Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 250332
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
932 PM CST WED DEC 24 2014

.UPDATE...
SEE DISCUSSION FOR EVENING UPDATE.

&&

.DISCUSSION...
SURFACE HIGH PRESSURE IS CURRENTLY LOCATED OVER SOUTH TEXAS WITH
THE RIDGE AXIS EXTENDING THROUGH THE AREA. WINDS HAVE GONE CALM
ACROSS MULTIPLE SITES THIS EVENING ALLOWING TEMPERATURES TO
QUICKLY FALL. CURRENT FORECAST HAS LOW TEMPS SLIGHTLY BELOW
GUIDANCE AND GIVEN CURRENT TRENDS THIS LOOKS REASONABLE. MADE ONLY
MINOR CHANGES TO MIN T GRIDS FOR COASTAL AREAS. SURFACE HIGH
PRESSURE TOMORROW IS FORECASTED TO QUICKLY PULL EAST WITH A
TIGHTENING PRESSURE GRADIENT. 850 TEMPS ARE CURRENTLY JUST BELOW
FREEZING BUT TOWARDS MIDLAND... AMARILLO... AND DEL RIO 850 TEMPS
HAVE WARMED BY ABOUT FIVE DEGREES IN 12 HOURS. NAM IS SHOWING 850
TEMPS WARMING TOWARDS 6 DEGREES C CHRISTMAS DAY. THANKS TO QUICKLY
RISING 850 TEMPS HAVE GONE AHEAD AND RAISED MAX TEMPERATURES BY A
DEGREE OR TWO FOR CHRISTMAS. GFS AND NAM SOUNDINGS ALSO HINTING AT
SOME HIGH CLOUDS FORMING ALONG THE COAST TOMORROW SO MADE MINOR
CHANGES TO SKY GRIDS. NO OTHER CHANGES REQUIRED AT THIS TIME. 23

&&

.PREV DISCUSSION... /ISSUED 528 PM CST WED DEC 24 2014/

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

40

AVIATION...
HIGH PRESSURE OVER FAR SOUTHERN TEXAS AND NORTHERN MEXICO WILL
MOVE INTO THE WESTERN AND NORTHERN GULF OF MEXICO TONIGHT AND
THURSDAY. BY LATE THURSDAY MORNING...THE PRESSURE GRADIENT WILL
TIGHTEN ENOUGH FOR BREEZY SOUTHERLY WINDS TO DEVELOP OVER ALL THE
INLAND SITES. THE WINDS MAY GUST TO BETWEEN 20 AND 25 KNOTS
DURING THE AFTERNOON. OTHERWISE...VFR CONDITIONS ARE EXPECTED.

40

PREV DISCUSSION... /ISSUED 307 PM CST WED DEC 24 2014/

DISCUSSION...
A RATHER COOL AFTERNOON WITH MAX TEMPS STRUGGLING TO WARM INTO THE
UPPER 50S. CLOUD COVER OVER THE EASTERN HALF OF THE AREA WILL EXIT
THE REGION BY SUNSET LEAVING CLEAR SKIES OVERNIGHT. WINDS WILL
ALSO DECOUPLE AS SFC HIGH PRESSURE OVER NORTHERN MEXICO DRIFTS
EAST. THE HIGH WILL BE EAST OF THE REGION ON THURSDAY AND WINDS
WILL BECOME ONSHORE AND STRENGTHEN AS LOW PRESSURE OVER SE
COLORADO DEEPENS. MOISTURE LEVELS WILL DEEPEN ON FRIDAY AS ONSHORE
WINDS PERSIST. PW VALUES ON FRIDAY REACH 1.10 AND FCST SOUNDINGS
SATURATE TO AROUND 800 MB. MOISTURE LOOKS DEEP ENOUGH TO GENERATE
A FEW SHOWERS BY FRI AFTN. PW VALUES REACH 1.40 INCHES ON SATURDAY
AHEAD OF ANOTHER COLD FRONT. THE FRONT WILL TRIGGER SCATTERED
SHOWERS AND THUNDERSTORMS AS IT CROSSES THE AREA. POST FRONTAL
RAIN WILL LIKELY PERSIST SAT NITE INTO EARLY SUNDAY AS THE FLOW
ALOFT REMAINS OUT OF THE SOUTHWEST AND SFC WINDS WILL BE NORTH.
ISENTROPIC UPGLIDE SHOULD BE MAXIMIZED SAT NIGHT. A S/WV TROUGH
WILL APPROACH THE PACIFIC COAST ON SATURDAY NIGHT AND THIS
FEATURE WILL NUDGE ANOTHER S/WV OVER SW TX EASTWARD. THE TEXAS
S/WV FILLS AS IT MOVES EAST AND THE FLOW ALOFT BECOMES ZONAL BY
MON 00Z. THE SET UP FOR ISENTROPIC UPGLIDE ON SUNDAY WHICH LOOKED
EXTREMELY FAVORABLE 24 HOURS AGO LOOKS CONSIDERABLY LESS FAVORABLE
NOW. THE CANADIAN CONTINUES TO SHOW SOME POTENTIAL FOR ISENTROPIC
UPGLIDE WHILE THE GFS AND ECMWF HAVE BACKED OFF. GLOBAL MODELS
CONTINUE TO SHOW SE TX IN A POTENT 155 KT RRQ WHICH SHOULD ENHANCE
PRECIP THROUGH EARLY SUN AFTN. SUBSIDENCE IN THE WAKE OF THE
DEPARTING S/WV SHOULD ALLOW FOR A BRIEF PERIOD OF DRY WEATHER AND
CLEARING SKIES ON MONDAY. ANOTHER UPPER TROUGH WILL DEVELOP OVER
THE SW U.S. AND ISENTROPIC UPGLIDE DEVELOPS AGAIN ON TUESDAY WITH
CLOUDS AND LIGHT RAIN RETURNING. THE ECMWF IS BRINGING VERY COLD
AIR INTO TEXAS AROUND THE NEW YEARS HOLIDAY AND FCST SOUNDINGS DO
SHOW SOME POTENTIAL FOR SLEET/FRZ RAIN NORTH OF A BRYAN TO
LIVINGSTON LINE.

MARINE...
EXERCISE CAUTION STATEMENT WILL REMAIN NECESSARY INTO THE EARLY
EVENING WITH WINDS...ALTHOUGH WINDS WILL DIMINISH THROUGH THE
EVENING BEFORE TURNING TO ONSHORE FLOW CHRISTMAS MORNING.
SOUTHERLY WINDS WILL LIKELY REACH CAUTIONARY OR EVEN APPROACH SCA
CRITERIA BY THURSDAY NIGHT TOMORROW...ESPECIALLY FOR THE OUTER
WATERS. ANOTHER COLD FRONT WILL CROSS THE AREA LATE SATURDAY
BRINGING A RETURN OF UNSETTLED WEATHER FOR THE WEEKEND.

TIDES ARE CURRENTLY ABOUT 1 FOOT BELOW NORMAL IN THE UPPER BAYS.
HOWEVER...AS WE MOVE OUT OF LOW TIDE AND WINDS DIMINISH LATER TODAY
EXPECT ANY LOW TIDE ISSUES TO ABATE BY EARLY THIS EVENING.

48

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      35  63  49  69  59 /   0   0  10  20  40
HOUSTON (IAH)              36  64  54  71  61 /   0   0  10  20  40
GALVESTON (GLS)            44  63  62  69  63 /   0   0  10  20  30

&&

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