Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 020315
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
815 PM MST WED APR 1 2015

.SYNOPSIS...
A DRY WEATHER SYSTEM WILL MOVE INTO THE REGION FROM THE GREAT BASIN
LATE TONIGHT THROUGH FRIDAY...USHERING IN COOLER TEMPERATURES AND
INCREASING WINDS. DRY CONDITIONS WILL REMAIN THROUGH THE WEEKEND
WITH CONTINUED ABOVE NORMAL TEMPERATURES WITH DAYTIME HIGHS IN THE
UPPER 80S TO LOW 90S. AN ACTIVE UPPER LEVEL PATTERN WILL LINGER OVER
THE WEST INTO NEXT WEEK...RESULTING IN NEAR OR POSSIBLY EVEN BELOW
NORMAL TEMPERATURES FOR OUR AFTERNOONS AND MILD MORNINGS.

&&

.DISCUSSION... DRY WESTERLY FLOW WAS IN PLACE THIS EVENING ACROSS
ARIZONA/SERN CA PER THE 00Z AREA PLOT AND RAOB DATA. PWAT VALUES
ACROSS ARIZONA WERE BELOW ONE QUARTER INCH...AND SURFACE DEWPOINTS
OVER THE LOWER DESERTS WERE MOSTLY RUNNING IN THE 20S. IR IMAGERY
EARLY THIS EVENING SHOWED GENERALLY CLEAR SKIES ACROSS THE AREA
WITHE THICKER CIRRUS MOVING BY WELL TO OUR NORTH MAINLY THRU
NEVADA/UTAH AND FAR NRN AZ. FOR THE REST OF TONIGHT EXPECT SOME
INCREASE IN HIGH CLOUDS AHEAD OF AN APPROACHING DISTURBANCE...ALONG
WITH MOSTLY LIGHT WINDS AND MILD OVERNIGHT LOW TEMPS. NO UPDATES
NEEDED TO THE FORECAST ATTM.

.PREVIOUS DISCUSSION...
ZONAL FLOW REMAINS IN PLACE ACROSS THE REGION THIS AFTERNOON...AS A
WEAK UPSTREAM SHORTWAVE TROUGH MOVES THROUGH NORTHERN CALIFORNIA. AS
HEIGHTS ARE SLIGHTLY LOWER TODAY COMPARED TO YESTERDAY...TEMPERATURES
ARE ALSO RUNNING A FEW DEGREES COOLER THAN THIS TIME TUESDAY
AFTERNOON. MOST DESERT LOCALES WERE GENERALLY IN THE MID/UPPER 80S AS
OF 20Z...STILL ABOVE NORMAL FOR EARLY APRIL.

FORECAST CONCERNS IN THE SHORT TERM ARE PRIMARILY FOCUSED ON THE
PASSAGE OF THE UPSTREAM TROUGH ON THURSDAY. THE SYSTEM IS MOISTURE
STARVED AND PRECIP CHANCES ARE NIL...HOWEVER IN TYPICAL SPRINGTIME
FASHION THE TROUGH WILL SWEEP THROUGH AND USHER IN LOWER DEWPOINTS
AND INCREASED WINDS. GRADIENTS WILL BE TIGHTEST ACROSS
NORTHERN/EASTERN ARIZONA AND THESE AREAS WILL LIKELY SEE THE
STRONGEST WINDS...SIMILARLY STRONG DRY ADVECTION DOWN THE COLORADO
RIVER WILL ALSO PRODUCE A BRIEF PERIOD OF AFTERNOON BREEZINESS ON
THURSDAY. THAT BEING SAID...IT STILL APPEARS THAT CRITICAL FIRE
WEATHER THRESHOLDS WILL NOT BE REALIZED OVER A PROLONGED PERIOD OF
TIME AND A WIDESPREAD AREA WITH THE PASSAGE OF THIS EVENT...AND NO
FIRE WEATHER HEADLINES SEEM WARRANTED AT THIS TIME. THE TROUGH WILL
USHER IN SLIGHTLY COOLER TEMPERATURES ALTHOUGH HIGHS THURSDAY AND
FRIDAY /WHILE COOLER/ WILL REMAIN ABOVE NORMAL.

FORECAST SOLNS IN THE EXTENDED REMAIN IN FAIRLY GOOD AGREEMENT
THROUGH ABOUT THE MIDDAY MONDAY TIME FRAME. LONGWAVE TROUGHING HOLDS
OVER MUCH OF THE WEST WITH EMBEDDED SHORTWAVE PASSING THROUGH THE
REGION TO OUR NORTH. AFTER MONDAY...A MORE ORGANIZED PACIFIC LOW IS
PROGGED TO DEVELOP OVER THE PACIFIC NW AND THEN EXPAND DOWN THE WEST
COAST. OUT OF THE 00Z OPERATIONS GUIDANCE...THE ECMWF SOLN IS THE
COLDEST AND DEEPEST SWEEPING THE SYSTEM THROUGH AZ AS A CUT-OFF LOW.
THE GFS/GEM SOLNS FAVOR A MORE OPEN WAVE WITH A LESSER SOUTHERN
EXTENT. ENSEMBLE SPREAD REMAINS HIGH...PARTICULARLY OVER THE
NORTHEAST PACIFIC AND OVER THE PACIFIC NW WITH THE GENESIS OF THIS
SYSTEM. TAKING A MEDIAN VALUE FORECAST OF ALL AVAILABLE TEMPERATURE
GUIDANCE ALONG WITH A HEAVY BLEND OF CONSENSUS GUIDANCE RESULTS IN
THE POSSIBILITY OF BELOW NORMAL TEMPERATURES DURING THE MIDDLE OF
NEXT WEEK. NORMALS FOR THIS PERIOD IN PHOENIX AND YUMA ARE 82/83 AND
84/85 DEGREES RESPECTIVELY. CONFIDENCE IS MARGINAL IN THESE FORECAST
VALUES AND EVEN LOWER IN THE TIMING AND MOVEMENT OF THE WEATHER
SYSTEM RESPONSIBLE FOR THE COOL DOWN. DESPITE THE DEPTH
DIFFERENCES...ALL SOLNS ATTM INDICATE THIS SYSTEMS WILL GENLY BE ON
THE DRIER SIDE. SOME MOISTURE MAY WORK INTO EASTERN AZ/MOGOLLON RIM
AND COULD RESULT IN SOME PRECIP ACTIVITY. SLIGHT BLEND OF (ABOUT 5
PERCENT OVER EACH 12 HR PERIOD) WAS WORKED INTO THE EXTENDED POP
GRIDS. RESULTING POPS DO NOT GENERATE ANY SENSIBLE WEATHER...BUT AT
LEAST A TREND WAS INTRODUCED FOR THE MIDDLE PARTS OF NEXT WEEK.

&&

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

LOCALLY BREEZY CONDITIONS HAVE DISSIPATED FOLLOWING SUNSET AND WE
CAN EXPECT MOSTLY LIGHT AND DIURNAL WINDS AT THE TAF SITES OVERNIGHT
AND INTO THE MID MORNING HOURS THURSDAY. A WEATHER SYSTEM PASSING BY
TO OUR NORTH THURSDAY WILL TIGHTEN GRADIENTS AND LEAD TO ANOTHER
BREEZY AFTERNOON TOMORROW...WITH WINDS IN THE CENTRAL DESERTS
TURNING BACK TO THE WEST BY AROUND NOON. WE MAY SEE A FEW GUSTS IN
EXCESS OF 18-20KT AFTER 20Z THURSDAY. WINDS WILL LIKELY FAVOR THE
NORTH THURSDAY AFTN AT BOTH KIPL AND KBLH. AS FOR THE SKY...SOME
INCREASE IN HIGH CLOUDS IS EXPECTED LATER TONIGHT AND WE CAN EXPECT
SCT-BKN CIRRUS DECKS BY 12Z...PERSISTING THROUGH THE DAY TOMORROW.
QUITE A BIT OF FILTERED SUNSHINE IS LIKELY THURSDAY WITH BKN DECKS
MOSTLY ON THE THIN SIDE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
FRIDAY THROUGH TUESDAY...A WEAK HIGH PRESSURE SYSTEM WILL BUILD OVER
THE REGION FRIDAY AND SATURDAY FOR MUCH LIGHTER AFTERNOON WIND...
FOLLOWED BY MORE WEATHER DISTURBANCES AND GUSTY AFTERNOON WEST WIND
15 TO 30 MPH SUNDAY...MONDAY...AND TUESDAY. NO PRECIPITATION IS
EXPECTED THIS PERIOD. MINIMUM RELATIVE HUMIDITIES WILL RANGE FROM 5
TO 10 PERCENT. FAIR RECOVERY IS EXPECTED OVERNIGHT. MARGINAL FIRE
WEATHER CONDITIONS ARE EXPECTED SUNDAY AND MONDAY AFTERNOONS DUE TO
WIND AND LOW HUMIDITY.

&&

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

&&

$$

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

DISCUSSION...CB
PREVIOUS DISCUSSION...LEINS/NOLTE
AVIATION....CB
FIRE WEATHER...VASQUEZ


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