Severe Thunderstorm Warning 17, NWS Phoenix, AZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
232 PM MST FRI JUL 11 2014

.SYNOPSIS...
THERE WILL BE A LULL IN MONSOON FLOW THROUGH SATURDAY...WITH
THUNDERSTORM ACTIVITY MAINLY CONFINED ACROSS HIGHER TERRAIN AREAS.
THE DECREASE IN MOISTURE WILL ALSO ALLOW TEMPERATURES TO INCREASE
BOTH SATURDAY AND SUNDAY SEVERAL DEGREES ABOVE NORMAL. MOISTURE
SHOULD BEGIN TO SURGE BACK TO THE NORTH AND WEST EARLY NEXT WEEK
ALLOWING MORE WIDESPREAD THUNDERSTORM ACTIVITY AND TEMPERATURES
CLOSER TO SEASONAL NORMALS.

&&

.DISCUSSION...
IN THE SHORT-TERM PERIOD IT LOOKS LIKE ANOTHER DAY OF LOW GRADE
MONSOON ACTIVITY. PER OUR EARLIER DISCUSSION...DRIER AIR HAS BEGUN
WORKING ITS WAY INTO THE WESTERN PORTION OF OUR FORECAST AREA. THE
BOUNDARY BETWEEN THE DRY AIR TO THE WEST AND MORE MOIST AIR TO THE
EAST IS EASILY DISCERNIBLE ON WATER VAPOR IMAGERY. LESS CLOUDS IN
PLACE TODAY ACROSS THE ENTIRE FORECAST AIR HAS ENABLED SURFACE
TEMPERATURES TO RISE A FEW DEGREES ABOVE READINGS AT THIS SAME TIME
YESTERDAY. BOUNDARY LAYER MOISTURE HAS ALSO MIXED OUT QUITE A
BIT...ENABLING DEWPOINTS TO DROP SEVERAL DEGREES TODAY. READINGS IN
THE EASTERN HALF OF THE FORECAST AREA THOUGH ARE STILL HOVERING NEAR
THE MONSOONAL MYSTICAL 55 DEGREE THRESHOLD. FURTHER WEST
THOUGH...PARTICULARLY WEST OF THE COLORADO RIVER VALUES WERE IN THE
30S.

MODELS SHOW CONTINUED DRYING AND INCREASING STABILITY OVER THE
DESERT SOUTHWEST THROUGH THIS EVENING. GFS BUFR SOUNDING FOR
KPHX...FOR INSTANCE...SHOWS PWAT DROPPING FROM A VALUE O5 1.71 INCH
THIS MORNING TO 1.34 INCH BY TOMORROW MORNING AND LI/S INCREASING
FROM -2.9 TO 2.9 IN THE SAME PERIOD. SPC MESOSCALE ANALYSES INDICATE
THE GREATEST INSTABILITY IS CURRENTLY OVER THE HIGHER TERRAIN TO THE
EAST AND IN EXTREME SOUTHEAST ARIZONA. EXPECT THESE WILL BE THE MOST
FAVORABLE AREAS FOR THUNDERSTORM DEVELOPMENT THEN TODAY. AT 2
PM...ACTIVITY HAD ALREADY BEGUN FIRING OVER THE MOGOLLON RIM. AM NOT
EXPECTING ANY ACTIVITY IN OUR LOWER DESERTS...THOUGH OUTFLOW FROM
STORMS IN SOUTHEAST AZ COULD PUSH SOME DUST AND MAYBE TRIGGER AN
ISOLATED STORM...PRIMARILY OVER PINAL COUNTY.

THE LULL IN ACTIVITY WILL CONTINUE INTO SATURDAY. MOSTLY CLEAR SKIES
AND RISING 5H HEIGHTS WILL ENABLE AFTERNOON TEMPERATURES TO CREEP UP
TO AROUND THE 110 DEGREE MARK. ANY THUNDERSTORM ACTIVITY ONCE AGAIN
WILL BE PRIMARILY CONFINED TO THE HIGHER TERRAIN AND EXTREME SE
ARIZONA.

SUNDAY THROUGH TUESDAY WILL SEE AN INCREASE IN MOISTURE AND RETURN
TO A MORE ACTIVE MONSOON PERIOD. THE GFS...ECMWF...AND NAM ALL
INDICATE MONDAY THROUGH TUESDAY WILL BE THE MOST ACTIVE
PERIOD...WITH MORE WIDESPREAD STORMS MOVING INTO THE LOWER DESERTS.
THE GFS SHOWS PWAT IN EXCESS OF 1.75 INCHES MONDAY INTO TUESDAY LI/S
APPROACHING MINUS 4 AND SUFFICIENT CAPE. IF MONDAY BECOMES REAL
ACTIVE...TUESDAY MAY SEE LESS ACTIVITY.

BEYOND TUESDAY...BOTH THE GFS AND ECMWF BOTH APPEAR TO INDICATE A
GRADUAL DRYING TREND. THIS TIME OF YEAR THOUGH THIS MAY ONLY MEAN
SOME VERY SUBTLE CHANGES IN THE ACTUAL FORECAST. THUNDERSTORMS WILL
LIKELY REMAIN SOMEWHERE IN THE FORECAST AREA DURING AFTERNOON
HOURS...WITH THE MOST FAVORABLE AREAS FOR DEVELOPMENT BEING THE
HIGHER TERRAIN IN EAST-CENTRAL ARIZONA AND THE SOUTHEAST PORTION TO
THE STATE. STILL PLENTY OF TIME TO WORK OUT THE DETAILS.

TEMPERATURES WILL PEAK THIS WEEKEND NEAR 110 DEGREES IN THE LOWER
DESERTS...DROP A FEW DEGREES BELOW NORMAL MONDAY AND TUESDAY...AND
THEN TREND BACK TO NEAR NORMAL BY THE END OF THE WEEK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...WEST WINDS LESS
THAN 15 KTS FROM THE WEST EXPECTED THIS AFTN LOWERING TO 5 TO 10
AFTER 02Z.  VERY ISOLATED CHANCE FOR OUTFLOW BOUNDARIES WHICH COULD
SHIFT WIND DIRECTION AFTER 00Z BUT NOT ENOUGH CONFIDENCE TO WARRANT
INCLUSION IN TAFS. NO WEATHER CONCERNS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
VARIABLE TO SOUTHWEST 5 TO 10 KTS EXPECTED REST OF DAY WITH ONLY
SOME ISOLATED HIGH CLOUDS. NO WEATHER CONCERNS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
A SURGE OF RENEWED MONSOON MOISTURE WILL AFFECT THE DISTRICT
BEGINNING SUNDAY NIGHT EVENTUALLY LEADING TO SIGNIFICANTLY INCREASED
CHANCES OF SHOWERS AND THUNDERSTORMS...HIGHER HUMIDITIES...AND
SLIGHTLY LOWER AFTERNOON HIGH TEMPERATURES. THE BEST OPPORTUNITY FOR
WETTING RAIN WILL OCCUR ON MONDAY AND TUESDAY...WITH CHANCES
GENERALLY TAPERING DOWN LATER IN THE WEEK. WINDS WILL REMAIN RATHER
LIGHT WITH ONLY OCCASIONAL AFTERNOON GUSTS...HOWEVER SUBSTANTIALLY
STRONGER GUSTS WILL ACCOMPANY ANY AFTERNOON AND EVENING
THUNDERSTORMS. MINIMUM HUMIDITY LEVELS WILL GENERALLY ONLY FALL INTO
A 20 TO 30 PERCENT RANGE...WITH GOOD TO EXCELLENT OVERNIGHT
RECOVERY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

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DISCUSSION...MCLANE
AVIATION....WATERS
FIRE WEATHER...MO