Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 041627
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
925 AM MST WED MAY 4 2016

.SYNOPSIS...
STRONG HIGH PRESSURE WILL LEAD TO VERY WARM TEMPERATURES TODAY WITH
MANY LOWER DESERT LOCATIONS REACHING 100 DEGREES. A COOLING TREND
STARTS THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE SOUTHWEST.
WINDY CONDITIONS CAN ALSO BE EXPECTED THURSDAY WITH PATCHY BLOWING
DUST. TEMPERATURES CONTINUE TO FALL ON FRIDAY WITH HIGHS IN THE
UPPER 70S TO LOW 80S...CONTINUING THROUGH THE WEEKEND. ALONG WITH
THE COOLER TEMPERATURES...THERE WILL ALSO BE CHANCES FOR LIGHT
RAIN...MAINLY FRIDAY AND SATURDAY ALONG WITH A SLIGHT CHANCE OF
THUNDERSTORMS.


&&

.DISCUSSION...
SHORTWAVE RIDGING CONTINUES TO HOLD OVER THE SWRN CONUS AS A SLOW
MOVING NEGATIVE HEIGHT ANOMALY EASES TOWARDS SRN CALIFORNIA. 12Z
KTWC SOUNDING DATA INDICATED H5 HEIGHTS NEAR 582DM WHILE H8
TEMPERATURES HOVERED JUST ABOVE +21C. THESE HEIGHT AND TEMPERATURE
READINGS GENERALLY FALL BETWEEN THE 75TH AND 90TH PERCENTILE
EQUATING TO ABNORMALLY WARM CONDITIONS...THOUGH STILL SHORT OF
RECORD TERRITORY. REGARDLESS...NEW MODEL AND ASSOCIATED SOUNDING
DATA STILL STRONGLY SUGGESTS PHOENIX WILL EXPERIENCE ITS FIRST 100F
DAY OF THE CALENDAR YEAR. OTHERWISE...STRONGER SOUTHEAST WINDS ALOFT
WERE MUCH SLOWER TO MIX AND REMAIN LOCALIZED OVER RIDGE TOPS THIS
MORNING NECESSITATING FAR LESS WIND MENTION TODAY. ALSO...BOTH
HOURLY TEMPERATURE AND DEWPOINT READINGS WERE ADJUSTED TO MATCH
OBSERVATIONAL DATA.

&&

.PREVIOUS DISCUSSION...
/343 AM MST WED MAY 4 2016/
TODAY THROUGH SUNDAY...
AN OMEGA PATTERN IS IN PLACE OVER NORTH AMERICA AND NORTHEAST
PACIFIC WITH A NARROW HIGH AMPLITUDE RIDGE AFFECTING MUCH OF WESTERN
NORTH AMERICA AND DEEP TROUGHS IMMEDIATELY UPSTREAM AND DOWNSTREAM.
SOME ADDITIONAL SUBSIDENCE WARMING COMBINED WITH SOUTHERLY WINDS WILL
LEAD TO WARMER TEMPERATURES TODAY. THESE FACTORS WILL BE MAXIMIZED
OVER SOUTH-CENTRAL ARIZONA AND THUS NUDGED FORECAST HIGHS UP A COUPLE
DEGREES HIGHER THAN PREVIOUS PACKAGE. THE BREEZINESS LATER TODAY WILL
BE DUE TO THE APPROACH OF A LOW PRESSURE SYSTEM CURRENTLY CENTERED
WEST OF SAN DIEGO. MODELS HAVE BEEN SLOWING THE ADVANCE OF THE SYSTEM
WHICH MAKES SENSE GIVEN THE PATTERN IN PLACE AND THE ADVERTISED
UPSTREAM AMPLIFICATION. LIKEWISE...THE EXIT LOOKS TO BE A LITTLE
SLOWER. IN BETWEEN...THE SYSTEM WILL SEND A LARGELY DRY COLD FRONT
ACROSS CALIFORNIA AND ARIZONA THURSDAY AND FRIDAY. THIS WILL LEAD TO
MUCH COOLER TEMPERATURES. THE STRONGEST WINDS OF THE WEEK WILL BE
THURSDAY AFTERNOON. THERE WILL ALSO BE A SERIES OF VORT LOBES THAT ROTATE
THROUGH BETWEEN THURSDAY AND SUNDAY. THE BEST OPPORTUNITY FOR PRECIP
OVER OUR FORECAST AREA LOOKS TO BE FRIDAY NIGHT AND SATURDAY AS
COOLER AIR ALOFT COMBINES WITH SOME MODEST DYNAMICAL LIFT. THERE WILL
BE SOME MODEST INSTABILITY FOR A SLIGHT CHANCE OF
THUNDERSTORMS...MAINLY FRIDAY AND SATURDAY AFTERNOONS. THE FINAL
VORT LOBE COMES THROUGH SUNDAY FOR THE LAST GASP CHANCE AT PRECIP. OVERALL
THOUGH...THIS SYSTEM WILL NOT PRODUCE ANY SIGNIFICANT PRECIP OUTSIDE
OF ISOLATED THUNDERSTORMS. MOST NOTICEABLE CHANGE WILL BE THE
TEMPERATURES...WITH HIGHS IN THE UPPER 70S TO LOW 80S FRIDAY THROUGH
SUNDAY.

MONDAY THROUGH WEDNESDAY...
HIGH PRESSURE BUILDS IN DURING THE FIRST HALF OF THE NEXT WORKWEEK.
THIS WILL LEAD TO TEMPERATURES A FEW DEGREES ABOVE NORMAL BY
NEXT WEDNESDAY.

&&

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

HIGH PRESSURE ALOFT WILL LEAD TO MOSTLY CLEAR SKIES AND LIGHT
DIURNAL WINDS ACROSS THE DESERTS. WINDS WILL INCREASE FROM THE
SOUTHEAST LATER IN THE MORNING...BECOMING MOSTLY SOUTHERLY AND
LOCALLY BREEZY WELL INTO THE AFTERNOON. GUSTY SOUTH WINDS ARE ALSO
EXPECTED AT KBLH AFTER 18Z. WINDS SHOULD NOT BE STRONG ENOUGH TO
CAUSE BLOWING DUST ISSUES AT THE TAF SITES BUT THIS MAY CHANGE ON
THURSDAY.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
WITH A LARGE COOL PACIFIC LOW PRESSURE SYSTEM IN PLACE EXPECT COOLER
AND WELL BELOW NORMAL AFTERNOON HIGH TEMPERATURES TROUGH SUNDAY AND
MODERATELY BELOW NORMAL HIGHS BY MONDAY. THE RELATIVELY MOIST AIRMASS
WILL SUPPORT MINIMUM RELATIVE HUMIDITIES IN THE 20 TO 25 PERCENT
RANGE THROUGH SATURDAY. BREEZY TO OCCASIONALLY WINDY SOUTHWEST WINDS
ARE EXPECTED TO DEVELOP FRIDAY AFTERNOON WITH GUSTS IN THE 15 TO 25
MPH RANGE IN THE LOWER DESERTS AND 20 TO 30 MPH IN THE TONTO
FOOTHILLS AND SOUTHERN GILA COUNTY AND SOUTHEAST CA. WINDS WILL
DECREASE TO THE 10 TO 15 MPH RANGE SATURDAY THROUGH TUESDAY
AFTERNOON. IN ADDITION...A SLIGHT CHANCE OF AFTERNOON SHOWERS AND
ISOLATED THUNDERSTORMS ARE POSSIBLE FROM LATE AFTERNOON AND EVENING
ON FRIDAY THROUGH SATURDAY.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...RED FLAG WARNING FROM 11 AM TO 8 PM MST THURSDAY FOR AZZ132-133.

CA...NONE.

&&

$$

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

DISCUSSION...MO/AJ
AVIATION...CB
FIRE WEATHER...SAWTELLE


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