Severe Thunderstorm Warning 51, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
230 PM MST TUE JUL 27 1999

SYNOPSIS...ANOTHER SUBTROPICAL WEATHER DISTURBANCE IS EXPECTED TO
MOVE INTO SOUTHEAST ARIZONA TODAY...RESULTING IN NUMEROUS
THUNDERSTORMS...SOME WITH LOCALLY HEAVY RAIN. THUNDERSTORM ACTIVITY
WILL DECREASE SOMEWHAT BY WEDNESDAY. HIGH PRESSURE WILL REMAIN OVER
THE EASTERN GREAT BASIN THROUGH THE END OF THE WEEK...FOR THE
CONTINUED THREAT OF MAINLY AFTERNOON AND EVENING THUNDERSTORMS.

DISCUSSION...CAP/INVERSION NEAR 700 MB HAS PRODUCED A SLOW START TO
THUNDERSTORM ACTIVITY THIS AFTERNOON. BUT SUNNY SKIES AND AFTERNOON
HEATING WILL BREAK THE INVERSION. SPC HAS AREA UNDER A SLIGHT CHANCE
OF SEVERE WEATHER THIS AFTERNOON. SO MAY HAVE TO DEAL WITH ISOLATED
DAMAGING WINDS IN ADDITION TO FLASH FLOODING. WATER VAPOR SHOWS LOTS
OF CONVECTIVE ACTIVITY NEAR THE CENTER OF THE TROUGH AND NORTHWARD
TO NEAR EL PASO. BOTH ETA/NGM MOVE THE WAVE INTO CENTRAL
ARIZONA...AND MOVEMENT OF THIS SYSTEM SEEN ON THE WATER VAPOR
IMAGERY SEEMS TO CONFIRM THIS.  SOUTHEAST ARIZONA WILL BE ON THE
BACKSIDE OF THE TROUGH WEDNESDAY. WITH NO DYNAMICS TO WORK WITH
STORMS WILL HAVE TO TRIGGER ON AFTERNOON HEATING...THUS WEDNESDAY
MAY BE A LOW GRADE MONSOON DAY. THURSDAY THROUGH THE EXTENDED PERIOD
MODELS MAINTAIN EASTERLY OR NORTHEASTERLY FLOW WITH THE HIGH CENTER
NORTH OF TUCSON. ANOTHER EASTERLY WAVE COULD PUSH THROUGH AT ANY
TIME. WITHOUT ANY CONFIDENCE ON TIMING OF FEATURES...WILL KEEP A
STANDARD MONSOON FORECAST GOING.

.TWC...FLASH FLOOD WATCH UNTIL 03Z ZONES 29,30,32,33,34,AND 35.