Area Forecast Discussion
Issued by NWS Tucson, AZ

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FXUS65 KTWC 291016
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
315 AM MST TUE JUL 29 2014

.SYNOPSIS...A DRYING TREND WILL LIMIT THUNDERSTORMS TO MAINLY NEAR
THE NEW MEXICO AND INTERNATIONAL BORDERS EAST TO SOUTHEAST OF TUCSON
BY WEDNESDAY. INCREASING CHANCES OF THUNDERSTORMS WILL THEN OCCUR BY
FRIDAY FOLLOWED BY SCATTERED MAINLY AFTERNOON AND EVENING
THUNDERSTORMS THIS WEEKEND. EXPECT WARMER DAYTIME TEMPERATURES
THROUGH WEDNESDAY...THEN A MODERATION IN HIGH TEMPERATURES WILL
PREVAIL THIS WEEKEND.

&&

.DISCUSSION...HIGH PRESSURE ALOFT CENTERED OVER WEST TEXAS WITH
RIDGE AXIS EXTENDING NWWD INTO THE PACIFIC NW EARLY THIS MORNING.
BLENDED TOTAL PRECIP WATER VALUES VALID 0730Z RANGED FROM 1.25
INCHES ACROSS THE WHITE MOUNTAINS TO 1.55 INCHES ACROSS WRN PIMA
COUNTY. THESE VALUES ARE EXPECTED TO DECREASE TODAY ESPECIALLY FROM
TUCSON WWD AS MID-LEVEL DRYING OCCURS.

GIVEN THE VERY WEAK GENERALLY WLY STORM STEERING FLOW...ANY SHOWERS/
TSTMS THAT DEVELOP THIS AFTERNOON/EVENING WILL LIKELY BE CONFINED TO
NEAR THE MOUNTAINS. CONTINUED MID-LEVEL DRYING TO OCCUR WED DUE TO A
LIGHT GENERALLY NWLY FLOW REGIME. ANY SHOWERS/TSTMS THAT OCCUR WED
AFTERNOON/EVENING SHOULD BE NEAR THE NEW MEXICO/INTERNATIONAL
BORDERS EAST-TO-SOUTHEAST OF TUCSON.

29/00Z GFS/ECMWF DEPICTED THE LIGHT WLY/NWLY MID-LEVEL FLOW REGIME
TO CONTINUE THUR. HAVE REDUCED THE INHERITED POPS SOMEWHAT FOR THUR
AFTERNOON/EVENING. THE OFFICIAL FORECAST DEPICTS CHANCE-CATEGORY
POPS EAST-TO-SOUTH OF TUCSON THUR AFTERNOON/EVENING...WITH A SLIGHT
CHANCE OF SHOWERS FURTHER NW INTO WRN PIMA/SOUTH CENTRAL PINAL
COUNTIES. HOWEVER...THIS SCENARIO MAY BE OVERDONE AND ADDITIONAL
DOWNWARD POP ADJUSTMENTS FOR THUR MAY YET OCCUR.

THEREAFTER...GFS/ECWMF/CANADIAN MODELS WERE SIMILAR WITH DEPICTING
INCREASING MOISTURE STARTING FRI AND CONTINUING INTO THE WEEKEND AS
THE MID-LEVEL FLOW BECOMES MORE SELY. SCATTERED SHOWERS/TSTMS WILL
RETURN TO MUCH OF SE AZ FRI AFTERNOON/EVENING. GIVEN THIS FLOW
PATTERN...A POTENTIAL SCENARIO OF GUSTY OUTFLOWS PRODUCING BLOWING
DUST IS A FAIRLY DISTINCT POSSIBILITY. SCATTERED MAINLY AFTERNOON/
EVENING SHOWERS/TSTMS WILL THEN CONTINUE THIS WEEKEND. GFS/ECMWF
WERE FAIRLY SIMILAR WITH DEPICTING ANOTHER DRYING TREND MON. THUS...
SCATTERED SHOWERS/TSTMS MON SHOULD BE LIMITED TO ERN SECTIONS WITH
LESSER COVERAGE OF SHOWERS/TSTMS FROM TUCSON WWD INTO WRN PIMA
COUNTY.

HIGH TEMPS THIS AFTERNOON WILL GENERALLY BE ABOUT 5 DEGS F WARMER
VERSUS TEMPS ACHIEVED MON. SLIGHTLY WARMER DAYTIME TEMPS WILL OCCUR
WED FOLLOWED BY A COOLING TREND FRI-SUN.

&&

.AVIATION...VALID THRU 30/12Z.
ISOLATED -TSRA/-SHRA WILL BE MAINLY NEAR THE MOUNTAINS THIS
AFTERNOON AND THIS EVENING. OTHERWISE...MOSTLY CLEAR SKIES THRU MID-
MORNING THEN A FEW TO OCCASIONALLY BROKEN CLOUDS AROUND 8-12K FT AGL
LATE THIS MORNING INTO THIS EVENING. CLEARING SKIES MOST SECTIONS
AFTER ABOUT 30/04Z. SURFACE WIND WILL BE MOSTLY LESS THAN 10 KTS
INTO EARLY WEDNESDAY MORNING. AVIATION DISCUSSION NOT UPDATED FOR
TAF AMENDMENTS.

&&

.FIRE WEATHER...EXPECT THUNDERSTORMS TO BE LIMITED TO MAINLY NEAR
THE MOUNTAINS THROUGH THURSDAY. THEREAFTER...SCATTERED MOSTLY
AFTERNOON AND EVENING THUNDERSTORMS WILL RETURN STARTING FRIDAY AND
CONTINUE THIS WEEKEND AS DEEPER MOISTURE MOVES INTO THE AREA.
OTHERWISE...NORMAL DIURNAL WIND TRENDS WILL OCCUR WITH OCCASIONAL
GUSTS DURING THE AFTERNOON HOURS DUE TO DAYTIME HEATING.

&&

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

&&

$$

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

FRANCIS





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