Severe Thunderstorm Warning 59, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
955 AM MST TUE AUG 17 2004

SOUTHEAST ARIZONA FORECAST DISCUSSION

.SYNOPSIS...SLIGHTLY DRIER AIR WILL MOVE INTO THE AREA BY WEDNESDAY
BEHIND A LOW PRESSURE SYSTEM TRACKING NORTH OF ARIZONA. THIS DRIER
AIR WILL DECREASE THE CHANCES OF DAILY THUNDERSTORMS. HIGH PRESSURE
WILL REGROUP OVER THE SOUTHERN ROCKIES AT THE WEEKEND... WITH A
RETURN TO A MOIST SOUTHERLY FLOW INTO ARIZONA. DAYTIME TEMPERATURES
WILL BE RUNNING AT OR SLIGHTLY BELOW NORMAL THIS WEEK.

&&

.DISCUSSION...THE UPPER LEVEL DISTURBANCE WHICH PRODUCED STRONG
THUNDERSTORMS YESTERDAY HAS SHIFTED TO THE EAST INTO NEW MEXICO.
THIS DISTURBANCE IS ASSOCIATED WITH A TROUGH WHICH EXTENDS FROM A
LOW PRESSURE CENTER NEAR THE GREAT SALT LAKE. THE SHIFT TO THE EAST
HAS OCCURRED DUE TO HIGH PRESSURE SOUTHWEST OF CALIFORNIA BUILDING
NORTHWARD. THIS HAS CAUSED A DECREASE IN PRECIPITABLE WATER OVER THE
LAST 24 HOURS IN SOUTHERN ARIZONA AS SEEN ON THE 12Z SOUNDINGS FROM
YUMA AND TUCSON. BOTH AREAS HAVE SEEN AS DECREASE OF ABOUT 2 TENTHS
OF AN INCH. BUT... ENOUGH MOISTURE REMAINS FOR THUNDERSTORMS TO ONCE
AGAIN DEVELOP LATER TODAY. THIS DRYING WILL CONTINUE THROUGH THE
WEEK AS THE RIDGE OF HIGH PRESSURE TAKES CONTROL. HOWEVER... THERE
IS A DIFFERENCE BETWEEN THE ETA AND GFS FORECAST MODEL SOLUTIONS
WITH THE STRENGTH OF THE HIGH. THE ETA MODEL BUILDS A STRONGER RIDGE
OVER CALIFORNIA AND NEVADA WHILE THE GFS WANTS TO HOLD ONTO A BAGGY
TROUGH EXTENDING OFF THE COAST OF CALIFORNIA. WITH EITHER SOLUTION
DRIER AIR IS STILL EXPECTED... BUT ENOUGH MOISTURE WILL LINGER FOR
SOME THUNDERSTORM ACTIVITY. AS THE WEEKEND BEGINS SO DOES AN
INCREASE IN MOISTURE FROM THE SOUTH AS THE RIDGE SHIFTS EASTWARD AND
PLACES SOUTHEASTERN ARIZONA IN A MORE FAVORABLE FLOW.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

EVANS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1155 AM MST TUE AUG 17 2004

AZZ019-029>035-180700-
NORTHERN GREENLEE COUNTY-UPPER GILA RIVER VALLEY-COCHISE COUNTY-
SOUTHEAST PINAL COUNTY-TUCSON METRO/MARANA/GREEN VALLEY-
SANTA CRUZ COUNTY-TOHONO OODHAM NATION-WESTERN PIMA COUNTY-
1155 AM MST TUE AUG 17 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...ACTIVITY WILL BE A LITTLE LESS TODAY IN THE WAKE OF THE
UPPER LEVEL DISTURBANCE THAT MOVED THROUGH THE AREA ON MONDAY.
HOWEVER...THERE WILL BE A SLIGHT RISK FOR SEVERE THUNDERSTORMS WITH
FLASH FLOODING STILL A THREAT.

DISCUSSION...THE AREA IS SLIGHTLY MORE STABLE AND DRIER THAN
YESTERDAY WITH THE AREA IN THE WAKE OF THE UPPER LEVEL DISTURBANCE
THAT MOVED THROUGH THE AREA. HOWEVER...THERE IS STILL ENOUGH
MOISTURE AROUND TO SUPPORT ISOLATED TO SCATTERED THUNDERSTORMS FROM
CENTRAL PIMA COUNTY EAST. THERE IS ALSO ENOUGH SHEAR IN THE
ATMOSPHERE TO SUPPORT ISOLATED SEVERE THUNDERSTORMS. THE THREAT FOR
FLASH FLOODING IS STILL ABOVE CLIMATOLOGY...ESPECIALLY IN AREAS THAT
HAVE BEEN HIT HARD OVER THE PAST 10 DAYS...LIKE CENTRAL PIMA
COUNTY...SANTA CRUZ AND COCHISE COUNTIES.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

DRIER WESTERLY FLOW ALOFT WILL OVERTAKE THE REGION STARTING
WEDNESDAY AND CONTINUE INTO THE FIRST HALF OF THE WEEKEND. STORMS
WILL BECOME MORE ISOLATED AND CONFINED NEAR THE MOUNTAINS BY FRIDAY.
THERE ARE MORE SIGNS THAT A SOMEWHAT MORE ACTIVE PATTERN WILL
DEVELOP LATE IN THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.