Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 312129
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
229 PM MST FRI JUL 31 2015

.SYNOPSIS...
SCATTERED THUNDERSTORMS OVER SOUTHERN ARIZONA CAN BE EXPECTED
THIS AFTERNOON AND TONIGHT...LESS SO OVER SOUTHEAST CALIFORNIA. STORM
CHANCES WILL TREND DOWN SATURDAY WITH CHANCES LIMITED TO AREAS EAST
OF THE LOWER COLORADO RIVER VALLEY. FURTHER DRYING OCCURS NEXT WEEK
WITH STORM CHANCES CONFINED TO THE HIGHER TERRAIN EAST OF PHOENIX.
TEMPERATURES WILL HOVER NEAR NORMAL THROUGH NEXT WEEK.

&&

.DISCUSSION...
REST OF TODAY THROUGH SUNDAY...
EARLY AFTERNOON STORM ACTIVITY ALREADY AFFECTING FRINGES OF PHOENIX
METRO AS OF THIS WRITING. STORMS PRODUCING BOTH STRONG DOWNDRAFTS AND
LOCALLY HEAVY RAIN. SO FAR...GUST FRONTS HAVE LARGELY BEEN UNABLE TO
PRODUCE NEW STORMS. WITH A SHORT WAVE MOVING THROUGH ALONG WITH
EXISTING STORMS...LOWER DESERTS OF SOUTH-CENTRAL ARIZONA WILL STILL
HAVE A GOOD CHANCE OF STORMS.  OVER FAR SOUTHERN ARIZONA...STORMS
HAVE ALSO BEEN AIDED BY AN MCV FROM SONORA. AS THESE FEATURES
CONTINUE TO MOVE WEST AND NORTHWESTWARD...SOUTHWEST ARIZONA AND SOUTHEAST
CALIFORNIA WILL SEE AT LEAST ISOLATED STORMS...ESPECIALLY EAST OF THE
LOWER COLORADO RIVER VALLEY. SOME OF THE HI RES MODELS ARE INDICATING
DEBRIS SHOWERS FROM SONORA LATE TONIGHT INTO SATURDAY MORNING AND
THUS KEPT SOME LOW END POPS GOING. FOR SATURDAY AFTERNOON...WE WILL
BE ON THE BACK SIDE OF TODAY/S SHORT WAVE WHICH WOULD SUGGEST A
DOWNTREND IN ACTIVITY. ONE CAVEAT THOUGH IS ANOTHER SHORT WAVE FROM
BAJA WILL APPROACH THE AREA SATURDAY NIGHT. THUS HELD ON TO SOME
POPS EAST OF THE LOWER COLORADO RIVER VALLEY...WHERE MOISTURE WILL BE
BETTER. AS THE WAVE MOVES THROUGH SUNDAY IT WEAKENS. IT WILL BE
EMBEDDED WITHIN SOUTHWESTERLY FLOW ALOFT WHICH ADVECTS DRIER AIR INTO
THE DESERTS. SO POPS WILL BE LIMITED TO THE HIGHER TERRAIN OF SOUTH-
CENTRAL ARIZONA.

MONDAY THROUGH FRIDAY...THE RIDGE REBOUNDS EARLY NEXT WEEK BUT DOES
NOT SETUP IN A FAVORABLE POSITION UNTIL AT LEAST WEDNESDAY. LATEST
GFS AND ECMWF INDICATE SOME MOIST ADVECTION BEGINNING THEN. AS
USUAL...THE ECMWF IS MORE AGGRESSIVE THAN THE GFS. THIS IS A
DEPARTURE FROM PREVIOUS RUNS WHICH KEPT THINGS DRY. WILL KEEP POPS
MINIMAL FOR NOW UNTIL THE MOISTURE RETURN LOOKS MORE SOLID.

&&

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

AN ACTIVE START TO THE AFTERNOON WITH QUITE A BIT OF STORM ACTIVITY
ALREADY FIRING OVER THE MOUNTAINS TO THE NORTH AND EAST OF PHOENIX.
EVENTUALLY EXPECTING SOME STORM OUTFLOWS TO ALLOW FOR MORE STORM
DEVELOPMENT OVER THE LOWER DESERTS BY LATE AFTERNOON. CONFIDENCE IN
TIMING FOR STORMS IN THE LOWER DESERTS IS STILL SOMEWHAT LOW...BUT
WE MAY SEE SOME OUTFLOWS INTO THE PHOENIX TERMINALS AS SOON AS 22-
00Z AND THEN A SHOT AT SOME THUNDERSTORMS DURING THE EVENING HOURS.
WIND FORECASTS THROUGH MIDNIGHT ARE RATHER TRICKY DUE TO THE STRONG
LIKELIHOOD OF STORM OUTFLOWS AFFECTING THE AREA. THERE IS POTENTIAL
FOR SOME STRONG WIND GUSTS WITH THESE OUTFLOWS AND VISIBILITY
RESTRICTIONS IN DUST OR RAIN.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH...

WEST WINDS TO HOLD MOSTLY FOR KIPL THROUGHOUT THE DAY WHILE
SOUTHERLY HEADINGS ARE IN STORE FOR KBLH. SLIGHT CHANCE FOR ISOLATED
THUNDERSTORM DEVELOPMENT INTO THE AFTN ALONG THE CO RIVER
VALLEY...SO AT LEAST VCSH MENTION IS BACK IN THE KBLH TAF FOR THE
AFTN/EVENING HOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
MONSOONAL MOISTURE WILL SLOWLY BEGIN TO THIN ACROSS THE AREA...FIRST
ACROSS THE WESTERN FIRE DISTRICTS AND EVENTUALLY INTO THE ENTIRE
LOWER DESERT ELEVATIONS AND REGION BY EARLY NEXT WEEK. THIS WILL
RELEGATE STORM CHANCES BACK TOWARDS THE HIGHER TERRAIN AND FURTHER
TO THE EAST ACROSS AZ. MINIMUM RH VALUES WILL BEGIN TO SETTLE INTO
THE TEENS WHILE MAKING MOSTLY MODEST TO FAIR OVERNIGHT RECOVERIES.
THE SLIGHTLY DRIER AIRMASS AND BUILDING UPPER RIDGE HEIGHTS WILL
LEND THEMSELVES TOWARD WARMER SFC CONDITIONS...AT OR ABOVE SEASONAL
NORMALS. WINDS WILL FOLLOW FAMILIAR WARM SEASON PATTERNS. BY MIDWEEK
A SUBTLE RETURN OF GULF MOISTURE MAY BOOST AREA HUMIDITIES...BUT NOT
LINGER MUCH THROUGH THE END OF THE WEEK.

&&

.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...AJ
AVIATION...KUHLMAN
FIRE WEATHER...NOLTE



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