000
FXUS64 KBRO 090010 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
610 PM CST SAT MAR 8 2014

.DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW. ALSO
POSTED A SMALL CRAFT ADVISORY FOR EARLY SUNDAY MORNING BASED ON
THE TIMING AND STRENGTH OF A COLD FRONT MOVING SOUTH TOWARD THE
AREA.

&&

.AVIATION...THE ADVANCE ECHELON OF A COLD FRONT IS MARCHING
THROUGH LAREDO NOW...ON ITS WAY TOWARD THE RGV AND DEEP SOUTH
TEXAS TONIGHT. WINDS HAVE SHIFTED TO MODERATE NORTH NORTHWEST UP
STREAM...WITH DEW POINT DECREMENTS LAGGING BEHIND BY A FEW HOURS.
SCATTERED SHOWERS WILL CONTINUE THIS EVENING...WITH ISOLD EMBEDDED
THUNDERSTORMS...BUT THE REAL FIRST ROUND OF THE MAIN EVENT WILL
OCCUR OVERNIGHT...AS DIVERGENCE ASSOCIATED WITH A MID LEVEL LOW
OVER NORTHWEST MEXICO ADDS ITS FUEL TO THE FIRE. SFC CONVERGENCE
WILL TAKE ADVANTAGE OF A MOIST LOWER LEVEL IN PLACE TO GENERATE
GOOD RAIN MAKING CONVECTION AS THE FRONT MOVES THROUGH BETWEEN
MIDNIGHT AND DAWN...REACHING THE LOWER VALLEY JUST BEFORE DAWN.
WE`VE ALREADY SEEN SOME OF THAT THIS AFTERNOON WITH MDT SHOWERS
MOVING NORTH THROUGH THE BROWNSVILLE AREA. THE STRONG CAP THAT
WAS IN PLACE HAS RISEN AND WEAKENED...SUCH THAT DEEPER CONVECTION
IS NOW A POSSIBILITY WITH THE FRONT. EVEN AFTER THE FRONT MOVES
THROUGH HOWEVER...UNSETTLED WEATHER WILL CONTINUE AS THE UPSTREAM
MID LEVEL TROUGH TAKES ITS TIME MOVING OUT.

VFR CONDITIONS FOR NOW WILL DETERIORATE TO MVFR OVERNIGHT IN
LOWERED CEILINGS AND VISIBILITY WITH THE ARRIVAL OF THE FRONT.
OVER RUNNING ALOFT AND MODERATE TO BREEZY NORTH WINDS WILL KEEP
MVFR OVC THROUGH THE DAY SUNDAY...WITH IFR POSSIBLE LATE SUNDAY
AS WINDS DECREASE AND TEMPS DECREASE TO AROUND 50 SUNDAY NIGHT TO
MONDAY MORNING. PATCHY FOG WILL ALSO BE POSSIBLE WITH RAIN WETTED
SURFACES AND COOLER OVERNIGHT TEMPS.

&&

.PREV DISCUSSION... /ISSUED 236 PM CST SAT MAR 8 2014/

SHORT TERM /NOW THROUGH SUNDAY NIGHT/...
LIGHT LOW LAYER WARM ADVECTION CONTINUES AS MOISTURE POURS INTO THE
REGION ON LOW LEVEL SOUTHEASTERLIES. AMSU/SSMI BLENDED PRECIPITABLE
WATER ESTIMATES HAVE INCREASED PERSISTENTLY THROUGH THE DAY AS THE
COLUMN PRIMES FOR WHAT SHOULD BE A WIDESPREAD RAINFALL EVENT THROUGH
THE WEEKEND. PERSISTENT CLOUD COVER SHOULD CONTINUE THROUGH THE REST
OF THE AFTERNOON WITH A FEW BREAKS AS A RESULT. THE SURFACE FRONT
REMAINS A LITTLE AHEAD OF SCHEDULE BUT IN REASONABLE AGREEMENT WITH
THE GOING FORECAST.

REST OF THIS AFTERNOON...WINDS JUST ABOVE THE 850MB LAYER ARE OUT OF
THE SOUTH TO SOUTHWESTERLY WHICH SHOULD BE AIDING IN KEEPING A
CAPPING INVERSION IN PLACE OVER THE REGION. THIS IS SUPPORTED BY A
LACK OF DEPTH TO THE STRATOCUMULUS LAYER DEVELOPING OVERHEAD. THIS
IS EXPECTED TO HOLD UNTIL STRONGER UPPER LEVEL FORCING ARRIVES LATER
THIS EVENING AND TONIGHT AND KEPT POPS LOW THROUGH WHAT SHOULD BE
MOSTLY A DRY AFTERNOON.

TONIGHT...RIGHT REAR QUADRANT OF A JET MAX TO THE EAST OF NEEDLE
NOSE UPPER TROUGH OVER WEST TEXAS MOVES OVERHEAD TONIGHT INCREASING
LARGE SCALE LIFT AS A SURFACE FRONT PUSHES SOUTH INTO THE AREA. THIS
FRONT IS STILL A LITTLE AHEAD OF SCHEDULE BUT SHOULD ARRIVE LATE
THIS EVENING IN THE NORTHWESTERN PORTION OF THE CWA AND AROUND
MIDNIGHT OR A LITTLE LATER IN THE VALLEY. WITH LARGE SCALE ASCENT
LIFTING THE CAPPING INVERSION OUT THERE SHOULD BE MARGINAL
INSTABILITY FOR SURFACE BASED OR NEAR SURFACE BASED CONVECTION ALONG
THE FRONT AND JUST BEHIND IT. COASTAL TROUGHING DEVELOPS JUST
OFFSHORE AMID THE LARGE SCALE FORCING AND LOW LEVEL CONVERGENCE
REMAINS STRONG THROUGH THE OVERNIGHT WITH MODEST FRONTAL OVERRUNNING
DEVELOPING AT 700MB. HODOGRAPHS SUGGEST RELATIVELY SLOW STORM MOTION
FOR ANY DEEPER ACTIVITY AND CAN NOT COMPLETELY RULE OUT SOME MINOR
HYDRO ISSUES IF THUNDERSTORM COVERAGE IS HIGH AMID PWAT VALUES
AROUND 1.60 INCHES. RAISED POPS TO AROUND 100 PERCENT AREA WIDE WITH
GOOD SYNOPTIC SUPPORT AND MET/MAV/ECM GUIDANCE ALL SHOWING
CATEGORICAL PRECIP CHANCES. THUNDER WILL BE MORE ISOLATED TO
SCATTERED WITH THE BEST CHANCES RIGHT ALONG THE FRONT. TOTAL
RAINFALL AMOUNTS OF AROUND ONE HALF TO ONE INCH ARE EXPECTED FOR
MOST OF THE AREA.

SUNDAY...COASTAL TROUGHING PERSISTS WITH 700MB SOUTHWESTERLY FLOW
AND GOOD UPPER LEVEL SUPPORT PRODUCING A WET DAY WITH LOCALLY
ENHANCED SHOWERS WITH MODEST INSTABILITY FOR ELEVATED CONVECTION.
EXPECTING A MIX OF SOME STRATIFORM RAIN FROM ISENTROPIC PROCESSES
AND ENHANCED SHOWERS WITH A THUNDERSTORM OR TWO WHERE LOW TO MID
LEVEL CONVERGENCE IS STRENGTHENED. RAISED POPS TO NEAR 100 PERCENT
THROUGH THE DAY AS WELL. RAINFALL INTENSITY IS EXPECTED TO BE LOWER
HOWEVER.

SUNDAY NIGHT...UPPER LEVEL LOW APPROACHES SUNDAY NIGHT WITH GOOD
PRECIP CHANCES REMAINING IN PLACE. THERE IS SOME QUESTION AS TO THE
DIRECTION OF 850/700MB FLOW IN REGARDS TO FRONTAL OVERRUNNING AND
ISENTROPIC LIFT AS COMPARED TO SUNDAY BUT COASTAL TROUGHING REMAINS
STRONG OFFSHORE WITH ABUNDANT COLUMN MOISTURE. KEPT POPS A LITTLE
LOWER IN THE WEST WHERE LOW LEVEL FLOW IS EXPECTED TO BE MORE
OVERLAND AND A LITTLE DRIER BUT KEPT GENERALLY LIKELY POPS THROUGH
THE NIGHT. QPF AMOUNTS SHOULD BE A LITTLE LOWER DUE TO WEAKER
FORCING.  /68/

LONG TERM /MONDAY THROUGH SATURDAY/...
WET WEATHER WOES FROM THE SHORT TERM PORTION OF THE FORECAST WILL
LIKELY CONTINUE AS WE HEAD INTO THE LONG TERM.  HEADING INTO
MONDAY...WE`RE STILL FACED WITH AN UPPER-LEVEL TROUGH AXIS FROM
TEXOMA TO THE MEXICAN STATE OF CHIHUAHUA AND SURFACE TROUGHING JUST
OFFSHORE.

ODDS ARE...IT`S GOING TO RAIN MONDAY...ESPECIALLY OVER EASTERN
AREAS.  ISENTROPIC FIELDS AROUND THE 305K LEVEL INDICATE PLENTY OF
UPGLIDE CONTINUING OVER THE REGION AHEAD OF THE EASTWARD-MOVING
TROUGH.  ONE OF THE FEW FLIES IN THE OINTMENT (AT LEAST IN MY MIND)
IS INCREASING CONDENSATION PRESSURE DEFICITS...WHICH SHOULD DECREASE
THE OVERALL PRECIPITATION COVERAGE A BIT.  STILL THOUGH...WITH
PLENTY OF SYNOPTIC SCALE FORCING AND BROAD/DEEP LOW-LEVEL
MOISTURE...THE ODDS OF SEEING RAIN SHOULD REMAIN ABOVE AVERAGE
THROUGH MONDAY.

BY ALL INDICATIONS...IT LOOKS LIKE AN AREA OF PRECIPITATION WILL
MOVE NORTH/NORTHEASTWARD ACROSS THE FORECAST AREA DURING THE EARLY
MORNING HOURS MONDAY...WITH THE GREATEST ODDS OF SEEING
PRECIPITATION OVER THE NORTHERN AND EASTERN AREAS BY SUNRISE (OR SO)
MONDAY.  THIS TREND SHOULD GENERALLY CONTINUE THROUGH MUCH OF THE
DAY.

FORECAST SOUNDINGS APPEAR TO BE RELATIVELY UNCONDUCIVE FOR
THUNDERSTORM DEVELOPMENT MONDAY.  HOWEVER...I CANNOT DISCOUNT A
(RELATIVELY) ROGUE ELEVATED STORM OR TWO AS MID-LEVEL LAPSE RATES
STEEPEN AS THE UPPER TROUGH MOVES OVERHEAD.  GIVEN THIS...I PLAN ON
KEEPING THE MENTION OF THUNDERSTORMS CONFINED TO COASTAL REGIONS.

CONDITIONS SHOULD START TO IMPROVE BY MONDAY NIGHT AS THE UPPER
TROUGH AXIS SHIFTS EAST OF OUR REGION...AND PUSHES THE COASTAL
TROUGH FURTHER OFFSHORE.  A MORE SUBSIDENT WEST THEN NORTHWEST FLOW
ALOFT WILL AID IN ENDING ANY RAIN PROBABILITIES AS DRIER AIR ADVECTS
INTO THE FORECAST AREA.

ANOTHER SHORTWAVE TROUGH IS FORECAST TO MOVE FROM THE CENTRAL PLAINS
TO THE MIDSOUTH AT MID-WEEK.  THIS SHOULD PUSH ANOTHER COLD FRONT
THROUGH OUR AREA AROUND MIDDAY WEDNESDAY.  BECAUSE OF THE SHORT TIME
SPAN BETWEEN THESE TWO STORM SYSTEMS...THERE SHOULD NOT BE ENOUGH
TIME FOR ANY SORT OF RETURN FLOW TO DEEPEN LOW-LEVEL MOISTURE.  THAT
SAID...THIS FRONT`S MAIN IMPACT SHOULD BE IN THE TEMPERATURE
DEPARTMENT AS A SLIGHT COOLDOWN IS EXPECTED FOR THE END OF THE
UPCOMING WEEK.

THERE ARE A FEW DISCREPANCIES SHOWING UP IN THE MODEL WORLD FOR
FRIDAY AND SATURDAY.  A NEARLY ZONAL FLOW ALOFT SHOULD PUSH SURFACE
HIGH PRESSURE EASTWARD...ALLOWING EAST TO SOUTHEAST WINDS TO RETURN
BY WEEK`S END.  IN GENERAL...IT LOOKS LIKE DRY CONDITIONS SHOULD BE
SEEN HEADING INTO NEXT WEEKEND.  /BUTTS/

MARINE...

TONIGHT THROUGH SUNDAY NIGHT...
MODERATE EAST TO SOUTHEAST WINDS WILL SLACKEN IN THE EARLY EVENING
AHEAD OF A COLD FRONT EXPECTED TO SWEEP ACROSS THE LOWER TEXAS COAST
TONIGHT BY AROUND MIDNIGHT. COASTAL TROUGHING WILL DEVELOP IN THE
WAKE OF THE FRONT AND PERSISTENT RAIN WITH EMBEDDED SHOWERS AND
THUNDERSTORMS ARE EXPECTED THROUGH SUNDAY NIGHT. WINDS FROM THE
NORTH TO NORTHEAST AT 18 TO 23 KNOTS ARE LIKELY THROUGH SUNDAY NIGHT
BUT THE PRESENCE OF THE TROUGHING SHOULD KEEP A MORE PRONOUNCED
BLAST OF NEAR GALE FORCE GUSTS OR OTHER SIMILAR CONDITIONS AT BAY
DURING THIS FRONTAL PASSAGE. NEVERTHELESS SMALL CRAFT ADVISORIES
WILL LIKELY BE NEEDED FROM THIS EVENING THROUGH SUNDAY NIGHT.  /68/

MONDAY THROUGH THURSDAY...
RAIN WILL LIKELY CONTINUE THROUGH MONDAY NIGHT OVER THE MARINE AREA
(ESPECIALLY THE GULF OF MEXICO WATERS) THANKS TO THE PRESENCE OF A
COASTAL TROUGH.  PRECIPITATION IS EXPECTED TO DIMINISH IN COVERAGE
TUESDAY MORNING WITH THE DEPARTURE OF THE STORM SYSTEM.  HIGH
PRESSURE SHOULD THEN DOMINATE THE MARINE AREA THROUGH MID-WEEK...
PROVIDING DRY WEATHER CONDITIONS.

EXPECT IMPROVING WINDS/SEAS MONDAY...WITH SEAS UNDER 4 FEET AND WIND
SPEEDS UNDER 10 KNOTS BY MONDAY NIGHT.  WINDS SHOULD BRIEFLY BECOME
SOUTHERLY TUESDAY AHEAD OF THE NEXT COLD FRONT...WHICH SHOULD MOVE
THROUGH THE MARINE AREA BY WEDNESDAY AFTERNOON.  BREEZY NORTH WINDS
SHOULD RETURN IN WAKE OF THIS FRONT.  /BUTTS/

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY FOR WINDS FROM 4 AM TO NOON CDT SUNDAY FOR
     GMZ130-132-135.

     SMALL CRAFT ADVISORY FROM 4 AM TO NOON CDT SUNDAY FOR GMZ150-155-
     170-175.

&&

$$

THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT:
HTTP://WEATHER.GOV/RGV

54/67/MARTINEZ