Dust Storm in Arizona, July 16, 2002

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
223 PM MST MON JUL 15 2002

.SYNOPSIS...HIGH PRESSURE ALOFT WILL CONTINUE OVER THE CENTRAL
ROCKIES THIS WEEK. THIS SYSTEM WILL KEEP SOUTHEAST ARIZONA IN A
FAVORABLE MONSOON PATTERN WITH A DAILY RISK OF AFTERNOON AND EVENING
THUNDERSTORMS.

.DISCUSSION...A NARROW BAND OF THICK CLOUDS CAUSED BY SOME MID LEVEL
CONVERGENCE EXTENDED FROM GBN EAST TO TUS AND WILLCOX LIMITING THE
AMOUNT OF SURFACE HEATING THERE. HOWEVER...CLOUD FREE SKIES TO THE
NORTH AND SOUTH OF THIS CONVERGENCE ZONE HAVE GIVEN WAY TO
THUNDERSTORMS...MAINLY ALONG THE EASTERN RIM INTO THE WHITE
MOUNTAINS AND IN THE HUACHUCA MOUNTAINS. THESE STORMS HAVE SHOWED
LITTLE PROGRESS SINCE AROUND NOON...BUT WILL NEED TO KEEP AN EYE ON
THE ACTIVITY IN CASE THEY MAKE A RUN TOWARD THE LOWER DESERTS. THE
STEERING FLOW IS LIGHTER THAN THE PAST FEW DAYS BUT STILL FROM A
FAVORABLE EASTERLY DIRECTION FOR CELLS TO PROPAGATE TOWARD TO LOWER
WESTERN DESERTS. HOWEVER...WOULD NOT EXPECT THIS TO HAPPEN UNTIL
LATE THIS EVENING OR POSSIBLY AFTER MID NIGHT. STILL THINK HEAVY
RAINFALL WILL BE THE MAIN CONCERN FROM THESE STORMS THROUGH TONIGHT.
OTHERWISE...NEXT SEVERAL DAYS STILL LOOK TYPICAL FOR THIS TIME OF
YEAR WITH THE HIGH PRESSURE CELL REMAINING NORTH OF US FOR A
CONTINUED EASTERLY FLOW ALOFT. HOWEVER...MODELS CONTINUED TO SHOW
SIGNS OF DEEPENING THE EASTERN PACIFIC TROUGH AND SHIFTING IT
CLOSER TO THE COAST. THIS WOULD TEND TO LEAD TO SOME DRYING ACROSS
OUR WESTERN ZONES AS A DEEPER SOUTHWESTERLY FLOW ALOFT SPREADS IN.
THUS...WILL CALL FOR LOWER POPS OUT WEST BY THURSDAY AND KEEP THE
HIGHER POPS IN THE EAST.

.TWC...NONE.