... WAS CONTRIBUTING TO HEAT INDICES IN THE LOW TO MID 90S
AS OF 3 AM CDT AT A FEW SITES. A WEAK FRONTAL BOUNDARY WAS ALSO
ANALYZED ON THIS MAP STRETCHING NORTH TEXAS AND ON INTO NORTHERN
LOUISIANA. THIS FRONT WILL PLAY A MAJOR ROLE IN HOW THE WEATHER
EVOLVES TODAY FOR THE REGION... BOTH IN TERMS OF THUNDERSTORM
CHANCES AS WELL AS CONCERNS ABOUT HEAT.

THE 00Z LAKE CHARLES SOUNDING REPORTED A PRECIPITABLE WATER VALUE
OF 2.26 INCHES... WITH OVERNIGHT GPS-MET MEASUREMENTS ACROSS THE
REGION SHOWING A SIMILARLY MOIST AIRMASS /2.1 TO 2.3 INCHES AROUND
THE HOUSTON METRO AND ALONG THE COAST/. HIGH RESOLUTION GUIDANCE
IS FAIRLY CONSISTENT WITH DEVELOPING SCATTERED SHOWERS AND
THUNDERSTORMS ALONG THE FRONT AS IT SLOWLY DROPS SOUTHWESTWARD
TODAY... BUT AGREEMENT IS POOR IN THE ACTUAL TIMING OF THIS
FEATURE AND CONSEQUENTLY THE LOCATION OF THE GREATEST AREAL
COVERAGE.

THE GFS APPEARS TO BE BY FAR THE MOST AGGRESSIVE AND SWEEPS
MOISTURE AWAY FROM THE INTERSTATE 45 CORRIDOR AND POINTS EAST BY
18Z. COMPARISON OF SURFACE THETA-E FIELDS HOWEVER /WHICH REPRESENT
MOISTURE AND INSTABILITY PRESENT/ REVEAL STABILIZATION FOR THE
EASTERN HALF OF THE REGION CLOSER TO 00Z... WITH RELATIVELY GOOD
AGREEMENT BETWEEN BOTH HIGHER RESOLUTION AND SYNOPTIC MODELS ON
THIS SOLUTION. BASED ON THIS... HIGHLIGHTING HIGHEST RAIN CHANCES
WEST OF THE INTERSTATE 45 CORRIDOR TODAY ALONG AND AHEAD OF THE
ANTICIPATED FRONTAL POSITION. ADDITIONALLY... A DRY SUB-CLOUD
LAYER AND DCAPE VALUES 1100-1300 J/KG THIS AFTERNOON RAISES
CONCERNS FOR AT LEAST AN ISOLATED GUSTY WIND THREAT FROM STRONGER
THUNDERSTORM ACTIVITY.

A LATER FRONTAL PASSAGE ALSO MEANS THAT STIFLING CONDITIONS WILL
PERSIST AHEAD OF THE FRONT TODAY AND HAVE GONE AHEAD AND ISSUED A
HEAT ADVISORY FOR THE COASTAL COUNTIES OF MATAGORDA... BRAZORIA...
GALVESTON... AND CHAMBERS. HEAT INDICES IN THESE AREAS REACHED 109
TO 111 DEGREES YESTERDAY. WITH THE ANTICIPATED SLOW PROGRESSION
OF THE FRONT TODAY COMBINED WITH NAEFS ANOMALIES HIGHLIGHTING
ANOMALOUS TEMPERATURES AGAIN ALONG THE COAST /A RETURN INTERVAL
OF APPROXIMATELY ONCE EVERY 10 YEARS/... WANTED TO HIGHLIGHT THE
INCREASED POTENTIAL FOR HEALTH IMPACTS. IF THE FRONT MOVES THROUGH
FASTER THAN ANTICIPATED HOWEVER... DRIER AIR FILTERING IN BEHIND
THE FRONT WILL ACTUALLY HELP LOWER HEAT INDEX VALUES AND ADVISORY
CRITERIA MAY NOT BE MET.

FOR THE REMAINDER OF THE SHORT TERM... THE FRONT IS EXPECTED TO
PUSH OFF THE COAST TONIGHT. DRIER AIR FILTERING IN BEHIND THE
FRONT WILL HELP LIMIT RAIN CHANCES OVER ALL BUT THE COASTAL WATERS
ON SATURDAY. THIS SLIGHTLY DRIER AIR MAY ALSO ALLOW FOR SOME
OVERNIGHT LOWS IN THE UPPER 60S IN THE PINEY WOODS REGION... WITH
LOW 70S TO NEAR 80 POSSIBLE ELSEWHERE. HIGH TEMPERATURES ARE NOT
EXPECTED TO DIFFER MUCH FROM TODAY ON SATURDAY BUT A DRIER AIRMASS
IN PLACE WILL HELP MITIGATE AGAINST HIGHER HEAT INDEX VALUES.

THE REGION WILL REMAIN ON THE EASTERN PERIPHERY OF THE UPPER RIDGE
ON SUNDAY AND THROUGH THE REST OF THE FORECAST PERIOD... WITH THE
CENTER OF THIS FEATURE SHIFTING A BIT AROUND THE SOUTHERN PLAINS
DURING THIS TIME. LOW THUNDERSTORM CHANCES WILL CONTINUE IN THE
VICINITY OF THE STALLED FRONTAL BOUNDARY WITH DRY CONDITIONS AND
ABOVE NORMAL TEMPERATURES INLAND PERSISTING INTO THE MIDDLE OF
NEXT WEEK.

HUFFMAN

&&

.MARINE...

STORMS HAVE DEPARTED THE WATERS BUT MORE COULD COMING LATE THIS
MORNING THROUGH EVENING. WINDS WILL GENERALLY BE VARIABLE NORTHERLY
TO EASTERLY ACROSS THE UPPER TEXAS COASTAL WATERS WITH AN AFTERNOON
SEABREEZE FORMING. EVENTUALLY A DIFFUSE COLD FRONT SAGS OUT INTO THE
GULF WATERS LATE TONIGHT AND WINDS INCREASE SLIGHTLY. 850MB FRONT
APPEARS TO STALL WELL OFFSHORE AND SHOULD BECOME A FOCUS FOR
REDEVELOPMENT OF SHOWERS AND THUNDERSTORMS BUT PROBABLY JUST SE OF THE
UPPER TEXAS COASTAL WATERS. WILL NEED TO KEEP AN EYE ON THE REMAINS
OF THE BOUNDARY SATURDAY AFTERNOON-SUNDAY AS THE GULF IS PLENTY WARM
ENOUGH AND SHEAR RELAXES. MOISTURE SURGES BACK INTO THE AREA LATE
SUNDAY AND SOUTH TO SOUTHEASTERLY FLOW RETURNS AND CONTINUES THROUGH
FRIDAY.
45

&&

.AVIATION...

VFR FOR NOW BUT MAY GET A FEW SPOTS WITH MIFG AROUND SUNRISE MAINLY
THE MORE RURAL SITES CXO NORTHWARD. CHALLENGING FORECAST FOR TODAY.
DRY AIR SHOULD INTRUDE INTO THE REGION FROM THE NORTHEAST BUT A FEW
OF THE MODELS APPEAR TOO QUICK TO DRY THINGS OUT. L/V WINDS WILL BE
THE NORTH UNTIL THE DIFFUSE FROPA. AM THINKING THAT CLL-HOU-SGR-LBX
MAY SEE SOME THUNDER CLOSE BY THIS AFTERNOON AND WILL LIKELY ADD
THIS IN THE 12Z PACKAGE IF NOT SOONER. IAH MAY BE ON THE NORTHERN
FRINGE OF WHERE POOLED MOISTURE AND SAGGING BOUNDARY INTERACT SO FOR
NOW WILL PROBABLY LEAVE VCTS OUT BUT IT WILL BE CLOSE. DEEP MIXING
AGAIN TODAY WITH LIGHT WINDS IN THE PROFILE SO STORMS SHOULD BE SLOW
MOVING. DRYING NORTHEASTERLY TO EASTERLY FLOW SHOULD OVERSPREAD
IAH/HOU BY LATE AFTERNOON/EARLY EVENING LEADING TO CLEAR SKIES.
45

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      98  73  98  74  99 /  30  10  10  10  10
HOUSTON (IAH)              98  74  98  75  99 /  20  10  10  10  10
GALVESTON (GLS)            95  80  94  81  92 /  30  10  10  10  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...HEAT ADVISORY FROM 1 PM THIS AFTERNOON TO 7 PM CDT THIS EVENING
     FOR THE FOLLOWING ZONES: BRAZORIA...CHAMBERS...GALVESTON...
     MATAGORDA.

GM...NONE.
&&

$$

DISCUSSION...14
AVIATION/MARINE...45


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