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592
FXUS65 KPSR 271134
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
430 AM MST WED AUG 27 2014

...UPDATED AVIATION AND FIRE WEATHER...

.SYNOPSIS...
WHILE THERE MAY STILL BE SOME LINGERING SHOWERS AND A FEW
THUNDERSTORMS ACROSS EAST-CENTRAL ARIZONA TODAY...A DRIER AND WARMER
STRETCH OF WEATHER WILL TAKE OVER LASTING AT LEAST THROUGH THE
WEEKEND. HIGH TEMPERATURES WILL CLIMB BACK TO NEAR NORMAL BY
THURSDAY PEAKING ON FRIDAY AND SATURDAY WITH SOME LOWER DESERT SPOTS
APPROACHING 110 DEGREES ACROSS SOUTHEAST CALIFORNIA AND SOUTHWEST
ARIZONA.

&&

.DISCUSSION...
ALTHOUGH THE MONSOON SEASON STILL OFFICIALLY HAS ANOTHER MONTH TO
GO...THE SYNOPTIC PATTERN IS ALREADY STARTING TO LOOK MORE LIKE A
MID TO LATE SEPTEMBER REGIME. THE PACIFIC LOW PRESSURE SYSTEM THAT
MOVED OUT OF NEVADA EARLIER TODAY INTO SOUTHERN UTAH IS SLOWLY
DRAWING IN DRIER AIR ALOFT FROM THE WEST INTO SOUTHERN CALIFORNIA
AND SOUTHERN ARIZONA. HOWEVER...BELOW 700MB THE ATMOSPHERE WILL
REMAIN FAIRLY MOIST WITH MIXING RATIOS AROUND 10 G/KG UNTIL LATER
THIS AFTERNOON WHEN DRY AIR ALOFT MIXES DOWN. CURRENT WATER VAPOR
IMAGERY SHOWS A HINT OF A TRAILING VORTICITY LOBE PASSING THROUGH
CENTRAL ARIZONA WHICH HAS HELPED TO KICK OFF SOME NIGHTTIME
SHOWERS AND THUNDERSTORMS ACROSS YAVAPAI AND COCONINO COUNTIES TO
OUR NORTH. EXPECTING AT LEAST A FEW OF THESE SHOWERS TO VENTURE INTO
NORTHERN PORTIONS OF MARICOPA AND POSSIBLY INTO GILA COUNTY THROUGH
12Z. ELSEWHERE...FURTHER TO THE SOUTH AND WEST...THE DRIER AIR AND
INCREASING SUBSIDENT FLOW ALOFT IS MORE EVIDENT UNDER MAINLY CLEAR
SKIES. THERE WILL STILL BE A SLIGHT CHANCE OF SOME SHOWERS ACROSS
FAR NORTHERN MARICOPA COUNTY INTO SOUTHERN GILA COUNTY THROUGH THE
REST OF THIS MORNING INTO EARLY AFTERNOON...BUT ALL ACTIVITY SHOULD
CEASE BY SUNSET. AS THE PACIFIC LOW CONTINUES TO TRACK EASTWARD INTO
WESTERN COLORADO BY LATE THIS AFTERNOON...WINDS ALOFT WILL VEER TO
THE NORTHWEST BRINGING IN INCREASINGLY DRY AIR ABOVE 700MB WITH
SUBSIDENT FLOW ALOFT OVERTAKING THE ENTIRE CWA.

FOR THURSDAY THROUGH THE WEEKEND...ZERO POPS ARE IN THE FORECAST
DURING THE PERIOD AS A VERY DRY NORTHWESTERLY UPPER LEVEL FLOW
PATTERN PERSISTS ACROSS THE DESERT SOUTHWEST. THE SUBTROPICAL HIGH
BUILDS WESTWARD BEHIND THE EXITING PACIFIC LOW WITH THE HIGH CENTER
SETTLING JUST OFF THE SOUTHERN CALIFORNIA COAST. THIS WILL ALLOW
500MB HEIGHTS TO BUILD ACROSS OUR REGION AND FOR AN UPTICK IN
TEMPERATURES. HIGHS WILL RETURN TO NEAR SEASONAL NORMALS ALREADY ON
THURSDAY AND THEN CLIMB A COUPLE DEGREES HIGHER FOR FRIDAY AND
SATURDAY. WOULDN/T BE SURPRISED IF A FEW LOCATIONS ACROSS THE
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA DESERTS HIT 110 ON FRIDAY
AND SATURDAY.

THE UPPER RIDGE WILL BEGIN TO BREAK DOWN ON SATURDAY AS A TROUGH
MOVES INTO THE PACIFIC NORTHWEST. MODELS ARE IN EXCELLENT AGREEMENT
THIS TROUGH WILL FLATTEN THE RIDGE TO OUR SOUTHWEST...BUT KEEP US
UNDER A WESTERLY TO NORTHWESTERLY DRY UPPER LEVEL FLOW INTO NEXT
MONDAY. HIGHS SHOULD START TO TREND DOWNWARD STARTING SUNDAY AS THE
TROUGH TO OUR NORTH SLOWLY KNOCKS DOWN OUR UPPER HEIGHTS. SOME MODEL
DIFFERENCES ARE SHOWN NEAR THE END OF THE FORECAST PERIOD FOR NEXT
TUESDAY AND WEDNESDAY AS THE EUROPEAN BEGINS TO REBUILD THE
SUBTROPICAL HIGH TO OUR SOUTHEAST AND POSSIBLY ALLOWS FOR SOME
MINIMAL MOISTURE RETURN UNDER WEAK SOUTHEASTERLY FLOW. THE GFS KEEPS
THE DRIER WESTERLY FLOW ALOFT UNDER A WEAKER SUB-TROPICAL HIGH
CENTERED STILL TO OUR SOUTHWEST. TO ACCOUNT FOR THE POTENTIAL RETURN
IN MONSOONAL MOISTURE...HAVE INTRODUCED AT LEAST SOME LOW END SLIGHT
CHANCE POPS FOR TUESDAY AND WEDNESDAY ACROSS THE HIGHER TERRAIN IN
GILA COUNTY.

&&

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

NO AVIATION CONCERNS THROUGH THURSDAY MORNING WITH ANY THUNDERSTORM
ACTIVITY REMAINING OVER THE HIGHER TERRAIN AREAS NORTH AND EAST OF
THE PHOENIX TERMINALS. THE PRESSURE GRADIENT WILL BE VERY WEAK
YIELDING LIGHT WINDS. THE ONLY MINOR UNCERTAINTY IS TIMING OF THE
NOCTURNAL WIND SHIFT LATE IN THE PERIOD...WHICH WILL LIKELY OCCUR
SOMEWHAT MORE DELAYED THAN USUAL.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
STRONG HIGH PRESSURE ALOFT AND DRY NORTHWEST FLOW WILL BUILD OVER
THE DISTRICT THROUGH EARLY NEXT WEEK. EVEN ACROSS GILA
COUNTY...CHANCES FOR THUNDERSTORMS ARE ALMOST ZERO THROUGH THE
ENTIRE PERIOD. WITH TEMPERATURES AT OR SLIGHTLY ABOVE THE SEASONAL
AVERAGE...AFTERNOON HUMIDITIES WILL RANGE FROM THE TEENS AT LOWER
ELEVATIONS TO 20-30 PERCENT OVER HIGHER TERRAIN. FAIR OVERNIGHT
RECOVERY THROUGH THE WEEKEND WILL GRADUALLY INCREASE...BECOMING GOOD
OR EXCELLENT BY EARLY NEXT WEEK. WIND SPEEDS WILL BE UNCOMMONLY LOW
THROUGH THE WEEKEND...WITH VERY LITTLE GUSTY CHARACTER.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
AVIATION...MO
FIRE WEATHER...CB/MO







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