Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 302136
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
236 PM MST SUN AUG 30 2015

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...
THERE WILL CONTINUE TO BE SUFFICIENT MOISTURE EAST OF THE LOWER
COLORADO RIVER TO SUPPORT ANOTHER ROUND OF ISOLATED TO EVEN
SCATTERED AFTERNOON AND EVENING THUNDERSTORMS TODAY. DRIER WESTERLY
FLOW WILL SLOWLY PUSH THE MOISTURE TO THE EAST BY TUESDAY...LIMITING
STORM CHANCES PRIMARILY TO HIGHER TERRAIN AREAS TO THE EAST OF
PHOENIX. THERE WILL ALSO BE A GRADUAL COOLING TREND THIS WEEK WITH
CENTRAL DESERTS HIGH TEMPERATURES DROPPING TO AROUND SEASONAL
NORMALS BY THE MIDDLE OR LATTER PORTION OF THE WEEK.

&&

.DISCUSSION...
BROAD AREA OF UL ASCENT COUPLED WITH A STILL FAVORABLE MONSOON
MOISTURE SURFACE ACROSS THE FOUR CORNERS AREA HAS SO FAR SUPPORTED
WIDESPREAD CONVECTION ACROSS NORTHERN AND SOUTHERN AZ.
MEANWHILE...THE SOUTH-CENTRAL AZ DESERTS HAVE BEEN SLOWER TO
DESTABILIZE WITH ONLY SOME MORE STOUT CU AND A FEW RADAR ECHOES
MANAGING TO POP-UP OVER THE EVER-FAVORED...OR AT LEAST IT SEEMS THAT
WAY THIS SEASON...PINAL/PIMA/MARICOPA BORDER AT THE TIME OF THIS
WRITING. MIDDAY STREAMLINE OVERLAYS AND STORM MOTION SO FAR TODAY
PLACE THE ANTICYCLONIC ML HIGH CIRC FURTHER TO THE NE THAN IT WAS
OBSERVED SATURDAY. ON TOP OF THAT...SPC MESOANALYSIS POINTING TO
SOME STRIPS OF CIN RUNNING ACROSS N-S ACROSS LA PAZ/YUMA AND
PINAL/MARICOPA COUNTIES ATTM...WHERE NORTHERN AZ REMAINS CIN FREE
AND AIDED BY THE WEAK TROUGH JET CUTTING THROUGH THE GREAT BASIN.
FOR THE REST OF TODAY`S STORM FORECAST...LOOK FOR ACTIVITY TO
CONSOLIDATE AND INCREASE IN COVERAGE EAST OF PHOENIX FOR THE REST OF
THE AFTN AS ACTIVITY IS GRADUALLY DRAWN INTO THE AREA FROM FLOW
AROUND THE ML CIRC CENTER.

ISOLATED STORM COVERAGE WILL BE POSSIBLE AGAIN THIS EVENING FOR THE
PHX METRO RELYING ON OUTFLOW COLLISIONS TO ACCESS THE LIMITED...BUT
STILL AVAILABLE...500-750 J/KG OR SO OF CAPE PROGGED OVER THE AREA.
ONE OTHER FACTOR THAT COULD HELP TRIGGER SOME MARICOPA CTY ACTIVITY
WOULD BE THE NOTICEABLE DRYLINE/GRADIENT ON WV IMAGERY OVER WESTERN
AZ. RESULTING DEWPOINTS BEHIND THIS INITIAL PUSH OF DRYING...PART OF
THE PACIFIC TROUGHING STRETCHING DOWN IN CA COAST...ARE STAYING
FAIRLY DRY ACROSS SOUTHEAST CA WITH READINGS IN THE UPPER 30S TO
40S. OVERNIGHT...DEBRIS CLOUDINESS WITH A STRAY SHOWER OR TWO IS
POSSIBLE FROM PHOENIX EASTWARD...WITH MOSTLY CLEAR SKIES AND MILD
OVERNIGHT CONDITIONS ACROSS WESTERN AZ INTO SOUTHEAST CA.

STARTING ON MONDAY...OPERATIONAL RUNS OF THE GFS AND ECMWF AS WELL
AS ENSEMBLE GUIDANCE CONTINUE TO CALL FOR THE START OF A GRADUAL
DRYING AND COOLING TREND AS TROUGHING SETTLES FURTHER ALONG THE WEST
COAST AND GIVES A DEEP SOUTHWESTERLY FLOW ALOFT TO SERN CA AND
ARIZONA. WHERE EARLIER FORECASTS HAVE CALLED FOR THIS FLOW TO SCOUR
OUT AND SWEEP THE DEEPER MOISTURE SURFACE TO OUR EAST AT A FAIRLY
QUICK RATE...DETERMINISTIC AND ENSEMBLE FCST GUIDANCE STILL POINT TO
A SOUTHERLY 850MB FLOW INTO THE REGION...MAINTAINING SOME SEMBLANCE
OF ELEVATED DEWPOINTS AND LL TO ML MIXING RATIOS THRU MIDWEEK.
CONFLUENT FLOW THROUGH THE ML AND UL WON`T BE OVERLY SUPPORTIVE OF
STORMS...BUT CANNOT RULE OUT AT LEAST SLIGHT CHANCES FOR THE LIMITED
AREAS OF HIGHER TERRAIN ACROSS SOUTH-CENTRAL AZ. OTHERWISE...BEST
LOCALES FOR STORMS WILL BE PRIMARILY CONFINED TO HIGHER TERRAIN
AREAS EAST OF PHOENIX. EXCEPT FOR SOME HIGH CLOUDS AT TIMES MOVING
THROUGH THE SOUTHWEST FLOW ALOFT SKIES WILL BE MOSTLY SUNNY OVER THE
LOWER DESERTS THROUGH MOST OF THE WORK WEEK. AS HEIGHTS SLOWLY
LOWER...HIGH TEMPERATURES WILL DROP OFF DAY BY DAY. MONDAY WILL
STILL SEE HIGH TEMPS WELL ABOVE NORMAL WITH HIGHS AROUND 107
EXPECTED AT PHOENIX BUT BY WEDNESDAY THE CENTRAL DESERTS SHOULD
LOWER TO AROUND 104 DEGREES...AND MUCH CLOSER TO SEASONAL
NORMALS...WITH LITTLE CHANGE THEN EXPECTED INTO THE WEEKEND.

THERE IS A BIT OF A WRINKLE IN THE FORECAST OUT AT THE END OF THE
EXTENDED PERIOD...OVER THE COMING WEEKEND...AS MEDIUM RANGE MODELS
CONTINUE TO CALL FOR SOME TROPICAL MOISTURE TO BE DRAWN NORTHWARD BY
THE BROAD TROF OVER THE WESTERN CONUS...AND THEN SPREAD INTO THE
LOWER ARIZONA DESERTS LEADING TO AT LEAST A SLIGHT CHANCE OF
AFTERNOON AND EVENING SHOWERS OR THUNDERSTORMS BY SATURDAY. POPS
HAVE BEEN RAISED OVER THE WEEKEND ACCORDINGLY...AND WILL BE SLIGHTLY
GREATER THAN CLIMO VALUES FOR NOW.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
CONDITIONS REMAIN FAVORABLE FOR AT LEAST ISOLATED STORMS ACROSS THE
PHOENIX METRO AREA AND POINTS EAST THIS EVENING. SOME CONVECTIVE
INHIBITION WILL LIKELY RESULT IN A LATER ONSET TO THE
ACTIVITY...PERHAPS AROUND 03Z WITH THE BEST CHANCES TO THE SOUTH NEAR
KIWA. SIMILAR TO LAST NIGHT...AN OUTFLOW BOUNDARY WITH AN ABRUPT
EASTERLY WIND SHIFT IS ALSO LIKELY AROUND 03-04Z...AFFECTING ALL
TERMINALS. ANY STORMS THAT DO DEVELOP HAVE THE POTENTIAL TO PRODUCE
STRONG WIND GUSTS AND BLOWING DUST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NO WEATHER-RELATED AVIATION IMPACTS EXPECTED AT KIPL OR KBLH THROUGH
MONDAY

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY... A LOW PRESSURE SYSTEM ACROSS THE PACIFIC
NORTHWEST WILL DISPLACE THE MONSOON HIGH TO THE SOUTH AND EAST
THROUGH THE WEEK. THE TREND WILL BE TOWARDS COOLER AND DRIER
CONDITIONS ACROSS THE DESERT SOUTHWEST. HOWEVER...ENOUGH MOISTURE
WILL LINGER ACROSS EASTERN ARIZONA FOR ISOLATED AFTERNOON
THUNDERSTORMS. FOR THE WEEKEND...LATEST GUIDANCE IS HINTING AT A
RETURN TO DEEPER MOISTURE AND BETTER RAIN CHANCES...PARTICULARLY
SOUTH AND EAST OF PHOENIX.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTERS ARE ENCOURAGED TO REPORT CONDITIONS ACCORDING TO STANDARD
OPERATING PROCEDURES.

&&

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

$$

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

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



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