Flash Flood Warning 28, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
223 PM MST THU JUL 31 2003

.SYNOPSIS...SOUTHEAST ARIZONA WAS CENTERED BETWEEN TWO SYSTEMS...AN
UPPER RIDGE OF HIGH PRESSURE TO OUR NORTH AND AN UPPER LOW PRESSURE
SYSTEM OFF THE NORTHERN BAJA PENINSULA. A WEAK DISTURBANCE NEAR THE
TIP OF THE BAJA PENINSULA WILL CONTINUE TO PUSH NORTH TOWARD
SOUTHERN ARIZONA TONIGHT...RESULTING IN SCATTERED MAINLY EVENING
THUNDERSTORMS. IN FACT...THE AIRMASS WILL REMAIN QUITE MOIST THE
NEXT COUPLE OF DAYS...RESULTING IN SCATTERED AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS. HIGH PRESSURE WILL THEN SHIFT EASTWARD
OVER NEW MEXICO AND INTO TEXAS BY SUNDAY ALLOWING A DRIER AIRMASS TO
FILTER INTO THE REGION EARLY NEXT WEEK. THIS WILL LEAD TO A GRADUAL
DECREASE IN THUNDERSTORM COVERAGE ACROSS ALL OF SOUTHEAST ARIZONA
NEXT WEEK.

.DISCUSSION...SYSTEM NEAR THE SOUTHERN TIP OF BAJA CONTINUES TO MAKE
SLOW PROGRESS NORTH. WATER VAPOR IMAGERY AND LIGHTNING DATA SHOW
SCATTERED CONVECTION WITHIN THE CONVERGENCE ZONE BETWEEN THE UPPER
LOW WEST OF BAJA AND THE HIGH OVER NEW MEXICO. KEMX RADAR CURRENTLY
DETECTING SCATTERED SHOWERS AND THUNDERSTORMS OVER A GOOD PORTION OF
MY COUNTY WARNING AREA WITH SOME OF THE STORMS POTENTIALLY POSING
PROBLEMS WITH REGARD TO FLOODING. MANY ARE BACK BUILDING AND HOURLY
RADAR ESTIMATES ARE INDICATING THAT A COUPLE OF THE STORMS ARE
SHOWING ISOLATED AMOUNTS BETWEEN 2 TO 3 INCHES.

ONE LARGE CELL OVER THE TOHONO OODHAM NATION IS DROPPING HEAVY RAIN
WITH RADAR ESTIMATES INDICATING AROUND 2 INCHES PER HOUR. WITH THIS
ADDITIONAL RAINFALL IT WILL ONLY EXACERBATE THE FLOODING PROBLEMS
FROM PREVIOUS RAINS. THEREFORE EVEN THOUGH THE WASHES AFFECTED
EARLIER IN THE WEEK WERE SHOWING SIGNS OF FALLING...THIS RAIN WILL
LIKELY CAUSE RISES IN THE STREAMS ONCE AGAIN. FLOOD WARNING FOR THIS
AREA WILL CONTINUE THROUGH 9 PM...BUT WILL LIKELY BE EXTENDED
THROUGH FRIDAY.

MODELS CONTINUE TO LIFT THE AFOREMENTIONED SYSTEM OVER SRN BAJA TO
THE YUMA AREA OVERNIGHT AND INTO CALIFORNIA ON FRIDAY AS THE UPPER
LOW WEST OF BAJA CONTINUES TO MOVE NORTHWEST. MEANWHILE THE HIGH
OVER NEW MEXICO AND EXTENDING BACK TO THE GREAT BASIN WILL BUILD TO
THE EAST AND SOUTH DURING THE WEEKEND...REACHING A POSITION
GENERALLY CENTERED NEAR EL PASO BY SATURDAY. AS THIS OCCURS A WEAK
TROUGH OUT AHEAD OF THE MAIN LOW IN THE PACIFIC WILL BE APPROACHING
THE WEST COAST WITH SOME HINT OF DRYING. BY EARLY NEXT WEEK MEDIUM
RANGE MODELS ARE ALL ADVERTISING SOUTHWEST FLOW AHEAD OF THE MAIN
TROUGH WITH SIGNIFICANT DRYING ANTICIPATED...BUT THE GFS IS THE MOST
ROBUST WITH THIS SOLUTION. HOWEVER...THE 00Z WAS NOT QUITE AS
AGGRESSIVE WITH THE DRYING AS WAS THE PREVIOUS RUN. THEREFORE WILL
KEEP THE TREND OF SCATTERED SHOWERS AND STORMS IN THE ZONES/GRIDS
THROUGH THE WEEKEND WITH STORMS DEVELOPING MORE ALONG THE
ARIZONA/NEW MEXICO BORDER BY THE WEEKEND. BY EARLY TO MID WEEK AS
SOME AMOUNT OF DRYING IS EXPECTED I HAVE DECREASED POPS TO GENERALLY
THE SLIGHT CHANCE CATEGORY.

MOLLERE

.TWC...FLOOD WARNING FOR CENTRAL PIMA COUNTY/ZONE 32 UNTIL 9 PM MST
THIS EVENING.

AZZ019-029>035-011400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1130 AM MST THU JUL 31 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...A HIGH PRESSURE RIDGE CONTINUES OVERHEAD CENTERED NEAR
THE FOUR CORNERS AREA. THIS HAS ALLOWED A MOIST SOUTHEAST FLOW TO
REMAIN ACROSS THE REGION. THE RESULT WILL BE SCATTERED SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND EVENING WITH THE BEST CHANCE
RESIDING OVER GREENLEE...GRAHAM...PINAL AND COCHISE COUNTIES.

DISCUSSION...SOUTHEAST FLOW ALOFT HAS ALLOWED THE PRECIPITABLE WATER
TO REMAIN OVER 1 INCH ACROSS SOUTHERN ARIZONA TODAY AND WILL PRODUCE
SCATTERED SHOWERS AND THUNDERSTORMS. AT 11 AM TODAY CLOUDS COVERED
MOST OF PIMA AND SANTA CRUZ COUNTIES WHICH WILL LIMIT THE
CONVECTION...HOWEVER A MAINLY CLEAR SKY FOR COCHISE...GRAHAM...
GREENLEE AND PINAL COUNTIES HAVE ALREADY ALLOWED TOWERING CU TO
DEVELOP OVER THE MOUNTAINS. HELPING THE CHANCES OF WIDESPREAD
THUNDERSTORMS TODAY WILL BE UPWARD MOTION AT THE LOWER LEVELS
COMBINED  WITH DIVERGENCE AT 250 MB. ELSEWHERE...CLOUD COVER WILL
DELAY THUNDERSTORM DEVELOPMENT UNTIL LATE THIS AFTERNOON OR INTO THE
EVENING. ONE OTHER CONSIDERATION IS A DISTURBANCE MOVING ALONG THE
EASTERN SIDE OF THE GULF OF CALIFORNIA. POSITIVE VORTICITY ADVECTION
ALONG WITH ADDITIONAL MOISTURE MAY BE ENOUGH TO START SIGNIFICANT
CONVECTION IN FAR WESTERN PIMA COUNTY DURING THE EARLY EVENING. SO
EXPECT A SLIGHTLY BETTER CHANCE THAN CLIMATOLOGY FOR SEVERE
THUNDERSTORMS AND HEAVY RAIN OVER GRAHAM...GREENLEE...EASTERN
PINAL...COCHISE AND FAR WESTERN PIMA COUNTIES. OTHERWISE...AT OR
BELOW CLIMATOLOGY IS EXPECTED.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

SEASONAL SCATTERED THUNDERSTORMS WITH THE NORMAL IMPLIED THREAT OF
HEAVY RAIN AND STRONG WINDS WILL CONTINUE THROUGH THE WEEK.

.SPOTTER INFORMATION STATEMENT...

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

EVANS