609  
FXUS65 KPSR 172049  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
149 PM MST TUE JUL 17 2018  
   
SYNOPSIS
 
 
THE POTENTIAL FOR ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS  
WILL CONTINUE THROUGH MID-WEEK, BEFORE A GRADUAL DOWNTICK IN  
THUNDERSTORM ACTIVITY IS EXPECTED INTO THE WEEKEND. HIGH PRESSURE  
WILL BUILD ACROSS THE REGION LATER THIS WEEK, RESULTING IN A  
WARMING TREND AND RETURN TO ABOVE NORMAL TEMPERATURES BY EARLY  
NEXT WEEK.  
 

 
   
DISCUSSION
 
 
THE OVERALL WEATHER PATTERN HAS NOT CHANGED ALL TOO MUCH WITH THE  
UPPER HIGH STILL CENTERED OVER THE WEST COAST AND EASTERLY FLOW  
OVER ARIZONA. THE MIDLEVEL WATER VAPOR IMAGERY SHOWS A WELL  
DEFINED INVERTED TROUGH PROGRESSING THROUGH SONORA, WHICH WILL  
LIKELY PLAY A LARGE ROLE IN TODAY'S THUNDERSTORM ACTIVITY FOR  
SOUTHERN ARIZONA AS FAVORABLE DYNAMICS SUPPORTIVE OF CONVECTION  
WILL SPREAD ACROSS THE AREA. AHEAD OF THE TROUGH, SATELLITE  
DERIVED TOTAL PRECIPITABLE WATER INDICATES NEARLY 2.00" OF PW  
STRETCHING FROM PHOENIX SOUTHWEST TOWARDS YUMA, AND SIGNIFICANTLY  
LOWER PW IN THE DRYSLOT FURTHER EAST BEHIND THE TROUGH.  
 
THE CONVECTIVE-ALLOWING MODELS ARE STILL IN GOOD AGREEMENT SHOWING  
STORMS DEVELOPING IN TWO AREAS. THE FIRST IS ALONG THE RIM AND  
HIGHER TERRAIN ACROSS NORTHERN ARIZONA, AND EVENTUALLY MAKING WAY  
INTO LA PAZ COUNTY. THE SECOND AREA FOR CONVECTION IS MOST LIKELY  
TO BE ACROSS PIMA AND SOUTHERN MARICOPA COUNTY LATER THIS  
AFTERNOON IN ASSOCIATION WITH THE AFOREMENTIONED TROUGH WHERE CAPE  
VALUES WILL NEAR 2000 J/KG WITH AMPLE DAYTIME HEATING TO  
DESTABILIZE THE ATMOSPHERE. THUNDERSTORMS AND SHOWERS MAY HAVE  
ENOUGH ENERGY TO SUSTAIN THEMSELVES INTO THE YUMA-EL CENTRO AREAS  
LATE TONIGHT AND VERY EARLY TOMORROW MORNING. THE GREATEST WEATHER  
THREAT FOR THE PHOENIX AREA WILL BE GUSTY OUTFLOW WINDS AND  
BLOWING DUST FROM THE SOUTH DURING THE EVENING. WHILE UNLIKELY,  
THE CHANCE OF STORMS IN THE PHOENIX AREA CANNOT BE RULED OUT DUE  
THE THE INCREDIBLE AMOUNT OF MOISTURE IN THE ATMOSPHERE.  
 
FOR WEDNESDAY, THE INVERTED TROUGH WILL CONTINUE TO PROGRESS  
WESTWARD AS THE RIDGE REESTABLISHES ITSELF OVER THE SOUTHWEST.  
THE ATMOSPHERE WILL BEGIN TO DRY SOMEWHAT BUT THERE WILL BE ENOUGH  
MOISTURE FOR CONVECTION TOMORROW AFTERNOON, PRIMARILY ACROSS THE  
HIGHER TERRAIN. THUNDERSTORM ACTIVITY WILL CONTINUE TO DECREASE  
THE NEXT FEW DAYS AS THE CENTER OF THE RIDGE BUILDS OVER ARIZONA  
BY THE END OF THE WEEKEND.  
 

 
   
AVIATION
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, AND KSDL:  
 
LATEST GUIDANCE POINTS TO TWO SEPARATE AREAS OF CONVECTION TODAY,  
ONE ACROSS YAVAPAI COUNTY AND ONE FURTHER SOUTH ACROSS SOUTHERN  
ARIZONA, ASSOCIATED WITH AN INVERTED TROUGH. SHOWERS AND  
THUNDERSTORMS ARE UNLIKELY IN THE VALLEY TONIGHT, HOWEVER AN  
OUTFLOW BOUNDARY IS LIKELY TO MOVE THROUGH, EITHER FROM THE NORTH OR  
MORE LIKELY FROM THE ACTIVITY FROM THE SOUTH. IF AN OUTFLOW BOUNDARY  
FROM THE SOUTH REACHES THE AREA THIS EVENING, THERE IS SOME  
POTENTIAL FOR BLOWING DUST AND REDUCED VISIBILITIES.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
 
THUNDERSTORM ACTIVITY PROPAGATING SOUTHWESTWARD FROM LA PAZ COUNTY  
COULD REACH KBLH LATER THIS AFTERNOON, BRINGING BRIEF HEAVY RAINFALL  
AND ERRATIC WINDS. OTHERWISE, DIURNAL WINDS ARE EXPECTED ACROSS THE  
AREA.  
 
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.  
 

 
   
FIRE WEATHER
 
 
FRIDAY THROUGH TUESDAY:  
ISOLATED SHOWERS AND THUNDERSTORMS WILL REMAIN POSSIBLE FRIDAY,  
ESPECIALLY ACROSS THE HIGHER TERRAIN NORTH AND EAST OF THE PHOENIX  
AREA. HOWEVER, MOISTURE VALUES WILL UNDERGO A GRADUAL DECREASE  
INTO THE WEEKEND, AND EXPECTING ONLY A SLIGHT CHANCE OF ANY  
THUNDERSTORMS AREA-WIDE BY SATURDAY. DAYTIME MINIMUM RELATIVE  
HUMIDITY VALUES WILL ALSO FALL CLOSER TO 15%. A SIGNIFICANT  
INCREASE IN HEAT IS ADVERTISED FOR SUNDAY AND MONDAY, WITH HIGH  
TEMPERATURES ABOVE 110 DEGREES EXPECTED OVER THE LOWER DESERTS.  
THE WINDS WILL BE GENERALLY LIGHT AND FOLLOW TYPICAL DIURNAL  
TRENDS.  
 

 
   
SPOTTER INFORMATION STATEMENT
 
 
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...NONE.  
CA...NONE.  

 
 

 
 
DISCUSSION...DEEMER  
AVIATION...HIRSCH  
FIRE WEATHER...ROGERS/DEEMER  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab AZ Page
The Nexlab CA Page Main Text Page