Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 241235
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
535 AM MST THU JUL 24 2014

.UPDATE...AVIATION SECTION UPDATED.

&&

.SYNOPSIS...
A STRONG HIGH PRESSURE SYSTEM IS FORECAST TO CONTINUE OVER THE
REGION THROUGH THE END OF THE WEEK...RESULTING IN VERY HOT
TEMPERATURES THROUGH FRIDAY. SUFFICIENT MOISTURE WILL BE IN PLACE
FOR AT LEAST A SLIGHT CHANCE OF THUNDERSTORMS ON MOST DAYS THROUGH
THE MIDDLE OF NEXT WEEK...MORE SO OVER THE HIGHER TERRAIN OF
SOUTH-CENTRAL ARIZONA.

&&

.DISCUSSION...

THURSDAY...
AFTER A MORE ACTIVE DAY ON WEDNESDAY AND OVERNIGHT...IN SPITE OF THE
EXCESSIVE HEAT...A BIT OF A DOWNTREND TREND IN CONVECTIVE ACTIVITY
SEEMS TO BE IN THE CARDS FOR TODAY. SOMEWHAT DRIER AIR IS EXPECTED
TO SPREAD INTO THE REGION BEHIND THE WEAK SHORTWAVE THAT TRIGGERED
THE THUNDERSTORM ACTIVITY OVER THE REGION ON WEDNESDAY AS THE UPPER
HIGH CENTER THAT HAS BROUGHT US THE VERY HOT WEATHER THE LAST FEW
DAYS REPOSITIONS ITSELF OFF TO THE EAST OVER NM. THE REDUCTION OF
THE AMOUNT OF CLOUD COVER AND DRYING OF THE LOWER LEVELS OF THE
ATMOSPHERE...ALONG WITH ANOTHER VERY WARM START TO THE DAY (90F+
LOWS AT MANY LOWER DESERT LOCATIONS) IS EXPECTED TO ALLOW ENOUGH
WARMING TO APPROACH OR REACH EXCESSIVE HEAT CRITERIA ACROSS THE
LOWER DESERTS FOR ONE MORE DAY...IN SPITE OF SOME REDUCTION OF THE
500MB HEIGHTS OVER THE REGION...FROM 595-596DM YESTERDAY TO
592-592DM TODAY. GIVEN THE RELOCATION OF THE MAIN MOISTURE PLUME TO
THE WEST...IT APPEARS THE BEST CHANCE FOR ANY ISOLATED THUNDERSTORM
ACTIVITY TODAY WILL BE ACROSS WESTERN PIMA COUNTY...PERHAPS
EXTENDING INTO SOUTHWEST MARICOPA COUNTY AND INTO EASTERN YUMA
COUNTY.

FRIDAY THROUGH SATURDAY...
SLIGHTLY COOLER AFTERNOON TEMPERATURES ARE FORECAST FOR FRIDAY AS
THE UPPER-LEVEL HIGH WEAKENS A BIT...AND A LITTLE MORE MONSOON
MOISTURE SPREADS INTO THE REGION. A BETTER THREAT FOR AFTERNOON AND
EVENING CONVECTION IS EXPECTED ON SATURDAY AS THE UPPER HIGH CENTER
SHIFTS A LITTLE FURTHER EAST...ALLOWING A DEEPER SOUTHEASTERLY FLOW
TO DEVELOP OVER THE REGION...IMPORTING MORE MOISTURE INTO THE DESERT
SOUTHWEST. ANOTHER WEAK SHORTWAVE EMBEDDED IN THIS FLOW APPEARS THAT
IT WILL MOVE INTO THE REGION...FURTHER ENHANCING THE CONVECTIVE
ACTIVITY AS MUCAPES ARE PUSHED UP INTO THE 500-100 J/KG RANGE.
THUS...HAVE DECIDED TO RAISE POPS OVER THE REGION AND LOWER MAX
TEMPS ON THAT DAY.

SUNDAY THROUGH THURSDAY...
IT APPEARS THAT A LOW-MID GRADE MONSOON WILL LIKELY PREVAIL THROUGH
THE EXTENDED PERIOD AS WEAK SOUTHERLY FLOW ALOFT CONTINUES TO PULL
MOISTURE INTO THE REGION...BUT WITH THE UPPER HIGH CENTER ATTEMPTING
TO REPOSITION ITSELF WESTWARD BACK OVER THE REGION...STABILIZING THE
AIRMASS SOMEWHAT AND PERHAPS PUTTING A BIT OF A LID ON THE
CONVECTIVE ACTIVITY.

&&

.CLIMATE...

RECORD HIGH TEMPERATURE FOR THE MIDDLE OF THE WEEK.

CITY        JULY 24       JULY 25
----        -------       -------
PHOENIX   114 IN 2006  115 IN 1943
YUMA      117 IN 1943  120 IN 1943

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...BKN TO OVC
MID AND HIGH LEVEL DEBRIS CLOUDINESS WILL GRADUALLY THIN THROUGH THE
DAY. CLOUD BASES WILL REMAIN AOA 15 KFT. EAST TO SOUTHEAST SURFACE
WINDS WILL CONTINUE THROUGH THIS EVENING...WITH MID-DAY AND
AFTERNOON GUSTS UP TO 25 KTS POSSIBLE.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOME HIGH DEBRIS CLOUDINESS MAY WORK ITS WAY INTO SOUTHEAST CA
THROUGH THE DAY...THOUGH SKIES ARE EXPECTED TO REMAIN MOSTLY SCT.
WINDS AT KIPL WILL REMAIN LIGHT AND VARIABLE TODAY...WHILE AT KBLH
SOUTHEAST WINDS WITH GUSTS TO NEAR 25 KTS ARE EXPECTED MID-DAY TO
EARLY EVENING. THERE IS A SLIGHT CHANCE OF THUNDERSTORMS EAST OF THE
COLORADO RIVER THIS AFTERNOON AND EVENING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
SLIGHTLY COOLER AFTERNOON HIGH TEMPERATURES ARE EXPECTED THROUGH THE
PERIOD...AS UPPER LEVEL HIGH PRESSURE WEAKENS AND SLIDES FURTHER TO
THE SOUTH. EVEN SO...READINGS WILL STILL BE SLIGHTLY WARMER THAN
NORMAL. AN INCREASE IN MOISTURE IS POSSIBLE AS THE HIGH SLIPS TO THE
SOUTH...THOUGH MINIMUM AFTERNOON DAILY HUMIDITY LEVELS WILL STILL
DIP BELOW 20 PERCENT. OVERNIGHT RECOVERY SHOULD HOWEVER BE MODERATE
TO GOOD. THERE WILL BE A DAILY THREAT OF THUNDERSTORMS...BUT THESE
WILL BE MAINLY CONCENTRATED IN THE HIGHER TERRAIN OF EASTERN AZ.
OUTFLOW BOUNDARIES MOVING INTO THE LOWER DESERTS WILL BE CAPABLE OF
PRODUCING STRONG WIND GUSTS. FURTHER WEST ACROSS SE CA...THE CHANCE
FOR RAIN AND THUNDERSTORM IMPACTS WILL BE EVEN LOWER. WINDS TO
GENERALLY FOLLOW DIURNAL AND TERRAIN DRIVEN HEADINGS...WITH MOSTLY
LIGHT SPEEDS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...EXCESSIVE HEAT WARNING THROUGH THURSDAY EVENING
AZZ020>023-025>028.

CA...EXCESSIVE HEAT WARNING THROUGH THURSDAY EVENING CAZ031>033.

&&

$$

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

DISCUSSION...PERCHA
CLIMATE...PERCHA
AVIATION....MCLANE
FIRE WEATHER...NOLTE/MCLANE/HIRSCH








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