Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 201721
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1020 AM MST SAT DEC 20 2014

.SYNOPSIS...
HIGH PRESSURE OFF THE WEST COAST WILL RESULT IN NEAR NORMAL
TEMPERATURES WITH VARYING AMOUNTS OF HIGH CLOUDS THROUGH THE MIDDLE
OF NEXT WEEK. BY NEXT THURSDAY...A FAST MOVING STORM SYSTEM WILL
MOVE THROUGH THE FOUR CORNERS REGION AND WILL BRING SLIGHTLY COOLER
TEMPERATURES AND INCREASED CLOUDINESS THAT WILL LAST THROUGH FRIDAY.
DRY WEATHER IS EXPECTED NEXT WEEKEND WITH BELOW NORMAL TEMPERATURES.

&&

.DISCUSSION...
REGIONAL IR SATELLITE IMAGERY THIS MORNING REVEALS A LARGE SWATH OF
THICKER UPPER LEVEL CLOUDS OVERSPREADING PORTIONS OF THE WESTERN
UNITED STATES...THE DEVELOPMENT DUE TO AN UPPER LEVEL JET STREAK
OVER NORTHERN CALIFORNIA RIDING OVER THE TOP OF THE STRENGTHENING
EASTERN PACIFIC RIDGE IN PLACE OFF THE WEST COAST. SURFACE
CONDITIONS ACROSS OUR FORECAST AREA REMAIN PERSISTENT...SHOWING
LITTLE CHANGE OVER THE LAST DAY OR TWO...DIURNAL DEW POINT TEMP
TRENDS MAINLY IN THE 30S-40S ACROSS OUR CWA...WITH FORECAST DAYTIME
MAX TEMPERATURES TODAY TOPPING OUT IN THE 60S ACROSS THE LOWER
DESERT ELEVATIONS.

NOT MANY CHANGES TO FORECAST THINKING FOR MUCH OF THE UPCOMING WEEK.
ONCE THE WEAK TROUGH AND ASSOCIATED ONSHORE FLOW MOVES THROUGH
NORTHERN CALIFORNIA TONIGHT...RIDGING WILL STRENGTHEN OFF THE
SOUTHERN CALIFORNIA COAST WITH ANOMALOUSLY HIGH 500MB HEIGHTS
FORECAST TO REMAIN IN PLACE THROUGH AT LEAST WEDNESDAY. THIS WILL
RESULT IN VARYING AMOUNTS OF HIGH CLOUDS AND ABOVE NORMAL
TEMPERATURES. A BLEND OF THE BEST PERFORMING BIAS CORRECTED GUIDANCE
SUGGESTS DAILY HIGHS FROM 65-70 EACH DAY /SLIGHTLY WARMER AROUND
YUMA AND EL CENTRO/ WITH NEAR NORMAL LOWS IN THE MID 40S.

ATTENTION TURNS TO CHRISTMAS DAY AS THERE ARE ONCE AGAIN SOME
DIFFERENCES BETWEEN THE ECMWF AND GFS MODELS. BOTH INDICATE
TROUGHING BUT THE ECMWF HAS ONCE AGAIN RETURNED TO ITS SOLUTION OF A
CLOSED CIRCULATION OVER ARIZONA WITH PRECIP DEVELOPING ACROSS THE
HIGHER TERRAIN NORTH/EAST OF PHOENIX. PARALLEL 13KM GFS IS A BIT
DEEPER WITH THE TROUGH WHEN COMPARED TO THE OPERATIONAL GFS BUT IS
LACKING MOISTURE AS IT MOVES THROUGH THE REGION. ENSEMBLES REMAIN
STEADY AND INDICATE THE OPERATIONAL GFS-TYPE SOLUTION WILL PREVAIL
BUT NOT WANTING TO DISCOUNT THE ECMWF /AND 13KM GFS/ ENTIRELY...I
INTRODUCED VERY LOW END DOUBLE DIGIT POPS NORTH/EAST OF PHOENIX ON
THURSDAY ALONG WITH SLIGHTLY COOLER TEMPERATURES. IMPACTS LOOK
MINIMAL BUT WILL NEED TO KEEP MONITORING SUBSEQUENT MODEL RUNS TO
SEE HOW THEY TREND.  REGARDLESS...A RETURN TO NORTHWESTERLY FLOW
LOOKS LIKELY LATE NEXT WEEK INTO THE WEEKEND.

&&

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

PASSING MID TO HIGH LEVEL CLOUDS EXPECTED AT PERIODS THROUGH THE
WEEKEND...GENERATING BKN TO OVC SKIES AND REMAINING MOSTLY ABOVE
20KFT. SFC WINDS WILL REMAIN LIGHT...GNLY 8KTS OR LESS...AND FOLLOW
TYPICAL DIURNAL HEADINGS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
UPPER LEVEL RIDGING WILL DOMINATE THROUGH A GOOD PORTION...IF NOT
ALL...OF NEXT WEEK WITH ABOVE NORMAL TEMPERATURES AND SLIGHTLY DRIER
CONDITIONS. HUMIDITIES WILL REMAIN FAIRLY HIGH THROUGH THE PERIOD
WITH MINIMUM VALUES STAYING ABOVE 25 PERCENT. WINDS WILL BE LIGHT
FOR THE MOST PART THROUGH WEDNESDAY WITH THE EXCEPTION OF OCCASIONAL
AFTERNOON BREEZINESS. A PACIFIC LOW PRESSURE SYSTEM MAY AFFECT THE
REGION LATE NEXT WEEK BRINGING THE POTENTIAL FOR GUSTY
WINDS...COOLER TEMPERATURES...AND SLIGHT CHANCES FOR PRECIPITATION
ACROSS HIGHER TERRAIN AREAS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MEYERS/LEINS
AVIATION...NOLTE/KUHLMAN
FIRE WEATHER...KUHLMAN





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