Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 220446
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1146 PM CDT THU MAY 21 2015

.DISCUSSION...
06Z TAF DISCUSSION IN AVIATION SECTION...

&&

.AVIATION...
NOT A LOT OF CHANGE FROM THE 00Z TAFS FOR 06Z. OVERALL TRENDS LOOK
LIKE THEY ARE ON TRACK BUT NOT SEEING WIDE SPREAD IFR EXCEPT AT
KCLL/KUTS. THINK THIS MAY FILL IN OVER KCXO AND HOUSTON TERMINALS
LATER TONIGHT AS MORE SATURATION OCCURS WITH IN MOIST BOUNDARY
LAYER. OTHERWISE MVFR CIGS WILL LIKELY PREVAIL. REST OF THE
FORECAST LOOK GOOD BASED OFF LATEST 00Z WRF GUIDANCE AND LATEST
HRRR/RAP GUIDANCE.

39

&&

.PREV DISCUSSION... /ISSUED 939 PM CDT THU MAY 21 2015/

DISCUSSION...
UPDATED THE FORECAST THIS EVENING TO LOWER INLAND TEMPERATURES AND
DEW POINTS BASED ON EVENING OBSERVATIONS. ALSO LOWERED RAIN CHANCES
FOR THE REMAINDER OF THE EVENING TO 20% IN CASE A STRAY SHOWER OR
TWO POPS UP. THE REST OF THE FORECAST WAS LEFT UNTOUCHED.

FLASH FLOOD WATCHES ARE BEING ISSUED FOR THE LONG HOLIDAY WEEKEND
TO OUR NORTH...AND THERE IS A CHANCE THAT MORE WATCHES WILL GO UP
OVER THE NEXT COUPLE OF DAYS ACROSS THE STATE. ANYONE WITH TRAVEL
PLANS OVER THE WEEKEND...ESPECIALLY TO OUR NORTH AND WEST...IS URGED
TO KEEP A CLOSE EYE ON THE WEATHER FORECASTS ALONG THEIR TRAVEL ROUTE.
42

PREV DISCUSSION... /ISSUED 639 PM CDT THU MAY 21 2015/

DISCUSSION...
00Z TAF DISCUSSION IN AVIATION SECTION.

AVIATION...
FRONTAL BOUNDARY HAS PUSHED JUST OFF THE UPPER TX COAST WITH
MAINLY NE WINDS FOR AREA TERMINALS. CIGS VARY FROM VFR TO IFR FOR
KCLL/KUTS. FRONTAL BOUDNARY WILL MAKE FORECASTING CIGS QUITE A
CHALLENGE. BOUNDARY LAYER WILL BE QUITE MOIST WITH LIGHT NE/E
WINDS SO LOOK FOR MVFR CIGS AND POSSIBLY IFR CIGS OVERNIGHT. MOST
AREAS HAVE PREVAILING MVFR WITH TEMP IFR CONDITIONS. SUSPECT THERE
WILL BE SOME AMMENDMENTS TO BETTER CAPTURE THE ONSET OF IFR WHILE
TRACKING SATELLITE/OBS.

TOMORROW FRONTAL BOUNDARY IS EXPECTED TO MOVE BACK NORTH AND
BECOME ORIENTED SE TO NW ACROSS THE AREA. QUESTION WILL BE HOW
MUCH RECOVERY OCCURS ALONG AND SOUTH OF THE BOUNDARY FOR
CONVECTION. STABLE AIR MAY HOLD ON FOR KCLL/KUTS/KCXO BASED ON
LATEST RAP/NAM/GFS BUT IT WILL BE CLOSE. THINK HOUSTON TERMINALS
SOUTHWARD COULD GET WARM SECTOR AIRMASS BACK SO MENTION VCTS IN
THE AFTERNOON FOR THUNDERSTORM THREAT. OVERALL THE MODELS ARE NOT
PRODUCING MUCH CONVECTION BUT WITH SOME HEATING IF CEILINGS BREAK
OUT IN THE AFTERNOON...IT WILL NOT TAKE MUCH TO GET CONVECTION.

39

PREV DISCUSSION... /ISSUED 333 PM CDT THU MAY 21 2015/

DISCUSSION...
AT 2 PM...A PRE-FRONTAL TROUGH OR PERHAPS AN OUTFLOW BOUNDARY
EXTENDED ALONG THE COAST WHILE THE COLD FRONT LINGERED BEHIND
EXTENDING FROM ABOUT CLEVELAND TO EAGLE LAKE TO NORTH OF VICTORIA.
THE FRONT WILL PUSH A BIT FURTHER SOUTH AND STALL NEAR THE COAST.
A WEAK UPPER LEVEL DISTURBANCE COUPLED WITH THE BOUNDARY ON FRIDAY
MORNING WILL YIELD SCATTERED SHRA/TSRA FRI OVER THE WESTERN HALF
OF THE CWA. PW VALUES ON FRIDAY WILL INCREASE TO 1.90 INCHES AND
CONVECTIVE TEMPS WILL BE AROUND 81 DEGREES SO SCT SHRA/TSRA WILL
DEVELOP AREAWIDE DURING THE LATE MORNING/EARLY AFTN. PW VALUES
NEAR 1.80 INCHES ON SATURDAY AND CONVECTIVE TEMPS IN THE LOWER 80S
SUGGEST MORE SCT PRECIP ON SATURDAY BUT THE FCST SOUNDINGS SHOW
MORE DRY AIR IN THE 850-700 MB LAYER. WILL CONTINUE WITH 30/40
POPS BUT SATURDAY MIGHT BE THE DRIEST DAY OUT OF THE NEXT SEVERAL
DAYS.

CONDITIONS DETERIORATE SUNDAY AS PW VALUES INCREASE TO 2.00 INCHES
AND JET DYNAMICS IMPROVE. FCST SOUNDINGS ON SUNDAY AFTN SHOW A
SATURATED PROFILE WITH PW VALUES ABOVE 2 INCHES. SE TX WILL LIE IN
A RIGHT REAR QUAD AS AN UPPER LEVEL TROUGH OVER THE DESERT SW
INCHES EASTWARD. THE DYNAMICS ARE MOST IMPRESSIVE SUNDAY NIGHT
INTO MONDAY. THE UPPER TROUGH EDGES EVER CLOSER AND THE THE
SUBTROPICAL JET SPLITS OVER EAST TEXAS. THE LOW LEVEL JET WILL
INCREASE TO 40-45 KNOTS AS WELL. ALL THE INGREDIENTS FOR A HEAVY
RAIN EVENT APPEAR TO BE IN PLACE.THE QPF OUTPUT FROM BOTH THE
GEM/ECMWF SUPPORT RAINFALL TOTALS IN EXCESS OF 5 INCHES. WITH ALL
THE RAIN THE AREA HAS RECEIVED OVER THE LAST 30 DAYS...RAINFALL OF
THIS MAGNITUDE WILL CREATE SIGNIFICANT FLOODING ISSUES. A FLASH
FLOOD WATCH WILL LIKELY BE REQUIRED SUN/MON. THE UPPER TROUGH AXIS
DOES NOT MOVE EAST UNTIL TUESDAY MORNING SO PERIODS OF SHRA/TSRA
WILL CONTINUE ON MONDAY. A SERIES OF WEAK S/WVS WILL MOVE ACROSS
THE STATE THROUGH THE END OF THE WEEK KEEPING CONDITIONS UNSETTLED
WITH SCATTERED SHRA/TSRA. 43

MARINE... WINDS ARE FROM THE SOUTHEAST AT 6 TO 8 KNOTS WITH SEAS
RUNNING 2 TO 3 FEET IN ADVANCE OF A WEAK COLD FRONT THAT IS DRAPED
ALONG THE COASTAL COUNTIES.  THUNDERSTORMS WILL EXTEND OVER THE BAYS
AND NEARSHORE WATERS LATER THIS AFTERNOON AS THE FRONT SAGS OFF THE
COAST.

THE FRONTAL BOUNDARY WILL WASH OUT ON FRIDAY AS IT LIFTS BACK SLOWLY
NORTHWARD AS A WARM FRONT. THE SURFACE PRESSURE GRADIENT WILL
TIGHTEN IN ADVANCE OF AN UPPER LEVEL TROUGH THAT WILL DIG IN TO WEST
TEXAS LATE THIS WEEKEND.  ONSHORE WINDS WINDS WILL BEGIN TO INCREASE
FRIDAY AND WILL VERY LIKELY WARRANT SCEC/SCA SATURDAY AND SCA
SATURDAY NIGHT-MONDAY.

MARINERS SHOULD EXPECT SUSTAINED WINDS AROUND 20 KNOTS WITH 7-8 FOOT
SEAS SUNDAY AND MONDAY. WIND GUSTS WILL BE IN THE 25 TO 30 KNOT
RANGE.  THE PERSISTENT SE FLOW AND SWELL FETCH POINT TO ELEVATED
TIDES AND STRONG RIP CURRENTS OVER THE HOLIDAY WEEKEND. 44

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      65  81  70  83  71 /  20  40  30  40  40
HOUSTON (IAH)              70  83  72  84  74 /  20  30  30  30  30
GALVESTON (GLS)            75  80  77  81  78 /  20  30  30  20  30

&&

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

$$

DISCUSSION...42
AVIATION/MARINE...39


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