Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 270334
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
934 PM CST FRI DEC 26 2014

.UPDATE...
SEE DISCUSSION FOR EVENING UPDATE.

&&

.DISCUSSION...
ONLY MINOR CHANGES TO THE FORECAST THIS EVENING. COLD FRONT IS NOW
PAST LUBBOCK AND IS FORECASTED TO BE AT COLLEGE STATION AROUND 9
AM TOMORROW MORNING. THE FRONT IS THEN FORECASTED TO BE AT HOUSTON
BETWEEN 2 AND 4 PM. A CONVERGENCE ZONE HAS SET UP THIS EVENING
RIGHT AROUND THE COAST UP INTO HARRIS AND LIBERTY COUNTIES. HIGH
RES MODELS HAVE STRUGGLED WITH THIS PRECIP. NEW RAP SEEMS TO BE
CATCHING ON WITH THE CURRENT TRENDS. GENERAL THINKING IS FOR THE
PRECIP TO PUSH TOWARDS THE NORTH AND EXPAND IN COVERAGE AHEAD OF
THE FRONT. NEW 0Z LCH SOUNDING HAS A PRETTY GOOD CAP AROUND 700 MB
SO EXPECT MOST PRECIP TO REMAIN THUNDER FREE OVERNIGHT. GFS AND
NAM SOUNDINGS ERODE THE CAP A BIT AND SUPPORT THUNDER FOR THE
AFTERNOON. BEHIND THE FRONT EXPECT TEMPERATURES TO FALL TOMORROW.
23

&&

.PREV DISCUSSION... /ISSUED 554 PM CST FRI DEC 26 2014/

DISCUSSION...
SEE THE 00Z AVIATION DISCUSSION BELOW.

40

AVIATION...
THE COLD FRONT WAS LOCATED LATE THIS AFTERNOON THROUGH THE PAN
HANDLE. THE LATEST NAM12 BROUGHT THE FRONT THROUGH KCLL AND KUTS
AROUND 13Z FRIDAY MORNING...BUT THEN SLOWS DOWN THE FRONTAL
MOVEMENT DRASTICALLY. IT THEN SHOULD MAKE ITS WAY THROUGH KCXO BY
20Z AND KIAH BY 00Z FRIDAY EVENING. CONDITIONS WILL BE MVFR
STARTING OUT THIS EVENING AND SHOULD LOWER TO IFR AHEAD OF THE
FRONT OVER THE NORTHERN SITES BY 10Z. THE FORECAST TO THE SOUTH
WAS A BIT TOUGHER REGARDING LOWERING BELOW MVFR. MODEL GUIDANCE
WAS VERY AGGRESSIVE IN EVEN GOING TO LIFR. DECIDED TO HOLD OFF
FOR NOW BUT THINK THERE IS A CHANCE IF THE FRONT SLOWS DOWN AS
ADVERTISED BY THE MODEL. SEA FOG MAY BECOME A PROBLEM TOWARD THE
COAST AS WELL SINCE THE DEWPOINTS WERE ALREADY IN THE MID 60S. AS
OF NOW THE FETCH OVER THE COOLER WATERS WAS FAIRLY SHORT. IF THE
WINDS SWITCH MORE TO THE EAST-SOUTHEAST...THE FETCH WILL LENGTHEN
AND SEA FOG MAY BECOME MORE OF A PROBLEM.

THE MODELS WERE ALSO HINTING AT A BREAK IN THE CONDITIONS BEHIND
THE FRONT AT KCLL AND KUTS...BUT THEN RETURN MVFR CONDITIONS BY
MIDDAY. THESE TYPE OF CONDITIONS DID NOT LOOKS VERY LIKELY FROM
KCXO SOUTHWARD BEHIND THE FRONT DUE TO ISENTROPIC LIFT BEHIND THE
FRONT.

40

PREV DISCUSSION... /ISSUED 342 PM CST FRI DEC 26 2014/

DISCUSSION...
AFTERNOON WATER VAPOR IMAGERY AT 3 PM DEPICTED THE NEXT TROUGH
APPROACHING THE REGION OVER THE FOUR CORNERS...WITH AN ASSOCIATED
COLD FRONT PUSHING THROUGH THE TEXAS PANHANDLE AND CENTRAL
OKLAHOMA. MOSTLY CLOUDY TO CLOUDY SKIES ACROSS THE AREA HAVE KEPT
TEMPERATURES GENERALLY IN THE MID 60S TO NEAR 70 THIS
AFTERNOON...AND THIS WARMTH IS SOMETHING WE LIKELY WON/T SEE FOR
THE REMAINDER OF 2014.

FOR TONIGHT... A PREFRONTAL TROUGH MOVING ACROSS SOUTHEAST TEXAS WILL
ALLOW WINDS TO SLACKEN ENOUGH TO ENABLE AT LEAST PATCHY FOG
DEVELOPMENT ACROSS THE AREA. SEA FOG WILL ALSO BE POSSIBLE OVER
THE COASTAL WATERS TONIGHT WITH HIGHER DEW POINT AIR ADVECTING
OVER COOLER SHELF WATERS /WATER TEMPERATURES NEAR 60 DEGREES/.
CONTINUED LIFT AND LOW LEVEL MOISTURE ADVECTION OVERSPREADING THE
REGION WILL PROMOTE AT LEAST INTERMITTENT LIGHT SHOWERS OR DRIZZLE
INTO THE OVERNIGHT HOURS...WITH OVERNIGHT LOWS BOTTOMING OUT IN
THE 60S.

AS THE UPPER TROUGH CONTINUES TO PUSH EAST ON SATURDAY... THE
FRONT MAKING ITS WAY THROUGH THE LONE STAR STATE WILL MOVE INTO
SOUTHEAST TEXAS. ROUGHLY TIMED...THE FRONT WILL REACH COLLEGE
STATION AROUND 8-10 AM... THE HOUSTON METRO 2-4 PM... AND
GALVESTON AROUND 6-8 PM. TEMPERATURES WILL FALL BEHIND THE
FRONT...SO NORTHERN AREAS WILL SEE THEIR HIGHS IN THE MORNING
WHILE SOUTHERN AREAS LOOK TO REALIZE THEIR HIGH TEMPERATURES IN
THE AFTERNOON.

SHOWERS AND THUNDERSTORMS...WITH THE POTENTIAL FOR ISOLATED
STRONG STORMS ALONG THE COAST...WILL BE ALSO POSSIBLE THROUGHOUT
THE DAY SATURDAY AHEAD OF AND ALONG THE COLD FRONT. SEVERAL
INGREDIENTS ARE IN PLACE FOR THUNDERSTORMS BUT THE MAIN QUESTION
WILL BE IF THE INSTABILITY CAN BE REALIZED TO SUPPORT DEVELOPMENT.
GUIDANCE INDICATES THE PRESENCE OF MUCAPE VALUES ALONG THE COAST
1000-1200 J/KG...0-6 KM BULK SHEAR APPROACHING 60-65 KTS...AND
MIDLEVEL LAPSE RATES AROUND 6.5 C/KM...RAISING THE POTENTIAL FOR
MAYBE SMALL HAIL OR SOME GUSTY WINDS FROM THUNDERSTORMS ALONG THE
COAST. FOR NOW THINK THE ATMOSPHERE MAY BE TOO STABLE WITH
FORECAST SOUNDINGS SHOWING THE PRESENCE OF A WEAK CAPPING
INVERSION. BEST CHANCES FOR STRONGER ACTIVITY APPEARS TO BE ALONG
THE FRONT DURING THE AFTERNOON AND EVENING HOURS AS IT APPROACHES
THE UPPER TEXAS COAST.

WEAK OVERRUNNING BEHIND THE FRONT COUPLED WITH ADDITIONAL LIFT
FROM THE PASSING SHORTWAVE TROUGH WILL PROMOTE ISOLATED TO
SCATTERED SHOWERS THROUGHOUT THE DAY ON SUNDAY...WITH BEST
CHANCES CHANCES PRIMARILY EAST OF THE BRAZOS RIVER. COOLER
TEMPERATURES WILL STICK AROUND SUNDAY...BEFORE A BRIEF WARM UP
MONDAY AS WEAK ONSHORE FLOW RESUMES.

IN THE EXTENDED... A STRONG ARCTIC FRONT WILL PUSH ACROSS THE
NORTHERN PLAINS EARLY NEXT WEEK AND REACH SOUTHEAST TEXAS IN THE
TUESDAY/WEDNESDAY TIMEFRAME. SURFACE HIGH PRESSURE BUILDING SOUTH
BEHIND THIS GUIDANCE LOOKS TO BRING A VERY CHILLY END TO 2015. MODEL
GUIDANCE IS OVERLY OPTIMISTIC/WARM WITH MID-WEEK HIGH TEMPERATURES
NEAR 50 GIVEN THE STRENGTH OF THE ARCTIC ANTICYCLONE THAT WILL
SETTLE INTO THE STATE. NAEFS ANOMALIES SHOW THE SURFACE HIGH
PRESSURE CLOSE TO 3 STANDARD DEVIATIONS ABOVE NORMAL /INDICATING A
VERY COLD AIRMASS/ AND FORECAST SOUNDINGS SUPPORT GOING COLDER
THAN GUIDANCE WITH TEMPERATURES IN THE MID 30/S TO LOW 40/S. HOW
COLD TEMPERATURES WILL GET CENTERS AROUND THE ACTUAL PLACEMENT OF
THE SURFACE HIGH...SO FOR NOW WILL CONTINUE TO TREND TEMPERATURES
COLDER /IN THE MID 40S WEDNESDAY AND THURSDAY/ AND ALLOW LATER
SHIFTS TO REFINE. AS ANOTHER TROUGH MOVES ACROSS THE SOUTHERN
PLAINS TOWARDS THE END OF NEXT WEEK...PRECIPITATION CHANCES WILL
INCREASE AGAIN. DESPITE THE COLD AIR IN PLACE...THERMAL PROFILES
SUPPORT A COLD RAIN...AS OPPOSED TO ANY KIND OF WINTRY
PRECIP...IN THE CARDS FOR THE END OF NEXT WEEK.

ALL IN ALL... IT/S LOOKING LIKE A COLD AND POTENTIALLY WET START
TO 2015 FOR SOUTHEAST TEXAS.

HUFFMAN

MARINE...
HAVE EXTENDED SMALL CRAFT ADVISORY FOR COASTAL WATERS
FROM 20 TO 60 NM OFF SHORE UNTIL 9PM TONIGHT AS WINDS AND SEAS HAVE
BEEN SLOW TO SUBSIDE THIS AFTERNOON.

A TIGHTENING PRESSURE GRADIENT COMBINED WITH THE EFFECTS OF A LOW
LEVEL JET HAVE PRODUCED 20 TO 25 KNOT WINDS AND SEAS RUNNING 8 TO 9
FEET AT BUOY 019...LOCATED 60 MILES SOUTH OF FREEPORT. WINDS AND
SEAS ARE STILL EXPECTED TO GRADUALLY DIMINISH TONIGHT/OVERNIGHT AS
THE NEXT COLD FRONT BEGINS TO APPROACH SOUTHEAST TEXAS.  IT IS
EXPECTED TO MOVE OFF THE COAST TOMORROW EVENING.  WITH A STRONG
ONSHORE FLOW OF WARM/MOIST AIR OVER COOLER WATERS...SEA FOG IS
LIKELY ALONG THE UPPER TEXAS COAST OVER NIGHT AND DURING THE DAY
SATURDAY.  44

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      62  63  42  53  38 /  50  60  40  20  10
HOUSTON (IAH)              65  72  47  53  40 /  50  70  50  40  10
GALVESTON (GLS)            66  70  50  53  48 /  50  70  70  60  10

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION UNTIL 3 AM CST SATURDAY 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...23


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