Severe Thunderstorm Warning 33, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
206 PM MST MON AUG 6 2001

.SYNOPSIS...A STRONG UPPER LEVEL DISTURBANCE OVER THE SOUTHERN
PLAINS WILL MOVE INTO EASTERN ARIZONA BY TUESDAY EVENING. AFTER
ANOTHER HOT DAY ON TUESDAY...THIS DISTURBANCE IS EXPECTED TO SET OFF
A ROUND OF STRONG THUNDERSTORMS OVER THE MOUNTAINS TUESDAY AFTERNOON
WHICH SHOULD THEN ROLL ACROSS THE DESERTS AND VALLEYS TUESDAY
EVENING. THIS DISTURBANCE IS THEN EXPECTED TO STALL JUST TO THE
EAST...WHICH WILL KEEP A RATHER HIGH RISK OF SHOWERS AND STORMS IN
THE REGION FOR THE REMAINDER OF THE WEEK.

.DISCUSSION...DOWNSLOPING, WARMING MID LEVELS, AND FULL SUN ARE
DOING THEIR TRICK THIS AFTERNOON WITH TEMPS ROCKETING PAST 100F IN
THE DESERTS. BECAUSE ITS A LITTLE WARMER THAN EXPECTED, WE ARE
GETTING PERILOUSLY CLOSE TO BREAKING THE CAP, ESPECIALLY ALONG A
LEFTOVER SHEAR AXIS EXTENDING FROM SW PINAL COUNTY INTO SW COCHISE
COUNTY. IF WE GET ANY KIND OF DEVELOPMENT, IT WILL BE IN THIS
CORRIDOR, WITH CELLS PROPAGATING TO THE W DUE TOWARD THE DEEPER
MOISTURE. CURRENT POPS HANDLE THE SITUATION PRETTY WELL, ALTHOUGH A
TWEAK HERE AND THERE MAY BE IN ORDER BEFORE PRESS TIME. PER OUR
SEVERE WEATHER OUTLOOK, DRY MICROBURST POTENTIAL WILL BE RATHER HIGH
IF SOMETHING CAN GET INTO THE VALLEYS.

CONTINUING TO WATCH THE OMINOUS-LOOKING UPPER LOW NOW DROPPING WSW
INTO TX. THE SAME BROKEN RECORD IS CONTINUING ON THE 18Z RUNS, WITH
EVERYTHING SAYING SIGNIFICANT RIM SHOT INTO SE AND S CENTRAL AZ LATE
TUE/TUE NIGHT. THE BIG PLUS THAT SEEMS TO BE DEVELOPING FOR SUCH AN
EVENT IS OUR WARM DESERTS AND CONTINUED DOWNSLOPE FLOW ON TUE.
850-700MB THICKNESSES SUPPORT SLIGHTLY WARMER HIGHS THAN WE HAVE
GOING NOW, WHICH BASED ON TODAYS RAPID CLIMB WILL BE REACHABLE. THE
E MAY BE JUST A HAIR COOLER AS MID LEVEL TEMPS START TO COLLAPSE
AHEAD OF THE EASTERLY WAVE. EXTENSIVE CU FIELD ACROSS TX/SE NM SEEMS
TO MARK THE LEADING EDGE OF THIS COOLER AIR ALOFT. THE COOLING IS
PROGGED TO ARRIVE IN CONJUNCTION WITH THE RAPID INCREASE IN
DIVERGENCE ALOFT, WHICH MEANS A POTENTIALLY EXPLOSIVE SITUATION IN
THE VALLEYS ONCE OUTFLOWS START MOVING OFF THE RIM. THE ONE THING
THATS STARTING TO CONCERN ME IS THAT THE 18Z MESOETA DRIES US OUT
SO MUCH THAT CAPE IS PRACTICALLY NIL UNTIL 06Z, WITH PRECIP WATERS
REMAINING UNDER 1 THROUGH WED MORNING. THE WAVE SEEMS TO BE
BRINGING MOISTURE WITH IT, THOUGH, BASED ON PRECIP WATER IMAGERY.
THE OTHER CONCERN IS THAT RIM STORMS WILL FIRE EARLY, WITH THE
ANVILS THEN DRIFTING INTO THE VALLEYS TO CHOKE OFF VALLEY HEATING.
ON THE OTHER HAND, IF WE GET UP OVER 105F AGAIN WITH SO MUCH COOLING
ALOFT (3-5C IN THE 500-400MB LAYER), IT PROBABLY WONT MATTER. IF I
WERE TO GO WITH THE AVN, ID USE LIKELY POPS FOR ALMOST EVERYONE
TUE NIGHT, BUT FOR NOW WELL OPT FOR AN NGM/AVN COMPROMISE AND KEEP
THE HIGHEST POPS IMMEDIATELY DOWNSLOPE FROM THE RIM (ZONES 19/30).
SEVERE THREAT IS DEFINITELY THERE, ESPECIALLY IF THE AVN IS RIGHT AS
THE LINE MOVES SW AT 30-40KTS. ETA IS MUCH WEAKER (15KTS) BUT TAKES
STORMS DUE S OFF THE MOUNTAINS.

WITH THIS EASTERLY WAVE GETTING STUCK ALONG THE AZ BORDER BETWEEN
UPPER LEVEL HIGH CELLS TO THE E AND W, THE DAY 2-5 FORECAST IS
DICEY. AT THEY VERY LEAST, WELL BE COOLER WITH MORE CLOUDS. THE
QUESTION IS WILL THE WAVE HELP TO FIRE MORE STORMS ON THE RIM WED
AFTERNOON, OR WILL THE LIFT BE SO STRONG WE END UP WITH SHOWERS AND
JUST A FEW RUMBLES OF THUNDER. THE SAME PROBLEMS CROP UP THU/FRI
WITH THE WAVE EVOLVING INTO MORE OF A TROUGH LINE, AND WITH THE
LIKELIHOOD OF A SURGE REINFORCING THE WESTERN DESERTS SOMETIME
BETWEEN NOW AND THEN. JUST TOO MUCH UNCERTAINTY TO GO FOR ANYTHING
MORE THAN WHAT WE HAVE RIGHT NOW: A STANDARD MID/HIGH GRADE MONSOON
FORECAST. PYTLAK

.TWC...NONE.

AZZ019-029>035-070700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1132 AM MST MON AUG 6 2001

.SYNOPSIS...DRY AIR AT LOW LEVELS AND A STABLE LAYER AT MID LEVELS
WILL LIMIT THUNDERSTORM ACTIVITY EAST OF A LINE FROM DOUGLAS AND
TUCSON. OTHERWISE...STORMS WILL DEVELOP OVER THE HIGHER TERRAIN OVER
SOUTH CENTRAL ARIZONA TODAY AND PUSH WEST INTO THE WESTERN DESERTS
BY LATE AFTERNOON. A NEAR CLIMATOLOGICAL THREAT OF SEVERE STORMS
WILL EXIST ALONG THIS LINE AND CLIMATOLOGICAL THREAT OF FLASH
FLOODING WILL EXIST WEST OF THIS LINE.

.DISCUSSION...ANOTHER LOW GRADE MONSOON DAY ON TAP FOR SOUTHEAST
ARIZONA TODAY AS DRY AIR OUT EAST COMBINED WITH A STABLE LAYER IN
THE ATMOSPHERE BETWEEN 15 AND 18 KFT WILL MAKE IT DIFFICULT FOR
THUNDERSTORMS TO DEVELOP. HOWEVER...GOES PRECIPITABLE WATER IMAGERY
INDICATES PLENTY OF LOW AND MID LEVEL MOISTURE OCCUPYING SPACE WEST
OF TUCSON. IN FACT...MORNING YUMA AND PHOENIX SOUNDINGS SHOW 1.70
AND 1.60 INCHES OF PRECIPITABLE WATER RESPECTIVELY. MOST OF THE
THUNDERSTORM ACTIVITY WILL OCCUR ALONG AND WEST OF THE MOISTURE
BOUNDARY...WHICH EXTENDS FROM DOUGLAS TO TUCSON. STORMS WILL DEVELOP
OVER THE HIGHER TERRAIN ALONG THIS MOISTURE BOUNDARY AND PUSH WEST AT
15 MPH OFF OF THE MOUNTAINS INTO THE LOWER DESERTS BY LATE THIS
AFTERNOON. THE HIGHER MOISTURE VALUES WILL BE ABLE TO SUSTAIN
THUNDERSTORM ACTIVITY.

THE BEST LOCATION FOR SEVERE STORMS WILL BE ALONG THE MOISTURE
BOUNDARY...WHERE DRY AIR RESIDES AT LOW LEVELS. THIS INVERTED-V
PROFILE WILL ENHANCE THE CHANCE FOR DOWNBURST WINDS. HOWEVER...WITH
A LIMITED COVERAGE OF THUNDERSTORMS...THE THREAT OF SEVERE STORMS IN
THIS PREFERRED AREA WILL BE SLIGHTLY BELOW CLIMATOLOGY.

A CLIMATOLOGICAL THREAT OF FLASH FLOODING DOES EXISTS WEST OF THE
MOISTURE BOUNDARY TODAY WHERE THE DEEPER MOISTURE RESIDES.

STORM MOVEMENT WILL BE TO THE WEST AT 15 MPH.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TUCSON ARIZONA
0501 PM MST MON AUG 6 2001

TIME (MST) .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0435 PM    ORGAN PIPE NATIONAL MONU  AZ   DUST STORM
08/06/01   PIMA                           VISIBILITY FELL TO 1/8 MILE FOR 20
                                          MINUTES.