Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 231736 AAB
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
1236 PM CDT THU APR 23 2015

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

&&

.AVIATION...LOW CLOUDS HAVE BEEN SLOW TO ERODE TODAY...AS VERY
DENSE MOISTURE REMAINS TRAPPED UNDER INVERSION AROUND 4500 FEET.
SOME THINNING WILL HAPPEN THIS AFTERNOON...BUT CLOUD COVER WILL
LIKELY REMAIN OVERCAST JUST ABOVE 3000 THROUGH THE REST OF THE
DAY. LOW CLOUD CONDITIONS RETURN TONIGHT SIMILAR TO LAST NIGHT.
WINDS WILL REMAIN FROM THE SOUTHEAST AROUND 10KTS TODAY...LOWERING
TO AROUND 5KTS OVERNIGHT. SLIGHT DECREASES IN VIS NOTED AREAWIDE
DUE TO SMOKE FROM THE SOUTHEAST...BUT HAVE NO REPORTS OF INBOUND
VIS ISSUES YET.

&&

.PREV DISCUSSION... /ISSUED 649 AM CDT THU APR 23 2015/

DISCUSSION...UPDATED FOR LATEST AVIATION DISCUSSION BELOW.

AVIATION...BRO RADAR SHOWS A WEAKENING AREA OF SHOWERS MOVING
ACROSS THE RIO GRANDE VALLEY THIS MORNING AND WILL MENTION VCSH
THROUGH 14Z. OTHERWISE...LOW LEVEL MOISTURE TRAPPED UNDERNEATH AN
INVERSION HAS RESULTED IN CEILINGS RANGING FROM 400 FEET AT BRO AT
PIL TO AROUND 1500 FEET AT HRL WITH VISIBILITIES BETWEEN 3 TO 5SM
DUE TO FOG. A MIX OF IFR AND MVFR CONDITIONS WILL PREVAIL AT ALL
OF THE RIO GRANDE VALLEY TERMINALS THROUGH MID MORNING. CEILINGS
WILL GRADUALLY INCREASE TO MVFR LEVELS BY MID MORNING WITH VFR
CONDITIONS AROUND NOON. MVFR CEILINGS WILL RETURN AFTER 01Z AT
BRO/HRL AND AFTER 03Z AT MFE. IFR CEILINGS POSSIBLE AFTER 04Z AT
BRO/HRL AND 05Z AT MFE.

PREV DISCUSSION... /ISSUED 437 AM CDT THU APR 23 2015/

SHORT TERM /NOW THROUGH FRIDAY/...LATEST WATER VAPOR IMAGERY SHOWS
AN MID LEVEL TROUGH/LOW OFF THE SOUTHERN CALIFORNIA COAST...A WEAK
DISTURBANCE MOVING OVER NORTHEAST MEXICO AND RIDGING OVER TEXAS. AT
THE SURFACE...BROAD HIGH PRESSURE CONTINUES ACROSS THE EASTERN GULF
OF MEXICO THIS MORNING. WIDESPREAD FOG REDUCING VISIBILITIES TO
BETWEEN 3 AND 5 MILES WILL LINGER ACROSS THE AREA THROUGH MID
MORNING BEFORE DISSIPATING. CURRENT BRO RADAR SHOWS ISOLATED
CONVECTION ACROSS THE MEXICAN STATES OF NUEVO LEON AND TAMAULIPAS
EXTENDING INTO PORTIONS OF THE RIO GRANDE VALLEY. THIS ACTIVITY IS
BEING GENERATED BY AN UPPER LEVEL DISTURBANCE PASSING OVERHEAD.
ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ACROSS DEEP
SOUTH TEXAS NOW THROUGH AROUND NOON WITH ADDITIONAL CONVECTION
DEVELOPING LATER THIS AFTERNOON.

THE 500MB TROUGH/LOW DEEPENS OVER SOUTHERN CALIFORNIA/BAJA REGION AS
THE MID LEVEL RIDGE BUILDS OVER TEXAS TODAY. THE MID LEVEL TROUGH
EJECTS NORTHEAST AS THE 500MB RIDGE MOVES EAST TONIGHT INTO FRIDAY.
LOW LEVEL MOISTURE WILL CONTINUE TO ADVECT ACROSS THE REGION
COURTESY OF SOUTHEAST SURFACE FLOW. THE SOUTHWEST FLOW ALOFT WILL
CONTINUE TO PROVIDE CAPPING AND SUBSIDENCE...ESPECIALLY ACROSS THE
EASTERN PORTIONS OF THE AREA.

EXCEPT FOR THE COASTAL COUNTIES...DEEP SOUTH TEXAS REMAINS UNDER A
MARGINAL RISK OF SEVERE WEATHER FOR TODAY AND TONIGHT. ISOLATED
SHOWERS AND THUNDERSTORMS AND FOG WILL BE POSSIBLE THIS MORNING.
OTHERWISE... TEMPERATURES TODAY WILL BE VERY WARM WITH HIGH
TEMPERATURES IN THE MID TO UPPER 80S ALONG AND EAST OF I-69E/HIGHWAY
77 CORRIDOR WITH LOWER 90S ACROSS THE UPPER VALLEY AND WEST UNDER
ABUNDANT HIGH CLOUDS OVERHEAD. SHORT WAVE ENERGY WILL ARRIVE OVER
THE MEXICAN MOUNTAINS LATE THIS AFTERNOON INTO THIS EVENING. THIS
WILL RESULT IN CONVECTION DEVELOPING ACROSS SIERRA MADRE AND MOVING
INTO THE WESTERN PORTIONS OF DEEP SOUTH TEXAS THIS EVENING INTO
TONIGHT. WILL HOLD OFF ON MENTIONING SEVERE WORDING AT THIS TIME DUE
TO LOW PROBABILITY CHANCES...HOWEVER AN ISOLATED SEVERE CELL CAN NOT
BE RULED OUT. LOW TEMPERATURES TONIGHT WILL BE IN THE MID TO UPPER
70S. FRIDAY WILL BE VERY WARM WITH HIGH TEMPERATURES IN THE 90S...
EXCEPT FOR THE 80S NEAR THE COAST. THE STORM PREDICTION CENTER HAS
ALL OF DEEP SOUTH TEXAS UNDER A MARGINAL RISK OF SEVERE
THUNDERSTORMS FRIDAY. AGAIN...CAPPING AND SUBSIDENCE ACROSS THE AREA
SHOULD SUPPORT ONLY A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...MAIN CONCERN IN THE
FIRST 24 HOURS OF THE LONG TERM PORTION OF THE FORECAST WILL BE
THUNDERSTORMS. MODELS INDICATE CONVECTION WILL FIRE OVER THE HIGH
TERRAIN OF NEIGHBORING MEXICO FRIDAY NIGHT DUE TO A WEAK 500 MB
TROUGH RIDING WITHIN THE SOUTHWEST-TO-NORTHEAST MID-LEVEL FLOW...
WITH THE CONVECTION POSSIBLY ENHANCED BY A WEAK SURFACE BOUNDARY
OVER THE WESTERN PORTION OF THE BRO CWFA. STORM PREDICTION CENTER
HAS ALL OF DEEP SOUTH TEXAS AND THE RIO GRANDE VALLEY IN A
MARGINAL RISK OF SEVERE WEATHER FOR FRIDAY NIGHT...WITH A SLIGHT
RISK OF SEVERE WEATHER FOR THE ENTIRE CRP CWFA AND WFO/S FARTHER
NORTH...WITH AN ENHANCED RISK OVER EAST AND NORTHEAST TEXAS. AFTER
COORDINATING WITH NEIGHBORING WFO CRP...WILL HOLD OFF ON
MENTIONING SEVERE THUNDERSTORMS WITHIN THE BRO CWFA FOR THE FRIDAY
NIGHT TIME FRAME...BUT WILL RE-EXAMINE THE POSSIBLE FUTURE NEED OF
THE MENTION WITH SUCCESSIVE SHIFTS. FOR NOW...ISOLATED/SCATTERED
SHOWERS/THUNDERSTORMS WILL RESULT FRIDAY NIGHT AND SATURDAY...
WITH THE REMAINDER OF THE FORECAST DRY DUE TO DRIER AIR PUSHING
INTO THE REGION ON SURFACE BOUNDARIES...THE MOST SIGNIFICANT OF
WHICH IS THE PASSAGE OF A COLD FRONT ON TUESDAY. EXPECT WELL ABOVE
NORMAL TEMPERATURES IN ADVANCE OF THE FRONT AND MORE NORMAL IN THE
WAKE OF THE FRONTAL PASSAGE.

MARINE...NOW THROUGH FRIDAY...BUOY 42020 CURRENTLY REPORTS
SOUTH WINDS AROUND 10 KNOTS WITH SEAS AROUND 3.3 FEET. BROAD SURFACE
HIGH PRESSURE ACROSS THE EASTERN GULF OF MEXICO WILL MAINTAIN LIGHT
TO MODERATE SOUTHEAST WINDS AND LOW TO MODERATE SEAS. A FEW SHOWERS
OR THUNDERSTORMS WILL BE POSSIBLE TODAY THROUGH FRIDAY.

FRIDAY NIGHT THROUGH WEDNESDAY...MODERATE WINDS AND SEAS WILL
PREVAIL ALONG THE LOWER TEXAS COAST WITH SURFACE HIGH PRESSURE
DOMINANT OVER THE WESTERN GULF OF MEXICO THROUGH A MAJORITY OF
THE FORECAST PERIOD. SMALL CRAFT ADVISORIES WILL QUITE POSSIBLY
BE NEEDED ON TUESDAY AND WEDNESDAY DUE TO STRONGER WINDS AND
HIGHER SEAS PRODUCED BY THE TUESDAY MORNING PASSAGE OF A COLD
FRONT.

&&

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

$$

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