Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 051128
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
628 AM CDT WED AUG 5 2015

.DISCUSSION...
SEE 12Z AVIATION DISCUSSION.

&&

.AVIATION...
NAM 12 AND THE GFS NOT IN THE BEST AGREEMENT AGAIN THIS MORNING.
THE NAM 12 HAS PW VALUES SURGING TO 2.3 INCHES THIS AFTN WHILE THE
GFS IS AROUND 1.90 INCHES. THE LATEST HRRR SEEMS TO SUPPORT THE
NAM SO LEANED IN THAT DIRECTION. HAVE ADDED VCSH FOR SOUTHERN TAF
SITES INCLUDING KIAH. PRECIP SHOULD END BETWEEN 23-01Z. VFR CONDS
EXPECTED TODAY AND TONIGHT OUTSIDE OF ANY CONVECTION. 43

&&

.PREV DISCUSSION... /ISSUED 400 AM CDT WED AUG 5 2015/

DISCUSSION...
EARLY MORNING WATER VAPOR IMAGERY DEPICTS A COMPACT SHORTWAVE
TROUGH MOVING ACROSS THE CENTRAL PLAINS... WITH BROAD RIDGING IN
PLACE OVER THE SOUTHWESTERN CONUS AND TROUGHING ACROSS THE EAST.
THE EXTREMELY MOIST AIRMASS THAT MOVED ACROSS THE REGION YESTERDAY
WAS SEEN PUSHING INTO NORTHEAST TEXAS PER GOES SOUNDER IMAGERY
THIS MORNING. PRECIPITABLE WATER VALUES ACROSS THE REGION RANGED
FROM 2-2.2 INCHES OVER CROCKETT/TRINITY/POLK COUNTIES TO 1.5
INCHES AROUND MATAGORDA BAY... WITH SLIGHTLY HIGHER PWATS AROUND
1.7 TO 1.9 INCHES JUST OFFSHORE.

FOR TODAY... SOUTHERLY WINDS WILL AGAIN ADVECT THE HIGHER
MOISTURE AIR OVER THE GULF INTO THE REGION. THIS WILL PROVIDE
ENOUGH MOISTURE FOR ISOLATED SHOWERS AND THUNDERSTORMS TO DEVELOP
ALONG THE SEA BREEZE AS IT PUSHES INLAND LATE MORNING THROUGH LATE
AFTERNOON. CARRYING THE HIGHEST CHANCES /20 POPS/ ALONG AND SOUTH
OF THE INTERSTATE 10 CORRIDOR... BUT CANNOT RULE OUT A STRAY CELL
OR TWO PUSHING NORTH OF THAT AREA. PEAK HEAT INDEX VALUES
YESTERDAY TOPPED OUT AT 108 AT GALVESTON AND WITH SIMILAR
TEMPERATURES AND LOW LEVEL MOISTURE IN PLACE ACROSS THE REGION
TODAY... ANTICIPATE HEAT INDEX VALUES TO BE NEAR YESTERDAY/S AND
AGAIN BELOW HEAT ADVISORY CRITERIA. HOWEVER... WILL BE ISSUING A
SPECIAL WEATHER STATEMENT TO HIGHLIGHT THE HEAT FOR THE REMAINDER
OF THE WEEK AND INTO THE WEEKEND.

LOSS OF DAYTIME HEATING WILL PREVENT SEA BREEZE SHOWER AND
THUNDERSTORM ACTIVITY FROM MAKING IT TOO FAR INTO THE EVENING
HOURS... BUT WILL NEED TO CONTINUE TO WATCH THE EVOLUTION OF THE
SHORTWAVE OVER THE CENTRAL PLAINS. THE NCEP 4 KM WRF ACTUALLY
BRINGS A THIN LINE OF THUNDERSTORMS TONIGHT INTO THE PINEY WOODS
REGION AS THIS SHORTWAVE DIVES TOWARDS THE LOWER MISSISSIPPI RIVER
TONIGHT. THIS MODEL IS INITIALIZED FROM THE 40 KM NAM... WHICH HAS
CONSISTENTLY BEEN AN OUTLIER WITH THE SOUTHERNMOST TRAJECTORY FOR
THIS SHORTWAVE OVER THE PAST FEW RUNS. 00Z GUIDANCE /INCLUDING THE
NAM/ DID NOT INITIALIZE TOO TERRIBLY WITH THE PLACEMENT OF THIS
SHORTWAVE. HOWEVER... GIVEN THAT THIS SOLUTION IS AN OUTLIER AND
THE MAJORITY OF GUIDANCE KEEPS THE SHORTWAVE TOO FAR NORTH OF THE
REGION TO RAISE ANY REAL CONCERNS FOR RAIN CHANCES THIS EVENING...
KEEPING THE FORECAST DRY FOR NOW. OTHERWISE... ANOTHER WARM AND
QUIET NIGHT EXPECTED FOR THE REGION.

THE UPPER RIDGE OVER THE SOUTHWESTERN CONUS WILL CONTINUE TO
SHIFT EASTWARD OVER THE NEXT 24 HOURS... CENTERING OVER EASTERN
NM/WEST TX ON THURSDAY. INCREASING HEIGHTS ALOFT WILL SERVE TO
INCREASE TEMPERATURES ACROSS THE REGION WITH HEAT ADVISORIES
POTENTIALLY NEEDED AS EARLY AS THURSDAY. BY THE WEEKEND... THE
UPPER RIDGE PARKS ITSELF OVER NORTH/NORTHEAST TEXAS AND PROLONGS
THE HEAT WITH INLAND TEMPERATURES RISING INTO THE LOW 100S THIS
WEEKEND. THOSE WITH OUTDOOR PLANS THIS WEEKEND WILL WANT TO TAKE
EXTREME CAUTION TO PREVENT HEAT ILLNESSES. LOOKING AHEAD TO NEXT
WEEK... MEDIUM RANGE GUIDANCE DOES ATTEMPT TO BRING A FRONTAL
SYSTEM OUT OF THE GREAT PLAINS WITH THE PROMISE FOR LOW RAIN
CHANCES BY THE MIDDLE OF NEXT WEEK.

HUFFMAN

MARINE...
HIGH PRESSURE OVER THE EASTERN GULF AND LOWER PRESSURE OVER THE
SOUTHERN PLAINS WILL MAINTAIN A LIGHT TO MODERATE ONSHORE FLOW
THROUGH THE WEEKEND. THERE WILL BE SUBTLE DIURNAL VARIATIONS WITH
SLIGHTLY STRONGER WINDS AT NIGHT AND A BRIEF S-SW COMPONENT TO THE
DIRECTION EACH MORNING. 43

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      99  77 100  78 101 /  10  10  10  10   0
HOUSTON (IAH)              97  79  98  80  99 /  20  10  10  10  10
GALVESTON (GLS)            92  82  91  82  92 /  10  10  10  10  10

&&

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

$$

DISCUSSION...14
AVIATION/MARINE...43



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