Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 060455
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
955 PM MST TUE MAY 5 2015

.SYNOPSIS...EXPECT SHOWERS TO DIMINISH AND SKIES BEGIN TO CLEAR
TODAY AS THE LOW PRESSURE SYSTEM MOVES EAST THROUGH NEW MEXICO. A
STRONGER EASTERN PACIFIC WEATHER SYSTEM WILL MOVE INTO THE REGION
BY FRIDAY...BRINGING EVEN COOLER TEMPERATURES...GUSTY WINDS...AND
MORE PRECIPITATION CHANCES. A SLOW WARMING TREND COMMENCES THROUGH
THE WEEKEND INTO EARLY NEXT WEEK AS HIGH PRESSURE GRADUALLY
REBUILDS OVER THE DESERT SOUTHWEST.

&&

.DISCUSSION...
YESTERDAYS LOW PRESSURE SYSTEM NOW OVER THE PLAINS STATES THIS
EVENING. SHORT WAVE RIDGING IN PLACE OVER OUR FORECAST AREA IN ITS
WAKE. A WEAK UPPER DISTURBANCE APPROACHING FROM THE WEST IS
SPREADING HIGH CLOUDS OVER THE AREA WHICH WILL BE IN PLACE
INTO THE MORNING HOURS BEFORE CLEARING OUT. OVER THE PACIFIC
NORTHWEST AND SOUTHWEST CANADA IS A LARGE LOW PRESSURE SYSTEM. IN
BETWEEN THE PLAINS LOW AND THE NORTHWEST LOW IS A NARROW POSITIVELY
TILTED RIDGE. LATEST MODELS AGREE THAT THE WEATHER DISTURBANCE
NEAR THE SOUTHERN CALIFORNIA COAST WILL MOVE INLAND BUT WEAKEN AS
THE NORTHWEST LOW PRESSES SOUTHWARD. BY THURSDAY AFTERNOON...THE
PACIFIC LOW BECOMES CENTERED OVER CENTRAL CALIFORNIA. OUR AREA
REMAINS DRY THROUGH THURSDAY WITH MODERATE AFTERNOON BREEZES. NO
CHANGES TO THE FORECAST AT THIS TIME.

&&

.PREVIOUS DISCUSSION ISSUED 244 PM MST/PDT...
TONIGHT THROUGH WEDNESDAY...SATELLITE IMAGERY REVELS THE CENTER OF
THE LOW MAKING ITS WAY INTO NORTHERN NEW MEXICO THIS AFTERNOON. A
FEW ISOLATED THUNDERSTORMS ARE FORMING ACROSS NORTHEAST PORTIONS OF
THE STATE...OTHERWISE CUMULUS FIELDS ARE ONLY SHOWING MODEST
VERTICAL DEVELOPMENT ACROSS OUR EASTERN ZONES...AND LITTLE IN THE
WAY OF PRECIP IS OBSERVED. HOWEVER...THERE MIGHT BE AN ISOLATED
SHOWER THAT LINGERS INTO THE EARLY EVENING HOURS OVER THE HIGHER
TERRAIN NORTH AND EAST OF PHOENIX BEFORE THE LOW-MID LEVEL CLOUD
DECKS FINALLY THIN OUT AND DISAPPEAR.

A DRIER SUBSIDENT FLOW ACROSS SOUTHERN CALIFORNIA AND SOUTHWESTERN
ARIZONA HAS LED TO A LACK OF CLOUD COVER AND ALLOWED TEMPS TO WARM
UP NICELY TO NEAR 90 DEGREES THIS AFTERNOON ACROSS THE LOWER
DESERTS. THIS WEAK RIDGING WILL CONTINUE TO HOLD OVER THE SOUTHWEST
DESERTS THROUGH WEDNESDAY...KEEPING CONDITIONS DRY WITH A COUPLE
DEGREES OF WARMING MAINLY OVER OUR EASTERN ZONES IN SOUTH-CENTRAL
ARIZONA...DAYTIME TEMPS ONCE AGAIN TOPPING OUT IN THE UPPER 80S/LOW
90S.

PREVIOUS DISCUSSION...
THURSDAY THROUGH SATURDAY...ALTHOUGH LATEST MODEL SUITES ARE
CONSISTENT WITH EARLY RUNS ON THE BASIC IDEA THAT ANOTHER UPPER LOW
CENTER WILL AFFECT OUR REGION DURING THIS PERIOD...THERE CONTINUE TO
BE SOME DIFFERENCES BETWEEN THE MODEL SUITES REGARDING THE TRACK OF
THIS SYSTEM. WHILE THE EURO AND GEM MODELS CONTINUE TO TAKE THIS LOW
CENTER TO OUR NORTH...ALONG THE AZ/UT BORDER...THE GFS NOW MOVES THE
UPPER LOW CENTER RIGHT ACROSS OUR CWA. IF THE GFS WERE TO
VERIFY...EVEN COOLER TEMPERATURES WOULD RESULT...WITH MANY LOWER
DESERT LOCATIONS SEEING HIGH ONLY IN THE 70S ON FRIDAY AND
SATURDAY...ALONG WITH A CHANCE FOR SHOWERS AS WELL. ALTHOUGH ALL
THREE MODELS STILL INCREASE SFC WINDS ACROSS THE REGION DURING THIS
PERIOD...THEY ALL NOW KEEP MINIMUM RH/S ELEVATED A BIT...MOSTLY IN
THE UPPER TEENS AND 20S...WHICH WOULD KEEP FIRE DANGER LEVELS FROM
RISING AS MUCH AS HAD BEEN EARLIER EXPECTED. I HAVE DECIDED THE
RAISE POPS AND COOL TEMPERATURES A BIT TO REFLECT THIS POSSIBLE GFS
SOLUTION.

SUNDAY THROUGH TUESDAY...ALL THREE GLOBAL MODELS CONTINUE TO SHOW
HIGH PRESSURE SLOWLY REBUILDING OVER THE REGION AS THE
AFOREMENTIONED UPPER LOW MOVES OFF TO THE EAST...WITH DRY CONTINUES
AND A GRADUAL WARMING TREND FORECAST THROUGH THIS PERIOD.

&&

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

YESTERDAYS LOW PRESSURE SYSTEM NOW OVER THE PLAINS STATES.
AOME ALTOCUMULUS WILL LINGER BUT WITH SPOTTY COVERAGE. CIRRUS
INCREASES TONIGHT AHEAD OF A WEAK DISTURBANCE CENTERED JUST OFF THE
SOUTHERN CALIFORNIA COAST AS OF 04Z. EXPECT LIGHT SURFACE WINDS
OVERNIGHT AND INTO THE MORNING HOURS BEFORE SOUTH AND SOUTHWEST
WINDS DEVELOP WEDNESDAY AFTERNOON WITH SOME MODEST GUSTINESS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...

THURSDAY THROUGH MONDAY...A SERIES OF PACIFIC WEATHER SYSTEMS WILL
MOVE INTO THE WESTERN STATES MAINLY NORTH OF SOUTHERN AZ THROUGH
SATURDAY...RESULTING IN BELOW NORMAL TEMPERATURES. PARTLY CLOUDY
SKIES ARE EXPECTED WITH BREEZY AFTERNOONS. HOWEVER THE STRONGEST
WIND PERIOD WILL BE THURSDAY AND FRIDAY WITH WINDS 15 TO 25 MPH AND
POSSIBLE GUSTS TO 30 MPH. A SLIGHT CHANCE OF SHOWERS IS POSSIBLE
FRIDAY AND SATURDAY AFTERNOONS MAINLY OVER SOUTHERN GILA COUNTY. A
HIGH PRESSURE SYSTEM WILL REBUILD OVER THE REGION LATE SUNDAY AND
MONDAY FOR CLEAR SKIES...LIGHT WIND...AND WARMER TEMPERATURES.
MINIMUM RELATIVE HUMIDITY IN GENERAL WILL RANGE FROM 15 TO 20
PERCENT...FALLING MONDAY INTO THE 10 TO 15 PERCENT RANGE. OVERNIGHT
RECOVERY WILL BE POOR TO FAIR.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&

$$

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

DISCUSSION...AJ
PREVIOUS DISCUSSION...MEYERS/PERCHA
AVIATION...AJ
FIRE WEATHER...VASQUEZ



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