Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 231159
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
459 AM MST SAT MAY 23 2015

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...
A SERIES OF LOW PRESSURE SYSTEMS MOVING THROUGH ARIZONA WILL KEEP
TEMPERATURES BELOW NORMAL THIS WEEKEND. SHOWER ACTIVITY IS
POSSIBLE...THOUGH PRECIPITATION WILL GENERALLY REMAIN WELL NORTH AND
EAST OF PHOENIX. A GRADUAL WARMING AND DRYING TREND IS EXPECTED NEXT
WEEK...WITH TEMPERATURES RETURNING TO THE UPPER 90S AND EVEN ABOVE
THE 100 DEGREE MARK BY NEXT WEEKEND.

&&

.DISCUSSION...
LATEST STREAMLINE ANALYSIS SHOWS THE PERSISTENT CYCLONIC FLOW
ACROSS THE DESERT SOUTHWEST ASSOCIATED WITH A LOW PRESSURE SYSTEM
CENTERED NEAR THE AZ/UT BORDER. A DRY SLOT IS EVIDENT ON WV IMAGERY AHEAD
OF THE LOW ACROSS SOUTHEASTERN AZ...THOUGH DEEPER MOISTURE FURTHER
WEST IS CURRENTLY OVERSPREADING THE MOJAVE DESERT.

OPERATIONAL MODELS REMAIN IN EXCELLENT AGREEMENT IN THE SHORT-TERM.
THE AFOREMENTIONED LOW PRESSURE SYSTEM WILL DRIFT NORTHEASTWARD
TODAY WHILE WEAKENING. CONSENSUS OF CONVECTIVE ALLOWING GUIDANCE
INDICATES THAT SHOWER ACTIVITY WILL BE FOCUSED ACROSS NORTHERN AZ
THIS AFTERNOON. ACROSS THE LOWER DESERTS...A FEW CLOUDS CAN BE
EXPECTED BUT THE BIG STORY WILL REMAIN THE WELL-BELOW NORMAL
TEMPERATURES WITH HIGHS GENERALLY IN THE LOWER 80S AND ROUGHLY 15
DEGREES BELOW NORMAL.

NEXT IN THE SERIES OF SHORT-WAVE TROUGHS WILL DIVE SOUTHEASTWARD
INTO SOUTHERN AZ SUNDAY. THIS VORT MAX WILL BE COMPACT BUT PRODUCE
STRONG FORCING FOR ASCENT IN A CONCENTRATED AREA ACROSS SOUTHEASTERN
AZ. BEST CHANCE FOR CONVECTION WILL BE IN THESE AREAS AND AGAIN
ACROSS NORTHERN-CENTRAL AZ IN THE VICINITY OF THE DEEPER MOISTURE.
HOWEVER...BOTH THE GFS AND NAM-WRF HAVE TRENDED STRONGER WITH THIS
SYSTEM AND IT BEARS WATCHING.

SHORT-WAVE RIDGE WILL MAKE A RETURN TO THE REGION MONDAY...HERALDING
WARMER CONDITIONS AND A RETURN TO THE 90S FOR MANY LOCATIONS. STEADY
HEIGHT RISES THROUGH THE WEEK IN A QUASI-ZONAL FLOW WILL YIELD A
GRADUAL WARMING TREND...WITH TEMPERATURES RECOVERING TO NEAR NORMAL
BY MID-LATE WEEK. MODELS SUGGEST A WEAK PACIFIC TROUGH WILL DRIFT EASTWARD
INTO THE INTERMOUNTAIN WEST LATE IN THE WEEK...BUT IT IS UNLIKELY TO
HAVE MUCH OF AN IMPACT IN TERMS OF SENSIBLE WEATHER. THEREAFTER...A
RIDGE IS LIKELY TO DEVELOP ACROSS THE REGION...WHICH WILL LIKELY
BOOST TEMPERATURES ABOVE THE 100 DEGREE MARK BY SATURDAY. FORECAST
TEMPERATURES WERE WEIGHTED HEAVILY TOWARDS THE OPERATIONAL AND
ENSEMBLE ECMWF WHICH HAVE PERFORMED WELL RECENTLY AND ARE OFTEN TOP
PERFORMERS IN THESE TYPES OF SETUPS.

&&

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

GENERALLY CLEAR SKIES THROUGH THE PERIOD EXCEPT FOR A FEW HIGHER
BASED CU THIS AFTERNOON OVER HIGHER TERRAIN AREAS. WINDS WILL BE
LIGHTER THAN THE PAST SEVERAL DAYS...BUT STILL CARRY A MORE DOMINANT
WESTERLY COMPONENT OVERALL. WILL LIKELY SEE SOME BREEZY AFTERNOON
WINDS...BUT MOSTLY ACROSS SOUTHEAST CALIFORNIA.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A FEW WEAK WEATHER DISTURBANCES WILL MOVE THROUGH THE DISTRICT NEXT
WEEK...HOWEVER DRY WEATHER WILL STILL PREVAIL. A GRADUAL WARMING
TREND WILL ALSO GRACE THE REGION BRINGING TEMPERATURES CLOSER TO THE
SEASONAL NORMAL. AS A RESULT...AFTERNOON RELATIVE HUMIDITY VALUES
WILL FALL BACK INTO THE TEENS FOLLOWING FAIR TO GOOD OVERNIGHT
RECOVERY. HOWEVER...WINDS WILL GENERALLY REMAIN LIGHT FOLLOWING
TYPICAL DAILY PATTERNS LEADING TO MINIMAL FIRE WEATHER CONCERNS.

&&

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

$$

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

DISCUSSION...HIRSCH
AVIATION...KUHLMAN
FIRE WEATHER...MO



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