Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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000
FXUS64 KHGX 200315
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
915 PM CST WED NOV 19 2014

.UPDATE...
SEE EVENING UPDATE.

&&

.DISCUSSION...
AT 8 PM...SURFACE HIGH PRESSURE WAS OVER THE FLORIDA PANHANDLE.
ONSHORE WINDS HAD RETURNED TO SE TX AND MOISTURE LEVELS ARE ON THE
RISE. SFC DEW PTS ARE IN THE UPPER 40S AND LOWER 50S AND OVERNIGHT
LOWS WILL BE MUCH WARMER THAN THE PAST FEW NIGHTS. AT 850
MB...WEAK RIDGING WAS NOTED OVER DEEP SOUTH TEXAS AND THE WESTERN
GULF. 850 MSTR WAS BEGINNING TO INCREASE FROM BRO TO CRP TO LCH. A
WEAK S/WV WAS NOTED OVER THE LEE OF THE ROCKIES EXTENDING SW INTO
EASTERN NEW MEXICO. THIS FEATURE WILL WEAKEN AS IT MOVES ACROSS
THE SOUTHERN PLAINS BUT THE SUBTLE LIFT IT PROVIDES COUPLED WITH
WEAK WARM AIR ADVECTION AND AN INCREASE IN MOISTURE SHOULD YIELD
SCATTERED SHOWERS ON THURSDAY. PREV FCST HAS THIS WELL COVERED.
OTHER THAN SOME COSMETIC TWEAKS TO MIN TEMPS AND SKY GRIDS...THE
PREVIOUS FCST IS IN GOOD SHAPE. A QUICK PEAK AT SATURDAY STILL
SUPPORTS STRONG TO SEVERE STORMS WITH STRONG DYNAMICS MOVING
ACROSS SE TX IN THE AFTN. SOME INTERESTING CLIMATE FACTS TO PASS
ALONG ABOUT OUR RECENT COLD SNAP. SEE THE CLIMATE SECTION BELOW.

43

&&

.CLIMATE...
HOUSTON RECORDED A RECORD LOW OF 30 DEGREES THIS MORNING. THE
HIGH TEMPERATURE THIS AFTERNOON WAS 69 DEGREES. THE HIGH IS
SIGNIFICANT BECAUSE HIGH TEMPERATURES HAVE NOT EXCEEDED 58
DEGREES SINCE NOV 11TH. THE LAST TIME HOUSTON RECORDED 7
CONSECUTIVE DAYS WITH HIGH TEMPS AT OR BELOW 58 DEGREES DURING THE
MONTH OF NOVEMBER WAS BACK IN 1907. THE TEMPERATURE WAS BELOW 58
DEGREES BETWEEN 11/11/1901 AND 11/18/1907. THAT WAS ALSO THE LAST
TIME (UNTIL THIS YEAR) THAT HOUSTON SUFFERED A DAILY AVERAGE
TEMPERATURE DEPARTURE GREATER THAN 10 DEGREES PER DAY FOR EIGHT
CONSECUTIVE DAYS.

                    1907                    2014

          DATE  TEMP  DEP              DATE  TEMP  DEP

          NOV 11  45  -18              NOV 12  51  -13
          NOV 12  40  -24              NOV 13  41  -22
          NOV 13  42  -22              NOV 14  41  -22
          NOV 14  43  -20              NOV 15  48  -14
          NOV 15  51  -12              NOV 16  50  -12
          NOV 16  45  -17              NOV 17  44  -18
          NOV 17  50  -12              NOV 18  44  -18
          NOV 18  50  -12              NOV 19  50  -11

LASTLY...SEVERE WEATHER IN NOVEMBER DOES OCCUR. SOME OF THE MORE
NOTORIOUS TORNADO OUTBREAKS THAT HAVE AFFECTED SE TX OCCURRED
DURING NOVEMBER. HERE ARE A FEW REMINDERS...

DATE         EF SCALE        LOCATION

NOV 8  2011    EF-1          HOUSTON AND TEXAS CITY

NOV 17 2003    EF-2          24 TORNADOES - 72 INJURIES

NOV 6  2000    EF-1          CONROE AND SHEPHERD

NOV 16 1993    EF-1          DOWNTOWN HOUSTON - 26 MINOR INJ

NOV 21 1992    EF-4          KATY...HOUSTON...CHANNELVIEW
                             LAST EF-4 TO AFFECT SE TX

NOV 15 1987    EF-2          4 TORNADOES
                             CALDWELL AND NORMANGEE
                             5 KILLED AND 35 INJURED

43

&&

.PREV DISCUSSION... /ISSUED 529 PM CST WED NOV 19 2014/

DISCUSSION...
THE 00Z AVIATION DISCUSSION IS BELOW.

40

AVIATION...
VFR CONDITIONS ARE EXPECTED THIS EVENING. HOWEVER...A MOIST
ONSHORE FLOW WITH A DECENT LOW-LEVEL JET WILL HELP LOWER CEILINGS
TO MVFR LEVELS AFTER 09Z FOR KCLL...KCXO...AND KUTS. THERE IS AN
OUTSIDE CHANCE THAT MVFR CONDITIONS COULD DEVELOP AT THE HOUSTON
METRO AIRPORTS BETWEEN 10Z AND 15Z. THE MODELS DO SUPPORT MVFR
CONDITIONS DEVELOPING FROM KHOU TO THE COAST AFTER 14Z...BUT
HOLDING OFF AT KIAH UNTIL AFTER 00Z THURSDAY EVENING. THERE IS
ALSO A CHANCE FOR RAIN SHOWERS TO DEVELOP THURSDAY AFTERNOON...
MAINLY OVER THE INLAND SITES.

40

PREV DISCUSSION... /ISSUED 319 PM CST WED NOV 19 2014/

DISCUSSION...
TEMPERATURES HAVE WARMED INTO THE MID TO UPPER 60S THIS AFTERNOON
AS SURFACE HIGH PRESSURE HAS MOVED OFF TO THE EAST ALLOWING SOUTH
TO SOUTHWEST WINDS TO RETURN TO THE AREA. PWATS HAVE ALREADY
STARTED TO COME BACK TODAY WITH GPS MET SITE SHOWING ANGLETON UP
TO 0.75". TOMORROW MOISTURE VALUES WILL CONTINUE TO RISE WITH THE
LOW LEVEL RH VALUES DRASTICALLY INCREASING. ISENTROPIC UPGLIDE
WILL ALSO START TO COMMENCE TOMORROW BRINGING THE CHANCE OF RAIN
BACK TO THE AREA.

ON FRIDAY A POTENT SHORTWAVE WILL DIVE TO THE SOUTH TOWARDS
SOUTHERN CALIFORNIA AND THEN BEGIN TO PUSH TO THE EAST. THE
SHORTWAVE WILL THEN CROSS TEXAS SATURDAY BRINGING A CHANCE OF
SEVERE WEATHER TO THE AREA. THE SHORTWAVE WILL BEGIN TO TAKE A
NEGATIVE TILT TO IT SATURDAY AFTERNOON AS IT APPROACHES SOUTHEAST
TEXAS. PWATS WILL ALSO CLIMB TO AROUND 1.70" WHICH IS AROUND 2SD
ABOVE NORMAL FOR THIS TIME OF YEAR. CAPE VALUES SATURDAY AFTERNOON
ARE FORECASTED TO BE BETWEEN 800 AND 1500 J/ KG K. GREATEST
POTENTIAL INSTABILITY LOOKS TO BE TOWARDS THE SOUTH BUT SHEAR
VALUES REMAIN IMPRESSIVE ACROSS THE CWA. SFC TO 1KM SHEAR IS
FORECASTED TO BE AROUND 20 KTS WITH SFC TO 6 KM SHEAR AROUND 45
KTS. UPPER LEVELS WILL ALSO PROVIDE DIFFLUENCE ACROSS THE AREA
SATURDAY. THE ESPECIALLY TRICKY PART WILL BE WHERE THE BEST UPPER
LEVEL DIFFLUENCE SETS UP. THE GFS PLACES THE BEST UPPER LEVEL
SUPPORT TOWARDS THE DALLAS/ FORT WORTH AREA WHILE THE EURO HAS THE
BEST UPPER LEVEL SUPPORT THROUGH OUR AREA. THE OVERALL PATTERN
SUPPORTS HEAVIER RAIN TOWARDS THE NORTH WITH THE STRONGER MORE
DISCRETE CELLS TOWARDS THE SOUTH IN THE HIGHER INSTABILITY. THE
MAIN THREATS WITH THIS WILL BE THE POTENTIAL FOR TORNADOES AND
DAMAGING WINDS. SECONDARY THREAT OF HEAVY RAINFALL WILL BE
POSSIBLE.

THE UPPER LEVEL SHORTWAVE WILL QUICKLY EJECT TO THE NORTHEAST
SUNDAY MORNING WITH DRIER MID LEVEL AIR FILTERING QUICKLY BEHIND
THE SHORTWAVE. THIS MEANS WE WILL CLEAR OUT QUICKLY SUNDAY
MORNING. A COLD FRONT WILL THEN MOVE THROUGH THE AREA SUNDAY NIGHT
ALLOWING A RETURN TO BELOW NORMAL TEMPERATURES FOR THE START OF
NEXT WORK WEEK. 23

MARINE...

SE FLOW PREVAILING THIS AFTERNOON AT 10-15 KNOTS OVER THE GULF
WATERS. WILL BE SEEING THESE WINDS INCREASE TONIGHT/THURSDAY AND BY
THURSDAY AFTERNOON WINDS SHOULD SUPPORT SCEC WITH BUILDING SEAS.
WILL PUT UP THE SCEC FLAGS NOW BUT SCA MAY BE NEEDED BY EVENING AS
GRADIENT CONTINUES TO TIGHTEN IN ADVANCE OF THE NEGATIVELY TILTED
TROUGH ON SATURDAY. BY SATURDAY SEAS SHOULD BE 5-8 FEET WITH WINDS
OF 17-23 KNOTS AND A LONG FETCH. IN ADDITION STRONG TO SEVERE
THUNDERSTORMS MAY BE POSSIBLE OVER THE COASTAL WATERS SATURDAY
AFTERNOON AND NIGHT.
45

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      51  68  60  73  62 /  10  30  50  60  40
HOUSTON (IAH)              55  71  61  75  62 /  10  30  40  40  30
GALVESTON (GLS)            59  69  64  72  66 /  10  30  40  30  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION FROM THURSDAY AFTERNOON
     THROUGH THURSDAY EVENING 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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