Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 070023 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
623 PM CST FRI MAR 6 2015

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

.AVIATION...SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATED
MID TO HIGH LEVEL CLOUDS ACROSS THE CWA EARLY THIS EVENING.
CEILINGS WERE BETWEEN 6500FT AND 7500FT ACROSS MOST OF THE AREA.
VISIBILITIES WERE NEAR 5SM WITH HAZE AT KT65 TO NEAR 6SM WITH HAZE
AT KPIL. EXPECT VFR CONDITIONS TO PREVAIL THE REST OF THE EVENING
INTO EARLY SAT MORNING AS SURFACE HIGH PRESSURE ACROSS EAST TEXAS
EXTENDING SOUTHWEST ACROSS THE RIO GRANDE PLAINS CONTINUES TO
PROVIDE DRY AIR AT THE SURFACE WHILE SOUTHWEST FLOW ALOFT
CONTINUES TO BRING MID TO UPPER LEVEL MOISTURE ACROSS THE AREA.
&&

.PREV DISCUSSION... /ISSUED 238 PM CST FRI MAR 6 2015/
SHORT TERM /NOW THROUGH SATURDAY NIGHT/... RELEVANT
FEATURES...THE RIGHT REAR QUADRANT OF A JET MAX SPREAD OUT OVER
MUCH OF THE NORTHERN GULF COAST IS PERSISTING OVER THE AREA...THIS
IS HELPING WORK WITH AVAILABLE MID LEVEL MOISTURE TO PRODUCE A FEW
ELEVATED SHOWERS OVER SOUTHEASTERN CAMERON COUNTY AND GENERAL MID
LEVEL CLOUDINESS OVER MOST OF THE REST OF DEEP SOUTH TEXAS. A WEAK
UPPER LEVEL LOW IS MOVING OVER NORTHEASTERN MEXICO BUT IT SHOULD
MOVE WELL TO THE NORTH OF THE AREA LATER TONIGHT. NEAR THE SURFACE
HIGH PRESSURE IS FILLING IN RESPONSE TO UPPER CONVERGENCE BEHIND
THE AFOREMENTIONED JET MAX. RATHER DRY AIR IS PRESENT IN THE
LOWEST FEW THOUSAND FEET OF THE ATMOSPHERE AS A RESULT OF SEVERAL
DAYS OF NORTHERLY WINDS AND DRY/COLD AIR ADVECTION.

TONIGHT...NORTHERLY WINDS WILL GRADUALLY SHIFT TO THE EAST AS
SURFACE HIGH PRESSURE MIGRATES NORTHEASTWARD. WITH LITTLE SURFACE
MOISTURE IN THE WESTERN GULF TO WORK WITH THIS SHOULD ALLOW
SURFACE DEWPOINTS TO SAY PRETTY LOW TONIGHT. PERSISTENT MID LEVEL
OVERCAST WILL LIKELY SEE A FEW BREAKS BUT COMBINED WITH LIGHT TO
MODERATE EAST WINDS TEMPERATURES WILL PROBABLY ONLY FALL INTO THE
LOW TO MID 40S.

SATURDAY...LOW LAYER RIDGING WILL SHIFT FURTHER TO THE EAST AND
AN ADVANCING SHORTWAVE TROUGH OVER THE SOUTHWEST US WILL HELP
CREATE RELATIVELY STRONG SOUTHERLY FLOW AT 850MB. MODEST
ISENTROPIC LIFT WILL BE OCCURRING IN THIS LAYER AND IT SHOULD
HELP GENERATE QUITE A BIT OF CLOUD COVER. SURFACE MOISTURE RETURN
WILL ALSO BEGIN TO INCREASE AS EASTERLY WINDS THERE START TO TAP
A LITTLE RICHER GULF MOISTURE. DOWNSLOPING 750MB VICINITY WINDS
THOUGH SHOULD KEEP RELATIVELY STRONG CAPPING/DRYING IN PLACE IN
THE MID LEVELS AND KEPT THE FORECAST DRY. TEMPERATURES SHOULD BE
WARMER THAN THE LAST FEW DAYS BUT LIMITED OVERALL BY CLOUD COVER
AND SOMEWHAT COOL ONSHORE FLOW. HIGHS LOOK TO BE IN THE LOW TO MID
60S.

SATURDAY NIGHT...THE AFOREMENTIONED SHORTWAVE TROUGH WILL BE
MOVING INTO WEST TEXAS/NORTH CENTRAL MEXICO SATURDAY NIGHT. THIS
IS JUST SLIGHTLY SLOWER THAN PREVIOUS MODEL CONSENSUS. MID LEVEL
LAPSE RATES WILL LIKELY BEGIN STEEPENING DURING THE NIGHT BUT LOW
LEVEL CONVERGENCE LOOKS TO REMAIN LOW AMID A RESIDUAL TERRAIN
INDUCED INVERSION AROUND 750MB AND HAVE DELAYED THE ONSET OF
HIGHER PRECIP CHANCES AS A RESULT. THE 30PCT POPS NOW COVER ABOUT
THE WESTERN QUARTER OF THE AREA FOR SIERRA MADRE INITIATED
THUNDERSTORMS...AND THE GULF AND IMMEDIATE COAST FOR SHOWERS
POPPING UP OVER THE INCREASINGLY UNSTABLE GULF. /68-JGG/

LONG TERM /SUNDAY THROUGH THURSDAY/...THE MAIN FEATURES NOW IN
PLACE WILL EVOLVE SLOWLY AS FOLLOWS...BROAD TROUGHING OVER THE
NORTHEAST...A RIDGE ALONG THE WEST COAST...SOME FORM OF MID LEVEL
LOW AND OR TROUGH OVER THE SOUTH WEST...NORTH MEXICO AND TEXAS...
AND A BUILDING RIDGE OVER FLORIDA AND THE SOUTHEAST.

THE MID LEVEL LOW OVER NORTH BAJA WILL DRIFT SLOWLY EAST IN THE
SHORT TERM...AND SHOULD BE IN RANGE TO PROVIDE LIFT/INSTABILITY TO
THE DOWNSTREAM PATTERN...TRIGGERING SOME CONVECTION COMING OFF THE
SIERRAS SATURDAY NIGHT. FURTHER ACTION SEEMS TO BE DIRECTED A BIT
NORTH OF THE CWA HOWEVER...OVER THE RIO GRANDE PLAINS SUNDAY. A BIT
BETTER FOCUS OCCURS AS THE TROUGH AXIS DIPS OVER WEST TEXAS SUNDAY
NIGHT...WITH SOLID SOUTHEAST INFLOW FROM THE GULF CONVERGING WITH
NORTHEAST FLOW INLAND. CONVECTIVE CHANCES WILL BE HIGHER OVER THE
BIG BEND UNDER THE BASE OF THE TROUGH BUT ALSO AHEAD OF IT UNDER
DIVERGENT UPPER FLOW ALL ALONG THE TEXAS COAST SUNDAY NIGHT.

THE GFS AND ECMWF BOTH SUPPORT THE UPSTREAM LOW EJECTING OUT TO
WEST TX BY SUNDAY...WITH DIVERGENCE AT THE MID LEVEL INDUCING
INSTABILITY OVER NORTHEAST MEXICO AND THENCE DEEP SOUTH TEXAS.
RAIN CHANCES WILL REMAIN ROBUST FROM SATURDAY SUNDAY THROUGH
MONDAY AS THE TROUGH EDGES SLOWLY EAST TOWARD WEST AND CENTRAL
TEXAS...WITH THE ADDED SUPPORT OF ADDITIONAL HIGH PRESSURE
REGENERATING OVER THE OHIO VALLEY AND MAKING ITS WAY BACK TOWARD
EAST TEXAS. NORTHEAST WINDS WILL STRENGTHEN SUNDAY NIGHT INTO
MONDAY...AS WILL RAIN CHANCES OVER THE NORTHWEST GULF EXTENDING
BACK TOWARD THE LOWER TEXAS COAST. HIGH TEMPS SUNDAY WILL BE IN
THE MID TO UPPER 60S WITH LOWS SUNDAY NIGHT 55 TO 65.

TEMPERATURES WILL STABILIZE A BIT BELOW NORMAL THROUGH WEDNESDAY
WITH SUBSTANTIAL CLOUD COVER WITH NEAR NORMAL TEMPERATURES NOT
REALLY BACK UNTIL THURSDAY. SLIGHT RAIN CHANCES WILL CONTINUE FOR
THE MARINE AREAS AND COASTAL COUNTIES THROUGH MID WEEK AS THE MID
LEVEL TROUGH WILL BE SLOW TO EJECT. WEST COAST RIDGING WILL TOPPLE
EAST TOWARD THE FOUR CORNERS... HELPING TO TRAP THE UPPER WEAKNESS
OVER NORTH CENTRAL MEXICO. THE RELATED DOWNSTREAM DIVERGENCE WOULD
SUPPORT PRESSURE DECREASES OVER THE WEST GULF WHILE HIGHER PRESSURE
STILL CONTROLLED THE NORTH GULF...LEADING TO A BROAD INVERTED TROUGH
AND NORTHEAST TO NORTH WINDS OFFSHORE...LOCKING IN LOW LVL MOISTURE
AND THE ASSOCIATED COOL...CLOUDY CONDITIONS.

MARINE...
NOW THROUGH SATURDAY NIGHT...SLOWLY IMPROVING MARINE CONDITIONS
ARE FORECAST THROUGH THE REST OF THE AFTERNOON AND TONIGHT. A
SMALL CRAFT ADVISORY REMAINS IN EFFECT THROUGH EARLY THIS EVENING
WITH EXERCISE CAUTION LEVEL SEAS POSSIBLE THROUGH MOST OF THE
NIGHT TONIGHT. BETTER CONDITIONS ARE FORECAST SATURDAY AND
SATURDAY NIGHT AS MODERATE EAST WINDS DEVELOP OVER ALL WATERS.
SEAS WILL REMAIN MODERATE THROUGH SATURDAY NIGHT.

SUNDAY THROUGH TUESDAY...HIGH PRESSURE OVER THE NORTHWEST GULF
WILL RESULT IN LIGHT TO MODERATE EAST WINDS LOW TO MODERATE SEAS.
THE APPROACH OF A MID LEVEL TROUGH FROM THE WEST AND A STRONGER
PRESSURE GRADIENT OVER THE NORTHWEST GULF WILL RESULT IN STRONGER
NORTHEAST WINDS BY MONDAY...AND MORE UNSETTLED WEATHER. THE
STRONGER WINDS WILL REACH SMALL CRAFT EXERCISE CAUTION CONDITIONS
ON THE GULF MONDAY TO TUESDAY...WITH SEAS ALSO BUILDING INTO THE
FOUR TO SIX FT RANGE. THE POSSIBLE DEVELOPMENT OF AN INVERTED
SURFACE TROUGH FARTHER OFF SHORE EARLY IN THE WEEK WILL CONTRIBUTE
TO A TIGHTER GRADIENT...ALSO HELPING TO KEEP THE NORTH TO
NORTHEAST WINDS A BIT STRONGER.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR GMZ150-155-
     170-175.
&&

$$

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