Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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FXUS64 KEWX 181039
AFDEWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
439 AM CST THU DEC 18 2014

...PERIODS OF HEAVY RAIN EXPECTED OVERNIGHT...

.SHORT TERM (TODAY THROUGH FRIDAY)...

MAIN FOCUS WILL CENTER ON NEXT 24-36 HOURS WHERE PERIODS OF HEAVY
RAIN WILL BE LIKELY FOR AREAS ALONG AND SOUTHEAST OF A PLEASANTON TO
GEORGETOWN LINE BEGINNING LATE TONIGHT THROUGH MID MORNING FRIDAY.
OVERALL ACCUMULATIONS NEAR 2 INCHES WITH LOCAL AREAS REACHING NEAR 3
INCHES SHOULD BE GREATEST ACROSS THE INLAND COASTAL PRAIRIES AND
SLOWLY TAPERING LOWER INTO THE 1-2 INCH RANGE TOWARDS THE I-35
CORRIDOR. SOME LOCALIZED FLASH FLOODING OR URBAN FLOODING COULD
OCCUR IF ENOUGH STORM TRAINING OCCURS.

FOR THIS MORNING, LIGHT SCATTERED SHOWERS AND DRIZZLE ARE SLOWLY
SHIFTING EAST ACROSS THE REGION WITH LIGHT DRIZZLE REMAINING
POSSIBLE THROUGH THE EARLY MORNING HOURS FOR MAINLY THE I-35
CORRIDOR AND AREAS EAST. AREAS OF FOG ARE ALSO ONGOING EARLY THIS
MORNING WITH SOME LOCALS SEEING DENSE FOG. FOG WILL IMPROVE THROUGH
THE EARLY TO MID MORNING. EXPECT A LULL IN ACTIVITY THROUGH MID
MORNING TO EARLY AFTERNOON WITH MOST SHOWER ACTIVITY RESIDING
TOWARDS THE TX COAST. THIS ACTIVITY HOWEVER WILL BEGIN TO MIGRATE
NORTHWARD AND BLOSSOM OVER THE REGION BY TONIGHT AS UPPER LEVEL
DIVERGENCE INCREASES WITH THE APPROACH OF POTENT SHORTWAVE TROUGH.

AS FAR AS WEATHER EVOLUTION TODAY AND OVERNIGHT, SHOWERS WILL
INITIALLY MOVE NORTH INTO SOUTHERN ZONES FROM SOUTH TEXAS LATE THIS
AFTERNOON. AS THE SHORTWAVE TROUGH PIVOTS TOWARDS THE REGION
TONIGHT, AND INVERTED SURFACE TROUGH AND EVENTUAL CLOSED LOW WILL
AID MOIST SE FLOW INTO THE RIO GRANDE VALLEY. THIS ADDITIONAL
MOISTURE UNDERNEATH AN ELEVATED COOLER CORE POCKET WILL INCREASE
BOTH SURFACE AND ELEVATED INSTABILITY FOR WESTERN LOCATIONS.
VERTICAL TOTALS LOOK TO INCREASE INTO THE 26-29C RANGE WITH
IMPRESSIVE -2 TO -5 NEGATIVE SHOWALTERS COUPLED WITH 60-70 KT 0-6 KM
SHEAR WILL SUPPORT A MARGINAL HAIL RISK INITIALLY AROUND MIDNIGHT.
THIS RISK WILL DECREASE INTO EARLY MORNING AS BAROCLINIC ZONE
FOCUSES FARTHER EAST. THE MAIN FOCUS OF IMPACTS FROM THIS SYSTEM
WILL BE THE BLOSSOMING OF SHOWER AND THUNDERSTORM ACTIVITY BY
MIDNIGHT ACROSS SOUTH-CENTRAL AND SOUTHEAST ZONES. OF HIGHEST
CONCERN WILL BE THE INLAND COASTAL PRAIRIE COUNTIES WHERE HI-RES
GUIDANCE AND SPC SSEO OUTPUT SUGGEST GREATEST RAIN TOTALS IN THE 2-3
INCH REALM COULD BE LOCATED. OVERALL GFS AND  GFS-PARALLEL TRENDS
HAVE ALSO FOCUSED IN THIS VICINITY WITH LESSER OVERALL AMOUNTS WEST
OF HWY 281 AND AMOUNTS TAPERING LOWER TOWARDS THE I-35 CORRIDOR. IF
SURFACE LOW DEVELOPS FARTHER SOUTH OR EAST, EVEN LOWER AMOUNTS FOR
THE I-35 CORRIDOR COULD OCCUR AS MOISTURE FLUX BECOMES DECREASED BY
BEING BLOCKED CLOSER TO THE COAST. HAVE PLACED GREATEST POPS IN
DURING THE MIDNIGHT TO 6AM TIMEFRAME WITH A RAMP UP AND RAMP DOWN
FOR THE PRE AND POST 3 HOUR TIME STEPS. SHOWER AND THUNDERSTORM
ACTIVITY WILL DECREASE AND MOVE EAST THROUGH MID MORNING FRIDAY WITH
MOST, IF NOT ALL, ACTIVITY EAST BY EARLY AFTERNOON. /ALLEN/

&&

.LONG TERM (FRIDAY NIGHT THROUGH WEDNESDAY)...

SLOW CLEARING WILL BE ONGOING BY LATE FRIDAY AND MORE SUN IS
EXPECTED SATURDAY WITH TEMPERATURES NEAR NORMAL. BY SUNDAY, YET
ANOTHER TROUGH LOOKS TO PIVOT OVER THE REGION BUT OVERALL COLUMN OF
MOISTURE LIKELY CONTINUES TO BE TOO DRY FOR SHOWER SUPPORT AS PWATS
WILL BE 0.5-0.7". INCREASED CLOUDINESS IS EXPECTED HOWEVER AND THAT
WILL LINGER THROUGH MONDAY BEFORE A DRY COLD FRONT LOOKS TO MOVE
ACROSS THE REGION EARLY TUESDAY. THIS WILL BRING REINFORCING DRIER
AIR AND KEEP TEMPERATURES NEAR NORMAL WITH TEMPERATURES AVERAGING IN
THE UPPER 30S TO LOW 40S FOR LOWS AND LOW TO MID 60S FOR HIGHS WITH
MORE SUN EXPECTED THROUGH MIDWEEK. NO IMPACT WEATHER IS EXPECTED
DURING THIS TIME FRAME. /ALLEN/

&&

.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY              68  54  59  45  58 /  20  90  80  10  10
AUSTIN BERGSTROM INTL AIRPORT  68  54  59  45  58 /  20  90  80  10  10
NEW BRAUNFELS MUNI AIRPORT     69  57  62  44  60 /  20  90  70  10  10
BURNET MUNI AIRPORT            67  51  57  40  56 /  10  80  70  10  10
DEL RIO INTL AIRPORT           67  54  65  43  61 /  -   40  20  10   0
GEORGETOWN MUNI AIRPORT        67  51  56  44  56 /  10  90  80  10  10
HONDO MUNI AIRPORT             70  56  64  41  60 /  20  80  60  10  10
SAN MARCOS MUNI AIRPORT        68  55  60  45  58 /  20  90  80  10  10
LA GRANGE - FAYETTE REGIONAL   69  57  62  48  59 /  30 100  90  10  10
SAN ANTONIO INTL AIRPORT       69  58  63  46  60 /  20  90  70  10  10
STINSON MUNI AIRPORT           69  58  64  45  61 /  20  90  70  10  10

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

MESOSCALE/AVIATION...04
SYNOPTIC/GRIDS...15




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