Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 231131
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
631 AM CDT SAT AUG 23 2014

.DISCUSSION...
SEE THE 12Z AVIATION DISCUSSION BELOW.

40

&&

.AVIATION...
PATCHY GROUND FOG AND POSSIBLY SOME STRATUS MAY IMPACT SOME OF THE
MORE RURAL SITES BETWEEN 12Z AND 15Z. OTHERWISE...VFR IS EXPECTED
THROUGH THIS EVENING WITH A POSSIBLE RETURN OF PATCHY GROUND FOG
AT THE MORE RURAL SITES AFTER 09Z TONIGHT. THERE IS AN OUTSIDE
CHANCE FOR ISOLATED SHOWERS TO FORM ALONG A SEABREEZE MAINLY
DURING THE AFTERNOON PERIOD TODAY. THE LATEST HIGH RESOLUTION
MODELS ARE SUGGESTING A TIME FRAME OF ABOUT 17Z TO NEAR 00Z MAINLY
FROM THE COAST INTO THE METRO HOUSTON SITES.

40

&&

.PREV DISCUSSION... /ISSUED 402 AM CDT SAT AUG 23 2014/

DISCUSSION...
AT 08Z...WEAK HIGH PRESSURE WAS LOCATED OVER THE WEST CENTRAL GULF
AND A WEAK TROUGH OF LOW PRESSURE REMAINED OVER THE WESTERN HIGH
PLAINS. AT 850 MB...HIGH PRESSURE WAS NOTED OVER EASTERN LOUISIANA
AND LOW PRESSURE WAS LOCATED OVER THE INTERMOUNTAIN WEST WITH A
TROUGH EXTENDING SOUTH ALONG THE AZ/NM STATE LINE. 850 MB MOISTURE
WAS CONFINED TO COASTAL LOUISIANA AND 850 TEMPS HAD COOLED 2 C AT
LCH. AT 700 MB...HIGH PRESSURE WAS LOCATED OVER LOUISIANA WITH
VERY DRY CONDITIONS NOTED AT THIS LEVEL. AT 250 MB...A STRONG
UPPER LEVEL RIDGE EXTENDED FROM EASTERN MISSOURI TO EASTERN
GEORGIA. A WEAK UPPER LEVEL LOW WAS NOTED OVER NORTH CENTRAL
MEXICO AND ANOTHER WEAK LOW WAS LOCATED OVER THE TEXAS PANHANDLE.
UPPER FLOW OVER EAST TEXAS LOOKS CONFLUENT AT 00Z.

MODELS HAVE BEEN FORECASTING COOLER 850 TEMPS FOR TODAY AND THE
00Z COOLING AT LCH MAY PORTEND THIS DEVELOPMENT. ENSEMBLE GUIDANCE
STILL SUPPORTS VERY WARM TEMPERATURES TODAY AS DOES THE ECMWF
GUIDANCE. WILL CONTINUE TO FCST MAX TEMPS IN THE UPPER 90S
INLAND...LOWER 90S COAST. MID LEVELS REMAIN DRY AND SOME OF THIS
DRY AIR WILL AGAIN MIX TO THE SURFACE SO HEAT INDEX VALUES WILL
AGAIN REMAIN CLOSE TO THE ACTUAL AIR TEMPERATURE OVER THE WESTERN
ZONES. THE HEAT ADVISORY FOR THE COASTAL COUNTIES IS A BIT TENUOUS
AS DEW PTS ARE A BIT LOWER THAN PREV DAYS. NOT SURE THE 105 DEGREE
THRESHOLD WILL BE REACHED TODAY BUT WILL MAINTAIN THE HEAT
ADVISORY. PREFER NOT TO EXTEND AT THE ADVISORY INTO SUNDAY AT THIS
TIME AND WAIT AND SEE HOW MUCH DRY AIR MIXES TO THE SFC THIS AFTN.
CAN`T RULE OUT AN ISOLATED SHRA THIS AFTERNOON BUT PROBABILITIES
ARE VERY SMALL.

HIGH PRESSURE WILL REMAIN IN CONTROL THROUGH MONDAY WITH VERY WARM
TEMPERATURES AND DRY CONDITIONS. CONDITIONS WILL CHANGE QUICKLY
MONDAY NIGHT AS AN INVERTED UPPER TROUGH OVER THE GULF PUSHES WEST
TOWARD THE UPPER TEXAS COAST. THIS FEATURE WILL BRING A SURGE OF
FAIRLY DEEP TROPICAL MOISTURE INTO SE TX LATE MON NITE WITH THE
MOISTURE HANGING AROUND THROUGH FRIDAY. THE NAM IS PARTICULARLY
AGGRESSIVE WITH PW VALUES APPROACHING 2.40 INCHES BY 12Z TUESDAY.
AN UPPER LEVEL TROUGH MOVING SLOWLY ACROSS THE CENTRAL PLAINS
DURING THE MID-WEEK PERIOD WILL KEEP UNSETTLED WEATHER IN THE FCST
WITH MAINLY DIURNAL SHRA/TSRA EXPECTED TUESDAY THRU FRIDAY. WILL
CARRY CHANCE POPS THROUGH FRIDAY WITH CONVECTIVE TEMPS AROUND 90
AND PW VALUES AOA 2.00 INCHES. GLOBAL MODELS DIVERGE SIGNIFICANTLY
FRIDAY AND BEYOND. THE GFS BRINGS A FRONT THROUGH THE AREA WITH
SFC DEW POINTS FALLING INTO THE 50S AND PW VALUES DROPPING TO LESS
THAN AN INCH. THE GFS IS CONSIDERABLY FASTER WITH THE UPPER TROUGH
MOVING ACROSS THE CENTRAL PLAINS. THE ECMWF IS MUCH SLOWER WITH
THE TROUGH AND NEVER BRINGS THE FRONT THROUGH THE CWA. THE
CANADIAN IS ALSO SLOWER WITH THE TROUGH SO HAVE LEANED TOWARD THE
SLOWER SOLUTIONS. THE ECMWF KEEPS THE UPPER TROUGH/WEAKNESS ACROSS
THE SOUTHERN PLAINS THRU SUNDAY SO WILL KEEP RAIN CHANCES IN THE
FCST THRU NEXT WEEKEND. 43

MARINE...
HIGH PRESSURE OVER THE LOUISIANA COAST WILL DRIFT WESTWARD OVER THE
TEXAS COAST TODAY AND SUNDAY. THE MODELS DIFFER BY THE MIDDLE OF THE
UPCOMING WEEK. PREFERRED THE ECMWF OVER THE GFS AND KEPT ONSHORE
WINDS IN PLACE.

40

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      98  75  99  76 100 /  10  10  10  10  10
HOUSTON (IAH)              97  77  97  77  99 /  10  10  10  10  10
GALVESTON (GLS)            92  83  91  83  92 /  10  10  10  10  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR THE FOLLOWING
     ZONES: BRAZORIA...CHAMBERS...GALVESTON...JACKSON...
     MATAGORDA.
GM...NONE.

&&

$$

DISCUSSION...43
AVIATION/MARINE...40


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