Weather Service Report


587 
FXUS65 KPSR 220425
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
925 PM MST THU AUG 21 2014

.SYNOPSIS...
AN UPPER LEVEL LOW PRESSURE SYSTEM BRINGING SHOWERS AND 
THUNDERSTORMS TO PORTIONS OF ARIZONA EARLY TONIGHT WILL BEGIN TO 
MOVE OUT OF THE AREA BY FRIDAY MORNING. STORM CHANCES DECREASE 
FRIDAY AND THROUGH THE WEEKEND AS DRIER AIR OVERSPREADS THE AREA. 
BELOW NORMAL TEMPERATURES ARE FORECAST THROUGH SATURDAY...GRADUALLY 
RETURNING TO NORMAL EARLY NEXT WEEK.

&&

.DISCUSSION...
THE UNSEASONABLY STRONG UPPER LOW THAT HAS BEEN AFFECTING OUR REGION 
SINCE YESTERDAY IS NOW MAKING ITS WAY INTO CENTRAL ARIZONA LATE THIS 
EVENING. CURRENT WATER VAPOR IMAGERY SHOWS THE CENTER OF THE LOW 
BETWEEN BLYTHE CA AND PHOENIX AND IT HAS INCREASED ITS NORTHEASTWARD 
SPEED IN THE PAST FEW HOURS. AN AREA OF SHOWERS AND EMBEDDED 
THUNDERSTORMS JUST TO THE EAST OF THE LOW CENTER WILL MOVE OUT OF 
THE PHOENIX AREA BY MIDNIGHT INTO AN AREA OF MUCH LOWER INSTABILITY 
AND DRIER AIR. BEFORE THE LOW CENTER LIFTS COMPLETELY OUT OF OUR 
AREA...WE COULD STILL SEE SOME ISOLATED SHOWER DEVELOPMENT THROUGH 
AROUND 3 AM...SO OVERNIGHT POPS OF 10 TO 20 PERCENT REMAIN IN THE 
FORECAST FOR SOUTH-CENTRAL ARIZONA. RAIN-COOLED AIR HAS SWEPT ACROSS 
THE MAJORITY OF THE CWA THIS EVENING DROPPING AREA TEMPERATURES INTO 
THE UPPER 60S TO MID 70S IN MOST LOCATIONS. HAVE MADE ADJUSTMENTS TO 
THE OVERNIGHT TEMPERATURE FORECAST TO ACCOUNT FOR THIS...THINKING 
TEMPERATURES WILL MAINLY REMAIN FLAT THROUGH THE REST OF THE 
OVERNIGHT. 

&& 

.PREVIOUS DISCUSSION...
THE LOW WILL MOVE MOVE ACROSS THE STATE TONIGHT...THE TROUGH AXIS 
EXPECTED TO BE DRAPED ACROSS THE CENTRAL ARIZONA BY LATE FRIDAY 
MORNING. MID LEVEL FLOW BEHIND THE DEPARTING TROUGH TURNS SHARPLY 
OUT OF THE WEST LATE TONIGHT INTO FRIDAY...SO MOISTURE GETS SCOURED 
OUT AND THE FLOW BECOMES LESS FAVORABLE FOR STORMS FRIDAY AFTERNOON. 
WOULD ANTICIPATE THAT THE ATMOSPHERE WILL BE PRETTY WORKED OVER AND 
MORE STABLE ACROSS OUR ENTIRE FORECAST AREA FROM THIS EVENINGS 
ACTIVITY THAT LITTLE IN THE WAY OF CONVECTIVE STORMS WILL 
MATERIALIZE FRIDAY. STILL KEEPING SLIGHT CHANCE POPS GOING ACROSS 
SOUTHERN GILA COUNTY FOR FRIDAY AFTERNOON...AND MUCH OF THE SAME IS 
EXPECTED FOR SATURDAY AND SUNDAY AS LOW LEVEL MIXING RATIOS CONTINUE 
TO FALL TO AROUND 5-6 G/KG THIS WEEKEND. DAYTIME TEMPERATURES WILL 
CONTINUE TO BE BELOW NORMAL AS WE END THE WEEK...HOLDING IN THE MID 
TO UPPER 90S OVER THE LOWER DESERTS FRIDAY AFTERNOON...BARLEY 
BREAKING THE 100 DEGREE MARK SATURDAY AFTERNOON...AND A FEW MORE 
DEGREES OF WARMING FOR SUNDAY.

THERE IS A GENERAL AGREEMENT AMONG THE OPERATIONAL MODELS AND 
ENSEMBLES THAT MOISTURE WILL RETURN TO THE AREA MONDAY/TUESDAY... 
ALTHOUGH AT THIS POINT THERE DOES NOT APPEAR TO BE ANY CLEAR SIGNALS 
ON WHICH DAY WILL BE ACTIVE. GOING TO RETAIN A LOW-GRADE MONSOON POP 
FORECAST EACH AFTERNOON MONDAY THROUGH THURSDAY ALONG WITH NEAR 
NORMAL TEMPERATURES. 

&&
 
.AVIATION... 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
AN AREA OF SHOWERS AND A FEW LINGERING EMBEDDED THUNDERSTORMS WILL 
AFFECT THE PHOENIX TERMINALS THROUGH AROUND 06Z BEFORE GRADUALLY 
DIMINISHING AND LIFTING OUT OF THE AREA TO THE NORTHEAST. GUSTY 
OUTFLOW WINDS GENERALLY OUT OF THE SOUTHWEST WILL LAST INTO LATE 
EVENING...BUT DIMINISH CONSIDERABLY BY MIDNIGHT. NOW EXPECTING A 
DELAYED ONSET TO DOWNSLOPE EASTERLY WINDS...LIKELY NOT SWITCHING 
AROUND UNTIL 09-10Z. CIGS AT 10-12K FEET WILL LINGER THROUGH MUCH OF 
THE OVERNIGHT...BEFORE SCATTERING OUT AROUND DAYBREAK. AN ISOLATED 
SHOWER AND THUNDERSTORM THREAT WILL AGAIN BE POSSIBLE FOR FRIDAY 
AFTERNOON...BUT CONFIDENCE IN AFFECTING AREA TERMINALS IS FAIRLY LOW 
AT THIS POINT.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THE UPPER LOW CENTER HAS PUSHED INTO SOUTHWEST ARIZONA WITH CLOUDS 
BEGINNING TO SCATTER OUT FROM WEST TO EAST ACROSS SOUTHEAST 
CALIFORNIA. A GENERAL WESTERLY WIND COMPONENT IS EXPECTED THROUGH 
THE OVERNIGHT. SKIES WILL LIKELY CLEAR OUT SOMETIME FRIDAY MORNING 
WITH ONLY SOME LINGERING HIGH CIRRUS POSSIBLE FOR THE REST OF FRIDAY.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY... 
HUMIDITIES TREND DOWNWARD SOME MORE OVER THE WEEKEND BEFORE 
REBOUNDING SOME NEXT WEEK. AIR WILL BE DRIEST OVER SOUTHEAST 
CALIFORNIA AND HAINES INDEX VALUES CLIMB TO 5 BEFORE IMPROVING BY 
TUESDAY. HAINES VALUES WILL BE SIGNIFICANTLY LOWER EAST OF THERE DUE 
TO BETTER MOISTURE. OVERNIGHT RECOVERY WILL REMAIN GOOD...LESS SO 
OVER SOUTHEAST CALIFORNIA. STORM CHANCES WILL BE SLIGHT AND LIMITED 
TO THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA THROUGH 
TUESDAY...EXPANDING WESTWARD WEDNESDAY. 

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...MEYERS/LEINS
AVIATION...KUHLMAN
FIRE WEATHER...AJ







Return to Home page


Western Regional Climate Center, wrcc@dri.edu