Severe Thunderstorm Warning 27, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-060545-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
245 PM MST SAT AUG 5 2000

.SYNOPSIS...
AN UPPER-LEVEL DISTURBANCE WILL MOVE SLOWLY ACROSS NORTHERN MEXICO
THIS WEEKEND.  AS A RESULT...AN INCREASE IN THUNDERSTORM ACTIVITY IS
EXPECTED OVER MAINLY SOUTH-CENTRAL ARIZONA TONIGHT. THE CHANCE FOR
MAINLY LATE AFTERNOON AND NIGHTTIME STORMS WILL CONTINUE OVER SOUTH
CENTRAL ARIZONA INTO AT LEAST THE MIDDLE OF NEXT WEEK AS A MORE
TYPICAL MONSOON FLOW BECOMES ESTABLISHED. TEMPERATURES WILL LOWER
SOMEWHAT DURING THE NEXT FIVE DAYS...BUT REMAIN ABOVE NORMAL.

.DISCUSSION...
STILL APPEARS THAT TONIGHT COULD BE AN ACTIVE NIGHT OVER THE ERN CWA.
ELY WAVE FROM NW MEX TO FAR W TEXAS CONTS TO PUSH WWD AND IS NOW
MOVING INTO ERN AZ. VERY IMPRESSIVE APPEARING FEATURE BASED ON IR AND
WATER VAPOR IMAGERY...AND IT IS ALREADY KICKING OFF IMPRESSIVE STORMS
ALONG THE CNTRL AND ERN RIM...WITH ADDITIONAL ONES FIRING OVER SERN
AZ. AS THIS WAVE MOVES WWD...UPPER HIGH HAS SHIFTED WEST WITH THE
MEAN WIND IN THE 700-300MB LAYER NOW FROM THE NNE. THIS IS ALLOWING
THE STORMS ALONG THE RIM TO MOVE DOWN INTO THE CNTRL DESERTS.
DEWPOINTS OVER THE CENTRAL DESERTS ARE STILL A LITTLE ON THE LOW
SIDE...GENLY IN THE MID 50S...BUT WITH THE DYNAMICS AND UPPER
DIFLUENCE ASSOCD WITH THE ELY WAVE...STILL FEEL THERE IS A CHANCE FOR
STORMS TO GET INTO THE ERN CWA...INCLUDING THE PHX METRO...TONIGHT.
AMS TOO DRY AND STABLE OVER THE WRN DESERTS...SHOULD SEE MOSTLY CLEAR
TO PARTLY CLOUDY SKIES THERE OVERNIGHT. NOT MUCH CHANGE FOR
SUNDAY...AS ADDITIONAL INVERTED TROFS/VORT MAXES ARE FORECAST TO
AFFECT SERN AZ AND THE ERN CWA...THE STEERING FLOW SHOULD STILL BE
NELY...AND THERE SHOULD BE SUFFICIENT MOISTURE AND INSTBY FOR ANOTHER
ROUND OF AFTN AND EVE THUNDERSTORMS. WILL CALL FOR A CHANCE FOR EVE
TSTMS OVER SCNTRL AZ SUN NIGHT...WITH A SLIGHT CHANCE FOR LATE AFTN
STORMS ON MON. FOR THE EXTENDED...TROFFING STARTS TO DEVELOP ALONG
THE W COAST...HELPING TO PUSH THE UPPER HIGH BACK TO NEAR THE FOUR
CORNERS...AND THEN A BIT E OF THAT POSITION...IN THE TUE THRU THU
TIME FRAME. AS THIS HAPPENS THE WRN CWA COMES UNDER THE INFLUENCE OF
A SWLY FLOW...WHICH ACTS TO DRY THE AMS SOMEWHAT. AS THIS HAPPENS THE
MOISTURE AND INSTABILITY WILL FOCUS OVER THE ERN CWA...AND WE WILL
RETURN TO A RATHER LOW GRADE STANDARD MONSOON FORECAST. THAT IS...A
CHANCE FOR MAINLY AFTN AND EVE STORMS OVER SCNTRL AZ...WITH MOSTLY
CLEAR TO PARTLY CLOUDY SKIES ELSEWHERE. 11

AZZ022>024-027-028-060130-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1122 AM MST SAT AUG 5 2000

...SLIGHT RISK FOR SEVERE THUNDERSTORMS OVER SOUTH-CENTRAL
ARIZONA THIS EVENING AND TONIGHT...

THE SLIGHT RISK AREA ENCOMPASSES MARICOPA...SOUTHERN GILA
...AND NORTHWEST PINAL COUNTIES...AND INCLUDES THE GREATER PHOENIX
METROPOLITAN AREA AS WELL AS THE CITIES OF GLOBE...COOLIDGE...CASA
GRANDE...GILA BEND AND WICKENBURG.

THE PRIMARY WEATHER THREAT FROM THUNDERSTORMS WILL BE STRONG...
DAMAGING STRAIGHT LINE WINDS TO OVER 60 MPH...BLOWING DUST THAT
COULD REDUCE VISIBILITIES TO LESS THAN ONE-QUARTER MILE...AND
INTENSE CLOUD TO GROUND LIGHTNING. LOCALLY HEAVY RAIN IS
POSSIBLE...BUT IT IS A LESSER THREAT.

SCATTERED STORMS ARE EXPECTED TO DEVELOP OVER SOUTHEAST ARIZONA...AS
WELL AS THE EAST-CENTRAL MOUNTAINS...THEN GRADUALLY WORK THEIR WAY
WESTWARD DURING THE LATE AFTERNOON AND EVENING HOURS. THE GREATEST
WEATHER THREAT WILL OCCUR DURING THE EVENING...BUT STORMS COULD
PERSIST PAST MIDNIGHT AND INTO THE MORNING HOURS.

STORM SPOTTER ACTIVATION MAY BE NECESSARY LATER TODAY AND TONIGHT.

CJB