000
FXUS64 KBRO 120504 AAC
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1204 AM CDT SUN MAY 12 2013

.DISCUSSION...WILL INCREASE POPS TO 30 PERCENT OVERNIGHT FOR THE
MIDDLE AND LOWER VALLEY WITH RADAR PICKING UP MORE ECHOS OVER
NORTHEAST MEXICO. DIFFLUENT FLOW ALOFT AND A SPEED MAX APPROACHING
SOUTH TEXAS TO MAINTAIN INITIATION OF CONVECTION SOME WITH THUNDER
FOR THE NEXT FEW HOURS. RAINFALL AMOUNTS WILL BE LIGHT WITH SOME
MODERATE DOWNPOURS.

&&

.DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

&&

.AVIATION...VFR CEILINGS ARE NOTED OVER DEEP SOUTH TEXAS. SOME
LOWERING CIGS TO MVFR IS EXPECTED OVERNIGHT AS SHOWERS AND SOME
THUNDERSTORMS INCREASE FROM THE SOUTHWEST OVERNIGHT. THE SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS TO INCREASE BETWEEN 06Z TO AT
LEAST 09Z FROM HIGHWAY 281 EAST TO THE COAST. OTHER THUNDERSTORMS
ARE NOTED PASSING NEAR OR NORTH OF THE NORTHERN COUNTIES OF JIM
HOGG AND BROOKS WITH A FEW OTHER AREAS OF CONVECTION APPROACHING
ZAPATA COUNTY. VFR TO PREVAIL ON SUNDAY WITH LOWER CIGS AND VSBY
WITHIN ISOLATED TO SCATTERED CONVECTION. LIGHT NORTH TO NORTHEAST
SURFACE WINDS ARE EXPECTED.

&&

.PREV DISCUSSION... /ISSUED 811 PM CDT SAT MAY 11 2013/

DISCUSSION...LARGER AREA OF PRECIP DEVELOPING ON KBRO RADAR ABOUT
35 MILES SOUTHWEST OF RIO GRANDE CITY SLIDING TO THE NORTHEAST.
WATER VAPOR SHOWS A SLIGHTLY MORE DIFFLUENT AREA ACROSS NUEVO LEON
MOVING INTO THE REGION AND BASED ON ITS NORTHEASTERLY DIRECTION
BELIEVE IT IS AT LEAST PARTIALLY ATTRIBUTABLE TO FRONTAL
OVERRUNNING. LIFTING A PARCEL FROM THAT AREA SHOWS ABOUT 500 J/KG
OF ELEVATED INSTABILITY SO A FEW THUNDERBOLTS WILL BE AT LEAST
POSSIBLE WITH THIS AREA AS IT MOVES INTO HIDALGO AND STARR COUNTY
IN THE NEXT HOUR OR TWO. RAINFALL AMOUNTS WOULD LIKELY BE ABOUT
0.05 TO 0.10 INCHES. UPDATED NEAR TERM GRIDS TO INCREASE RAIN
CHANCES IN FAVORED AREAS THROUGH 100 AM.

WITH AT LEAST SOME LARGE SCALE ASCENT ONGOING THROUGH THE NIGHT
THE CHANCE FOR SHOWERS OR POSSIBLY A THUNDERSTORM WILL
REMAIN BUT 20 PERCENT CHANCE AFTER 1 AM...THE GOING
FORECAST...SOUNDS ABOUT LIKE THE APPROPRIATE PROBABILITY FOR
SOMETHING GETTING GOING. SFC AND ELEVATED INSTABILITY IS VERY
LIMITED SO CONFIDENT BRIEF MODERATE TO HEAVY RAIN THE MAIN ISSUE
WITH ANY STRONGER CONVECTION THAT MIGHT GET GOING THROUGH SUNRISE.
/68-JGG/

PREV DISCUSSION... /ISSUED 629 PM CDT SAT MAY 11 2013/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...EVENING SOUNDING SHOWS LOWER ATMOSPHERE HAS DRIED A
LITTLE MORE THAN EXPECTED SO HAVE IMPROVED THE OUTLOOK OVERNIGHT
TO PREDOMINANT VFR. WATCHING A FEW SHOWERS THAT MAY DEVELOP
THROUGH THIS EVENING FROM THE SOUTHWEST BUT LIKELY WILL NOT DROP
VIS/CIG BELOW VFR FOR SIGNIFICANT PERIODS OF TIME. THUNDERSTORMS
MAY MOVE SOUTHEAST INTO THE REGION LATE TONIGHT BUT THE
PROBABILITY IS TOO LOW FOR TAF MENTION. THERE IS A BETTER CHANCE
FOR SHOWERS AND STORMS STARTING SUNDAY IN THE AFTERNOON BUT AGAIN
THE PROBABILITY IS TOO LOW FOR TAF MENTION AT THIS TIME WITH
PREDOMINANT VFR CONDITIONS EXPECTED. /68-JGG/

PREV DISCUSSION... /ISSUED 157 PM CDT SAT MAY 11 2013/

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...
LATEST WV SATELLITE IMAGERY SHOWS CLOSED LOW OVER NORTHERN MEXICO
SLIGHTLY MOVING SOUTHWARD KEEPING THE RIO GRANDE VALLEY UNDER SW
FLOW ALOFT AND PUSHING DRY AIR INTO THE AREA. THE SURFACE FRONT IS
SOUTH OF THE BORDER WITH A LIGHT TO MODERATE N TO NE WIND IN PLACE
ACROSS THE VALLEY WITH CLOUDS BREAKING. EXPECT THIS CLOUD COVER TO
CONTINUE TO BREAK INTO THE AFTERNOON AS DAYTIME HEATING CONTINUES.
THE POSSIBILITY OF SHOWERS IN THE AFTERNOON REMAIN AS THIS SYSTEM
CONTINUES TO PUSH WEAK WAVES INTO THE AREA. THIS COMBINED WITH THE
WARMER TEMPERATURES WILL ALLOW FOR A MORE UNSTABLE ENVIRONMENT.
THESE SHOWERS WILL MAINLY FAVOR THE COMMUNITIES NEAR THE BORDER
LINE. THE LOW TEMPERATURES WILL BE IN THE MID 60S ACROSS MUCH OF THE
VALLEY WITH A FEW LOCATIONS NEAR THE COAST IN THE 70S. RAINFALL
ACCUMULATIONS WILL BE BETWEEN HALF TO A QUARTER OF AN INCH POSSIBLE.
SUNDAY MOST OF THE SHOWERS SHOULD REMAIN SOUTH OF THE BORDER AND THE
DAY WILL BE ALMOST A REPEAT OF TODAY WITH NOT MUCH RAINFALL AS THE
FAVORABLE AREA IS FURTHER SOUTH OF THE VALLEY. HIGH TEMPERATURES
WILL BE IN THE LOWER 80S AS THE CLOUDS TAKE A LITTLE LONGER TO
BREAK. CONVECTION WILL INITIATE ONCE AGAIN IN THE LATE EVENING
ESPECIALLY ALONG THE BORDER AS THE UPPER LEVEL FLOW PUTS THE VALLEY
UNDER A MORE DIFFLUENT FLOW ALOFT AND THE FRONT LIFTS TO THE NORTH.
LOWS ON SUNDAY NIGHT WILL BE IN THE MID/UPPER 60S. /67/

LONG TERM /MONDAY THROUGH SATURDAY/...
A DIFFLUENT FLOW ALOFT IS EXPECTED TO CONTINUE ACROSS THE FORECAST
AREA AS WE HEAD INTO THE NEW WORKWEEK...THANKS TO A CUTOFF UPPER LOW
CENTERED NEAR THE GULF OF CALIFORNIA.  WITH THE UPPER LOW EXPECTED
TO SHOW LITTLE MOVEMENT...THE BIGGEST QUESTION IN MY MIND REVOLVES
AROUND THE POSSIBILITY OF CONVECTION EARLY IN THE WEEK.

IN ADDITION TO THE DIFFLUENT FLOW ALOFT...I FEEL THERE WILL PROBABLY
BE AT LEAST A LITTLE BIT OF EXTRA FORCING IN PLACE.  A BIT OF
UPPER-LEVEL JET ENERGY SHOULD ALLOW WEAK PERTURBATIONS TO EMANATE
AND MOVE ACROSS THE REGION.  GIVEN THE EXPECTED POSITION OF THE
SURFACE HIGH /FROM THE APPALACHIANS TO THE NORTHWESTERN GULF/...
PRECIPITABLE WATERS ARE FORECAST TO REMAIN MORE THAN 2 STANDARD
DEVIATIONS ABOVE NORMAL.  THIS LOW-LEVEL EASTERLY FLOW MAY ALSO
RESULT IN SOME UPSLOPE CONVECTIVE DEVELOPMENT...PROBABLY OVER THE
MOUNTAINS IN NORTHERN MEXICO.

IT IS NOT OUT OF THE REALM OF POSSIBILITY TO SEE SOME OF THIS
CONVECTION HEAD TOWARD OUR RIO GRANDE-BORDERING COUNTIES...WITH THE
GREATEST ODDS IN THE UPPER VALLEY.  GIVEN MY CONFIDENCE IN THIS
HAPPENING...I HAVE DECIDED TO TREND PRECIPITATION PROBABILITIES
DOWNWARD A BIT WITH THIS FORECAST PACKAGE.

THE CUTOFF UPPER LOW SHOULD OPEN UP TUESDAY NIGHT...AS AN
UPPER-LEVEL JET STREAK ROUNDS THE BASE OF ITS TROUGH.  THIS SHOULD
PUSH THE LOW INTO THE SOUTHERN PLAINS DURING THE DAY WEDNESDAY.  AS
PRECIPITATION PROBABILITIES WANE AS THE UPPER TROUGH AXIS HEADS
EAST...A DEVELOPING TROUGH OF LOW PRESSURE IN WEST TEXAS MAY RESULT
IN INCREASED SOUTHEASTERLY WINDS OVER THE REGION.

FROM THUSDAY THROUGH NEXT SATURDAY...OUR CORNER OF THE WORLD WILL
LIKELY BE BETWEEN WEATHER SYSTEMS.  UPPER-LEVEL TROUGHINESS IS
EXPECTED TO MOVE INTO THE WESTERN UNITED STATES THURSDAY.  THIS WILL
LIKELY PRODUCED INCREASED SHORTWAVE RIDGING OVER THE FORECAST AREA
FOR FRIDAY AND SATURDAY.  GIVEN THIS...AND AVAILABLE FORECAST
CONFIDENCE TOOLS SUGGESTING 500MB HEIGHTS AROUND 1 STANDARD
DEVIATION ABOVE NORMAL...I WILL TREND ON THE HIGH SIDE OF...OR GO
SLIGHTLY ABOVE...AVAILABLE GUIDANCE FOR TEMPERATURES FOR THE END OF
THE WEEK.  /53/

MARINE...

TONIGHT THROUGH SUNDAY NIGHT...
THE NORTHEAST WINDS WILL BEGIN TO SHIFT TO THE EAST AS THE SURFACE
HIGH DOMINATES THE NORTHERN PART OF THE GULF. THIS EASTERLY FLOW
WILL ALLOW FOR LONGER FETCH TO  INCREASE THE ONSHORE FLOW AND BUILD
SEAS. EXPECT SEAS TO BEGIN INCREASING INTO SUNDAY BETWEEN 4 TO 6
FEET. SCEC MARINE CONDITIONS WILL BE POSSIBLE OVER THE GULF WATERS
INTO TOMORROW. /67/

MONDAY THROUGH THURSDAY...
EASTERLY WINDS ARE EXPECTED TO CONTINUE ACROSS THE MARINE AREA EARLY
WIND THE WEEK...AS HIGH PRESSURE REMAINS CENTERED NEAR THE
APPALACHIANS.  AS THE SURFACE HIGH SHIFTS EAST...A SOUTHEASTERLY
FLOW EXPECTED TO RETURN BY TUSDAY NIGHT AND WILL LIKELY CONTINUE
THROUGH THURSDAY.  WIND SPEEDS WILL LIKELY INCREASE OVER THE MARINE
AREA BY WEDNESDAY...WHICH MAY NECESSITATE SMALL CRAFT TO EXERCISE
CAUTION OR THE ISSUANCE OF SMALL CRAFT ADVISORIES.  COMBINED SEAS
SHOULD AVERAGE 5 FEET OR LESS THROUGH MUCH OF THE FORECAST PERIOD.
A FEW SHOWERS OR STORMS MAY BE POSSIBLE OVER THE LAGUNA AND GULF
SOUTH OF PORT MANSFIELD EARLY IN THE WEEK.  /53/

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

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