Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 011544
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
845 AM MST SUN MAY 1 2016


.SYNOPSIS...
A LOW PRESSURE SYSTEM WILL LINGER OVER THE REGION THROUGH TONIGHT...
PROVIDING BELOW NORMAL TEMPERATURES...AND A CHANCE OF SHOWERS AND
THUNDERSTORMS OVER NORTHERN AND EASTERN ARIZONA. A HIGH PRESSURE
SYSTEM WILL SUBSEQUENTLY REBUILD OVER THE REGION MONDAY THROUGH
THURSDAY...RESULTING IN MOSTLY CLEAR SKIES AND A STRONG WARMING
TREND. ANOTHER PACIFIC WEATHER SYSTEM HOWEVER IS FORECAST TO MOVE
INTO THE AREA NEXT FRIDAY AND THE WEEKEND...BRINGING COOLER
TEMPERATURES...BREEZY CONDITIONS...AND A SLIGHT CHANCE OF SHOWERS.

&&

.DISCUSSION...

A RATHER COOL MORNING...FOR THE 1ST OF MAY ACROSS OUR CWA THIS
MORNING. MOST LOWER DESERT LOCATIONS SAW LOWS IN THE UPPER 50-LOW 60
RANGE...WITH SKY HARBOR SEEING A LOW OF 59...6 DEGREES BELOW THE
NORMAL FOR THE DATE. THE UPPER LOW THAT BROUGHT US THIS COOL
WEATHER...AND THE RAINFALL YESTERDAY/LAST NIGHT IS NOW MOVING
EASTWARD ACROSS EAST-CENTRAL AZ AND IS EXPECTED TO MOVE INTO THE 4-
CORNERS REGION BY THIS EVENING. TO THE SOUTH AND WEST OF THIS LOW
CENTER...TEMPERATURES ALOFT ARE BEGINNING TO WARM...STABILIZING THE
ATMOSPHERE AND ENDING THE SHOWER ACTIVITY ACROSS MOST OF OUR CWA.
HOWEVER...LEFT-OVER MOISTURE ROTATING AROUND THE BACK SIDE OF THE
UPPER LOW CENTER IS STILL TRIGGERING A FEW SHOWERS OVER PINAL AND
SOUTHERN GILA COUNTIES...AS WELL AS EXTREME EASTERN MARICOPA COUNTY
AT THIS HOUR. THE LATEST HRRR HIGH-RES MODEL RUN IS SHOWING THESE
SHOWERS CONTINUING THROUGH ABOUT MIDDAY BEFORE DIMINISHING THIS
AFTERNOON. GIVEN THESE CURRENT TRENDS...IT APPEARS THAT OUR CURRENT
SHORT-TERM FORECASTS ARE HOLDING UP WELL..AND NO UPDATES ARE PLANNED
AT THIS TIME.

&&

.PREVIOUS DISCUSSION...

TODAY AND TONIGHT...

THE COOL LOW PRESSURE SYSTEM OVER AZ WILL LINGER OVER THE STATE
TODAY...ALBEIT MOVE SLOWLY TO THE EAST BY EARLY AFTERNOON. MODELS
FORECAST THE 500 MB CIRCULATION CENTER TO MOVE FROM OVER PHOENIX
EARLY THIS MORNING...TOWARD THE WHITE MOUNTAINS IN EAST CENTRAL AZ
BY AFTERNOON. THEREFORE A FEW LIGHT SHOWERS ARE POSSIBLE OVER THE
DESERTS NEAR PHOENIX THIS MORNING...CHANGING TO A SLIGHT CHANCE OF
SHOWERS DURING THE AFTERNOON WITH INCREASING STABILITY. MOSTLY
CLOUDY SKIES HOWEVER ARE FORECAST OVER MUCH OF SOUTHWEST AND SOUTH
CENTRAL ARIZONA TODAY...WITH THE BEST CHANCE OF SHOWERS AND
THUNDERSTORMS IN OUR MOUNTAINOUS ZONE 24 SOUTHERN GILA COUNTY
THROUGH EVENING. CLEARING TO PARTIAL CLEARING SKIES ARE EXPECTED
EARLY THIS EVENING WITH SHOWERS ENDING.

MONDAY THROUGH THURSDAY...

A HIGH PRESSURE SYSTEM WILL SLOWLY BUILD OVER THE REGION THIS PERIOD
PROVIDING MOSTLY CLEAR SKIES AND MUCH WARMER AFTERNOON TEMPERATURES.
BACK MIDDLE 90S ON THE LOWER DESERTS AGAIN...OR ABOUT 5 DEGREES ABOVE
NORMAL.

THURSDAY NIGHT THROUGH SUNDAY...

MODELS HAVE BEEN FORECASTING ANOTHER PACIFIC WEATHER SYSTEM TO
APPROACH SOUTHERN CA AND AZ LATE THURSDAY AND FRIDAY. ENSEMBLE
MEMBER SPREAD APPEARS TO BE CONSOLIDATING MORE...INCREASING OUR
CONFIDENCE THAT THIS NEW WEATHER SYSTEM WILL BODILY MOVE INTO THE
REGION FRIDAY AND THE WEEKEND.  SINCE ENSEMBLE MEMBERS ARE COMING
INTO CLOSER AGREEMENT...WE CAN PLACE SOME VALUE IN THE OPERATION GFS
WHICH SHOWS THIS SYSTEM TO BE INITIALLY DRY FRIDAY AND SATURDAY...
WITH PERHAPS A BETTER CHANCE OF PRECIP SUNDAY. THEREFORE A BROAD
BRUSH FORECAST APPROACH SEEMS TO BE IN ORDER FOR NOW...KEEPING A
SLIGHT CHANCE OF SHOWERS GOING...AND MUCH COOLER TEMPERATURES
DEVELOPING.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
UPPER LOW WILL BEGIN TO WEAKEN AND MAKE A SLOW EXIT TO THE EAST OVER
AZ TODAY. LIGHT RAIN SHOWER ACTIVITY WILL BE POSSIBLE DURING THE
MORNING FROM MARICOPA COUNTY EASTWARD BEFORE PRECIP ACTIVITY FOCUSES
ON THE MOUNTAINS NORTH/EAST OF PHOENIX. SCT TO BKN CLOUDS RANGING 8
TO 12KFT WILL PERSIST THROUGH EARLY AFTERNOON BEFORE DISSIPATING AND
EVENTUALLY CLEARING COMPLETELY AFTER SUNSET. TYPICAL EASTERLY AM
WINDS WILL TRANSITION SOUTH THEN WEST MIDDAY INTO THE
AFTERNOON...WITH GENERALLY LIGHT SPEEDS 6 KTS OR LESS.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
FOCUS OF ANY LINGERING PRECIP ACTIVITY TODAY WILL BE WELL EAST OF THE
CO RIVER VALLEY. NOTICEABLY LIGHTER WINDS IN STORE TODAY WITH
HEADINGS VARIANT BETWEEN WEST AND NORTHWEST FOR KIPL AND NORTH AND
NORTHEAST FOR KBLH. FEW TO SCT CLOUDS GNLY AOA 10KFT WILL DISSIPATE
DURING THE DAY...WITH CLEAR SKIES POSSIBLE BY THE AFTERNOON AND FOR
THE EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
HIGH PRESSURE WILL RESULT IN A DRIER AND WARMER AIRMASS OVER THE
DISTRICTS QUICKLY WARMING TEMPERATURES TO ABOVE NORMAL READINGS WITH
MANY LOWER ELEVATION SITES HEADING INTO THE MID TO UPPER 90S. DEEP
PACIFIC TROUGH WILL APPROACH THE WEST COAST MIDWEEK SUPPORTING
INCREASING SOUTHERLY WINDS FOR WEDNESDAY AND THURSDAY. THE
COMBINATION OF STRONG WINDS...PARTICULARLY FOR THURSDAY...AND LOW
HUMIDITIES MAY SUPPORT POCKETS OF CRITICAL FIRE WEATHER CONDITIONS
ACROSS THE LOWER AZ DESERTS. CONDITIONS WILL IMPROVE ON FRIDAY AND
SATURDAY WHEN THE NEXT STORM SYSTEM WILL COOL HIGH TEMPERATURES TO
THE LOW TO MID 80S WITH MINIMUM HUMIDITIES IN THE MID TEEN TO MID 20
PERCENT RANGE BY SATURDAY.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED.

&&

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

$$

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

DISCUSSION...PERCHA/VASQUEZ
AVIATION...NOLTE
FIRE WEATHER...NOLTE/SAWTELLE



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