Flash Flood Warning 20, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
230 PM MST SUN JUL 19 1998

SYNOPSIS...SURGE OF MOISTURE FROM THE GULF OF CALIFORNIA COMBINED
WITH AN UPPER LEVEL IMPULSE WILL LEAD TO INCREASED THUNDERSTORM
ACTIVITY ACROSS SOUTHEAST ARIZONA.

DISCUSSION...HIGH REMAINS CENTERED NEAR THE UT/AZ BORDER...SHIFTING
SLOWLY EASTWARD OVER THE NEXT 48 HRS. UPPER LEVEL IMPULSE SPINNING
UNDER IT IN EASTERLY INTO SOUTHEAST AZ WILL CONTINUE TO SHIFT SLOWLY
WESTWARD. STRONG SURGE SIGNAL EVIDENT IN YUMA OVERNIGHT SPREADING
INTO THE LOWER DESERTS CIRCULATING INTO THE WESTERN 2/3RDS OF OUR
AREA. LOTS OF SUNSHINE...VERY UNSTABLE OUTSIDE OF SUBSIDENCE
IMMEDIATELY AHEAD OF IMPULSE. EVERYTHING POINTS TOWARDS A
SIGNIFICANT THUNDERSTORM AFTERNOON AND EVENING WITH CONSIDERATION
FOR SEVERE AS WELL AS LOCALLY HEAVY RAINFALL. UPPER LEVEL DYNAMICS
MAY ASSIST STORM DEVELOPMENT / REDEVELOPMENT OVERNIGHT.

IF OVERNIGHT ACTIVITY TURNS OUT TO BE AS HEAVY AS PREDICTED...DEBRIS
CLOUD AND SOME STABILITY IN THE LOWER ATMOSPHERE COULD HELP DEPRESS
WIDESPREAD ACTIVITY TOMORROW. WILL TAYLOR THE FORECAST IN THAT
DIRECTION...BUT NOT COMPLETELY. OTHERWISE OVERALL GOOD THUNDERSTORM
CONDITIONS WILzL PERSIST INTO THE EXTENDED. TUS 6333. MEYER

.TWC...NONE.

AZZ019-029>035-200700-
SPECIAL WEATHER STATEMENT...SOUTHEAST ARIZONA CONVECTIVE OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1245 PM MST SUN JUL 19 1998...THIS PRODUCT IS NOT UPDATED

                        *CONDITIONAL*    *CONDITIONAL*
                AREAL    PROBABILITY   RAIN GREATER THAN   STORM
              COVERAGE    OF SEVERE     1.00       2.00    MOTION

COCHISE          50          30          45          5      W 12
GRAHAM           50          25          45          5      W 12
GREENLEE         60          15          45          5      W 12
TUCSON/ERN PIMA  55          30          55         10      W 10
TOHONO O'ODHAM   55          30          60         15      W 10
WESTERN PIMA     45          15          50         10      W 10
SOUTHEAST PINAL  55          30          60         15      W 10
SANTA CRUZ       60          25          60         15      W 10

SYNOPSIS...GULF SURGE ALONG WITH AN EASTERLY UPPER LEVEL DISTURBANCE
AND PLENTY OF HEATING SHOULD COMBINE FOR A STRONG THUNDERSTORM
AFTERNOON AND NIGHT. SCATTERED TO LIKELY THUNDERSTORMS WITH MODERATE
RISK FOR SEVERE AND LOCALLY HEAVY RAINFALL. SOME DELAYED DEVELOPMENT
MAY OCCUR FROM EAST TO WEST AS THE UPPER LEVEL DISTURBANCE MOVES IN
FROM NEW MEXICO. STORMS WILL LIKELY BE SUSTAINED AND/OR REGENERATE
INTO THE EARLY MORNING HOURS. THE NEXT 14 HOURS WILL BE BUSY.

*****************************************************************
KEY...
AREAL COVERAGE - PERCENT OF COUNTY OR AREA THAT WILL EXPERIENCE
                  THUNDERSTORMS
PROB OF SEVERE - THE PROBABILITY THAT ANY ONE OF THE STORMS WILL
                  REACH SEVERE LEVELS (DAMAGING WIND AND/OR
                  LARGE HAIL)
RAIN GRTR THAN - THE PROBABILITY THAT ANY ONE OF THE STORMS WILL
                  PRODUCE RAIN EXCEEDING 1 INCH OR 2 INCHES IN
                  ANY LOCATION
STORM MOTION   - GENERAL DIRECTION TO WHICH THE STORMS WILL
                  LIKELY MOVE AND SPEED IN MPH

NOTE...
VALID TIME IS FROM 12:45 PM TO 12 MIDNIGHT OF THE DAY OF ISSUANCE.
THIS PRODUCT IS NOT TO BE USED IN PLACE OF SEVERE THUNDERSTORM OR
FLASH FLOOD WARNINGS OR WATCHES. THIS PRODUCT IS ONLY USED FOR
OUTLOOK PURPOSES. CORRESPONDING GRAPHICS MAY BE FOUND ON THE NWS
TUCSON INTERNET PAGE AT
HTTP://NIMBO.WRH.NOAA.GOV/TUCSON/SWO/SWO.SHTML

END/MEYER