Flash Flood Warning 15, NWS Tucson, AZ

SOUTHEAST ARIZONA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
218 AM MST THU JUL 15 1999

SYNOPSIS...HIGH PRESSURE DEVELOPING SOUTH OF ARIZONA WILL SLOWLY
FEED DRIER AIR INTO THE REGION. HOWEVER...ANOTHER ROUND OF SCATTERED
THUNDERSTORMS CAN BE EXPECTED THIS AFTERNOON AND EVENING. WITH
PLENTY OF MOISTURE STILL AROUND...A FEW STORMS COULD ONCE AGAIN
PRODUCE HEAVY DOWNPOURS. THE HIGH PRESSURE AREA WILL GRADUALLY
MIGRATE INTO THE SOUTHERN PLAINS OVER THE WEEKEND. WHILE THIS STILL
FAVORS MONSOON THUNDERSTORMS...THE ACTIVITY WILL NOT BE AS
WIDESPREAD AS IT HAS BEEN RECENTLY.

DISCUSSION...WESTERLY FLOW HAS COMMENCED, BUT WERE NOT OUT OF THE
WOODS YET (OR TROPICAL RAIN FOREST AS THE CASE MAY BE). A SLEEPER
SHORT WAVE IN THE KLAS AREA, WHICH IS FUELING A SMALL, SLOW-MOVING
MCS NEAK KIGM, WAS ONLY PICKED UP WELL BY THE ETA AND RUC. THEY TAKE
IT ACROSS NORTHERN AZ TODAY WITH A TRAILING, WEAK LOBE THROUGH SE AZ
JUST AFTER 00Z. BASED ON CURRENT MOVEMENT, THAT MAY NOT BE TOO BAD.
FLOW AND SHEAR PROFILES ARENT AS STRONG AS YESTERDAY, SO THE DEGREE
OF RELOADING IS IN DOUBT. HOWEVER, DEEP TROPICAL MOISTURE REMAINS
(PRECIP WATERS IN THE 1.5-1.75 RANGE) WITH SOME MID LEVEL COOLING
EXPECTED. THERE WILL ALSO BE SOME UPPER DIVERGENCE BETWEEN THE VORT
AND THE 300MB HIGH TO OUR SOUTH. THIS MAY EXPLAIN THE ONGOING
CONVECTION ALONG OUR SOUTHERN BORDER AND ISOLATED ELEVATED SHOWERS
AS FAR NORTH AS PINAL COUNTY. THE SLOW DRYING MAY BE JUST ENOUGH TO
KEEP OUR FLASH FLOOD THREAT DOWN, BUT DAY SHIFT WILL HAVE TO WATCH
AND MAY NEED TO BEEF UP WORDING ONCE WE GET THE 12Z UPPER AIR DATA.
THE TORRENTIAL RAIN OVER THE NORTH AND EAST CWA LAST NIGHT HAS
REALLY SATURATED THINGS WITH MANY WASHES STILL RUNNING THIS MORNING.

TO SUM UP, PREVIOUS FORECAST IS IN GOOD SHAPE OTHER THAN A DOWNWARD
TWEAK ON HIGHS TODAY AND SLIGHT POP INCREASES FROM TUCSON EAST THIS
AFTERNOON/EVENING. TOMORROW DEFINITELY LOOKS LIKE A DOWNER WITH
LOWER THETA-E AND SOME WARMING ALOFT. WEAK FLOW SHOULD KEEP MUCH OF
THE ACTIVITY NEAR THE MOUNTAINS WITH A SLIGHT WARMUP DUE TO LESS
CLOUD COVER. NO MRF AVAILABLE AS YET, BUT OTHER MEDIUM RANGE MODELS
MAINTAIN A TROUGH JUST OFF THE WEST COAST. THAT SUPPORTS OUR CURRENT
EXTENDED WITH ONLY THE WESTERN DESERTS CUTOFF FROM THE MONSOON FLOW.
PYTLAK

.TWC...NONE.