Area Forecast Discussion
Issued by NWS Phoenix, AZ

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FXUS65 KPSR 020412
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
912 PM MST SUN MAY 1 2016

.SYNOPSIS...
THE LOW PRESSURE SYSTEM THAT BROUGHT SHOWERS AND BELOW-NORMAL
TEMPERATURES TO THE REGION OVER THE LAST FEW DAYS IS EXPECTED TO
MOVE OFF TO THE NORTHEAST TONIGHT AND MONDAY. THIS WILL ALLOW HIGH
PRESSURE TO REBUILD OVER THE DESERT SOUTHWEST FROM MONDAY THROUGH
THURSDAY...RESULTING IN MOSTLY CLEAR SKIES AND A STRONG WARMING
TREND. ANOTHER PACIFIC WEATHER SYSTEM IS STILL FORECAST TO MOVE INTO
THE AREA NEXT FRIDAY AND THE WEEKEND...BRINGING MUCH COOLER
TEMPERATURES...BREEZY CONDITIONS...AND A SLIGHT CHANCE OF SHOWERS.

&&

.DISCUSSION...
SKIES ARE CLEARING RAPIDLY ACROSS THE DESERT SOUTHWEST THIS EVENING.
THIS IS LIKELY A RESULT OF THE STRONG HEIGHT RISES...GENERALLY
AROUND 80 METERS AT 500 MB OVER THE PAST 12 HOURS. WINDS ALSO
CONTINUE TO SUBSIDE...WHICH WILL PROMOTE FAVORABLE CONDITIONS FOR
RADIATIONAL COOLING. LOW TEMPERATURES WILL AGAIN BE AT OR BELOW
NORMAL FOR MOST SPOTS. MINOR ADJUSTMENTS WERE MADE TO THE SHORT-TERM
FORECAST THIS EVENING...MAINLY TO ACCOUNT FOR THE CLEARING SKIES AND
TO ESSENTIALLY REMOVE ANY CHANCE OF MEASURABLE PRECIPITATION.

&&

.PREVIOUS DISCUSSION...

TONIGHT THROUGH MONDAY...

THE COLD UPPER LOW CENTER THAT BROUGHT BELOW-NORMAL TEMPERATURES AND
SHOWERS TO THE REGION OVER THE LAST FEW DAYS IS NOW LIFTING OUT TO
THE NORTHEAST...AS ANOTHER...MUCH WEAKER SHORTWAVE MOVES INLAND INTO
CENTRAL CA/NV. AS HEIGHTS/TEMPERATURES ALOFT GRADUALLY RISE THIS
EVENING AND TONIGHT...THE SPRINKLE/LIGHT SHOWER ACTIVITY THAT IS
BEING DETECTED THIS AFTERNOON ON RADAR ACROSS SOUTH-CENTRAL AZ IS
EXPECTED TO END AROUND/AFTER SUNSET...WITH SKIES BECOMING CLEAR-
PARTLY CLOUDY OVER ALL OF OUR CWA BY LATE TONIGHT. THE WARMING
AIRMASS WILL LIKELY KEEP OVERNIGHT LOWS A BIT WARMER AT MOST
LOCATIONS THAN WHAT WAS OBSERVED LAST NIGHT...IN SPITE OF LESS CLOUD
COVER. CONTINUED WARMING ALOFT WILL ALSO ALLOW TEMPERATURES TO WARM
UP INTO THE UPPER-80S TO NEAR 90 RANGE ON MONDAY UNDER MOSTLY CLEAR
SKIES. HOWEVER...THE AFOREMENTIONED SHORTWAVE...THAT IS NOW MOVING
INTO CENTRAL CA...WILL LIKELY KEEP MOST LOWER DESERT LOCATIONS BELOW
THE 90 DEGREE MARK ON MONDAY...AS IT MOVES EASTWARD OVER NORTHERN AZ.

TUESDAY THROUGH WEDNESDAY...

CURRENT GLOBAL MODEL SUITES CONTINUE TO SHOW RATHER STRONG HIGH
PRESSURE RIDGING BUILDING EASTWARD INTO THE REGION DURING THIS
PERIOD. THE COMBINATION OF 500MB HEIGHTS IN THE 578-580DM RANGE AND
1000-500MB THICKNESSES AOA 570DM...ALONG WITH MOSTLY CLEAR SKIES
WILL CERTAINLY ALLOW TEMPERATURES TO RISE WELL UP INTO THE 90S EACH
DAY...WITH WEDNESDAY LIKELY BEING THE WARMEST DAY...AS LOW-LEVEL
SOUTHERLY FLOW DEVELOPS OVER THE REGION. HOWEVER...OUTSIDE OF
PERHAPS A FEW OF THE VERY WARMEST SPOTS...IT STILL APPEARS THE MOST
LOCATIONS WILL SEE HIGHS FALL SHORT OF 100 DEGREES EACH DAY...WITH
EVEN THE WARMEST NUMERICAL GUIDANCE STILL KEEPING PHOENIX SKY HARBOR
BELOW 100 AS WELL.

THURSDAY THROUGH SUNDAY...

ALL OF THE GLOBAL MODEL SUITES...AND THE VAST MAJORITY OF THEIR
RESPECTIVE ENSEMBLE MEMBERS CONTINUE TO BRING ANOTHER COLD UPPER LOW
SOUTHWARD INTO THE REGION DURING THIS PERIOD...AS THE OVERALL LONG-
WAVE PATTERN OVER THE NORTH PACIFIC AND NORTH AMERICA UNDERGOES
SIGNIFICANT AMPLIFICATION. ALTHOUGH THIS NEW SYSTEM WILL LIKELY BE
AT LEAST AS COLD AS THE ONE THAT HAS AFFECTED US OVER THE PAST FEW
DAYS...IT APPEARS THAT IT WILL BE A SOMEWHAT DRIER ONE...LIKELY DUE
TO THE MORE NORTHERLY TRACK OF THE SYSTEM. HOWEVER THE OVERALL
IMPACTS FROM THIS NEW SYSTEM WILL LIKELY BE SIMILAR TO THE LAST ONE.
ALTHOUGH THERE ARE STILL SOME TIMING DIFFERENCES BETWEEN THE
MODELS...IT NOW APPEARS THAT THIS UPPER LOW WILL BEGIN TO AFFECT OUR
CWA ON THURSDAY...BEGINNING TO COOL TEMPERATURES ACROSS THE
REGION...ESPECIALLY OVER SE CA AND THE LOWER COLORADO RIVER
VALLEY...WHILE ALSO SUBSTANTIALLY INCREASING THE WINDS AS WELL...AS
A 100+ KT JET PUSHES EASTWARD OVER THE REGION AHEAD OF THE MAIN
UPPER LOW...WITH ADVISORY-LEVEL WINDS...AREAS OF BLOWING DUST...AND
EVEN SOME FIRE WEATHER ISSUES A REAL POSSIBILITY. FURTHER
COOLING...AND EVEN A SLIGHT CHANCE FOR SHOWERS IS LIKELY FOR THE
FRIDAY-SUNDAY TIME PERIOD AS THE MAIN UPPER LOW MOVES VERY SLOWLY
EASTWARD ACROSS THE REGION...WITH AT LEAST ONE DAY OF HIGHS IN THE
70S ONCE AGAIN A POSSIBILITY FOR MANY LOWER DESERT LOCATIONS.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
WINDS WILL BE LIGHTER THAN NORMAL AS HIGH PRESSURE BUILDS INTO THE
REGION. OTHERWISE...SKIES WILL BE MAINLY CLEAR THROUGH TUESDAY
MORNING. FEW DIURNAL CU WITH BASES AROUND 9K FT ARE EXPECTED MONDAY...THOUGH
THEY WILL BE MOST CONCENTRATED ACROSS THE HIGHER TERRAIN AND OUTSIDE
OF THE PHOENIX VICINITY.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NO AVIATION WEATHER IMPACTS EXPECTED. WINDS WILL GENERALLY BE LIGHT
AND VARIABLE UNDER MAINLY CLEAR SKIES.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...

HIGH PRESSURE WILL RESULT IN A DRIER AND WARMER AIRMASS OVER THE
DISTRICTS WITH TEMPERATURES ABOVE SEASONAL NORMALS TUESDAY THROUGH
THURSDAY. AN INCOMING WEATHER SYSTEM WILL CAUSE SOUTHERLY WINDS TO
INCREASE WEDNESDAY AND THURSDAY. THERE MAY BE A WINDOW THURSDAY
AFTERNOON OF STRONG WINDS AND LOW HUMIDITIES THAT REACH CRITICAL
FIRE WEATHER CONDITIONS FROM MARICOPA COUNTY AND TO THE EAST.
CONDITIONS WILL IMPROVE FRIDAY AND SATURDAY WHEN THE SYSTEM MOVES IN
ALLOWING TEMPERATURES TO COOL...HUMIDITIES TO COME UP...AND WINDS TO
DECREASE.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED.

&&

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

$$

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

DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...PERCHA
AVIATION...HIRSCH
FIRE WEATHER...INIGUEZ



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