Light wind and plenty of low level moisture will allow some fog to develop late tonight. Watch for visibilities to drop after midnight. Take extra care if you plan to be out early Sunday morning. Here’s the advisory from the National Weather Service:

Dense Fog Advisory

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
756 PM CST SAT NOV 7 2009

...DENSE FOG ADVISORY ALONG THE BALCONES ESCARPMENT EARLY THROUGH
MID-MORNING SUNDAY...

.MID-LEVEL CLOUD COVER WILL DELAY THE DEVELOPMENT OF FOG AND LIMIT
THE EXTENT OF DENSE FOG BY SLOWLY RADIATIONAL COOLING. HOWEVER...
THERE IS STILL PLENTY OF MOIST AIR IN THE BOUNDARY LAYER...AND DRY
AIR ALOFT...TO PROMOTE DIFFERENTIAL RADIATIONAL COOLING AND THE
DEVELOPMENT OF FOG AREAWIDE BY 3 AM CST...WITH DENSE FOG LIKELY
ALONG THE BALCONES ESCARPMENT FROM GEORGETOWN TO SAN ANTONIO TO
UVALDE.

TXZ173-191>193-203>207-220-081600-
/O.NEW.KEWX.FG.Y.0007.091108T0900Z-091108T1600Z/
WILLIAMSON-HAYS-TRAVIS-BASTROP-UVALDE-MEDINA-BEXAR-COMAL-
GUADALUPE-ATASCOSA-
INCLUDING THE CITIES OF...GEORGETOWN...SAN MARCOS...AUSTIN...
BASTROP...UVALDE...HONDO...SAN ANTONIO...NEW BRAUNFELS...SEGUIN...
PLEASANTON
756 PM CST SAT NOV 7 2009

...DENSE FOG ADVISORY IN EFFECT FROM 3 AM TO 10 AM CST SUNDAY...

THE NATIONAL WEATHER SERVICE IN AUSTIN/SAN ANTONIO HAS ISSUED A
DENSE FOG ADVISORY...WHICH IS IN EFFECT FROM 3 AM TO 10 AM CST
SUNDAY.

MOIST GULF AIR NEAR THE GROUND AND DRIER AIR ALOFT WILL ALLOW FOR
NIGHTTIME COOLING TO CONDENSE THE MOIST AIR AND PRODUCE FOG
AREAWIDE. DENSE FOG WITH VISIBILITY LESS THAN 1/4 MILE IS LIKELY
ALONG THE BALCONES ESCARPMENT (I-35 FROM GEORGETOWN TO SAN ANTONIO
AND U.S. 90 FROM SAN ANTONIO TO UVALDE) EARLY SUNDAY MORNING.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DENSE FOG ADVISORY MEANS VISIBILITY WILL FREQUENTLY BE REDUCED
TO LESS THAN 1/4 MILE. DRIVERS SHOULD SLOW DOWN...USE LOW BEAM
HEADLIGHTS...AND LEAVE PLENTY OF SPACE BETWEEN YOU AND OTHER
VEHICLES. JOGGERS AND WALKERS SHOULD WEAR BRIGHT-COLORED CLOTHING
WITH REFLECTIVE TAPE IF POSSIBLE...AND CARRY A FLASHLIGHT TO MAKE
OTHERS AWARE OF YOUR PRESENCE.