Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 041516
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1016 AM CDT TUE AUG 4 2015

.DISCUSSION...
A SURFACE TROUGH EXTENDED ACROSS THE NORTHWESTERN GULF TO NEAR
GALVESTON THIS MORNING. RADAR SHOWED THAT SHOWERS WERE TRYING TO
DEVELOP ALONG AND SOUTH OF A LINE FROM NEAR WHARTON TO
GALVESTON...HOWEVER SUBSIDENCE DUE TO THE UPPER LEVEL RIDGE WAS
APPEARING TO KEEP THE COVERAGE VERY ISOLATED. MODEL GUIDANCE
VARIED FOR COVERAGE THIS AFTERNOON...FROM ONLY AN ISOLATED SHOWER
OR STORM TO MORE SCATTERED COVERAGE. THE 12Z NAM12 CONTINUED ITS
TREND OF BRING ISOLATED TO SCATTERED COVERAGE CLOSE TO THE
NORTHERN COUNTIES LATE THIS AFTERNOON AND EARLY THIS EVENING.
THIS LOOKED TO BE DUE TO THE MODEL SHOWING A STRONGER SHORTWAVE
TROUGH ON THE NORTHERN SIDE OF THE RIDGE.

FOR NOW...THE CURRENT FORECAST LOOKS ON TRACK. WILL WATCH TRENDS
AND UPDATE LATER THIS MORNING OR INTO THE EARLY AFTERNOON IF
NECESSARY.

40

&&

.PREV DISCUSSION... /ISSUED 558 AM CDT TUE AUG 4 2015/

DISCUSSION...
SEE 12Z AVIATION DISCUSSION.

AVIATION...
MODELS (NAM12/GFS) SENDING A BIT OF A MIXED MESSAGE THIS MORNING
AS FCST SOUNDINGS SHOW PW VALUES EXCEEDING 2.10 INCHES AT KIAH
THIS AFTN BUT MODEL MASS FIELDS REMAIN BARE. THOUGHT THE RAP
INITIALIZED WELL AND HAVE LEANED TOWARD THE RAP TODAY. FEEL SHRA
WILL GENERALLY STAY OVER THE SOUTHERN TAF SITES AND IMPACT
KGLS...KLBX AND KHOU. VFR CONDS ARE EXPECTED TODAY AND MOST OF
TONIGHT WITH SOME BRIEF MVFR CIGS TOWARD SUNRISE WEDNESDAY. 43

PREV DISCUSSION... /ISSUED 408 AM CDT TUE AUG 4 2015/

DISCUSSION...
EARLY MORNING WATER VAPOR IMAGERY AND EVENING UPPER AIR ANALYSIS
SHOWED A FLATTENED UPPER RIDGE STRETCHING ACROSS THE SOUTHWESTERN
CONUS INTO TEXAS... WITH A COMPACT SHORTWAVE TROUGH MOVING ACROSS
CO/WY AND AN UPPER LOW OVER THE PACIFIC SPINNING ABOUT 800 MILES
OFF THE COAST OF NORTHERN CA. A PLUME OF VERY MOIST AIR
/PRECIPITABLE WATER VALUES OF 2.3 TO 2.5 INCHES/ WAS LOCATED OVER
WHARTON... JACKSON... AND MATAGORDA COUNTIES PER GOES SOUNDER
IMAGERY. A FEW EARLY MORNING SHOWERS HAD ALREADY BEGUN TO DEVELOP
AROUND MATAGORDA BAY WITHIN THIS MORE MOIST AIRMASS AND AT LEAST
ISOLATED SHOWERS WILL BE POSSIBLE SOUTH OF INTERSTATE 10 THROUGH
THE REMAINDER OF THE MORNING.

AS SOUTHERLY WINDS INCREASE TODAY... THIS MORE MOIST AIRMASS WILL
PUSH FARTHER INLAND. THIS... COMBINED WITH DAYTIME HEATING AND THE
SEA BREEZE... WILL KEEP THE CHANCE FOR ISOLATED SHOWERS AND
THUNDERSTORMS IN THE FORECAST THIS AFTERNOON AND EVENING MAINLY
ALONG AND SOUTH OF A COLUMBUS TO CLEVELAND LINE. CANNOT RULE OUT
AN ISOLATED STRONGER WIND GUST WITH THIS ACTIVITY AS DCAPE VALUES
APPROACH 1000 J/KG THIS AFTERNOON... BUT BRIEF HEAVY DOWNPOURS
APPEAR TO BE THE MOST LIKELY HAZARD GIVEN THE EXTREMELY MOIST
ENVIRONMENT. HIGH TEMPERATURES THIS AFTERNOON ARE EXPECTED TO TOP
OUT IN THE LOW 90S ALONG THE COAST... WITH MID TO UPPER 90S
FARTHER INLAND. HEAT INDEX VALUES MAY APPROACH OR SLIGHTLY EXCEED
105 DEGREES THIS AFTERNOON... BUT WILL CONTINUE TO INCREASE DURING
THE WEEK AS AFTERNOON TEMPERATURES RISE. ELEVATED LOW LEVEL
MOISTURE WILL PROMOTE A LIMITED COOLDOWN OVERNIGHT AS TEMPERATURES
ONLY FALL INTO THE MID 70S TO NEAR 80.

THE UPPER RIDGE WILL SHIFT EAST WEDNESDAY AS THE LOW OVER THE
PACIFIC APPROACHES THE WEST COAST. HIGH RESOLUTION GUIDANCE
BREAKS OUT A FEW SHOWERS FROM COASTAL CONVERGENCE ALONG THE COAST
WEDNESDAY MORNING AND AGAIN WEDNESDAY AFTERNOON ALONG THE SEA
BREEZE BUT ONLY HIGHLIGHTING THIS ACTIVITY WITH SILENT 10 POPS FOR
NOW DUE TO ANTICIPATED LOW COVERAGE. OTHERWISE... ANOTHER HOT DAY
EXPECTED WEDNESDAY WITH TEMPERATURES SIMILAR TO TODAY. HEAT INDEX
VALUES ARE EXPECTED TO REMAIN BELOW HEAT ADVISORY CRITERIA AGAIN
ON WEDNESDAY... BUT HEAT ADVISORY CRITERIA MAY BE MET AS EARLY AS
THURSDAY FOR PARTS OF THE AREA.

FOR THE REMAINDER OF THE FORECAST... HOT AND DRY IS PROBABLY THE
BEST WAY TO DESCRIBE THE SENSIBLE WEATHER PATTERN. THE UPPER RIDGE
BUILDING FARTHER EAST WILL ALLOW TEMPERATURES TO RISE INTO THE LOW
100S BY THE BEGINNING OF THE WEEKEND. MEDIUM RANGE GUIDANCE BUILDS
THE CENTER OF THE UPPER RIDGE OVER NORTH TEXAS AND INTO THE
ARKLATEX BY SATURDAY... WITH THIS FEATURE MAINTAINING CONTROL OVER
THE SOUTHERN PLAINS WELL INTO NEXT WEEK.

HUFFMAN

MARINE...
HIGH PRESSURE OVER THE EASTERN GULF WILL PRODUCE A SW-S WIND
TODAY. A WEAK BOUNDARY OVER THE GULF WILL SERVE AS A FOCUS FOR
SHOWERS AND ISOLATED THUNDERSTORMS OVER THE MARINE ZONES TODAY.
THE GRADIENT WILL BEGIN TO TIGHTEN WEDNESDAY AND WEDNESDAY NIGHT
AS LOW PRESSURE DEEPENS OVER THE SOUTHERN PLAINS. A LIGHT TO
OCCASIONALLY MODERATE ONSHORE FLOW WILL PERSIST THROUGH NEXT
WEEKEND. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      99  77  99  77  99 /  10  10  10  10  10
HOUSTON (IAH)              97  78  97  79  98 /  20  10  10  10  10
GALVESTON (GLS)            92  82  92  82  91 /  20  10  10  10  10

&&

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

$$

DISCUSSION...40
AVIATION/MARINE...41


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