Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 210953
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
255 AM MST SUN SEP 21 2014

.SYNOPSIS...DRIER AIR WILL BEGIN TO MOVE INTO THE REGION TODAY
WHICH WILL REDUCE RAIN CHANCES THROUGH THE MIDDLE OF THE WORK WEEK.
AN INCREASE IN SHOWERS AND THUNDERSTORMS IS EXPECTED BY THURSDAY AND
FRIDAY. NEAR-NORMAL HIGH TEMPERATURES ARE ANTICIPATED THE REST OF
THIS WEEKEND AND NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY THIS MORNING PLACED UPPER LOW OVER
CENTRAL CALIFORNIA LIFTING TO THE NE. THIS FEATURE IS BRINGING DRIER
AIR INTO THE REGION...ESPECIALLY OUT WEST. HOWEVER THE EASTERN AREAS
WILL HANG ON TO ENOUGH MOISTURE FOR A CHANCE OF AFTERNOON AND EARLY
EVENING THUNDERSTORMS...SOME OF WHICH WILL BE ISOLATED HEAVY
RAINERS.

DRYING TREND CONTINUES ON MONDAY UNDER WESTERLY FLOW ALOFT. EASTERN
AREAS HOLDING ON TO ENOUGH MOISTURE FOR A SLIGHT CHANCE OF STORMS.

DRYING TREND CONTINUES AS UPPER HIGH BUILDS OVER THE AREA TUESDAY
AND WEDNESDAY. ANY CHANCE OF STORMS WILL BE MAINLY OVER THE HIGHER
TERRAIN EAST AND SOUTH OF TUCSON.

THURSDAY WILL BE TRANSITION DAY AS UPPER HIGH PUSHES ON EAST IN
RESPONSE TO STRONG PACIFIC SYSTEM MOVING TOWARD THE PACIFIC NW. FLOW
ALOFT BECOMES MORE SOUTHERLY THUS INCREASING PW VALUES ACROSS THE
AREA. THUS EXPECT A SLIGHT UPTICK IN THUNDERSTORM COVERAGE BUT STILL
FAVORING THE HIGHER TERRAIN EAST AND SOUTH OF TUCSON.

STILL SOME TIMING/DEPTH DIFFERENCES BETWEEN GFS/ECMWF WITH RESPECTS
TO THE ABOVE MENTIONED TROF MOVING INTO INTERMOUNTAIN WEST.
SOUTHERLY FLOW OUT AHEAD OF THIS SYSTEM WILL INCREASE MOISTURE
ACROSS THE AREA FOR BETTER CHANCE OF AFTERNOON/EVENING STORMS. THE
THREAT OF STORMS BEING SEVERE WILL ALSO BE ON THE INCREASE.

AFTERNOON HIGHS WILL CONTINUE SLOW WARMUP THROUGH MID WEEK AND THEN
GRADUALLY COOL TOWARD NEXT WEEKEND.

&&

.AVIATION...VALID THRU 22/12Z. ISOLD -SHRA E OF KTUS THIS MORNING
THEN ISOLD TO SCTD -SHRA/-TSRA WILL THEN OCCUR FROM KTUS VICINITY
EAST AND SOUTH THIS AFTN INTO THIS EVENG. MVFR CONDITIONS AND BRIEF
WIND GUSTS TO AROUND 30 KTS WILL OCCUR WITH SHRA/TSRA. OTHERWISE...
SURFACE WIND WILL BE MAINLY LESS THAN 10 KTS THRU SUNDAY AFTERNOON.
AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED MAINLY AFTERNOON AND EVENING SHOWERS AND
THUNDERSTORMS WILL OCCUR ESPECIALLY FROM TUCSON EASTWARD AND
SOUTHWARD TODAY AND MONDAY. SOMEWHAT DRIER CONDITIONS WILL PRODUCE
LESS COVERAGE OF SHOWERS AND THUNDERSTORMS TUESDAY AND WEDNESDAY.
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS WILL THEN PREVAIL
THURSDAY THROUGH SATURDAY. BRIEF GUSTY OUTFLOWS WILL OCCUR WITH THE
STRONGER THUNDERSTORMS. OTHERWISE...20-FOOT WINDS WILL GENERALLY BE
LESS THAN 15 MPH INTO THE UPCOMING WEEK.

&&

.HYDROLOGY...THE POSSIBILITY EXITS THIS AFTERNOON FOR ISOLATED HEAVY
RAINERS ON THE HEADWATERS OF THE GILA RIVER IN NEW MEXICO. IF THIS
OCCURS LIKE IT DID ON SATURDAY LIKELY WILL SEE ANOTHER INCREASE IN
FLOW...ESPECIALLY AT DUNCAN...BUT LEVELS WILL REMAIN WELL BELOW
BANKFULL.

&&

.TWC WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

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