360 
FXUS65 KTWC 042114
AFDTUS

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
212 PM MST WED AUG 4 1999

SYNOPSIS...THE BOUNDARY BETWEEN DEEP MONSOON MOISTURE TO THE EAST 
AND DRIER AIR TO THE WEST WILL OSCILLATE BACK AND FORTH ACROSS THE 
REGION THROUGH THE WEEKEND. THE BOUNDARY...WHICH HAS MOVED WEST OF 
TUCSON TODAY...WILL SHIFT BACK TO THE EAST ON FRIDAY...ONLY TO MOVE 
BACK TO THE WEST THIS WEEKEND. AREAS TO THE EAST WILL HAVE A 
CONTINUED THREAT OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS... 
WHILE AREAS TO THE WEST SEE ONLY ISOLATED STORMS AT MOST. 

DISCUSSION...ITS BEEN AN INTERESTING AFTERNOON SO FAR. CELLS POPPED 
QUICKLY NEAR TUCSON AND HAVE CONSOLIDATED INTO A LINE ALONG THE 
UPPER LEVEL SHEAR AXIS FROM FLORENCE TO THE WEST SIDE OF THE TUCSON 
MOUNTAINS. WE EVEN HAD 1/2 HAIL AT THE DESERT MUSEUM AROUND 130 PM. 
WARM-TOP CELLS ARE ALSO DEVELOPING IN THE CORE OF A MID LEVEL 
CIRCULATION NEAR DOUGLAS AND ARE HEADING SLOWLY NW. THE SOMEWHAT 
LIMITED HEATING MAKES ME LEAN AGAINST A WATCH, BUT IF THE SHEAR AXIS 
STALLS OR THINGS GET MORE ORGANIZED UNDERNEATH THE CIRCULATION, WE 
MAY HAVE TO DO SOMETHING. RIGHT NOW, IM THINKING HEAVY DOWNPOUR 
WORDING WILL SUFFICE.

MESOETA/ETA THE WINNER TODAY BASED ON SHORT-TERM TRENDS. TOMORROW IS 
SOMEWHAT IN DOUBT BECAUSE A BIG NIGHT MAY MESS THINGS UP. CONTINUED 
UPPER DIVERGENCE COULD SUSTAIN THINGS WELL INTO THE MORNING, WHICH 
WE HAVE SEEN TO THE EAST SO FAR THIS WEEK. THE OUTFLOW MOVING UP THE 
GULF OF CALIFORNIA SEEMS TO BE DOING ITS JOB WITH 18Z PHX SOUNDING 
WETTER THAN BEFORE AND ISOLATED CELLS POPPING UP NEAR KGBN. IF WE 
CAN GET A FAIR AMOUNT OF SUN, THETA-E RIDGE AND UPPER SHEAR AXIS 
WILL ALLOW PLENTY OF DEVELOPMENT. EVEN THE LEAST-AGGRESSIVE ETA 
BRING THE UPPER LOW OFF THE WA/OR COAST CLOSE ENOUGH TO SWITCH OUR 
FLOW TO THE SW ON FRI. THAT SHOULD BE OUR DOWN DAY. AS FOR THE 
EXTENDED, I LIKE THE MRF SINCE AN UPPER LOW OFF THE PACIFIC COAST IS 
PRETTY RARE FOR THIS TIME OF YEAR AND SHOULD FILL/RETROGRADE RATHER 
QUICKLY DUE TO THE RELATIVELY WARM WATER. THE UPPER TROUGH IN THE NE 
U.S. ALSO TELECONNECTS TO AT LEAST A MODERATE RIDGE TO OUR EAST. 
WELL WORD FOR A MID-GRADE MONSOON SITUATION, PARTICULARLY FROM 
TUCSON EAST. PYTLAK
 
.TWC...NONE.