Severe Thunderstorm Warning 16, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
250 PM MST FRI JUL 13 2001

SYNOPSIS...HIGH PRESSURE TO OUR EAST WILL CONTINUE TO PROVIDE A
MOIST SOUTHERLY FLOW INTO ARIZONA. HOWEVER...A SOMEWHAT DRIER
SOUTHWEST FLOW WILL DEVELOP THIS WEEKEND AS A STORM SYSTEM CROSSES
THE NORTHERN ROCKIES...WHILE HIGH PRESSURE SHIFTS INTO WESTERN NEW
MEXICO.

DISCUSSION...UPPER LOW PRESSURE CIRCULATION OVER NORTHERN BAJA ALONG
WITH A SHARP MOISTURE GRADIENT ACROSS OUR EASTERN ZONES WERE THE
MAIN FEATURES TO FOCUS ON THIS EVENING. LATEST RADAR AND SATELLITE
IMAGERY INDICATED SCATTERED THUNDERSTORMS STRETCHING FROM THE WHITE
MOUNTAINS SOUTH ALONG THE MOUNTAIN RIDGE LINES TO NEAR DOUGLAS.
OTHER STORMS WERE FORMING ACROSS SOUTHWESTERN ARIZONA IN THE
VICINITY OF THE UPPER LOW. THE STORMS WERE STILL RATHER ISOLATED IN
NATURE...BUT MUCH STRONGER AND MORE WIDESPREAD THAN THE PAST FEW
DAYS. THE PRIMARY CONCERN FROM THESE THUNDERSTORMS WILL BE LOCALLY
HEAVY RAINFALL...BUT STORMS DEVELOPING ALONG THE MOISTURE GRADIENT
ACROSS COCHISE...GRAHAM...AND GREENLEE COUNTIES COULD PRODUCE STRONG
DOWNBURST WINDS. DECENT UPWARD VERTICAL MOTION ASSOCIATED WITH THE
LOW PRESSURE SYSTEM OVER NORTHERN BAJA MAY HELP SUSTAIN CONVECTION
THROUGH THE NIGHT TIME HOURS...ESPECIALLY ACROSS CENTRAL AND WESTERN
PIMA COUNTY. OTHERWISE...EXPECT MOST OF THE STORMS TO DISSIPATE BY
MIDNIGHT. LATEST MODELS CONTINUED TO SHOW A DRYING TREND AS A
MODERATE SOUTHWESTERLY FLOW ALOFT SPREADS INTO THE WESTERN ONE-HALF
OF ARIZONA. MRF MODEL WAS STILL SUGGESTING SOME POSSIBLE MOISTURE
SUPPLY LINGERING ACROSS FAR EASTERN ARIZONA FOR A CONTINUED CHANCE
OF AFTERNOON AND EVENING MOUNTAIN THUNDERSTORMS THROUGH NEXT WEEK.

.TWC...NONE.

AZZ019-029>035-140700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1100 AM MST FRI JUL 13 2001

.SYNOPSIS...DEEP MONSOON MOISTURE CONTINUES IN PLACE ACROSS MOST OF
SOUTHEAST ARIZONA...WITH SOMEWHAT DRIER AIR WORKING INTO FAR EASTERN
PORTIONS OF THE REGION ALONG THE NEW MEXICO BORDER. WITH DAYTIME
HEATING AND GOOD MOISTURE...THE HIGHER TERRAIN WILL PROVIDE THE
FOCUSING MECHANISM TO SPARK THUNDERSTORM DEVELOPMENT. THE PRIMARY
THREAT ACROSS SOUTHEAST ARIZONA TODAY WILL BE A SLIGHTLY ELEVATED
THREAT OF FLASH FLOODING OVER THE HIGHER TERRAIN. WITH THE
COMBINATION OF MORNING CLOUDINESS AND CLOUDS SPREADING OUT AHEAD OF
ANY STORMS THAT DEVELOP...THE THREAT OF SEVERE WEATHER IS LOW.

.DISCUSSION...LOOK FOR THUNDERSTORMS TO DEVELOP OVER THE HIGHER
TERRAIN DURING THE AFTERNOON HOURS. THE MORNING TUCSON UPPER AIR
SOUNDING INDICATED A VERY MOIST ATMOSPHERE...WITH A PRECIPITABLE
WATER VALUE OF 1.50 INCHES. WEAK SOUTHERLY FLOW AT MID-LEVELS WILL
PREVENT THUNDERSTORMS FROM MOVING OFF OF THE MOUNTAINS INTO THE
VALLEYS UNTIL LATE THIS AFTERNOON AND EVENING. IN ADDITION...A
STRONGER FLOW ALOFT WILL PUSH THE THUNDERSTORM ANVILS INTO THE
VALLEYS...REDUCING SOLAR INSOLATION THERE AND THUS INHIBITING
THUNDERSTORM DEVELOPMENT. THEREFORE...THE THREAT OF FLASH FLOODING
WILL BE SLIGHTLY GREATER THAN CLIMATOLOGY OVER THE MOUNTAINS...AND
NEAR CLIMATOLOGY ELSEWHERE. THE THREAT OF SEVERE THUNDERSTORMS WILL
BE BELOW CLIMATOLOGY TODAY OVER A GOOD PORTION OF SOUTHEAST
ARIZONA...WITH A NEAR NORMAL THREAT OVER FAR WESTERN PIMA COUNTY.
THE HIGHEST THREAT OF SEVERE WEATHER WILL BE OVER FAR EASTERN
PORTIONS OF SOUTHEAST ARIZONA...IN COCHISE...GRAHAM AND GREENLEE
COUNTIES.

STORM MOTION WILL BE TOWARDS THE NORTH-NORTHWEST AT 10 MPH.

ZELL