Severe Thunderstorm Warning 19, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
150 PM MST SAT JUL 14 2001

SYNOPSIS...A TROUGH OF LOW PRESSURE WILL REMAIN STATIONARY ALONG
THE WEST COAST FOR THE NEXT WEEK. THIS WILL BRING A LITTLE DRIER
SOUTHWEST FLOW OVER MUCH OF THE REGION. HIGH PRESSURE WILL REMAIN
NEARLY STATIONARY IN NEW MEXICO WHICH WILL CONTINUE TO PUSH SOME
MOISTURE INTO FAR EASTERN ARIZONA. LOOK FOR TEMPERATURES TO REMAIN
NEAR OR SLIGHTLY ABOVE NORMAL WITH A CHANCE OF AFTERNOON AND EVENING
THUNDERSTORMS.

DISCUSSION...STRONG THUNDERSTORMS WERE DEVELOPING ALONG THE WESTERN
EDGE OF THE CLOUD BAND THAT COVERED MOST OF OUR EASTERN ZONES THIS
MORNING. THE STORMS EXTENDED FROM NORTH OF TUCSON SOUTH TO NEAR
NOGALES. THESE STORMS WERE MOVING RATHER SLOWLY AND DEVELOPING IN
THE GENERAL SOME AREA...THUS POSING A THREAT FOR FLASH FLOODING THIS
AFTERNOON. THE STRONGER SOUTHWESTERLY FLOW ALOFT WAS HELPING
ORGANIZE THE STORMS BETTER TODAY THAN IN PREVIOUS DAYS...SO EXPECT
LONGER LIVED CELLS TRAINING ACROSS THE GREATER TUCSON METRO BETWEEN
2 PM AND 5 PM MST. OTHERWISE...EXPECT THE STORMS TO TAPER OFF
EARLIER THAN NORMAL THIS EVENING WITH VARIABLE CLOUDINESS OVERNIGHT.
THE TROUGH ALONG THE WEST COAST WILL SERVE TO MAINTAIN A DRY
SOUTHWESTERLY FLOW ACROSS WESTERN ARIZONA THE NEXT FEW DAYS.
HOWEVER...EXPECT SUFFICIENT MOISTURE TO LINGER ACROSS OUR EASTERN
ZONES TO SUPPORT A CHANCE OF THUNDERSTORMS GENERALLY THROUGH THE
FORECAST PERIOD. TUCSON...AS ALWAYS...WILL BE ON THE WESTERN FRINGES
OF THIS MOISTURE. ANOTHER FEATURE THAT MAY AFFECT OUR NECK OF THE
WOODS WILL BE A LARGE UPPER LOW OVER MEXICO. THE SYSTEM IS FORECAST
BY THE AVN/MRF TO TRACK WESTWARD INTO BAJA AND THEN LIFT NORTH
ENTERING SOUTHERN ARIZONA IN A WEAKENING STATE MONDAY NIGHT. THIS
SYSTEM COULD ENHANCE OUR CHANCES OF THUNDERSTORMS MONDAY EVENING AND
NIGHT. OTHERWISE...JUST A LOW GRADE THUNDERSTORM FORECAST jCAN BE
EXPECTED. HIGH TEMPERATURES SHOULD ALSO DROP A FEW DEGREES WITH THE
LOWER HEIGHT VALUES...AND THE DRIER AIRMASS IN PLACE SHOULD RESULT
IN SLIGHTLY COOLER OVERNIGHT LOWS.

.TWC...NONE.

AZZ019-029>035-150700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1145 AM MST SAT JUL 14 2001

.SYNOPSIS...DRIER AIR HAS STARTED TO WORK ITS WAY INTO WESTERN
PORTIONS OF SOUTHERN ARIZONA...ESPECIALLY IN THE MID LEVELS. DEEPER
MOISTURE CONTINUES ACROSS EASTERN PORTIONS OF THE FORECAST AREA.
AGAIN THE HIGHER TERRAIN WILL PROVIDE THE FOCUSING MECHANISM TO
SPARK THUNDERSTORM DEVELOPMENT. WITH LESS OVERALL MOISTURE TO WORK
WITH...AND HIGHER WINDS ALOFT THE THREAT OF FLASH FLOODING WILL BE
NEAR CLIMATOLOGY ACROSS ALL OF SOUTHERN ARIZONA. WITH SOUTHWEST FLOW
AT MID AND UPPER LEVELS PULLING IN DRIER AIR ALOFT...THE THREAT OF
SEVERE WEATHER IS LOW.

.DISCUSSION...LOOK FOR THUNDERSTORMS TO DEVELOP OVER THE HIGHER
TERRAIN DURING THE AFTERNOON HOURS...MAINLY FROM TUCSON EAST. THE
MORNING TUCSON UPPER AIR SOUNDING INDICATED SOMEWHAT DRIER AIR IN
PLACE COMPARED TO YESTERDAY...WITH A PRECIPITABLE WATER VALUE OF
1.23 INCHES. MID LEVEL STEERING FLOW IS STRONG ENOUGH FOR THE STORMS
TO MOVE OFF THE MOUNTAINS AND INTO THE VALLEYS...HOWEVER THE
STRONGER FLOW WILL REDUCE THE THREAT OF FLASH FLOODING TO NEAR
CLIMATOLOGY ACROSS ALL OF SOUTHERN ARIZONA EXCEPT FAR EASTERN
PORTIONS WHERE DEEPER MOISTURE REMAINS. THE THREAT OF SEVERE
THUNDERSTORMS WILL BE NEAR CLIMATOLOGY TODAY OVER A GOOD PORTION OF
SOUTHEAST ARIZONA...WITH A BELOW NORMAL THREAT OVER FAR WESTERN PIMA
COUNTY. THE HIGHEST THREAT OF SEVERE WEATHER WILL BE OVER EASTERN
PORTIONS OF SOUTHEAST ARIZONA (FAR EASTERN PIMA...COCHISE AND GRAHAM
COUNTIES) WHERE DIFFERENTIAL HEATING DUE TO MORNING CLOUDS AND THE
BOUNDARY BETWEEN DRIER AND MORE MOIST AIR EXISTS.

STORM MOTION WILL BE TOWARDS THE NORTHEAST AT 10 MPH.

ZELL