Area Forecast Discussion
Issued by NWS Brownsville, TX

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FXUS64 KBRO 042352 AAA
AFDBRO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BROWNSVILLE TX
552 PM CST WED MAR 4 2015

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

.AVIATION...SATELLITE IMAGES AND SURFACE OBSERVATIONS INDICATE LOW
CLOUDS DEVELOPING ACROSS EXTREME SOUTHEAST PORTIONS OF THE CWA
EARLY THIS EVENING WITH MID TO HIGH LEVEL CLOUDS ACROSS THE REST
OF THE CWA. CEILINGS WERE NEAR 1200FT AT KPIL TO NEAR 3600FT AT
KBKS. VISIBILITIES WERE NEAR 6SM WITH FOG AT KPIL. EXPECT MVFR TO
IFR CONDITIONS TO DEVELOP TONIGHT AS MOISTURE POOLS ALONG AND
AHEAD OF A STRONG COLD FRONT MOVING INTO THE NORTHERN PORTIONS OF
THE CWA LATE TONIGHT. IN ADDITION...WINDS WILL DIMINISH AHEAD OF
THE FRONT ALLOWING LOW CLOUDS/FOG TO DEVELOP ACROSS THE SOUTHERN
AND EASTERN PORTIONS OF THE CWA. THE FRONT WILL MOVE THROUGH THE
RIO GRANDE VALLEY EARLY THURS MORNING. IFR CONDITIONS WILL PREVAIL
THE REST OF TONIGHT INTO THURSDAY AS OVERRUNNING CONDITIONS
DEVELOP AS WARM AND MOIST AIR ALOFT MOVES ACROSS THE SHALLOW COLD
AIR FILTERING INTO THE AREA.
&&

.PREV DISCUSSION... /ISSUED 257 PM CST WED MAR 4 2015/
SHORT TERM /NOW THROUGH THURSDAY NIGHT/...THE INFAMOUS COLD FRONT
CURRENTLY LIES ALONG A SHREVEPORT...TEMPLE...JUNCTION TO NORTH OF
DEL RIO LINE. STEADY SOUTHWARD PROGRESS SURGES THE FRONT THROUGH
THE NORTHERN COUNTIES BETWEEN MIDNIGHT AND 3AM AND THE RGV 3 TO 6
AM. TEMPERATURES IN THE 20S AND 30S OVER NORTH TEXAS WILL BE
HEADING OUR WAY WITH AT LEAST A 24-36 HOUR PERIOD OF COLD AIR
ADVECTION. FORECAST REMAINS DIFFICULT TO DIGEST WITH A LOT GOING
ON IN A SHORT AMOUNT OF TIME.

WILL HIGHLIGHT THE BIGGEST IMPACTS. THE SHARP TEMPERATURES CONTRAST
IS STILL ON TAP WITH TEMPERATURES TO REMAIN IN THE 60S OR NEAR 70
MUCH OF THE NIGHT THEN TUMBLE VERY QUICKLY WITH AN EXPECTED 20-30
DEGREE DROP IN TEMPERATURES 3 TO 5 HOURS. GFS/NAM GUIDANCE SHOW A
20+ DEGREE DROP IN THE LOWER VALLEY BETWEEN 6 AND 9 AM THURSDAY AND
THEN CONTINUE FALLING THROUGH MID DAY. EXPECT UP TO A 40+ DEGREE
DOWNWARD CHANGE IN AMBIENT TEMPERATURES FROM TODAY THROUGH THURSDAY.

WINDS AND WIND CHILLS NEXT...TIGHT PRESSURE GRADIENT ACROSS TEXAS
AND JUST BEHIND THE FRONT AND STILL ARCTIC HIGH PRESSURE AT 1040MB
TO MOVE INTO STATE THURSDAY. NORTHERLY WINDS TO INCREASE RAPIDLY
WITH THE INITIAL SURGE OF THE FRONT WITH AT LEAST 20 TO 30 MPH AND
HIGHER GUSTS. GRADIENT STRENGTHENS THROUGH AT LEAST NOON WITH WINDS
UP ANOTHER NOTCH POSSIBLY REACHING WIND ADVISORY LEVELS ALONG THE
COAST COUNTIES. THIS WILL MATCH UP WELL WITH THE ON GOING GALE
WARNING ISSUED LAST NIGHT. MODEL GUIDANCE HAS ALSO BEEN INDICATING 3
TO 6 HOURS OF ADVISORY LEVELS WINDS AND THE MAV AND MET USUALLY DO
WELL WITH THE LOCAL WINDS. AS THE WINDS INCREASE AND TEMPS DROP LIKE
A ROCK WINDS CHILLS TO GO LOW. WIND CHILL ADVISORIES WILL BE ISSUED
FOR ALL OF THURSDAY AND MAY HAVE TO BE EXTENDED THROUGH THURSDAY
NIGHT IF WINDS REMAIN HIGH ENOUGH.

RAINFALL AND POTENTIAL FOR FREEZING RAIN...OF THE MOST CONCERN BUT
LATE IN THE FORECAST PERIOD IS THE CHANCE OF RAIN FREEZING RAIN AND
OR DRIZZLE IN THE MID AND LOWER VALLEY LATE THURSDAY NIGHT INTO
FRIDAY MORNING. FIRST RAIN TO INCREASE IN COVERAGE AS THE FRONT
PASSES TO THE SOUTH. OVERRUNNING CONDITIONS TO DEVELOP RATHER RAPIDLY
IN WAKE OF THE FRONT WITH THE WARM AIR BEING FORCED OVER THE TOP OF
THE DEEPENING COLD AIR. RAIN AMOUNTS MAY NOT BE MUCH A FEW HUNDREDTHS
AT BEST BUT MOST AREAS SHOULD SEE SOME RAIN. POPS WERE INCREASED TO
60 TO 80 PERCENT FOR THURSDAY AND CONFIDENCE IS HIGH ENOUGH TO
WARRANT 100 PERCENT. TEMPERATURES CONTINUE TO FALL SLIGHTLY
THURSDAY NIGHT AND DEW POINTS CONTINUE TO CRASH INTO FRIDAY
MORNING. THE DRIER AIR WILL PUSH THE DEEPER MOISTURE SOUTH LETTING
THE NORTHERN AND WESTERN RANCHLANDS TO DRY OUT. THE COASTAL SECTIONS
CONTINUE OVER THE DEEPER MOISTURE WITH A SHARP INVERSION AND DEEP
LAYER MOISTURE. EVAPORATIVE COOLING IS LIKELY TO TAKE PLACE AS
PRECIPITATION CONTINUES TO FALL THROUGH THIS LAYER AND WITH DEW
POINTS FALLING BETWEEN 25-29 DEGREES AMBIENT TEMPERATURES COULD FALL
TO THE WET BULB WHICH IS FORECAST TO LOWER BETWEEN 30-32 DEGREES.
THIS BRINGS UP THE THREAT OF SOME FREEZING RAIN/DRIZZLE. AN SPS HAS
BEEN ISSUED TO COVER THE DETAILS AND CONFIDENCE ON THIS EVENT. NO
ADVISORIES OR WARNINGS ARE ISSUED YET BUT FURTHER INTERROGATION OF
THE NEXT TWO MODEL RUNS MAY SHED SOME LIGHT ON THIS ISSUE.

LONG TERM /FRIDAY THROUGH TUESDAY/...AN ARCTIC SOURCE AIRMASS
ARRIVING THURSDAY WILL CONTINUE TO SETTLE OVER DEEP SOUTH TEXAS
EARLY IN THE LONG TERM. CAA WILL CONTINUE ACROSS THE AREA THROUGH
SATURDAY. SOUTHWEST WINDS ALOFT...ANCHORED BY A MID LEVEL LOW OVER
BAJA CALIFORNIA AND NORTHWEST MEXICO WILL SUPPORT OVERRUNNING...
PERSISTENT CLOUDY SKIES WITH PATCHY DRIZZLE AND LIGHT RAIN THROUGH
SATURDAY MORNING.

TEMPERATURES WILL BE WELL BELOW NORMAL...WITH SPECIAL HAZARDS FRIDAY
MORNING. A VERY COLD AIR MASS WILL ARRIVE THU MORNING...LOWERING
TEMPERATURES SIGNIFICANTLY. THURSDAY NIGHT TEMPERATURES FOR THE LWR
VALLEY...INCLUDING THE COUNTIES OF CAMERON...WILLACY...HIDALGO AND
THE SOUTHERN PORTIONS OF KENEDY AND BROOKS COUNTIES...WILL DECREASE
TO JUST ABOVE FREEZING BY THE PREDAWN HOURS OF FRIDAY. ANY LIGHT
LIQUID PRECIPITATION WILL HAVE A CHANCE TO EVAPORATE AS IT FALLS
THROUGH DRIER AIR NEAR THE SFC...ALLOWING IT TO POTENTIALLY COOL
ENOUGH TO FREEZE BY THE TIME IT REACHES THE GROUND.

FRIDAY TEMPS WILL WARM INTO THE 40S BUT TEMPERATURES OVERALL WILL
REMAIN WELL BELOW NORMAL THROUGH THE WEEKEND. LOW TEMPERATURES
FRIDAY NIGHT WILL FALL INTO THE 30S ACROSS THE RANCHLANDS TO THE
LOWER 40S NEAR THE COAST. NO FREEZING TEMPERATURES EXPECTED AT THIS
TIME ACROSS DEEP SOUTH TEXAS. HIGH TEMPS SATURDAY WILL SEEM WARM IN
THE 50S EVEN THOUGH 20 DEGREES BELOW NORMAL. A SLOW WARMING TREND
WILL CONTINUE INTO THE EARLY PART OF THE WEEK...WITH NEAR NORMAL
TEMPS FINALLY BACK AROUND TUESDAY.

THE DEVELOPMENT OF A COASTAL TROUGH OFF THE LOWER TEXAS COAST...
ALONG WITH AN APPROACHING A 500MB TROUGH BELOW THE RIGHT ENTRANCE
REGION OF AN EXITING JET STREAK WILL PROVIDE A LINGERING CHANCE OF
RAIN SATURDAY THROUGH MONDAY OR TUESDAY. THE TROUGH WILL MOVE SLOWLY
EAST...STRUGGLING TO MOVE PAST TEXAS...AND RAIN CHANCES WILL LINGER
INTO EARLY NEXT WEEK.

MARINE...
GALE WARNINGS REMAIN POSTED FOR THE LOWER TEXAS COAST AS WELL AS
THE ENTIRE TEXAS COAST AND ALL OF THE WESTERN AND SOUTHWESTERN
GULF OF MEXICO. THE SIGNIFICANT COLD FRONT EXPECTED BETWEEN
MIDNIGHT AND 6AM WITH GALE FORCE WINDS TO DEVELOP RATHER QUICKLY.
SEAS BECOME HAZARDOUS BY 6 AM THURSDAY IF NOT EARLIER AND WILL
STAY INTENSE THROUGH THURSDAY NIGHT AS STRONG HIGH PRESSURE
REMAINS NORTH OF THE COASTAL WATERS WITH COLD AIR CONTINUES TO
POOR INTO THE REGION. FOG MAY DEVELOP OFFSHORE TONIGHT AS WINDS
SLACKEN IN ADVANCE OF THE FRONT AND MAY BECOME DENSE FOR A SHORT
WHILE BEFORE THE STRONG WINDS ADVANCE SOUTHWARD.

FRIDAY THROUGH SUNDAY...SLOW RECOVERY WILL BE ONGOING IN THE WAKE OF
THE STRONG COLD FRONT OF THURSDAY. HIGH SEAS PERSISTING INTO FRIDAY
EVENING WILL EXTEND SMALL CRAFT ADVISORY CONDITIONS INTO THE LONG
TERM PORTION OF THE FORECAST...EVEN AS WINDS EASE BELOW 20 KNOTS
FRIDAY MORNING. THE MAIN HIGH PRESSURE CENTER WILL HOLD STRONG OVER
THE LOWER MISSISSIPPI VALLEY FRIDAY...BUT HIGH PRESSURE OVER SOUTH
TEXAS WILL WEAKEN AND THE WINDS OVER THE GULF WILL VEER AND WEAKEN
FROM FRESH TO MODERATE BY SATURDAY. HIGH PRESSURE PUSHING OUT INTO
THE NORTHEAST GULF SUNDAY AND THE PERSISTENCE OF AN INVERTED
TROUGH OVER THE NORTHWEST GULF MAY HELP REINVIGORATED NORTHEAST
WINDS INCREASE BACK INTO THE FRESH CATEGORY SUNDAY...REQUIRING AN
EXERCISE CAUTION OR LOW END SMALL CRAFT ADVISORY MENTION ON THE
GULF...WITH SEAS AT FOUR TO SIX FEET SUNDAY BUT BUILDING TO SEVEN
FEET OR MORE SUNDAY NIGHT AND EARLY NEXT WEEK.
&&

.BRO WATCHES/WARNINGS/ADVISORIES...
TX...WIND CHILL ADVISORY FROM 6 AM TO 6 PM CST THURSDAY FOR
     TXZ248>257.

     WIND ADVISORY FROM 5 AM TO 3 PM CST THURSDAY FOR TXZ251-254>257.

GM...GALE WARNING FROM MIDNIGHT TONIGHT TO 6 PM CST THURSDAY FOR
     GMZ130-132-135-150-155-170-175.
&&

$$

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