Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 240355
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
855 PM MST WED APR 23 2014

.SYNOPSIS...
WARMER TEMPERATURES WILL MAKE A RETURN THURSDAY AND FRIDAY.
ANOTHER...MUCH STRONGER LOW PRESSURE SYSTEM WILL THEN AFFECT THE
REGION FROM FRIDAY ONWARD INTO THE UPCOMING WEEKEND. BREEZY TO WINDY
CONDITIONS CAN BE EXPECTED ALONG WITH MUCH COOLER TEMPERATURES ON
SATURDAY. THERE IS ALSO A CHANCE OF SHOWERS LATE FRIDAY NIGHT INTO
SATURDAY NIGHT...MAINLY FOR THE HIGHER TERRAIN OF SOUTH-CENTRAL
ARIZONA. HIGH PRESSURE BUILDING BACK NORTHWARD OVER THE WESTERN US
IS THEN EXPECTED TO BRING WARMER TEMPERATURES FOR THE EARLY AND
MIDDLE PARTS OF NEXT WEEK.

&&

.DISCUSSION...
COOLER BUT CONTINUED BREEZY CONDITIONS LINGERED TODAY IN THE WAKE OF
THE PASSING SHORTWAVE IMPULSE...WHICH HAS NOW CLEAR THE FOUR CORNER
AND CLEARING THE ROCKIES FRONT RANGE THIS EVENING. WHILE SURFACE
CONDITIONS IN TERMS OF DEWPOINTS HAVE DRIED SUBSTANTIALLY
TODAY...WITH SINGLE DIGITS TO LOW 10S OBSERVATIONS...WATER VAPOR
IMAGERY AND UPSTREAM RAOBS SHOW SOME HIGH LEVEL MOISTURE STREAMING
THROUGH THE SUBTLE RIDGE HEIGHTS TO OUR WEST. PATCHES OF HIGH CLOUDS
WILL CONTINUE TO STREAM FROM NORTHWEST TO SOUTHEAST TONIGHT...AT
MOST GENERATING BRIEF PERIODS OF PARTLY CLOUDY SKIES. SURFACE TEMPS
RUNNING 7 TO 10 DEGREES COOLER THAN THIS TIME TUESDAY EVENING...SO
EVEN WITH THE QUICK-PASSING CLOUDS...THINK MIN T FORECAST FOR
TONIGHT IS IN GOOD SHAPE. NO MAJOR UPDATES NEEDED...REMAINDER
OF THE DISCUSSION STILL APPLIES.

&&

.PREVIOUS DISCUSSION /ISSUED AT 255 PM MST/PDT/...
SHORT-WAVE RIDGE WILL BUILD IN OVERNIGHT...RESULTING IN MOSTLY CLEAR
SKIES AND LIGHT WINDS. THIS WILL PROMOTE EFFICIENT RADIATIONAL
COOLING AND TEMPERATURES NEAR OR EVEN SLIGHTLY BELOW NORMAL.

REBOUND IN TEMPERATURES IS EXPECTED THURSDAY AS A SHORT-WAVE RIDGE
IN THE SUBTROPICAL EASTERN PACIFIC BUILDS EASTWARD. ATTENTION WILL
THEN TURN TO A DEEPENING LOW PRESSURE SYSTEM ALONG THE WEST COAST
FRIDAY. BIGGEST IMPACT ACROSS THE FORECAST AREA WILL BE AN INCREASE
IN WIND AHEAD OF THIS SYSTEM. WINDS WILL BE STRONGEST ACROSS SE CA
WHERE GUSTS TO 35 MPH WILL BE POSSIBLE AND UP TO 30 MPH ACROSS
SOUTH-CENTRAL AZ INCLUDING THE PHOENIX METRO AREA.

PREVIOUS DISCUSSION /ISSUED AT 225 AM MST/PDT/...
THE MODELS ARE ALL NOW SHOWING VERY SHARP HEIGHT FALLS AND
TEMPERATURE DROPS AS THIS SYSTEM MOVES THROUGH...WITH 500MB HEIGHTS
OVER THE PHX AREA FALLING FROM AROUND 572DM ON FRIDAY AFTERNOON TO
AROUND 550-552DM BY SATURDAY AFTERNOON...WITH 850MB TEMPERATURES
FALLING FROM AROUND 19C TO 7C DURING THE SAME PERIOD. ALTHOUGH THERE
WILL LIKELY NOT BE A WHOLE LOT OF MOISTURE ASSOCIATED WITH THIS
SYSTEM...WITH PWATS ONLY BRIEFLY RISING INTO THE 0.75-0.85 INCH
RANGE...THE IMPRESSIVE DYNAMICS AND COOLING THAT THIS SYSTEM WILL
POSSESS WILL LIKELY PRODUCE AT LEAST SOME SHOWER ACTIVITY DURING THE
DAY ON SATURDAY ACROSS SOUTH-CENTRAL AZ ALONG AND JUST AHEAD OF THE
MAIN FRONT. HOWEVER...THE BIGGEST IMPACT FROM THIS SYSTEM WILL
LIKELY BE THE WINDS...WITH WIDESPREAD ADVISORY-LEVEL WINDS POSSIBLE
ON SATURDAY AS EFFICIENT MIXING WILL LIKELY ALLOW 35-40KT 700MB
WINDS TO BE BROUGHT ALL THE WAY DOWN TO THE SFC...WITH BLOWING DUST
LIKELY TO BE A PROBLEM AS WELL. AFTER ANOTHER DAY OF 90+ DEGREE
TEMPERATURES ON FRIDAY...IT NOW LOOK LIKELY THAT HIGHS WILL REMAIN
WELL DOWN IN THE 70S ON SATURDAY. SUNDAY LOOKS LIKE IT WILL BE A
MUCH QUIETER DAY AS THE SYSTEM MOVES OFF RAPIDLY TO THE EAST...WITH
HIGHS REBOUNDING INTO THE LOW 80S ACROSS THE LOWER DESERTS UNDER
MOSTLY CLEAR SKIES...WITH JUST SOME AFTERNOON WESTERLY BREEZES.

MONDAY THROUGH WEDNESDAY...
ALTHOUGH THERE ARE DIFFERENCES BETWEEN THE MODELS...WITH THE EURO
BEING THE SLOWEST/COOLEST AND THE GEM BEING THE
FASTEST/WARMEST...THEY ALL ARE ATTEMPTING TO REBUILD RIDGING BACK
NORTHWARD OVER THE REGION FOR THE EARLY AND MIDDLE PART OF NEXT
WEEK...WITH TEMPERATURES WARMING BACK UP WELL INTO THE 90S UNDER
MOSTLY CLEAR SKIES. HOWEVER...WIDESPREAD TRIPLE-DIGIT TEMPERATURES
DO NOT APPEAR LIKELY AT THIS TIME...SINCE LONG-WAVE TROUGHING OVER
THE CENTRAL CONUS SHOULD KEEP OUR UPPER-LEVEL FLOW A NORTHWESTERLY
ONE.

&&

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

LIGHTER WINDS EXPECTED OVERNIGHT FOR THE TERMINALS WITH SPEEDS
STAYING MOSTLY UNDER 8KTS...WITH W/SW HEADINGS FOR THE PHX AREA
AIRFIELDS AND W/NW FOR KIPL AND KBLH. WINDS OVERNIGHT AND CLOSER
TOWARDS SUNRISE MAY BECOME LIGHT ENOUGH TO WARRANT VRB HEADINGS. THE
USUAL EASTERLY DRIFT SHOULD WORK IN FOR THE PHX AREA TERMINALS NEAR
OR AFTER 24/0800Z. SKIES WILL REMAIN MOSTLY CLEAR...SAVE FOR A FEW
HIGH CLOUDS MOVING FROM NW TO SE ACROSS ARIZONA OVERNIGHT.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
UPPER LOW WILL APPROACH THE AREA FRIDAY AND MOVE THROUGH THE AREA ON
SATURDAY. WINDS WILL ONCE AGAIN BE GUSTY ACROSS THE ENTIRE REGION ON
SATURDAY...HOWEVER MOISTURE WILL BE ON THE INCREASE AND TEMPERATURES
WILL BE SUBSTANTIALLY COOLER THAN NORMAL...THUS CRITICAL THRESHOLDS
SHOULD NOT BE REALIZED. MUCH LIGHTER WINDS ARE EXPECTED FROM SUNDAY
ONWARD ALTHOUGH TEMPERATURES WILL SLOWLY RECOVER BACK TOWARD NORMAL
VALUES. RECOVERIES WILL GRADUALLY DETERIORATE AS THE WEEK
PROGRESSES.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FIRE WEATHER WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING
     AZZ020-025.

CA...FIRE WEATHER WATCH FROM FRIDAY AFTERNOON THROUGH FRIDAY EVENING
     CAZ031.

$$

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

DISCUSSION...NOLTE
PREVIOUS DISCUSSION...HIRSCH/PERCHA
AVIATION....NOLTE
FIRE WEATHER...LEINS







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