Severe Thunderstorm Warning 26, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
210 PM MST FRI AUG 3 2001

.SYNOPSIS...A STRONG RIDGE OF HIGH PRESSURE WILL EXPAND WEST FROM
KANSAS INTO NORTHERN ARIZONA THROUGH EARLY NEXT WEEK. THIS WILL
BRING A SERIES OF DISTURBANCES WEST ACROSS MEXICO AND MAINTAIN A
FAIRLY HIGH THREAT OF THUNDERSTORMS THROUGH THE FIRST PART OF NEXT
WEEK. DUE TO THE CLOSE PROXIMITY OF THE HIGH...TEMPERATURES WILL
AVERAGE SEVERAL DEGREES ABOVE NORMAL.

.DISCUSSION...THINGS GOING PRETTY MUCH AS PLANNED SO FAR WITH
MOUNTAIN TSTMS VALIANTLY FIGHTING AGAINST THE MID LEVEL CAP. THE
PROBLEM IS THAT THE STORMS ARE TRYING TO BREAK THROUGH, AND WE STILL
HAVE A FEW MORE HOURS OF HEATING. 18Z ETA HAS ALSO BECOME MORE
EMPHATIC ABOUT INCREASING DIVERGENCE AND WEAK STATIC STABILITY IN
THE 300-200MB LAYER. WE'LL GO FOR SCATTERED POPS IN MOST AREAS, BUT
WE'LL WAIT UNTIL THE LAST MINUTE TO SEE IF WE NEED TO BUMP POPS UP
HIGHER OR TO INSERT HEIGHTENED WORDING. AS MENTIONED IN THE
HAZARDOUS WEATHER OUTLOOK, THE DRIER MID LEVELS AND SLIGHTLY FASTER
STEERING FLOW HAS INCREASED THE THREAT OF DAMAGING WINDS THIS
EVENING AND REDUCED THE THREAT OF FLASH FLOODING (ONLY BY A LITTLE,
THOUGH). ON THE OUTSIDE CHANCE THAT THE ETA IS RIGHT AND WE GET 2-3C
OF COOLING ALOFT BETWEEN 00Z AND 03Z, WE COULD BE IN FOR A LONG
EVENING.

WITH UPPER RIDGE EXTENDING FROM S SONORA INTO TX, FLOW WILL
TEMPORARILY GO LIGHT AS THE RIDGE PIVOTS INTO AN W-E CONFIGURATION
FROM AZ INTO THE GULF COAST STATES BY SAT NIGHT. I WAS GOING TO BACK
THINGS OFF BOTH PERIODS 2 AND 3, BUT THE EASTERLY WAVE NEARING
KCRP/KBRO IS BOOKING W AT 25KTS. THAT WOULD PUT IT INTO SONORA BY
SAT EVENING. NONE OF THE MODELS ARE HANDLING IT VERY WELL, BUT THE
MESOETA IS HANDLING THE INCREASINGLY DIFFLUENT FLOW UNDERNEATH THE
UPPER RIDGE, AS IS INCREASING OUR 700-500MB FLOW TO 25KTS. AFTER
ANOTHER DOWNSLOPED AND RATHER HOT DAY SAT, AN EASTERLY WAVE MARCHING
INTO THE NEIGHBORHOOD COULD BE TROUBLE, DEPENDING AS USUAL ON EXACT
TIMING. WE'LL LOWER POPS ON SAT, BUT RAISE THEM SAT NIGHT/SUN. AS
MENTIONED EARLIER, THE DAY 3-7 SITUATION LOOKS QUITE ACTIVE WITH THE
UPPER RIDGE PARKED TO OUR N AND OUR PERSISTENT UPPER TROUGH
RETREATING INTO THE GULF OF AK. THE ONLY PROBLEM I SEE IS THAT OUR
FLOW WILL BE PERSISTENTLY OUT OF THE E, WHICH IS NOT ONLY DOWNSLOPE,
BUT ALSO OFF HOT/BONE-DRY AREAS OF THE SOUTHERN PLAINS. THEN AGAIN,
THE DESERTS WILL BE HOT OVER THE NEXT SEVERAL DAYS AS WELL, SO ANY
STORMS THAT CAN FIRE WILL GET NASTY PRETTY QUICKLY AND WILL HAVE AT
LEAST SOME ORGANIZATION. WE'LL STICK TO MID-GRADE WORDING PER GOING
FORECAST, BUT WE'LL NUDGE TEMPS UP A NOTCH DUE TO THE DOWNSLOPING
AND PROXIMITY OF THE UPPER RIDGE. PYTLAK

.TWC...NONE.

AZZ019-029>035-040700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1152 PM MST FRI AUG 3 2001

.SYNOPSIS...AN UPPER LEVEL HIGH HAS BEGUN TO EXPAND WEST TOWARD
ARIZONA. DRIER AIR IS COMING INTO THE REGION WITH THIS HIGH...BUT
LOW LEVEL MOISTURE REMAINS IN PLACE. A WEAK DISTURBANCE OVER EASTERN
NEW MEXICO IS MOVING WEST AND WILL ARRIVE IN EASTERN ARIZONA BY
EARLY THIS EVENING. THIS MAY HELP TO OVERCOME THE WARMING
TEMPERATURES ALOFT AND LEAD TO STRONG THUNDERSTORMS.

.DISCUSSION...THIS IS VERY MUCH A CONDITIONAL DAY OVER SOUTHEAST
ARIZONA. SUBSIDENCE HAS CAUSED NOTICEABLE WARMING AND DRYING IN THE
UPPER LEVELS OF THE ATMOSPHERE. THIS WILL INITIALLY CONFINE
THUNDERSTORM DEVELOPMENT TO THE MOUNTAINS AND ALLOW PLENTY OF
DAYTIME HEATING TO TAKE PLACE IN THE VALLEYS. SOUTHEAST WINDS OF 10
TO 20 MPH ARE ALSO DOWNSLOPING INTO THE REGION AND WILL FURTHER WARM
THE VALLEYS.

BY MID AFTERNOON...STRONGER STORMS ARE EXPECTED TO DEVELOP FIRST
OVER THE WESTERN DESERTS WHERE MID LEVEL TEMPERATURES ARE NOT AS
WARM AND INITIAL CLOUD DEVELOPMENT THIS MORNING HAS BEEN A LITTLE
DEEPER. BY LATE AFTERNOON...ATTENTION WILL SHIFT TO THE EAST WHERE
THE DISTURBANCE MOVING OUT OF NEW MEXICO MAY CAUSE THE MID LEVEL
TEMPERATURE INVERSION TO BREAK. IF THIS OCCURS...THE STORMS WILL
DEVELOP RAPIDLY...BECOME SOMEWHAT ORGANIZED...AND BECOME QUITE
STRONG AS THEY MOVE INTO THE VALLEYS. THE WIND FLOW ALOFT WILL ALSO
TEND TO SUSTAIN ANY STORMS THAT DEVELOP WELL INTO THE EVENING HOURS.

IN CONTRAST TO YESTERDAY...THE DRYING TAKING PLACE ALOFT AND
INCREASED SOUTHEAST FLOW HAS INCREASED THE RISK OF SEVERE
THUNDERSTORMS ABOVE CLIMATOLOGY. DAMAGING DOWNBURST WINDS ARE THE
MAIN THREAT SINCE UPPER LEVEL TEMPERATURES ARE TOO WARM TO SUPPORT
MUCH IN THE WAY OF HAIL. THE SAME CONDITIONS HAVE REDUCED THE THREAT
OF FLASH FLOODING...BUT BECAUSE LOW LEVEL MOISTURE REMAINS QUITE
HIGH...THE RISK OF FLASH FLOODING IS ONLY REDUCED TO NEAR
CLIMATOLOGICAL VALUES.

STORM MOVEMENT WILL BE NORTHWEST AT 15 TO 20 MPH.

PYTLAK