Severe Thunderstorm Warning 27, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
208 PM MST SAT AUG 4 2001

.SYNOPSIS...A SUBTROPICAL DISTURBANCE WILL MOVE ACROSS SOUTHERN
ARIZONA TONIGHT AND INTO NORTHERN BAJA ON SUNDAY. IN ITS WAKE...THE
ATMOSPHERE SHOULD STABILIZE AND LEAD TO LESS THUNDERSTORM COVERAGE
ON SUNDAY AND POSSIBLY INTO MONDAY. MEANWHILE...HIGH PRESSURE WILL
REMAIN OVER THE GREAT BASIN...WHICH MAY ALLOW ANOTHER DISTURBANCE TO
MOVE WEST INTO THE REGION BY MID WEEK.

.DISCUSSION...SWOMCD/QPFERD/SWODY1 SUM THINGS UP WELL, ALTHOUGH I'M
STARTING TO SEE A COUPLE OF THINGS WHICH ARE BOTHERING ME. ANVILS
ARE MOVING AHEAD OF THE STORMS SO FAR, WHICH MEANS THAT IF THE MID
LEVEL FLOW DOESN'T PICK UP SOON, THE ANVILS MIGHT WIN AND REDUCE THE
TSTM COVERAGE SIGNIFICANTLY. ALSO, MUCH LIKE YESTERDAY, SUSTAINED
UPSLOPING FROM THE NW HASN'T DEVELOPED AS YET. KTUS HAS BEEN TRYING
TO SHIFT AROUND FOR A COUPLE OF HOURS NOW, AND KPHX AREA IS STILL S
OR LIGHT AND VARIABLE. IF THOSE MINUSES CAN BE OVERCOME, WE'RE
LOOKING AT AN ACTIVE LATE AFTERNOON/EVENING. DESERTS ARE NOW OVER
100+F, AND THE LEADING EDGE OF THE EASTERLY WAVE IS APPROACHING THE
NM/AZ BORDER. A COUPLE OF MOUNTAIN HUGGERS HAVE STARTED TO GET
PRETTY STRONG. CLOSER TO THE UPPER LOW, A CLUSTER CROSSING THE NM
BORDER E OF KDUG APPEARS TO HAVE GONE SURFACE-BASED. WE HAVE
HEIGHTENED WORDING AND MID-HIGH GRADE POPS IN OUR DRAFT ZONES, WHICH
WE MAY ADJUST UP OR DOWN DEPENDING ON HOW THINGS GO OVER THE NEXT
HOUR AND A HALF. UPPER LEVEL DIVERGENCE REMAINS FIXED OVER SE AZ
UNTIL 06Z WHEN IS IS PROGGED BY THE 18Z ETA TO SHIFT S OF THE
BORDER. GIVEN THE APPROACHING SUBTROPICAL LOW, WE'LL PROBABLY GET AN
MCS GOING RIGHT ALONG OUR BORDER TO JUST TO OUR S, WHICH WOULD KEEP
SPOTTY SHOWERS GOING FOR MUCH OF THE NIGHT. WE'LL WORD THE FORECAST
ACCORDINGLY.

MODELS ARE CONSISTENT IN WARMING OUR MID LEVELS ON SUN IN THE WAKE
OF THIS SUBTROPICAL LOW. THIS, IN ADDITION TO GETTING WORKED OVER
THIS EVENING, SHOULD LEAD TO A NOTICEABLE DOWN DAY SUN. I'D DROP
POPS EVEN MORE, BUT 20-25KT 500MB FLOW HAS ME CONCERNED THAT
ANYTHING THAT TRIES TO DEVELOP ON THE MOUNTAINS WILL STILL BE ABLE
TO MOVE INTO THE VALLEYS, ESPECIALLY LATE IN THE DAY WHEN OUR LOW
LEVELS WILL HAVE HAD A LITTLE TIME TO RECOVER. MON DOESN'T LOOK VERY
ACTIVE, EITHER, AS MID LEVEL TEMPS REMAIN WARM AND WE GET INTO WEAK
UPPER RIDGING AHEAD OF THE NEXT WAVE EXPECTED TO FORM OVER THE
EASTERN GULF OF MEXICO. THE MODELS, OF COURSE, USUALLY HAVE A ROUGH
TIME TRYING TO PICK UP THESE WAVES, LET ALONE TIME THEM PROPERLY.
THE ONE MOVING INTO US NOW MARCHED IN 24HRS FASTER THAN THE AVN
INDICATED ON THU. I'LL GO FOR A SLIGHT UPTICK ON MON SINCE THE
DESERTS WILL HAVE HAD TIME TO RECOVER, FOLLOWED BY A STANDARD
MID/HIGH GRADE FORECAST INTO THE EXTENDED. HOWEVER, I WOULDN'T BE
SURPRISED IF WE HAVE TO SPEED THE TIMING UP ON THE NEXT WAVE AS
WELL. POSITIONING OF THE UPPER HIGH IS GREAT FOR AN ACTIVE MONSOON
INTO THE END OF THE WEEK. HOWEVER, WE'LL HAVE TO KEEP AN EYE ON THE
MUCH DRIER AIR OVER S TX WHICH COULD ENTRAIN INTO THE EASTERN ZONES,
AND POSSIBLE REAMPLIFIwCATION OF THE WEST COAST TROUGH IN DAYS 6/7.
PYTLAK

.TWC...NONE.

AZZ019-029>035-050700-

SOUTHEAST ARIZONA HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TUCSON AZ
1145 PM MST SAT AUG 4 2001

.SYNOPSIS...AN UPSWING IN ACTIVITY IS EXPECTED TODAY AS AN UPPER
LEVEL DISTURBANCE INTERACTS WITH ABUNDANT MONSOON MOISTURE THIS
AFTERNOON AND EVENING. THE THREAT OF FLASH FLOODING AND SEVERE
THUNDERSTORMS WILL BE ABOVE CLIMATOLOGICAL NORMALS.

.DISCUSSION...LOW LEVELS STILL REMAIN VERY MOIST TUCSON AND WEST AND
LOW LEVEL FLOW WILL BE UPSLOPE THIS AFTERNOON...TO THE EAST THE LOW
LEVEL MOISTURE IS NOT AS GOOD BUT MID LEVEL MOISTURE VALUES STILL
HIGH. COLD LOW ANALYZED NEAR THE BIG BEND OF TEXAS THIS MORNING IS
MOVING WESTWARD...40 KNOTS OF WIND AT 300 MB OVER DEL RIO THIS
MORNING AND -10 TEMP AT 500 MB OVER EL PASO MAKES THIS LOOK LIKE A
VERY POTENT SYSTEM. MODELS PUSH THIS SYSTEM WESTWARD TODAY AND PLACE
ARIZONA IN FAVORABLE CYCLONIC FLOW AT 300 MB TONIGHT WHICH SHOULD
LOWER INERTIAL INSTABILITY. MODELS ALL SHOW DECENT OUTBREAK AND WITH
500 MB WINDS FRESHENING TO 15 KNOTS THERE WONT BE A PROBLEM MOVING
THE STORMS OFF THE MOUNTAINS. TIMING IS ONLY QUESTION...PROBABLY
WILL KICK OFF EARLIER THAN MODELS SHOW...EARLY AFTERNOON OUT EAST
AND LATE AFTERNOON TUCSON AREA. STORMS SHOULD PUNCH PRETTY FAR WEST
TONIGHT...POSSIBLY PAST ORGAN PIPE. SEVERE THREAT SEEMS MORE
IMPORTANT SINCE FLASH FLOOD THREAT WILL BE LIMITED BY SPEED OF
MOVEMENT OF STORMS. THERE IS SOME POTENTIAL THAT STORMS WILL BE
LARGER THAN NORMAL THEREBY INCREASING THE FLASH FLOOD THREAT.

STORM MOVEMENT WILL BE TO THE WEST AT 10 TO 15 MPH.