Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 162359 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
659 PM CDT THU APR 16 2015

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

&&

.AVIATION...LOW AND HIGH LEVEL CLOUDS CONTINUE ACROSS DEEP SOUTH
TEXAS THIS EVENING. CEILINGS RANGE FROM 1400 FEET AT BRO TO 2600
FEET AT MFE AND T65. VISIBILITIES RANGE FROM 4SM AT PIL TO 6SM AT
MFE DUE TO LINGERING HAZE. LATEST BRO RADAR SHOWS DIMINSHING
CONVECTION SOUTH OF THE RIO GRANDE VALLEY. EXPECT MVFR WITH BRIEF
PERIODS OF VFR CONDITIONS THIS EVENING. MVFR TO IFR CONDITIONS
WILL DEVELOP TONIGHT AS ABUNDANT LOW TO MID LEVEL MOISTURE ALLOWS
LOW CLOUDS AND PATCHY FOG TO DEVELOP LATE TONIGHT INTO EARLY
FRIDAY MORNING. SHOWERS AND THUNDERSTORMS ARE FORECAST TO DEVELOP
ACROSS DEEP SOUTH TEXAS AFTER 15Z FRIDAY. UNCERTAINTY CONTINUES
ON TIMING AND COVERAGE OF CONVECTION FOR FRIDAY. THE LATEST MODEL
DATA INDICATES THAT THE BETTER THUNDERSTORM CHANCES MAY REMAIN
NORTH OF THE VALLEY TAF SITES THROUGH LATE FRIDAY AFTERNOON. WILL
CONTINUE TO MENTION VCSH FOR ALL TAF SITES STARTING AT 15Z.

&&

.PREV DISCUSSION... /ISSUED 334 PM CDT THU APR 16 2015/

SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...SATELLITE AND RADAR
IMAGES INDICATE STRONG TO SEVERE THUNDERSTORMS CONTINUE TO DEVELOP
WELL NORTHEAST OF THE CWA THIS AFTERNOON AS A WEAK WARM FRONT LIFTS
NORTHWARD ACROSS SOUTH TEXAS. IN ADDITION...CONVECTION APPEARS TO BE
DEVELOPING ACROSS THE MEXICAN PLATEAU. SURFACE INSTABILITY CONTINUES
TO INCREASE THIS AFTERNOON WITH DIURNAL HEATING AND WE MAY STILL SEE
SOME ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS DEVELOP ACROSS
PORTIONS OF THE RIO GRANDE VALLEY AND THE NORTHERN RANCHLANDS LATE
THIS AFTERNOON INTO THIS EVENING BEFORE THE LOSS OF DIURNAL HEATING.
WILL NOT MENTION ANY SEVERE STORMS TONIGHT BUT SOME STORMS COULD BE
STRONG WITH GUSTY WINDS AND SMALL HAIL.

THE THREAT FOR SEVERE WEATHER APPEARS TO INCREASE FRIDAY INTO FRIDAY
NIGHT AS THE 500MB LOW ACROSS THE SOUTHWEST UNITED STATES MOVES
SLOWLY EASTWARD TONIGHT INTO FRIDAY. A MESOSCALE CONVECTIVE SYSTEM
IS EXPECTED TO DEVELOP ACROSS SOUTHWEST TEXAS LATE TONIGHT INTO FRI
MORNING AND POSSIBLY MOVE EASTWARD ACROSS THE NORTHERN RANCHLANDS
LATE FRI MORNING. WITH THE SURFACE INSTABILITY AND STEEP LAPSE RATES
ACROSS THE RIO GRANDE PLAINS...DAMAGING WINDS AND HAIL ARE THE MAIN
THREATS FOR SEVERE WEATHER BUT AN ISOLATED TORNADO CANNOT BE RULED
OUT AS THE GFS PROGS A SURFACE MESOLOW DEVELOPING ACROSS THE WESTERN
PORTIONS OF THE CWA FRIDAY AND THIS WILL ENHANCE THE STORM RELATIVE
HELICITY ACROSS THE NORTHERN PORTIONS OF THE CWA AS A RESULT.
ASSUMING THE MCS DEVELOPS AND MOVES ACROSS THE NORTHERN PORTIONS OF
THE CWA LATE FRIDAY MORNING...WILL LIKELY HAVE TO WAIT UNTIL THE
ATMOSPHERE RECOVERS FRI AFTERNOON INTO FRI EVENING FOR THE NEXT
POSSIBLE ROUND OF CONVECTION TO DEVELOP ACROSS PORTIONS OF SOUTHWEST
TX AND NORTHEAST MEXICO FRI NIGHT BUT THE LOSS OF DIURNAL HEATING
WILL LIMIT THE POTENTIAL FOR SEVERE WEATHER. WILL MENTION SEVERE
STORMS FRIDAY AFTERNOON INTO FRIDAY EVENING WITH HEAVY RAINFALL
POSSIBLE FRIDAY INTO FRI NIGHT. WILL NOT ISSUE ANY FLASH FLOOD
WATCHES AT THIS TIME AS THE FLOODING THREAT SHOULD BE LOCALIZED IN
NATURE AND NOT WIDESPREAD.

LONG TERM /SATURDAY THROUGH WEDNESDAY/...AS THE H5 TROUGH TO THE
NORTH SLOWLY SWEEPS ACROSS THE US...THE DIFFLUENCE AHEAD OF IT
WILL SHIFT AWAY FROM SOUTH TEXAS...DECREASING THE EFFECTS OF ITS
DYNAMICAL LIFTING. SATURDAY...THE AS THE LOW SWEEPS BY...A STRONG
MIDLEVEL JET STREAK WILL WRAP AROUND THE BOTTOM OF THE TROUGH
THROUGH SOUTH TEXAS. OUR AREA WILL BE ON THE FAVORABLE RIGHT REAR
QUAD FOR CONTINUED MIDLEVEL ENHANCEMENT. AT THE SFC...FOCUSING
MECHANISM INCLUDE OUTFLOW BOUNDARIES LEFT OVER FROM FRIDAY
ACTIVITY...AND THE LATE INTRUSION OF THE DRYLINE INTO THE FAR
WESTERN VALLEY. THIS SHOULD BE SUFFICIENT TO SPARK THUNDERSTORM
ACTIVITY FOCUSED ON THE AFTERNOON HOURS SATURDAY. THE STRENGTH OF
THESE STORMS WILL BE HIGHLY DEPENDENT ON THE STRENGTH AND TIMING
OF FRIDAYS STORMS...WHICH COULD STABILIZE THE ATMOSPHERE FOR UP TO
18 HOURS. WILL NOT YET ADD SEVERE WORDING TO THE FORECAST...BUT
WILL EMPHASIZE THE THREAT REMAINS DEPENDING ON FRIDAYS TURNOUT.
SUNDAY MAY BE A QUIETER DAY AS DYNAMICS ALOFT ARE LACKING AND THE
LIKELY ABSENCE OF REMNANTS BOUNDARIES AND THE DRYLINE. A FEW
PASSING THUNDERSTORMS MAY DEVELOP DURING PEAK HEATING...DEPENDING
ON DRY AIR CAPPING ALOFT. MOISTURE REMAINS IN THE REGION FOR THE
FIRST HALF OF NEXT WEEK...WITH THE POSSIBILITY OF SHOWERS AND
THUNDERSTORMS EACH DAY.

MARINE...TONIGHT THROUGH FRIDAY NIGHT...SEAS WERE NEAR 3 FEET
WITH EAST WINDS NEAR 8 KNOTS AT BUOY020 THIS AFTERNOON. WINDS WILL
VEER TO THE SOUTHEAST AND INCREASE ACROSS THE LOWER TEXAS COASTAL
WATERS TONIGHT WITH LOW PRESSURE ACROSS WEST TEXAS. LIGHT TO
MODERATE SOUTHEAST WINDS WILL PREVAIL ACROSS THE WESTERN GULF OF
MEXICO FRIDAY. SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS THE
COASTAL WATERS FRIDAY INTO FRI NIGHT AS THE 500MB LOW ACROSS THE
SOUTHWEST UNITED STATES MOVES EASTWARD PROVIDING INSTABILITY
ACROSS SOUTH TEXAS AND THE WESTERN GULF OF MEXICO. SOME OF THESE
STORMS MAY BE STRONG TO SEVERE AND WINDS AND SEAS WILL BE HIGHER
IN AND NEAR THUNDERSTORMS.

SATURDAY THROUGH MONDAY...CONDITIONS REMAIN CONSISTENT THROUGH
THE UPCOMING WEEKEND...AS MODERATE ONSHORE FLOW CONTINUES. WINDS
REMAIN FROM THE SOUTHEAST 10 TO 15 KNOTS EACH DAY...CREATING SEAS
OF 3 TO 4 FEET. MAIN WEATHER ISSUE WILL BE THE CONTINUED SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE PERIOD...WHICH MAY PRODUCE
GUSTY WINDS AND FREQUENT LIGHTNING.

&&

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

$$

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

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