Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 032046
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
246 PM CST TUE MAR 3 2015

.SHORT TERM /NOW THROUGH WEDNESDAY NIGHT/...
MAJOR WESTERN TROUGH IS BEGINNING TO MAKE ITS PRESENCE FELT WITH
RAPIDLY INCREASING SOUTHERLY FLOW AND WARMER TEMPS GRADUALLY
SPREADING WESTWARD FROM THE COAST. ALREADY AS OF 1 PM THE TEMP IN
BROWNSVILLE HAS EXCEEDED 80 DEGREES. THE WARM FRONT IS MAKING SLOW
WESTWARD PROGRESS AND SHOULD BE THROUGH MUCH OF THE CWA BY 5 PM.
TEMPERATURES MIGHT CONTINUE TO WARM AN HOUR OR SO AFTER SUNSET
BEFORE DIURNAL COOLING KICKS IN.

TONIGHT...SURFACE INVERSION REESTABLISHES ITSELF A FEW HOURS AFTER
SUNSET WITH A BRISK LOW LEVEL JET OF 30-40KNOTS  DEVELOPING IN
RESPONSE LOWERING PRESSURE AND SURFACE TROUGHING ACROSS THE LEE OF
THE SIERRA MADRE WARMING THE BOUNDARY LAYER. STRATUS TO QUICKLY
REFORM AND WITH THE CONTINUED MIXING OF WINDS OVERNIGHT LOW
TEMPERATURES WILL BE MUCH WARMER WITH ANY ADDITIONAL COOLING SLOWED
DOWN.

WEDNESDAY...THE VENGEANCE OF THE RGV WIND MACHINE AND WARMING WILL BE
IN FULL SWING. MODELS IN GOOD AGREEMENT WITH DEEPENING SURFACE
TROUGH OVER THE LEE OF THE SIERRAS. SURFACE TO 850MB WINDS TO VEER S-
SW-W THIS IS GOOD SIGNAL FOR DOWNSLOPING CONDITIONS. MODEL GUIDANCE
RESPONDS NICELY WITH MID TO UPPER 80S AND EVEN SOME LOCATIONS
TOUCHING 90 DEGREES. INHERITED FORECAST REFLECTS THIS WELL AND WILL
MAINTAIN CURRENT NUMBERS. ANY LOW CLOUDS AND LIGHT FOG, FOG NEAR THE
COAST AND OFFSHORE, TO QUICKLY BURN OFF AND LIFT WITH A MOSTLY SUNNY
TO PARTLY CLOUDY AFTERNOON SKY. SURFACE WINDS AS MENTION BECOME
BREEZY TO WINDY AS TEMPERATURE AND PRESSURE GRADIENT FROM COAST TO
SIERRA STRENGTHENS.

WEDNESDAY NIGHT...THE BRIEF WARMING TREND TO QUICKLY GO INTO
REVERSE AS THE MUCH ADVERTISED ARCTIC FRONT BARRELS THROUGH THE
CWA AFTER MIDNIGHT. STRONG NORTHERN JET MOVING SOUTH THROUGH THE
NORTHERN ROCKIES TO PHASE WITH THE SUBTROPICAL JET OVER THE
SOUTHWEST AND CENTRAL PORTIONS OF THE COUNTRY. THIS WILL DRIVE THE
ARCTIC HIGH SOUTHWARD RAPIDLY INCREASING THE FORWARD SPEED OF THE
COLD AIR. MODELS IN GOOD AGREEMENT ON THE TIMING OF THE FRONT
ENTERING THE NORTHERN RANCH LANDS BY MIDNIGHT AND THROUGH THE
LOWER VALLEY BY 4 AM. RAPID FORCING OF THE DEEP LAYER COLD AIR
OVER THE WARM MOIST LAYER TO ALLOW FOR QUICK DEVELOPMENT OF
SHOWERS AND A POSSIBLE THUNDERSTORM OR TWO IN WAKE OF THE FRONT.
GRADIENT IMMEDIATELY BEHIND THE FRONT IS VERY TIGHT SO FRONTAL
PASSAGE WILL BE FELT BY STRONG GUSTY NORTH WINDS AND RAPIDLY
FALLING TEMPERATURES. MODELS GUIDANCE SHOWS A DROP OF 30+ DEGREES
IN 9 HOURS BETWEEN MIDNIGHT AND 9 AM AT BROWNSVILLE. THIS WILL
LIKELY OCCUR WITHING A 3 HOUR TIME PERIOD WITH THE FRONT EXPECTED
TO MOVE THROUGH BROWNSVILLE AT 4 AM GIVE OR TAKE AN HOUR. THIS
SCENARIO IS HIGHLY PROBABLE FOR ALL LOCATIONS WITHIN THE CWA.

.LONG TERM /THURSDAY THROUGH MONDAY/...A SIGNIFICANT COLD SNAP IS
ON TRACK TO IMPACT THE AREA FROM WEDNESDAY NIGHT INTO THURSDAY AND
BEYOND. A PROGRESSIVE MID LEVEL TROUGH WILL BE LIFTING OVER THE
GREAT LAKES THURSDAY...HAVING FAILED TO COMPLETELY PHASE WITH THE
SOUTHERN CALIFORNIA MID LEVEL FEATURE. HENCE...AS COLD SURFACE
HIGH PRESSURE SPREADS OVER THE CWA THURSDAY...BROAD TROUGHINESS
WILL REMAIN TO THE WEST...PROLONGING SOUTHWEST FLOW ALOFT AND
ENSURING AN OVER RUNNING PATTERN THAT LASTS INTO THE WEEKEND.
EVEN THOUGH THE TROUGH TO THE WEST WILL FILL OVER THE WEEKEND...A
WEAKNESS WILL REMAIN OVER NW MEXICO...PREVENTING THE MID LEVEL
FLOW FROM VEERING SIGNIFICANTLY...AND THE HOPES OF ANY SIGNIFICANT
AMOUNT OF SUNSHINE BEFORE EARLY NEXT WEEK WILL HAVE TO BE PUT ON
HOLD FOR A TIME.

IN THE WAKE OF THE FRONT AN ARCTIC SOURCE AIRMASS WILL SETTLE OVER
DEEP SOUTH TEXAS THURSDAY THROUGH SATURDAY. ALTHOUGH CAA WILL NOT
RESULT IN ANY FREEZING TEMPS AT THIS TIME...NORTH WINDS ALONG THE
COAST HAVE A CHANCE OF TOUCHING WIND ADVISORY CRITERIA FOR A FEW
HOURS THURSDAY MORNING. THE COMBINATION OF THE SUSTAINED CAA AND
STRONG NORTHERLY FLOW WILL ALSO SET THE STAGE FOR A PERIOD OF
ADVISORY CRITERIA WIND CHILL VALUES THURSDAY THROUGH EARLY FRIDAY.

MADE SLIGHT ADJUSTMENTS TO TEMPS ON THURSDAY...FOLLOWING GUIDANCE
TO KEEP THE SLOW TEMPERATURE DROP GOING THROUGH THE MORNING INTO
THE EARLY AFTERNOON HOURS...AFTER WHICH A RECOVERY OF A COUPLE OF
DEGREES MAY ALLOW AFTERNOON TEMPS TO GET BACK TO THE SAME READINGS
AS AT THE BEGINNING OF THE DAY. IT IS POSSIBLE THAT THE HIGH FOR
THE DAY MAY OCCUR AT DAWN HOWEVER. ALSO BACKED OFF ON HIGHER POPS
AFTER THE INITIAL SURGE. LIGHT RAIN STILL IN THE CARDS BUT QPF
AMOUNTS SHOULD BE LIGHT. THE ISENTROPIC LIFT IN THE WAKE OF THE
FRONT WILL GENERATE THICK LOW CLOUDS AT THE LEAST...HOWEVER.

THE SUSTAINED CAA WILL ALSO BE HELPED ALONG BY PERSISTENT COASTAL
SURFACE TROFFING IN THE WAKE OF THE FROPA...WHICH WILL MAINTAIN
THICK LOW LEVEL CLD COVER AND PERSISTENT POPS LASTING INTO THE
WEEKEND. THE COASTAL TROFFING WILL LIKELY LOOSEN ITS GRIP OVER DEEP
SOUTH TEXAS LATER THIS WEEKEND. BUT THE DISSIPATION OF THIS SURFACE
FEATURE WILL THEN BE FOLLOWED QUICKLY BY THE BAJA CALIFORNIA 500 MB
LOW OPENING UP AND MOVING EAST OVER TEXAS SUNDAY AND MONDAY. THE
COMBINATION OF THIS SERIES OF 500 MB AND SURFACE LOWS/TROUGHS WILL
HOLD CLOUD COVER AND RAIN CHANCES IN PLACE INTO THE WEEKEND...
TENDING TO HOLD OFF ANY SERIOUS WARMING THROUGH THE EXTENDED RANGE
PERIOD.

PRETTY GOOD AGREEMENT SHOWS UP BETWEEN THE GFS AND ECMWF THROUGH
AROUND FRIDAY. SLIGHT DIFFERENCES THEN SHOW UP AS THE TWO MODELS
WRESTLE WITH THE DETAILS OF THE LOW LATITUDE TROUGHING MOVING
ACROSS FROM THE WEST. THE DIFFERENCES DON`T SEEM TO TRANSLATE INTO
ANY BIG ISSUES THROUGH THE END OF THE ADVERTISED FORECAST...BUT
COULD HAVE MORE RELEVANCE DEEPER INTO NEXT WEEK.

&&

.MARINE...
NOW THROUGH WEDNESDAY NIGHT...RELATIVELY MILD CONDITIONS ARE
EXPECTED ACROSS THE LAGUNA MADRE AND THE GULF WATERS AS SOUTHERLY
WINDS FINALLY RETURN. THE ONSHORE FLOW TO INCREASE SOMEWHAT
OVERNIGHT ESPECIALLY OFFSHORE AS PRESSURES CONTINUE TO LOWER
INLAND. THE COOLER WATER SHOULD LIMIT THE WIND POTENTIAL BUT
MARGINAL SMALL CRAFT ADVISORY LEVELS ARE LIKELY MAINLY OVER THE
OUTER WATERS. MARINERS ARE URGED TO FINISH ANY BUSINESS EARLY
WEDNESDAY AS A MAJOR COLD FRONT IS STILL ON TRACK FOR AFTER
MIDNIGHT WEDNESDAY NIGHT. GALE WATCHES ARE POSTED AND WILL LIKELY
BE UPGRADED TO WARNING LATER TONIGHT OR FIRST THING WEDNESDAY. THE
SHARP FRONT BARRELS THROUGH THE NORTHERN COASTAL WATERS BETWEEN
MIDNIGHT AND 2 AM THEN THE SOUTHERN WATERS WILL SEE THE SURGE
BETWEEN 2 AND 5 AM. LIGHT SOUTHERLY WINDS TO QUICKLY SWITCH TO
GALE FORCE WINDS WITH RAPIDLY BUILDING SEAS.

THURSDAY THROUGH SATURDAY...STRONG NORTH WINDS WITH GALE FORCE GUSTS
ARE STILL EXPECTED THURSDAY IN THE WAKE OF A STRONG COLD FRONT WITH
ARCTIC ORIGINS. GALES WILL ALSO OCCUR ON THE LAGUNA MADRE...BUT
WINDS MAY WEAKEN A BIT EARLIER THERE...MID THURSDAY...THAN ON THE
OPEN GULF. SEAS ON THE GULF WILL BUILD TO 12 FEET DURING THE DAY.
THE PRESSURE GRADIENT WILL BEGIN TO RELAX THURSDAY NIGHT AS THE
COLD AIR MASS SLOWLY SPREADS OVER THE AREA. THE REMAINDER OF THE
LONG TERM MARINE FCST WILL CONSIST OF SLOWLY IMPROVING CONDITIONS IN
THE WAKE OF THE COLD FRONT. THOUGH WINDS WILL DECREASE BELOW 20 KTS
BY MID FRIDAY MORNING...WAVE HEIGHTS ON THE GULF MAY REMAIN AT OR
ABOVE SEVEN FEET INTO SATURDAY.

&&

.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL  67  80  42  42 /  10  10  50  60
BROWNSVILLE          66  84  39  40 /  10  10  50  60
HARLINGEN            68  85  39  39 /  10  10  60  60
MCALLEN              67  87  38  38 /  10  10  60  50
RIO GRANDE CITY      64  88  40  40 /  10  10  60  40
SOUTH PADRE ISLAND   66  71  46  46 /  10  10  50  60

&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...GALE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY EVENING
     FOR GMZ130-132-135-150-155-170-175.

&&

$$

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

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