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000
FXUS65 KPSR 040950 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
250 AM MST MON MAY 4 2015

.UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTH
ACROSS THE GREATER PHOENIX AREA THROUGH AT LEAST 12Z...AFFECTING ALL
OF THE TAF SITES. EXPECTING CIGS TO LOWER TO AROUND 4-6KFT...AND
THIS WILL VARY BASED ON INTENSITY OF PASSING SHOWERS...THROUGH
APPROX 15Z AND THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z AIDED BY HEAT OF THE DAY...BUT AT THIS POINT WILL ONLY
MENTION VCTS AS CONFIDENCE IN AREAL COVERAGE IS LOW. WINDS WILL BE
TRICKY DUE TO THE NATURE OF SCATTERED SHOWERS/STORMS...WITH
DIRECTIONS RAPIDLY CHANGING FROM TIME TO TIME AS OUTFLOW MOVE
THROUGH THE AREA. EXPECT WINDS TO FAVOR AN EASTERLY COMPONENT MOST
OF THE TIME THROUGH LATE MORNING...THEN RETURNING TO THE SOUTHWEST
DURING THE AFTERNOON HOURS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS WITH A
COOOLING TREND TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD
INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FRIDAY WILL LIKELY BE THE COOLEST DAY WITH HIGH TEMPERATURES
ACROSS THE LOWER DESERTS FALLING INTO THE LOW TO MIDDLE 80S. FIRE
DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD AS
AFTERNOON HUMIDITIES FALL INTO THE TEENS. A WARMING TREND WILL TAKE
PLACE THIS WEEKEND...AND THERE WILL BE LESS WIND AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST
AND HIGHER PRESSURE ALOFT BUILDS INTO THE AREA FROM THE WEST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS/CB
FIRE WEATHER...PERCHA/CB




000
FXUS65 KPSR 040950 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
250 AM MST MON MAY 4 2015

.UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTH
ACROSS THE GREATER PHOENIX AREA THROUGH AT LEAST 12Z...AFFECTING ALL
OF THE TAF SITES. EXPECTING CIGS TO LOWER TO AROUND 4-6KFT...AND
THIS WILL VARY BASED ON INTENSITY OF PASSING SHOWERS...THROUGH
APPROX 15Z AND THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z AIDED BY HEAT OF THE DAY...BUT AT THIS POINT WILL ONLY
MENTION VCTS AS CONFIDENCE IN AREAL COVERAGE IS LOW. WINDS WILL BE
TRICKY DUE TO THE NATURE OF SCATTERED SHOWERS/STORMS...WITH
DIRECTIONS RAPIDLY CHANGING FROM TIME TO TIME AS OUTFLOW MOVE
THROUGH THE AREA. EXPECT WINDS TO FAVOR AN EASTERLY COMPONENT MOST
OF THE TIME THROUGH LATE MORNING...THEN RETURNING TO THE SOUTHWEST
DURING THE AFTERNOON HOURS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS WITH A
COOOLING TREND TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD
INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FRIDAY WILL LIKELY BE THE COOLEST DAY WITH HIGH TEMPERATURES
ACROSS THE LOWER DESERTS FALLING INTO THE LOW TO MIDDLE 80S. FIRE
DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD AS
AFTERNOON HUMIDITIES FALL INTO THE TEENS. A WARMING TREND WILL TAKE
PLACE THIS WEEKEND...AND THERE WILL BE LESS WIND AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST
AND HIGHER PRESSURE ALOFT BUILDS INTO THE AREA FROM THE WEST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS/CB
FIRE WEATHER...PERCHA/CB





000
FXUS65 KPSR 040950 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
250 AM MST MON MAY 4 2015

.UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTH
ACROSS THE GREATER PHOENIX AREA THROUGH AT LEAST 12Z...AFFECTING ALL
OF THE TAF SITES. EXPECTING CIGS TO LOWER TO AROUND 4-6KFT...AND
THIS WILL VARY BASED ON INTENSITY OF PASSING SHOWERS...THROUGH
APPROX 15Z AND THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z AIDED BY HEAT OF THE DAY...BUT AT THIS POINT WILL ONLY
MENTION VCTS AS CONFIDENCE IN AREAL COVERAGE IS LOW. WINDS WILL BE
TRICKY DUE TO THE NATURE OF SCATTERED SHOWERS/STORMS...WITH
DIRECTIONS RAPIDLY CHANGING FROM TIME TO TIME AS OUTFLOW MOVE
THROUGH THE AREA. EXPECT WINDS TO FAVOR AN EASTERLY COMPONENT MOST
OF THE TIME THROUGH LATE MORNING...THEN RETURNING TO THE SOUTHWEST
DURING THE AFTERNOON HOURS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS WITH A
COOOLING TREND TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD
INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FRIDAY WILL LIKELY BE THE COOLEST DAY WITH HIGH TEMPERATURES
ACROSS THE LOWER DESERTS FALLING INTO THE LOW TO MIDDLE 80S. FIRE
DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD AS
AFTERNOON HUMIDITIES FALL INTO THE TEENS. A WARMING TREND WILL TAKE
PLACE THIS WEEKEND...AND THERE WILL BE LESS WIND AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST
AND HIGHER PRESSURE ALOFT BUILDS INTO THE AREA FROM THE WEST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS/CB
FIRE WEATHER...PERCHA/CB




000
FXUS65 KPSR 040950 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
250 AM MST MON MAY 4 2015

.UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTH
ACROSS THE GREATER PHOENIX AREA THROUGH AT LEAST 12Z...AFFECTING ALL
OF THE TAF SITES. EXPECTING CIGS TO LOWER TO AROUND 4-6KFT...AND
THIS WILL VARY BASED ON INTENSITY OF PASSING SHOWERS...THROUGH
APPROX 15Z AND THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z AIDED BY HEAT OF THE DAY...BUT AT THIS POINT WILL ONLY
MENTION VCTS AS CONFIDENCE IN AREAL COVERAGE IS LOW. WINDS WILL BE
TRICKY DUE TO THE NATURE OF SCATTERED SHOWERS/STORMS...WITH
DIRECTIONS RAPIDLY CHANGING FROM TIME TO TIME AS OUTFLOW MOVE
THROUGH THE AREA. EXPECT WINDS TO FAVOR AN EASTERLY COMPONENT MOST
OF THE TIME THROUGH LATE MORNING...THEN RETURNING TO THE SOUTHWEST
DURING THE AFTERNOON HOURS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS WITH A
COOOLING TREND TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD
INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FRIDAY WILL LIKELY BE THE COOLEST DAY WITH HIGH TEMPERATURES
ACROSS THE LOWER DESERTS FALLING INTO THE LOW TO MIDDLE 80S. FIRE
DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD AS
AFTERNOON HUMIDITIES FALL INTO THE TEENS. A WARMING TREND WILL TAKE
PLACE THIS WEEKEND...AND THERE WILL BE LESS WIND AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST
AND HIGHER PRESSURE ALOFT BUILDS INTO THE AREA FROM THE WEST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS/CB
FIRE WEATHER...PERCHA/CB





000
FXUS65 KPSR 040904
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
205 AM MST MON MAY 4 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 040904
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
205 AM MST MON MAY 4 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA




000
FXUS65 KPSR 040904
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
205 AM MST MON MAY 4 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE ACROSS THE REGION THIS WEEK...KEEPING TEMPERATURES BELOW NORMAL
THROUGH THE ENTIRE PERIOD. THE FIRST IN THIS SERIES OF DISTURBANCES
IS EXPECTED TO PRODUCE SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA TODAY AND TUESDAY. A
SECOND...COLDER DISTURBANCE IS THEN EXPECTED TO BRING EVEN COOLER
TEMPERATURES...AND GUSTY WINDS FOR THE END OF THIS WEEK.

&&

.DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR THE SHORT-TERM...LATEST FORECASTS CONTINUE TO BE ON TRACK ON THE
DETAILS OF A RATHER STRONG...AND MOIST (FOR MAY) UPPER LOW THAT IS
NOW PRODUCING SCATTERED SHOWERS AND THUNDERSTORMS ACROSS SOUTH-
CENTRAL ARIZONA. THE COMBINATION OF RATHER HIGH PWATS (AROUND 0.90
INCH) AND DECENT INSTABILITY (LI`S IN THE -2 TO -4 RANGE)...ALONG
WITH GOOD DIFFLUENCE ALOFT IS WHAT IS TRIGGERING THIS ACTIVITY. THE
LATEST FORECASTS SOUNDINGS SUGGEST THAT THIS ACTIVITY WILL CONTINUE
INTO THE MID-MORNING HOURS BEFORE TAKING A BIT OF A BREAK LATER THIS
MORNING/EARLY THIS AFTERNOON AS SLIGHTLY DRIER AIR MOVES IN FROM THE
SOUTH. A SECOND ROUND OF CONVECTIVE ACTIVITY IS LIKELY LATER THIS
AFTERNOON INTO THIS EVENING AS THE MAIN UPPER LOW CENTER PASSES
OVER THE REGION. THE MAIN IMPACTS FROM THE STRONGER STORMS WILL BE
TO PRODUCE GUSTY WINDS AND BRIEF HEAVY RAINS...UP TO AROUND 1/2 INCH
AS THEY PASS OVER A SPECIFIC LOCATION. A GRADUAL CLEARING/DRYING
TREND IS THEN EXPECTED FROM LATE TONIGHT INTO TUESDAY AS THE UPPER
LOW LIFTS OUT TO THE NORTHEAST. THIS COMBINATION OF COOLER AIR ALOFT
AND CONSIDERABLE CLOUDINESS/SHOWERS WILL KEEP LOWER DESERT HIGHS IN
THE 80S TODAY AND TUESDAY...ABOUT 3-6 DEGREES BELOW NORMAL FOR THIS
TIME OF YEAR.

WEDNESDAY...WEAK RIDGING AHEAD OF THE NEXT MAJOR TROF TO PRODUCE DRY
CONDITIONS...MOSTLY CLEAR SKIES...AND SLIGHTLY WARMER TEMPERATURES.

THURSDAY THROUGH SATURDAY...GLOBAL MODELS CONTINUE TO MOVE ANOTHER
COOL TROF TO OUR NORTH...ACROSS THE GREAT BASIN...WITH VERY GOOD
INTERMODEL AND RUN-TO-RUN AGREEMENT ON THE DETAILS OF THIS SYSTEM.
THE MAIN IMPACTS FROM THIS SECOND SYSTEM WILL TO BRING EVEN COOLER
TEMPS INTO THE REGION...UP TO 10 DEGREES BELOW NORMAL ON
FRIDAY...AS THE UPPER LOW PASSES CLOSEST TO OUR CWA...AND STRONG
WESTERLY WINDS...WITH GUSTS UP TO 30 MPH. THE COMBINATION OF THESE
STRONG WINDS AND A RATHER DRY AIRMASS WILL LIKELY RAISE FIRE DANGER
LEVELS ACROSS THE REGION...ESPECIALLY ACROSS SW AZ...THE LOWER
COLORADO RIVER VALLEY...AND SE CA.

SUNDAY AND MONDAY...A WARMING TREND IS LIKELY DURING THIS PERIOD AS
RIDGING ALOFT ATTEMPTS TO BUILD NORTHWARD INTO THE DESERT SW...WITH
HIGHS LIKELY TO RISE TO NEAR NORMAL BY MONDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...PERCHA
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 040227
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
727 PM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION...RESULTING IN A COOLING TREND. A LARGE AND
COLDER DISTURBANCE IS FORECAST TO MOVE INTO THE REGION EARLY MONDAY
MORNING THROUGH TUESDAY...FOR AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS...MAINLY ACROSS ARIZONA. CLEARING IS EXPECTED LATE
TUESDAY THROUGH THE REMAINDER OF THE WEEK AND NEXT WEEKEND...HOWEVER
WITH SEVERAL PACIFIC WEATHER SYSTEMS FORECAST TO MOVE INTO THE
WESTERN STATES NORTH OF ARIZONA THIS WEEK...BELOW NORMAL TEMPERATURES
ARE EXPECTED THE NEXT SEVEN DAYS.

&&

.DISCUSSION...
ISOLATED SHOWERS CONTINUE TO PERCOLATE ACROSS PORTIONS OF WESTERN
MARICOPA COUNTY AND CENTRAL PINAL COUNTY. UNLIKE YESTERDAY...DUST
PROBLEMS HAVE BEEN FEW AND FAR BETWEEN THIS EVENING AS STORMS HAVE
STRUGGLED TO MAINTAIN CORES ABOVE 20-25KFT. NONETHELESS A FEW SPOTS
SOUTHWEST OF THE METRO MANAGED TO SQUEEZE OUT A FEW HUNDREDTHS OF AN
INCH OF RAINFALL SINCE 00Z.

TAKING A LOOK AT INCOMING 00Z NAM...21Z SREF...AND THE LAST 5-6 RUNS
OF THE HRRR...ALL GUIDANCE IS POINTING TOWARD THE DEVELOPMENT OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS AFTER MIDNIGHT WITH
MEASURABLE PRECIP ACROSS THE PHOENIX AREA BEFORE DAYBREAK.
APPROXIMATELY HALF OF THE 21Z SREF MEMBERS INDICATE MEASURABLE PRECIP
AT KPHX AROUND 09Z AND I FELT IT PRUDENT TO ADJUST THE FORECAST IN
THAT DIRECTION. MAKING SOME UPWARD ADJUSTMENTS TO THE POPS AFTER 06Z
AND ACCELERATING THE ONSET OF RAIN ACROSS THE AREA. WHILE AMOUNTS
WILL BE LIGHT /FEW HUNDREDTHS/...IT SHOULD NONETHELESS MAKE FOR A
DAMP MONDAY MORNING COMMUTE.

THE REMAINDER OF THE INHERITED FORECAST GRIDS ARE IN GOOD
SHAPE...WILL MAKE MINOR ADJUSTMENTS TO TEMPS/DEWPOINTS/WINDS BASED ON
OBSERVATIONAL TRENDS BUT NOTHING SIGNIFICANT.

&&

.PREVIOUS DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR MONDAY AND TUESDAY A MAJOR COOL PACIFIC TROF IS STILL ON TRACK
TO MOVE FORECAST TO MOVE INTO SOUTHERN CA TONIGHT THEN INTO AZ MONDAY
MORNING THROUGH TUESDAY MORNING. THIS IS A MUCH COLDER TROF WITH WITH
SOMEWHAT STRONG UPPER LEVEL DYNAMICS...AND...WITH INCREASED BOUNDARY
LAYER MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING
TROF...THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO
EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY SKIES ARE EXPECTED WITH NO PRECIP AS A
MINOR SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY THROUGH SATURDAY...ANOTHER COOL TROF IS FORECAST TO MOVE
INTO THE WESTERN REGION MAINLY NORTH OF OUR FORECAST AREA. PRECIP
CHANCES SHOULD MOSTLY BE CONFINED TO OUR SOUTHEAST CA JOSHUA TREE
ZONE 30. HOWEVER...STRONG 500-300 MB HEIGHT FALLS OVER THE MOHAVE
DESERT OF CA FRIDAY SUGGESTS VERY STRONG GUSTY WEST WINDS ACROSS
MUCH OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY.


&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 040227
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
727 PM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION...RESULTING IN A COOLING TREND. A LARGE AND
COLDER DISTURBANCE IS FORECAST TO MOVE INTO THE REGION EARLY MONDAY
MORNING THROUGH TUESDAY...FOR AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS...MAINLY ACROSS ARIZONA. CLEARING IS EXPECTED LATE
TUESDAY THROUGH THE REMAINDER OF THE WEEK AND NEXT WEEKEND...HOWEVER
WITH SEVERAL PACIFIC WEATHER SYSTEMS FORECAST TO MOVE INTO THE
WESTERN STATES NORTH OF ARIZONA THIS WEEK...BELOW NORMAL TEMPERATURES
ARE EXPECTED THE NEXT SEVEN DAYS.

&&

.DISCUSSION...
ISOLATED SHOWERS CONTINUE TO PERCOLATE ACROSS PORTIONS OF WESTERN
MARICOPA COUNTY AND CENTRAL PINAL COUNTY. UNLIKE YESTERDAY...DUST
PROBLEMS HAVE BEEN FEW AND FAR BETWEEN THIS EVENING AS STORMS HAVE
STRUGGLED TO MAINTAIN CORES ABOVE 20-25KFT. NONETHELESS A FEW SPOTS
SOUTHWEST OF THE METRO MANAGED TO SQUEEZE OUT A FEW HUNDREDTHS OF AN
INCH OF RAINFALL SINCE 00Z.

TAKING A LOOK AT INCOMING 00Z NAM...21Z SREF...AND THE LAST 5-6 RUNS
OF THE HRRR...ALL GUIDANCE IS POINTING TOWARD THE DEVELOPMENT OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS AFTER MIDNIGHT WITH
MEASURABLE PRECIP ACROSS THE PHOENIX AREA BEFORE DAYBREAK.
APPROXIMATELY HALF OF THE 21Z SREF MEMBERS INDICATE MEASURABLE PRECIP
AT KPHX AROUND 09Z AND I FELT IT PRUDENT TO ADJUST THE FORECAST IN
THAT DIRECTION. MAKING SOME UPWARD ADJUSTMENTS TO THE POPS AFTER 06Z
AND ACCELERATING THE ONSET OF RAIN ACROSS THE AREA. WHILE AMOUNTS
WILL BE LIGHT /FEW HUNDREDTHS/...IT SHOULD NONETHELESS MAKE FOR A
DAMP MONDAY MORNING COMMUTE.

THE REMAINDER OF THE INHERITED FORECAST GRIDS ARE IN GOOD
SHAPE...WILL MAKE MINOR ADJUSTMENTS TO TEMPS/DEWPOINTS/WINDS BASED ON
OBSERVATIONAL TRENDS BUT NOTHING SIGNIFICANT.

&&

.PREVIOUS DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR MONDAY AND TUESDAY A MAJOR COOL PACIFIC TROF IS STILL ON TRACK
TO MOVE FORECAST TO MOVE INTO SOUTHERN CA TONIGHT THEN INTO AZ MONDAY
MORNING THROUGH TUESDAY MORNING. THIS IS A MUCH COLDER TROF WITH WITH
SOMEWHAT STRONG UPPER LEVEL DYNAMICS...AND...WITH INCREASED BOUNDARY
LAYER MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING
TROF...THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO
EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY SKIES ARE EXPECTED WITH NO PRECIP AS A
MINOR SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY THROUGH SATURDAY...ANOTHER COOL TROF IS FORECAST TO MOVE
INTO THE WESTERN REGION MAINLY NORTH OF OUR FORECAST AREA. PRECIP
CHANCES SHOULD MOSTLY BE CONFINED TO OUR SOUTHEAST CA JOSHUA TREE
ZONE 30. HOWEVER...STRONG 500-300 MB HEIGHT FALLS OVER THE MOHAVE
DESERT OF CA FRIDAY SUGGESTS VERY STRONG GUSTY WEST WINDS ACROSS
MUCH OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY.


&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA




000
FXUS65 KPSR 040227
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
727 PM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION...RESULTING IN A COOLING TREND. A LARGE AND
COLDER DISTURBANCE IS FORECAST TO MOVE INTO THE REGION EARLY MONDAY
MORNING THROUGH TUESDAY...FOR AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS...MAINLY ACROSS ARIZONA. CLEARING IS EXPECTED LATE
TUESDAY THROUGH THE REMAINDER OF THE WEEK AND NEXT WEEKEND...HOWEVER
WITH SEVERAL PACIFIC WEATHER SYSTEMS FORECAST TO MOVE INTO THE
WESTERN STATES NORTH OF ARIZONA THIS WEEK...BELOW NORMAL TEMPERATURES
ARE EXPECTED THE NEXT SEVEN DAYS.

&&

.DISCUSSION...
ISOLATED SHOWERS CONTINUE TO PERCOLATE ACROSS PORTIONS OF WESTERN
MARICOPA COUNTY AND CENTRAL PINAL COUNTY. UNLIKE YESTERDAY...DUST
PROBLEMS HAVE BEEN FEW AND FAR BETWEEN THIS EVENING AS STORMS HAVE
STRUGGLED TO MAINTAIN CORES ABOVE 20-25KFT. NONETHELESS A FEW SPOTS
SOUTHWEST OF THE METRO MANAGED TO SQUEEZE OUT A FEW HUNDREDTHS OF AN
INCH OF RAINFALL SINCE 00Z.

TAKING A LOOK AT INCOMING 00Z NAM...21Z SREF...AND THE LAST 5-6 RUNS
OF THE HRRR...ALL GUIDANCE IS POINTING TOWARD THE DEVELOPMENT OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS AFTER MIDNIGHT WITH
MEASURABLE PRECIP ACROSS THE PHOENIX AREA BEFORE DAYBREAK.
APPROXIMATELY HALF OF THE 21Z SREF MEMBERS INDICATE MEASURABLE PRECIP
AT KPHX AROUND 09Z AND I FELT IT PRUDENT TO ADJUST THE FORECAST IN
THAT DIRECTION. MAKING SOME UPWARD ADJUSTMENTS TO THE POPS AFTER 06Z
AND ACCELERATING THE ONSET OF RAIN ACROSS THE AREA. WHILE AMOUNTS
WILL BE LIGHT /FEW HUNDREDTHS/...IT SHOULD NONETHELESS MAKE FOR A
DAMP MONDAY MORNING COMMUTE.

THE REMAINDER OF THE INHERITED FORECAST GRIDS ARE IN GOOD
SHAPE...WILL MAKE MINOR ADJUSTMENTS TO TEMPS/DEWPOINTS/WINDS BASED ON
OBSERVATIONAL TRENDS BUT NOTHING SIGNIFICANT.

&&

.PREVIOUS DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR MONDAY AND TUESDAY A MAJOR COOL PACIFIC TROF IS STILL ON TRACK
TO MOVE FORECAST TO MOVE INTO SOUTHERN CA TONIGHT THEN INTO AZ MONDAY
MORNING THROUGH TUESDAY MORNING. THIS IS A MUCH COLDER TROF WITH WITH
SOMEWHAT STRONG UPPER LEVEL DYNAMICS...AND...WITH INCREASED BOUNDARY
LAYER MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING
TROF...THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO
EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY SKIES ARE EXPECTED WITH NO PRECIP AS A
MINOR SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY THROUGH SATURDAY...ANOTHER COOL TROF IS FORECAST TO MOVE
INTO THE WESTERN REGION MAINLY NORTH OF OUR FORECAST AREA. PRECIP
CHANCES SHOULD MOSTLY BE CONFINED TO OUR SOUTHEAST CA JOSHUA TREE
ZONE 30. HOWEVER...STRONG 500-300 MB HEIGHT FALLS OVER THE MOHAVE
DESERT OF CA FRIDAY SUGGESTS VERY STRONG GUSTY WEST WINDS ACROSS
MUCH OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY.


&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA




000
FXUS65 KPSR 040227
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
727 PM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION...RESULTING IN A COOLING TREND. A LARGE AND
COLDER DISTURBANCE IS FORECAST TO MOVE INTO THE REGION EARLY MONDAY
MORNING THROUGH TUESDAY...FOR AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS...MAINLY ACROSS ARIZONA. CLEARING IS EXPECTED LATE
TUESDAY THROUGH THE REMAINDER OF THE WEEK AND NEXT WEEKEND...HOWEVER
WITH SEVERAL PACIFIC WEATHER SYSTEMS FORECAST TO MOVE INTO THE
WESTERN STATES NORTH OF ARIZONA THIS WEEK...BELOW NORMAL TEMPERATURES
ARE EXPECTED THE NEXT SEVEN DAYS.

&&

.DISCUSSION...
ISOLATED SHOWERS CONTINUE TO PERCOLATE ACROSS PORTIONS OF WESTERN
MARICOPA COUNTY AND CENTRAL PINAL COUNTY. UNLIKE YESTERDAY...DUST
PROBLEMS HAVE BEEN FEW AND FAR BETWEEN THIS EVENING AS STORMS HAVE
STRUGGLED TO MAINTAIN CORES ABOVE 20-25KFT. NONETHELESS A FEW SPOTS
SOUTHWEST OF THE METRO MANAGED TO SQUEEZE OUT A FEW HUNDREDTHS OF AN
INCH OF RAINFALL SINCE 00Z.

TAKING A LOOK AT INCOMING 00Z NAM...21Z SREF...AND THE LAST 5-6 RUNS
OF THE HRRR...ALL GUIDANCE IS POINTING TOWARD THE DEVELOPMENT OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS AFTER MIDNIGHT WITH
MEASURABLE PRECIP ACROSS THE PHOENIX AREA BEFORE DAYBREAK.
APPROXIMATELY HALF OF THE 21Z SREF MEMBERS INDICATE MEASURABLE PRECIP
AT KPHX AROUND 09Z AND I FELT IT PRUDENT TO ADJUST THE FORECAST IN
THAT DIRECTION. MAKING SOME UPWARD ADJUSTMENTS TO THE POPS AFTER 06Z
AND ACCELERATING THE ONSET OF RAIN ACROSS THE AREA. WHILE AMOUNTS
WILL BE LIGHT /FEW HUNDREDTHS/...IT SHOULD NONETHELESS MAKE FOR A
DAMP MONDAY MORNING COMMUTE.

THE REMAINDER OF THE INHERITED FORECAST GRIDS ARE IN GOOD
SHAPE...WILL MAKE MINOR ADJUSTMENTS TO TEMPS/DEWPOINTS/WINDS BASED ON
OBSERVATIONAL TRENDS BUT NOTHING SIGNIFICANT.

&&

.PREVIOUS DISCUSSION...
MONDAY THROUGH TUESDAY...
FOR MONDAY AND TUESDAY A MAJOR COOL PACIFIC TROF IS STILL ON TRACK
TO MOVE FORECAST TO MOVE INTO SOUTHERN CA TONIGHT THEN INTO AZ MONDAY
MORNING THROUGH TUESDAY MORNING. THIS IS A MUCH COLDER TROF WITH WITH
SOMEWHAT STRONG UPPER LEVEL DYNAMICS...AND...WITH INCREASED BOUNDARY
LAYER MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND
THUNDERSTORMS AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING
TROF...THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO
EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY SKIES ARE EXPECTED WITH NO PRECIP AS A
MINOR SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY THROUGH SATURDAY...ANOTHER COOL TROF IS FORECAST TO MOVE
INTO THE WESTERN REGION MAINLY NORTH OF OUR FORECAST AREA. PRECIP
CHANCES SHOULD MOSTLY BE CONFINED TO OUR SOUTHEAST CA JOSHUA TREE
ZONE 30. HOWEVER...STRONG 500-300 MB HEIGHT FALLS OVER THE MOHAVE
DESERT OF CA FRIDAY SUGGESTS VERY STRONG GUSTY WEST WINDS ACROSS
MUCH OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY.


&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SHOWERS HAVE AVOIDED THE PHOENIX TERMINALS SO FAR THIS EVENING...BUT
WILL BECOME MORE SCATTERED IN NATURE AROUND 09Z WITH SEVERAL HOURS OF
-SHRA EXPECTED AT ALL 3 PHOENIX TAF SITES. EXPECTING CIGS TO LOWER TO
AROUND 4-6KFT /WILL VARY BASED ON INTENSITY OF PASSING SHOWERS/
THROUGH APPROX 15Z...THEN IMPROVE FOR A BIT INTO THE EARLY AFTERNOON
HOURS. EXPECTING ANOTHER ROUND OF ISOLATED/SCATTERED LATE-DAY -SHRA
AFTER 22Z BUT AT THIS POINT WILL ONLY MENTION VCSH AS CONFIDENCE IN
AREAL COVERAGE IS LOW. AS FOR WINDS...SHOULD SEE A PERSISTENT
WESTERLY DIRECTION AT KPHX OVERNIGHT ALTHOUGH KIWA MAY TRY AND TAKE
ITS USUAL TURN OUT OF THE SOUTHEAST AFTER MIDNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NOT EXPECTING ANY SHOWERS TO IMPACT EITHER KIPL OR KBLH. MOST LIKELY
IMPACT FROM THE APPROACHING TROUGH WILL BE IN THE FORM OF BLOWOFF
CIRRUS AND BREEZY AFTERNOON WINDS. OTHERWISE...WEATHER IMPACTS SHOULD
BE CONFINED TO AREAS EAST OF THE CO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY
AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 032204
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
305 PM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION...RESULTING IN A COOLING TREND. A LARGE AND
COLDER DISTURBANCE IS FORECAST TO MOVE INTO THE REGION LATE TONIGHT
THROUGH TUESDAY...FOR AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS...MAINLY ACROSS ARIZONA. CLEARING IS EXPECTED LATE
TUESDAY THROUGH THE REMAINDER OF THE WEEK AND NEXT WEEKEND...HOWEVER
WITH SEVERAL PACIFIC WEATHER SYSTEMS FORECAST TO MOVE INTO THE
WESTERN STATES NORTH OF ARIZONA THIS WEEK...BELOW NORMAL
TEMPERATURES ARE EXPECTED THE NEXT SEVEN DAYS.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...MINIMAL CONVECTIVE ACTIVITY WAS NOTED SO
FAR AT 2 PM MST ACROSS OUR FORECAST AREA AS UPPER LEVEL CONVERGENCE
HAS STABILIZED MOST OF SOUTHERN AZ. ALSO NOTED FROM VISIBLE
SATELLITE IMAGERY WAS THE LONG FETCH OF CLOUD STREETS EXTENDING INTO
SOUTHERN AZ FROM MEXICO/GULF OF CA. PRECIP WATER (PW) IMAGERY ALSO
SHOWED PW AMOUNTS HAD INCREASED ACROSS THE ENTIRE GULF OF CA
SUGGESTING CONTINUED MOISTURE ADVECTION THE REMAINDER OF TODAY AND
TONIGHT AHEAD OF MONDAYS ANTICIPATED TROF.

FOR MONDAY AND TUESDAY A MAJOR COOL PACIFIC TROF IS STILL ON TRACK
TO MOVE FORECAST TO MOVE INTO SOUTHERN CA TONIGHT THEN INTO AZ
MONDAY MORNING THROUGH TUESDAY MORNING. THIS IS A MUCH COLDER TROF
WITH WITH SOMEWHAT STRONG UPPER LEVEL DYNAMICS...AND...WITH
INCREASED BOUNDARY LAYER MOISTURE WILL LEAD TO A GOOD CHANCE OF
SHOWERS AND THUNDERSTORMS AREA-WIDE. SINCE IT WILL BE A SLOW
EASTWARD MOVING TROF...THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL
CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY SKIES ARE EXPECTED WITH NO PRECIP AS A
MINOR SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY THROUGH SATURDAY...ANOTHER COOL TROF IS FORECAST TO MOVE
INTO THE WESTERN REGION MAINLY NORTH OF OUR FORECAST AREA. PRECIP
CHANCES SHOULD MOSTLY BE CONFINED TO OUR SOUTHEAST CA JOSHUA TREE
ZONE 30. HOWEVER...STRONG 500-300 MB HEIGHT FALLS OVER THE MOHAVE
DESERT OF CA FRIDAY SUGGESTS VERY STRONG GUSTY WEST WINDS ACROSS
MUCH OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY.


&&

.AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND
KSDL...

MORE STABLE ATMOSPHERIC SET-UP TODAY WILL PROVIDE A BRIEF BREAK IN
BETWEEN THE PRECIP ACTIVITY OVER THE SOUTH-CENTRAL AZ DESERTS. FEW-
SCT CU FIELDS AOA 10-12KFT WILL LINGER UNTIL AFTER SUNSET THEN
GRADUALLY CLEAR OFF. AFTN WINDS TO WORK THEIR WAY INTO SW-W HEADINGS
WITH SPEEDS 10-15KTS AT THEIR PEAK. MOISTURE SURGE FROM THE
SOUTHWEST WILL BE ACCOMPANIED BY ELEVATED WINDS JUST ABOVE THE SFC
THAT MAY CREATE PERIODS OF LLWS CONDITIONS. UNCERTAINTY REMAINS IF
SFC WINDS WILL CALM OUT ENOUGH FOR IT TO BE A SIGNIFICANT IMPACT IN
TERMS OF SPEED DIFFERENTIAL...25 TO 30 KTS OR SO. PRECIP ACTIVITY
WILL BE POSSIBLE EARLY IN THE AM...WITH AT LEAST VCSH COVERAGE FOR
THE PHX TERMINALS BY 12Z. CIGS TO GRADUALLY LOWER DOWN TOWARDS 4-
6KFT INTO MONDAY AM.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH... FEW TO SCT CUMULUS FIELDS OVER THE TERMINALS THROUGH SUNSET
THEN MID LEVEL CLOUDS TO GIVE WAY TO PASSING HIGH LEVEL CLOUDS GNLY
AOA 20KFT. ELEVATED S-SE WINDS TO PERSIST OVERNIGHT ALONG THE CO
RIVER VALLEY AND KBLH WHILE WESTERLY WINDS FOR KIPL WILL CONTINUE
THROUGH EARLY EVENING. ANY PRECIP ACTIVITY OVERNIGHT AND INTO MONDAY
SHOULD STAY EAST OF THE TERMINALS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER... WEDNESDAY THROUGH SUNDAY... DRY WEATHER...AND
SLIGHTLY WARMER TEMPERATURES TO RETURN WEDNESDAY AS WEAK HIGH
PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER TEMPERATURES
TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO SATURDAY AS
ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT BASIN. FIRE
DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD AS
AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ AVIATION...NOLTE/PERCHA FIRE WEATHER...PERCHA





000
FXUS65 KPSR 031554
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
850 AM MST SUN MAY 3 2015

.SYNOPSIS... A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION... SKIES WERE MOSTLY CLEAR ACROSS OUR FORECAST AREA...
WITH THE EXCEPTION OF SOUTHERN GILA COUNTY WHERE MOSTLY CLOUDY SKIES
WERE NOTED. CLOUDS IN SOUTHERN GILA COUNTY WERE REMNANTS OF
CONVECTIVE DEBRIS CLOUDS AND ISOLATED THUNDERSTORMS THAT DEVELOP
NEAR WICKENBURG AND NORTH OF CAREFREE/CAVE CREEK BETWEEN MIDNIGHT
AND 2 AM.

PERUSING THE UPPER AIR DATA SHOWED THE ATMOSPHERE OVER TUCSON IN
TERMS OF PRECIP WATER CHANGED LITTLE SINCE YESTERDAY AM... HOWEVER
NOW ITS ALL IN THE BOUNDARY LAYER. IN FACT...THE BOUNDARY LAYER HAS
BECOME MORE MOIST ACROSS ALL OF SOUTH CENTRAL AND SOUTHEAST AZ THIS
MORNING. AND...IT WAS ALSO NOTED THAT 300/250 MB FLOW ACROSS ALL OF
AZ WAS SOUTHWESTERLY AND DIFLUENT...MEANING THE ATMOSPHERE IS
UNWEIGHTING OR WITH DECREASING STATIC STABILITY AT TIMES. A CAVEAT
THOUGH...AND ITS A BIG ONE...MODELS FORECAST THE STRONGEST WINDS
ALOFT OR JET MAX AT 300/250 MB TO SHIFT NORTH FROM NORTHWEST MEX
INTO SOUTHERN AZ LATER THIS AFTERNOON AND BECOME ANTI-CYCLONIC. THIS
SHOULD INCREASE STATIC STABILITY AND REDUCE THE CHANCE OF AFTN/EVE
TSTMS DESPITE THE INCREASE IN BOUNDARY LAYER MOISTURE AND
THERMODYNAMIC INSTABILITY. FINGERS CROSS. THEREFORE TODAYS FORECASTS
LOOK OK WITH THE BEST CHANCE OF AFTN SHWRS AND TSTMS EXPECTED IN THE
MOUNTAINS OF SOUTHERN GILA COUNTY FOR TODAY.  WE WENT AHEAD AND MADE
A FEW TWEAKS TO THE SOUTHERN GILA COUNTY FORECASTS BY INCREASING
POPS SLIGHTLY FOR TODAY.

OTHERWISE REMAINDER OF FORECASTS FOR EARLY THIS WEEK...MON AND TUE
LOOK GOOD AS A FAIRLY DYNAMICAL PACIFIC LOW PRESSURE SYSTEM IS
FORECAST TO SLOWLY ADVANCE THROUGH THE REGION MONDAY MORNING THROUGH
TUESDAY MORNING. PREVIOUS DISCUSSION BELOW STILL APPLIES.


...PREVIOUS DISCUSSION...320 AM MST...

WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN BAJA LED TO A FEW
AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE SOUTHERN AZ DESERTS
YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED LEAVING BEHIND
VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE SOUTHWEST FLOW ALOFT
OVER THE AREA SPREAD INCREASING AMOUNTS OF MOISTURE INTO THE
AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z SOUNDING...AND
SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS WELL. ACROSS SERN
CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE PAST 24 HOURS AND
WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS HAVE SEEN
READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM. THE
PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE NORTHEAST
EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR SOUTHWEST FLOW.
STILL...WITH THE INCREASED MOISTURE AND INSTABILITY THERE WILL
LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS ACROSS THE
HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS POSSIBLE THAT A
STRAY HIGH BASED STORM COULD DEVELOP OVER THE CENTRAL DESERTS AS
WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR COMPARED TO THE BIG
CHANGE IN THE WEATHER SLATED TO ARRIVE MONDAY...AND CONTINUE THROUGH
TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO KEEP THIS
AFTERNOON/S CROP OF THUNDERSHOWERS NORTH AND EAST OF THE
TERMINALS...LEAVING SCT-BKN MID-HIGH CLOUD LAYERS FOR THE TERMINALS
THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE EXPECTED TO REMAIN P6SM
LEFTOVER DUST FROM SATURDAY/S THUNDERSTORMS COULD AFFECT SLANTWISE
VSBYS FOR INBOUND AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS.
WINDS ARE EXPECTED TO FOLLOW TYPICAL DIURNAL TRENDS WITH WESTERLY
BREEZES PREVAILING THROUGH THE AFTERNOON AND EARLY EVENING HOURS.
FCST GUIDANCE INDICATES ELEVATED WEST WINDS MAY PERSIST OVERNIGHT AT
THE SFC WHILE INCREASING IN SPEED JUST OFF THE SFC IN RESPONSE TO AN
APPROACHING PACIFIC LOW. IF THE PHX AREA IS ABLE TO STAY MIXED
OVERNIGHT AND NOT DECOUPLE... THESE WINDS SHOULD NOT IMPACT TYPICAL
FLIGHT OPS. WILL TAKE A CLOSER LOOK AT THIS MORNING MODEL RUNS TO
SEE IF ANY LLWS MENTION IS WARRANTED OVERNIGHT AT ANY OF THE
TERMINALS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH...
ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND KBLH...WITH
JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-TIME.
SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER AZ ON
SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY FOLLOW
TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO SOUTHEASTERLY WINDS
DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A PACIFIC STORM THAT WILL BE AFFECTING THE DESERT SW EARLY IN THE
UPCOMING WORKWEEK WILL BRING A DECENT CHANCE FOR
SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON TUESDAY...ESPECIALLY
OVER THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX...WITH
TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES. DRY
WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON WEDNESDAY AS
WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ/CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 031554
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
850 AM MST SUN MAY 3 2015

.SYNOPSIS... A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION... SKIES WERE MOSTLY CLEAR ACROSS OUR FORECAST AREA...
WITH THE EXCEPTION OF SOUTHERN GILA COUNTY WHERE MOSTLY CLOUDY SKIES
WERE NOTED. CLOUDS IN SOUTHERN GILA COUNTY WERE REMNANTS OF
CONVECTIVE DEBRIS CLOUDS AND ISOLATED THUNDERSTORMS THAT DEVELOP
NEAR WICKENBURG AND NORTH OF CAREFREE/CAVE CREEK BETWEEN MIDNIGHT
AND 2 AM.

PERUSING THE UPPER AIR DATA SHOWED THE ATMOSPHERE OVER TUCSON IN
TERMS OF PRECIP WATER CHANGED LITTLE SINCE YESTERDAY AM... HOWEVER
NOW ITS ALL IN THE BOUNDARY LAYER. IN FACT...THE BOUNDARY LAYER HAS
BECOME MORE MOIST ACROSS ALL OF SOUTH CENTRAL AND SOUTHEAST AZ THIS
MORNING. AND...IT WAS ALSO NOTED THAT 300/250 MB FLOW ACROSS ALL OF
AZ WAS SOUTHWESTERLY AND DIFLUENT...MEANING THE ATMOSPHERE IS
UNWEIGHTING OR WITH DECREASING STATIC STABILITY AT TIMES. A CAVEAT
THOUGH...AND ITS A BIG ONE...MODELS FORECAST THE STRONGEST WINDS
ALOFT OR JET MAX AT 300/250 MB TO SHIFT NORTH FROM NORTHWEST MEX
INTO SOUTHERN AZ LATER THIS AFTERNOON AND BECOME ANTI-CYCLONIC. THIS
SHOULD INCREASE STATIC STABILITY AND REDUCE THE CHANCE OF AFTN/EVE
TSTMS DESPITE THE INCREASE IN BOUNDARY LAYER MOISTURE AND
THERMODYNAMIC INSTABILITY. FINGERS CROSS. THEREFORE TODAYS FORECASTS
LOOK OK WITH THE BEST CHANCE OF AFTN SHWRS AND TSTMS EXPECTED IN THE
MOUNTAINS OF SOUTHERN GILA COUNTY FOR TODAY.  WE WENT AHEAD AND MADE
A FEW TWEAKS TO THE SOUTHERN GILA COUNTY FORECASTS BY INCREASING
POPS SLIGHTLY FOR TODAY.

OTHERWISE REMAINDER OF FORECASTS FOR EARLY THIS WEEK...MON AND TUE
LOOK GOOD AS A FAIRLY DYNAMICAL PACIFIC LOW PRESSURE SYSTEM IS
FORECAST TO SLOWLY ADVANCE THROUGH THE REGION MONDAY MORNING THROUGH
TUESDAY MORNING. PREVIOUS DISCUSSION BELOW STILL APPLIES.


...PREVIOUS DISCUSSION...320 AM MST...

WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN BAJA LED TO A FEW
AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE SOUTHERN AZ DESERTS
YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED LEAVING BEHIND
VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE SOUTHWEST FLOW ALOFT
OVER THE AREA SPREAD INCREASING AMOUNTS OF MOISTURE INTO THE
AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z SOUNDING...AND
SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS WELL. ACROSS SERN
CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE PAST 24 HOURS AND
WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS HAVE SEEN
READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM. THE
PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE NORTHEAST
EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR SOUTHWEST FLOW.
STILL...WITH THE INCREASED MOISTURE AND INSTABILITY THERE WILL
LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS ACROSS THE
HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS POSSIBLE THAT A
STRAY HIGH BASED STORM COULD DEVELOP OVER THE CENTRAL DESERTS AS
WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR COMPARED TO THE BIG
CHANGE IN THE WEATHER SLATED TO ARRIVE MONDAY...AND CONTINUE THROUGH
TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO KEEP THIS
AFTERNOON/S CROP OF THUNDERSHOWERS NORTH AND EAST OF THE
TERMINALS...LEAVING SCT-BKN MID-HIGH CLOUD LAYERS FOR THE TERMINALS
THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE EXPECTED TO REMAIN P6SM
LEFTOVER DUST FROM SATURDAY/S THUNDERSTORMS COULD AFFECT SLANTWISE
VSBYS FOR INBOUND AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS.
WINDS ARE EXPECTED TO FOLLOW TYPICAL DIURNAL TRENDS WITH WESTERLY
BREEZES PREVAILING THROUGH THE AFTERNOON AND EARLY EVENING HOURS.
FCST GUIDANCE INDICATES ELEVATED WEST WINDS MAY PERSIST OVERNIGHT AT
THE SFC WHILE INCREASING IN SPEED JUST OFF THE SFC IN RESPONSE TO AN
APPROACHING PACIFIC LOW. IF THE PHX AREA IS ABLE TO STAY MIXED
OVERNIGHT AND NOT DECOUPLE... THESE WINDS SHOULD NOT IMPACT TYPICAL
FLIGHT OPS. WILL TAKE A CLOSER LOOK AT THIS MORNING MODEL RUNS TO
SEE IF ANY LLWS MENTION IS WARRANTED OVERNIGHT AT ANY OF THE
TERMINALS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH...
ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND KBLH...WITH
JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-TIME.
SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER AZ ON
SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY FOLLOW
TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO SOUTHEASTERLY WINDS
DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A PACIFIC STORM THAT WILL BE AFFECTING THE DESERT SW EARLY IN THE
UPCOMING WORKWEEK WILL BRING A DECENT CHANCE FOR
SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON TUESDAY...ESPECIALLY
OVER THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX...WITH
TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES. DRY
WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON WEDNESDAY AS
WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ/CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 031429 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE PHOENIX AZ
728 AM MST SUN MAY 3 2015

.UPDATE...AND MINOR CORRECTION TO AVIATION DISCUSSION...

&&

.SYNOPSIS...
A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO MOVE INTO
THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND. ENOUGH
MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND EARLY
EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND EASTERN
ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS FORECAST TO
MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD CHANCE OF SHOWERS
AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION...
WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN BAJA LED TO A FEW
AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE SOUTHERN AZ DESERTS
YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED LEAVING BEHIND
VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE SOUTHWEST FLOW ALOFT
OVER THE AREA SPREAD INCREASING AMOUNTS OF MOISTURE INTO THE
AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z SOUNDING...AND
SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS WELL. ACROSS SERN
CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE PAST 24 HOURS AND
WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS HAVE SEEN
READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM. THE
PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE NORTHEAST
EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR SOUTHWEST FLOW.
STILL...WITH THE INCREASED MOISTURE AND INSTABILITY THERE WILL
LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS ACROSS THE
HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS POSSIBLE THAT A
STRAY HIGH BASED STORM COULD DEVELOP OVER THE CENTRAL DESERTS AS
WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR COMPARED TO THE BIG
CHANGE IN THE WEATHER SLATED TO ARRIVE MONDAY...AND CONTINUE THROUGH
TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO KEEP THIS
AFTERNOON/S CROP OF THUNDERSHOWERS NORTH AND EAST OF THE
TERMINALS...LEAVING SCT-BKN MID-HIGH CLOUD LAYERS FOR THE TERMINALS
THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE EXPECTED TO REMAIN P6SM
LEFTOVER DUST FROM SATURDAY/S THUNDERSTORMS COULD AFFECT SLANTWISE
VSBYS FOR INBOUND AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS.
WINDS ARE EXPECTED TO FOLLOW TYPICAL DIURNAL TRENDS WITH WESTERLY
BREEZES PREVAILING THROUGH THE AFTERNOON AND EARLY EVENING HOURS.
FCST GUIDANCE INDICATES ELEVATED WEST WINDS MAY PERSIST OVERNIGHT AT
THE SFC WHILE INCREASING IN SPEED JUST OFF THE SFC IN RESPONSE TO AN
APPROACHING PACIFIC LOW. IF THE PHX AREA IS ABLE TO STAY MIXED
OVERNIGHT AND NOT DECOUPLE... THESE WINDS SHOULD NOT IMPACT TYPICAL
FLIGHT OPS. WILL TAKE A CLOSER LOOK AT THIS MORNING MODEL RUNS TO
SEE IF ANY LLWS MENTION IS WARRANTED OVERNIGHT AT ANY OF THE
TERMINALS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH...
ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND KBLH...WITH
JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-TIME.
SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER AZ ON
SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY FOLLOW
TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO SOUTHEASTERLY WINDS
DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A PACIFIC STORM THAT WILL BE AFFECTING THE DESERT SW EARLY IN THE
UPCOMING WORKWEEK WILL BRING A DECENT CHANCE FOR
SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON TUESDAY...ESPECIALLY
OVER THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX...WITH
TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES. DRY
WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON WEDNESDAY AS
WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS AND COOLER
TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY ONWARD INTO
SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS THE GREAT
BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING THIS PERIOD
AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY WARMER
TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 031022
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
320 AM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION... WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN
BAJA LED TO A FEW AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE
SOUTHERN AZ DESERTS YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED
LEAVING BEHIND VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE
SOUTHWEST FLOW ALOFT OVER THE AREA SPREAD INCREASING AMOUNTS OF
MOISTURE INTO THE AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z
SOUNDING...AND SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS
WELL. ACROSS SERN CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE
PAST 24 HOURS AND WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS
HAVE SEEN READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM.
THE PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE
NORTHEAST EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR
SOUTHWEST FLOW. STILL...WITH THE INCREASED MOISTURE AND INSTABILITY
THERE WILL LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS
ACROSS THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS
POSSIBLE THAT A STRAY HIGH BASED STORM COULD DEVELOP OVER THE
CENTRAL DESERTS AS WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR
COMPARED TO THE BIG CHANGE IN THE WEATHER SLATED TO ARRIVE
MONDAY...AND CONTINUE THROUGH TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND
KSDL... SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO
KEEP SUNDAY AFTERNOON/S CROP OF SHOWERS/THUNDERSTORMS TO THE NORTH
AND EAST OF THE TERMINALS...WITH JUST SCT-BKN MID-HIGH CLOUD LAYERS
AFFECTING THE TERMINALS THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE
EXPECTED TO REMAIN P6SM...LEFTOVER DUST FROM SATURDAY/S
THUNDERSTORMS COULD AFFECT SLANTWISE VSBYS FOR INBOUND
AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS. WINDS ARE EXPECTED
TO FOLLOW TYPICAL DIURNAL TRENDS...WITH WESTERLY BREEZES PREVAILING
THROUGH THE AFTERNOON AND EARLY EVENING HOURS. CLOUDINESS IS
EXPECTED TO INCREASE...AND LOWER SOMEWHAT EARLY MONDAY MORNING AS
THE NEXT DISTURBANCE APPROACHES FROM THE WEST. THERE IS AN OUTSIDE
CHANCE THAT LIGHT SHOWERS COULD IMPACT THE PHX AREA TERMINALS AS
WELL EARLY TUESDAY MORNING...BUT CONFIDENCE IS FAR TOO LOW TO INCLUDE
IN THE TAFS AT THIS TIME.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH... ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND
KBLH...WITH JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-
TIME. SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER
AZ ON SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY
FOLLOW TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO
SOUTHEASTERLY WINDS DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY
EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY... A PACIFIC STORM THAT WILL BE AFFECTING
THE DESERT SW EARLY IN THE UPCOMING WORKWEEK WILL BRING A DECENT
CHANCE FOR SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON
TUESDAY...ESPECIALLY OVER THE HIGHER TERRAIN NORTH AND EAST OF
PHOENIX...WITH TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES.
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON
WEDNESDAY AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS
AND COOLER TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY
ONWARD INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS
THE GREAT BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING
THIS PERIOD AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY
WARMER TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 031022
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
320 AM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION... WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN
BAJA LED TO A FEW AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE
SOUTHERN AZ DESERTS YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED
LEAVING BEHIND VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE
SOUTHWEST FLOW ALOFT OVER THE AREA SPREAD INCREASING AMOUNTS OF
MOISTURE INTO THE AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z
SOUNDING...AND SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS
WELL. ACROSS SERN CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE
PAST 24 HOURS AND WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS
HAVE SEEN READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM.
THE PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE
NORTHEAST EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR
SOUTHWEST FLOW. STILL...WITH THE INCREASED MOISTURE AND INSTABILITY
THERE WILL LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS
ACROSS THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS
POSSIBLE THAT A STRAY HIGH BASED STORM COULD DEVELOP OVER THE
CENTRAL DESERTS AS WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR
COMPARED TO THE BIG CHANGE IN THE WEATHER SLATED TO ARRIVE
MONDAY...AND CONTINUE THROUGH TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND
KSDL... SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO
KEEP SUNDAY AFTERNOON/S CROP OF SHOWERS/THUNDERSTORMS TO THE NORTH
AND EAST OF THE TERMINALS...WITH JUST SCT-BKN MID-HIGH CLOUD LAYERS
AFFECTING THE TERMINALS THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE
EXPECTED TO REMAIN P6SM...LEFTOVER DUST FROM SATURDAY/S
THUNDERSTORMS COULD AFFECT SLANTWISE VSBYS FOR INBOUND
AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS. WINDS ARE EXPECTED
TO FOLLOW TYPICAL DIURNAL TRENDS...WITH WESTERLY BREEZES PREVAILING
THROUGH THE AFTERNOON AND EARLY EVENING HOURS. CLOUDINESS IS
EXPECTED TO INCREASE...AND LOWER SOMEWHAT EARLY MONDAY MORNING AS
THE NEXT DISTURBANCE APPROACHES FROM THE WEST. THERE IS AN OUTSIDE
CHANCE THAT LIGHT SHOWERS COULD IMPACT THE PHX AREA TERMINALS AS
WELL EARLY TUESDAY MORNING...BUT CONFIDENCE IS FAR TOO LOW TO INCLUDE
IN THE TAFS AT THIS TIME.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH... ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND
KBLH...WITH JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-
TIME. SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER
AZ ON SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY
FOLLOW TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO
SOUTHEASTERLY WINDS DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY
EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY... A PACIFIC STORM THAT WILL BE AFFECTING
THE DESERT SW EARLY IN THE UPCOMING WORKWEEK WILL BRING A DECENT
CHANCE FOR SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON
TUESDAY...ESPECIALLY OVER THE HIGHER TERRAIN NORTH AND EAST OF
PHOENIX...WITH TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES.
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON
WEDNESDAY AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS
AND COOLER TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY
ONWARD INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS
THE GREAT BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING
THIS PERIOD AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY
WARMER TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 031022
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
320 AM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION... WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN
BAJA LED TO A FEW AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE
SOUTHERN AZ DESERTS YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED
LEAVING BEHIND VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE
SOUTHWEST FLOW ALOFT OVER THE AREA SPREAD INCREASING AMOUNTS OF
MOISTURE INTO THE AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z
SOUNDING...AND SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS
WELL. ACROSS SERN CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE
PAST 24 HOURS AND WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS
HAVE SEEN READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM.
THE PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE
NORTHEAST EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR
SOUTHWEST FLOW. STILL...WITH THE INCREASED MOISTURE AND INSTABILITY
THERE WILL LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS
ACROSS THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS
POSSIBLE THAT A STRAY HIGH BASED STORM COULD DEVELOP OVER THE
CENTRAL DESERTS AS WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR
COMPARED TO THE BIG CHANGE IN THE WEATHER SLATED TO ARRIVE
MONDAY...AND CONTINUE THROUGH TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND
KSDL... SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO
KEEP SUNDAY AFTERNOON/S CROP OF SHOWERS/THUNDERSTORMS TO THE NORTH
AND EAST OF THE TERMINALS...WITH JUST SCT-BKN MID-HIGH CLOUD LAYERS
AFFECTING THE TERMINALS THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE
EXPECTED TO REMAIN P6SM...LEFTOVER DUST FROM SATURDAY/S
THUNDERSTORMS COULD AFFECT SLANTWISE VSBYS FOR INBOUND
AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS. WINDS ARE EXPECTED
TO FOLLOW TYPICAL DIURNAL TRENDS...WITH WESTERLY BREEZES PREVAILING
THROUGH THE AFTERNOON AND EARLY EVENING HOURS. CLOUDINESS IS
EXPECTED TO INCREASE...AND LOWER SOMEWHAT EARLY MONDAY MORNING AS
THE NEXT DISTURBANCE APPROACHES FROM THE WEST. THERE IS AN OUTSIDE
CHANCE THAT LIGHT SHOWERS COULD IMPACT THE PHX AREA TERMINALS AS
WELL EARLY TUESDAY MORNING...BUT CONFIDENCE IS FAR TOO LOW TO INCLUDE
IN THE TAFS AT THIS TIME.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH... ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND
KBLH...WITH JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-
TIME. SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER
AZ ON SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY
FOLLOW TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO
SOUTHEASTERLY WINDS DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY
EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY... A PACIFIC STORM THAT WILL BE AFFECTING
THE DESERT SW EARLY IN THE UPCOMING WORKWEEK WILL BRING A DECENT
CHANCE FOR SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON
TUESDAY...ESPECIALLY OVER THE HIGHER TERRAIN NORTH AND EAST OF
PHOENIX...WITH TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES.
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON
WEDNESDAY AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS
AND COOLER TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY
ONWARD INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS
THE GREAT BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING
THIS PERIOD AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY
WARMER TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 031022
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
320 AM MST SUN MAY 3 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA TODAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER IN THE WEEK. THIS LATE WEEK SYSTEM IS EXPECTED
TO BE DRY BUT WILL LEAD TO ANOTHER COOLING TREND ALONG WITH
INCREASED AFTERNOON BREEZINESS.

&&

.DISCUSSION... WEAK SHORT WAVE MOVING INTO ARIZONA FROM NORTHERN
BAJA LED TO A FEW AFTERNOON AND EVENING THUNDERSTORMS ACROSS THE
SOUTHERN AZ DESERTS YESTERDAY...AND AS OF 3 AM CONVECTION HAD ENDED
LEAVING BEHIND VARIABLE AMOUNTS OF MID LEVEL DEBRIS CLOUD. THE
SOUTHWEST FLOW ALOFT OVER THE AREA SPREAD INCREASING AMOUNTS OF
MOISTURE INTO THE AREA...PWAT AT TUS ROSE TO 0.70 PER THE RECENT 00Z
SOUNDING...AND SURFACE DEWPOINTS OVER THE DESERTS HAVE CLIMBED AS
WELL. ACROSS SERN CA...DEWPOINTS HAVE CLIMBED 10-15 DEGREES OVER THE
PAST 24 HOURS AND WERE RUNNING MOSTLY IN THE 40S. CENTRAL AZ DESERTS
HAVE SEEN READINGS IN THE UPPER 30S TO MID 40S EARLY AS OF 3 AM.
THE PREVIOUSLY MENTIONED SHORTWAVE IS EXPECTED TO LIFT TO THE
NORTHEAST EARLY THIS MORNING...LEAVING BEHIND A MORE LAMINAR
SOUTHWEST FLOW. STILL...WITH THE INCREASED MOISTURE AND INSTABILITY
THERE WILL LIKELY BE ISOLATED AFTERNOON/EVENING SHOWERS OR STORMS
ACROSS THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX AND IT IS
POSSIBLE THAT A STRAY HIGH BASED STORM COULD DEVELOP OVER THE
CENTRAL DESERTS AS WELL. ANY CONVECTION SEEN TODAY WILL BE MINOR
COMPARED TO THE BIG CHANGE IN THE WEATHER SLATED TO ARRIVE
MONDAY...AND CONTINUE THROUGH TUESDAY.

PROGS REMAIN VERY CONSISTENT IN CALLING FOR A MODERATELY STRONG
UPPER LOW TO MOVE INTO THE DESERT SOUTHWEST FROM OFF OF THE SRN CA
AND NRN BAJA COAST LATE TONIGHT...AND THEN MOVE PROGRESSIVELY EAST
ACROSS ARIZONA MONDAY INTO TUESDAY LEADING TO SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS SOUTH CENTRAL ARIZONA...AND ISOLATED
SHOWERS/STORMS OVER THE WESTERN DESERTS. THE BEST WINDOW FOR PRECIP
ACROSS SOUTH CENTRAL AZ APPEARS TO BE MONDAY AFTERNOON AND
EVENING...AND THAT PERIOD CONTAINS THE HIGHEST POPS WHICH RANGE FROM
30 TO OVER 50 PERCENT. DESPITE ONLY MODEST WIND FIELDS ASSOCIATED
WITH THE LOW...AND NOT OVERLY IMPRESSIVE QG FORCING/DYNAMICS...THE
ATMOSPHERE WILL BECOME RATHER MOIST AND UNSTABLE WITH PWAT VALUES
OVER THE DESERT CLIMBING TO AROUND 1 INCH BY MONDAY AFTERNOON. GFS
CAPE VALUES ARE FORECAST TO RISE OVER 800 J/KG...AND THE NAM
FORECASTS CAPE WELL IN EXCESS OF 1000 J/KG OVER SOUTH CENTRAL AZ
MONDAY AFTERNOON. THUS WE SHOULD CERTAINLY SEE SCATTERED
THUNDERSTORMS DEVELOP MONDAY AND CONTINUE INTO THE EVENING HOURS AND
SOME STORMS MAY PRODUCE LOCALLY HEAVY RAIN AS WELL AS POTENTIALLY
STRONG GUSTY WINDS. THE EXPECTED CLOUDS/SHOWERS AND THICKNESS
COOLING WILL LEAD TO A SHARP DROP IN HIGH TEMPS MONDAY AND TUESDAY
WITH THE CENTRAL DESERTS LOWERING INTO THE LOW TO MIDDLE 80S. WARMER
TEMPS...REACHING UPPER 80S TO AROUND 90...ARE EXPECTED OVER THE FAR
WESTERN DESERTS.

BY TUESDAY AFTERNOON THE SYSTEM WILL BE LIFTING TO THE NORTHEAST OF
PHOENIX AND INTO NEW MEXICO...BUT THERE WILL BE SUFFICIENT LINGERING
MOISTURE AND INSTABILITY TO GENERATE A FEW SHOWERS OR STORMS ACROSS
THE CENTRAL DESERTS...AND EVEN SCATTERED CONVECTION OVER THE HIGHER
TERRAIN EAST OF PHOENIX. DRIER SOUTHWEST FLOW ALOFT WILL SPREAD INTO
THE AREA WEDNESDAY BEHIND THE EXITING SYSTEM LEADING TO PARTLY OR
MOSTLY SUNNY SKIES AND SLIGHTLY WARMER HIGH TEMPERATURES.
STILL...READINGS WILL LIKELY REMAIN SLIGHTLY BELOW SEASONAL NORMALS
AS HIGHS STAY MOSTLY IN THE 80S.

FOR THE EXTENDED PERIOD...THURSDAY THROUGH SATURDAY...MEDIUM RANGE
MODELS INCLUDING THEIR ENSEMBLE MEMBERS HAVE COME INTO AGREEMENT AND
CALL FOR A LARGE UPPER TROF TO SETTLE INTO THE WESTERN CONUS. THIS
SYSTEM WILL BE CENTERED WELL TO THE NORTHWEST OF PHOENIX...OVER
PORTIONS OF SRN CA AND NEVADA...AND AS SUCH THE SOUTHERN AZ DESERTS
WILL STAY ON THE SOUTHERN FLANK OF THE LOW. THIS WILL RESULT IN A
MOSTLY DRY SOUTHWEST/WEST FLOW ALOFT FOR OUR AREA AND WILL RESULT IN
A MARKED COOLING TREND WITH HIGH TEMPS DROPPING WELL BELOW SEASONAL
NORMALS AND INTO THE LOW TO MID 80S. INCREASED BREEZINESS IS ALSO
EXPECTED DURING THE AFTERNOON AND EARLY EVENING HOURS THURSDAY AND
FRIDAY...AND GIVEN THE EXPECTED DRY CONDITIONS WITH LOW SURFACE
RH...FIRE WEATHER CONCERNS ARE LIKELY AS WELL. AT THIS TIME WE WILL
CONFINE ANY THREAT FOR PRECIP DURING THE PERIOD TO THE HIGHER
TERRAIN OF JOSHUA TREE NATIONAL PARK.

&&

.AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND
KSDL... SLIGHTLY DRIER AIR MOVING INTO THE REGION IS EXPECTED TO
KEEP SUNDAY AFTERNOON/S CROP OF SHOWERS/THUNDERSTORMS TO THE NORTH
AND EAST OF THE TERMINALS...WITH JUST SCT-BKN MID-HIGH CLOUD LAYERS
AFFECTING THE TERMINALS THEMSELVES. ALTHOUGH SFC VISIBILITIES ARE
EXPECTED TO REMAIN P6SM...LEFTOVER DUST FROM SATURDAY/S
THUNDERSTORMS COULD AFFECT SLANTWISE VSBYS FOR INBOUND
AIRCRAFT...ESPECIALLY DURING THE MORNING HOURS. WINDS ARE EXPECTED
TO FOLLOW TYPICAL DIURNAL TRENDS...WITH WESTERLY BREEZES PREVAILING
THROUGH THE AFTERNOON AND EARLY EVENING HOURS. CLOUDINESS IS
EXPECTED TO INCREASE...AND LOWER SOMEWHAT EARLY MONDAY MORNING AS
THE NEXT DISTURBANCE APPROACHES FROM THE WEST. THERE IS AN OUTSIDE
CHANCE THAT LIGHT SHOWERS COULD IMPACT THE PHX AREA TERMINALS AS
WELL EARLY TUESDAY MORNING...BUT CONFIDENCE IS FAR TOO LOW TO INCLUDE
IN THE TAFS AT THIS TIME.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH... ANOTHER QUIET TAF PERIOD IS EXPECTED AT BOTH KIPL AND
KBLH...WITH JUST SOME HIGH CLOUDINESS PASSING OVERHEAD FROM TIME-TO-
TIME. SHOWER/THUNDERSTORM ACTIVITY THAT IS EXPECTED TO DEVELOP OVER
AZ ON SUNDAY AFTERNOON TO REMAIN WELL EAST OF KBLH. WINDS TO MAINLY
FOLLOW TYPICAL DIURNAL TRENDS...WITH GUSTY SOUTHERLY TO
SOUTHEASTERLY WINDS DEVELOPING FOR A TIME ON SUNDAY AFTERNOON/EARLY
EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY... A PACIFIC STORM THAT WILL BE AFFECTING
THE DESERT SW EARLY IN THE UPCOMING WORKWEEK WILL BRING A DECENT
CHANCE FOR SHOWERS/THUNDERSTORMS TO SOUTH-CENTRAL AZ ON
TUESDAY...ESPECIALLY OVER THE HIGHER TERRAIN NORTH AND EAST OF
PHOENIX...WITH TEMPERATURES FALLING TO SLIGHTLY BELOW NORMAL VALUES.
DRY WEATHER...AND SLIGHTLY WARMER TEMPERATURES TO RETURN ON
WEDNESDAY AS WEAK HIGH PRESSURE PASSES OVER THE REGION. GUSTY WINDS
AND COOLER TEMPERATURES TO PREVAIL ACROSS THE REGION FROM THURSDAY
ONWARD INTO SATURDAY AS ANOTHER PACIFIC STORM SYSTEM MOVES ACROSS
THE GREAT BASIN. FIRE DANGER LEVELS WILL LIKELY BE ELEVATED DURING
THIS PERIOD AS AFTERNOON HUMIDITIES FALL INTO THE TEENS. SLIGHTLY
WARMER TEMPERATURES AND LESS WIND CAN BE EXPECTED ON SATURDAY AS THE
AFOREMENTIONED PACIFIC STORM SYSTEM BEGINS TO MOVE OFF TO THE EAST.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 030354
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
854 PM MST SAT MAY 2 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...
VERY ISOLATED SHOWERS/TSTORMS CONTINUE TO MOVE THROUGH THE EAST
VALLEY OF THE PHOENIX METRO AREA AS OF 0345Z THIS EVENING...AS THE
LAST BIT OF THIS AFTERNOON`S BL INSTABILITY IS EXHAUSTED. NOT
SURPRISINGLY...MOST OF THIS EVENING`S ACTIVITY WAS IN THE FORM OF
BLOWING DUST/OUTFLOW WINDS...BUT A FEW SPOTS MANAGED TO SEE
MEASURABLE PRECIP. AT THIS POINT THE FEW SHOWERS THAT REMAIN ARE
ONLY PRODUCING SPRINKLES/VIRGA AND PATCHY BLOWING DUST...AND IT WOULD
APPEAR THE ACTIVITY WILL CONTINUE TO TREND DOWNWARD THROUGH THE
EVENING/OVERNIGHT HOURS. LAST FEW RUNS OF THE HRRR SUGGEST 100-250
J/KG OF ELEVATED INSTABILITY THROUGH 06Z...THEN RAPID STABILIZATION
FOR THE DURATION OF THE OVERNIGHT HOURS.

MADE A FEW FORECAST ADJUSTMENTS OVER THE PAST FEW HOURS TO CAPTURE
WIND/DEWPOINT/SKY TRENDS. POPS STILL LOOK REASONABLE AND SINGLE
DIGIT VALUES AFTER 06Z SEEM WARRANTED. NO ADDITIONAL CHANGES APPEAR
NECESSARY AT THIS POINT.

&&

.PREVIOUS DISCUSSION...
SUNDAY THROUGH TUESDAY...
A MAJOR CHANGE IN THE FLOW PATTERN/JET STREAM WILL TAKE PLACE SUNDAY
THROUGH TUESDAY AS A NUMBER OF SMALL DISTURBANCES MOVE THROUGH THE
REGION THIS EVENING AND SUNDAY AFTERNOON...FOLLOWED BY A MAJOR COOL
TROF MONDAY AND TUESDAY.

AS THE MULTITUDE OF SHORTWAVES CONTINUE TO MOVE INTO THE REGION FROM
THE WEST...MODELS FORECAST A LONG SOUTHERLY FETCH OF 850 MB WINDS
EMANATING FROM THE LOWER GULF OF CA. PRECIP WATER (PW) IMAGERY
DETECTED THE HIGHEST VALUES OF PW IN THAT DIRECTION...SO AN
INCREASINGLY MOIST BOUNDARY LAYER IS EXPECTED INTO SOUTHERN AZ THE
NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SUSPENDED DUST/HAZE WILL CONTINUE TO MOVE THROUGH THE METRO THIS
EVENING AND WHILE SURFACE VSBYS WILL REMAIN P6SM...SLANTWISE VSBYS
WILL BE COMPROMISED THROUGH SUNDAY MORNING. EXPECTING LESS CONVECTION
DURING THE DAY SUNDAY AND I WILL ONLY INCLUDE FEW/SCT MID CLOUDS
SUNDAY AFTERNOON ALONG WITH TYPICAL DIURNAL WINDS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
STILL EXPECTING LOW-IMPACT WEATHER EXPECTED ACROSS SOUTHEAST
CALIFORNIA. WINDS WILL FOLLOW TYPICAL DIURNAL TRENDS THROUGH SUNDAY
EVENING. ANY STORMS THAT DEVELOP ON SUNDAY WOULD LIKELY BE CONFINED
TO AREAS WELL NORTH/EAST OF THE LOWER COLORADO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND AFTERNOON
HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER LEVELS TO
RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES ARE
EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 030354
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
854 PM MST SAT MAY 2 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...
VERY ISOLATED SHOWERS/TSTORMS CONTINUE TO MOVE THROUGH THE EAST
VALLEY OF THE PHOENIX METRO AREA AS OF 0345Z THIS EVENING...AS THE
LAST BIT OF THIS AFTERNOON`S BL INSTABILITY IS EXHAUSTED. NOT
SURPRISINGLY...MOST OF THIS EVENING`S ACTIVITY WAS IN THE FORM OF
BLOWING DUST/OUTFLOW WINDS...BUT A FEW SPOTS MANAGED TO SEE
MEASURABLE PRECIP. AT THIS POINT THE FEW SHOWERS THAT REMAIN ARE
ONLY PRODUCING SPRINKLES/VIRGA AND PATCHY BLOWING DUST...AND IT WOULD
APPEAR THE ACTIVITY WILL CONTINUE TO TREND DOWNWARD THROUGH THE
EVENING/OVERNIGHT HOURS. LAST FEW RUNS OF THE HRRR SUGGEST 100-250
J/KG OF ELEVATED INSTABILITY THROUGH 06Z...THEN RAPID STABILIZATION
FOR THE DURATION OF THE OVERNIGHT HOURS.

MADE A FEW FORECAST ADJUSTMENTS OVER THE PAST FEW HOURS TO CAPTURE
WIND/DEWPOINT/SKY TRENDS. POPS STILL LOOK REASONABLE AND SINGLE
DIGIT VALUES AFTER 06Z SEEM WARRANTED. NO ADDITIONAL CHANGES APPEAR
NECESSARY AT THIS POINT.

&&

.PREVIOUS DISCUSSION...
SUNDAY THROUGH TUESDAY...
A MAJOR CHANGE IN THE FLOW PATTERN/JET STREAM WILL TAKE PLACE SUNDAY
THROUGH TUESDAY AS A NUMBER OF SMALL DISTURBANCES MOVE THROUGH THE
REGION THIS EVENING AND SUNDAY AFTERNOON...FOLLOWED BY A MAJOR COOL
TROF MONDAY AND TUESDAY.

AS THE MULTITUDE OF SHORTWAVES CONTINUE TO MOVE INTO THE REGION FROM
THE WEST...MODELS FORECAST A LONG SOUTHERLY FETCH OF 850 MB WINDS
EMANATING FROM THE LOWER GULF OF CA. PRECIP WATER (PW) IMAGERY
DETECTED THE HIGHEST VALUES OF PW IN THAT DIRECTION...SO AN
INCREASINGLY MOIST BOUNDARY LAYER IS EXPECTED INTO SOUTHERN AZ THE
NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SUSPENDED DUST/HAZE WILL CONTINUE TO MOVE THROUGH THE METRO THIS
EVENING AND WHILE SURFACE VSBYS WILL REMAIN P6SM...SLANTWISE VSBYS
WILL BE COMPROMISED THROUGH SUNDAY MORNING. EXPECTING LESS CONVECTION
DURING THE DAY SUNDAY AND I WILL ONLY INCLUDE FEW/SCT MID CLOUDS
SUNDAY AFTERNOON ALONG WITH TYPICAL DIURNAL WINDS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
STILL EXPECTING LOW-IMPACT WEATHER EXPECTED ACROSS SOUTHEAST
CALIFORNIA. WINDS WILL FOLLOW TYPICAL DIURNAL TRENDS THROUGH SUNDAY
EVENING. ANY STORMS THAT DEVELOP ON SUNDAY WOULD LIKELY BE CONFINED
TO AREAS WELL NORTH/EAST OF THE LOWER COLORADO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND AFTERNOON
HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER LEVELS TO
RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES ARE
EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/VASQUEZ
AVIATION...LEINS
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 022313 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
413 PM MST SAT MAY 2 2015

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...A MAJOR CHANGE IN THE FLOW PATTERN/JET
STREAM WILL TAKE PLACE TODAY THROUGH TUESDAY AS A NUMBER OF SMALL
DISTURBANCES MOVE THROUGH THE REGION THIS EVENING AND SUNDAY
AFTERNOON...FOLLOWED BY A MAJOR COOL TROF MONDAY AND TUESDAY.

THE DISTURBANCE WORKING ITS WAY INTO CENTRAL THIS AFTERNOON...BEST
SEEN IN WATER VAPOR IMAGERY...ALONG WITH AN INCREASE IN BOUNDARY
LAYER MOISTURE HAS LEAD TO SCATTERED THUNDERSTORMS MAINLY IN THE
HIGH COUNTRY FROM PRESCOTT EAST TO THE WHITE MOUNTAINS AS 2 PM. THIS
MORNINGS ANALYSIS SHOWED THERE WAS A SLIGHT THREAT OF AFTERNOON
THUNDERSTORMS ACROSS PARTS OF THE SOUTH CENTRAL AZ DESERTS AND
MOUNTAINS FROM PHOENIX EAST AND SOUTHEAST AS A FUNCTION OF THIS
SHORTWAVE AND UPPER LEVEL CYCLONIC FLOW. SPECIAL EXPERIMENTAL HRRR
SATELLITE DERIVED FUTURE PRECIP FORECASTS DID SHOW A TSTM THREAT
JUST EAST AND SOUTHEAST OF PHOENIX FLOWING NORTH FROM SOUTHERN AZ
FOR LATE TODAY. THEREFORE A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
EARLY EVENING WILL CONTINUE FOR AREAS EAST AND SOUTHEAST OF PHOENIX.

CLEARING SKIES TONIGHT.

INCREASING LOW LEVEL MOISTURE.  AS THE MULTITUDE OF SHORTWAVES
CONTINUE TO MOVE INTO THE REGION FROM THE WEST...MODELS FORECAST A
LONG SOUTHERLY FETCH OF 850 MB WINDS EMANATING FROM THE LOWER GULF
OF CA. PRECIP WATER (PW) IMAGERY DETECTED THE HIGHEST VALUES OF PW
IN THAT DIRECTION...SO AN INCREASINGLY MOIST BOUNDARY LAYER IS
EXPECTED INTO SOUTHERN AZ THE NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
STORMS HAVE FORMED ACROSS THE AREA BUT THE BULK OF THE ACTIVITY HAS
REMAINED TO THE SOUTH/EAST OF PHOENIX. LAST FEW RUNS OF THE HRRR AND
OTHER HI-RES MODELS SUGGEST STORMS WILL DIMINISH BEFORE THEY REACH
THE LOWER DESERTS AND I WILL KEEP ANY MENTION OF THUNDER OUT OF THE
PHOENIX TERMINALS. WILL NEED TO KEEP AN EYE ON OUTFLOWS OUT OF THE
SOUTH - ESPECIALLY AT KIWA ALTHOUGH CONFIDENCE IS LOW THAT THEY WOULD
SURVIVE LONG ENOUGH TO BE OF MUCH IMPACT. KPHX/KSDL SHOULD SEE
TYPICAL DIURNAL WINDS THIS EVENING THROUGH SUNDAY.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LOW-IMPACT WEATHER EXPECTED ACROSS SOUTHEAST CALIFORNIA. OUTSIDE OF
SOME BREEZINESS AT KBLH THIS EVENING...WINDS WILL FOLLOW TYPICAL
DIURNAL TRENDS. ANY STORMS THAT DEVELOP SHOULD REMAIN EAST OF THE
COLORADO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND AFTERNOON
HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER LEVELS TO
RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES ARE
EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ
AVIATION...LEINS
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 022313 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
413 PM MST SAT MAY 2 2015

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...A MAJOR CHANGE IN THE FLOW PATTERN/JET
STREAM WILL TAKE PLACE TODAY THROUGH TUESDAY AS A NUMBER OF SMALL
DISTURBANCES MOVE THROUGH THE REGION THIS EVENING AND SUNDAY
AFTERNOON...FOLLOWED BY A MAJOR COOL TROF MONDAY AND TUESDAY.

THE DISTURBANCE WORKING ITS WAY INTO CENTRAL THIS AFTERNOON...BEST
SEEN IN WATER VAPOR IMAGERY...ALONG WITH AN INCREASE IN BOUNDARY
LAYER MOISTURE HAS LEAD TO SCATTERED THUNDERSTORMS MAINLY IN THE
HIGH COUNTRY FROM PRESCOTT EAST TO THE WHITE MOUNTAINS AS 2 PM. THIS
MORNINGS ANALYSIS SHOWED THERE WAS A SLIGHT THREAT OF AFTERNOON
THUNDERSTORMS ACROSS PARTS OF THE SOUTH CENTRAL AZ DESERTS AND
MOUNTAINS FROM PHOENIX EAST AND SOUTHEAST AS A FUNCTION OF THIS
SHORTWAVE AND UPPER LEVEL CYCLONIC FLOW. SPECIAL EXPERIMENTAL HRRR
SATELLITE DERIVED FUTURE PRECIP FORECASTS DID SHOW A TSTM THREAT
JUST EAST AND SOUTHEAST OF PHOENIX FLOWING NORTH FROM SOUTHERN AZ
FOR LATE TODAY. THEREFORE A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
EARLY EVENING WILL CONTINUE FOR AREAS EAST AND SOUTHEAST OF PHOENIX.

CLEARING SKIES TONIGHT.

INCREASING LOW LEVEL MOISTURE.  AS THE MULTITUDE OF SHORTWAVES
CONTINUE TO MOVE INTO THE REGION FROM THE WEST...MODELS FORECAST A
LONG SOUTHERLY FETCH OF 850 MB WINDS EMANATING FROM THE LOWER GULF
OF CA. PRECIP WATER (PW) IMAGERY DETECTED THE HIGHEST VALUES OF PW
IN THAT DIRECTION...SO AN INCREASINGLY MOIST BOUNDARY LAYER IS
EXPECTED INTO SOUTHERN AZ THE NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
STORMS HAVE FORMED ACROSS THE AREA BUT THE BULK OF THE ACTIVITY HAS
REMAINED TO THE SOUTH/EAST OF PHOENIX. LAST FEW RUNS OF THE HRRR AND
OTHER HI-RES MODELS SUGGEST STORMS WILL DIMINISH BEFORE THEY REACH
THE LOWER DESERTS AND I WILL KEEP ANY MENTION OF THUNDER OUT OF THE
PHOENIX TERMINALS. WILL NEED TO KEEP AN EYE ON OUTFLOWS OUT OF THE
SOUTH - ESPECIALLY AT KIWA ALTHOUGH CONFIDENCE IS LOW THAT THEY WOULD
SURVIVE LONG ENOUGH TO BE OF MUCH IMPACT. KPHX/KSDL SHOULD SEE
TYPICAL DIURNAL WINDS THIS EVENING THROUGH SUNDAY.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LOW-IMPACT WEATHER EXPECTED ACROSS SOUTHEAST CALIFORNIA. OUTSIDE OF
SOME BREEZINESS AT KBLH THIS EVENING...WINDS WILL FOLLOW TYPICAL
DIURNAL TRENDS. ANY STORMS THAT DEVELOP SHOULD REMAIN EAST OF THE
COLORADO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND AFTERNOON
HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER LEVELS TO
RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES ARE
EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ
AVIATION...LEINS
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 022313 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
413 PM MST SAT MAY 2 2015

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...A MAJOR CHANGE IN THE FLOW PATTERN/JET
STREAM WILL TAKE PLACE TODAY THROUGH TUESDAY AS A NUMBER OF SMALL
DISTURBANCES MOVE THROUGH THE REGION THIS EVENING AND SUNDAY
AFTERNOON...FOLLOWED BY A MAJOR COOL TROF MONDAY AND TUESDAY.

THE DISTURBANCE WORKING ITS WAY INTO CENTRAL THIS AFTERNOON...BEST
SEEN IN WATER VAPOR IMAGERY...ALONG WITH AN INCREASE IN BOUNDARY
LAYER MOISTURE HAS LEAD TO SCATTERED THUNDERSTORMS MAINLY IN THE
HIGH COUNTRY FROM PRESCOTT EAST TO THE WHITE MOUNTAINS AS 2 PM. THIS
MORNINGS ANALYSIS SHOWED THERE WAS A SLIGHT THREAT OF AFTERNOON
THUNDERSTORMS ACROSS PARTS OF THE SOUTH CENTRAL AZ DESERTS AND
MOUNTAINS FROM PHOENIX EAST AND SOUTHEAST AS A FUNCTION OF THIS
SHORTWAVE AND UPPER LEVEL CYCLONIC FLOW. SPECIAL EXPERIMENTAL HRRR
SATELLITE DERIVED FUTURE PRECIP FORECASTS DID SHOW A TSTM THREAT
JUST EAST AND SOUTHEAST OF PHOENIX FLOWING NORTH FROM SOUTHERN AZ
FOR LATE TODAY. THEREFORE A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
EARLY EVENING WILL CONTINUE FOR AREAS EAST AND SOUTHEAST OF PHOENIX.

CLEARING SKIES TONIGHT.

INCREASING LOW LEVEL MOISTURE.  AS THE MULTITUDE OF SHORTWAVES
CONTINUE TO MOVE INTO THE REGION FROM THE WEST...MODELS FORECAST A
LONG SOUTHERLY FETCH OF 850 MB WINDS EMANATING FROM THE LOWER GULF
OF CA. PRECIP WATER (PW) IMAGERY DETECTED THE HIGHEST VALUES OF PW
IN THAT DIRECTION...SO AN INCREASINGLY MOIST BOUNDARY LAYER IS
EXPECTED INTO SOUTHERN AZ THE NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
STORMS HAVE FORMED ACROSS THE AREA BUT THE BULK OF THE ACTIVITY HAS
REMAINED TO THE SOUTH/EAST OF PHOENIX. LAST FEW RUNS OF THE HRRR AND
OTHER HI-RES MODELS SUGGEST STORMS WILL DIMINISH BEFORE THEY REACH
THE LOWER DESERTS AND I WILL KEEP ANY MENTION OF THUNDER OUT OF THE
PHOENIX TERMINALS. WILL NEED TO KEEP AN EYE ON OUTFLOWS OUT OF THE
SOUTH - ESPECIALLY AT KIWA ALTHOUGH CONFIDENCE IS LOW THAT THEY WOULD
SURVIVE LONG ENOUGH TO BE OF MUCH IMPACT. KPHX/KSDL SHOULD SEE
TYPICAL DIURNAL WINDS THIS EVENING THROUGH SUNDAY.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LOW-IMPACT WEATHER EXPECTED ACROSS SOUTHEAST CALIFORNIA. OUTSIDE OF
SOME BREEZINESS AT KBLH THIS EVENING...WINDS WILL FOLLOW TYPICAL
DIURNAL TRENDS. ANY STORMS THAT DEVELOP SHOULD REMAIN EAST OF THE
COLORADO RIVER.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND AFTERNOON
HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER LEVELS TO
RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES ARE
EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ
AVIATION...LEINS
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 022205
AFDPSR

ZCZC PHXWRKAFD 022039
TTAA00 KPHX DDHHMM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
305 PM MST SAT MAY 2 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...A MAJOR CHANGE IN THE FLOW PATTERN/JET
STREAM WILL TAKE PLACE TODAY THROUGH TUESDAY AS A NUMBER OF SMALL
DISTURBANCES MOVE THROUGH THE REGION THIS EVENING AND SUNDAY
AFTERNOON...FOLLOWED BY A MAJOR COOL TROF MONDAY AND TUESDAY.

THE DISTURBANCE WORKING ITS WAY INTO CENTRAL THIS AFTERNOON...BEST
SEEN IN WATER VAPOR IMAGERY...ALONG WITH AN INCREASE IN BOUNDARY
LAYER MOISTURE HAS LEAD TO SCATTERED THUNDERSTORMS MAINLY IN THE
HIGH COUNTRY FROM PRESCOTT EAST TO THE WHITE MOUNTAINS AS 2 PM. THIS
MORNINGS ANALYSIS SHOWED THERE WAS A SLIGHT THREAT OF AFTERNOON
THUNDERSTORMS ACROSS PARTS OF THE SOUTH CENTRAL AZ DESERTS AND
MOUNTAINS FROM PHOENIX EAST AND SOUTHEAST AS A FUNCTION OF THIS
SHORTWAVE AND UPPER LEVEL CYCLONIC FLOW. SPECIAL EXPERIMENTAL HRRR
SATELLITE DERIVED FUTURE PRECIP FORECASTS DID SHOW A TSTM THREAT
JUST EAST AND SOUTHEAST OF PHOENIX FLOWING NORTH FROM SOUTHERN AZ
FOR LATE TODAY. THEREFORE A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
EARLY EVENING WILL CONTINUE FOR AREAS EAST AND SOUTHEAST OF PHOENIX.

CLEARING SKIES TONIGHT.

INCREASING LOW LEVEL MOISTURE.  AS THE MULTITUDE OF SHORTWAVES
CONTINUE TO MOVE INTO THE REGION FROM THE WEST...MODELS FORECAST A
LONG SOUTHERLY FETCH OF 850 MB WINDS EMANATING FROM THE LOWER GULF
OF CA. PRECIP WATER (PW) IMAGERY DETECTED THE HIGHEST VALUES OF PW
IN THAT DIRECTION...SO AN INCREASINGLY MOIST BOUNDARY LAYER IS
EXPECTED INTO SOUTHERN AZ THE NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 022205
AFDPSR

ZCZC PHXWRKAFD 022039
TTAA00 KPHX DDHHMM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
305 PM MST SAT MAY 2 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...A MAJOR CHANGE IN THE FLOW PATTERN/JET
STREAM WILL TAKE PLACE TODAY THROUGH TUESDAY AS A NUMBER OF SMALL
DISTURBANCES MOVE THROUGH THE REGION THIS EVENING AND SUNDAY
AFTERNOON...FOLLOWED BY A MAJOR COOL TROF MONDAY AND TUESDAY.

THE DISTURBANCE WORKING ITS WAY INTO CENTRAL THIS AFTERNOON...BEST
SEEN IN WATER VAPOR IMAGERY...ALONG WITH AN INCREASE IN BOUNDARY
LAYER MOISTURE HAS LEAD TO SCATTERED THUNDERSTORMS MAINLY IN THE
HIGH COUNTRY FROM PRESCOTT EAST TO THE WHITE MOUNTAINS AS 2 PM. THIS
MORNINGS ANALYSIS SHOWED THERE WAS A SLIGHT THREAT OF AFTERNOON
THUNDERSTORMS ACROSS PARTS OF THE SOUTH CENTRAL AZ DESERTS AND
MOUNTAINS FROM PHOENIX EAST AND SOUTHEAST AS A FUNCTION OF THIS
SHORTWAVE AND UPPER LEVEL CYCLONIC FLOW. SPECIAL EXPERIMENTAL HRRR
SATELLITE DERIVED FUTURE PRECIP FORECASTS DID SHOW A TSTM THREAT
JUST EAST AND SOUTHEAST OF PHOENIX FLOWING NORTH FROM SOUTHERN AZ
FOR LATE TODAY. THEREFORE A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
EARLY EVENING WILL CONTINUE FOR AREAS EAST AND SOUTHEAST OF PHOENIX.

CLEARING SKIES TONIGHT.

INCREASING LOW LEVEL MOISTURE.  AS THE MULTITUDE OF SHORTWAVES
CONTINUE TO MOVE INTO THE REGION FROM THE WEST...MODELS FORECAST A
LONG SOUTHERLY FETCH OF 850 MB WINDS EMANATING FROM THE LOWER GULF
OF CA. PRECIP WATER (PW) IMAGERY DETECTED THE HIGHEST VALUES OF PW
IN THAT DIRECTION...SO AN INCREASINGLY MOIST BOUNDARY LAYER IS
EXPECTED INTO SOUTHERN AZ THE NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 022205
AFDPSR

ZCZC PHXWRKAFD 022039
TTAA00 KPHX DDHHMM

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
305 PM MST SAT MAY 2 2015

.SYNOPSIS...A SERIES OF PACIFIC WEATHER DISTURBANCES IS FORECAST TO
MOVE INTO THE REGION THROUGH TUESDAY...RESULTING IN A COOLING TREND.
ENOUGH MOISTURE WILL BE PRESENT FOR A SLIGHT CHANCE OF AFTERNOON AND
EARLY EVENING SHOWERS AND THUNDERSTORMS MAINLY OVER NORTHERN AND
EASTERN ARIZONA SUNDAY. A MUCH LARGER AND COLDER DISTURBANCE IS
FORECAST TO MOVE INTO THE REGION MONDAY AND TUESDAY FOR A GOOD
CHANCE OF SHOWERS AND THUNDERSTORMS AREA-WIDE. CLEARING IS EXPECTED
WEDNESDAY...HOWEVER ANOTHER LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION LATER NEXT WEEK.

&&

.DISCUSSION...

TONIGHT THROUGH TUESDAY...A MAJOR CHANGE IN THE FLOW PATTERN/JET
STREAM WILL TAKE PLACE TODAY THROUGH TUESDAY AS A NUMBER OF SMALL
DISTURBANCES MOVE THROUGH THE REGION THIS EVENING AND SUNDAY
AFTERNOON...FOLLOWED BY A MAJOR COOL TROF MONDAY AND TUESDAY.

THE DISTURBANCE WORKING ITS WAY INTO CENTRAL THIS AFTERNOON...BEST
SEEN IN WATER VAPOR IMAGERY...ALONG WITH AN INCREASE IN BOUNDARY
LAYER MOISTURE HAS LEAD TO SCATTERED THUNDERSTORMS MAINLY IN THE
HIGH COUNTRY FROM PRESCOTT EAST TO THE WHITE MOUNTAINS AS 2 PM. THIS
MORNINGS ANALYSIS SHOWED THERE WAS A SLIGHT THREAT OF AFTERNOON
THUNDERSTORMS ACROSS PARTS OF THE SOUTH CENTRAL AZ DESERTS AND
MOUNTAINS FROM PHOENIX EAST AND SOUTHEAST AS A FUNCTION OF THIS
SHORTWAVE AND UPPER LEVEL CYCLONIC FLOW. SPECIAL EXPERIMENTAL HRRR
SATELLITE DERIVED FUTURE PRECIP FORECASTS DID SHOW A TSTM THREAT
JUST EAST AND SOUTHEAST OF PHOENIX FLOWING NORTH FROM SOUTHERN AZ
FOR LATE TODAY. THEREFORE A SLIGHT CHANCE OF THUNDERSTORMS THROUGH
EARLY EVENING WILL CONTINUE FOR AREAS EAST AND SOUTHEAST OF PHOENIX.

CLEARING SKIES TONIGHT.

INCREASING LOW LEVEL MOISTURE.  AS THE MULTITUDE OF SHORTWAVES
CONTINUE TO MOVE INTO THE REGION FROM THE WEST...MODELS FORECAST A
LONG SOUTHERLY FETCH OF 850 MB WINDS EMANATING FROM THE LOWER GULF
OF CA. PRECIP WATER (PW) IMAGERY DETECTED THE HIGHEST VALUES OF PW
IN THAT DIRECTION...SO AN INCREASINGLY MOIST BOUNDARY LAYER IS
EXPECTED INTO SOUTHERN AZ THE NEXT 48 HOURS.

SUNDAY. CONTINUED UPPER LEVEL CYCLONIC FLOW WITH A SECONDARY WEAK
SHORTWAVE...COMBINED WITH A LITTLE MORE BOUNDARY LAYER MOISTURE AND
ANOTHER WARM AFTERNOON...WILL CONTINUE A SLIGHT CHANCE OF AFTERNOON
THUNDERSTORMS OVER THE MOUNTAINS OF SOUTH CENTRAL AZ FROM PHOENIX
EAST AND SOUTHEAST. SKIES WILL BECOME PARTLY CLOUDY SUNDAY
NIGHT.

MONDAY AND TUESDAY...A MAJOR COOL PACIFIC TROF IS FORECAST TO MOVE
INTO SOUTHERN CA EARLY MONDAY MORNING...THEN INTO AZ BY MONDAY
AFTERNOON. THIS TROF IS MUCH COLDER AND UNSTABLE ALOFT...HAS
STRONGER UPPER LEVEL DYNAMICS...AND WITH INCREASED BOUNDARY LAYER
MOISTURE WILL LEAD TO A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS
AREA-WIDE. SINCE IT WILL BE A SLOW EASTWARD MOVING TROF...THE CHANCE
OF SHOWERS AND THUNDERSTORMS WILL CONTINUE INTO EARLY TUESDAY.

WEDNESDAY...PARTLY CLOUDY WEDNESDAY WITH NO PRECIP AS A MINOR
SHORTWAVE RIDGE MOVES QUICKLY THROUGH THE REGION.

THURSDAY AND FRIDAY...ANOTHER COOL TROF IS FORECAST TO MOVE INTO THE
REGION THE NORTHWEST. PRECIP CHANCES FOR NOW WILL BE CONFINED TO
PARTS OF SOUTHEAST CA.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 021658 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
958 AM MST SAT MAY 2 2015

.UPDATE...TO AVIATION DISCUSSION...

&&

.SYNOPSIS...
DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS WEEKEND...AND WE
WILL SEE THE START OF A GRADUAL COOLING TREND LOWERING HIGH
TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE COOLING TREND WILL
CONTINUE INTO EARLY NEXT WEEK AS A WEATHER DISTURBANCE MOVES ACROSS
ARIZONA BRINGING A CHANCE FOR SHOWERS AS WELL AS AFTERNOON AND
EVENING THUNDERSTORMS MONDAY INTO TUESDAY... MAINLY ACROSS SOUTH
CENTRAL ARIZONA. IT WILL AGAIN TURN DRY WEDNESDAY INTO THE LATTER
HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE UPPER LOW DEVELOPING OVER
THE WESTERN STATES WILL LEAD TO FURTHER COOLING ALONG WITH AN
INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...

NOTE...INCREASED TSTM CHANCES OVER PORTIONS OF SOUTH CENTRAL AZ
WHICH IS A CHANGE IN THE FORECAST FOR TODAY...DETAILS BELOW.

UPPER AIR FEATURES THIS MORNING LOOK SURPRISING DISSIMILAR TO
YESTERDAY...IN FACT ITS MORE UNSTABLE ON THE SOUTH CENTRAL DESERTS
AND MOUNTAINS. LET US EXPLAIN.

WHAT CAUGHT OUR EYE THIS MORNING WAS THE 35 KT 500 MB SOUTH WIND ON
THE TUS SOUNDING AND 5 KNOTS AT SAN DIEGO. A DISTURBANCE? YOU
DECIDE. 300 MB WINDS WERE ALSO CYCLONIC IN THE PLOT DATA AS A
WESTERLY JET MAX FROM THE PACIFIC CUTS ACROSS BAJA CA/NW MEX JUST
SOUTH OF THE BORDER TODAY (SEE VAPOR IMAGERY). ADDITIONALLY...PRECIP
WATER (PW) IMAGERY AS WELL AS WX BALLOON SOUNDINGS SHOWED AN
INCREASE IN PW...IN SOME SOUTHEAST AZ AREAS...SIGNIFICANTLY. 12Z WX
BALLOON SOUNDINGS AS WELL AS MODELED SOUNDINGS SHOW CONVECTIVE
TRIGGER TEMPS WILL BE MET TODAY IN SOME OF OUR HIGHER ELEVATION
AREAS INCLUDING NORTHWEST MARICOPA...SOUTHERN GILA...NORTHEAST
MARICOPA...AND PARTS OF NORTHERN PINAL COUNTIES. IN LIGHT OF THIS
NEW MORNING INFORMATION...WE WOULD BE REMISS NOT SO CHANGE THE
FORECASTS FROM SINGLE DIGIT NEAR ZERO POPS TO AT LEAST A SLIGHT
CHANCE IN THE LOWER ELEVATIONS...AND A CHANCE IN THE HIGHER
ELEVATIONS OF SOUTHERN GILA COUNTY. CONVECTIVE STEERING CURRENTS
WILL BE FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST THIS AFTERNOON...AND
LACK OF APPRECIABLE BOUNDARY LAYER MOISTURE WILL PRECLUDE BACK-
BUILDING CONVECTIVE STORMS...MORE HIGH BASED GUSTY WIND TYPES
REPLETE WITH SOME BLOWING DUST ON THE DESERTS.

CONVECTIVE THREATS WILL END THIS EVENING OR AFTER DARK. THERE WILL
BE NO UPDATES TO SUNDAYS FORECAST.

&&

.PREVIOUS DISCUSSION...245 AM MST...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH CENTRAL AND EASTERN
AZ BOTH DAYS. OTHERWISE WE CAN EXPECT GENLY SUNNY SKIES BOTH DAYS
WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY TAPER OFF. BY
SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL MOSTLY INTO THE
MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ/CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 021658 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
958 AM MST SAT MAY 2 2015

.UPDATE...TO AVIATION DISCUSSION...

&&

.SYNOPSIS...
DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS WEEKEND...AND WE
WILL SEE THE START OF A GRADUAL COOLING TREND LOWERING HIGH
TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE COOLING TREND WILL
CONTINUE INTO EARLY NEXT WEEK AS A WEATHER DISTURBANCE MOVES ACROSS
ARIZONA BRINGING A CHANCE FOR SHOWERS AS WELL AS AFTERNOON AND
EVENING THUNDERSTORMS MONDAY INTO TUESDAY... MAINLY ACROSS SOUTH
CENTRAL ARIZONA. IT WILL AGAIN TURN DRY WEDNESDAY INTO THE LATTER
HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE UPPER LOW DEVELOPING OVER
THE WESTERN STATES WILL LEAD TO FURTHER COOLING ALONG WITH AN
INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...

NOTE...INCREASED TSTM CHANCES OVER PORTIONS OF SOUTH CENTRAL AZ
WHICH IS A CHANGE IN THE FORECAST FOR TODAY...DETAILS BELOW.

UPPER AIR FEATURES THIS MORNING LOOK SURPRISING DISSIMILAR TO
YESTERDAY...IN FACT ITS MORE UNSTABLE ON THE SOUTH CENTRAL DESERTS
AND MOUNTAINS. LET US EXPLAIN.

WHAT CAUGHT OUR EYE THIS MORNING WAS THE 35 KT 500 MB SOUTH WIND ON
THE TUS SOUNDING AND 5 KNOTS AT SAN DIEGO. A DISTURBANCE? YOU
DECIDE. 300 MB WINDS WERE ALSO CYCLONIC IN THE PLOT DATA AS A
WESTERLY JET MAX FROM THE PACIFIC CUTS ACROSS BAJA CA/NW MEX JUST
SOUTH OF THE BORDER TODAY (SEE VAPOR IMAGERY). ADDITIONALLY...PRECIP
WATER (PW) IMAGERY AS WELL AS WX BALLOON SOUNDINGS SHOWED AN
INCREASE IN PW...IN SOME SOUTHEAST AZ AREAS...SIGNIFICANTLY. 12Z WX
BALLOON SOUNDINGS AS WELL AS MODELED SOUNDINGS SHOW CONVECTIVE
TRIGGER TEMPS WILL BE MET TODAY IN SOME OF OUR HIGHER ELEVATION
AREAS INCLUDING NORTHWEST MARICOPA...SOUTHERN GILA...NORTHEAST
MARICOPA...AND PARTS OF NORTHERN PINAL COUNTIES. IN LIGHT OF THIS
NEW MORNING INFORMATION...WE WOULD BE REMISS NOT SO CHANGE THE
FORECASTS FROM SINGLE DIGIT NEAR ZERO POPS TO AT LEAST A SLIGHT
CHANCE IN THE LOWER ELEVATIONS...AND A CHANCE IN THE HIGHER
ELEVATIONS OF SOUTHERN GILA COUNTY. CONVECTIVE STEERING CURRENTS
WILL BE FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST THIS AFTERNOON...AND
LACK OF APPRECIABLE BOUNDARY LAYER MOISTURE WILL PRECLUDE BACK-
BUILDING CONVECTIVE STORMS...MORE HIGH BASED GUSTY WIND TYPES
REPLETE WITH SOME BLOWING DUST ON THE DESERTS.

CONVECTIVE THREATS WILL END THIS EVENING OR AFTER DARK. THERE WILL
BE NO UPDATES TO SUNDAYS FORECAST.

&&

.PREVIOUS DISCUSSION...245 AM MST...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH CENTRAL AND EASTERN
AZ BOTH DAYS. OTHERWISE WE CAN EXPECT GENLY SUNNY SKIES BOTH DAYS
WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY TAPER OFF. BY
SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL MOSTLY INTO THE
MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ/CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 021658 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
958 AM MST SAT MAY 2 2015

.UPDATE...TO AVIATION DISCUSSION...

&&

.SYNOPSIS...
DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS WEEKEND...AND WE
WILL SEE THE START OF A GRADUAL COOLING TREND LOWERING HIGH
TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE COOLING TREND WILL
CONTINUE INTO EARLY NEXT WEEK AS A WEATHER DISTURBANCE MOVES ACROSS
ARIZONA BRINGING A CHANCE FOR SHOWERS AS WELL AS AFTERNOON AND
EVENING THUNDERSTORMS MONDAY INTO TUESDAY... MAINLY ACROSS SOUTH
CENTRAL ARIZONA. IT WILL AGAIN TURN DRY WEDNESDAY INTO THE LATTER
HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE UPPER LOW DEVELOPING OVER
THE WESTERN STATES WILL LEAD TO FURTHER COOLING ALONG WITH AN
INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...

NOTE...INCREASED TSTM CHANCES OVER PORTIONS OF SOUTH CENTRAL AZ
WHICH IS A CHANGE IN THE FORECAST FOR TODAY...DETAILS BELOW.

UPPER AIR FEATURES THIS MORNING LOOK SURPRISING DISSIMILAR TO
YESTERDAY...IN FACT ITS MORE UNSTABLE ON THE SOUTH CENTRAL DESERTS
AND MOUNTAINS. LET US EXPLAIN.

WHAT CAUGHT OUR EYE THIS MORNING WAS THE 35 KT 500 MB SOUTH WIND ON
THE TUS SOUNDING AND 5 KNOTS AT SAN DIEGO. A DISTURBANCE? YOU
DECIDE. 300 MB WINDS WERE ALSO CYCLONIC IN THE PLOT DATA AS A
WESTERLY JET MAX FROM THE PACIFIC CUTS ACROSS BAJA CA/NW MEX JUST
SOUTH OF THE BORDER TODAY (SEE VAPOR IMAGERY). ADDITIONALLY...PRECIP
WATER (PW) IMAGERY AS WELL AS WX BALLOON SOUNDINGS SHOWED AN
INCREASE IN PW...IN SOME SOUTHEAST AZ AREAS...SIGNIFICANTLY. 12Z WX
BALLOON SOUNDINGS AS WELL AS MODELED SOUNDINGS SHOW CONVECTIVE
TRIGGER TEMPS WILL BE MET TODAY IN SOME OF OUR HIGHER ELEVATION
AREAS INCLUDING NORTHWEST MARICOPA...SOUTHERN GILA...NORTHEAST
MARICOPA...AND PARTS OF NORTHERN PINAL COUNTIES. IN LIGHT OF THIS
NEW MORNING INFORMATION...WE WOULD BE REMISS NOT SO CHANGE THE
FORECASTS FROM SINGLE DIGIT NEAR ZERO POPS TO AT LEAST A SLIGHT
CHANCE IN THE LOWER ELEVATIONS...AND A CHANCE IN THE HIGHER
ELEVATIONS OF SOUTHERN GILA COUNTY. CONVECTIVE STEERING CURRENTS
WILL BE FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST THIS AFTERNOON...AND
LACK OF APPRECIABLE BOUNDARY LAYER MOISTURE WILL PRECLUDE BACK-
BUILDING CONVECTIVE STORMS...MORE HIGH BASED GUSTY WIND TYPES
REPLETE WITH SOME BLOWING DUST ON THE DESERTS.

CONVECTIVE THREATS WILL END THIS EVENING OR AFTER DARK. THERE WILL
BE NO UPDATES TO SUNDAYS FORECAST.

&&

.PREVIOUS DISCUSSION...245 AM MST...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH CENTRAL AND EASTERN
AZ BOTH DAYS. OTHERWISE WE CAN EXPECT GENLY SUNNY SKIES BOTH DAYS
WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY TAPER OFF. BY
SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL MOSTLY INTO THE
MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ/CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 021658 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
958 AM MST SAT MAY 2 2015

.UPDATE...TO AVIATION DISCUSSION...

&&

.SYNOPSIS...
DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS WEEKEND...AND WE
WILL SEE THE START OF A GRADUAL COOLING TREND LOWERING HIGH
TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE COOLING TREND WILL
CONTINUE INTO EARLY NEXT WEEK AS A WEATHER DISTURBANCE MOVES ACROSS
ARIZONA BRINGING A CHANCE FOR SHOWERS AS WELL AS AFTERNOON AND
EVENING THUNDERSTORMS MONDAY INTO TUESDAY... MAINLY ACROSS SOUTH
CENTRAL ARIZONA. IT WILL AGAIN TURN DRY WEDNESDAY INTO THE LATTER
HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE UPPER LOW DEVELOPING OVER
THE WESTERN STATES WILL LEAD TO FURTHER COOLING ALONG WITH AN
INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...

NOTE...INCREASED TSTM CHANCES OVER PORTIONS OF SOUTH CENTRAL AZ
WHICH IS A CHANGE IN THE FORECAST FOR TODAY...DETAILS BELOW.

UPPER AIR FEATURES THIS MORNING LOOK SURPRISING DISSIMILAR TO
YESTERDAY...IN FACT ITS MORE UNSTABLE ON THE SOUTH CENTRAL DESERTS
AND MOUNTAINS. LET US EXPLAIN.

WHAT CAUGHT OUR EYE THIS MORNING WAS THE 35 KT 500 MB SOUTH WIND ON
THE TUS SOUNDING AND 5 KNOTS AT SAN DIEGO. A DISTURBANCE? YOU
DECIDE. 300 MB WINDS WERE ALSO CYCLONIC IN THE PLOT DATA AS A
WESTERLY JET MAX FROM THE PACIFIC CUTS ACROSS BAJA CA/NW MEX JUST
SOUTH OF THE BORDER TODAY (SEE VAPOR IMAGERY). ADDITIONALLY...PRECIP
WATER (PW) IMAGERY AS WELL AS WX BALLOON SOUNDINGS SHOWED AN
INCREASE IN PW...IN SOME SOUTHEAST AZ AREAS...SIGNIFICANTLY. 12Z WX
BALLOON SOUNDINGS AS WELL AS MODELED SOUNDINGS SHOW CONVECTIVE
TRIGGER TEMPS WILL BE MET TODAY IN SOME OF OUR HIGHER ELEVATION
AREAS INCLUDING NORTHWEST MARICOPA...SOUTHERN GILA...NORTHEAST
MARICOPA...AND PARTS OF NORTHERN PINAL COUNTIES. IN LIGHT OF THIS
NEW MORNING INFORMATION...WE WOULD BE REMISS NOT SO CHANGE THE
FORECASTS FROM SINGLE DIGIT NEAR ZERO POPS TO AT LEAST A SLIGHT
CHANCE IN THE LOWER ELEVATIONS...AND A CHANCE IN THE HIGHER
ELEVATIONS OF SOUTHERN GILA COUNTY. CONVECTIVE STEERING CURRENTS
WILL BE FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST THIS AFTERNOON...AND
LACK OF APPRECIABLE BOUNDARY LAYER MOISTURE WILL PRECLUDE BACK-
BUILDING CONVECTIVE STORMS...MORE HIGH BASED GUSTY WIND TYPES
REPLETE WITH SOME BLOWING DUST ON THE DESERTS.

CONVECTIVE THREATS WILL END THIS EVENING OR AFTER DARK. THERE WILL
BE NO UPDATES TO SUNDAYS FORECAST.

&&

.PREVIOUS DISCUSSION...245 AM MST...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH CENTRAL AND EASTERN
AZ BOTH DAYS. OTHERWISE WE CAN EXPECT GENLY SUNNY SKIES BOTH DAYS
WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY TAPER OFF. BY
SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL MOSTLY INTO THE
MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
FOR THE REST OF THE AM...DIURNAL WINDS TO CONTINUE WITH SCT TO BKN
CLOUDS HOLDING IN THE 10-20KFT RANGE. INCREASE IN BOUNDARY LAYER
MOISTURE BROUGHT INTO THE AREA BY A VIGOROUS PACIFIC SHORTWAVE WILL
INCREASE AFTN/EARLY EVE THUNDERSHOWER COVERAGE OVER THE AZ HIGHER
TERRAIN. STORM ACTIVITY SHOULD BE CLOSER TO THE PHOENIX METRO
PERIPHERY WITH SOME RECENT HI-RES MODEL FCSTS INDICATING THE EASTERN
SATELLITE TERMINALS LIKE KIWA...KFFZ AND KSDL STAND CHANCES OF AT
LEAST SEEING A BRUSH PASS OF THICK CU/CB DECKS...STORM OUTFLOW WINDS
AND ANY BLOWING DUST ACCOMPANYING THEM. WILL INTRODUCE A WINDOW OF
VCTS FOR KIWA WITH THE 18Z TAFS AND CONTINUE TO MONITOR SATELLITE
RADAR TRENDS FOR ADDITIONAL VCTS INCLUSION IN THE KPHX AND KSDL
TAFS. ANY WX RADAR ACTIVITY SHOULD DIMINISH AFTER SUNSET...WITH SOME
FEW-SCT HIGH LEVEL CLOUDS LINGERING OVERNIGHT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH PRESSURE AT THE SFC TO KEEP WINDS MAINLY ON THE LIGHT SIDE
THROUGH THE TAF PERIOD...EXCEPT AT KBLH...WHERE S-LY BREEZES WILL
LIKELY RISE INTO THE 12-15 KT RANGE DURING THE LATE AFTERNOON/EARLY
EVENING HOURS ON SATURDAY. DRYING SOUTHWEST FLOW ALOFT WILL KEEP
SKIES GENERALLY CLEAR OVER THE WESTERN TERMINALS THROUGH SUN AM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ/CB
AVIATION...NOLTE/PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 021538
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
837 AM MST SAT MAY 2 2015

.SYNOPSIS... DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS
WEEKEND...AND WE WILL SEE THE START OF A GRADUAL COOLING TREND
LOWERING HIGH TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE
COOLING TREND WILL CONTINUE INTO EARLY NEXT WEEK AS A WEATHER
DISTURBANCE MOVES ACROSS ARIZONA BRINGING A CHANCE FOR SHOWERS AS
WELL AS AFTERNOON AND EVENING THUNDERSTORMS MONDAY INTO TUESDAY...
MAINLY ACROSS SOUTH CENTRAL ARIZONA. IT WILL AGAIN TURN DRY
WEDNESDAY INTO THE LATTER HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE
UPPER LOW DEVELOPING OVER THE WESTERN STATES WILL LEAD TO FURTHER
COOLING ALONG WITH AN INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...

.NOTE...INCREASED TSTM CHANCES OVER PORTIONS OF SOUTH CENTRAL AZ
WHICH IS A CHANGE IN THE FORECAST FOR TODAY...DETAILS BELOW.

UPPER AIR FEATURES THIS MORNING LOOK SURPRISING DISSIMILAR TO
YESTERDAY...INFACT ITS MORE UNSTABLE ON THE SOUTH CENTRAL DESERTS
AND MOUNTAINS. LET US EXPLAIN.

WHAT CAUGHT OUR EYE THIS MORNING WAS THE 35 KT 500 MB SOUTH WIND ON
THE TUS SOUNDING AND 5 KNOTS AT SAN DIEGO. A DISTURBANCE? YOU
DECIDE. 300 MB WINDS WERE ALSO CYCLONIC IN THE PLOT DATA AS A
WESTERLY JET MAX FROM THE PACIFIC CUTS ACROSS BAJA CA/NW MEX JUST
SOUTH OF THE BORDER TODAY (SEE VAPOR IMAGERY). ADDITIONALLY...PRECIP
WATER (PW) IMAGERY AS WELL AS WX BALLOON SOUNDINGS SHOWED AN
INCREASE IN PW...IN SOME SOUTHEAST AZ AREAS...SIGNIFICANTLY. 12Z WX
BALLOON SOUNDINGS AS WELL AS MODELED SOUNDINGS SHOW CONVECTIVE
TRIGGER TEMPS WILL BE MET TODAY IN SOME OF OUR HIGHER ELEVATION
AREAS INCLUDING NORTHWEST MARICOPA...SOUTHERN GILA...NORTHEAST
MARICOPA...AND PARTS OF NORTHERN PINAL COUNTIES. IN LIGHT OF THIS
NEW MORNING INFORMATION...WE WOULD BE REMIS NOT SO CHANGE THE
FORECASTS FROM SINGLE DIGIT NEAR ZERO POPS TO AT LEAST A SLIGHT
CHANCE IN THE LOWER ELEVATIONS...AND A CHANCE IN THE HIGHER
ELEVATIONS OF SOUTHERN GILA COUNTY. CONVECTIVE STEERING CURRENTS
WILL BE FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST THIS AFTERNOON...AND
LACK OF APPRECIABLE BOUNDARY LAYER MOISTURE WILL PRECLUDE BACK-
BUILDING CONVECTIVE STORMS...MORE HIGH BASED GUSTY WIND TYPES
REPLETE WITH SOME BLOWING DUST ON THE DESERTS.

CONVECTIVE THREATS WILL END THIS EVENING OR AFTER DARK. THERE WILL
BE NO UPDATES TO SUNDAYS FORECAST.

.PREVIOUS DISCUSSION...245 AM MST...

STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH CENTRAL AND EASTERN
AZ BOTH DAYS. OTHERWISE WE CAN EXPECT GENLY SUNNY SKIES BOTH DAYS
WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY TAPER OFF. BY
SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL MOSTLY INTO THE
MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE AT THE SFC...AND WEAK SFC PRESSURE GRADIENTS TO KEEP
WINDS MAINLY ON THE LIGHT SIDE THROUGH THE TAF PERIOD...EXCEPT AT
KBLH...WHERE S-LY BREEZES WILL LIKELY RISE INTO THE 12-15 KT RANGE
DURING THE LATE AFTERNOON/EARLY EVENING HOURS ON SATURDAY. AS FAR AS
CLOUD COVER IS CONCERNED...LIGHT SW-LY FLOW WILL CONTINUE TO PUSH
SCT-BKN CIRRUS LAYERS OVER THE TERMINALS THROUGH SUNDAY...WITH A FEW
PUFFY CU ALSO DEVELOPING OVER THE PHX AREA TERMINALS FOR A TIME LATE
SAT AFT/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ/CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA





000
FXUS65 KPSR 021538
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
837 AM MST SAT MAY 2 2015

.SYNOPSIS... DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS
WEEKEND...AND WE WILL SEE THE START OF A GRADUAL COOLING TREND
LOWERING HIGH TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE
COOLING TREND WILL CONTINUE INTO EARLY NEXT WEEK AS A WEATHER
DISTURBANCE MOVES ACROSS ARIZONA BRINGING A CHANCE FOR SHOWERS AS
WELL AS AFTERNOON AND EVENING THUNDERSTORMS MONDAY INTO TUESDAY...
MAINLY ACROSS SOUTH CENTRAL ARIZONA. IT WILL AGAIN TURN DRY
WEDNESDAY INTO THE LATTER HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE
UPPER LOW DEVELOPING OVER THE WESTERN STATES WILL LEAD TO FURTHER
COOLING ALONG WITH AN INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...

.NOTE...INCREASED TSTM CHANCES OVER PORTIONS OF SOUTH CENTRAL AZ
WHICH IS A CHANGE IN THE FORECAST FOR TODAY...DETAILS BELOW.

UPPER AIR FEATURES THIS MORNING LOOK SURPRISING DISSIMILAR TO
YESTERDAY...INFACT ITS MORE UNSTABLE ON THE SOUTH CENTRAL DESERTS
AND MOUNTAINS. LET US EXPLAIN.

WHAT CAUGHT OUR EYE THIS MORNING WAS THE 35 KT 500 MB SOUTH WIND ON
THE TUS SOUNDING AND 5 KNOTS AT SAN DIEGO. A DISTURBANCE? YOU
DECIDE. 300 MB WINDS WERE ALSO CYCLONIC IN THE PLOT DATA AS A
WESTERLY JET MAX FROM THE PACIFIC CUTS ACROSS BAJA CA/NW MEX JUST
SOUTH OF THE BORDER TODAY (SEE VAPOR IMAGERY). ADDITIONALLY...PRECIP
WATER (PW) IMAGERY AS WELL AS WX BALLOON SOUNDINGS SHOWED AN
INCREASE IN PW...IN SOME SOUTHEAST AZ AREAS...SIGNIFICANTLY. 12Z WX
BALLOON SOUNDINGS AS WELL AS MODELED SOUNDINGS SHOW CONVECTIVE
TRIGGER TEMPS WILL BE MET TODAY IN SOME OF OUR HIGHER ELEVATION
AREAS INCLUDING NORTHWEST MARICOPA...SOUTHERN GILA...NORTHEAST
MARICOPA...AND PARTS OF NORTHERN PINAL COUNTIES. IN LIGHT OF THIS
NEW MORNING INFORMATION...WE WOULD BE REMIS NOT SO CHANGE THE
FORECASTS FROM SINGLE DIGIT NEAR ZERO POPS TO AT LEAST A SLIGHT
CHANCE IN THE LOWER ELEVATIONS...AND A CHANCE IN THE HIGHER
ELEVATIONS OF SOUTHERN GILA COUNTY. CONVECTIVE STEERING CURRENTS
WILL BE FROM SOUTH-SOUTHWEST TO NORTH-NORTHEAST THIS AFTERNOON...AND
LACK OF APPRECIABLE BOUNDARY LAYER MOISTURE WILL PRECLUDE BACK-
BUILDING CONVECTIVE STORMS...MORE HIGH BASED GUSTY WIND TYPES
REPLETE WITH SOME BLOWING DUST ON THE DESERTS.

CONVECTIVE THREATS WILL END THIS EVENING OR AFTER DARK. THERE WILL
BE NO UPDATES TO SUNDAYS FORECAST.

.PREVIOUS DISCUSSION...245 AM MST...

STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF SOUTH CENTRAL AND EASTERN
AZ BOTH DAYS. OTHERWISE WE CAN EXPECT GENLY SUNNY SKIES BOTH DAYS
WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY TAPER OFF. BY
SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL MOSTLY INTO THE
MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE AT THE SFC...AND WEAK SFC PRESSURE GRADIENTS TO KEEP
WINDS MAINLY ON THE LIGHT SIDE THROUGH THE TAF PERIOD...EXCEPT AT
KBLH...WHERE S-LY BREEZES WILL LIKELY RISE INTO THE 12-15 KT RANGE
DURING THE LATE AFTERNOON/EARLY EVENING HOURS ON SATURDAY. AS FAR AS
CLOUD COVER IS CONCERNED...LIGHT SW-LY FLOW WILL CONTINUE TO PUSH
SCT-BKN CIRRUS LAYERS OVER THE TERMINALS THROUGH SUNDAY...WITH A FEW
PUFFY CU ALSO DEVELOPING OVER THE PHX AREA TERMINALS FOR A TIME LATE
SAT AFT/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..VASQUEZ/CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA




000
FXUS65 KPSR 020945
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
245 AM MST SAT MAY 2 2015

.SYNOPSIS... DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS
WEEKEND...AND WE WILL SEE THE START OF A GRADUAL COOLING TREND
LOWERING HIGH TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE
COOLING TREND WILL CONTINUE INTO EARLY NEXT WEEK AS A WEATHER
DISTURBANCE MOVES ACROSS ARIZONA BRINGING A CHANCE FOR SHOWERS AS
WELL AS AFTERNOON AND EVENING THUNDERSTORMS MONDAY INTO TUESDAY...
MAINLY ACROSS SOUTH CENTRAL ARIZONA. IT WILL AGAIN TURN DRY
WEDNESDAY INTO THE LATTER HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE
UPPER LOW DEVELOPING OVER THE WESTERN STATES WILL LEAD TO FURTHER
COOLING ALONG WITH AN INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF EASTERN AZ BOTH DAYS...
MAINLY AREAS TO THE EAST OF GLOBE. OTHERWISE WE CAN EXPECT GENLY
SUNNY SKIES BOTH DAYS WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY
TAPER OFF. BY SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL
MOSTLY INTO THE MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE AT THE SFC...AND WEAK SFC PRESSURE GRADIENTS TO KEEP
WINDS MAINLY ON THE LIGHT SIDE THROUGH THE TAF PERIOD...EXCEPT AT
KBLH...WHERE S-LY BREEZES WILL LIKELY RISE INTO THE 12-15 KT RANGE
DURING THE LATE AFTERNOON/EARLY EVENING HOURS ON SATURDAY. AS FAR AS
CLOUD COVER IS CONCERNED...LIGHT SW-LY FLOW WILL CONTINUE TO PUSH
SCT-BKN CIRRUS LAYERS OVER THE TERMINALS THROUGH SUNDAY...WITH A FEW
PUFFY CU ALSO DEVELOPING OVER THE PHX AREA TERMINALS FOR A TIME LATE
SAT AFT/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..CB
AVIATION...PERCHA
WEATHER...PERCHA





000
FXUS65 KPSR 020945
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
245 AM MST SAT MAY 2 2015

.SYNOPSIS... DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS
WEEKEND...AND WE WILL SEE THE START OF A GRADUAL COOLING TREND
LOWERING HIGH TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE
COOLING TREND WILL CONTINUE INTO EARLY NEXT WEEK AS A WEATHER
DISTURBANCE MOVES ACROSS ARIZONA BRINGING A CHANCE FOR SHOWERS AS
WELL AS AFTERNOON AND EVENING THUNDERSTORMS MONDAY INTO TUESDAY...
MAINLY ACROSS SOUTH CENTRAL ARIZONA. IT WILL AGAIN TURN DRY
WEDNESDAY INTO THE LATTER HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE
UPPER LOW DEVELOPING OVER THE WESTERN STATES WILL LEAD TO FURTHER
COOLING ALONG WITH AN INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF EASTERN AZ BOTH DAYS...
MAINLY AREAS TO THE EAST OF GLOBE. OTHERWISE WE CAN EXPECT GENLY
SUNNY SKIES BOTH DAYS WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY
TAPER OFF. BY SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL
MOSTLY INTO THE MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE AT THE SFC...AND WEAK SFC PRESSURE GRADIENTS TO KEEP
WINDS MAINLY ON THE LIGHT SIDE THROUGH THE TAF PERIOD...EXCEPT AT
KBLH...WHERE S-LY BREEZES WILL LIKELY RISE INTO THE 12-15 KT RANGE
DURING THE LATE AFTERNOON/EARLY EVENING HOURS ON SATURDAY. AS FAR AS
CLOUD COVER IS CONCERNED...LIGHT SW-LY FLOW WILL CONTINUE TO PUSH
SCT-BKN CIRRUS LAYERS OVER THE TERMINALS THROUGH SUNDAY...WITH A FEW
PUFFY CU ALSO DEVELOPING OVER THE PHX AREA TERMINALS FOR A TIME LATE
SAT AFT/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..CB
AVIATION...PERCHA
WEATHER...PERCHA




000
FXUS65 KPSR 020945
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
245 AM MST SAT MAY 2 2015

.SYNOPSIS... DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS
WEEKEND...AND WE WILL SEE THE START OF A GRADUAL COOLING TREND
LOWERING HIGH TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE
COOLING TREND WILL CONTINUE INTO EARLY NEXT WEEK AS A WEATHER
DISTURBANCE MOVES ACROSS ARIZONA BRINGING A CHANCE FOR SHOWERS AS
WELL AS AFTERNOON AND EVENING THUNDERSTORMS MONDAY INTO TUESDAY...
MAINLY ACROSS SOUTH CENTRAL ARIZONA. IT WILL AGAIN TURN DRY
WEDNESDAY INTO THE LATTER HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE
UPPER LOW DEVELOPING OVER THE WESTERN STATES WILL LEAD TO FURTHER
COOLING ALONG WITH AN INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF EASTERN AZ BOTH DAYS...
MAINLY AREAS TO THE EAST OF GLOBE. OTHERWISE WE CAN EXPECT GENLY
SUNNY SKIES BOTH DAYS WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY
TAPER OFF. BY SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL
MOSTLY INTO THE MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE AT THE SFC...AND WEAK SFC PRESSURE GRADIENTS TO KEEP
WINDS MAINLY ON THE LIGHT SIDE THROUGH THE TAF PERIOD...EXCEPT AT
KBLH...WHERE S-LY BREEZES WILL LIKELY RISE INTO THE 12-15 KT RANGE
DURING THE LATE AFTERNOON/EARLY EVENING HOURS ON SATURDAY. AS FAR AS
CLOUD COVER IS CONCERNED...LIGHT SW-LY FLOW WILL CONTINUE TO PUSH
SCT-BKN CIRRUS LAYERS OVER THE TERMINALS THROUGH SUNDAY...WITH A FEW
PUFFY CU ALSO DEVELOPING OVER THE PHX AREA TERMINALS FOR A TIME LATE
SAT AFT/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..CB
AVIATION...PERCHA
WEATHER...PERCHA




000
FXUS65 KPSR 020945
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
245 AM MST SAT MAY 2 2015

.SYNOPSIS... DRY SOUTHWEST FLOW ALOFT WILL AFFECT THE AREA THIS
WEEKEND...AND WE WILL SEE THE START OF A GRADUAL COOLING TREND
LOWERING HIGH TEMPERATURES INTO THE MIDDLE 90S BY SUNDAY. THE
COOLING TREND WILL CONTINUE INTO EARLY NEXT WEEK AS A WEATHER
DISTURBANCE MOVES ACROSS ARIZONA BRINGING A CHANCE FOR SHOWERS AS
WELL AS AFTERNOON AND EVENING THUNDERSTORMS MONDAY INTO TUESDAY...
MAINLY ACROSS SOUTH CENTRAL ARIZONA. IT WILL AGAIN TURN DRY
WEDNESDAY INTO THE LATTER HALF OF NEXT WORK WEEK...ALTHOUGH A LARGE
UPPER LOW DEVELOPING OVER THE WESTERN STATES WILL LEAD TO FURTHER
COOLING ALONG WITH AN INCREASE IN AFTERNOON BREEZINESS.

&&

.DISCUSSION...
STRONG HIGH PRESSURE ALOFT...WITH H5 HEIGHTS RUNNING AROUND 581DM
OVER THE SRN ARIZONA DESERTS...LED TO THE FIRST 100 DEGREE READING
OF THE YEAR AT PHOENIX YESTERDAY. HOWEVER...THE RIDGE WILL SLOWLY
ERODE AND SHIFT OFF TO THE EAST THIS WEEKEND AS WEAK SHORT WAVE
ENERGY MOVES INLAND OFF SRN CA/NRN BAJA AND INTO THE DESERT
SOUTHWEST. MODEST AMOUNTS OF MID LEVEL MOISTURE HAVE ALREADY SPREAD
INTO THE AREA...VISIBLE ON THE LATEST 00Z ARIZONA SOUNDINGS...AND WE
WILL CONTINUE TO SEE ISOLATED AFTERNOON AND EARLY EVENING HIGH BASED
THUNDERSTORMS OVER THE HIGHER TERRAIN OF EASTERN AZ BOTH DAYS...
MAINLY AREAS TO THE EAST OF GLOBE. OTHERWISE WE CAN EXPECT GENLY
SUNNY SKIES BOTH DAYS WITH A MODEST COOLING TREND AS HEIGHTS SLOWLY
TAPER OFF. BY SUNDAY...HIGH TEMPS OVER THE SRN DESERTS WILL FALL
MOSTLY INTO THE MIDDLE RANGE OF THE 90S.

MODEL GUIDANCE REMAINS VERY CONSISTENT IN CALLING FOR A WEAK UPPER
LOW TO MOVE INTO ARIZONA FROM OFF THE SRN CA/NRN BAJA COAST IN THE
MONDAY THROUGH TUESDAY TIME FRAME. ALTHOUGH THIS WILL BE A RATHER
WEAK AND PROGRESSIVE SYSTEM WITH LIMITED DYNAMICS AND QG
FORCING...THERE WILL BE DECENT AMOUNTS OF MOISTURE AT PLAY WITH PWAT
VALUES RISING TO AROUND 1 INCH. IT WILL ALSO BE AN UNSTABLE SYSTEM
WITH LIFTED INDICES AT LEAST MINUS 2 AND CAPE VALUES OF AROUND 500-
600 J/KG. AS SUCH WE ARE LOOKING AT ISOLATED TO SCATTERED SHOWERS
AND THUNDERSTORMS DEVELOPING MONDAY AND CONTINUING THROUGH MONDAY
NIGHT...WITH THE BEST CHANCES FOR PRECIP ACROSS SOUTH CENTRAL
ARIZONA. POPS OVER THE HIGHER TERRAIN EAST OF PHOENIX WILL EXCEED 40
PERCENT. DUE TO INCREASING CONFIDENCE...AND MRA POPS AT PHOENIX
CONSISTENTLY BETWEEN 30 AND 50 PERCENT FOR MONDAY NIGHT...WE HAVE
RAISED POPS AROUND 10 PERCENT OVER THE CENTRAL DESERTS WITH PHOENIX
RISING ABOVE 30 PERCENT MONDAY AFTERNOON AND EVENING. BY TUESDAY
AFTERNOON...AS THE TROF AXIS LIFTS OUT TO THE EAST OF PHOENIX...POPS
WILL FALL INTO THE SLIGHT CHANCE CATEGORY OVER THE CENTRAL DESERTS
WITH MOSTLY SUNNY SKIES EXPECTED WEST OF MARICOPA COUNTY. THERE WILL
REMAIN A LINGERING CHANCE FOR SHOWERS/STORMS ACROSS THE HIGHER
TERRAIN EAST OF PHOENIX INTO TUESDAY EVENING HOWEVER. THE
CLOUDS/SHOWERS AND THICKNESS COOLING WILL CAUSE HIGH TEMPS MONDAY
AND TUESDAY TO FALL BELOW SEASONAL NORMALS AND INTO THE 80S OVER THE
CENTRAL DESERTS. EXPECT A HIGH AROUND 87 BOTH DAYS AT PHOENIX UNDER
PARTLY SUNNY SKIES.

DRY WEST TO SOUTHWEST FLOW WILL OVERSPREAD THE AREA WEDNESDAY FOR
MOSTLY SUNNY SKIES...AND VERY SLIGHT WARMING. HIGH TEMPS OVER THE
LOWER DESERTS WILL STAY MOSTLY IN THE 80S HOWEVER...JUST SLIGHTLY
BELOW NORMALS.

THE MODEL INCONSISTENCIES THAT WERE DISPLAYED YESTERDAY HAVE MORE OR
LESS RESOLVED THEMSELVES...AND NOW WE ARE LOOKING AT A SOLUTION MORE
IN LINE WITH YESTERDAYS GFS. THAT IS...A LARGE UPPER LOW WILL SET UP
OVER THE WESTERN CONUS DURING THE LATTER PORTION OF NEXT WORK WEEK.
THE CENTER OF THE LOW IS FORECAST TO STAY WELL TO THE NORTHWEST OF
PHOENIX...KEEPING THE SOUTHERN DESERTS ON THE SOUTHERN FRINGES OF
THE LOW AND UNDER A DRY WESTERLY FLOW ALOFT. AS SUCH NO PRECIP IS
EXPECTED ACROSS OUR AREA NEXT THURSDAY AND FRIDAY. WE WILL SEE
TEMPERATURES FALLING OFF SEVERAL DEGREES HOWEVER...AND DOWN INTO THE
MIDDLE 80S BY FRIDAY. ALSO...THERE WILL BE AN INCREASE IN AFTERNOON
BREEZINESS EACH DAY...AND WITH LOW SURFACE RH THERE MAY BE FIRE
WEATHER CONCERNS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE AT THE SFC...AND WEAK SFC PRESSURE GRADIENTS TO KEEP
WINDS MAINLY ON THE LIGHT SIDE THROUGH THE TAF PERIOD...EXCEPT AT
KBLH...WHERE S-LY BREEZES WILL LIKELY RISE INTO THE 12-15 KT RANGE
DURING THE LATE AFTERNOON/EARLY EVENING HOURS ON SATURDAY. AS FAR AS
CLOUD COVER IS CONCERNED...LIGHT SW-LY FLOW WILL CONTINUE TO PUSH
SCT-BKN CIRRUS LAYERS OVER THE TERMINALS THROUGH SUNDAY...WITH A FEW
PUFFY CU ALSO DEVELOPING OVER THE PHX AREA TERMINALS FOR A TIME LATE
SAT AFT/EARLY EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF LATE-SEASON STORM SYSTEMS TO BRING COOLER TEMPS TO THE
REGION DURING THE UPCOMING WEEK...WITH HIGHS REMAINING NEAR...OR
SLIGHTLY BELOW NORMAL EACH DAY. THE 1ST STORM CENTER WILL ALSO BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS TO THE REGION ON MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. THE 2ND STORM CENTER TO
BRING AN INCREASE IN CLOUDINESS AND WINDS TO THE REGION ON WEDNESDAY
AND THURSDAY. THE COMBINATION OF THESE STRONGER WINDS...AND
AFTERNOON HUMIDITIES IN THE TEENS WILL DEFINITELY ALLOW FIRE DANGER
LEVELS TO RISE DURING THIS PERIOD. OTHERWISE...AFTERNOON HUMIDITIES
ARE EXPECTED TO FALL INTO THE 15-30 PERCENT RANGE ON MONDAY AND
TUESDAY...AND AGAIN ON FRIDAY.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION..CB
AVIATION...PERCHA
WEATHER...PERCHA





000
FXUS65 KPSR 020352
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
852 PM MST FRI MAY 1 2015

.SYNOPSIS...
UNUSUALLY WARM WEATHER WILL CONTINUE INTO THE WEEKEND...WITH MANY
DESERT LOCATIONS ONCE AGAIN AROUND TRIPLE DIGITS TODAY. TEMPERATURES
WILL COOL SLIGHTLY LATER IN THE WEEKEND AND EARLY NEXT WEEK AS A
WEATHER DISTURBANCE NEARS THE AREA. THIS WEATHER SYSTEM MAY ALSO
LEAD TO A FEW SHOWERS FOR HIGHER ELEVATION AREAS...WITH EVEN COOLER
TEMPERATURES IN ITS WAKE DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
ISOLATED SHOWERS ACROSS THE HIGHER TERRAIN LOCATIONS OF ARIZONA
CONTINUE TO DIMINISH THIS EVENING WITH THE LOSS OF DAYTIME HEATING.
STILL SOME CLOUD COVER IN PLACE ACROSS THE REGION ALTHOUGH MOST OF
THIS IS JUST SOME THIN CIRRUS. FOLLOWING ANOTHER WARM
AFTERNOON...TEMPERATURES HAVE BEEN SLOW TO RETREAT THIS
EVENING...WITH MOST DESERT LOCATIONS STILL IN THE UPPER 80S/LOWER 90S
AS OF 0350Z.

LOOKING THROUGH THE INHERITED FORECAST...EVERYTHING APPEARS ON TRACK.
WILL MAKE MINOR ADJUSTMENTS TO THE HOURLY TEMPS/DEWPOINTS/WINDS TO
CAPTURE TRENDS THROUGH THE OVERNIGHT HOURS BUT BOTTOM-LINE...WE
SHOULD BE LOOKING AT ANOTHER MILD NIGHT WITH LOWS BOTTOMING OUT IN
THE MID 60S TO LOWER 70S.

&&

.PREVIOUS DISCUSSION...
ANOTHER ABOVE AVERAGE AFTERNOON UNDERWAY ACROSS THE SOUTH-CENTRAL
ARIZONA AND SOUTHEAST CALIFORNIA DESERTS...WITH PHOENIX SKY HARBOR
OFFICIALLY HITTING 100F FOR THE FIRST TIME THIS YEAR EARLIER DURING
THE 2 PM MST HOUR. OTHER SITES AROUND THE AREA SUCH AS YUMA AND
BLYTHE ARE CLOSE IF NOT OVER THE 100F MARK AS WELL. UPPER LEVEL HIGH
PRESSURE...THE DRIVER IN GETTING US TO THE 100F MARK...HAS SLOWLY
TRANSITIONED TOWARDS TO AZ/NM STATE LINE. THE WARM ATMOSPHERE AND
THIN LAYER OF MOISTURE WORKING DOWN FROM THE FOUR CORNERS AREA HAS
SUPPORTING WIDELY SCATTERED THUNDERSTORM DEVELOPMENT ALONG THE I-40
CORRIDOR EAST OF FLAGSTAFF AND DOWN THROUGH A PORTION OF THE WHITE
MOUNTAINS. SATELLITE IMAGERY LOOPS FROM THE AFTERNOON SHOWS STORM
TOPS AND OVERALL STORM MOTION MOVING NORTHEASTWARD...SO OUTSIDE OF
SOME BUILD-UPS ON THE HORIZON... CONDITIONS OVER THE SOUTH-CENTRAL
DESERTS WILL STAY ON THE DRY SIDE TONIGHT. MEANWHILE...FURTHER OUT
WEST...SKIES WERE SLOWLY CLEARING FROM THE EARLIER PASSING CLOUDS.

WILL STILL LOOK FOR FURTHER WEAKENING FROM THE RIDGE AS IT FULLY
TRANSITIONS OUT THE AREA LATER TONIGHT INTO SATURDAY. THIS IS IN
RESPONSE TO A SERIES OF WEATHER DISTURBANCES MOVING THROUGH THE AREA
FROM OFF THE PACIFIC...THE FIRST DUE THROUGH THE AREA THIS WEEKEND.
A BIT OF MID LEVEL MOISTURE WILL FEED INLAND AS WELL ALLOWING FOR
SOME AFTERNOON BUILDUPS OVER THE WHITE MOUNTAINS EACH DAY...ALTHOUGH
NO THUNDERSTORMS SHOULD DEVELOP OVER SOUTHERN GILA COUNTY THROUGH
SUNDAY EVENING. MODEL PWATS GENERALLY PEAK AROUND 0.80 INCH DURING
THIS TIME. WITH THE POTENTIAL FOR INCREASED MOISTURE IN THE FORM OF
HIGHER DEWPOINTS AND CLOUD COVER ALONG WITH LOWERING UPPER LEVEL
HEIGHTS...HIGH TEMPERATURES WILL START TO DROP AND BY SUNDAY
AFTERNOON THE WARMER DESERTS WILL SEE READINGS MAINLY IN THE MIDDLE
RANGE OF THE 90S UNDER CONTINUED SUNNY SKIES.

LATEST GFS AND ECMWF ARE IN GOOD AGREEMENT FOR THE MIDDLE PORTION OF
THE FORECAST AND BOTH CALL FOR A RATHER PROGRESSIVE UPPER LOW TO
SWING INLAND FROM OFF THE SRN CA/NRN BAJA COAST AND MOVE ACROSS
ARIZONA DURING THE MONDAY THROUGH TUESDAY TIME FRAME. PWAT VALUES
ARE FORECAST TO CLIMB TO NEARLY ONE INCH OVER THE LOWER
DESERTS...AND LIFTED INDICES LOWER BELOW MINUS 2. THIS IS NOT AN
ESPECIALLY DYNAMIC LOW AND DYNAMICS/Q FORCING ARE NOT OVERLY
IMPRESSIVE. STILL...WE WILL SEE A SLIGHT CHANCE FOR
AFTERNOON/EVENING SHOWERS OR STORMS OVER THE LOWER DESERTS MONDAY
AFTERNOON AND EVENING...WITH CHANCES ACROSS THE HIGHER TERRAIN EAST
OF PHOENIX. THICKNESS COOLING ALONG WITH INCREASED CLOUD COVER
SHOULD ALLOW HIGH TEMPS TO NEAR OR SLIGHTLY BELOW SEASONAL NORMAL
VALUES MONDAY INTO TUESDAY. PHOENIX IS EXPECTED TO SEE A HIGH IN THE
UPPER 80S TUESDAY...2-3 DEGREES BELOW NORMAL. BY TUESDAY AFTERNOON
THE LOW WILL EXIT INTO NEW MEXICO LEAVING A LINGERING SLIGHT CHANCE
FOR SHOWERS/STORMS OVER SOUTH CENTRAL ARIZONA...WITH SKIES ACROSS
THE DESERTS WEST OF PHOENIX CLEARING AND BECOMING MOSTLY SUNNY.

FOR THE END OF THE EXTENDED FORECAST...WEDNESDAY INTO THURSDAY...GFS
AND ECMWF START TO DIVERGE RADICALLY ALTHOUGH BOTH SOLUTIONS WOULD
LEAD TO DRY CONDITIONS ACROSS THE AREA AS A WESTERLY FLOW ALOFT SETS
UP. MAIN DIFFERENCES WOULD BE WITH RESPECT TO WIND AND
TEMPERATURES...BY THURSDAY AFTERNOON THE GFS FORECASTS A HUGE WOUND
UP CLOSED LOW SITUATED OVER THE WESTERN CONUS...CENTERED OVER
CENTRAL CA/CENTRAL NV. H5 HEIGHTS OVER PHOENIX ARE FORECAST TO BE
AROUND 566DM. AT THE SAME TIME THE ECMWF CALLS FOR A BROAD UPPER
RIDGE TO MOVE IN AND SET UP ALONG THE PAC NW COAST GIVING A DRY
NORTHWEST FLOW ALOFT TO THE AREA...WITH H5 HEIGHTS RUNNING AROUND
574DM OVER PHOENIX. IN SHORT THE GFS SOLUTION WOULD BE MUCH WINDIER
AND COOLER...THE MEX MOS FOR PHOENIX NEXT THURSDAY CALLS FOR 81
DEGREES VERSUS A FORECAST OF 92 FROM THE ECE MOS FROM THE EUROPEAN.

CONFIDENCE IN THE BOWLING BALL LOW SOLUTION THE GFS PRESENTS IS
EXTREMELY LOW...DUE TO SEVERAL FACTORS INCLUDING CLIMATOLOGY...POOR
PAST MODEL PERFORMANCE WITH LARGE CLOSED LOWS BEYOND DAY 5...HIGH
SPREAD IN THE GFS ENSEMBLE MEMBERS...AND TYPICALLY BETTER LONG RANGE
PERFORMANCE WITH THE ECMWF. THUS WILL HEDGE OUR TEMP AND WIND
FORECASTS FOR WED/THU CLOSER TO THE ECMWF SOLUTION...AND FORECAST
CENTRAL DESERTS HIGHS IN THE MID TO UPPER 80S BOTH DAYS UNDER SUNNY
SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

JUST SOME HIGH CLOUDS ACROSS THE AREA OVERNIGHT. COULD BE A FEW CU
ACROSS THE DESERTS /MAINLY TO THE NORTH AND EAST/ SATURDAY AFTERNOON
BUT NOTHING OF ANY CONSEQUENCE. AS FOR WINDS...LIGHT/DIURNALLY DRIVEN
TRENDS WILL DOMINATE THROUGH SATURDAY NIGHT.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A MORE ACTIVE UPPER STORM TRACK WILL WORK THROUGH THE REGION FOR THE
EARLY PART OF THE WEEK...ALLOWING TEMPERATURES TO COOL DOWN TO
NEAR...OR EVEN SLIGHTLY BELOW NORMAL THROUGH THE FORECAST PERIOD.
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL RESULT FOR MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. AFTERNOON HUMIDITIES IN A
15 TO 25 PERCENT RANGE FROM SUNDAY THROUGH TUESDAY TO FALL INTO THE
10-20 PERCENT RANGE ON WEDNESDAY AND THURSDAY...WITH FAIR TO GOOD
OVERNIGHT RECOVERIES. WINDS WILL GENERALLY BE LIGHT AND
DIURNAL...THOUGH BREEZY CONDITIONS ARE POSSIBLE TUESDAY AND
WEDNESDAY AFTERNOON. FOR THE LATTER PART OF THE WEEK MEDIUM-RANGE
FORECAST MODELS INDICATE A LARGER AND MUCH COOLER STORM SYSTEM WILL
DEVELOP INTO THE GREAT BASIN AND SOUTHWEST STATES. HOWEVER...MODELS
HAVE ONLY RECENTLY BEGUN TO ADVERTISE AND AGREE ON THIS SOLUTION.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/NOLTE/CB
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA




000
FXUS65 KPSR 020352
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
852 PM MST FRI MAY 1 2015

.SYNOPSIS...
UNUSUALLY WARM WEATHER WILL CONTINUE INTO THE WEEKEND...WITH MANY
DESERT LOCATIONS ONCE AGAIN AROUND TRIPLE DIGITS TODAY. TEMPERATURES
WILL COOL SLIGHTLY LATER IN THE WEEKEND AND EARLY NEXT WEEK AS A
WEATHER DISTURBANCE NEARS THE AREA. THIS WEATHER SYSTEM MAY ALSO
LEAD TO A FEW SHOWERS FOR HIGHER ELEVATION AREAS...WITH EVEN COOLER
TEMPERATURES IN ITS WAKE DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
ISOLATED SHOWERS ACROSS THE HIGHER TERRAIN LOCATIONS OF ARIZONA
CONTINUE TO DIMINISH THIS EVENING WITH THE LOSS OF DAYTIME HEATING.
STILL SOME CLOUD COVER IN PLACE ACROSS THE REGION ALTHOUGH MOST OF
THIS IS JUST SOME THIN CIRRUS. FOLLOWING ANOTHER WARM
AFTERNOON...TEMPERATURES HAVE BEEN SLOW TO RETREAT THIS
EVENING...WITH MOST DESERT LOCATIONS STILL IN THE UPPER 80S/LOWER 90S
AS OF 0350Z.

LOOKING THROUGH THE INHERITED FORECAST...EVERYTHING APPEARS ON TRACK.
WILL MAKE MINOR ADJUSTMENTS TO THE HOURLY TEMPS/DEWPOINTS/WINDS TO
CAPTURE TRENDS THROUGH THE OVERNIGHT HOURS BUT BOTTOM-LINE...WE
SHOULD BE LOOKING AT ANOTHER MILD NIGHT WITH LOWS BOTTOMING OUT IN
THE MID 60S TO LOWER 70S.

&&

.PREVIOUS DISCUSSION...
ANOTHER ABOVE AVERAGE AFTERNOON UNDERWAY ACROSS THE SOUTH-CENTRAL
ARIZONA AND SOUTHEAST CALIFORNIA DESERTS...WITH PHOENIX SKY HARBOR
OFFICIALLY HITTING 100F FOR THE FIRST TIME THIS YEAR EARLIER DURING
THE 2 PM MST HOUR. OTHER SITES AROUND THE AREA SUCH AS YUMA AND
BLYTHE ARE CLOSE IF NOT OVER THE 100F MARK AS WELL. UPPER LEVEL HIGH
PRESSURE...THE DRIVER IN GETTING US TO THE 100F MARK...HAS SLOWLY
TRANSITIONED TOWARDS TO AZ/NM STATE LINE. THE WARM ATMOSPHERE AND
THIN LAYER OF MOISTURE WORKING DOWN FROM THE FOUR CORNERS AREA HAS
SUPPORTING WIDELY SCATTERED THUNDERSTORM DEVELOPMENT ALONG THE I-40
CORRIDOR EAST OF FLAGSTAFF AND DOWN THROUGH A PORTION OF THE WHITE
MOUNTAINS. SATELLITE IMAGERY LOOPS FROM THE AFTERNOON SHOWS STORM
TOPS AND OVERALL STORM MOTION MOVING NORTHEASTWARD...SO OUTSIDE OF
SOME BUILD-UPS ON THE HORIZON... CONDITIONS OVER THE SOUTH-CENTRAL
DESERTS WILL STAY ON THE DRY SIDE TONIGHT. MEANWHILE...FURTHER OUT
WEST...SKIES WERE SLOWLY CLEARING FROM THE EARLIER PASSING CLOUDS.

WILL STILL LOOK FOR FURTHER WEAKENING FROM THE RIDGE AS IT FULLY
TRANSITIONS OUT THE AREA LATER TONIGHT INTO SATURDAY. THIS IS IN
RESPONSE TO A SERIES OF WEATHER DISTURBANCES MOVING THROUGH THE AREA
FROM OFF THE PACIFIC...THE FIRST DUE THROUGH THE AREA THIS WEEKEND.
A BIT OF MID LEVEL MOISTURE WILL FEED INLAND AS WELL ALLOWING FOR
SOME AFTERNOON BUILDUPS OVER THE WHITE MOUNTAINS EACH DAY...ALTHOUGH
NO THUNDERSTORMS SHOULD DEVELOP OVER SOUTHERN GILA COUNTY THROUGH
SUNDAY EVENING. MODEL PWATS GENERALLY PEAK AROUND 0.80 INCH DURING
THIS TIME. WITH THE POTENTIAL FOR INCREASED MOISTURE IN THE FORM OF
HIGHER DEWPOINTS AND CLOUD COVER ALONG WITH LOWERING UPPER LEVEL
HEIGHTS...HIGH TEMPERATURES WILL START TO DROP AND BY SUNDAY
AFTERNOON THE WARMER DESERTS WILL SEE READINGS MAINLY IN THE MIDDLE
RANGE OF THE 90S UNDER CONTINUED SUNNY SKIES.

LATEST GFS AND ECMWF ARE IN GOOD AGREEMENT FOR THE MIDDLE PORTION OF
THE FORECAST AND BOTH CALL FOR A RATHER PROGRESSIVE UPPER LOW TO
SWING INLAND FROM OFF THE SRN CA/NRN BAJA COAST AND MOVE ACROSS
ARIZONA DURING THE MONDAY THROUGH TUESDAY TIME FRAME. PWAT VALUES
ARE FORECAST TO CLIMB TO NEARLY ONE INCH OVER THE LOWER
DESERTS...AND LIFTED INDICES LOWER BELOW MINUS 2. THIS IS NOT AN
ESPECIALLY DYNAMIC LOW AND DYNAMICS/Q FORCING ARE NOT OVERLY
IMPRESSIVE. STILL...WE WILL SEE A SLIGHT CHANCE FOR
AFTERNOON/EVENING SHOWERS OR STORMS OVER THE LOWER DESERTS MONDAY
AFTERNOON AND EVENING...WITH CHANCES ACROSS THE HIGHER TERRAIN EAST
OF PHOENIX. THICKNESS COOLING ALONG WITH INCREASED CLOUD COVER
SHOULD ALLOW HIGH TEMPS TO NEAR OR SLIGHTLY BELOW SEASONAL NORMAL
VALUES MONDAY INTO TUESDAY. PHOENIX IS EXPECTED TO SEE A HIGH IN THE
UPPER 80S TUESDAY...2-3 DEGREES BELOW NORMAL. BY TUESDAY AFTERNOON
THE LOW WILL EXIT INTO NEW MEXICO LEAVING A LINGERING SLIGHT CHANCE
FOR SHOWERS/STORMS OVER SOUTH CENTRAL ARIZONA...WITH SKIES ACROSS
THE DESERTS WEST OF PHOENIX CLEARING AND BECOMING MOSTLY SUNNY.

FOR THE END OF THE EXTENDED FORECAST...WEDNESDAY INTO THURSDAY...GFS
AND ECMWF START TO DIVERGE RADICALLY ALTHOUGH BOTH SOLUTIONS WOULD
LEAD TO DRY CONDITIONS ACROSS THE AREA AS A WESTERLY FLOW ALOFT SETS
UP. MAIN DIFFERENCES WOULD BE WITH RESPECT TO WIND AND
TEMPERATURES...BY THURSDAY AFTERNOON THE GFS FORECASTS A HUGE WOUND
UP CLOSED LOW SITUATED OVER THE WESTERN CONUS...CENTERED OVER
CENTRAL CA/CENTRAL NV. H5 HEIGHTS OVER PHOENIX ARE FORECAST TO BE
AROUND 566DM. AT THE SAME TIME THE ECMWF CALLS FOR A BROAD UPPER
RIDGE TO MOVE IN AND SET UP ALONG THE PAC NW COAST GIVING A DRY
NORTHWEST FLOW ALOFT TO THE AREA...WITH H5 HEIGHTS RUNNING AROUND
574DM OVER PHOENIX. IN SHORT THE GFS SOLUTION WOULD BE MUCH WINDIER
AND COOLER...THE MEX MOS FOR PHOENIX NEXT THURSDAY CALLS FOR 81
DEGREES VERSUS A FORECAST OF 92 FROM THE ECE MOS FROM THE EUROPEAN.

CONFIDENCE IN THE BOWLING BALL LOW SOLUTION THE GFS PRESENTS IS
EXTREMELY LOW...DUE TO SEVERAL FACTORS INCLUDING CLIMATOLOGY...POOR
PAST MODEL PERFORMANCE WITH LARGE CLOSED LOWS BEYOND DAY 5...HIGH
SPREAD IN THE GFS ENSEMBLE MEMBERS...AND TYPICALLY BETTER LONG RANGE
PERFORMANCE WITH THE ECMWF. THUS WILL HEDGE OUR TEMP AND WIND
FORECASTS FOR WED/THU CLOSER TO THE ECMWF SOLUTION...AND FORECAST
CENTRAL DESERTS HIGHS IN THE MID TO UPPER 80S BOTH DAYS UNDER SUNNY
SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

JUST SOME HIGH CLOUDS ACROSS THE AREA OVERNIGHT. COULD BE A FEW CU
ACROSS THE DESERTS /MAINLY TO THE NORTH AND EAST/ SATURDAY AFTERNOON
BUT NOTHING OF ANY CONSEQUENCE. AS FOR WINDS...LIGHT/DIURNALLY DRIVEN
TRENDS WILL DOMINATE THROUGH SATURDAY NIGHT.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A MORE ACTIVE UPPER STORM TRACK WILL WORK THROUGH THE REGION FOR THE
EARLY PART OF THE WEEK...ALLOWING TEMPERATURES TO COOL DOWN TO
NEAR...OR EVEN SLIGHTLY BELOW NORMAL THROUGH THE FORECAST PERIOD.
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL RESULT FOR MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. AFTERNOON HUMIDITIES IN A
15 TO 25 PERCENT RANGE FROM SUNDAY THROUGH TUESDAY TO FALL INTO THE
10-20 PERCENT RANGE ON WEDNESDAY AND THURSDAY...WITH FAIR TO GOOD
OVERNIGHT RECOVERIES. WINDS WILL GENERALLY BE LIGHT AND
DIURNAL...THOUGH BREEZY CONDITIONS ARE POSSIBLE TUESDAY AND
WEDNESDAY AFTERNOON. FOR THE LATTER PART OF THE WEEK MEDIUM-RANGE
FORECAST MODELS INDICATE A LARGER AND MUCH COOLER STORM SYSTEM WILL
DEVELOP INTO THE GREAT BASIN AND SOUTHWEST STATES. HOWEVER...MODELS
HAVE ONLY RECENTLY BEGUN TO ADVERTISE AND AGREE ON THIS SOLUTION.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...LEINS/NOLTE/CB
AVIATION...LEINS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 012240
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
340 PM MST FRI MAY 1 2015

.SYNOPSIS...
UNUSUALLY WARM WEATHER WILL CONTINUE INTO THE WEEKEND...WITH MANY
DESERT LOCATIONS ONCE AGAIN AROUND TRIPLE DIGITS TODAY. TEMPERATURES
WILL COOL SLIGHTLY LATER IN THE WEEKEND AND EARLY NEXT WEEK AS A
WEATHER DISTURBANCE NEARS THE AREA. THIS WEATHER SYSTEM MAY ALSO
LEAD TO A FEW SHOWERS FOR HIGHER ELEVATION AREAS...WITH EVEN COOLER
TEMPERATURES IN ITS WAKE DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
ANOTHER ABOVE AVERAGE AFTERNOON UNDERWAY ACROSS THE SOUTH-CENTRAL
ARIZONA AND SOUTHEAST CALIFORNIA DESERTS...WITH PHOENIX SKY HARBOR
OFFICIALLY HITTING 100F FOR THE FIRST TIME THIS YEAR EARLIER DURING
THE 2 PM MST HOUR. OTHER SITES AROUND THE AREA SUCH AS YUMA AND
BLYTHE ARE CLOSE IF NOT OVER THE 100F MARK AS WELL. UPPER LEVEL HIGH
PRESSURE...THE DRIVER IN GETTING US TO THE 100F MARK...HAS SLOWLY
TRANSITIONED TOWARDS TO AZ/NM STATE LINE. THE WARM ATMOSPHERE AND
THIN LAYER OF MOISTURE WORKING DOWN FROM THE FOUR CORNERS AREA HAS
SUPPORTING WIDELY SCATTERED THUNDERSTORM DEVELOPMENT ALONG THE I-40
CORRIDOR EAST OF FLAGSTAFF AND DOWN THROUGH A PORTION OF THE WHITE
MOUNTAINS. SATELLITE IMAGERY LOOPS FROM THE AFTERNOON SHOWS STORM
TOPS AND OVERALL STORM MOTION MOVING NORTHEASTWARD...SO OUTSIDE OF
SOME BUILD-UPS ON THE HORIZON... CONDITIONS OVER THE SOUTH-CENTRAL
DESERTS WILL STAY ON THE DRY SIDE TONIGHT. MEANWHILE...FURTHER OUT
WEST...SKIES WERE SLOWLY CLEARING FROM THE EARLIER PASSING CLOUDS.

WILL STILL LOOK FOR FURTHER WEAKENING FROM THE RIDGE AS IT FULLY
TRANSITIONS OUT THE AREA LATER TONIGHT INTO SATURDAY. THIS IS IN
RESPONSE TO A SERIES OF WEATHER DISTURBANCES MOVING THROUGH THE AREA
FROM OFF THE PACIFIC...THE FIRST DUE THROUGH THE AREA THIS WEEKEND.
A BIT OF MID LEVEL MOISTURE WILL FEED INLAND AS WELL ALLOWING FOR
SOME AFTERNOON BUILDUPS OVER THE WHITE MOUNTAINS EACH DAY...ALTHOUGH
NO THUNDERSTORMS SHOULD DEVELOP OVER SOUTHERN GILA COUNTY THROUGH
SUNDAY EVENING. MODEL PWATS GENERALLY PEAK AROUND 0.80 INCH DURING
THIS TIME. WITH THE POTENTIAL FOR INCREASED MOISTURE IN THE FORM OF
HIGHER DEWPOINTS AND CLOUD COVER ALONG WITH LOWERING UPPER LEVEL
HEIGHTS...HIGH TEMPERATURES WILL START TO DROP AND BY SUNDAY
AFTERNOON THE WARMER DESERTS WILL SEE READINGS MAINLY IN THE MIDDLE
RANGE OF THE 90S UNDER CONTINUED SUNNY SKIES.

LATEST GFS AND ECMWF ARE IN GOOD AGREEMENT FOR THE MIDDLE PORTION OF
THE FORECAST AND BOTH CALL FOR A RATHER PROGRESSIVE UPPER LOW TO
SWING INLAND FROM OFF THE SRN CA/NRN BAJA COAST AND MOVE ACROSS
ARIZONA DURING THE MONDAY THROUGH TUESDAY TIME FRAME. PWAT VALUES
ARE FORECAST TO CLIMB TO NEARLY ONE INCH OVER THE LOWER
DESERTS...AND LIFTED INDICES LOWER BELOW MINUS 2. THIS IS NOT AN
ESPECIALLY DYNAMIC LOW AND DYNAMICS/Q FORCING ARE NOT OVERLY
IMPRESSIVE. STILL...WE WILL SEE A SLIGHT CHANCE FOR
AFTERNOON/EVENING SHOWERS OR STORMS OVER THE LOWER DESERTS MONDAY
AFTERNOON AND EVENING...WITH CHANCES ACROSS THE HIGHER TERRAIN EAST
OF PHOENIX. THICKNESS COOLING ALONG WITH INCREASED CLOUD COVER
SHOULD ALLOW HIGH TEMPS TO NEAR OR SLIGHTLY BELOW SEASONAL NORMAL
VALUES MONDAY INTO TUESDAY. PHOENIX IS EXPECTED TO SEE A HIGH IN THE
UPPER 80S TUESDAY...2-3 DEGREES BELOW NORMAL. BY TUESDAY AFTERNOON
THE LOW WILL EXIT INTO NEW MEXICO LEAVING A LINGERING SLIGHT CHANCE
FOR SHOWERS/STORMS OVER SOUTH CENTRAL ARIZONA...WITH SKIES ACROSS
THE DESERTS WEST OF PHOENIX CLEARING AND BECOMING MOSTLY SUNNY.

FOR THE END OF THE EXTENDED FORECAST...WEDNESDAY INTO THURSDAY...GFS
AND ECMWF START TO DIVERGE RADICALLY ALTHOUGH BOTH SOLUTIONS WOULD
LEAD TO DRY CONDITIONS ACROSS THE AREA AS A WESTERLY FLOW ALOFT SETS
UP. MAIN DIFFERENCES WOULD BE WITH RESPECT TO WIND AND
TEMPERATURES...BY THURSDAY AFTERNOON THE GFS FORECASTS A HUGE WOUND
UP CLOSED LOW SITUATED OVER THE WESTERN CONUS...CENTERED OVER
CENTRAL CA/CENTRAL NV. H5 HEIGHTS OVER PHOENIX ARE FORECAST TO BE
AROUND 566DM. AT THE SAME TIME THE ECMWF CALLS FOR A BROAD UPPER
RIDGE TO MOVE IN AND SET UP ALONG THE PAC NW COAST GIVING A DRY
NORTHWEST FLOW ALOFT TO THE AREA...WITH H5 HEIGHTS RUNNING AROUND
574DM OVER PHOENIX. IN SHORT THE GFS SOLUTION WOULD BE MUCH WINDIER
AND COOLER...THE MEX MOS FOR PHOENIX NEXT THURSDAY CALLS FOR 81
DEGREES VERSUS A FORECAST OF 92 FROM THE ECE MOS FROM THE EUROPEAN.

CONFIDENCE IN THE BOWLING BALL LOW SOLUTION THE GFS PRESENTS IS
EXTREMELY LOW...DUE TO SEVERAL FACTORS INCLUDING CLIMATOLOGY...POOR
PAST MODEL PERFORMANCE WITH LARGE CLOSED LOWS BEYOND DAY 5...HIGH
SPREAD IN THE GFS ENSEMBLE MEMBERS...AND TYPICALLY BETTER LONG RANGE
PERFORMANCE WITH THE ECMWF. THUS WILL HEDGE OUR TEMP AND WIND
FORECASTS FOR WED/THU CLOSER TO THE ECMWF SOLUTION...AND FORECAST
CENTRAL DESERTS HIGHS IN THE MID TO UPPER 80S BOTH DAYS UNDER SUNNY
SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

WESTERLY WINDS OVER KPHX...KIWA...AND KSDL WILL CONTINUE UNTIL 03Z
THIS AFTERNOON...5 TO 15 KTS THEN TURNING MORE LGT AND VRB
OVERNIGHT. KIPL AND KBLH WITH LGT SOUTHERLY WINDS. SOME PASSING HIGH
CLOUDS WILL CONTINUE ACROSS THE ENTIRE REGION FOR THE NEXT 6 HRS BUT
WILL PRIMARILY BE FEW TO SCT.

NO AVIATION CONCERNS EXPECTED OVER THE NEXT 24 HRS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A MORE ACTIVE UPPER STORM TRACK WILL WORK THROUGH THE REGION FOR THE
EARLY PART OF THE WEEK...ALLOWING TEMPERATURES TO COOL DOWN TO
NEAR...OR EVEN SLIGHTLY BELOW NORMAL THROUGH THE FORECAST PERIOD.
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL RESULT FOR MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. AFTERNOON HUMIDITIES IN A
15 TO 25 PERCENT RANGE FROM SUNDAY THROUGH TUESDAY TO FALL INTO THE
10-20 PERCENT RANGE ON WEDNESDAY AND THURSDAY...WITH FAIR TO GOOD
OVERNIGHT RECOVERIES. WINDS WILL GENERALLY BE LIGHT AND
DIURNAL...THOUGH BREEZY CONDITIONS ARE POSSIBLE TUESDAY AND
WEDNESDAY AFTERNOON. FOR THE LATTER PART OF THE WEEK MEDIUM-RANGE
FORECAST MODELS INDICATE A LARGER AND MUCH COOLER STORM SYSTEM WILL
DEVELOP INTO THE GREAT BASIN AND SOUTHWEST STATES. HOWEVER...MODELS
HAVE ONLY RECENTLY BEGUN TO ADVERTISE AND AGREE ON THIS SOLUTION.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...NOLTE/CB
AVIATION...WATERS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 012240
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
340 PM MST FRI MAY 1 2015

.SYNOPSIS...
UNUSUALLY WARM WEATHER WILL CONTINUE INTO THE WEEKEND...WITH MANY
DESERT LOCATIONS ONCE AGAIN AROUND TRIPLE DIGITS TODAY. TEMPERATURES
WILL COOL SLIGHTLY LATER IN THE WEEKEND AND EARLY NEXT WEEK AS A
WEATHER DISTURBANCE NEARS THE AREA. THIS WEATHER SYSTEM MAY ALSO
LEAD TO A FEW SHOWERS FOR HIGHER ELEVATION AREAS...WITH EVEN COOLER
TEMPERATURES IN ITS WAKE DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
ANOTHER ABOVE AVERAGE AFTERNOON UNDERWAY ACROSS THE SOUTH-CENTRAL
ARIZONA AND SOUTHEAST CALIFORNIA DESERTS...WITH PHOENIX SKY HARBOR
OFFICIALLY HITTING 100F FOR THE FIRST TIME THIS YEAR EARLIER DURING
THE 2 PM MST HOUR. OTHER SITES AROUND THE AREA SUCH AS YUMA AND
BLYTHE ARE CLOSE IF NOT OVER THE 100F MARK AS WELL. UPPER LEVEL HIGH
PRESSURE...THE DRIVER IN GETTING US TO THE 100F MARK...HAS SLOWLY
TRANSITIONED TOWARDS TO AZ/NM STATE LINE. THE WARM ATMOSPHERE AND
THIN LAYER OF MOISTURE WORKING DOWN FROM THE FOUR CORNERS AREA HAS
SUPPORTING WIDELY SCATTERED THUNDERSTORM DEVELOPMENT ALONG THE I-40
CORRIDOR EAST OF FLAGSTAFF AND DOWN THROUGH A PORTION OF THE WHITE
MOUNTAINS. SATELLITE IMAGERY LOOPS FROM THE AFTERNOON SHOWS STORM
TOPS AND OVERALL STORM MOTION MOVING NORTHEASTWARD...SO OUTSIDE OF
SOME BUILD-UPS ON THE HORIZON... CONDITIONS OVER THE SOUTH-CENTRAL
DESERTS WILL STAY ON THE DRY SIDE TONIGHT. MEANWHILE...FURTHER OUT
WEST...SKIES WERE SLOWLY CLEARING FROM THE EARLIER PASSING CLOUDS.

WILL STILL LOOK FOR FURTHER WEAKENING FROM THE RIDGE AS IT FULLY
TRANSITIONS OUT THE AREA LATER TONIGHT INTO SATURDAY. THIS IS IN
RESPONSE TO A SERIES OF WEATHER DISTURBANCES MOVING THROUGH THE AREA
FROM OFF THE PACIFIC...THE FIRST DUE THROUGH THE AREA THIS WEEKEND.
A BIT OF MID LEVEL MOISTURE WILL FEED INLAND AS WELL ALLOWING FOR
SOME AFTERNOON BUILDUPS OVER THE WHITE MOUNTAINS EACH DAY...ALTHOUGH
NO THUNDERSTORMS SHOULD DEVELOP OVER SOUTHERN GILA COUNTY THROUGH
SUNDAY EVENING. MODEL PWATS GENERALLY PEAK AROUND 0.80 INCH DURING
THIS TIME. WITH THE POTENTIAL FOR INCREASED MOISTURE IN THE FORM OF
HIGHER DEWPOINTS AND CLOUD COVER ALONG WITH LOWERING UPPER LEVEL
HEIGHTS...HIGH TEMPERATURES WILL START TO DROP AND BY SUNDAY
AFTERNOON THE WARMER DESERTS WILL SEE READINGS MAINLY IN THE MIDDLE
RANGE OF THE 90S UNDER CONTINUED SUNNY SKIES.

LATEST GFS AND ECMWF ARE IN GOOD AGREEMENT FOR THE MIDDLE PORTION OF
THE FORECAST AND BOTH CALL FOR A RATHER PROGRESSIVE UPPER LOW TO
SWING INLAND FROM OFF THE SRN CA/NRN BAJA COAST AND MOVE ACROSS
ARIZONA DURING THE MONDAY THROUGH TUESDAY TIME FRAME. PWAT VALUES
ARE FORECAST TO CLIMB TO NEARLY ONE INCH OVER THE LOWER
DESERTS...AND LIFTED INDICES LOWER BELOW MINUS 2. THIS IS NOT AN
ESPECIALLY DYNAMIC LOW AND DYNAMICS/Q FORCING ARE NOT OVERLY
IMPRESSIVE. STILL...WE WILL SEE A SLIGHT CHANCE FOR
AFTERNOON/EVENING SHOWERS OR STORMS OVER THE LOWER DESERTS MONDAY
AFTERNOON AND EVENING...WITH CHANCES ACROSS THE HIGHER TERRAIN EAST
OF PHOENIX. THICKNESS COOLING ALONG WITH INCREASED CLOUD COVER
SHOULD ALLOW HIGH TEMPS TO NEAR OR SLIGHTLY BELOW SEASONAL NORMAL
VALUES MONDAY INTO TUESDAY. PHOENIX IS EXPECTED TO SEE A HIGH IN THE
UPPER 80S TUESDAY...2-3 DEGREES BELOW NORMAL. BY TUESDAY AFTERNOON
THE LOW WILL EXIT INTO NEW MEXICO LEAVING A LINGERING SLIGHT CHANCE
FOR SHOWERS/STORMS OVER SOUTH CENTRAL ARIZONA...WITH SKIES ACROSS
THE DESERTS WEST OF PHOENIX CLEARING AND BECOMING MOSTLY SUNNY.

FOR THE END OF THE EXTENDED FORECAST...WEDNESDAY INTO THURSDAY...GFS
AND ECMWF START TO DIVERGE RADICALLY ALTHOUGH BOTH SOLUTIONS WOULD
LEAD TO DRY CONDITIONS ACROSS THE AREA AS A WESTERLY FLOW ALOFT SETS
UP. MAIN DIFFERENCES WOULD BE WITH RESPECT TO WIND AND
TEMPERATURES...BY THURSDAY AFTERNOON THE GFS FORECASTS A HUGE WOUND
UP CLOSED LOW SITUATED OVER THE WESTERN CONUS...CENTERED OVER
CENTRAL CA/CENTRAL NV. H5 HEIGHTS OVER PHOENIX ARE FORECAST TO BE
AROUND 566DM. AT THE SAME TIME THE ECMWF CALLS FOR A BROAD UPPER
RIDGE TO MOVE IN AND SET UP ALONG THE PAC NW COAST GIVING A DRY
NORTHWEST FLOW ALOFT TO THE AREA...WITH H5 HEIGHTS RUNNING AROUND
574DM OVER PHOENIX. IN SHORT THE GFS SOLUTION WOULD BE MUCH WINDIER
AND COOLER...THE MEX MOS FOR PHOENIX NEXT THURSDAY CALLS FOR 81
DEGREES VERSUS A FORECAST OF 92 FROM THE ECE MOS FROM THE EUROPEAN.

CONFIDENCE IN THE BOWLING BALL LOW SOLUTION THE GFS PRESENTS IS
EXTREMELY LOW...DUE TO SEVERAL FACTORS INCLUDING CLIMATOLOGY...POOR
PAST MODEL PERFORMANCE WITH LARGE CLOSED LOWS BEYOND DAY 5...HIGH
SPREAD IN THE GFS ENSEMBLE MEMBERS...AND TYPICALLY BETTER LONG RANGE
PERFORMANCE WITH THE ECMWF. THUS WILL HEDGE OUR TEMP AND WIND
FORECASTS FOR WED/THU CLOSER TO THE ECMWF SOLUTION...AND FORECAST
CENTRAL DESERTS HIGHS IN THE MID TO UPPER 80S BOTH DAYS UNDER SUNNY
SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

WESTERLY WINDS OVER KPHX...KIWA...AND KSDL WILL CONTINUE UNTIL 03Z
THIS AFTERNOON...5 TO 15 KTS THEN TURNING MORE LGT AND VRB
OVERNIGHT. KIPL AND KBLH WITH LGT SOUTHERLY WINDS. SOME PASSING HIGH
CLOUDS WILL CONTINUE ACROSS THE ENTIRE REGION FOR THE NEXT 6 HRS BUT
WILL PRIMARILY BE FEW TO SCT.

NO AVIATION CONCERNS EXPECTED OVER THE NEXT 24 HRS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A MORE ACTIVE UPPER STORM TRACK WILL WORK THROUGH THE REGION FOR THE
EARLY PART OF THE WEEK...ALLOWING TEMPERATURES TO COOL DOWN TO
NEAR...OR EVEN SLIGHTLY BELOW NORMAL THROUGH THE FORECAST PERIOD.
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL RESULT FOR MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. AFTERNOON HUMIDITIES IN A
15 TO 25 PERCENT RANGE FROM SUNDAY THROUGH TUESDAY TO FALL INTO THE
10-20 PERCENT RANGE ON WEDNESDAY AND THURSDAY...WITH FAIR TO GOOD
OVERNIGHT RECOVERIES. WINDS WILL GENERALLY BE LIGHT AND
DIURNAL...THOUGH BREEZY CONDITIONS ARE POSSIBLE TUESDAY AND
WEDNESDAY AFTERNOON. FOR THE LATTER PART OF THE WEEK MEDIUM-RANGE
FORECAST MODELS INDICATE A LARGER AND MUCH COOLER STORM SYSTEM WILL
DEVELOP INTO THE GREAT BASIN AND SOUTHWEST STATES. HOWEVER...MODELS
HAVE ONLY RECENTLY BEGUN TO ADVERTISE AND AGREE ON THIS SOLUTION.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...NOLTE/CB
AVIATION...WATERS
FIRE WEATHER...NOLTE/PERCHA




000
FXUS65 KPSR 012240
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
340 PM MST FRI MAY 1 2015

.SYNOPSIS...
UNUSUALLY WARM WEATHER WILL CONTINUE INTO THE WEEKEND...WITH MANY
DESERT LOCATIONS ONCE AGAIN AROUND TRIPLE DIGITS TODAY. TEMPERATURES
WILL COOL SLIGHTLY LATER IN THE WEEKEND AND EARLY NEXT WEEK AS A
WEATHER DISTURBANCE NEARS THE AREA. THIS WEATHER SYSTEM MAY ALSO
LEAD TO A FEW SHOWERS FOR HIGHER ELEVATION AREAS...WITH EVEN COOLER
TEMPERATURES IN ITS WAKE DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
ANOTHER ABOVE AVERAGE AFTERNOON UNDERWAY ACROSS THE SOUTH-CENTRAL
ARIZONA AND SOUTHEAST CALIFORNIA DESERTS...WITH PHOENIX SKY HARBOR
OFFICIALLY HITTING 100F FOR THE FIRST TIME THIS YEAR EARLIER DURING
THE 2 PM MST HOUR. OTHER SITES AROUND THE AREA SUCH AS YUMA AND
BLYTHE ARE CLOSE IF NOT OVER THE 100F MARK AS WELL. UPPER LEVEL HIGH
PRESSURE...THE DRIVER IN GETTING US TO THE 100F MARK...HAS SLOWLY
TRANSITIONED TOWARDS TO AZ/NM STATE LINE. THE WARM ATMOSPHERE AND
THIN LAYER OF MOISTURE WORKING DOWN FROM THE FOUR CORNERS AREA HAS
SUPPORTING WIDELY SCATTERED THUNDERSTORM DEVELOPMENT ALONG THE I-40
CORRIDOR EAST OF FLAGSTAFF AND DOWN THROUGH A PORTION OF THE WHITE
MOUNTAINS. SATELLITE IMAGERY LOOPS FROM THE AFTERNOON SHOWS STORM
TOPS AND OVERALL STORM MOTION MOVING NORTHEASTWARD...SO OUTSIDE OF
SOME BUILD-UPS ON THE HORIZON... CONDITIONS OVER THE SOUTH-CENTRAL
DESERTS WILL STAY ON THE DRY SIDE TONIGHT. MEANWHILE...FURTHER OUT
WEST...SKIES WERE SLOWLY CLEARING FROM THE EARLIER PASSING CLOUDS.

WILL STILL LOOK FOR FURTHER WEAKENING FROM THE RIDGE AS IT FULLY
TRANSITIONS OUT THE AREA LATER TONIGHT INTO SATURDAY. THIS IS IN
RESPONSE TO A SERIES OF WEATHER DISTURBANCES MOVING THROUGH THE AREA
FROM OFF THE PACIFIC...THE FIRST DUE THROUGH THE AREA THIS WEEKEND.
A BIT OF MID LEVEL MOISTURE WILL FEED INLAND AS WELL ALLOWING FOR
SOME AFTERNOON BUILDUPS OVER THE WHITE MOUNTAINS EACH DAY...ALTHOUGH
NO THUNDERSTORMS SHOULD DEVELOP OVER SOUTHERN GILA COUNTY THROUGH
SUNDAY EVENING. MODEL PWATS GENERALLY PEAK AROUND 0.80 INCH DURING
THIS TIME. WITH THE POTENTIAL FOR INCREASED MOISTURE IN THE FORM OF
HIGHER DEWPOINTS AND CLOUD COVER ALONG WITH LOWERING UPPER LEVEL
HEIGHTS...HIGH TEMPERATURES WILL START TO DROP AND BY SUNDAY
AFTERNOON THE WARMER DESERTS WILL SEE READINGS MAINLY IN THE MIDDLE
RANGE OF THE 90S UNDER CONTINUED SUNNY SKIES.

LATEST GFS AND ECMWF ARE IN GOOD AGREEMENT FOR THE MIDDLE PORTION OF
THE FORECAST AND BOTH CALL FOR A RATHER PROGRESSIVE UPPER LOW TO
SWING INLAND FROM OFF THE SRN CA/NRN BAJA COAST AND MOVE ACROSS
ARIZONA DURING THE MONDAY THROUGH TUESDAY TIME FRAME. PWAT VALUES
ARE FORECAST TO CLIMB TO NEARLY ONE INCH OVER THE LOWER
DESERTS...AND LIFTED INDICES LOWER BELOW MINUS 2. THIS IS NOT AN
ESPECIALLY DYNAMIC LOW AND DYNAMICS/Q FORCING ARE NOT OVERLY
IMPRESSIVE. STILL...WE WILL SEE A SLIGHT CHANCE FOR
AFTERNOON/EVENING SHOWERS OR STORMS OVER THE LOWER DESERTS MONDAY
AFTERNOON AND EVENING...WITH CHANCES ACROSS THE HIGHER TERRAIN EAST
OF PHOENIX. THICKNESS COOLING ALONG WITH INCREASED CLOUD COVER
SHOULD ALLOW HIGH TEMPS TO NEAR OR SLIGHTLY BELOW SEASONAL NORMAL
VALUES MONDAY INTO TUESDAY. PHOENIX IS EXPECTED TO SEE A HIGH IN THE
UPPER 80S TUESDAY...2-3 DEGREES BELOW NORMAL. BY TUESDAY AFTERNOON
THE LOW WILL EXIT INTO NEW MEXICO LEAVING A LINGERING SLIGHT CHANCE
FOR SHOWERS/STORMS OVER SOUTH CENTRAL ARIZONA...WITH SKIES ACROSS
THE DESERTS WEST OF PHOENIX CLEARING AND BECOMING MOSTLY SUNNY.

FOR THE END OF THE EXTENDED FORECAST...WEDNESDAY INTO THURSDAY...GFS
AND ECMWF START TO DIVERGE RADICALLY ALTHOUGH BOTH SOLUTIONS WOULD
LEAD TO DRY CONDITIONS ACROSS THE AREA AS A WESTERLY FLOW ALOFT SETS
UP. MAIN DIFFERENCES WOULD BE WITH RESPECT TO WIND AND
TEMPERATURES...BY THURSDAY AFTERNOON THE GFS FORECASTS A HUGE WOUND
UP CLOSED LOW SITUATED OVER THE WESTERN CONUS...CENTERED OVER
CENTRAL CA/CENTRAL NV. H5 HEIGHTS OVER PHOENIX ARE FORECAST TO BE
AROUND 566DM. AT THE SAME TIME THE ECMWF CALLS FOR A BROAD UPPER
RIDGE TO MOVE IN AND SET UP ALONG THE PAC NW COAST GIVING A DRY
NORTHWEST FLOW ALOFT TO THE AREA...WITH H5 HEIGHTS RUNNING AROUND
574DM OVER PHOENIX. IN SHORT THE GFS SOLUTION WOULD BE MUCH WINDIER
AND COOLER...THE MEX MOS FOR PHOENIX NEXT THURSDAY CALLS FOR 81
DEGREES VERSUS A FORECAST OF 92 FROM THE ECE MOS FROM THE EUROPEAN.

CONFIDENCE IN THE BOWLING BALL LOW SOLUTION THE GFS PRESENTS IS
EXTREMELY LOW...DUE TO SEVERAL FACTORS INCLUDING CLIMATOLOGY...POOR
PAST MODEL PERFORMANCE WITH LARGE CLOSED LOWS BEYOND DAY 5...HIGH
SPREAD IN THE GFS ENSEMBLE MEMBERS...AND TYPICALLY BETTER LONG RANGE
PERFORMANCE WITH THE ECMWF. THUS WILL HEDGE OUR TEMP AND WIND
FORECASTS FOR WED/THU CLOSER TO THE ECMWF SOLUTION...AND FORECAST
CENTRAL DESERTS HIGHS IN THE MID TO UPPER 80S BOTH DAYS UNDER SUNNY
SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

WESTERLY WINDS OVER KPHX...KIWA...AND KSDL WILL CONTINUE UNTIL 03Z
THIS AFTERNOON...5 TO 15 KTS THEN TURNING MORE LGT AND VRB
OVERNIGHT. KIPL AND KBLH WITH LGT SOUTHERLY WINDS. SOME PASSING HIGH
CLOUDS WILL CONTINUE ACROSS THE ENTIRE REGION FOR THE NEXT 6 HRS BUT
WILL PRIMARILY BE FEW TO SCT.

NO AVIATION CONCERNS EXPECTED OVER THE NEXT 24 HRS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A MORE ACTIVE UPPER STORM TRACK WILL WORK THROUGH THE REGION FOR THE
EARLY PART OF THE WEEK...ALLOWING TEMPERATURES TO COOL DOWN TO
NEAR...OR EVEN SLIGHTLY BELOW NORMAL THROUGH THE FORECAST PERIOD.
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL RESULT FOR MONDAY AND
TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE OVER THE
HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. AFTERNOON HUMIDITIES IN A
15 TO 25 PERCENT RANGE FROM SUNDAY THROUGH TUESDAY TO FALL INTO THE
10-20 PERCENT RANGE ON WEDNESDAY AND THURSDAY...WITH FAIR TO GOOD
OVERNIGHT RECOVERIES. WINDS WILL GENERALLY BE LIGHT AND
DIURNAL...THOUGH BREEZY CONDITIONS ARE POSSIBLE TUESDAY AND
WEDNESDAY AFTERNOON. FOR THE LATTER PART OF THE WEEK MEDIUM-RANGE
FORECAST MODELS INDICATE A LARGER AND MUCH COOLER STORM SYSTEM WILL
DEVELOP INTO THE GREAT BASIN AND SOUTHWEST STATES. HOWEVER...MODELS
HAVE ONLY RECENTLY BEGUN TO ADVERTISE AND AGREE ON THIS SOLUTION.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...NOLTE/CB
AVIATION...WATERS
FIRE WEATHER...NOLTE/PERCHA





000
FXUS65 KPSR 011538
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
838 AM MST FRI MAY 1 2015

.SYNOPSIS...
UNUSUALLY WARM WEATHER WILL CONTINUE INTO THE WEEKEND...WITH MANY
DESERT LOCATIONS ONCE AGAIN AROUND TRIPLE DIGITS TODAY. TEMPERATURES
WILL COOL SLIGHTLY LATER IN THE WEEKEND AND EARLY NEXT WEEK AS A
WEATHER DISTURBANCE NEARS THE AREA. THIS WEATHER SYSTEM MAY ALSO
LEAD TO A FEW SHOWERS FOR HIGHER ELEVATION AREAS...WITH EVEN COOLER
TEMPERATURES IN ITS WAKE DURING THE MIDDLE OF NEXT WEEK.

&&

.DISCUSSION...
ALL EYES...AT LEAST THOSE AROUND THE SOUTH-CENTRAL AZ DESERTS AND
THE METROPOLITAN PHOENIX AREA...WILL BE ON THE AFTERNOON HIGH
TEMPERATURES LATER ON TODAY AS PHOENIX MAKES ANOTHER RUN AT ITS
FIRST 100F DAY OF THE CALENDAR YEAR. SO FAR THIS MORNING...MOST
SITES AROUND THE FORECAST AREA ARE ON PAR OR LITTLE BIT WARMER
COMPARED TO THIS TIME YESTERDAY. UPPER RIDGE CIRCULATION CENTER PER
12Z RAOBS AND STREAMLINE FORECASTS HAS BEGUN TO SHIFT TO OUR EAST
WITH UPPER FLOW ALOFT TRANSITIONING MORE SOUTHERLY OVER THE WESTERN
FORECAST AREA ZONES. SOME AREAS OF MOSTLY HIGH LEVEL
CLOUDS...SATELLITE DERIVED OBS PLOTTING THEM AROUND 25KFT...MOVING
NORTHWARD OVER SOUTHEAST CA AND ALONG THE CO RIVER VALLEY. PATCHES
OF HIGH LEVELS CLOUDS WILL CONTINUE TO DRIFT NORTH-NORTHEASTWARD
THROUGH THE DAY POSSIBLY INTRUDING INTO THE SOUTH-CENTRAL AZ DESERTS
TOWARDS THE LATER AFTERNOON HOURS. CURRENT THINKING THEY WILL NOT BE
THICK ENOUGH TO INHIBIT THE WARMING TO KEEP PHOENIX WORKING TO THE
CENTURY MARK TODAY. BEST PERFORMING GRIDDED TEMPERATURE GUIDANCE AND
MOS OUTPUT ALL POINT 100F FOR PHOENIX AND OTHER LOWER DESERT LOCALES
TODAY. STILL LOOKING AT A SLOW COOL DOWN GOING THROUGH THE WEEKEND
AND EARLY NEXT WEEK AS A PACIFIC SHORTWAVE SKIRTS THE
REGION...IMPORTS SOME MOISTURE AND EVEN SLIGHT CHANCES FOR PRECIP
ACROSS MUCH OF THE AREA TO OPEN UP THE NEXT WORK WEEK. MADE A FEW
MINOR ADJUSTMENTS TO HOURLY TEMP AND SKY GRIDS...OTHERWISE FORECAST
IS IN GOOD SHAPE. REST OF DISCUSSION BELOW STILL APPLIES FOR THE
REST OF THE FORECAST PERIOD.

&&

.PREVIOUS DISCUSSION...
RELATIVELY STRONG UPPER LEVEL HIGH PRESSURE RIDGE REMAINED SITUATED
OVER THE DESERT SOUTHWEST EARLY THIS MORNING... WITH H5 HEIGHTS
RUNNING AROUND 581DM OVER THE SOUTHERN DESERTS. UNDER SUNNY
SKIES...THIS WILL LEAD TO ANOTHER DAY OF UNSEASONABLY WARM HIGH
TEMPERATURES RUNNING AROUND 10 DEGREES ABOVE NORMALS. TODAY WILL
LIKELY BE THE DAY THAT PHOENIX RECORDS THE FIRST 100 DEGREE READING
OF THE YEAR...BUT SHOULD THE MERCURY COME UP SHORT IT WILL LIKELY
TAKE AT LEAST ANOTHER WEEK BEFORE THE CHANCE PRESENTS ITSELF AGAIN
TO REACH THE FIRST 100.

AFTER TODAY...THE RIDGE WILL SLOWLY WEAKEN AND SHIFT EAST AS MINOR
SHORTWAVE ENERGY MOVES INLAND OFF THE SRN CA/NRN BAJA COAST. A BIT
OF MID LEVEL MOISTURE WILL FEED INLAND AS WELL ALLOWING FOR SOME
AFTERNOON BUILDUPS OVER THE WHITE MOUNTAINS EACH DAY...ALTHOUGH NO
THUNDERSTORMS SHOULD DEVELOP OVER SOUTHERN GILA COUNTY THROUGH
SUNDAY EVENING. AS HEIGHTS ALOFT SLOWLY FALL OFF...HIGH TEMPERATURES
WILL START TO DROP AND BY SUNDAY AFTERNOON THE WARMER DESERTS WILL
SEE READINGS MAINLY IN THE MIDDLE RANGE OF THE 90S UNDER CONTINUED
SUNNY SKIES.

LATEST GFS AND ECMWF ARE IN GOOD AGREEMENT FOR THE MIDDLE PORTION OF
THE FORECAST AND BOTH CALL FOR A RATHER PROGRESSIVE UPPER LOW TO
SWING INLAND FROM OFF THE SRN CA/NRN BAJA COAST AND MOVE ACROSS
ARIZONA DURING THE MONDAY THROUGH TUESDAY TIME FRAME. PWAT VALUES
ARE FORECAST TO CLIMB TO NEARLY ONE INCH OVER THE LOWER
DESERTS...AND LIFTED INDICES LOWER BELOW MINUS 2. THIS IS NOT AN
ESPECIALLY DYNAMIC LOW AND DYNAMICS/Q FORCING ARE NOT OVERLY
IMPRESSIVE. STILL...WE WILL SEE A SLIGHT CHANCE FOR
AFTERNOON/EVENING SHOWERS OR STORMS OVER THE LOWER DESERTS MONDAY
AFTERNOON AND EVENING...WITH CHANCES ACROSS THE HIGHER TERRAIN EAST
OF PHOENIX. THICKNESS COOLING ALONG WITH INCREASED CLOUD COVER
SHOULD ALLOW HIGH TEMPS TO NEAR OR SLIGHTLY BELOW SEASONAL NORMAL
VALUES MONDAY INTO TUESDAY. PHOENIX IS EXPECTED TO SEE A HIGH IN THE
UPPER 80S TUESDAY...2-3 DEGREES BELOW NORMAL. BY TUESDAY AFTERNOON
THE LOW WILL EXIT INTO NEW MEXICO LEAVING A LINGERING SLIGHT CHANCE
FOR SHOWERS/STORMS OVER SOUTH CENTRAL ARIZONA...WITH SKIES ACROSS
THE DESERTS WEST OF PHOENIX CLEARING AND BECOMING MOSTLY SUNNY.

FOR THE END OF THE EXTENDED FORECAST...WEDNESDAY INTO THURSDAY...GFS
AND ECMWF START TO DIVERGE RADICALLY ALTHOUGH BOTH SOLUTIONS WOULD
LEAD TO DRY CONDITIONS ACROSS THE AREA AS A WESTERLY FLOW ALOFT SETS
UP. MAIN DIFFERENCES WOULD BE WITH RESPECT TO WIND AND
TEMPERATURES...BY THURSDAY AFTERNOON THE GFS FORECASTS A HUGE WOUND
UP CLOSED LOW SITUATED OVER THE WESTERN CONUS...CENTERED OVER
CENTRAL CA/CENTRAL NV. H5 HEIGHTS OVER PHOENIX ARE FORECAST TO BE
AROUND 566DM. AT THE SAME TIME THE ECMWF CALLS FOR A BROAD UPPER
RIDGE TO MOVE IN AND SET UP ALONG THE PAC NW COAST GIVING A DRY
NORTHWEST FLOW ALOFT TO THE AREA...WITH H5 HEIGHTS RUNNING AROUND
574DM OVER PHOENIX. IN SHORT THE GFS SOLUTION WOULD BE MUCH WINDIER
AND COOLER...THE MEX MOS FOR PHOENIX NEXT THURSDAY CALLS FOR 81
DEGREES VERSUS A FORECAST OF 92 FROM THE ECE MOS FROM THE EUROPEAN.

CONFIDENCE IN THE BOWLING BALL LOW SOLUTION THE GFS PRESENTS IS
EXTREMELY LOW...DUE TO SEVERAL FACTORS INCLUDING CLIMATOLOGY...POOR
PAST MODEL PERFORMANCE WITH LARGE CLOSED LOWS BEYOND DAY 5...HIGH
SPREAD IN THE GFS ENSEMBLE MEMBERS...AND TYPICALLY BETTER LONG RANGE
PERFORMANCE WITH THE ECMWF. THUS WILL HEDGE OUR TEMP AND WIND
FORECASTS FOR WED/THU CLOSER TO THE ECMWF SOLUTION...AND FORECAST
CENTRAL DESERTS HIGHS IN THE MID TO UPPER 80S BOTH DAYS UNDER SUNNY
SKIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...

HIGH PRESSURE OVER THE REGION TO KEEP WINDS MAINLY ON THE LIGHT
SIDE...AOB 10 KTS...EXCEPT AT KBLH...WHERE SOUTHERLY WINDS WILL
LIKELY RISE INTO THE 12-14 KT RANGE BY THIS AFTERNOON. A WEAK UPPER-
LEVEL DISTURBANCE APPROACHING FROM THE SOUTH WILL LIKELY CONTINUE TO
PUSH MORE SCT-BKN CIRRUS LAYERS OVER THE TAF SITES THROUGH AT LEAST
THE NEXT 24 HRS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
UPPER-LEVEL PACIFIC LOW PRESSURE SYSTEM TO WEAKEN THE HIGH PRESSURE
THAT IS CURRENTLY OVER THE REGION...ALLOWING TEMPERATURES TO COOL
DOWN TO NEAR...OR EVEN SLIGHTLY BELOW NORMAL THROUGH THE FORECAST
PERIOD...AND EVEN BING A CHANCE FOR SHOWERS AND THUNDERSTORMS ON
MONDAY AND TUESDAY...WITH THE BEST CHANCES FOR WETTING RAINS TO BE
OVER THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA. AFTERNOON
HUMIDITIES IN A 15 TO 25 PERCENT RANGE FROM SUNDAY THROUGH TUESDAY
TO FALL INTO THE 10-20 PERCENT RANGE ON WEDNESDAY AND
THURSDAY...WITH FAIR TO GOOD OVERNIGHT RECOVERIES. WINDS WILL
GENERALLY BE LIGHT AND DIURNAL...THOUGH BREEZY CONDITIONS ARE
POSSIBLE TUESDAY AND WEDNESDAY AFTERNOON.

&&

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

$$

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...NOLTE
PREVIOUS DISCUSSION...CB
AVIATION...PERCHA
FIRE WEATHER...PERCHA




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