Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 302031
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
130 PM MST WED JUL 30 2014

.SYNOPSIS...
THERE WILL BE A BREAK IN THE MONSOON THROUGH THURSDAY...WITH
DECREASED CHANCES OF SHOWERS AND THUNDERSTORMS.
CONSEQUENTLY...TEMPERATURES WILL CONTINUE THEIR UPWARD TREND AND
HIGHS IN THE 110-115 RANGE WILL BE COMMON ACROSS THE DESERTS THROUGH
THURSDAY. A RETURN TO A MORE TYPICAL MONSOON REGIME IS EXPECTED LATE
FRIDAY INTO THE WEEKEND AS SHOWERS AND THUNDERSTORMS ARE ONCE AGAIN
EXPECTED ACROSS THE REGION.

&&

.DISCUSSION...
MONSOON HIGH IS LOCATED ALONG THE SOUTHERN AZ/NM BORDER...WHICH IS
RESULTING IN A WESTERLY FLOW IN THE MID-LEVELS AND A SOUTHWESTERLY
FLOW ALOFT. MAIN CONCERN FOR TODAY IS THE HOT CONDITIONS AND AN
EXCESSIVE HEAT WARNING REMAINS IN EFFECT FOR THE LOWER DESERTS. IN
THE PHOENIX AREA...TEMPERATURES ARE ALREADY APPROACHING THE 100
DEGREE MARK AFTER A MORNING LOW OF 92 DEGREES. THIS WILL MOST LIKELY
BREAK THE PREVIOUS RECORD WARM MIN OF 90 DEGREES...WHICH WAS SET IN
1996. TEMPERATURES THIS AFTERNOON HAVE BEEN RUNNING 3 TO 4 DEGREES
ABOVE THOSE OBSERVED YESTERDAY AT THIS TIME.

GLOBAL AND CONVECTIVE ALLOWING GUIDANCE REMAINS IN GOOD AGREEMENT
THAT THUNDERSTORM ACTIVITY WILL REMAIN CONFINED TO THE HIGHER
TERRAIN THROUGH THURSDAY. INCREASE IN MOISTURE WILL KNOCK ABOUT A
DEGREE OFF FORECAST TEMPERATURES...THOUGH HEAT WILL CONTINUE TO BE
EXCESSIVE AND A WARNING WILL REMAIN IN EFFECT THROUGH 8 PM.

&&

.PREVIOUS DISCUSSION...
MONSOON MOISTURE IS EXPECTED TO CREEP BACK INTO THE AREA ON FRIDAY
AND BY AND LARGE THE FORECAST THINKING HAS NOT CHANGED FOR FRIDAY
THROUGH THE WEEKEND. DEEPER MOISTURE WILL LAG A BIT AND IS NOT
EXPECTED TO ARRIVE IN THE DESERTS UNTIL THIS WEEKEND. POPS WERE
INCREASED A BIT FOR FRIDAY /STILL GENERALLY LOOKING AT SLIGHT
CHANCES/ BUT HIGHER VALUES SEEM WARRANTED FOR SATURDAY AND SUNDAY.
BOTH THE GFS AND EUROPEAN INDICATE A TROUGH MOVING THROUGH THE AREA
AT 700-500MB SATURDAY AFTERNOON/EVENING WITH MID LEVEL WINDS AROUND
20KTS...MLCAPES AROUND 1000 J/KG AND MEAN BL MIXING RATIOS AROUND
8-10 G/KG. IF THOSE VALUES ACTUALLY COME TO PASS IT COULD END UP
BEING QUITE ACTIVE SATURDAY EVENING. SIMILAR CONDITIONS ARE EXPECTED
SUNDAY HOWEVER ITS TYPICALLY DIFFICULT TO GET BACK TO BACK ACTIVE
DAYS SO MY CONFIDENCE IN THE WEEKEND FORECAST IS LOW...ESPECIALLY
FOR SUNDAY.

LOOKING DOWN THE ROAD TO NEXT WEEK...SOUTHWEST FLOW IS EXPECTED TO
RETURN TO THE AREA MONDAY/TUESDAY...ADVECTING SOMEWHAT DRIER AIR
INTO THE REGION FROM THE WEST AND ONCE AGAIN RESULTING IN DECREASED
CHANCES OF PRECIP ALONG WITH INCREASED TEMPERATURES.

&&

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

NO AVIATION IMPACTS THROUGH THIS EVENING AS ONLY FEW/SCT
MID AND HIGH CLOUDS DEVELOP MAINLY OVER HIGH TERRAIN REMOVED FROM
TERMINAL SITES. LARGEST FORECAST CHALLENGE WILL BE TIMING OF WIND
SHIFTS...AND MUCH LIKE THE PAST 24 HOURS...TYPICAL DIRECTIONAL
CHANGES MAY BE DELAYED OR ABSENT. EVEN PROLONGED PERIODS OF VARIABLE
WINDS WILL BE POSSIBLE...WITH PEAK WINDS GENERALLY AOB 12KT.
SLIGHTLY BETTER STORM CHANCES FOR THURSDAY AFTN/EVE AS HUMIDITY
VALUES START TO CLIMB.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
THE DRIER WESTERLY FLOW ALOFT OF MIDWEEK WILL BE REPLACED BY A MORE
CLASSICAL MONSOONAL SOUTHEAST FLOW ALOFT...WHICH WILL SPREAD
INCREASING MOISTURE WESTWARD ACROSS THE DESERTS FRIDAY INTO THE
WEEKEND. AS THIS OCCURS THE CHANCES FOR AFTERNOON AND EVENING
THUNDERSTORMS WILL INCREASE FROM EAST TO WEST EACH DAY. HUMIDITY
VALUES WILL STEADILY INCREASE WITH MINIMUM VALUES BETWEEN 20 AND 30
PERCENT EXPECTED ACROSS THE DESERTS SATURDAY INTO THE EARLY PART OF
NEXT WEEK. CORRESPONDINGLY...HIGH TEMPERATURES WILL FALL
OFF...DROPPING FROM AROUND SEASONAL NORMALS FRIDAY TO WELL BELOW
NORMAL VALUES ON SUNDAY. SLIGHT WARMING WILL RETURN BY NEXT TUESDAY
AS HUMIDITY VALUES LOWER SOMEWHAT. STRONG WINDS ARE NOT EXPECTED
DURING THE FIVE DAY PERIOD...AND THEY SHOULD TYPICALLY FAVOR SOUTH
TO SOUTHWEST DIRECTIONS DURING THE AFTERNOON AND EVENING HOURS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...EXCESSIVE HEAT WARNING FROM 10 AM THIS MORNING TO 8 PM MST
     THURSDAY AZZ020>023-025>028.

CA...EXCESSIVE HEAT WARNING FROM 10 AM THIS MORNING TO 8 PM PDT
     THURSDAY CAZ031>033.

&&

$$

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

DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...LEINS
AVIATION...MO/CB
FIRE WEATHER...CB







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