Flash Flood Warning 10, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
228 PM MST FRI JUL 9 1999

SYNOPSIS...HIGH PRESSURE OVER THE FOUR CORNERS WILL KEEP SOUTHERN
ARIZONA IN AN ACTIVE MONSOON PATTERN THROUGH EARLY NEXT WEEK. A WEAK
DISTURBANCE...EXTENDING FROM WESTERN PIMA COUNTY INTO NORTHEAST
SONORA PROVINCE...WILL BE THE MAIN FOCUS FOR STORMS TONIGHT. A COLD
FRONT DROPPING SOUTH THROUGH NEW MEXICO...COMBINED WITH AN UPPER
LEVEL DISTURBANCE BEHIND THE FRONT...WILL ENHANCE THUNDERSTORM
DEVELOPMENT SATURDAY AFTERNOON AND NIGHT.

DISCUSSION...HOPE EVERYONE ENJOYED OUR DOWN DAY YESTERDAY.
DEFINITELY DONT LIKE RADAR AND SATELLITE TRENDS AT THE MOMENT.
CELLS TO OUR SOUTH HAVE BEEN TAKING ONLY 15 MINUTES TO GO FROM
NOTHING TO 65DBZS. THEYRE ALSO LOOKING VERY WET AND ARE LINING
UP ALONG A WEAK SHEAR AXIS EXTENDING FROM NEAR GILA BEND TO SOUTH
OF DOUGLAS. THE CELLS WERE HOLDING ON THE MOUNTAINS INITIALLY, BUT
ARE NOW BECOMING MORE NUMEROUS IN THE VALLEYS AND ARE STARTING TO
TRAIN. OTHER CONCERN IS WITH STORMS DEVELOPING OVER THE WHITES.
THEYRE TRYING TO PROPAGATE OFF THE RIM, BUT THE FLOW LOOKS TOO WEAK
TO START A FULL SQUALL LINE GOING. THEYLL HAVE TO BE WATCHED,
THOUGH, CONSIDERING THE EVOLVING SITUATION TO OUR NE.

THE MOST INTERESTING FEATURE THIS AFTERNOON IS THE COLD FRONT
PRESSING SOUTHWEST ACROSS NEW MEXICO. THE FRONT IS VERY IMPRESSIVE
FOR JULY WITH 24HR PRESSURE RISES ON THE ORDER OF 11MB/24HRS ALONG
THE FRONT RANGE. BASED ON THE RISES AND CURRENT SPEED, IT WILL
ARRIVE IN THE WHITES AROUND 06Z AND MAY EVEN MAKE IT TO TUCSON JUST
AFTER 12Z. BEST DYNAMICS ROTATING AROUND THE HIGH CENTER DONT
ARRIVE UNTIL LATE TOMORROW AFTERNOON ACCORDING TO THE AVN. HAVE GONE
ALONG WITH THAT SOLUTION SINCE THE ETA IS TOO STRONG WITH THE
ANTICYCLONIC CIRCULATION OVER NM WHILE THE NGM BRINGS THE DYNAMICS
ACROSS A LITTLE FAST. USING ANY OF THE MODELS, HOWEVER, WERE
LOOKING AT A VERY ACTIVE 36HRS WITH A RELATIVE DOWN DAY ON SUNDAY.

FOR THE SHORT TERM, WELL GO AHEAD WITH A FLASH FLOOD WATCH SOUTH
THE SOUTHERN CWA. THIS AREA HAS BEEN RAKED SINCE MONDAY AND ITS
SMACK DAB IN THE MIDDLE OF THE TRAIN. WITH THE FRONT PRESSING IN
LATER ON, WELL DROP TIMING MENTIONS AND BROAD BRUSH THE STORMS ALL
NIGHT LONG. WE SHOULD GET A BREAK TOMORROW MORNING, BUT NOT FOR LONG
AS NE FLOW INCREASES BEHIND THE FRONT AND RELOADS THE ATMOSPHERE.
THUS WELL RETAIN THE WORDING AND TIMING MY PREDECESSOR USED FOR
TOMORROW, AND EXTEND STRONG WORDING INTO SAT NIGHT ALONG WITH THE
HIGH POPS. BASED ON TEMPS THE PAST FEW DAYS AND AMOUNT OF MOISTURE
AROUND, IT WILL BE DIFFICULT TO WARM UP VERY MUCH. HAVE LOWERED
HIGHS CLOSER TO PERSISTENCE. EXTENDED STILL LOOKS WET WITH ENSEMBLES
KEEPING THE 4-CORNER HIGH AS FAR OUT AS DAY 10. PYTLAK

.TWC...FLASH FLOOD WATCH UNTIL MIDNIGHT ZONES 31/32/SW 33/34/S 35.