Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 130920
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
420 AM CDT SUN APR 13 2014

.DISCUSSION...
SOUTHERLY WINDS CONTINUE TONIGHT AND EARLY SUNDAY MORNING WITH
MAINLY BKN/OVC MVFR CIGS. CLOUDS AND WINDS ARE KEEPING TEMPS IN
THE UPPER 60S FOR MOST AREAS. SFC COMPOSITE MAP FROM 05Z HAS
MOISTURE AXIS RIDING THROUGH SE TX UP INTO C OKLA. MAIN 850MB LLJ
AXIS STARTS OVER WESTERN HILL COUNTRY AND STRETCHES NE TOWARDS NE
OKLA. AT 300MB POLAR JET STARTING TO INCREASE OVER S ROCKIES INTO
SW KS. AT THE SFC...LOW PRESSURE CONTINUES TO DEEPEN IN THE SAME
VICINITY OF SW KS. DRYLINE STRETCHES SOUTHWARD THROUGH TX
PANHANDLE. ANALYSIS OF 500 MB HAS JET STREAK COMING ACROSS S
ROCKIES INTO THE BIG BEND OF TX. LOOKING AT 00Z SOUNDINGS AT
CRP/DRT...STRONG CAPPING FROM ELEVATED MIXED LAYER AT 850-800MB.
VERY STEEP LAPSE RATES WERE NOTED ABOVE THAT WITH MOIST BOUNDARY
LAYER UNDER THE CAP.

GIVEN ALL THIS...THINK THE EML CAPPING WILL HOLD FOR MOST OF THE
DAY. JET STREAK COMING FROM W TX WILL PLAY A BIG ROLE IN ERODING
CAP. RIGHT NOW BY 00Z MON...JET STREAK AT 300MB AND PVA AT 500MB
WITH MID LEVEL COOLING SHOULD ERODE CAP OVER N TX. MODELS KEEP SE
TX ON SUBSIDENT SIDE OF THE JET CIRCULATION BUT AREAS FROM KCLL TO
KLFK MAY JET BE ENOUGH UNDER THE JET THAT THE CAP COULD ERODE.
NAM/GFS/ECMWF ALL SHOW POSSIBLE THUNDERSTORM DEVELOPMENT AROUND
00Z TO 06Z WHICH PUSHES EAST INTO LA. DECIDED TO GO 40/50 POPS
MAINLY FOR THE NORTHERN FEW COUNTIES IN THE FORECAST AREA TO
ACCOUNT FOR THIS POSSIBILITY. SPC HAS SLIGHT RISK OF SEVERE STORMS
NORTH OF A CALDWELL...WILLIS...LIVINGSTON LINE. GIVEN THE CAP AND
JET CONFIGURATION...THIS LOOKS REASONABLE. INSTABILITY OF
1000-2000 J/KG...DEEP MOISTURE...LIFT FROM JET AND DEEP LAYER
SHEAR OF 50-60KTS SHOULD SUPPORT ORGANIZED CONVECTION FOR A FEW
STRONG/SEVERE STORMS IN THE EVENING IF EML CAPPING ERODES ENOUGH.
IT LOOKS LIKE THERE IS A SMALL WINDOW FROM 21Z TO 02Z MON THAT
THIS COULD HAPPEN.

THERE ALSO LOOKS TO BE A SECOND WINDOW FOR POSSIBLE STRONG/SEVERE
STORMS. MODELS ARE ALL IN GOOD AGREEMENT WITH THE EML CAP ERODING
DURING THE MORNING HOURS MONDAY AS A COLD FRONT PUSHES INTO THE
AREA. JET STREAK MOVES MOVER OVER SE TX WITH MORE ASCENT PRESENT.
THIS IS ALSO WHEN A SECOND SHORTWAVE TROUGH NOW OVER THE INTER-
MOUNTAIN WEST BEGINS TO DIG INTO N TX. THINK UPPER LEVEL FLOW AND
FRONTOGENTIC LIFT SHOULD BE PLENTY TO ERODE CAPPING. MODELS STILL
SHOW DECENT INSTABILITY AROUND 1500 J/KG IN THE MORNING UP AGAINST
THE FRONTAL BOUNDARY. SHEAR PARAMETERS WITH LINEAR FORCING
SUGGESTS THAT AN ORGANIZED LINE OF STORMS WILL BE POSSIBLE. MAY
GET A BOWING SEGMENT WITH A WIND THREAT. RIGHT NOW SPC HAS SLIGHT
RISK OF SEVERE EAST OF THE AREA. WOULD NOT BE SURPRISED IF PARTS
OF SE TX ARE ADDED TO FUTURE OUTLOOKS DEPENDING ON THE STORM
DEVELOPMENT AND EVOLUTION. AGAIN LOOKS LIKE HAIL/WIND WILL BE THE
MAIN SEVERE THREATS.

COLD FRONT SHOULD CLEAR THE AREA BY LATE MON AFTERNOON. TEMPS
SHOULD BE FALLING BEHIND THE FRONT FOR THE REST OF THE DAY. TEMPS
IN THE MORNING WILL LIKELY BE DAY TIME HIGH TEMPS WITH MONDAY LOW
TEMPS OCCURRING BEFORE MIDNIGHT ON MONDAY NIGHT. COLD ADVECTION
WILL BE QUITE STRONG THROUGH MONDAY NIGHT AS FREEZING LINE AT
850MB REACHES A KCLL/KUTS LINE BY 12Z TUE. MAX TEMPS ON TUE MAY
REACH THE MID 60S MOST AREAS AFTER LOW TEMPS IN THE 30S/40S. WED
MORNING COULD BE ANOTHER COLD MORNING WITH MIN TEMPS BACK IN THE
30S/40S AS SFC RIDGE AXIS BEGINS TO MOVE EAST.

EXTENDED FORECAST CONTINUES TO BE TROUBLESOME. GFS CONTINUES ITS
TREND OF BRINGING ANOTHER SHORTWAVE INTO THE PLAINS ON THUR. ECMWF
IS NOT AS AMPLIFIED OR STRONG WITH THE WAVE. BUT THE ECMWF DOES
SEEM TO BE TRENDING TOWARDS THE GFS SOLUTION. TRENDED THE FORECAST
CLOSER TO THE GFS FOR THUR/FRI AS SFC LOW IN THE PLAINS MOVES UP
THE MISS RIVER VALLEY. COLD FRONT WORKS INTO THE AREA FRI PER GFS
WHILE ECMWF SHOWS A MILD WIND SHIFT TO NE WINDS. WILL HAVE TO KEEP
AN EYE ON NEXT WEEKEND AS GFS/ECMWF BOTH BEGINING TO SHOW A
SIGNIFICANT RAIN EVENT IN TX ON NEXT SUNDAY.

39

&&

.MARINE...
MODERATE ONSHORE FLOW WILL CONTINUE AND WILL CONTINUE THE SCEC
THROUGH LATE AFTERNOON. A STRONG COLD FRONT WILL MOVE OFF THE
COAST EARLY MONDAY AFTERNOON BRINGING SHOWERS AND THUNDERSTORMS
ALONG WITH STRONG NORTH WINDS AND INCREASING SEAS. GUSTS TO GALE
FORCE WILL BE POSSIBLE IN THE NEARSHORE WATERS AND ARE LIKELY IN
THE OFFSHORE WATERS AND A GALE WATCH MAY NEED TO BE ISSUED LATER
TODAY. THE STRONG WINDS WILL ALSO DRIVE TIDE LEVELS BELOW NORMAL
AND A LOW WATER ADVISORY MAY BE NEEDED FOR THE BAYS LATE MONDAY.
38

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      82  62  69  34  63 /  50  40  60  10   0
HOUSTON (IAH)              81  71  72  40  65 /  30  30  60  10   0
GALVESTON (GLS)            77  70  70  46  64 /  20  30  60  20   0

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION THROUGH THIS EVENING FOR THE
     FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP
     CHANNEL 20 NM TO 60 NM...WATERS FROM FREEPORT TO THE
     MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND
     TO FREEPORT 20 TO 60 NM...WATERS FROM HIGH ISLAND TO
     FREEPORT OUT 20 NM.

&&

$$

DISCUSSION...39
AVIATION/MARINE...38



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