FXUS64 KBRO 251944
AFDBRO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
144 PM CST FRI DEC 25 2009
.DISCUSSION...BKN-OVC250 SO FAR TODAY HAS INHIBITING WARMING. AT 1
PM...TEMPERATURES REMAINED IN THE LOW AND MID 50S AND SHUD JUMP TO
NEAR 60 BY 4 PM TDY. SFC WNDS WILL CONTINUE TO VEER TO THE SOUTHEAST
OVERNIGHT. OVRRNG PCPN WILL DEVELOP AS OUR COOLER DENSE AIR AT THE
SFC LIFTS SW FLOW OF AIR FM H850-H7. RAINFALL AMOUNT SHUD REMAIN
UNDER 0.05 INCH WITH ANY HEAVIER SHRA ACTIVITY CONFINED TO OUR GULF
WATERS. THE MAIN WX-MAKER...AN UPPER LOW NOW OVR MO...WILL SLOWLY
DRIFT TO THE GREAT LAKES...ALLOWING ADDITIONAL WEAK ENTRY OF DRIER
AIR SUNDAY IN A NORTH SFC FLOW. SW FLOW IN MID LVLS MON THRU WED
WILL KEEP CLOUDS AROUND...TEMPS DOWN (HIGHS 60/LOWS 47) IN OVC SKIES
AND GENERALLY WEAK NORTHERLY SFC FLOW. THE SECOND OVRRNG EVENT
TUESDAY SHUD BRING RAINFALL TOTALS OF ONE TENTH TO ONE QUARTER OF AN
INCH TUESDAY AFTERNOON...HIEST TOTALS OVR NRN COUNTIES. BRO IS
RUNNING RAINFALL DEFICITS OF 1.29 INCH FOR THE YEAR 2009...AND WE'LL
APPROACH NORMS IN RAINFALL BY YEAR'S END.
&&
.MARINE...CONDITIONS GRADUALLY IMPROVING OFFSHORE THIS AFTERNOON AS
WINDS HAVE DROPPED BELOW 20 KNOTS AND SEAS HAVE DIPPED JUST BELOW 7
FEET AT BUOY 42020. GIVEN HIGHER SEAS OFFSHORE (11 TO 12 FEET AT
200 NM) AND POSSIBILITY THAT SOME 8 FOOT HEIGHTS ARE STILL OCCURRING
TOWARD THE 60 NM MARKER WILL LET ADVISORY RIDE THROUGH 4
PM...EXPECTING IT TO DROP THEREAFTER AS SURFACE WINDS VEER TOWARD
THE NORTHEAST/EAST WITH HIGH PRESSURE RIDGE AXIS MOVING BY.
OTHERWISE...A QUIET NIGHT FOR THE LAGUNA AND EVENTUALLY THE
NEARSHORE WATERS AS WINDS VEER TO THE EAST AND REMAIN RATHER
LIGHT...LESS THAN 15 KNOTS OFFSHORE AND 5 TO 10 KNOTS IN THE
LAGUNA/NEARSHORE.
THINGS GET A LITTLE TRICKY SATURDAY. BOTH GFS...AND NAM TO A LESSER
DEGREE...TRY TO DEVELOP COASTAL TROUGH VERY CLOSE TO THE SHORELINE.
FIND THIS A HARD SELL SINCE SURFACE AIR MASS WILL NOT RECOVER MUCH
AHEAD OF THE APPROACHING JET ENERGY ALOFT. WITH NEARSHORE WATERS IN
THE COOL 60 DEGREE RANGE...THE COASTAL TROUGH WOULD TEND TO FORM AT
THE CLOSEST SOME 40-50 NM OFFSHORE. THEREFORE...HAVE SHADED WIND
DIRECTION FROM SOUTHEAST BEYOND THAT POINT TO EAST CLOSER IN...AND
NORTH TO NORTH/NORTHEAST ACROSS THE LAGUNA WHICH WILL REMAIN IN THE
TRAPPED COOL AIRMASS. SPEEDS SHOULDN'T BE MUCH OF AN ISSUE SATURDAY
THOUGH SOME INCREASE IS EXPECTED BY LATE AFTERNOON AS UPPER ENERGY
PULLS OFFSHORE AND DEVELOPS THE SURFACE FEATURE FARTHER
OFFSHORE...WITH WINDS SHIFTING BACK TO THE NORTH ACROSS ALL THE
WATERS AND NEARING CAUTION LEVELS.
THE WAVE GETS GOING SATURDAY NIGHT IN THE CENTRAL GULF AND
REINFORCING HIGH PRESSURE NOSES INTO SOUTH TEXAS...TIGHTENING THE
GRADIENT. IN THIS SEASON OF EL NINO EXPECT WINDS AND SEAS TO
RATCHET UP QUICKLY...WITH 20 TO 25 KNOT NORTHERLIES AND SEAS
BUILDING BACK TO 8 FEET FOR MANY. THESE CONDITIONS WILL HOLD RIGHT
INTO SUNDAY AND MONDAY AS FAIRLY STRONG SURFACE HIGH ANCHORS IN
ACROSS THE UPPER VALLEY...MAINTAINING TIGHT PRESSURE GRADIENT ACROSS
THE WATERS. PERSISTENT PATTERN COULD KICK UP SWELL PERIOD TOWARD
9/10 SEC IN TIME AND SEAS COULD REACH 10 FEET BUT FOR NOW WILL CAP
AT 9 FEET INTO MONDAY AND BEYOND.
NEXT WAVE APPROACHES TUESDAY AND TUESDAY NIGHT WITH ANOTHER COASTAL
SYSTEM DEVELOPING. DIFFICULT TO PINPOINT EXACTLY WHERE THE
TROUGH/LOW WILL FORM BUT FOR NOW HAVE MAINTAINED WINDS NEAR 20 KNOTS
AND ONLY VEERED GRADUALLY FROM NORTHEAST TO EAST. GRADIENT COULD
SLACKEN SOME BEHIND THIS WAVE NEXT WEDNESDAY...BUT CONFIDENCE FAIRLY
LOW AT THIS POINT SO WILL MAINTAIN SOMEWHAT DIFFICULT CONDITIONS TO
THE END OF THE PERIOD.
IN SUMMARY...ENJOY THE BRIEF RESPITE FROM WINDS AND SEAS/SWELL
THROUGH SATURDAY AS IT LOOKS LIKE PROLONGED SMALL CRAFT ADVISORY
CONDITIONS THEREAFTER...WITH CAUTION CONDITIONS EDGING CLOSE TO
ADVISORY (WINDS) ACROSS THE LAGUNA.
&&
.AVIATION...GOOD FLYING DAY CONTINUES...THOUGH ALTOSTRATUS OVERCAST
HAS FORMED ACROSS THE LOWER AND MID VALLEY AT 6K FEET QUITE A BIT
SOONER THAN EXPECTED. NOT SURE HOW LONG THIS WILL HOLD THIS
AFTERNOON/EVENING...AS THERE ARE BREAKS TO OUR SOUTH AND WEST...AND
CIRRUS ABOVE 20K FEET COULD RETURN FOR AWHILE.
LOWER CLOUDS SHOULD ARRIVE IN EARNEST AFTER MIDNIGHT...STILL
VFR...BUT MVFR CONDITIONS WILL FOLLOW QUICKLY TOWARD OR JUST AFTER
DAYBREAK AS NEXT SYSTEM FORMS UP. IFR CEILING A POSSIBILITY BY
SATURDAY AFTERNOON BUT HAVE HELD MVFR FOR NOW OWING TO VERY LOW WET
BULB TEMPERATURES AT AND JUST ABOVE THE SURFACE TO START...WHICH
WOULD TEND TO NEED TIME TO MOISTEN UP. BEGAN RAINS AS TEMPO GROUPS
BY MID MORNING NEAR THE COAST WITH JUST A PROB30 FOR NOW AT KMFE.
WINDS WILL NOT BE AN ISSUE THROUGH 18Z/DEC 26 BUT SURFACE DIRECTION
LOOKS TO BE LIGHT/NORTH FROM 12-18Z...QUICKLY TURNING
SOUTH/SOUTHEAST NOT TOO FAR OFF THE DECK.
&&
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 49 67 52 66 / 20 30 0 0
BROWNSVILLE 50 67 49 67 / 20 30 0 0
HARLINGEN 46 62 49 66 / 20 30 0 0
MCALLEN 46 61 48 66 / 20 10 0 0
RIO GRANDE CITY 42 60 43 65 / 0 0 0 0
SOUTH PADRE ISLAND 47 65 51 66 / 20 30 0 0
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 4 PM CST THIS AFTERNOON FOR GMZ170-
175.
&&
$$
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