Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 270213
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
913 PM CDT TUE APR 26 2016

.DISCUSSION...
00Z SOUNDINGS SHOW A STOUT CAP IN PLACE AT CRP/LCH AND SHV. PW
VALUES ARE UP TO 1.59 AT CRP AND 1.20 AT LCH AND SHV. CAPE VALUES
ARE BETWEEN 3000-4000 J/KG AND LAPSE RATES ABOVE THE CAPPING
INVERSION LOOK STEEP. AT 850 MB...A STRONG LLJ WAS ORIENTED FROM
DEEP SOUTH TEXAS INTO CENTRAL OKLAHOMA WITH DEEP 850 MB MSTR
EXTENDING ACROSS THE EASTERN HALF OF TX/OK. AN 850 MB TROUGH AXIS
EXTENDED N-S ACROSS WEST TEXAS. 700 MB TEMPS WERE 12C AT CRP AND
A FAIRLY WARM 700MB LAYER IS IN PLACE SOUTH OF I-10. AT 300
MB...WINDS WERE STRONGLY DIVERGENT ACROSS THE NORTHERN HALF OF THE
STATE BUT WINDS ALOFT LOOK SOME WHAT ZONAL OVER THE SOUTHERN HALF
OF THE STATE.

THE RAP...TEXAS TECH WRF AND HRRR ALL WANT TO BREAK THE CAP
OVERNIGHT AND BRING A LINE OF SHRA/TSRA THROUGH THE REGION BETWEEN
08-14Z WHILE THE GFS AND NAM12 MAINTAIN THE CAP AND WEAKEN THE
PRECIP PRIOR TO REACHING THE HOUSTON AREA. MODELS ARE SENDING
MIXED SIGNALS BUT THE STORMS OUT WEST ARE MOVING AT A PRETTY GOOD
CLIP (35-40 KTS) AND THE RAP/HRRR/WRF ALL INITIALIZED WELL SO WILL
LEAN TOWARD THE MORE AGGRESSIVE SHORT TERM GUIDANCE. HAVE RAISED
POPS A LITTLE OVER THE CENTRAL ZONES AND BROUGHT SEVERE WORDING
JUST A TAD FURTHER SOUTH (INTO HOUSTON). THE LINE OF STORMS SHOULD
ARRIVE AT KCLL AROUND 4 AM...HOUSTON AROUND 6 AM AND GALVESTON
AROUND 8 AM. STILL SOME UNCERTAINTY WITH REGARD TO THE CAP
STRENGTH AND IF THE CAP HOLDS...THE AREA WILL PROBABLY JUST GET A
FEW SHOWERS. A SPECIAL SOUNDING WILL BE LAUNCHED AT COLLEGE
STATION LATER TONIGHT AND HOPEFULLY WILL PROVIDE A FEW CLUES ON
CAP STRENGTH AND INSTABILITY.

MADE SOME SMALL CHANGES TO THE MARINE AREAS. ISSUED A SMALL CRAFT
ADVISORY FOR GLS BAY AND THE GULF WATERS. THE GRADIENT REMAINS
TIGHT AND GENERALLY THE WINDS BEGIN TO INCREASE IN ADVANCE OF A
NOCTURNAL MCS. ALREADY SEEING SIGNS OF INCREASING WINDS AT KGLS.
THE ADVISORY WILL EXPIRE AT 14Z WED MORNING. 43

43

&&

.PREV DISCUSSION... /ISSUED 646 PM CDT TUE APR 26 2016/

AVIATION...
BIT OF A TIGHT PRESSURE GRADIENT HAS KEPT WINDS UP OVER MOST OF
THE TERMINALS LATE THIS AFTERNOON. EXPECT MOST WILL LOSE THE GUST
CHARACTERISTIC BY AROUND 03Z. FAIRLY LARGE CAPPING INVERSION
OVERHEAD WHICH WILL LIKELY HELP IN THE FORMATION OF MVFR
CONDITIONS BETWEEN 02Z AND 06Z. SOME LOCATIONS MAY EXPERIENCE IFR
CONDITIONS. A MODEL CONSENSUS PUSHES A FRONTAL BOUNDARY INTO SE TX
OVERNIGHT TONIGHT AND WEDNESDAY MORNING. A PREFRONTAL TROUGH/DRY
LINE WILL SWING THE WINDS AROUND FROM THE SOUTHEAST TO THE SOUTH.
THE HIGH RESOLUTION MODELS HAVE A LINE OF SHOWERS AND
THUNDERSTORMS ALONG THE PREFRONTAL TROUGH. THE HIGH RESOLUTION
MODELS HAVE BETTER SHOWER AND THUNDERSTORM CHANCES FROM KCLL AND
KUTS SOUTH TO ABOUT KIAH. THUNDER CHANCES LOOK MUCH LOWER AT KLBX
AND KGLS.

SOUTHWEST WINDS WILL FOLLOW THE PASSAGE OF THE FRONT. IT IS LIKELY
THAT THE FRONT WILL NOT MAKE IT PAST HOUSTON BEFORE RETURNING BACK
INLAND WEDNESDAY AFTERNOON.

40

PREV DISCUSSION... /ISSUED 400 PM CDT TUE APR 26 2016/

DISCUSSION...
FAIRLY QUIET WX ACROSS SE TX SO FAR THIS AFTN BUT EXPECTING THIS
TO CHANGE OVERNIGHT. THE STRONG UPPER LEVEL STORM SYSTEM DEEPENING
OVER THE WESTERN PLAINS WILL PRODUCE A LINE OF STRONG/SEVERE OVER
NORTH CENTRAL TX THIS EVENING. THIS LINE IS FCST TO MOVE E/SE
DURING THE OVERNIGHT HRS...LIKELY REACHING THE NW PORTIONS OF THE
CWA AFTER MIDNIGHT. WHILE THERE IS ENOUGH MOISTURE/INSTABILITY
ALONG WITH FAVORABLE WINDS ALOFT TO SUSTAIN THIS ACTIVITY AS IT
MOVES INTO SE TX...THERE IS STILL CONCERNS WITH CAP STRENGTH.
HOWEVER WILL GO AHEAD AND ADD THE MENTION OF SEVERE WX FOR THESE
AREAS OVERNIGHT. LOCALLY HEAVY RAIN ALSO POSSIBLE BUT CELLS WILL
BE MOVING SO EXPECTED RAIN TOTALS OVERNIGHT WILL AVG FROM 1/2 TO 2
INCHES.

CONDITIONS WILL BE IMPROVING FROM THE WEST BY WEDS AFTN WITH THE
SYSTEM MOVING FURTHER E/NE. A BIT OF A BREAK THEN UNTIL FRI WITH
THE UPPER FLOW GOING ZONAL BRIEFLY. THAT BEING SAID...WILL LEAVE
SOME ISO POPS FOR THUR AFTN MAINLY ALONG THE COAST/CENTRAL ZONES
IN DEFERENCE TO THE SEABREEZE. OTHERWISE RAIN CHCS RETURN TO THE
FCST FRI (IN RESPONSE TO THE NEXT UPPER TROF/LOW DIGGING AOA THE
FOUR CORNERS). STRONG SHORTWAVE ROTATING AROUND THE BASE OF THIS
SYSTEM PROGGED TO PRODUCE WIDESPREAD SHOWERS/STORMS FOR BOTH FRI
AND SAT. FCSTS OF HIGH PWS (1.8"-2") AND STRONG DIFFLUENCE ALOFT
POINTING TO THE POSSIBILITY OF HEAVY RAIN/FLOODING FOR THIS TIME
FRAME. WILL HAVE TO SEE IF LATER RUNS KEEP RUNNING WITH THIS. 41

MARINE...
MODERATE AND OCCASIONALLY STRONG ONSHORE WINDS WILL CONTINUE THIS
WEEK...PRIMARILY OVER NIGHT AT STRONGER WINDS MIX DOWN TO THE
SURFACE. THERE WILL LIKELY BE INTERMITTENT PERIODS WHERE CAUTION
AND/OR ADVISORY FLAGS WILL BE REQUIRED. THIS WILL BE ESPECIALLY TRUE
LATER IN THE WEEK AS THE PRESSURE GRADIENT FURTHER TIGHTENS AND THE
FETCH LENGTHENS IN TO THE SOUTHEASTERN GULF. CORRESPONDING WIND
SPEEDS AND SEAS WILL SEE A FURTHER UPWARD BUMP GOING INTO THE
WEEKEND.

A SERIES OF UPPER LEVEL DISTURBANCES WILL BRING A CHANCE OF SHOWERS
AND THUNDERSTORMS ON WEDNESDAY MORNING...FRIDAY AND SATURDAY.

44

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      69  87  67  87  70 /  70  30  10  20  30
HOUSTON (IAH)              72  85  71  87  73 /  60  50  10  20  20
GALVESTON (GLS)            73  80  74  83  73 /  20  50  20  10  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 6 AM CDT WEDNESDAY FOR
     THE FOLLOWING ZONES: MATAGORDA BAY.

     SMALL CRAFT ADVISORY UNTIL 6 AM CDT WEDNESDAY FOR THE FOLLOWING
     ZONES: GALVESTON BAY.

     SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 10 PM CDT THIS EVENING
     FOR THE FOLLOWING ZONES: GALVESTON BAY...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.

     SMALL CRAFT ADVISORY UNTIL 9 AM CDT WEDNESDAY 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...43


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