Area Forecast Discussion
Issued by NWS Houston/Galveston, TX

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FXUS64 KHGX 050908
AFDHGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
408 AM CDT TUE MAY 5 2015

.DISCUSSION...
SFC ANALYSIS THIS MORNING HAS AN AREA OF LOW PRESSURE OVER
TRANSPECOS/W TX WITH SE WINDS OFF THE GULF. MOISTURE AXIS
STRETCHES FROM THE COASTAL BEND NW TO THE HILL COUNTRY AND THEN
TOWARDS THE LLANO ESTACADO. UPPER AIR ANALYSIS HAS UPPER LOW OVER
THE DESERT SW WITH A WEAK SHORTWAVE TROUGH AXIS EXTENDING FROM IT
TOWARDS W TX. UPPER LEVEL JET WAS PUSHING ACROSS NOR MEXICO INTO
TX WITH SOME SPEED CONVERGENCE AHEAD OF IT. A SECOND UPPER LOW WAS
NOTED OVER THE PAC NW WHICH WILL HELP PUSH THE UPPER LOW OVER AZ
INTO THE PLAINS TODAY/TOMORROW. A LITTLE MORE DIFFICULT TO TRACK
IS AN EASTERLY WAVE IN THE GULF WITH AN AXIS OF HIGHER PRECIP
WATER VALUES. GOES SOUNDER PRECIP WATER PRODUCT DOES SHOW THIS
AREA OF ENHANCED MOISTURE SOUTHWARD INTO THE GULF FROM LCH THIS
MORNING. RADAR SHOWS A FEW SHOWERS IN E TX DUE TO THIS HIGHER
MOISTURE BUT OVERALL NOT MUCH OTHER ACTIVITY.

RECENT HRRR/WRF ARW RUNS CONTINUE TO SUPPORT THE SYNOPTIC MODELS
WITH PRECIP DEVELOPING LATER THIS MORNING AND THROUGH THE
AFTERNOON. THINK 40/50 POPS LOOK ON TRACK FOR THE SCATTERED
ACTIVITY EXPECTED TODAY. INSTABILITY WILL BE LIMITED TO 500-1000
J/KG WITH PRECIP WATER VALUES AROUND 1.6-1.7 INCHES. THIS SHOULD
BE ENOUGH TO AT LEAST SUPPORT SOME LOCALLY HEAVY RAINFALL BUT DO
NOT EXPECT MUCH OF AN IMPACT OTHER THAN TYPICAL STREET FLOODING
SHOULD ANY OF THE STORMS REALIZE 1-2 INCH/HR RAIN RATES. ALSO
LOOKS LIKE DAY TIME HEATING MAY BE NEEDED TO INITIATE
SHOWER/THUNDERSTORM ACTIVITY. CONVECTIVE TEMPS LOOK TO BE IN THE
LOW 80S AND THAT IS CLOSE TO FORECAST MAX TEMPS TODAY AS WELL.

PRECIP CHANCES LOOK TO GO DOWN WED AND ARE RATHER LIMITED
THUR/FRI/SAT DESPITE WEAK CAPPING IF ANY AND DECENT MOISTURE WITH
PRECIP WATER VALUES HANGING AROUND 1.3-1.5 INCHES. MOISTURE DOES
INCREASE PER GFS FRI WITH HIGHER MOISTURE LINGERING THROUGH THE
WEEKEND. WHILE MOISTURE AND INSTABILITY REMAIN
ESTABLISHED...CONVECTION WILL BE LIMITED DUE TO THERE NOT REALLY
BEING ANY BOUNDARIES TO FOCUS THE CONVECTION. THIS MEANS MESOSCALE
FORCING WILL BE NEEDED TO ORGANIZE CONVECTION. ALSO OVERALL JET
STRUCTURE WHILE STARTING OUT FAVORABLE BECOME LESS FAVORABLE FOR
CONVECTION. AFTER UPPER LOW OVER DESERT SW MOVES INTO THE
PLAINS...JET BECOMES MORE ANTICYCLONICALLY CURVED AS NOTED BEFORE
ON WED THROUGH THE END OF THE WEEK. WHILE THERE IS SOME DIFFLUENCE
ALOFT WITH THE JET THERE IS ALSO SPEED CONVERGENCE ALOFT WHICH MAY
OFF SET ANY LARGE SCALE ASCENT. JET FINALLY BECOMES MORE FAVORABLE
FOR CONVECTION SUN INTO MON AS UPPER LOW MOVES TOWARDS THE C
PLAINS AND MORE OF THE JET CORE MOVES OVER TX. SUN/MON IS ALSO
WHEN HIGHER 40 POPS COME BACK INTO THE FORECAST AS BOTH THE
GFS/ECMWF SHOW MORE CONVECTIVE ACTIVITY.

MAIN DIFFERENCE IN THE EXTENDED FORECAST IS NOW WHETHER A COLD
FRONT WILL WORK INTO SE TX. THE ECMWF STILL HAS A FRONT REACHING
THE AREA WHILE THE GFS HAS BACKED OFF ON ANY FROPA. THE FRONT WILL
ALSO BE A FACTOR WITH RAIN CHANCES GOING INTO MONDAY. OVERALL
TEMPERED RAIN CHANCES GIVEN THIS IS THE EXTENDED FORECAST AND THE
DETAILS WILL LIKELY CHANGE QUITE A BIT. ALSO SPLIT THE DIFFERENCE
ON TEMPS BETWEEN THE GFS/ECMWF FOR THE MON/TUE FORECAST NEXT WEEK.

39

&&

.MARINE...
MODERATE ONSHORE WINDS AND ELEVATED SEAS CAN BE EXPECTED THROUGH
THE END OF THE WEEK. CAUTION FLAGS ARE UP...AND ADVISORIES MIGHT
BE NEEDED. THE BEST CHANCE FOR SHOWERS AND SOME THUNDERSTORMS
SHOULD BE TODAY THROUGH TOMORROW MORNING. ONSHORE WINDS WILL
PERSIST INTO THE UPCOMING WEEKEND. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
COLLEGE STATION (CLL)      81  68  84  70  84 /  50  30  30  20  30
HOUSTON (IAH)              81  70  84  71  85 /  50  20  20  10  20
GALVESTON (GLS)            81  73  81  74  82 /  40  20  20  10  20

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION FROM NOON CDT TODAY THROUGH
     THIS EVENING FOR THE FOLLOWING ZONES: GALVESTON BAY...
     MATAGORDA BAY.

     SMALL CRAFT SHOULD EXERCISE CAUTION THROUGH LATE TONIGHT 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...39
AVIATION/MARINE...42


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