Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 231617
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
915 AM MST WED APR 23 2014

.SYNOPSIS...
THE WEATHER DISTURBANCE THAT BROUGHT GUSTY WINDS AND AREAS OF
BLOWING DUST TO THE REGION ON TUESDAY IS EXPECTED TO BRING COOLER
TEMPERATURES TODAY AS IT MOVES OFF TO THE EAST. 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...
ANOTHER MORE COMPACT SHORT-WAVE TROUGH IS EVIDENT IN WV IMAGERY
ACROSS NW AZ. THIS SYSTEM WILL MOVE RAPIDLY EASTWARD...BRINGING A
REINFORCING SHOT OF DRIER AIR TO THE REGION TODAY. OBSERVATIONS
INDICATE THAT SURFACE DEWPOINTS ARE ALREADY AS LOW AS THE TEENS IN
THE PHOENIX METRO AREA. STILL EXPECTING COOLER TEMPERATURES
TODAY...AS MUCH AS 10 DEGREES LOWER THAN THOSE OBSERVED YESTERDAY.
FORECAST REMAINS ON TRACK AND ONLY MINOR ADJUSTMENTS TO THE
SHORT-TERM TEMPERATURES ARE ANTICIPATED.

&&


.PREVIOUS DISCUSSION...
WEDNESDAY AND THURSDAY...
THE DRY COOL FRONT THAT BROUGHT OUR CWA GUSTY WINDS...PATCHY BLOWING
DUST...AND HIGH FIRE DANGER ON TUESDAY HAS FINALLY PUSHED INTO
SOUTHEASTERN AZ THIS MORNING. THE MAIN IMPACTS FROM THIS FRONT TODAY
WILL BE SOMEWHAT COOLER TEMPERATURES AND LOWER DEWPOINTS...ALONG
WITH SOME GUSTY AFTERNOON BREEZES ACROSS SOUTHWEST AND SOUTH-CENTRAL
AZ. CURRENT FORECAST SOUNDINGS FOR THE PHX AREA ARE INDICATING THAT
850MB TEMPS WILL DROP FROM YESTERDAY`S 22C TO AROUND 17C BY THIS
AFTERNOON...WHICH SHOULD RESULT IN ABOUT 8-10 DEGREES OF COOLING AT
THE SFC...WITH HIGHS REMAINING MOSTLY IN THE MID TO UPPER 80S
TODAY...WHICH IS NOW RIGHT AROUND NORMAL FOR THIS TIME OF YEAR.
NIGHTTIME LOWS TONIGHT SHOULD ALSO BE NOTICEABLY COOLER...WITH MOST
OUTLYING LOWER DESERT LOCATIONS SEEING LOWS IN THE 50S UNDER MOSTLY
CLEAR SKIES. WEAK RIDGING AHEAD OF THE NEXT UPPER TROF IS THEN
EXPECTED TO BRING SOMEWHAT WARMER TEMPERATURES ON THURSDAY...WITH
LOWER DESERT HIGHS PUSHING BACK INTO THE LOW TO MID 90S.

FRIDAY THROUGH SUNDAY...
THE NEXT PACIFIC SYSTEM THAT WILL BE AFFECTING OUR AREA FROM FRIDAY
ONWARD INTO THE WEEKEND CAN ALREADY BE SEEN ON LATEST IR SATELLITE
IMAGERY JUST BEGINNING TO MOVE SOUTHWARD FROM THE GULF OF ALASKA
INTO THE EASTERN PACIFIC. THE LATEST GFS...EURO...AND GEM HAVE NOW
COME INTO VERY GOOD AGREEMENT THAT THIS NEXT SYSTEM WILL BE THE
STRONGEST SYSTEM THAT WE HAVE SEEN FOR A WHILE. THEY ALL NOW MOVE A
RATHER ROBUST...AND COLD UPPER LOW INLAND OVER CENTRAL AND SOUTHERN
CA BY LATE FRIDAY EVENING AND EARLY SATURDAY...THEN ACROSS NORTHERN
ARIZONA DURING THE DAY ON SATURDAY...AND INTO NEW MEXICO BY SUNDAY
MORNING.

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...
NO SIGNIFICANT AVIATION CONCERNS THROUGH THURSDAY MORNING...WITH
TIMING OF WIND SHIFTS THE PRIMARY FORECAST CHALLENGE. WITH FAIRLY
GOOD CONFIDENCE...A PERIOD OF VARIABLE SFC WINDS WILL PREVAIL THIS
MORNING DESPITE A PERSISTENT WEST 5-10KT WINDS 2K-4K ABOVE THE
GROUND. EVENTUALLY LATE THIS MORNING...WLY WINDS WILL MIX TO THE
GROUND. THERE MAY BE A PERIOD OF A FEW HIGHER GUSTS UP TO
20KT...THOUGH THESE CONDITIONS SHOULD BE MORE TEMPORALLY LIMITED.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SFC WINDS WILL EVENTUALLY VEER TO A MORE NLY DIRECTION THIS
MORNING...AND CONFIDENCE IS FAIRLY GOOD THAT A FEW HIGHER GUSTS WILL
MATERIALIZE BY LATE MORNING (PARTICULARLY AT KBLH). NO OTHER
AVIATION CONCERNS AS THE PRESSURE GRADIENT WEAKENS BY LATE
AFTERNOON...AND SFC WINDS FALL BACK TO AROUND 5KT AND BECOME MORE
WLY IN DIRECTION WITH NOCTURNAL DECOUPLING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...
A VERY STRONG UPPER LEVEL LOW WILL APPROACH THE AREA ON FRIDAY AND
MOVE THROUGH THE DISTRICTS ON SATURDAY. AHEAD OF THIS WEATHER
SYSTEM...WINDS WILL INCREASE AND BECOME FREQUENTLY GUSTY FRIDAY
AFTERNOON AND EVENING. THE STRONGEST WINDS FRIDAY WILL BE
EXPERIENCED ACROSS SE CALIFORNIA AND THE LOWER COLORADO RIVER
VALLEY...AND ITS POSSIBLE CRITICAL THRESHOLDS MAY BE MET.
TEMPERATURES ON SATURDAY WILL PLUMMET TO WELL BELOW NORMAL
LEVELS...AND HUMIDITY LEVELS WILL INCREASE (ALONG WITH A POSSIBILITY
OF LIGHT RAIN). THIS MAY OTHERWISE LIMIT A MUCH HIGHER FIRE
DANGER...BECAUSE WINDS SATURDAY ACROSS THE ENTIRE REGION WILL BE
UNUSUALLY STRONG FOR MUCH OF THE DAY (LIKELY GUSTING AOA 40 MPH).
COOLER WEATHER WILL LINGER SUNDAY WITH A WARMING TREND EARLY NEXT
WEEK. AS TEMPERATURES RECOVER NEXT WEEK...AFTERNOON HUMIDITIES WILL
ONCE AGAIN DROP INTO THE SINGLE DIGITS WITH ONLY FAIR OVERNIGHT
RECOVERY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

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









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