865
FXUS64 KEWX 211130
AFDEWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
630 AM CDT SUN OCT 21 2018
AVIATION
WHILE MID AND HIGH LEVEL CLOUDS MOVE ACROSS THE STATE IN THE
SOUTHWESTERLY FLOW ALOFT VFR FLYING CONDITIONS WILL PREVAIL THROUGH
THE TAF PERIOD. WINDS AT THE I-35 TERMINALS WILL BE OUT OF THE NORTH
AROUND 10 KNOTS TODAY, DECREASING TO 5 KNOTS OR LESS OVERNIGHT
TONIGHT. AT DRT WINDS WILL GO EASTERLY/SOUTHEASTERLY LATE THIS
AFTERNOON. DRIZZLE OR LIGHT RAIN MAY BE POSSIBLE BY 18Z AT THE 30 HR
TAF SITES (AUS/SAT) BUT THE BEST CHANCES ARE DURING THE AFTERNOON
HOURS PER THE HIGH RESOLUTION MODELS, SO HAVE LEFT THE TAFS DRY FOR
NOW.
PREV DISCUSSION
/ISSUED 401 AM CDT SUN OCT 21 2018/
SHORT TERM (TODAY THROUGH MONDAY)...
WEAK COLD AIR ADVECTION BEHIND YESTERDAY'S FRONT WILL ALLOW FOR
MORNING TEMPERATURES IN THE REGION TO FALL FARTHER INTO THE 50S BY
SUNRISE. DESPITE NEARLY PERSISTENT MID AND HIGH CLOUD COVER TODAY,
RAIN CHANCES WILL REMAIN MINIMAL AS DRIER LOW LEVEL AIR ASSOCIATED
WITH A SURFACE RIDGE SLIDING ACROSS TEXAS PENETRATES FARTHER INTO THE
REGION. AIRCRAFT SOUNDINGS OUT OF SAN ANTONIO AROUND 11 PM LAST NIGHT
ALREADY SHOWED THIS DRIER LAYER HAD REACHED THE INTERSTATE 10
CORRIDOR AND WAS AROUND 10,000 FEET DEEP. EXPECT HIGHS THIS AFTERNOON
TO CLIMB INTO THE MID 60S TO LOWER 70S WITH THIS DRIER AIR ALLOWING
FOR LOWS MONDAY MORNING TO FALL INTO THE UPPER 40S TO MID 50.
UPPER RIDGING OVER THE REGION TODAY WILL BEGIN TO TRANSLATE EAST AND
FLATTEN TONIGHT AND MONDAY. THIS IS IN RESPONSE TO A REX BLOCK
BREAKING DOWN OFF THE CALIFORNIA COAST, ALLOWING A CLOSED LOW TO OPEN
UP AND PUSH EASTWARD TOWARDS NEVADA. AS THE UPPER RIDGE SHIFTS EAST
(AND NUDGES THE SURFACE RIDGE EAST WITH IT), INCREASING UPPER LEVEL
DIVERGENCE ASSOCIATED WITH A SOMEWHAT CURVED 70-80 KNOT JET STREAK
WILL RESULT IN LIGHT SHOWERS DEVELOPING NEAR THE RIO GRANDE PLAINS
LATE THIS EVENING AND TONIGHT. SHOWERS ARE EXPECTED TO SPREAD EAST
TOWARDS THE INTERSTATE 35 CORRIDOR DURING THE DAY MONDAY. SHOWERS MAY
INITIALLY BE VIRGA TONIGHT BEFORE ENOUGH TOP DOWN MOISTENING OCCURS
TO ALLOW RAIN TO REACH THE SURFACE. FORECAST SOUNDINGS INDICATE
ALMOST NO MUCAPE OR APPRECIABLE INSTABILITY DURING THIS TIME AND
EXPECT SHOWER ACTIVITY ON MONDAY TO REMAIN LIGHT TO OCCASIONALLY
MODERATE. HIGHEST ACCUMULATIONS TONIGHT THROUGH MONDAY MAY APPROACH
ONE HALF TO ONE INCH ALONG AND SOUTH OF THE HIGHWAY 57/INTERSTATE 10
CORRIDOR WHERE SHORTER TERM GUIDANCE INDICATES SOME KIND OF 850 MB
CONVERGENT AXIS SETS UP AS THE LOW LEVEL RIDGE SHIFTS EAST OF THE
REGION.
LONG TERM (MONDAY NIGHT THROUGH SATURDAY)...
LITTLE CHANGE IS EXPECTED IN THE OVERALL PATTERN MONDAY NIGHT INTO
TUESDAY NIGHT, WITH PERSISTENT UPPER LEVEL DIVERGENCE AHEAD OF THE
APPROACHING TROUGH FROM NEVADA CONTRIBUTING TO WHAT APPEARS TO BE A
RATHER EXPANSIVE SHIELD OF RAIN ACROSS THE SOUTHERN HALF OF TEXAS.
INSTABILITY CONTINUES TO APPEAR RELATIVELY MINIMAL MONDAY NIGHT AND
TUESDAY AS THE GULF REMAINS CLOSED OFF TO THE REGION AND CLOUDS
LIMIT DIURNAL DESTABILIZATION, WHICH WILL HELP KEEP RAIN RATES FAIRLY
LIGHT. HOWEVER, NEARLY PERSISTENT RAIN WILL ALLOW FOR RAINFALL
AMOUNTS MONDAY NIGHT THROUGH TUESDAY NIGHT TO RANGE FROM ONE TO TWO
INCHES SOUTH OF A DEL RIO TO LA GRANGE LINE.
BY WEDNESDAY, THE UPPER TROUGH LIFTS INTO WEST TEXAS AND HELPS DRAW
THE REMNANTS OF EASTERN PACIFIC TROPICAL STORMS WILLA AND VICENTE
TOWARDS THE REGION. DEPENDING ON HOW WELL THESE THESE SYSTEMS ARE
ABLE TO MAINTAIN THEMSELVES ACROSS THE HIGHER TERRAIN OF MEXICO,
PRECIPITABLE WATER VALUES INCREASING INTO THE 1.5 TO 1.7 INCH RANGE
AND ENHANCED MID AND UPPER LEVEL FORCING MAY HELP INCREASE RAIN
RATES DURING THE DAY WEDNESDAY ACROSS THE SOUTHERN HALF OF THE
REGION. AS A RESULT, WILL HAVE TO MONITOR WEDNESDAY FOR THE POTENTIAL
FOR LOCALLY HEAVY RAINFALL. OTHERWISE, EXPECT PERSISTENT CLOUD COVER
AND RAIN DURING THE MIDDLE OF THE WEEK TO KEEP HIGHS ONLY IN THE
UPPER 50S TO LOWER 60S.
AS THE UPPER TROUGH CLEARS THE REGION EARLY THURSDAY, RAIN CHANCES
WILL QUICKLY END FROM WEST TO EAST AS MOISTURE IS SWEPT EAST OF THE
REGION AND PRECIPITABLE WATER VALUES FALL BACK INTO THE 1-1.25 INCH
RANGE. LIMITED AVAILABLE LOW AND MID LEVEL MOISTURE WILL MEAN THAT A
SECONDARY UPPER TROUGH PASSAGE ON FRIDAY SHOULD HAVE LITTLE IMPACT ON
SENSIBLE WEATHER AS IT SENDS A REINFORCING COLD FRONT INTO THE
REGION ON SATURDAY, SAVE FOR SOME PASSING HIGH CLOUDS. THIS WILL MAKE
FOR A DRY AND MILD END TO THE WEEK WITH HIGHS FRIDAY AND SATURDAY IN
THE UPPER 60S TO MID 70S AND LOWS IN THE UPPER 40S TO MID 50S.
PRELIMINARY POINT TEMPS/POPS
AUSTIN CAMP MABRY 69 53 62 51 63 / 0 - 50 50 60
AUSTIN BERGSTROM INTL AIRPORT 69 51 62 50 63 / 0 - 50 50 60
NEW BRAUNFELS MUNI AIRPORT 70 52 62 51 62 / 0 - 60 60 60
BURNET MUNI AIRPORT 67 49 64 50 61 / 0 10 40 50 50
DEL RIO INTL AIRPORT 68 54 61 54 62 / 10 20 60 40 60
GEORGETOWN MUNI AIRPORT 68 50 63 49 63 / 0 - 40 40 50
HONDO MUNI AIRPORT 70 54 61 53 62 / 0 20 70 60 60
SAN MARCOS MUNI AIRPORT 70 52 61 52 62 / 0 - 50 60 60
LA GRANGE - FAYETTE REGIONAL 71 52 63 53 64 / 0 0 40 60 60
SAN ANTONIO INTL AIRPORT 69 53 62 53 61 / 0 10 60 70 60
STINSON MUNI AIRPORT 71 54 63 54 61 / 0 10 60 70 60
EWX WATCHES/WARNINGS/ADVISORIES
NONE.
AVIATION...TREADWAY
SHORT-TERM/LONG-TERM...HUFFMAN
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