FXUS64 KHGX 240411
AFDHGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1011 PM CST WED DEC 23 2009
.UPDATE...
NEW TORNADO WATCH IN EFFECT FOR ALL OF SOUTHEAST TEXAS BUT JACKSON
COUNTY.
&&
.DISCUSSION...
LL JET RIPPING THROUGH THE AREA AND VWP INDICATED A STRONGLY
SHEARED ENVIRONMENT IN PLACE. INSTABILITY HAS BEEN LACKING TO SOME
DEGREE AS INVERSION (PER CRP/ACARS SOUNDINGS) INDICATING ONLY A
THIN SLICE OF CAPE TO WORK WITH SO FAR. EVEN SO A FEW STORMS HAVE
BEEN PUTTING DOWN 1 TO 2 INCH PER HOUR RAINFALL RATES. RADAR
ESTIMATES OF 3 INCHES IN GRIMES/WALLER COUNTY.
RECENT STORMS ALSO EXHIBITING SOME ROTATION THOUGH SO FAR IT HAS
BEEN WEAK TO MODERATE. WILL BE KEEPING A CLOSE EYE ON STORMS
TRACKING THROUGH THE AREA. HELICITY VALUES OF 170-250 PREVAILING
OVER THE EASTERN 2/3RDS OF THE AREA.
NEXT WILL BE THE COLD FRONT TO SWEEP IN AFTER MIDNIGHT AND SHOULD
BE EXITING THE AREA 6-8 AM. HODOGRAPH MAY BECOME MORE LINEAR AND
WOULD EXPECT A LINE TO COME IN FROM THE SW AND AND FROM THE NW
MEETING UP OVER THE CENTRAL CWA FILLING IN OVER THE EASTERN HALF
OF THE AREA. SOME WIND DAMAGE POTENTIAL WITH LINEAR MCS/EMBEDDED
BOWING STRUCTURES.
HAVE ISSUED A WIND ADVISORY FOR THE CWA FOR 6A-6P THURSDAY AS
IMPRESSIVE WINDS ALOFT IN 925-850 LAYER SHOULD MIX DOWN DURING THE
DAY AND EXPECT SUSTAINED WINDS OF 20-25 KNOTS WITH GUSTS NEAR 35
KNOTS AT TIMES.
45/39
&&
.PREV DISCUSSION... /ISSUED 528 PM CST WED DEC 23 2009/
DISCUSSION...
00Z TAF DISCUSSION.
AVIATION...
MAIN THREATS WILL BE THE SEVERE WEATHER POTENTIAL MAINLY FOR
KCLL...KUTS AND KCXO. COLD FRONT EXPECTED TO PUSH THROUGH SE TX
AFTER MIDNIGHT TONIGHT WHICH MAY BRING A LINE OF STORMS THROUGH
THE REGION. LATEST THINKING FOR THE TAF AGREES WITH THE PREVIOUS
PACKAGE WITH TSRA AND GUSTY WINDS FROM 06Z TO 12Z THU. THERE MAY
BE SOME POST FRONTAL CLOUDINESS FOR THE LATE MORNING HOURS BUT
LIKELY AT VFR LEVELS. WINDS WILL BE QUITE GUST IN THE AFTERNOON
AS CLOUDS BEGIN TO LIFT AND WINDS MIX DOWN MORE.
39
PREV DISCUSSION... /ISSUED 337 PM CST WED DEC 23 2009/
AVIATION...
SCHEDULED AMENDMENTS FOR KIAH AND KHOU HAVE SOME CHANGES FROM THE
PREVIOUS PACKAGE. THERE WERE NO THUNDERSTORMS IN THE VICINITY BUT
DO EXPECT THE AREA OF STORMS BETWEEN KCLL AND KUTS TO POSSIBLY
BUILD SOUTHWARD TOWARD KIAH BY 22Z. ALSO EXPECT MORE WIDESPREAD
SHOWERS WITH ISOLATED THUNDERSTORMS AHEAD OF THE COLD FRONT THIS
EVENING. THE FRONT LOOKS TO WORK ITS WAY ACROSS BOTH TERMINAL
SITES EARLIER THAN PREVIOUSLY FORECASTED WITH THE HEAVIEST
ACTIVITY BETWEEN 06Z AND 10Z.
THE WEST WINDS WILL LIKELY GUST TO BETWEEN 20 AND 30 KNOTS
THURSDAY AFTERNOON. REFLECTED THIS ON THE KIAH TERMINAL FORECAST
BEGINNING AT 19Z.
40
PREV DISCUSSION... /ISSUED 249 PM CST WED DEC 23 2009/
DISCUSSION...
STRONG LLJ TRANSPORTING GULF MOISTURE INTO THE REGION. DAYTIME
HEATING AND SOME TEMPORARY PEEKS OF SUN HAVE ALLOWED SHRA/TSTMS TO
DEVELOP ACROSS THE AREA. THIS ROUND OF PRECIP SHOULD GRADUALLY
PUSH OFF TO THE E/NE THIS EVNG. IN THE MEANTIME...THERE IS
SUFFICIENT SHEAR AND UPPER DIFFLUENCE FOR A FEW DISCREET STRONG
TO SVR CELLS TO DEVELOP...WITH TORNADO'S AND WIND DMG THE PRIMARY
THREAT.
ATTENTION THEN TURNS TO THE WEST AS THE MAIN UPPER TROF APPROACHES
AND A BETTER SEVERE WX THREAT COMES INTO PLAY. EXPECT LARGE SCALE
LIFT TO INCREASE THRU THE NIGHT AND UPPER DIFFLUENCE TO BECOME
QUITE IMPRESSIVE AS LFQ OF THE JET NOSES INTO THE REGION. EXPECT
PRECIP IN WEST/CNTL TX TO EVENTUALLY CONSOLIDATE INTO A FAST
MOVING SQUALL LINE ALONG THE COLD FRONT THAT SHOULD BE MOVING WNW-
TO-ESE THRU THE REGION FROM ROUGHLY MIDNIGHT-6AM. PRIMARY THREAT
FROM THESE STORMS WILL BE STRONG WINDS. SHEAR IS STILL PRETTY GOOD
SO CANNOT RULE OUT ISOLATED TORNADO'S ALONG/AHEAD OF THE MAIN
SQUALL LINE. HAIL WILL ALSO BE POSSIBLE WITH STEEPENING LAPSE
RATES AS THE TROF APPROACHES.
MAY SEE SOME WRAP AROUND SHOWERS IN THE MORNING...GENERALLY ACROSS
NRN 1/2 OF THE CWA ON THURS...FOLLOWED BY DECREASING CLOUD COVER
LATER IN THE AFTN. LOTS OF WIND BEHIND THIS SYSTEM AND THERE'S A
GOOD CHANCE THE MIDNIGHT CREW WILL NEED TO ISSUE A WIND ADVSY FOR
PARTS OF SE TX. THOSE TRAVELING...ESP IN HIGH PROFILE VEHICLES
SHOULD BE PREPARED FOR A ROUGH RIDE ON NORTH-SOUTH ORIENTED ROADS.
HIGH PRES BUILDING IN WILL BRING IN COOL/COLD TEMPS WITH PORTIONS
OF THE REGION SEEING FREEZING OVERNIGHT LOWS FOR A COUPLE NIGHTS.
COASTAL LOW DEVELOPS OFF THE S TX OR NRN MEXICO COAST LATER IN THE
WEEKEND AND MOVES EAST - SHOULD NOT BE MUCH OF A FACTOR TO OUR WX.
ANOTHER SURGE OF HIGH PRES WILL FILL IN BEHIND THIS. NEXT CHANCE
OF RAINFALL ENTERS THE FCST TUE OR WED WHEN THE NEXT UPPER TROF
APPROACHES. ANOTHER COASTAL LOW FCST TO DEVELOP AHEAD OF THE
TROF...THIS TIME CLOSER TO THE MID/UPPER COAST. 47
MARINE...
WINDS HAVE BEEN STEADY OVER THE COASTAL WATERS TODAY. DO NOT EXPECT
MUCH CHANGE THROUGH THE LATE EVENING WITH AN ADVISORY 20 TO 60 NM
DUE TO WINDS AND SEAS AND A CAUTION WITHIN 20 NM. WINDS WILL PICK UP
OVER THE BAYS AND NEARSHORE WATERS AROUND MIDNIGHT ENOUGH FOR AN
ADVISORY. THE STRONG COLD FRONT IS EXPECTED TO MOVE THROUGH
MATAGORDA BAY AND THE COASTAL WATERS WEST OF FREEPORT OVERNIGHT...
AND THEN GALVESTON BAY AND THE AREAS TO THE EAST OF FREEPORT TOWARD
SUNRISE. THE COMPUTER MODELS INDICATE THAT WINDS BEHIND THE FRONT
MAY GUST TO GALE FORCE BY MID MORNING THURSDAY AND PERSIST INTO THE
EARLY EVENING.
HIGH PRESSURE WILL BRING A BREAK TO THE WINDS THURSDAY NIGHT THROUGH
EARLY IN THE WEEKEND. BY SATURDAY EVENING...MODERATE NORTHEASTERLY
WINDS WILL BE POSSIBLE AS LOW PRESSURE BEGINS TO FORM IN THE WEST
CENTRAL GULF OF MEXICO AND INTERACTS WITH HIGH PRESSURE NORTH OF THE
STATE. 40
&&
.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL) 50 51 30 50 31 / 80 40 0 0 10
HOUSTON (IAH) 52 56 33 52 33 / 80 50 0 0 10
GALVESTON (GLS) 61 58 40 52 43 / 80 50 0 0 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...WIND ADVISORY FROM 6 AM TO 6 PM CST THURSDAY FOR THE FOLLOWING
ZONES: AUSTIN...BRAZORIA...BRAZOS...BURLESON...CHAMBERS...
COLORADO...FORT BEND...GALVESTON...GRIMES...HARRIS...
HOUSTON...JACKSON...LIBERTY...MADISON...MATAGORDA...
MONTGOMERY...POLK...SAN JACINTO...TRINITY...WALKER...
WALLER...WASHINGTON...WHARTON.
GM...SMALL CRAFT ADVISORY FROM 3 AM TO 6 PM CST THURSDAY FOR THE
FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY.
SMALL CRAFT ADVISORY FROM 3 AM THURSDAY TO MIDNIGHT CST THURSDAY
NIGHT FOR THE FOLLOWING ZONES: WATERS FROM FREEPORT TO THE
MATAGORDA SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND
TO FREEPORT OUT 20 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 3 AM CST THURSDAY FOR
THE FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA
SHIP CHANNEL OUT 20 NM...WATERS FROM HIGH ISLAND TO
FREEPORT OUT 20 NM.
SMALL CRAFT ADVISORY UNTIL MIDNIGHT CST THURSDAY NIGHT FOR THE
FOLLOWING ZONES: WATERS FROM FREEPORT TO THE MATAGORDA SHIP
CHANNEL 20 NM TO 60 NM...WATERS FROM HIGH ISLAND TO
FREEPORT 20 TO 60 NM.
&&
$$
DISCUSSION...45
