Severe Thunderstorm Warning 15, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
220 PM MST THU JUL 11 2002

.SYNOPSIS...STRONG HIGH PRESSURE OVER UTAH WILL KEEP DEEP EASTERLY
FLOW OVER THE REGION FOR THE REST OF THE WEEK. THIS WILL STEER A
SERIES OF DISTURBANCES OFF THE GULF OF MEXICO AND SOUTHERN PLAINS...
LEADING TO A DAILY RISK OF THUNDERSTORMS THROUGH EARLY NEXT
WEEK.

.DISCUSSION...ELEVATED TSTMS HAVE MANAGED TO FIRE ON THE BOUNDARY
BETWEEN THE DEEPER MOISTURE OVER THE W CWA AND THE DRIER AIR OVER
THE E. FURTHER E, THINGS ARE EVOLVING PRETTY MUCH AS EXPECTED WITH
REMNANT CONVECTIVE VORT HELPING TO GET THINGS GOING IN THE WHITES/
GILAS, AND THE APPROACHING EASTERLY WAVE OVER THE BIG BEND HELPING
TO INCREASE THE E FLOW ALONG THE NM/AZ BORDER. DEWPOINTS ARE STILL
LOWER THAN WED LIKE TO SEE, BUT AT LEAST THEYVE STABILIZED AS WE
TAP INTO SLIGHTLY HIGHER PRECIP WATERS OVER W TX/N CHIHUAHUA.
BECAUSE OF THE BELOW-CLIMO PRECIP WATERS AND DEWPOINTS WE HAVE IN
PLACE, HAVE DECIDED TO LOWER POPS A BIT TONIGHT WHILE STILL
INCLUDING SOME GUSTY WIND/BLOWING DUST WORDING. CELLS ARE ALREADY
PICKING UP SPEED AS THE LOW LEVEL FLOW INCREASES, SO HEAVY RAIN
THREAT IS MINIMAL EXCEPT MAYBE THE W DESERTS WHERE PRECIP WATERS ARE
A LITTLE HIGHER. INCREASE IN FLOW SHOULD ALSO HELP SUSTAIN A FEW
ELEVATED SHOWERS/TSMTS WILL INTO THE NIGHT, MOST LIKELY AGAIN OUT W.

WE HAVE AN INTERESTING WRINKLE DEVELOPING IN OUR OVERALL THINKING --
ONE WHICH WILL MAKE THINGS MORE COMPLICATED AS WE HEAD INTO THE
WEEKEND. BROAD UPPER LOW HAS NOW FORMED OVER THE SOUTHERN GULF OF CA
AND IS STARTING TO INGEST THE BIG BEND EASTERLY WAVE. THIS UPPER LOW
IS NOT PROGGED TO GO VERY FAR OVER THE NEXT 48-72HRS, WHICH MEANS S
AZ WILL EITHER END UP IN A RATHER FAVORABLE DIFFLUENT AREA BETWEEN
IT AND THE UPPER HIGH OVER THE NORTHERN ROCKIES, OR AN UNFAVORABLE
CONFLUENT AREA IF THE HIGH SHIFTS E INTO CO/WY. THE PRESENCE OF THE
LOW MAY ALSO GET A SURGE GOING, BUT UNTIL THAT HAPPENS, WERE GOING
TO CONTINUE TO BATTLE DOWNSLOPING E FLOW WHICH WILL TEND TO KEEP US
ON THE DRY SIDE OF CLIMO. THEREFORE WE SEE NO REASON TO GO ABOVE
STANDARD MID-GRADE POPS FOR THE NEXT 48HRS, KEEPING IN MIND WE MAY
HAVE TO UPSHIFT IF A SURGE GETS GOING EITHER FRI OR SAT NIGHT.
MODELS DONT SHOW MUCH CHANGE IN THE UPPER HIGH POSITION THROUGH
DAYS 6 OR 7, BUT IF THE BAJA UPPER LOW CAN PARK JUST W OF BAJA, OUR
MEAN FLOW WOULD SHIFT TO THE SE OR S AND SEND US INTO HIGH GRADE
MODE FOR A FEW DAYS. WERE NOT WILLING TO UP THE ANTE BEYOND A
STANDARD SCATTERED EAST/CHANCE WEST SCENARIO UNTIL WE GET A BETTER
IDEA ON WHERE EXACTLY THE UPPER LOW IS GOING TO SET UP. PYTLAK

.TWC...NONE.

AZZ019-029>035-120700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1207 PM MST THU JUL 11 2002

.SYNOPSIS...ALTHOUGH AMPLE LOW TO MID-LEVEL MOISTURE RESIDES WEST OF
LINE FROM PATAGONIA TO TUCSON TO KEARNY...DRY AIR AT LOW-LEVELS
CONTINUES TO BLANKET THE EASTERN VALLEYS. SOUTHEAST ARIZONA WILL
EXPERIENCE BELOW CLIMATOLOGICAL PROBABILITIES FOR PRECIPITATION IN
EXCESS OF ONE INCH WITH A HIGHER PROBABILITY FOR HEAVY PRECIPITATION
IN THE WESTERN DESERTS. THE PROBABILITY FOR SEVERE THUNDERSTORMS
WILL BE NEAR CLIMATOLOGY WITH HIGHER PROBABILITIES IN THE EASTERN
VALLEYS.

.DISCUSSION...SATELLITE IMAGERY CONTINUES TO INDICATE DEEP LOW-LEVEL
MOISTURE ACROSS CENTRAL AND WESTERN PIMA COUNTY TODAY WITH DRY AIR
RESIDING ACROSS THE EASTERN VALLEYS. WITH AMPLE MID-LEVEL MOISTURE
ACROSS ALL OF SOUTHEAST ARIZONA...THUNDERSTORMS WILL HAVE TO RELY ON
SOLAR HEATING TODAY TO DESTABILIZE THE ATMOSPHERE FOR THUNDERSTORM
DEVELOPMENT.

THUNDERSTORMS WILL BEGIN TO DEVELOP OVER THE MOUNTAINS EARLY TODAY
AND REMAIN CONFINED TO THE HIGHER TERRAIN DUE TO A LACK OF STRONG
MID-LEVEL WINDS TO PUSH THEM OVER THE VALLEYS. IN ADDITION...WITH
STRONGER WINDS ABOVE THESE WEAK MID-LEVEL WINDS...THE RESULTING
SHEAR WILL TILT THUNDERSTORM UPDRAFTS...INHIBITING DEEP CONVECTION
UNTIL LATE THIS AFTERNOON. SINCE THE FLOW INCREASES THROUGHOUT THE
AFTERNOON AND INTO THE EVENING...THE SHEAR DECREASES ALLOWING DEEPER
CONVECTION TO OCCUR...AND MORE IMPORTANTLY WILL ALLOW THESE STORMS
TO PUSH INTO THE VALLEYS.

ALTHOUGH THESE STORMS WILL HAVE DIFFICULTY SUSTAINING THEMSELVES
OVER THE VALLEYS WITH DRY AIR AT LOW LEVELS...THIS DOES INCREASES
THE POTENTIAL FOR THESE STORMS TO PRODUCING STRONG...GUSTY AND
ERRATIC THUNDERSTORM WINDS. THE RISK OF A SEVERE THUNDERSTORM WILL
BE NEAR CLIMATOLOGY TODAY ACROSS MOST OF THE AREA WITH SLIGHTLY
ABOVE CLIMATOLOGICAL PROBABILITIES IN THE EASTERN VALLEYS WHERE
LOW-LEVEL DRY AIR RESIDES.

THUNDERSTORM MOTION WILL BE INITIALLY BE TOWARDS THE WEST EARLY THIS
AFTERNOON AT 5 MPH...THEN INCREASING TO 15 MPH BY THE AFTERNOON.

THOSE THUNDERSTORMS THAT PUSH INTO CENTRAL AND WESTERN PIMA COUNTY
WILL BE CAPABLE OF PRODUCING HEAVIER RAINFALL AMOUNTS DUE TO AMPLE
MOISTURE. THEREFORE...THE RISK OF RECEIVING PRECIPITATION IN EXCESS
OF ONE INCH IS GREATER IN THE WEST TODAY. THE REGION WILL SEE BELOW
CLIMATOLOGICAL ONE INCH PROBABILITIES FOR MOST OF THE AREA WITH
PROBABILITIES ABOVE CLIMATOLOGY IN THE FAR WESTERN DESERTS.