Weather Service Report


873 
FXUS65 KTWC 311110
AFDTWC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TUCSON AZ
410 AM MST THU JUL 31 2014

.SYNOPSIS...EXPECT SCATTERED SHOWERS AND THUNDERSTORMS THROUGH 
TONIGHT FOLLOWED BY A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS INTO 
THIS WEEKEND. GUSTY OUTFLOWS WILL PRODUCE AREAS OF BLOWING DUST...
ESPECIALLY FRIDAY AFTERNOON. PERIODS OF HEAVY RAINFALL MAY THEN 
OCCUR THIS WEEKEND. A COOLING TREND WILL PREVAIL INTO THE WEEKEND 
FOLLOWED BY DRIER CONDITIONS AND WARMER TEMPERATURES BY THE MIDDLE 
OF NEXT WEEK.

&&

.DISCUSSION...CLOUDINESS ALONG WITH SCATTERED SHOWERS PRODUCING 
LIGHT RAIN HAS INCREASED DURING THE PAST 2-3 HOURS IN RESPONSE TO A 
DECAYING MCS OVER SONORA MEXICO. A FEW LIGHTNING STRIKES HAVE BEEN 
DETECTED NEAR SELLS AND GREEN VALLEY. OTHERWISE...LIGHTNING STRIKES 
HAVE BEEN LIMITED TO NERN SONORA AND ACROSS SWRN NEW MEXICO. 31/08Z 
RUC HRRR DEPICTS FAIRLY EXTENSIVE COVERAGE OF SHOWERS PRODUCING 
MOSTLY LIGHT RAINFALL THRU ABOUT MID-MORNING. RAINFALL COVERAGE IS 
THEN PROGGED TO DECREASE LATE THIS MORNING INTO EARLY THIS 
AFTERNOON. 

A POTENTIAL SCENARIO FOR TODAY INTO THIS EVENING IS THAT CONVECTIVE 
DEBRIS CLOUDS THIS MORNING WILL INHIBIT MORE WIDESPREAD COVERAGE OF 
SHOWERS/TSTMS THIS AFTERNOON/EVENING. HOWEVER...HAVE OPTED FOR THE 
SCENARIO CONSISTING OF MORE SUBSTANTIAL SHOWER/TSTM ACTIVITY TO 
OCCUR THIS AFTERNOON AND THIS EVENING. THUS...THE OFFICIAL FORECAST 
DEPICTS ISOLATED SHOWERS/TSTMS AREA-WIDE THIS MORNING...THEN 
SCATTERED SHOWERS/TSTMS THIS AFTERNOON/EVENING. GUSTY OUTFLOWS MAY 
PRODUCE LOCALIZED BLOWING DUST SIMILAR TO WED. HOWEVER...WIDESPREAD 
BLOWING DUST IS NOT EXPECTED TO OCCUR AT THIS TIME. LOCALLY HEAVY 
RAINFALL MAY OCCUR WITH THE STRONGER SHOWERS/TSTMS. HAVE MAINTAINED 
ISOLATED SHOWERS/TSTMS FOR MUCH OF THE AREA LATE TONIGHT.

FRI...
A GREATER COVERAGE OF SHOWERS/TSTMS WILL OCCUR FRI DUE TO THE 
PROGGED MOISTURE INCREASE AND A MORE FAVORABLE SELY MID-LEVEL FLOW. 
GUSTY OUTFLOWS PRODUCING MORE WIDESPREAD AREAS OF BLOWING DUST IS A 
MORE DISTINCT POSSIBILITY FRI AFTERNOON INTO FRI EVENING... 
ESPECIALLY NW OF TUCSON. THUS...HAVE OPTED FOR AREAS OF BLOWING DUST
ACROSS SOUTH CENTRAL PINAL COUNTY FRI AFTERNOON/EVENING. ISOLATED TO 
SCATTERED SHOWERS/TSTMS SHOULD CONTINUE LATE FRI NIGHT.

SAT-SUN...
31/00Z GFS/ECMWF MOISTURE FIELDS WERE SUFFICIENT TO JUSTIFY 
INCREASED POPS VERSUS THE INHERITED FORECAST. GFS/ECWMF ALSO 
CONTINUED TO DEPICT A WEAK AREA OF LOW PRESSURE ALOFT TO BE OVER SE 
AZ...BETWEEN HIGH PRESSURE CENTERED OVER NRN AZ AS WELL AS OVER SRN 
CHIHUAHUA. SLIGHTLY DRIER CONDITIONS MAY ENCROACH UPON WRN SECTIONS 
SUN AS THE WEAK UPPER LOW DRIFTS INTO NRN AZ. 

AT ANY RATE...THE COMBINATION OF AMPLE MOISTURE ALONG WITH THE WEAK 
AREA OF LOW PRESSURE ALOFT SHOULD PROVIDE SCATTERED TO NUMEROUS 
SHOWERS/TSTMS. AM CONCERNED THAT THE POTENTIAL FOR HEAVY RAINFALL 
AND FLASH FLOODING WILL BE ENHANCED...ESPECIALLY SAT...AS WEAK 
MID-LEVEL STEERING FLOW TRANSLATES INTO SLOW STORM MOTIONS.

MON-WED...
GFS/ECMWF WERE SIMILAR WITH DEPICTING DRIER AIR TO ADVECT INTO SE AZ 
MON AS HIGH PRESSURE ALOFT WILL BE CENTERED OVER CHIHUAHUA...AND A 
TROUGH OF LOW PRESSURE EXISTS OVER THE GREAT BASIN. A GRADUAL DRYING 
TREND SHOULD CONTINUE TUE-WED UNDER WLY/NWLY FLOW ALOFT. 
THUS...EXPECT ISOLATED TO SCATTERED SHOWERS/TSTMS MON AFTERNOON/ 
EVENING...THEN ISOLATED SHOWERS/TSTMS ARE FORECAST TO BE CONFINED TO 
MAINLY NEAR THE NEW MEXICO BORDER NEXT WED. 

A COOLING TREND WILL OCCUR THRU SAT FOLLOWED BY WARMER DAYTIME 
TEMPERATURES EARLY NEXT WEEK.

&&

.AVIATION...VALID THRU 01/12Z.
SCATTERED TSRA/SHRA WILL OCCUR INTO EARLY FRIDAY MORNING AS MOISTURE 
INCREASES ACROSS THE AREA. EXPECT MVFR VISIBILITIES WITH +TSRA AS 
WELL AS WIND GUSTS TO AROUND 40-45 KTS. THE BEST OCCURRENCE FOR THE 
STRONGEST GUSTS WILL BE THIS AFTERNOON AND EARLY THIS EVENING. 
OTHERWISE...CLOUD DECKS WILL GENERALLY BE AT 8-15K FT AGL INTO EARLY 
FRIDAY MORNING. AVIATION DISCUSSION NOT UPDATED FOR TAF AMENDMENTS.

&&

.FIRE WEATHER...SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR 
THROUGH TONIGHT FOLLOWED BY A GOOD CHANCE OF SHOWERS AND 
THUNDERSTORMS INTO THIS WEEKEND. EXPECT STRONG...GUSTY AND ERRATIC 
WINDS WITH THE STRONGER THUNDERSTORMS. INCREASING MOISTURE WILL ALSO 
TRANSLATE INTO PERIODS OF HEAVY RAINFALL AND COOLER TEMPERATURES 
THIS WEEKEND...PARTICULARLY SATURDAY. THEREAFTER...A DRYING TREND 
WITH WARMER TEMPERATURES WILL PREVAIL BY THE MIDDLE OF NEXT WEEK.

&&

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

&&

$$

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FRANCIS



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