Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 031039
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
340 AM MST TUE MAY 3 2016

.UPDATE...AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...
TEMPERATURES WILL QUICKLY WARM TUESDAY AND PEAK WEDNESDAY UNDER HIGH
PRESSURE. SOME LOWER DESERTS WILL APPROACH TRIPLE DIGITS. THE HEAT
WILL NOT LAST LONG AS ANOTHER STORM SYSTEM ROLLS IN FROM THE
PACIFIC. WINDS WILL INCREASE WEDNESDAY AND BE STRONGEST THURSDAY
LEADING TO AREAS OF BLOWING DUST. FRIDAY INTO THE WEEKEND WILL
FEATURE BELOW NORMAL TEMPERATURES...VARIOUS CLOUD COVER...AND MODEST
CHANCES FOR RAIN.

&&

.DISCUSSION...
OVERNIGHT WATER VAPOR LOOPS OVER THE N.A. CONTINENT THIS MORNING
HERALD A HIGHLY AMPLIFIED WAVE PATTERN AND RIDGING BUILDING OVER THE
SOUTHWEST STATES. HIGH PRESSURE ANCHORED OVER THE INTERMOUNTAIN WEST
EXTENDS WELL NORTH INTO CANADIAN NORTHWEST TERRITORIES AND IS PINCHED
BETWEEN TWO DEEP TROUGHS OVER THE NORTHEAST PACIFIC AND THE
CENTRAL/EASTERN CONUS. COMPACT AND TRAILING UPPER SHORTWAVE THAT
BROUGHT SCATTERED PRECIP ACTIVITY TO THE NORTHERN AZ MOUNTAIN
YESTERDAY CONTINUES TO WEAKEN IN TERMS OF 500MB HEIGHTS BUT MAINTAINS
A SUBTLE CIRCULATION AS IT SLOWLY ROTATES EASTWARD. RIDGE HEIGHTS
OVER SOUTHERN CA ARE PUSHING EASTWARD AND WILL BEGIN TO SETTLE OVER
THE SOUTHWEST STATES TODAY AND WEDNESDAY...INTRODUCING A SHARP
WARMING TREND TO DAYTIME TEMPERATURES.

CONSENSUS AND NAM/GFS MOS HAVE BEGUN TO ADVERTISE 100F FOR PHOENIX
ON WEDNESDAY. UNDERSTANDING EVEN THE WARM BIASED BC GUIDANCE HAS THE
INFLUENCE OF THE LAST FEW DAYS OF BELOW AVERAGE TEMPERATURES...FELT
COMFORTABLE ENOUGH NUDGING UP FORECAST VALUES TO 100F FOR PHOENIX.
CLIMATOLOGICAL FIRST OBSERVANCE OVER THE LAST NORMAL PERIOD /98-10/
FALLS ON MAY 2ND...SO WE ARE CLOSE. YUMA STILL HAS TO HIT THEIR FIRST
100F OF 2016 ALSO...WITH APRIL 22ND THEIR AVERAGE FIRST OBSERVANCE
OVER THE LAST NORMAL PERIOD. YUMA COULD GET CLOSE ON WEDNESDAY
HOWEVER...500MB HEIGHTS BEGIN TO FALL ACROSS THE WESTERN FORECAST
AREA ZONES BY WEDNESDAY /SOUTH OF 580DM/ RELEGATING THEIR CHANCES
DEPENDENT TO THE WAA AND STRONG SOUTHERLY FLOW THAT BEGINS DURING
THE DAY.

WHILE THE WARMTH WILL BE THE MAIN HEADLINE WEDNESDAY...SOUTHERLY
WINDS WILL BECOME NOTICEABLE STRONGER AS THE AFOREMENTIONED PACIFIC
TROUGH BEGINS TO MOVE INTO THE WEST COAST. WINDS WILL BECOME STRONGER
FOR THURSDAY AS 55-PLUS KT 500MB AND 80-PLUS KT 300MB JET NOSES INTO
THE AREA AHEAD OF THE MAIN LOW CIRCULATION. DUST AND ASSOCIATED VSBY
RESTRICTIONS ARE PRESENT FOR WEDNESDAY WITH A MORE LOCAL FOCUS...BUT
BECOME A REGIONAL CONCERN ACROSS THE MAJORITY OF THE LOWER DESERT
ELEVATIONS THURSDAY. FORECAST SFC WINDS CONTINUE TO SIT WITHIN GEFS
UPPER PERCENTILE FORECASTS AND NEAR WIND ADVISORY THRESHOLDS.
COMBINATION OF STRONG WINDS AND LOW HUMIDITIES LEND THEMSELVES TO
FIRE WEATHER CONCERNS AS WELL THURSDAY AND AS SUCH A FIRE WEATHER
WATCH HAS BEEN POSTED FOR THE CENTRAL AZ ZONES/DISTRICTS JUST EAST OF
THE CO RIVER VALLEY. BY THURSDAY AFTERNOON THE UPPER LOW CENTER IN
PLOTTED NORTH OF THE L.A. BASIN...JUST OFF-SHORE.

MOISTURE PARAMETERS...PWAT OUTPUTS FROM GFS/GEFS AND MIXING RATIOS
FROM ECMWF...ARE BEGINNING TO FOCUS ON THE FIRST WAVE OF ACTIONABLE
MOISTURE IN COMBINATION WITH A VORT MAX/FROPA FOR
FRIDAY...PARTICULARLY IN THE AFTERNOON HOURS. STRONG UPSTREAM
HEIGHTS AND LL JET WINDS DOWN THE CA COAST SHOULD BE ABLE TO
TRANSPORT MARINE MOISTURE INLAND FOR FRIDAY WITH PWATS HEADING NORTH
TOWARD 0.75 INCH VALUES. FURTHER IMPROVEMENT OF GEFS REFORECAST POPS
AND FINER TIMING DETAILS LEAD ME TO NUDGE FCST POPS FOR FRIDAY INTO
THE CHANCE CATEGORY ACROSS SOUTH-CENTRAL AZ AND ALSO INCLUDE MENTION
OF THUNDER. TIMING OF COLDEST TEMPERATURES ALOFT AND LIS ARE NOT
PERFECTLY ALIGNED WITH PEAK HEATING...BUT GIVEN VERTICAL MOTION
ASSOCIATED WITH THE HEIGHT FALLS TRANSITIONING INTO THE AREA FELT
THUNDER MENTION WAS WARRANTED. SIGNIFICANT COOLING TREND IS STILL ON
TAP...WITH HIGHS DIPPING BACK INTO THE 70S/LOW 80S FOR MOST DESERT
LOCALES AND UPPER 60S/LOW 70S FOR THE NEARBY FOOTHILLS AND HIGHER
TERRAIN FOR FRIDAY AND SATURDAY.

HEADING INTO THE WEEKEND THE FORECAST REMAINS BROADLY COVERED BY
SLIGHT CHANCE POPS...COOLER TEMPERATURES AND PARTLY TO MOSTLY CLOUDY
SKIES. THIS LATEST TROUGH CUTOFFS...SIMILAR TO SYSTEMS EARLIER THIS
SPRING...AND BEGINS TO SEND EMBEDDED SHORTWAVE/VORT LOBES THROUGH THE
REGION AT VARIOUS TIMES. LATEST DETERMINISTIC AND ENSEMBLE STORM
TRACK FORECASTS EVENTUALLY DRAW THE SYSTEM EASTWARD BY EARLY NEXT
WEEK WITH PACIFIC HIGH PRESSURE TRANSITIONING INTO THE WEST.

&&

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

A HIGH PRESSURE SYSTEM WILL BUILD OVER THE REGION. STABLE CONDITIONS
WILL RESULT IN MOSTLY CLEAR SKIES WITH LIGHT WIND UNDER 6 KNOTS
THROUGH AT LEAST 23Z TUE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

THURSDAY THROUGH MONDAY...
...FIRE WEATHER WATCH THURSDAY AFTERNOON AND EVENING ACROSS
SOUTHWEST AND SOUTH CENTRAL ARIZONA...

THURSDAY...A PACIFIC COLD FRONT WILL MOVE INTO SOUTHERN CALIFORNIA
THURSDAY AFTERNOON. AHEAD OF THE FRONT...STRONG GUSTY SOUTH TO
SOUTHWEST WINDS 25 TO 35 MPH WILL DEVELOP OVER A LARGE PART OF
SOUTHWEST AND SOUTH CENTRAL ARIZONA.. WITH MINIMUM RELATIVE
HUMIDITIES FALLING BELOW 15 PERCENT...A FIRE WEATHER WATCH HAS BEEN
POSTED.

FRIDAY THROUGH MONDAY...BEHIND THURSDAYS COLD FRONT...A LARGE COOL
PACIFIC LOW PRESSURE SYSTEM WILL BECOME NEARLY STATIONARY OVER THE
REGION. THIS WILL PROVIDE COOLER AFTERNOON TEMPERATURES...ALONG WITH
A RELATIVELY MOIST AIRMASS. MINIMUM RELATIVE HUMIDITIES WILL RANGE
FROM 20 TO 25 PERCENT. AFTERNOON SOUTHWEST WINDS IN THE 15 TO 25 MPH
RANGE WILL DEVELOP FRIDAY...DECREASING INTO THE 10 TO 15 MPH RANGE
SATURDAY THROUGH MONDAY AFTERNOON. ADDITIONALLY...A SLIGHT CHANCE OF
AFTERNOON SHOWERS ARE POSSIBLE MAINLY OVER THE MOUNTAINS NORTH
THROUGH EAST OF PHOENIX.

&&

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

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...FIRE WEATHER WATCH FROM THURSDAY AFTERNOON THROUGH THURSDAY
     EVENING FOR AZZ132-133.

CA...NONE.
&&

$$

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

DISCUSSION...NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...VASQUEZ



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