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Organization: National Weather Service
Date: July 17, 2009
Heat Wave to Persist Through the Weekend
400 PM PDT FRI JUL 17 2009
CONTINUED HOT TEMPERATURES EXPECTED TO PERSIST ACROSS INLAND
AREAS THROUGH AT LEAST EARLY NEXT WEEK...
A STRONG UPPER LEVEL HIGH PRESSURE SYSTEM CENTERED OVER THE DESERT
SOUTHWEST WILL CONTINUE TO BRING HOT TEMPERATURES ACROSS INLAND
AREAS OF SOUTHERN CALIFORNIA THROUGH AT LEAST EARLY NEXT WEEK. HIGH
TEMPERATURES IN THE VALLEYS ARE GENERALLY EXPECTED TO RANGE BETWEEN
95 AND 105 DEGREES...WITH SUNDAY EXPECTED TO BE THE WARMEST DAY.
HIGH TEMPERATURES IN THE ANTELOPE VALLEY ARE EXPECTED TO RANGE
BETWEEN 102 AND 110 DEGREES THROUGH SUNDAY...APPROACHING RECORD
LEVELS.
MOUNTAIN HIGH TEMPERATURES ARE GENERALLY EXPECTED TO RANGE BETWEEN
90 AND 107 DEGREES. THE COMBINATION OF THESE HOT TEMPERATURES WITH
SUFFICIENT MOISTURE WILL CONTINUE TO GENERATE HEAT INDEX VALUES OF
100 DEGREES OR GREATER THROUGH SUNDAY...RESULTING IN EXCESSIVE HEAT
WARNINGS BEING POSTED FOR THE MOUNTAINS OF SOUTHWEST CALIFORNIA.
HEAT INDEX IS A MEASURE OF DISCOMFORT LEVEL BASED ON THE COMBINATION
OF TEMPERATURE AND HUMIDITY. AT THIS TIME...IT APPEARS THAT HEAT INDEX
VALUES WILL REMAIN BELOW CRITICAL HEAT WARNING THRESHOLDS FOR THE
VALLEYS AND ANTELOPE VALLEY THROUGH SATURDAY...BUT WARNINGS MAY BE
NEEDED BY SUNDAY FOR PORTIONS OF THE VALLEYS AS MOST AREAS ARE
EXPECTED TO RECEIVE THEIR HIGHEST TEMPERATURES OF THIS CURRENT HEAT
WAVE.
TEMPERATURES ALONG THE COASTAL PLAIN HAVE BEEN MODERATED BY THE
COMBINATION OF ONSHORE FLOW AND A PERSISTENT MARINE LAYER. HOWEVER
OVER THE WEEKEND...THERE IS EXPECTED TO BE LESS MARINE INFLUENCE
AND WEAKER ONSHORE FLOW. AS A RESULT...TEMPERATURES WILL INCREASE
OVER THE INTERIOR PORTIONS OF THE COASTAL PLAIN...WITH WARMEST
LOCATIONS EXPECTED TO CLIMB ABOVE 90 DEGREES.
THE VERY WARM AIR MASS COMBINED WITH INCREASING MOISTURE WILL ALSO
BRING WARMER MINIMUM TEMPERATURES THROUGH THE WEEKEND. MANY
VALLEY...MOUNTAIN...AND DESERT LOCATIONS WILL HAVE MINIMUM TEMPERATURES
REMAINING IN THE 70S...MINIMIZING THE RELIEF FROM HEAT STRESS IN THESE
AREAS.
THERE IS HIGH CONFIDENCE THAT THIS CURRENT HEAT WAVE WILL PERSIST ACROSS
INLAND AREAS THROUGH AT LEAST EARLY NEXT WEEK. LONG RANGE COMPUTER
MODELS ARE CONTINUING TO INDICATE THE POTENTIAL FOR A LONG DURATION
HEAT WAVE ACROSS INLAND AREAS...WITH TEMPERATURES LIKELY REMAINING
ABOVE NORMAL FOR VALLEYS...MOUNTAINS...AND DESERTS THROUGH MUCH OF
NEXT WEEK.
THE PROLONGED HEAT WAVE THAT IS ANTICIPATED FOR INLAND AREAS OF
SOUTHWEST CALIFORNIA CAN BE DANGEROUS...ESPECIALLY FOR THE
ELDERLY...SMALL CHILDREN...AND PETS. IF YOU PLAN ON BEING
OUTDOORS...REMEMBER TO REMAIN HYDRATED BY DRINKING PLENTY OF
WATER...WEAR LOOSE-FITTING CLOTHING AND A HAT...AND REMAIN IN THE
SHADE OR INDOORS AS MUCH AS POSSIBLE.
NEVER LEAVE CHILDREN OR PETS IN CARS WITH THE WINDOWS UP OR EVEN
CRACKED DURING THE DAY...EVEN FOR A VERY SHORT TIME...AS
TEMPERATURES CAN QUICKLY REACH LETHAL LEVELS.
