Severe Thunderstorm Warning 5, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
213 PM MST THU JUN 17 1999

SYNOPSIS...HIGH PRESSURE OVER NEW MEXICO WILL REMAIN NEARLY
STATIONARY THROUGH SUNDAY. THE HIGH WILL CONTINUE TO PUMP MOIST AIR
INTO ARIZONA FROM THE SOUTH AND SOUTHEAST...RESULTING IN A DAILY
THREAT OF AFTERNOON AND EVENING THUNDERSTORMS. A DRIER AIR FLOW IS
NOT EXPECTED TO DEVELOP UNTIL AT LEAST TUESDAY.

DISCUSSION...RADAR ALREADY BUSY THIS AFTERNOON WITH A COUPLE OF
CELLS ALREADY NEAR SEVERE LIMITS. HAVE EVEN HAD MARBLE-SIZED HAIL ON
MT. LEMMON. STORMS GOT GOING EARLIER TODAY JUST EAST OF THE SANTA
CRUZ RIVER WHERE SATELLITE INDICATES SOME MID LEVEL CONVERGENCE.
WEAK SE-SW SHEAR IS ALSO FAVORABLE FOR SUSTAINING STRONG UPDRAFTS.
THUS WE'LL RETAIN THE HEIGHTENED WORDING AGAIN THIS EVENING.
RAPID-SCAN SATELLITE UPDATES WILL HELP OUT AS WE TRY TO KEEP TABS ON
ANY CELLS ENTERING BEAM-BLOCKED AREAS.

NEXT 2 DAYS COULD BE ALMOST AS BUSY. ORIGINALLY THOUGHT THAT THE
POCKET OF DRY AIR MOVING UP THE NORTHERN GULF OF CALIFORNIA WOULD
MODIFY THIS SOUP THAT ADVECTED IN FROM THE EAST. NO SUCH LUCK.
RECENT GOES PRECIP WATER IMAGERY SHOWS A BLOB OF 1.5" PRECIP WATER
GATHERING OVER THE SOUTHERN GULF AND GETTING ENTRAINED NORTH. I ALSO
SEE NO REASON FOR THIS WEAK, LOW LEVEL, SE FLOW TO SHUT DOWN. AFTER
GETTING WORKED OVER TODAY AND WITH SLIGHTLY WEAKER MID LEVEL SHEAR
TOMORROW, I THINK WE'LL RAMP DOWN JUST A LITTLE BEFORE THE SHEAR
INCREASES AGAIN SATURDAY. WE MAY ALSO GET A LITTLE HELP FROM
DYNAMICS SATURDAY WHEN THE WEAK UPPER LOW OFF THE CENTRAL BAJA JOGS
NORTH TO THE N BAJA. BASIC GIST OF THE FORECAST IS TO HAVE SCATTERED
AFTERNOON/EVENING ACTIVITY RIGHT INTO THE EXTENDED. IF MEDIUM RANGE
MODELS WERE IN BETTER AGREEMENT OF WHEN DRIER SW FLOW WILL KICK IN,
I'D TRY TO SWITCH TO SCATTERED WORDING IN THE EXTENDED INSTEAD OF
USING THE "CHANCE" BROADBRUSH. NO SENSE FINESSING, THOUGH, WITH
BASIC PAbTTERN SHOWING NO SIGNS OF CHANGING UNTIL DAY 5 OR SO. TO
GIVE YOU AN IDEA ON HOW RARE THIS IS, THE CLIMO CHANCE OF PRECIP FOR
JUNE 17 IN TUCSON IS A WHOPPING 4% (IT'S RAINED ONLY 4 TIMES IN 129
YEARS OF RECORDS). PYTLAK

.TWC...NONE.