Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 011607
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
1007 AM CST SUN MAR 1 2015

.UPDATE...
MORNING FORECAST UPDATE.

&&

.DISCUSSION...
LATEST SFC ANALYSIS HAS A COASTAL LOW OFF MATAGORDA BAY ALONG THE
UPPER TX COAST. THERE APPEARS TO BE TWO BOUNDARIES OF CONCERN. THE
FIRST HAS PUSHED MORE INLAND AND SEPARATES AIRMASS WITH TEMPS IN
THE 40S FROM AIRMASS WITH TEMPS IN UPPER 50S TO LOW 60S. SECOND
BOUNDARY IS THE TRUE WARM FRONT WHICH SEPARATES THE UPPER 50S/LOW
60S FROM THE UPPER 60S/LOW 70S WITH DEWPOINT TEMPS IN THE UPPER
60S AS WELL. THE 12Z CRP AND LCH SOUNDINGS CAPTURE THE COOLER
BOUNDARY LAYER AIRMASSES NORTH OF THESE BOUNDARIES. ONE GLARING
DIFFERENCE IS THE CRP SOUNDING SHOWS AN ELEVATED MIXED LAYER AND
CAP AT 700MB WHERE LCH DOES NOT. THIS MEANS LIFTING AN ELEVATED
PARCEL WOULD RESULT IN CONVECTION AND REASON WHY THERE HAS BEEN
SOME ISO TSRA BETWEEN HOUSTON AND BEAUMONT. SUSPECT THE EML WILL
ADVECT OVER SE TX MORE IN THE COMING DAYS AND LIKELY BE A FACTOR
IN THE FORECAST WHEN THE STRONG COLD FRONT COMES WED. UNTIL THEN
MAIN CONCERNS WILL BE HOW/WHEN/WHERE WARM FRONT PUSHES
NORTH/STALLS AND THEN PUSHES NORTH AGAIN THROUGH TUE. TEMP
FORECAST WILL BE VERY CHALLENGING. ONLY CHANGES TO THE FORECAST
THIS MORNING WERE FOR TEMP TRENDS AND RAIN CHANCES.

EARLY LOOK AT 12Z MODEL RUNS...NAM IS SIGNIFICANTLY SLOWER WITH
FROPA ON WED. GFS HAS BECOME MUCH MORE WET BEHIND THE FRONT ON WED
INTO THUR. WED NIGHT FORECAST WILL BE AN INTERESTING ONE.

39

&&

.PREV DISCUSSION... /ISSUED 615 AM CST SUN MAR 1 2015/

AVIATION...
A DAY MAINLY SPENT IN THE LIFR TO IFR CAT WITH PERIODIC LIGHT RAIN
OR DRIZZLE. A NEAR COASTAL TROUGH OF LOW PRESSURE AND INLAND ADVANCING
WARM FRONT WILL PROVIDE THE LOWER LEVEL CONVERGENCE NEEDED TO KEEP
DECKS AND VISIBILITIES LOW. A LIGHT INLAND NORTHERLY FLOW WITH
COASTAL EAST SOUTHEAST WINDS THROUGH THE PERIOD. 31

PREV DISCUSSION... /ISSUED 352 AM CST SUN MAR 1 2015/

DISCUSSION...
AREAS OF LIGHT RAIN CONTINUE TO DEVELOP EARLY THIS MORNING ACROSS
SOUTHEAST TEXAS AND ADJACENT COASTAL WATERS AND MOVE OFF TO THE NORTH
AND NORTHEAST. ANTICIPATE ONLY SUBTLE CHANGES IN THE WEATHER PATTERN
OVER THE NEXT COUPLE OF DAYS...RESULTING IN PERIODS OF MAINLY LIGHT
RAIN OR RAIN SHOWERS ALONG WITH AREAS OF FOG. SOME OF THE FOG COULD
BECOME DENSE...AND DENSE FOG ADVISORIES MIGHT BE NEEDED. MIGHT EVEN
SEE A THUNDERSTORM OR TWO...BUT THE GREATEST RISK AREA FOR THAT IS
EXPECTED TO BE OFF TO OUR NORTH AND NORTHEAST. WITH THIS FORECAST
PACKAGE...HAVE CONTINUED YESTERDAY`S TREND OF SLIGHTLY LOWERING
TEMPERATURES. A SIGNIFICANT WARM UP IS STILL IN STORE FOR THE AREA
ON TUESDAY AS SOUTH WINDS FINALLY RETURN AND STRENGTHEN AHEAD OF THE
AREA`S NEXT COLD FRONT. IT STILL LOOKS LIKE THIS STRONG FRONT WILL
MOVE THROUGH SOUTHEAST TEXAS ON WEDNESDAY WITH TEMPERATURES FALLING
BEHIND THE BOUNDARY. A TIGHT PRESSURE GRADIENT BEHIND THE FRONT WILL
BRING BREEZY/WINDY CONDITIONS TO THE AREA...AND WOULD NOT BE SURPRISED
IF WE END UP NEEDING A WIND ADVISORY WEDNESDAY NIGHT ON INTO THURSDAY
MORNING. CONDITIONS STILL LOOK FAVORABLE FOR POSSIBLE FROZEN PRECIP
UP NORTH WEDNESDAY NIGHT THROUGH THURSDAY MORNING. THERE IS A LOT OF
TIME FOR THIS FORECAST TO CHANGE...SO STAY TUNED. 42

MARINE...
THE DEVELOPMENT AND SLOW PROGRESSION OF A NEARSHORE TROUGH...AND ITS
ASSOCIATED WARM FRONTAL BOUNDARY MOVING ONTO THE UPPER TEXAS COAST...
HAS AND WILL FORTIFY THE FORMATION OF SEA FOG AND PERIODS OF
LIGHT RAIN OR DRIZZLE. LIGHT TO OCCASIONALLY MODERATE SOUTHEAST
WINDS WITH OFFSHORE SEAS FALLING BELOW CAUTION CRITERIA THROUGH
THE DAY. AS THIS WESTERN GULF TROUGH WASHES OUT LATE MONDAY...FOG
AND PERIODS OF LIGHT PRECIPITATION WILL LINGER. AS NORTHWESTERN
TEXAS SURFACE PRESSURES LOWER AHEAD OF THE NEXT COLD FRONT ON
TUESDAY... ONSHORE WINDS WILL STRENGTHEN TO NEAR CAUTION LEVELS.
THE COLD FRONTAL PASSAGE IS TIMED TO PASS ACROSS THE LOCAL WATERS
WEDNESDAY NIGHT. THIS IS FORECAST TO BE A STRONG FRONT AS A COLD
SHOT OF NORTHERN PLAINS AIR AND A TIGHT OFFSHORE GRADIENT PUSHES
WINDS TO NEAR GALE FORCE THURSDAY MORNING. 31

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      49  44  56  52  74 /  50  40  40  30  40
HOUSTON (IAH)              60  53  62  58  75 /  60  30  40  30  30
GALVESTON (GLS)            64  54  67  63  71 /  60  30  30  20  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...DENSE FOG ADVISORY UNTIL 10 PM CST THIS EVENING FOR THE
     FOLLOWING ZONES: GALVESTON BAY...MATAGORDA BAY...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 NOON CST TODAY 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...39



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