Severe Thunderstorm Warning 18, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
225 PM MST THU JUL 15 2004

SOUTHEAST ARIZONA FORECAST DISCUSSION

.SYNOPSIS...HIGH PRESSURE ALOFT CENTERED OVER COLORADO WILL KEEP A
MOIST EAST TO SOUTHEAST FLOW INTO ARIZONA THIS WEEK. THE RISK OF
THUNDERSTORMS SHOULD DECREASE SOMEWHAT OVER THE WEEKEND AS THE UPPER
HIGH MOVES SOUTH AND CUTS OFF SOME OF THE MOISTURE SUPPLY.
&&

.DISCUSSION...REGIONAL SOUNDINGS THIS MORNING SHOWED THAT IT WAS
STILL VERY MOIST ACROSS MOST OF ARIZONA...BUT DRYING HAD TAKEN
PLACE IN NEW MEXICO AND HAS BEEN SPREADING WEST ACROSS SOUTHEAST
ARIZONA. THIS IS ALSO SEEN ON THE GOES PRECIPITABLE WATER IMAGERY
WITH VALUES RANGING FROM 1.50 TO 2 WEST OF TUCSON AND LESS THEN
1.25 FROM TUCSON EAST...WITH VALUES BELOW 1 IN THE WHITES. EVEN
THOUGH WE ARE STARTING OFF RATHER SLOW THIS AFTERNOON...WITH
CONVECTION OVER THE EASTERN MOUNTAINS AS OF 2 PM...SHOULD SEE A MORE
ACTIVE EVENING THAN LAST NIGHT AS THE AREA HAS HAD VERY GOOD HEATING
TODAY.  HOWEVER THE AREA WILL HAVE TO RELY ON OUTFLOW INTERACTIONS
AND ALSO A TRIGGER ALOGT TO GET SOME ORGANIZED STORMS GOING. WE
CURRENTLY HAVE ONE MOVING TOWARD SOUTHEAST ARIZONA. AS OF 2
PM...THIS FEATURE WAS JUST WEST OF EL PASO WITH ISOLATED TO WIDELY
SCATTERED THUNDERSTORMS DEVELOPING ACROSS SOUTHWEST NEW MEXICO. THE
DRIER AIR HAS MIX DOWN TO THE SURFACE EAST OF TUCSON WHERE DEWPOINTS
HAVE FALLEN DOWN INTO THE LOW TO MID 50S...WHILE THEY ARE HANGING IN
THE LOWER 60S ACROSS EASTERN PIMA/PINAL/SANTA CRUZ COUNTIES.
MODIFIED TUCSON SOUNDING FOR AFTERNOON CONDITIONS GAVE A MLCAPE OF
1400 J/KG. SO PLENTY UNSTABLE OUT THERE BUT AGAIN NEED SOME TRIGGERS
TO WORK TOGETHER TO GET THE STORMS GOING. WITH THE DRIER AIR IN
PLACE FROM TUCSON EAST AND A MOIST ATMOSPHERE WEST...WE HAVE TWO
CONCERNS TO DEAL WITH TONIGHT. A BETTER SEVERE T-STORM THREAT FROM
TUCSON EAST...WITH LOCALIZED HEAVY RAINERS...AND MOSTLY A HEAVY RAIN
EVENT IN CENTRAL AND WESTERN PIMA COUNTY IF STORMS TO PROPAGATE OUT
THERE. THERE HAVE BEEN SOME HEALTHLY STORMS IN SOUTHWEST NEW MEXICO
WHERE A COUPLE WARNINGS HAVE BEEN ISSUED BY WFO EL PASO.

THE REMAINDER OF THE FORECAST CYCLE WILL SHOW A DECREASE IN
AFTERNOON AND EVENING THUNDERSTORM ACTIVITY AND WARMER DAY TIME
TEMPERATURES. THIS DUE TO THE RIDGE OF HIGH PRESSURE SETTING IN OVER
EASTERN ARIZONA WITH RIDGE AXIS ALONG THE STATE LINE. THIS WILL CUT
OFF ANY INVERTED TROFS FROM ENTER THE PICTURE AND TURN FLOW ALOFT TO
THE SOUTH. LOOKS LIKE LOW GRADE MONSOON FORECAST. I HAVE UPPED HIGH
TEMPERATURES OVER THE WEEKEND DUE TO THE LOCATION OF THE RIDGE..BUT
MAY NOT BE WARM ENOUGH IN SPOTS. DONT BE SURPRISED IF TUCSON HITS
105 OR 106 THIS WEEKEND.
&&

.FIRE WEATHER...WITH HUMIDITY LEVELS UP FOR THE THUNDERSTORM
SEASON...THE MAIN CONCERN WILL BE GUSTY WINDS FROM NEARBY SHOWERS
AND THUNDERSTORMS THE NEXT SEVERAL DAYS. A FEW OF THE BURN SITES
FROM LAST YEAR AND THIS FIRE SEASON WILL CONTINUED TO BE WATCHED
CLOSELY FOR HEAVY RAINFALL.
&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

JRG

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1156 AM MST THU JUL 15 2004

AZZ019-029>035-160700-
NORTHERN GREENLEE COUNTY-UPPER GILA RIVER VALLEY-COCHISE COUNTY-
SOUTHEAST PINAL COUNTY-TUCSON METRO/MARANA/GREEN VALLEY-
SANTA CRUZ COUNTY-TOHONO OODHAM NATION-WESTERN PIMA COUNTY-
1156 AM MST THU JUL 15 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...THERE IS A HIGHER RISK OF SEVERE DOWNBURST WINDS WITH
LOCALIZED HEAVY RAIN TO THE EAST OF TUCSON TODAY...WITH AN HIGHER
RISK OF MORE WIDESPREAD VERY HEAVY RAINFALL WEST OF TUCSON.

DISCUSSION...A WEAK UPPER LEVEL DISTURBANCE...WHICH ORIGINATED FROM
SOUTHERN OKLAHOMA LAST NIGHT...WILL CONTINUE TO ROTATE EAST THROUGH
SOUTH CENTRAL NEW MEXICO ALONG THE BASE OF THE UPPER RIDGE TODAY...
AND EVENTUALLY WILL PUSH INTO THE FAR SOUTHEAST CORNER OF ARIZONA
LATER THIS AFTERNOON. THIS DISTURBANCE WILL ACT AS A TRIGGERING
MECHANISM FOR THUNDERSTORM INITIATION THIS AFTERNOON. IN ADDITION...
BOTH THE MID AND UPPER LEVEL HIGH CENTERS LOCATED OVER COLORADO THIS
MORNING WILL SHIFT SOUTHEAST TOWARDS THE TEXAS PANHANDLE. THIS WILL
ALLOW THE FLOW ALOFT TO BECOME DIFFLUENT...THUS ALSO AIDING
CONVECTIVE INITIATION. THIS DIFFLUENT AREA WILL PUSH INTO THE FAR
SOUTHEAST CORNER OF ARIZONA BY LATE THIS AFTERNOON...AND THEN WILL
SHIFT NORTHWEST INTO CENTRAL ARIZONA BY LATE THIS EVENING.

THE GOES-10 PRECIPITABLE WATER IMAGERY AND SURFACE OBSERVATIONS
INDICATED THAT LOCATIONS WEST OF TUCSON REMAIN VERY MOIST IN THE LOW
LEVELS...WITH AREAS EAST OF TUCSON BEGINNING TO SEE SOME DRYING
COMING IN FROM THE EAST. GIVEN THIS...THERE IS A HIGHER RISK OF
SEVERE DOWNBURST WINDS WITH LOCALIZED VERY HEAVY RAIN TO THE EAST OF
TUCSON TODAY...WITH AN HIGHER RISK OF MORE WIDESPREAD VERY HEAVY
RAINFALL WEST OF TUCSON. THUNDERSTORM ACTIVITY WILL BEGIN LATER THIS
AFTERNOON IN THE EASTERN MOUNTAINS...PUSH INTO THE VALLEYS BY LATE
AFTERNOON AND THEN PUSH WEST INTO THE LOWER DESERTS BY EARLY THIS
EVENING. STORM MOTION WILL BE TO THE WEST NORTHWEST AT 15 MPH TODAY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

THUNDERSTORM ACTIVITY ACROSS SOUTHEAST ARIZONA WILL SLOWLY DECREASE
THIS WEEKEND AND EARLY NEXT WEEK AS THE UPPER HIGH CENTER MOVES
FURTHER SOUTH...CUTTING OFF THE MOISTURE SUPPLY FROM THE SOUTH AND
SOUTHEAST. HOWEVER...ENOUGH MOISTURE WILL STILL REMAIN IN PLACE FOR
ISOLATED TO SCATTERED THUNDERSTORMS.

.SPOTTER INFORMATION STATEMENT...

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