Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 222344
AFDBRO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BROWNSVILLE TX
644 PM CDT WED APR 22 2015

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

&&

.AVIATION...MOISTURE CONTINUES TO ADVECT FROM THE SOUTHEAST
UNDERNEATH INVERSION LOCATED AROUND 1500 FEET. TABULAR DATA AS
WELL AS SHORT RANGE MODELS SHOW MVFR DEVELOPING EARLY THIS EVENING
WITH IFR CONDITIONS OVERSPREADING THE TERMINALS AFTER 06Z. WITH
HIGH PRESSURE NEARBY WINDS WILL GENERALLY BE FROM THE SOUTHEAST
AND SPEEDS BELOW 12 KNOTS. CIGS WILL LIFT BACK TO MVFR BY MID
MORNING WITH VFR CONDITIONS AROUND NOON THURSDAY.

&&

.PREV DISCUSSION... /ISSUED 308 PM CDT WED APR 22 2015/

SHORT TERM /NOW THROUGH THURSDAY NIGHT/...MID LEVEL RIDGE WILL
BUILD OVER TEXAS NEXT 24 HOURS AS MID LEVEL TROUGH/LOW DEEPENS
OVER SOUTHERN CALIFORNIA AND THEN BEGINS TO EJECT. RIDGE WILL THEN
SHIFT EAST BUT IN THE MEAN TIME THE UPPER PATTERN OVER THE
SOUTHWEST U.S. WILL AMPLIFY. SOUTHEAST SFC INFLOW SUPPORTED BY
BROAD HIGH PRESSURE OVER THE GULF AND SOUTHEAST U.S. WILL MAINTAIN
A RICH LOW LEVEL MOISTURE FEED WHILE SOUTHWEST FLOW ALOFT WILL
INITIALLY PROVIDE A STABILIZING CAP AND SUBSIDENCE. OVER TIME
HOWEVER...SUBSIDENCE WILL HELP DAY TIME SURFACE TEMPERATURES
WARM...AND ENERGY MOVING AROUND THE BASE OF THE EJECTING TROUGH
WILL TAP INTO THE LOWER LVL ENERGY TO HELP TRIGGER CONVECTION TO
THE WEST AND NORTH.

FOR THIS EVENING AND TONIGHT...ONGOING CONVECTION TO THE NORTH OF
THE CWA WILL WANE AND SHOULD NOT PLAY A MAJOR ROLE FOR THE CWA. LOW
TEMPS WILL BE IN THE 70S WITH OVC SKIES AND LIGHT SOUTHEAST WINDS.

ON THURSDAY...A MARGINAL RISK AREA WILL CONTINUE OVER THE AREA. HIGH
TEMPS WILL PUSH INTO THE LOWER 90S WEST OF THE COASTAL AREAS...EVEN
WITH THIN CIRRUS MOVING OVER FROM THE SOUTHWEST. SHORT WAVE ENERGY
WILL ARRIVE OVER THE MEXICAN MOUNTAINS THURSDAY EVE...AND TSTMS WILL
IGNITE AND MOVE EAST...MOVING OVER THE UPPER AND MID VALLEYS LATE
THURSDAY AND THURSDAY NIGHT. DISCUSSED PREVIOUSLY A MILDER RENDITION
FOR THE THU NIGHT WEATHER...OPTING NOT TO CARRY SEVERE WORDING AT
THIS TIME DUE TO LOW PROBABILITY CHANCES...WITH THE UNDERSTANDING
THAT AN ISOLTD SEVERE CELL CAN NOT BE RULED OUT.

LONG TERM /FRIDAY THROUGH TUESDAY/...BY FRIDAY MORNING, THE
MIDLEVEL TROUGH WILL BE SWEEPING NEWD THROUGH THE TEXAS PANHANDLE
INTO KANSAS. THIS WILL KEEP THE BEST DYNAMICS WELL TO THE NORTH.
AT THE SFC, LOWER ATMOSPHERE WILL BE PRIMED WITH AMPLE MOISTURE
WITH HIGHER CAPES. THE BIG ISSUE IS THE CAPPING. FORECAST STILL
SHOWS H8 TEMPERATURES 20 TO 25 DEGREES ALL DAY FRIDAY, PEAKING IN
THE EVENING. BEST THREAT FOR ANY THUNDERSTORM ACTIVITY WOULD BE
FOR THE FAR WESTERN VALLEY AGAIN, WITH MOUNTAIN THUNDERSTORMS
MOVING ENE ACROSS THE RIVER AFTER SUNSET. WITH THE LACK OF SUPPORT
ALOFT AND THE CAP, CAN`T GO MORE THAN A 20 TO 30 POP. IF ANY
STORMS TO REACH THE CWA, THERE IS THE RISK FOR THEM BEING STRONG
TO SEVERE. WITH H8 TEMPS AT 20 TO 25 C, THAT TRANSLATES TO HIGH
TEMPERATURES IN THE 90S FOR MOST OF THE REGION. WITH DEWPOINTS IN
THE 70S, HEAT INDEX VALUES WILL PUSH 100 TO 105 DURING THE
AFTERNOON.

SATURDAY WILL BE A QUIETER DAY AS WEAK RIDGING BRIEFLY REIGNS
ALOFT. THE ONLY POSSIBILITY FOR A THUNDERSTORM WOULD BE IF THE
DRYLINE WERE ABLE TO REACH THE WESTERN VALLEY LATER SATURDAY.
GOING TO BE TOUGH TO DO. TEMPERATURES AGAIN REACH THE 90S FOR THE
VALLEY WITH HUMID CONDITIONS CONTINUING.

LONGER TERM PERIOD BRINGS THE NEXT TROUGH DIVING DOWN THE ROCKIES
INTO TEXAS...WITH ANOTHER ROUND OF IMPROVED DYNAMIC SUPPORT ALOFT.
MODELS ARE STILL TRYING TO BRING A FRONT ACROSS TEXAS SOMETIME
EARLY NEXT WEEK...WHICH WOULD BE A USEFUL TRIGGERING MECHANISM
FOR SHOWER FORMATION. UNTIL MODELS COME TOGETHER BETTER ON A
PASSAGE TIMING AND STRENGTH, CAN ONLY CAST A WIDE NET FOR NOW.

MARINE...
NOW THROUGH THURSDAY NIGHT...MID LEVEL RIDGING WILL BUILD OVER THE
GULF OF MEXICO...SUPPORTING BROAD SURFACE HIGH PRESSURE. THIS WILL
MAINTAIN LIGHT TO MODERATE SOUTHEAST WINDS AND LOW TO MODERATE SEAS.
A FEW SHOWERS OR THUNDERSTORMS WILL BE POSSIBLE.

FRIDAY THROUGH SUNDAY...CONSISTENT CONDITIONS CONTINUE ACROSS THE
GULF WATERS, WITH MODEST SOUTHEAST FLOW 10 TO 15 KNOTS CREATING
SEAS GENERALLY 3 TO 4 FEET.

&&

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

$$

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