Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 310425
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
924 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...
VIRTUALLY ALL OF THE CONVECTION THIS EVENING WAS CONFINED IN EXTREME
SOUTHEAST ARIZONA ALONG AND SOUTH OF THE INTERNATIONAL BORDER.
SATELLITE CURRENTLY SHOWS MOSTLY CLEAR SKIES OVER THE FORECAST
AREA...THOUGH SOME DEBRIS CLOUDINESS FROM THE EARLIER CONVECTION HAS
BEGUN ROTATING NORTHWARD INTO SOUTH-CENTRAL ARIZONA AROUND THE UPPER
LEVEL HIGH. BIG STORY TODAY WAS THE HIGH TEMPERATURES. A LOOK AT
READINGS ACROSS THE AREA FROM MESOWEST SHOWS NUMEROUS REPORTS AT OR
ABOVE 110 DEGREES. AT PHOENIX SKY HARBOR WE HIT 111...WHICH IS A FEW
DEGREES SHY OF THE 115 DEGREE RECORD SET IN 1934. IT APPEARS THE 92
DEGREE LOW TEMP THIS MORNING WILL ECLIPSE THE HIGH MINIMUM RECORD OF
90...SET IN 1996.

TOMORROW LOOKS TO BE ANOTHER VERY HOT DAY. CURRENT TEMPERATURES
ACROSS THE REGION ARE RUNNING A FEW DEGREES WARMER THAN 24-HOURS
AGO...WHICH MEANS THE DAY WILL START OF ON A VERY WARM NOTE. HIGH
TEMPERATURES TOMORROW...THOUGH MAYBE A TAD COOLER...WILL STILL END
UP AT OR ABOVE EXCESSIVE HEAT THRESHOLDS. AN EXCESSIVE HEAT WARNING
REMAINS IN EFFECT UNTIL 8 PM TOMORROW EVENING.

FORECAST PACKAGE OVERALL IS ON TRACK. MADE SOME MINOR ADJUSTMENT TO
GRIDS TO ACCOUNT FOR CURRENT CONDITIONS AND TRENDS.

&&

.PREV DISCUSSION...
ISSUED AT 130 PM MST WED JUL 30 2014

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.

REMAINDER FROM MORNING 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 ARE EXPECTED THROUGH THURSDAY MORNING...WITH
ONLY FEW/SCT MID AND HIGH CLOUDS DEVELOPING ACROSS THE REGION.
LARGEST FORECAST CHALLENGE WILL BE THE 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 ARE EXPECTED 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...MCLANE
PREVIOUS DISCUSSION...HIRSH/LEINS
AVIATION...MCLANE/MO/CB
FIRE WEATHER...CB












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