Severe Thunderstorm Warning 7, NWS Tucson, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
203 PM MST TUE JUL 13 2004

SOUTHEAST ARIZONA FORECAST DISCUSSION

.SYNOPSIS...HIGH PRESSURE ALOFT CENTERED OVER COLORADO WILL KEEP A
MOIST EAST TO SOUTHEAST FLOW INTO ARIZONA THROUGH FRIDAY. AN UPPER
LEVEL DISTURBANCE APPROACHING THE AREA FROM THE SOUTHEAST WILL SERVE
TO FURTHER INCREASE THE COVERAGE AND INTENSITY AS IT TAPS INTO
MOISTURE FROM TROPICAL STORM BLAS SOUTHWEST OF THE SOUTHERN TIP OF
BAJA. THE RISK OF THUNDERSTORMS MAY DIMINISH SOMEWHAT BY THE WEEKEND
AS THE UPPER HIGH SHIFTS TO THE NEW MEXICO ARIZONA BORDER AND CLOSES
OFF SOME OF THE MOISTURE SUPPLY FROM THE SOUTH AND EAST.

&&

.DISCUSSION...18Z SOUNDING SHOWED A CONTINUATION OF THE WEAK
850-500MB SHEAR WEVE HAD THE PAST SEVERAL DAYS. IT ALSO SHOWED A
WEAK CAP IN THE 800-700MB LAYER (CIN AROUND 50 J/KG). HOWEVER
PLUGGING IN A TEMP OF 98F AND A DEWPOINT OF 60F WE GET A CAP RUPTURE
AND A MODIFIED MLCAPE NEAR 1500 J/KG. A COUPLE OF TSTMS HAVE
RECENTLY RUPTURED THIS CAP OVER THE SANTA RITA AND RINCONS S AND E
OF KTUS. GENERAL IDEA IS THAT TSTMS WILL BE STRONGER AND LONGER
LASTING THIS AFTERNOON/EVENING, BUT THE STRONGER COLD POOLS WILL
AGAIN OUTRUN THE TSTMS AND KEEP THEM ORGANIZING INTO ANYTHING MORE
THAN LOOSE CLUSTERS. THE ONE EXCEPTION MAYBE ALONG THE FRONTERA FROM
KOLS TO ORGAN PIPE WHERE PRECIP WATER AND MID LEVEL SHEAR ARE A BIT
HIGHER. WELL ADD HEIGHTENED WORDING TO MOST ZONES THIS EVENING, BUT
STOP SHORT OF SEVERE WORDING OR ISSUING AN FFA. HAVE ALSO NUDGED
POPS UP, BUT ONLY SLIGHTLY. WELL OBVIOUSLY KEEP A CLOSE EYE ON BURN
AREAS BUT THE HEAVY RAINFALL COVERAGE WILL NOT BE PARTICULARLY GREAT
WITH THE LOOSE CONVECTIVE ORGANIZATION.

THE POTENTIAL IS DEFINITELY THERE FOR FLASH FLOODING ON WED AS
PRECIP WATERS CLIMB EVEN FURTHER AND ANOTHER GULF SURGE GETS
UNDERWAY (OR MORE LIKELY, SIMPLY REINFORCES THE ONE THAT HAS BEEN
UNDERWAY SINCE LATE LAST NIGHT). BASED ON STUDIES LEADING UP TO
NAME, MAJOR SURGES LIKE THE ONE WE HAVE NOW USUALLY LEAD TO
CONVECTIVE OUTBREAKS THE DAY AFTER THE SURGE COMMENCES AND NOT THE
DAY IT STARTS. HOWEVER IT IS ALSO TYPICAL WHEN WE GET UP OVER 1.5
PRECIP WATER THAT DEBRIS CLOUDS AND COOLER DAYTIME HIGHS HOLD
INSTABILITY IN CHECK. 850-500MB SHEAR WILL ALSO REMAIN RATHER WEAK,
SO TSTMS MAY OCCASIONALLY TRAIN BUT WILL MAY NOT BE ABLE TO
CONSOLIDATE INTO AN MCS DESPITE INCREASED UPPER DIVERGENCE. THIS
WILL ALL HAVE TO BE MONITORED FOR LATER WATCH DECISIONS, BUT GIVEN
ALL OF THE FACTORS MENTIONED, WELL START TO INCLUDE THE POTENTIAL
FOR HEAVY RAIN ON WED/WED EVENING WHILE CONTINUING THE MID-HIGH
GRADE POPS WE ALREADY HAVE OUT.

MONSOON PATTERN CONTINUES RIGHT THROUGH DAY 7, ALTHOUGH MOST MEDIUM
RANGE MODELS SHOW THE UPPER HIGH SHIFTING FROM CO TO THE NM/AZ
BORDER. IF IT GETS TOO CLOSE WE WILL GET PRETTY WARM ALOFT, WEAKEN
THE ALREADY WEAK FLOW AND CAUSE TSTMS TO REMAIN TIED PRIMARILY TO
THE MOUNTAINS. IT WILL BE INTERESTING TO SEE HOW THE NEXT UPPER LOW
SPINNING UP OVER THE EASTERN GULF OF MEXICO TRACKS. THIS COULD LEAD
TO AN UPSWING PRETTY CLOSE, BUT TRACK WILL BE CRITICAL. WELL CARRY
CLIMO POPS AFTER DAY 4.

A NAME IOP REMAINS UNDERWAY THROUGH AT LEAST 00Z THU.

&&

.FIRE WEATHER...HUMIDITIES CONTINUE TO IMPROVE WITH WINDS REMAINING
ON THE LIGHT SIDE EXCEPT NEAR TSTMS. THE MAIN ISSUE IS NOW STARTING
TO INVOLVE BURN AREA FLASH FLOOD POTENTIAL WHICH WILL CONTINUE TO BE
MONITORED CLOSELY.

&&

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

PYTLAK

HAZARDOUS WEATHER OUTLOOK...CORRECTION
NATIONAL WEATHER SERVICE TUCSON AZ
1215 PM MST TUE JUL 13 2004

CORRECTION TO ADD STORM MOVEMENT FOR TODAY

AZZ019-029>035-140700-
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-
1215 PM MST TUE JUL 13 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST ARIZONA

.DAY ONE...TODAY

SYNOPSIS...LOW LEVEL MOISTURE HAS INCREASED OVER THE LOW DESERTS OF
ARIZONA THANKS TO AN THUNDERSTORM OUTFLOW INDUCED GULF SURGE.
ADDITIONALLY...AN UPPER LEVEL DISTURBANCE WILL MOVE ACROSS NORTHERN
SONORA THIS AFTERNOON AND TONIGHT. WITH A MOIST AND UNSTABLE
ATMOSPHERE IN PLACE...THE RISK OF BOTH SEVERE THUNDERSTORMS AND
FLASH FLOODING HAS INCREASED ACROSS THE AREA.

DISCUSSION...A THUNDERSTORM OUTFLOW INDUCED GULF SURGE HAS SPREAD
ABUNDANT AMOUNT OF LOW LEVEL MOISTURE INTO THE LOWER DESERTS OF
SOUTHWEST ARIZONA WHERE DEWPOINTS ARE IN THE MID 70S. DEWPOINT
VALUES ACROSS SOUTHEAST ARIZONA RANGED FROM THE 50S EAST OF TUCSON
TO THE 60S FROM TUCSON WEST. THE MOIST ATMOSPHERE IS SHOWN ON THE
18Z/11AM TUCSON SOUNDING WITH A PRECIPITABLE WATER VALUE OF 1.38.
ADDITIONALLY...THE SOUNDING SHOWED THAT THE MID-LEVEL WINDS HAVE
INCREASED...THUS INCREASING THE MID-LEVEL WIND SHEAR. ONE MORE
INGREDIENT TO THROW INTO THE MIX IS AN UPPER LEVEL DISTURBANCE THAT
WILL MOVE ACROSS NORTHERN SONORA THIS AFTERNOON AND TONIGHT. ALL OF
THIS ADDS UP TO A POTENTIALLY BIG DAY...WITH THE RISK OF DAMAGING
WINDS...LARGE HAIL AND FLASH FLOODING ALL ABOVE CLIMATOLOGY ACROSS
MOST OF SOUTHEAST ARIZONA. A FLASH FLOOD WATCH MAY BE ISSUED LATER
TODAY DUE TO THE MOIST AND UNSTABLE ATMOSPHERE. MOVEMENT OF THE
STORMS WILL BE TO THE WEST AROUND 10 TO 15 MPH.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

A SIGNIFICANT GULF SURGE WILL LIKELY OCCUR ON WEDNESDAY AS TROPICAL
STORM BLAS INCREASES THE WIND FLOW UP THE GULF OF CALIFORNIA.
DEPENDING ON WHAT HAPPENS TONIGHT...WEDNESDAY COULD ALSO BE A BIG
DAY. HOWEVER THERE IS A CHANCE THAT CONSIDERABLE CLOUD COVER MAY BE
AROUND ON WEDNESDAY...THUS HOLDING DOWN THE AMOUNT OF INSTABILITY
AND THUS REDUCING THE THREAT OF SEVERE THUNDERSTORMS AND FLASH
FLOODING ON ANY GIVEN DAY. THE REMAINDER OF THE WEEK AND INTO THE
WEEKEND WILL SEE A SLIGHT DECREASE IN THUNDERSTORM ACTIVITY.

.SPOTTER INFORMATION STATEMENT...

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