Weather Service Report


031 
FXUS65 KTWC 211736
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
1035 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...IR/VISIBLE SATELLITE IMAGERY AND SURFACE OBSERVATIONS 
INDICATED SUNNY SKIES ACROSS WRN PIMA COUNTY WITH PARTLY CLOUDY 
SKIES ELSEWHERE ACROSS SE AZ. DEWPOINTS AT LOWER ELEVATIONS VALID 
17Z WERE GENERALLY IN THE LOWER-MID 60S F...AND THESE TEMPS WERE 
NEARLY IDENTICAL TO 24 HOURS AGO. SURFACE TEMPS VALID 17Z WERE ALSO 
GENERALLY UNCHANGED VERSUS THIS TIME SAT. 21/12Z KTWC SOUNDING 
PRECIP WATER WAS 1.50 INCHES...A DECREASE OF 0.15 INCH VERSUS 24 
HOURS AGO. THE ENVIRONMENT WAS MARGINALLY UNSTABLE WITH LIFTED INDEX 
OF MINUS 2...AND UNMODIFIED SBCAPE OF 893 J/KG. 21/12Z UPPER AIR 
PLOTS INDICATED WEAK UPPER LOW CENTERED OVER CENTRAL CALIFORNIA WITH 
HIGH PRESSURE CENTERED OVER WEST TEXAS. LIGHT TO MODERATE SLY/SWLY 
FLOW PREVAILED OVER SE AZ.

21/12Z NAM/GFS/UNIV OF AZ WRF-NAM/UNIV OF AZ WRF-GFS WERE VERY 
SIMILAR WITH DEPICTING SCATTERED SHOWERS/TSTMS TO OCCUR EAST AND 
SOUTH OF TUCSON THIS AFTERNOON AND THIS EVENING. PRECIP-FREE 
CONDITIONS WERE PROGGED TO OCCUR FROM TUCSON WWD/NWWD INTO WRN PIMA 
COUNTY AND SOUTH CENTRAL PINAL COUNTY. THESE SOLUTIONS WERE QUITE 
SIMILAR TO THE INHERITED OFFICIAL FORECAST...EXCEPT FOR RAINFALL 
POTENTIAL FOR THE TUCSON METRO AREA. FOR NOW...HAVE OPTED TO 
MAINTAIN SCATTERED SHOWERS/TSTMS THIS AFTERNOON/EVENING FOR TUCSON. 
THE BULK OF ANY PRECIP SHOULD END BY AROUND 22/07Z...OR ABOUT 
MIDNIGHT TONIGHT. FOR NOW WILL MAINTAIN A SLIGHT CHANCE OF SHOWERS/
TSTMS LATE TONIGHT ACROSS ERN SECTIONS WITH PRECIP-FREE CONDITIONS 
ELSEWHERE. HIGH TEMPS THIS AFTERNOON WILL GENERALLY BE ABOUT 2-3 
DEGS F WARMER VERSUS TEMPS ACHIEVED SAT.

PLEASE REFER TO THE ADDITIONAL SECTIONS FOR FURTHER DETAIL.

&&

.AVIATION...VALID THRU 22/18Z.
ISOLATED -SHRA EAST OF KTUS THIS MORNING THEN SCATTERED -SHRA/-TSRA 
FROM KTUS VICINITY EAST AND SOUTH THIS AFTERNOON AND THIS EVENING. 
EXPECT MVFR CONDITIONS AND BRIEF WIND GUSTS TO AROUND 30 KTS WITH
THE STRONGER THUNDERSTORMS. ISOLATED -SHRA/-TSRA MAY OCCUR EAST OF 
KTUS LATE TONIGHT AND EARLY MONDAY MORNING. OTHERWISE...SURFACE WIND 
WILL BE MAINLY LESS THAN 10 KTS THRU MONDAY MORNING. 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 THROUGH 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.

&&

.PREV DISCUSSION...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.

&&

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

&&

$$

VISIT US ON FACEBOOK...TWITTER...YOUTUBE...AND AT WEATHER.GOV/TUCSON

FRANCIS



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