Severe Thunderstorm Warning 38, NWS Phoenix, AZ

AZZ020>028-CAZ030>033-120545-

SOUTHWEST ARIZONA/SOUTHEAST CALIFORNIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
235 PM MST FRI AUG 11 2000

.SYNOPSIS...
A STATIONARY UPPER LEVEL DISTURBANCE DRAPED ACROSS ARIZONA WILL
AFFECT THE SOUTH CENTRAL AND SOUTHWEST PORTIONS THE NEXT COUPLE OF
DAYS. THIS IMPULSE WILL HELP TO TRIGGER THUNDERSTORMS...FIRST ALONG
THE HIGHER TERRAIN...WITH STEERING FLOWS HELPING TO MOVE THE STORMS
SOUTHWEST INTO THE LOWER DESERTS IN THE EVENINGS. MEANWHILE...HIGH
PRESSURE ALOFT WILL DRIFT NORTHWARD THE NEXT FEW DAYS AND WILL HELP
TO IMPORT ADDITIONAL MOISTURE INTO THE STATE. BY EARLY NEXT WEEK...
SUFFICIENT FLOW WILL BE PRESENT TO GIVE A THREAT OF AFTERNOON AND
EVENING THUNDERSTORMS ALL THE WAY INTO SOUTHEAST CALIFORNIA.

.DISCUSSION...
NEW 18Z MESO-ETA CONTINUES TO ADVERTIZE PRESENCE OF INVERTED VORT
TROF DRAPED NE-SW ACROSS AZ. THIS FEATURE GAVE CONSIDERABLE MID LEVEL
CONVERGENCE EARLIER TODAY...AS NOTED BY PERSISTENT LINE OF SHOWERS
AND THUNDERSTORMS NEAR ITS VICINITY. BELIEVE THIS FEATURE WAS ALSO
HELPING TO TRIGGER LARGE MCS ALONG AZ/MEX BORDER THIS AFTERNOON.
MEANWHILE...MESO-ETA...ET AL...IS CONTINUING TO FORECAST FAVORABLE
STEERING WINDS TO HELP PROPOGATE STORMS OFF THE RIM INTO THE HIGH
THETA-E AIRMASS NOW IN PLACE OVER THE DESERTS TONIGHT. RADAR VWP AND
SATELLITE TRENDS ALSO SEEM TO BE BEARING THIS FAVORABLE MOTION OUT.
SO...WENT WITH RELATIVELY HIGH POPS TONIGHT FOR PHX...40 PCT...AND
ALSO ISSUED A HAZARDOUS WEATHER OUTLOOK...MAINLY FOR HEAVY RAIN...
OVER MARICOPA...GILA AND PINAL PORTIONS OF CWFA. AFTER TONIGHT...
AMOUNT OF CONVECTION WILL DEPEND ON DEBRIS CLOUD SHIELDS...HOW MUCH
INSTABILITY IS RELEASED...AS WELL AS IF WE CAN KEEP THE NELY STEERING
FLOW. ANOTHER POSSIBLE PLAYER IN WEEKEND CONVECTION WILL BE WHETHER
WE CAN GET A SURGE TONIGHT FROM THE BORDER MCS...WHICH CONTINUES TO
PROPOGATE WWD...PERHAPS ENDING UP OUT OVER NRN GULF??  WILL OPT TO
KEEP LOW GRADE SCT POPS IN PLACE OVER DESERTS AFTER TONIGHT...MAINLY
IN THE EVENING...AND TAKE THREAT ALL THE WAY TO RIVER AND FAR SE CA
BY SATURDAY NIGHT. DURING THE EXTENDED...H5 RIDGE AXIS SETS UP TO OUR
N...OPENING THE DOOR FOR ELY FLOW TO MAKE IT ALL THE WAY INTO WRN
CWFA. HAVE DECIDED TO INCLUDE CHANCE OF TSTMS ALL THE WAY OUT INTO CA
ZONES DURING 3 TO 5 DAY PERIOD.    ESTLE

AZZ022>024-027-028-120130-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
1140 AM MST FRI AUG 11 2000

A MODERATE RISK OF THUNDERSTORMS WITH LOCALLY HEAVY RAIN OVER MUCH
OF SOUTH CENTRAL ARIZONA LATER THIS AFTERNOON AND EVENING...

THE MODERATE RISK AREA INCLUDES ALL OF MARICOPA COUNTY AS WELL
AS SOUTHERN GILA AND NORTHWEST PINAL COUNTIES. THIS INCLUDES
THE GREATER PHOENIX AREA...AS WELL AS CASA GRANDE...COOLIDGE...GLOBE
...MIAMI...WICKENBURG AND GILA BEND.

AN UPPER LEVEL DISTURBANCE OVER EASTERN ARIZONA WILL SERVE TO ACT AS
A TRIGGER FOR SCATTERED SHOWERS AND THUNDERSTORMS OVER THE MODERATE
RISK AREA THIS AFTERNOON AND EVENING. LOCALIZED RAINFALL AMOUNTS OF
OVER AN INCH PER HOUR ARE POSSIBLE. IN ADDITION...GUSTY WINDS TO
OVER 40 MPH ARE LIKELY...WHICH COULD LEAD TO AREAS OF REDUCED
VISIBILITIES IN BLOWING DUST IN THE DESERTS.

STORM SPOTTER ACTIVATION MAY BE NECESSARY LATER TODAY.

ESTLEc