Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 012242
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
340 PM MST SAT AUG 1 2015

.SYNOPSIS...EXPECT SCATTERED THUNDERSTORMS THIS EVENING FOLLOWED BY
DECREASING RAINFALL CHANCES LATE TONIGHT. A GRADUAL DAILY REDUCTION
IN THUNDERSTORM COVERAGE WILL THEN OCCUR SUNDAY THROUGH TUESDAY.
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS MAINLY FROM TUCSON
EAST AND SOUTH WILL RETURN DURING THE LATTER PART OF THE UPCOMING
WEEK.

&&

.DISCUSSION...SCATTERED SHOWERS AND THUNDERSTORMS WERE OCCURRING
ACROSS MUCH OF SE ARIZONA AT THIS TIME. HOWEVER...PRECIP-FREE
CONDITIONS WERE ONGOING ACROSS WRN PIMA COUNTY...SOUTH CENTRAL PINAL
COUNTY AND PORTIONS OF THE TOHONO O`ODHAM NATION. EXPECT SCATTERED
SHOWERS/TSTMS ESPECIALLY FROM TUCSON EAST AND SOUTH THIS EVENING
FOLLOWED BY DECREASING COVERAGE OF SHOWERS/TSTMS LATE TONIGHT. BASED
ON THE 01/12Z NAM/GFS/ECMWF...THERE SHOULD BE ENOUGH MOISTURE/
INSTABILITY TO MAINTAIN A SLIGHT CHANCE OF SHOWERS/TSTMS LATE
TONIGHT AND EARLY SUN MORNING FROM TUCSON EAST AND SOUTH TO THE NEW
MEXICO/INTERNATIONAL BORDERS.

01/12Z NAM/GFS/ECMWF/CMC WERE IN GOOD AGREEMENT WITH DEPICTING A
DRYING TREND TO COMMENCE SUNDAY AND CONTINUE INTO TUE...AT LEAST.
HIGH PRESSURE ALOFT IS PROGGED TO BE CENTERED OVER FAR WEST TEXAS
SUN MORNING...WITH A SHORTWAVE TROUGH OVER THE GREAT BASIN AND NWRN
ARIZONA. 700-300 MB SWLY FLOW SUN WILL BECOME INCREASINGLY WLY MON
AND CONTINUE WITH GENERALLY LIGHT WLY FLOW TUE AS THE UPPER HIGH
BECOMES POSITIONED JUST SOUTH OF THIS FORECAST AREA OVER NRN SONORA.

THIS WIND REGIME WILL TRANSLATE INTO ISOLATED TO SCATTERED SHOWERS/
TSTMS FROM TUCSON EWD/SWD SUN AND MON. BY TUE...THERE IS ONLY A
SLIGHT CHANCE OF SHOWERS/TSTMS MAINLY NEAR THE MOUNTAINS WITH DRY
CONDITIONS ELSEWHERE. A SIMILAR PRECIP REGIME MAY ACTUALLY OCCUR
WED...AT LEAST BASED ON THE GFS/ECMWF/CMC SOLUTIONS. FOR NOW...
OPTED TO CONTINUE WITH A SLIGHT CHANCE OF SHOWERS/TSTMS ACROSS MUCH
OF SE ARIZONA WED.

THEREAFTER...THE GFS/ECMWF WERE FAIRLY SIMILAR WITH DEPICTING DEEPER
MOISTURE TO RETURN TO THIS FORECAST AREA STARTING THUR AND
CONTINUING INTO NEXT SAT. THESE SOLUTIONS SEEM PLAUSIBLE AS THE MID-
LEVEL STEERING FLOW BECOMES INCREASINGLY SLY IN RESPONSE TO THE
UPPER HIGH BECOMING POSITIONED AGAIN OVER WEST TEXAS...AND AN UPPER
TROUGH ADJACENT THE CALIFORNIA COAST. THUS...SCATTERED SHOWERS/TSTMS
WILL RETURN THUR-SAT MAINLY FROM TUCSON EWD/SWD TO THE NEW MEXICO/
INTERNATIONAL BORDERS.

EXPECT ABOUT A DEGREE-OR-TWO OF DAILY WARMING SUN-TUE FOLLOWED BY A
VERY GRADUAL REDUCTION IN DAYTIME TEMPS DURING THE LATTER PART OF
THE UPCOMING WEEK.

&&

.AVIATION...VALID THRU 03/00Z.
SCT TO BKN CLOUDS 6-10K FT AGL WITH SCT SHRA/TSRA UNTIL AROUND
02/02Z MAINLY EAST OF A KTUS TO KOLS LINE. BRIEF MVFR CONDITIONS
WITH ERRATIC WIND GUSTS TO 45 KTS POSSIBLE IN AND AROUND THE
STRONGER TSRA. OUTSIDE OF STORM INFLUENCES SFC WINDS WILL GENERALLY
BE LESS THAN 12 KTS WITH A FEW HIGHER GUSTS IN THE AFTERNOON/EARLY
EVENING HOURS. EXPECT CLEARING SKIES LATE TONIGHT INTO SUNDAY
MORNING BEFORE REDEVELOPMENT OF ISO-SCT SHRA/TSRA DURING THE EARLY
AFTERNOON...MAINLY E OF KTUS/KOLS AND ESP NEAR TERRAIN. AVIATION
DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
THROUGH THIS EVENING WITH STRONG OUTFLOW WINDS POSSIBLE...ESPECIALLY
ACROSS EASTERN ZONES. SOUTHWEST WINDS ALOFT ON SUNDAY WILL USHER
DRIER AIR INTO THE REGION...WHICH WILL LIMIT PRECIPITATION CHANCES
ON MONDAY AND ESPECIALLY ON TUESDAY. HIGH PRESSURE RETURNS TO A MORE
FAVORABLE LOCATION FOR DAILY CHANCES OF MONSOON SHOWERS AND
THUNDERSTORMS FROM WEDNESDAY ONWARD.

OUTSIDE OF THUNDERSTORM WIND GUSTS...20-FT WINDS WILL GENERALLY BE
TERRAIN DRIVEN AND LESS THAN 15 MPH. HOWEVER SOME AFTERNOON AND
EARLY EVENING BREEZINESS IS LIKELY DUE TO DAYTIME HEATING...
ESPECIALLY THROUGH THE GILA VALLEY NEAR SAFFORD.

&&

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

&&

$$

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

DISCUSSION...FRANCIS
AVIATION/FIRE WEATHER...FRENCH



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