Severe Thunderstorm Warning 29, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
230 PM MST THU JUL 24 2003

.SYNOPSIS...HIGH PRESSURE WILL REMAIN OVER THE FOUR CORNERS REGION
INTO THE WEEKEND. DISTURBANCES ROTATING AROUND THE HIGH WILL ENHANCE
THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS TONIGHT AND AGAIN
FRIDAY. AN INCREASE IN STORMS IS EXPECTED SUNDAY AND MONDAY AS THE
HIGH PRESSURE CENTER WEAKENS AND A STRONGER DISTURBANCE MOVES TOWARD
SOUTHEAST ARIZONA.

.DISCUSSION...KEMX WSR-88D DETECTED ISOLATED MOSTLY LESS THAN 40 DBZ
ECHOES NEAR THE WHITE/CHIRICAHUA/PINALENO MOUNTAINS AT 2110Z.
SCATTERED STRONG STORMS WERE ALSO DETECTED FROM JUST S KOLS ACROSS
NRN SONORA. ECHOES WERE MOVING/DEVELOPING SLOWLY NWWD. CONVECTIVE
DEVELOPMENT EXPECTED ACROSS SW NM/EXTREME SE AZ/NRN SONORA DURING
THE NEXT FEW HOURS IN REGION OF STRONGLY DIFLUENT H5-H3 FLOW.
BELIEVE ACTIVITY WILL WANE ACROSS ERN SECTIONS THIS EVENING BUT
SCENARIO FOR CONTINUED NRN SONORA DEVELOPMENT MAY PROVIDE NWWD
ADVANCING OUTFLOW SUFFICIENT TO MAINTAIN SHOWERS/THUNDERSTORMS
CENTRAL/WRN SECTIONS EVEN BEYOND MIDNIGHT. SIMILAR DEVELOPMENT
EXPECTED FRI AFTERNOON AND ESPECIALLY FRI NIGHT GIVEN PROGGED H3
OMEGA/DIVERGENCE/TOTAL DEFORMATION FIELDS. 24/12Z GFS DEPICTED
IMPRESSIVE UPPER LOW/VORT MAX TO MOVE ACROSS NE AZ SUN AFTERNOON
THEN SWWD ACROSS CENTRAL/SW AZ BY MON AS FOUR CORNERS HIGH SHIFTS
TOWARD NV. PER COORD WITH WFO/S PSR/FGZ WILL OPT FOR INCREASED POPS
SUN-MON AND WILL REFLECT 50 PERCENT POP TUS VICINITY SUN NIGHT.
FAIRLY ACTIVE PATTERN SHOULD CONTINUE INTO MID-WEEK AS SE AZ TO
REMAIN UNDER DIFLUENT FLOW ALOFT BETWEEN GREAT BASIN UPPER HIGH AND
LOWER PRESSURE OVER OLD MEXICO. DAYTIME MAX TEMPS FRI-SAT EXPECTED
TO REMAIN CLOSE TO SEASONAL NORMALS FOR LATE JULY. CONFIDENCE QUITE
LOW REGARDING FORECAST MAX TEMPS SUN-MON THAT WILL BE PROBLEMATIC
AND DEFINITELY DEPEND UPON CLOUD COVER AND PRECIP. HAVE OPTED TO
REDUCE MAX TEMPS ABOUT 2-4 DEGS F AREAWIDE SUN-TUE VERSUS PREVIOUS
FORECASTS THOUGH STILL NOT QUITE AS LOW AS MRF MOS GUIDANCE
INDICATES.  BF

.TWC...NONE.

AZZ019-029>035-251400-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1130 AM MST THU JUL 24 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...HIGH PRESSURE WILL REMAIN CENTERED NEAR THE FOUR CORNERS
REGION. SEVERAL WEAK DISTURBANCES ROTATING AROUND THE HIGH WILL MOVE
FROM CENTRAL NEW MEXICO INTO SOUTHEAST ARIZONA LATE THIS AFTERNOON
AND EARLY THIS EVENING. THIS IS EXPECTED TO ENHANCE THE DEVELOPMENT
OF SCATTERED LATE AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS
TODAY. WEATHER CONCERNS WILL BE THE POTENTIAL FOR A FEW OF THE
STORMS TO PRODUCE STRONG GUSTY WINDS...SMALL HAIL AND LOCALIZED
HEAVY RAINFALL...ESPECIALLY DURING THE EVENING HOURS.

.DISCUSSION...NO MAJOR CHANGES ON THE MORNING TUCSON UPPER AIR
SOUNDING...WITH ABUNDANT MOISTURE IN PLACE AND A PRECIPITABLE WATER
VALUE OF 1.30 INCHES. GOES TOTAL PRECIPITABLE WATER SATELLITE
IMAGERY INDICATES HIGHER VALUES FROM TUCSON WESTWARD...ALTHOUGH
RAOBS FROM AROUND THE REGION SHOW MORE THAN SUFFICIENT MOISTURE IN
PLACE OVER MUCH OF THE SOUTHWESTERN UNITED STATES. THE PROFILE WAS
ALSO MODERATELY UNSTABLE WITH LIFTED INDEX NEAR MINUS 4 AND AN
UNMODIFIED SURFACE-BASED CAPE VALUE OF 1488 J/KG. HOWEVER...THESE
VALUES WERE DOWN SLIGHTLY FROM YESTERDAYS SOUNDING WHICH SHOWED A
LIFTED INDEX OF NEAR MINUS 6 AND AN UNMODIFIED SURFACE-BASED CAPE
VALUE OF 2121 J/KG. SOUNDING ALSO SHOWS SOME COOLING IN THE LOWER
LAYERS AND WARMING AT THE MID LEVELS...WHICH SHOULD SLOW INITIAL
START OF THE THUNDERSTORM DEVELOPMENT TODAY.

NUMERICAL MODELS POINT TO SEVERAL INDICATORS THAT COULD BRING AN
UPSWING IN ACTIVITY TODAY. PEAK THUNDERSTORM ACTIVITY IS EXPECTED TO
BE BETWEEN 4 PM AND 10 PM MST THIS EVENING. SIGNIFICANT ORGANIZED
CONVECTION WILL ALSO BE A POSSIBILITY THIS EVENING AS SEVERAL
FACTORS COME TOGETHER ACROSS NORTHERN SONORA AND SOUTHERN ARIZONA.
300 MB RIDGE AXIS IS EXPECTED TO SHIFT WESTWARD OVER THE REGION
TODAY. IN ADDITION...SEVERAL WEAK DISTURBANCES OVER NEW MEXICO WILL
ROTATE AROUND THE UPPER HIGH AND INTO ARIZONA LATE THIS AFTERNOON
AND EARLY THIS EVENING...BRINGING SOME DYNAMICS/LIFT INTO PLAY.
ANOTHER POSITIVE FACTOR WILL BE THE ANTICIPATED LATE START...WHICH
WILL ALLOW STORM DEVELOPMENT TO COINCIDE WITH MAXIMUM DAYTIME
HEATING AND DURING TIME OF MAXIMUM INSTABILITY.

STORM MOTION WILL BE TO THE WEST TO NORTHWEST AT 15 MPH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH THURSDAY.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

SUFFICIENT MOISTURE WILL BE IN PLACE FOR AT LEAST A STANDARD
SUMMERTIME THUNDERSTORM SEASON FORECAST WITH SCATTERED MAINLY
AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. HOWEVER...THE
MODELS ARE INDICATING THAT AN EASTERLY WAVE IS EXPECTED TO DEVELOP
OVER THE WESTERN GULF COAST ON FRIDAY AND THEN MOVE NORTHWEST INTO
THE DESERT SOUTHWEST ON SUNDAY. IF THIS OCCURS...WE MAY SEE AN
UPSWING IN SHOWER AND THUNDERSTORM ACTIVITY ON SUNDAY AND MONDAY AS
THIS SYSTEM MOVES ACROSS THE REGION.

.SPOTTER INFORMATION STATEMENT...

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