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000
FXUS65 KPSR 200320
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
815 PM MST SAT APR 19 2014

.SYNOPSIS...
HIGH PRESSURE ALOFT WILL BUILD INTO THE AREA SUNDAY INTO EARLY NEXT
WEEK...AND LEAD TO SUNNY DAYS AND CLEAR NIGHTS ALONG WITH SHARPLY
WARMING HIGH TEMPERATURES. BREEZY TO WINDY CONDITIONS ARE EXPECTED
NEXT TUESDAY INTO WEDNESDAY AS A DRY WEATHER SYSTEM PASSES BY TO OUR
NORTH. THE PASSING SYSTEM WILL LEAD TO COOLER WEATHER...WITH HIGH
TEMPERATURES FALLING TO NEAR SEASONAL NORMALS ON WEDNESDAY. HIGHER
PRESSURE WILL RETURN FOR THE LATTER PART OF THE NEXT WORK WEEK...
BRINGING ANOTHER WARMING TREND AND GENERALLY SUNNY SKIES.

&&

.DISCUSSION...
THE PACIFIC LOW PRESSURE SYSTEM CONTINUED TO SLOWLY TRACK EAST
THROUGH CENTRAL AND EASTERN AZ THIS EVENING...AND SHOULD BE IN
CENTRAL NEW MEXICO BY SUNDAY MORNING. UNFORTUNATELY FOR A LARGE PART
OF SOUTHWEST AND SOUTH CENTRAL AZ...INCLUDING PHOENIX...UPPER LEVEL
CONVERGENCE/SUBSIDENCE WITH THE BACKSIDE OF THE TROF MOVED INTO THE
AREA A LITTLE FASTER AND PREVENTED SHWR/TSTM DEVELOPMENT. AS PER
AFTERNOON SATELLITE IMAGERY...MOST UPPER LEVEL STORM SUPPORT WAS
FOCUSED OVER THE SOUTHEAST QUARTER OF AZ...INCLUDING PARTS OF OUR
ZONE 24 SOUTHERN GILA COUNTY.

AS THE LOW PRESSURE SYSTEM CONTINUES TO MOVE EAST THIS EVENING...
ONLY A SLIGHT CHANCE OF SHWRS/TSTMS WILL REMAIN OVER OUR MOUNTAINOUS
SOUTHERN GILA COUNTY ZONE 24 THROUGH MIDNIGHT. OTHERWISE CLEARING
SKIES ARE EXPECTED OVER THE REMAINDER OF THE FORECAST AREA...
SOUTHEAST CA TO SOUTH CENTRAL AZ. FORECASTS WERE UPDATED TO REMOVE
ANY SHWR THREATS THE REMAINDER OF THE EVENING...EXCEPT FOR SOUTHERN
GILA COUNTY ZONE 24. THE SLIGHT CHANCE OF SHOWERS FORECAST FOR A
SMALL PART OF EASTERN SOUTHERN GILA COUNTY ON SUNDAY WAS ALSO
REMOVED AS STRONG SUBSIDENCE WITH THE BUILDING SHORTWAVE RIDGE WILL
PRECLUDE ANY SHOWER POSSIBILITIES.

OTHERWISE CURRENT FORECASTS LOOK OK THROUGH MONDAY. NO FURTHER
UPDATES.


.PORTIONS OF PREVIOUS DISCUSSION...210 PM MST...
UPPER LEVEL PACIFIC LOW CONTINUED TO PUSH EASTWARD ACROSS THE DESERT
SOUTHWEST EARLY THIS AFTERNOON WITH THE MAIN LOW CENTER SHIFTED INTO
FAR SOUTH CENTRAL ARIZONA. MOST OF THE DYNAMICS/Q FORCING HAS
SHIFTED INTO FAR EASTERN OR SOUTHEAST ARIZONA...TO THE SOUTHEAST OF
OUR CWA...AND THE ASSOCIATED CONVECTION HAS SHIFTED SOUTHEAST OF OUR
AREA AS WELL. ONE OF THE MAIN VORT MAXES ROTATING THRU THE BASE OF
THE TROF...AND CLEARLY SEEN IN THE VAPOR IMAGERY...WAS TREKKING
ALONG THE SRN AZ/MEXICAN BORDER EARLY THIS EVENING...AND THE PVA
INDUCED CONVECTION AHEAD OF IT WAS PUSHING THRU FAR SERN AZ...WELL
SOUTHEAST OF THE GREATER PHOENIX AREA.

OTHERWISE...IR IMAGERY INDICATED PARTLY CLOUDY SKIES ACROSS MUCH OF
THE THE CWA...AS THE COLD AIR ALOFT MOVING OVER THE DESERTS HELPED
GENERATE VARIABLE AMOUNTS OF CU.  THE LOW PRESSURE SYSTEM WILL
CONTINUE TO SHIFT EAST ALLOWING FOR DRIER AND MORE SUBSIDENT AIR TO
OVERSPREAD THE LOWER DESERTS. THERE WILL BE A LINGERING SLIGHT
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE HIGHER TERRAIN MAINLY
EAST OF GLOBE UNTIL MIDNIGHT...AND SKIES ACROSS MOST OF THE CWA WILL
BECOME MOSTLY CLEAR.

FOR SUNDAY...TROF AXIS WILL SHIFT INTO NEW MEXICO...AND HIGH
PRESSURE ALOFT WILL BUILD INTO THE DESERTS FROM THE WEST. THERE WILL
BE A BIT OF LINGERING MOISTURE FOR PARTLY CLOUDY SKIES OVER THE
HIGHER TERRAIN EAST OF PHOENIX. OTHERWISE EXPECT MOSTLY SUNNY SKIES
ALONG WITH WARMING HIGH TEMPERATURES. HIGH TEMPS WILL RISE SEVERAL
DEGREES AND INTO THE LOW TO MID 90S ACROSS THE WARMEST LOWER
DESERTS. HIGH PRESSURE ALOFT WILL BUILD FURTHER ON MONDAY...LEADING
TO SOME ADDITIONAL WARMING UNDER GENERALLY SUNNY SKIES.

FOR TUESDAY INTO WEDNESDAY...BOTH THE GFS AND ECMWF CONTINUE TO CALL
FOR A RATHER VIGOROUS PACIFIC UPPER TROF TO MOVE EAST THROUGH THE
DESERT SOUTHWEST...BRINGING CONSIDERABLE WIND TO THE AREA TUESDAY
AFTERNOON AND EVENING...AND LEADING TO SOME CONCERNS REGARDING
POTENTIAL FOR DANGEROUS FIRE WEATHER CONDITIONS. TOO EARLY AT THIS
TIME TO ISSUE A FIRE WEATHER WATCH...BUT THIS MAY BE NEEDED SOMETIME
IN THE NEXT DAY OR SO SHOULD CONFIDENCE IN THE EVENT CONTINUE TO
CLIMB. OTHERWISE THIS WILL BE A TYPICAL APRIL SYSTEM FOR OUR
CWA...BRINGING WIND AND COOLING AND NO PRECIP. IT APPEARS TO BE A
VERY DRY SYSTEM AND SKIES SHOULD BE MOSTLY SUNNY FOR THE MOST PART
BOTH DAYS. DESPITE THE WIND POTENTIAL...THIS TROF WILL LIKELY PASS
TO FAR TO OUR NORTH TO BRING SIGNIFICANT COOLING...AND HIGH TEMPS
ARE FORECAST TO DROP BACK TO NEAR SEASONAL NORMALS ON
WEDNESDAY...WITH THE WARMER DESERTS FALLING INTO THE MID TO UPPER
80S. FLAT UPPER RIDGING...AND DRY WESTERLY FLOW ALOFT...WILL FOLLOW
ON THURSDAY FOR MOSTLY SUNNY SKIES AND A BIT OF WARMING WITH THE
WARMER DESERTS CLIMBING BACK INTO THE LOWER 90S.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 03Z SUN...SCT-BKN CLOUDS AOA 12 THSD AGL. LIGHT AND VARIABLE
WIND UNDER 8 KNOTS. FROM 03Z SUN TO 19Z SUN...FEW CLDS NEAR 16 THSD
MSL. LIGHT AND VRBL WIND UNDER 7 KNOTS.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 19Z SUN...FEW CLDS BASED NEAR 16 THSD AGL. LIGHT SOUTH TO
SOUTHWEST WIND UNDER 7 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
WESTERLY FLOW ALOFT WILL BRING WARM AND DRY CONDITIONS FOR TUESDAY
WITH WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. A COOLING TREND
ENSUES WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO
THE GREAT BASIN AND THE PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH
THIS SYSTEM WILL BE AN INCREASE IN WIND AREA-WIDE TUESDAY INTO
WEDNESDAY...WITH GUSTS UP TO 35 MPH POSSIBLE...AND EVEN STRONGER
GUSTS EXPECTED ACROSS SOUTHEAST CALIFORNIA AND PORTIONS OF THE LOWER
COLORADO RIVER VALLEY. MINIMUM HUMIDITY LEVELS ALSO BOTTOM OUT IN
THE SINGLE DIGITS DURING THIS TIME FRAME OF STRONG
WINDS...PRESENTING AN INCREASED FIRE DANGER THREAT AND THE POSSIBLE
ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS. LIGHT WINDS...WITH DRY
AND WARMER CONDITIONS ARE ON TAP THURSDAY THROUGH SATURDAY AS
HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...VASQUEZ/CB/MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/KUHLMAN




















000
FXUS65 KPSR 200320
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
815 PM MST SAT APR 19 2014

.SYNOPSIS...
HIGH PRESSURE ALOFT WILL BUILD INTO THE AREA SUNDAY INTO EARLY NEXT
WEEK...AND LEAD TO SUNNY DAYS AND CLEAR NIGHTS ALONG WITH SHARPLY
WARMING HIGH TEMPERATURES. BREEZY TO WINDY CONDITIONS ARE EXPECTED
NEXT TUESDAY INTO WEDNESDAY AS A DRY WEATHER SYSTEM PASSES BY TO OUR
NORTH. THE PASSING SYSTEM WILL LEAD TO COOLER WEATHER...WITH HIGH
TEMPERATURES FALLING TO NEAR SEASONAL NORMALS ON WEDNESDAY. HIGHER
PRESSURE WILL RETURN FOR THE LATTER PART OF THE NEXT WORK WEEK...
BRINGING ANOTHER WARMING TREND AND GENERALLY SUNNY SKIES.

&&

.DISCUSSION...
THE PACIFIC LOW PRESSURE SYSTEM CONTINUED TO SLOWLY TRACK EAST
THROUGH CENTRAL AND EASTERN AZ THIS EVENING...AND SHOULD BE IN
CENTRAL NEW MEXICO BY SUNDAY MORNING. UNFORTUNATELY FOR A LARGE PART
OF SOUTHWEST AND SOUTH CENTRAL AZ...INCLUDING PHOENIX...UPPER LEVEL
CONVERGENCE/SUBSIDENCE WITH THE BACKSIDE OF THE TROF MOVED INTO THE
AREA A LITTLE FASTER AND PREVENTED SHWR/TSTM DEVELOPMENT. AS PER
AFTERNOON SATELLITE IMAGERY...MOST UPPER LEVEL STORM SUPPORT WAS
FOCUSED OVER THE SOUTHEAST QUARTER OF AZ...INCLUDING PARTS OF OUR
ZONE 24 SOUTHERN GILA COUNTY.

AS THE LOW PRESSURE SYSTEM CONTINUES TO MOVE EAST THIS EVENING...
ONLY A SLIGHT CHANCE OF SHWRS/TSTMS WILL REMAIN OVER OUR MOUNTAINOUS
SOUTHERN GILA COUNTY ZONE 24 THROUGH MIDNIGHT. OTHERWISE CLEARING
SKIES ARE EXPECTED OVER THE REMAINDER OF THE FORECAST AREA...
SOUTHEAST CA TO SOUTH CENTRAL AZ. FORECASTS WERE UPDATED TO REMOVE
ANY SHWR THREATS THE REMAINDER OF THE EVENING...EXCEPT FOR SOUTHERN
GILA COUNTY ZONE 24. THE SLIGHT CHANCE OF SHOWERS FORECAST FOR A
SMALL PART OF EASTERN SOUTHERN GILA COUNTY ON SUNDAY WAS ALSO
REMOVED AS STRONG SUBSIDENCE WITH THE BUILDING SHORTWAVE RIDGE WILL
PRECLUDE ANY SHOWER POSSIBILITIES.

OTHERWISE CURRENT FORECASTS LOOK OK THROUGH MONDAY. NO FURTHER
UPDATES.


.PORTIONS OF PREVIOUS DISCUSSION...210 PM MST...
UPPER LEVEL PACIFIC LOW CONTINUED TO PUSH EASTWARD ACROSS THE DESERT
SOUTHWEST EARLY THIS AFTERNOON WITH THE MAIN LOW CENTER SHIFTED INTO
FAR SOUTH CENTRAL ARIZONA. MOST OF THE DYNAMICS/Q FORCING HAS
SHIFTED INTO FAR EASTERN OR SOUTHEAST ARIZONA...TO THE SOUTHEAST OF
OUR CWA...AND THE ASSOCIATED CONVECTION HAS SHIFTED SOUTHEAST OF OUR
AREA AS WELL. ONE OF THE MAIN VORT MAXES ROTATING THRU THE BASE OF
THE TROF...AND CLEARLY SEEN IN THE VAPOR IMAGERY...WAS TREKKING
ALONG THE SRN AZ/MEXICAN BORDER EARLY THIS EVENING...AND THE PVA
INDUCED CONVECTION AHEAD OF IT WAS PUSHING THRU FAR SERN AZ...WELL
SOUTHEAST OF THE GREATER PHOENIX AREA.

OTHERWISE...IR IMAGERY INDICATED PARTLY CLOUDY SKIES ACROSS MUCH OF
THE THE CWA...AS THE COLD AIR ALOFT MOVING OVER THE DESERTS HELPED
GENERATE VARIABLE AMOUNTS OF CU.  THE LOW PRESSURE SYSTEM WILL
CONTINUE TO SHIFT EAST ALLOWING FOR DRIER AND MORE SUBSIDENT AIR TO
OVERSPREAD THE LOWER DESERTS. THERE WILL BE A LINGERING SLIGHT
CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE HIGHER TERRAIN MAINLY
EAST OF GLOBE UNTIL MIDNIGHT...AND SKIES ACROSS MOST OF THE CWA WILL
BECOME MOSTLY CLEAR.

FOR SUNDAY...TROF AXIS WILL SHIFT INTO NEW MEXICO...AND HIGH
PRESSURE ALOFT WILL BUILD INTO THE DESERTS FROM THE WEST. THERE WILL
BE A BIT OF LINGERING MOISTURE FOR PARTLY CLOUDY SKIES OVER THE
HIGHER TERRAIN EAST OF PHOENIX. OTHERWISE EXPECT MOSTLY SUNNY SKIES
ALONG WITH WARMING HIGH TEMPERATURES. HIGH TEMPS WILL RISE SEVERAL
DEGREES AND INTO THE LOW TO MID 90S ACROSS THE WARMEST LOWER
DESERTS. HIGH PRESSURE ALOFT WILL BUILD FURTHER ON MONDAY...LEADING
TO SOME ADDITIONAL WARMING UNDER GENERALLY SUNNY SKIES.

FOR TUESDAY INTO WEDNESDAY...BOTH THE GFS AND ECMWF CONTINUE TO CALL
FOR A RATHER VIGOROUS PACIFIC UPPER TROF TO MOVE EAST THROUGH THE
DESERT SOUTHWEST...BRINGING CONSIDERABLE WIND TO THE AREA TUESDAY
AFTERNOON AND EVENING...AND LEADING TO SOME CONCERNS REGARDING
POTENTIAL FOR DANGEROUS FIRE WEATHER CONDITIONS. TOO EARLY AT THIS
TIME TO ISSUE A FIRE WEATHER WATCH...BUT THIS MAY BE NEEDED SOMETIME
IN THE NEXT DAY OR SO SHOULD CONFIDENCE IN THE EVENT CONTINUE TO
CLIMB. OTHERWISE THIS WILL BE A TYPICAL APRIL SYSTEM FOR OUR
CWA...BRINGING WIND AND COOLING AND NO PRECIP. IT APPEARS TO BE A
VERY DRY SYSTEM AND SKIES SHOULD BE MOSTLY SUNNY FOR THE MOST PART
BOTH DAYS. DESPITE THE WIND POTENTIAL...THIS TROF WILL LIKELY PASS
TO FAR TO OUR NORTH TO BRING SIGNIFICANT COOLING...AND HIGH TEMPS
ARE FORECAST TO DROP BACK TO NEAR SEASONAL NORMALS ON
WEDNESDAY...WITH THE WARMER DESERTS FALLING INTO THE MID TO UPPER
80S. FLAT UPPER RIDGING...AND DRY WESTERLY FLOW ALOFT...WILL FOLLOW
ON THURSDAY FOR MOSTLY SUNNY SKIES AND A BIT OF WARMING WITH THE
WARMER DESERTS CLIMBING BACK INTO THE LOWER 90S.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 03Z SUN...SCT-BKN CLOUDS AOA 12 THSD AGL. LIGHT AND VARIABLE
WIND UNDER 8 KNOTS. FROM 03Z SUN TO 19Z SUN...FEW CLDS NEAR 16 THSD
MSL. LIGHT AND VRBL WIND UNDER 7 KNOTS.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 19Z SUN...FEW CLDS BASED NEAR 16 THSD AGL. LIGHT SOUTH TO
SOUTHWEST WIND UNDER 7 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
WESTERLY FLOW ALOFT WILL BRING WARM AND DRY CONDITIONS FOR TUESDAY
WITH WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. A COOLING TREND
ENSUES WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO
THE GREAT BASIN AND THE PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH
THIS SYSTEM WILL BE AN INCREASE IN WIND AREA-WIDE TUESDAY INTO
WEDNESDAY...WITH GUSTS UP TO 35 MPH POSSIBLE...AND EVEN STRONGER
GUSTS EXPECTED ACROSS SOUTHEAST CALIFORNIA AND PORTIONS OF THE LOWER
COLORADO RIVER VALLEY. MINIMUM HUMIDITY LEVELS ALSO BOTTOM OUT IN
THE SINGLE DIGITS DURING THIS TIME FRAME OF STRONG
WINDS...PRESENTING AN INCREASED FIRE DANGER THREAT AND THE POSSIBLE
ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS. LIGHT WINDS...WITH DRY
AND WARMER CONDITIONS ARE ON TAP THURSDAY THROUGH SATURDAY AS
HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...VASQUEZ/CB/MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/KUHLMAN



















000
FXUS65 KPSR 200005
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
505 PM MST SAT APR 19 2014

.UPDATE...AVIATION WEATHER DISCUSSION.

&&

.SYNOPSIS...
A PACIFIC LOW PRESSURE SYSTEM MOVING EAST ACROSS ARIZONA WILL LEAD
TO A LINGERING SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS ACROSS
SOUTH CENTRAL ARIZONA THIS EVENING. HIGH PRESSURE ALOFT WILL BUILD
INTO THE AREA SUNDAY INTO EARLY NEXT WEEK BEHIND THE EXITING
LOW...AND LEAD TO SUNNY DAYS AND CLEAR NIGHTS ALONG WITH SHARPLY
WARMING HIGH TEMPERATURES. BREEZY TO WINDY CONDITIONS ARE EXPECTED
NEXT TUESDAY INTO WEDNESDAY AS A DRY WEATHER SYSTEM PASSES BY TO OUR
NORTH. THE PASSING SYSTEM WILL LEAD TO COOLER WEATHER...WITH HIGH
TEMPERATURES FALLING TO NEAR SEASONAL NORMALS ON WEDNESDAY. HIGHER
PRESSURE WILL RETURN FOR THE LATTER PART OF THE NEXT WORK WEEK...
BRINGING ANOTHER WARMING TREND AND GENERALLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL PACIFIC LOW CONTINUED TO PUSH EASTWARD ACROSS THE DESERT
SOUTHWEST EARLY THIS AFTERNOON WITH THE MAIN LOW CENTER SHIFTED INTO
FAR SOUTH CENTRAL ARIZONA. MOST OF THE DYNAMICS/Q FORCING HAS
SHIFTED INTO FAR EASTERN OR SOUTHEAST ARIZONA...TO THE SOUTHEAST OF
OUR CWA...AND THE ASSOCIATED CONVECTION HAS SHIFTED SOUTHEAST OF OUR
AREA AS WELL. ONE OF THE MAIN VORT MAXES ROTATING THRU THE BASE OF
THE TROF...AND CLEARLY SEEN IN THE VAPOR IMAGERY...WAS TREKKING
ALONG THE SRN AZ/MEXICAN BORDER EARLY THIS EVENING...AND THE PVA
INDUCED CONVECTION AHEAD OF IT WAS PUSHING THRU FAR SERN AZ...WELL
SOUTHEAST OF THE GREATER PHOENIX AREA.

OTHERWISE...IR IMAGERY INDICATED PARTLY CLOUDY SKIES ACROSS MUCH OF
THE THE CWA...AS THE COLD AIR ALOFT MOVING OVER THE DESERTS HELPED
GENERATE VARIABLE AMOUNTS OF CU ALONG WITH A FEW INSTABILITY
SHOWERS. MADE A ZONE UPDATE FOR THIS AFTERNOON TO INCLUDE SLIGHT
CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHWEST DESERTS OF
ARIZONA...BASED ON INCREASING ECHO ON RADAR AS WELL AS INCREASING
AND THICKENING INSTABILITY CUMULUS. FOR LATER THIS AFTERNOON AND
INTO THE EVENING HOURS...THE LOW WILL CONTINUE TO SHIFT EAST
ALLOWING DRIER AND MORE SUBSIDENT AIR TO OVERSPREAD THE LOWER
DESERTS. THERE WILL BE A LINGERING SLIGHT CHANCE OF SHOWERS OR
THUNDERSTORMS FROM THE GREATER PHOENIX AREA EASTWARD...WITH THE BEST
THREAT FOR ANY CONVECTION OVER HIGHER TERRAIN AREAS WELL TO THE EAST
OF PHOENIX...AND MAINLY EAST OF GLOBE. BY MIDNIGHT EXPECT MOST OF
THE CONVECTION TO HAVE ENDED...AND SKIES ACROSS MOST OF THE CWA TO
BECOME MOSTLY CLEAR.

FOR SUNDAY...TROF AXIS WILL SHIFT INTO NEW MEXICO...AND HIGH
PRESSURE ALOFT WILL BUILD INTO THE DESERTS FROM THE WEST. THERE WILL
BE A BIT OF LINGERING MOISTURE AND INSTABILITY OVER THE HIGHER
TERRAIN EAST OF PHOENIX...AND AS SUCH WE WILL KEEP AROUND A 10
PERCENT CHANCE OF INSTABILITY STORMS GOING EAST OF GLOBE DURING THE
AFTERNOON HOURS. OTHERWISE EXPECT MOSTLY SUNNY SKIES ALONG WITH
WARMING HIGH TEMPERATURES. HIGH TEMPS WILL RISE SEVERAL DEGREES AND
INTO THE LOW TO MID 90S ACROSS THE WARMEST LOWER DESERTS. HIGH
PRESSURE ALOFT WILL BUILD FURTHER ON MONDAY...LEADING TO SOME
ADDITIONAL WARMING UNDER GENERALLY SUNNY SKIES.

FOR TUESDAY INTO WEDNESDAY...BOTH THE GFS AND ECMWF CONTINUE TO CALL
FOR A RATHER VIGOROUS PACIFIC UPPER TROF TO MOVE EAST THROUGH THE
DESERT SOUTHWEST...BRINGING CONSIDERABLE WIND TO THE AREA TUESDAY
AFTERNOON AND EVENING...AND LEADING TO SOME CONCERNS REGARDING
POTENTIAL FOR DANGEROUS FIRE WEATHER CONDITIONS. TOO EARLY AT THIS
TIME TO ISSUE A FIRE WEATHER WATCH...BUT THIS MAY BE NEEDED SOMETIME
IN THE NEXT DAY OR SO SHOULD CONFIDENCE IN THE EVENT CONTINUE TO
CLIMB. OTHERWISE THIS WILL BE A TYPICAL APRIL SYSTEM FOR OUR
CWA...BRINGING WIND AND COOLING AND NO PRECIP. IT APPEARS TO BE A
VERY DRY SYSTEM AND SKIES SHOULD BE MOSTLY SUNNY FOR THE MOST PART
BOTH DAYS. DESPITE THE WIND POTENTIAL...THIS TROF WILL LIKELY PASS
TO FAR TO OUR NORTH TO BRING SIGNIFICANT COOLING...AND HIGH TEMPS
ARE FORECAST TO DROP BACK TO NEAR SEASONAL NORMALS ON
WEDNESDAY...WITH THE WARMER DESERTS FALLING INTO THE MID TO UPPER
80S. FLAT UPPER RIDGING...AND DRY WESTERLY FLOW ALOFT...WILL FOLLOW
ON THURSDAY FOR MOSTLY SUNNY SKIES AND A BIT OF WARMING WITH THE
WARMER DESERTS CLIMBING BACK INTO THE LOWER 90S.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 03Z SUN...SCT-BKN CLOUDS AOA 12 THSD AGL. LIGHT AND VARIABLE
WIND UNDER 8 KNOTS. FROM 03Z SUN TO 19Z SUN...FEW CLDS NEAR 16 THSD
MSL. LIGHT AND VRBL WIND UNDER 7 KNOTS.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 19Z SUN...FEW CLDS BASED NEAR 16 THSD AGL. LIGHT SOUTH TO
SOUTHWEST WIND UNDER 7 KNOTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
WESTERLY FLOW ALOFT WILL BRING WARM AND DRY CONDITIONS FOR TUESDAY
WITH WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. A COOLING TREND
ENSUES WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO
THE GREAT BASIN AND THE PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH
THIS SYSTEM WILL BE AN INCREASE IN WIND AREA-WIDE TUESDAY INTO
WEDNESDAY...WITH GUSTS UP TO 35 MPH POSSIBLE...AND EVEN STRONGER
GUSTS EXPECTED ACROSS SOUTHEAST CALIFORNIA AND PORTIONS OF THE LOWER
COLORADO RIVER VALLEY. MINIMUM HUMIDITY LEVELS ALSO BOTTOM OUT IN
THE SINGLE DIGITS DURING THIS TIME FRAME OF STRONG
WINDS...PRESENTING AN INCREASED FIRE DANGER THREAT AND THE POSSIBLE
ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS. LIGHT WINDS...WITH DRY
AND WARMER CONDITIONS ARE ON TAP THURSDAY THROUGH SATURDAY AS
HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB/MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/KUHLMAN

















000
FXUS65 KPSR 192111
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
210 PM MST SAT APR 19 2014

.SYNOPSIS...
A PACIFIC LOW PRESSURE SYSTEM MOVING EAST ACROSS ARIZONA WILL LEAD
TO A LINGERING SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS ACROSS
SOUTH CENTRAL ARIZONA THIS EVENING. HIGH PRESSURE ALOFT WILL BUILD
INTO THE AREA SUNDAY INTO EARLY NEXT WEEK BEHIND THE EXITING
LOW...AND LEAD TO SUNNY DAYS AND CLEAR NIGHTS ALONG WITH SHARPLY
WARMING HIGH TEMPERATURES. BREEZY TO WINDY CONDITIONS ARE EXPECTED
NEXT TUESDAY INTO WEDNESDAY AS A DRY WEATHER SYSTEM PASSES BY TO OUR
NORTH. THE PASSING SYSTEM WILL LEAD TO COOLER WEATHER...WITH HIGH
TEMPERATURES FALLING TO NEAR SEASONAL NORMALS ON WEDNESDAY. HIGHER
PRESSURE WILL RETURN FOR THE LATTER PART OF THE NEXT WORK WEEK...
BRINGING ANOTHER WARMING TREND AND GENERALLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL PACIFIC LOW CONTINUED TO PUSH EASTWARD ACROSS THE DESERT
SOUTHWEST EARLY THIS AFTERNOON WITH THE MAIN LOW CENTER SHIFTED INTO
FAR SOUTH CENTRAL ARIZONA. MOST OF THE DYNAMICS/Q FORCING HAS
SHIFTED INTO FAR EASTERN OR SOUTHEAST ARIZONA...TO THE SOUTHEAST OF
OUR CWA...AND THE ASSOCIATED CONVECTION HAS SHIFTED SOUTHEAST OF OUR
AREA AS WELL. ONE OF THE MAIN VORT MAXES ROTATING THRU THE BASE OF
THE TROF...AND CLEARLY SEEN IN THE VAPOR IMAGERY...WAS TREKKING
ALONG THE SRN AZ/MEXICAN BORDER EARLY THIS EVENING...AND THE PVA
INDUCED CONVECTION AHEAD OF IT WAS PUSHING THRU FAR SERN AZ...WELL
SOUTHEAST OF THE GREATER PHOENIX AREA.

OTHERWISE...IR IMAGERY INDICATED PARTLY CLOUDY SKIES ACROSS MUCH OF
THE THE CWA...AS THE COLD AIR ALOFT MOVING OVER THE DESERTS HELPED
GENERATE VARIABLE AMOUNTS OF CU ALONG WITH A FEW INSTABILITY
SHOWERS. MADE A ZONE UPDATE FOR THIS AFTERNOON TO INCLUDE SLIGHT
CHANCES OF SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHWEST DESERTS OF
ARIZONA...BASED ON INCREASING ECHO ON RADAR AS WELL AS INCREASING
AND THICKENING INSTABILITY CUMULUS. FOR LATER THIS AFTERNOON AND
INTO THE EVENING HOURS...THE LOW WILL CONTINUE TO SHIFT EAST
ALLOWING DRIER AND MORE SUBSIDENT AIR TO OVERSPREAD THE LOWER
DESERTS. THERE WILL BE A LINGERING SLIGHT CHANCE OF SHOWERS OR
THUNDERSTORMS FROM THE GREATER PHOENIX AREA EASTWARD...WITH THE BEST
THREAT FOR ANY CONVECTION OVER HIGHER TERRAIN AREAS WELL TO THE EAST
OF PHOENIX...AND MAINLY EAST OF GLOBE. BY MIDNIGHT EXPECT MOST OF
THE CONVECTION TO HAVE ENDED...AND SKIES ACROSS MOST OF THE CWA TO
BECOME MOSTLY CLEAR.

FOR SUNDAY...TROF AXIS WILL SHIFT INTO NEW MEXICO...AND HIGH
PRESSURE ALOFT WILL BUILD INTO THE DESERTS FROM THE WEST. THERE WILL
BE A BIT OF LINGERING MOISTURE AND INSTABILITY OVER THE HIGHER
TERRAIN EAST OF PHOENIX...AND AS SUCH WE WILL KEEP AROUND A 10
PERCENT CHANCE OF INSTABILITY STORMS GOING EAST OF GLOBE DURING THE
AFTERNOON HOURS. OTHERWISE EXPECT MOSTLY SUNNY SKIES ALONG WITH
WARMING HIGH TEMPERATURES. HIGH TEMPS WILL RISE SEVERAL DEGREES AND
INTO THE LOW TO MID 90S ACROSS THE WARMEST LOWER DESERTS. HIGH
PRESSURE ALOFT WILL BUILD FURTHER ON MONDAY...LEADING TO SOME
ADDITIONAL WARMING UNDER GENERALLY SUNNY SKIES.

FOR TUESDAY INTO WEDNESDAY...BOTH THE GFS AND ECMWF CONTINUE TO CALL
FOR A RATHER VIGOROUS PACIFIC UPPER TROF TO MOVE EAST THROUGH THE
DESERT SOUTHWEST...BRINGING CONSIDERABLE WIND TO THE AREA TUESDAY
AFTERNOON AND EVENING...AND LEADING TO SOME CONCERNS REGARDING
POTENTIAL FOR DANGEROUS FIRE WEATHER CONDITIONS. TOO EARLY AT THIS
TIME TO ISSUE A FIRE WEATHER WATCH...BUT THIS MAY BE NEEDED SOMETIME
IN THE NEXT DAY OR SO SHOULD CONFIDENCE IN THE EVENT CONTINUE TO
CLIMB. OTHERWISE THIS WILL BE A TYPICAL APRIL SYSTEM FOR OUR
CWA...BRINGING WIND AND COOLING AND NO PRECIP. IT APPEARS TO BE A
VERY DRY SYSTEM AND SKIES SHOULD BE MOSTLY SUNNY FOR THE MOST PART
BOTH DAYS. DESPITE THE WIND POTENTIAL...THIS TROF WILL LIKELY PASS
TO FAR TO OUR NORTH TO BRING SIGNIFICANT COOLING...AND HIGH TEMPS
ARE FORECAST TO DROP BACK TO NEAR SEASONAL NORMALS ON
WEDNESDAY...WITH THE WARMER DESERTS FALLING INTO THE MID TO UPPER
80S. FLAT UPPER RIDGING...AND DRY WESTERLY FLOW ALOFT...WILL FOLLOW
ON THURSDAY FOR MOSTLY SUNNY SKIES AND A BIT OF WARMING WITH THE
WARMER DESERTS CLIMBING BACK INTO THE LOWER 90S.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND SCATTERED CLOUD DECKS GENERALLY AOA 10KFT
WITH ISOLATED SHOWERS/THUNDERSTORMS THIS AFTERNOON MAINLY EAST OF
KPHX-KIWA-KSDL. THERE IS STILL THE POSSIBILITY OF STRONG GUSTY
ERRATIC WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE
AND CLEAR OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND FEW TO SCATTERED CLOUD DECKS AOA 12KFT EXPECTED
THROUGH THIS AFTERNOON. SKIES CLEAR OUT BY EARLY EVENING FOR MOSTLY
CLEAR SKIES THE REMAINDER OF THE TAF PERIOD.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
WESTERLY FLOW ALOFT WILL BRING WARM AND DRY CONDITIONS FOR TUESDAY
WITH WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. A COOLING TREND
ENSUES WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO
THE GREAT BASIN AND THE PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH
THIS SYSTEM WILL BE AN INCREASE IN WIND AREA-WIDE TUESDAY INTO
WEDNESDAY...WITH GUSTS UP TO 35 MPH POSSIBLE...AND EVEN STRONGER
GUSTS EXPECTED ACROSS SOUTHEAST CALIFORNIA AND PORTIONS OF THE LOWER
COLORADO RIVER VALLEY. MINIMUM HUMIDITY LEVELS ALSO BOTTOM OUT IN
THE SINGLE DIGITS DURING THIS TIME FRAME OF STRONG
WINDS...PRESENTING AN INCREASED FIRE DANGER THREAT AND THE POSSIBLE
ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS. LIGHT WINDS...WITH DRY
AND WARMER CONDITIONS ARE ON TAP THURSDAY THROUGH SATURDAY AS
HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB/MO
AVIATION...MEYERS/KUHLMAN
FIRE WEATHER...MEYERS/KUHLMAN













000
FXUS65 KPSR 192005
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
105 PM MST SAT APR 19 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS...

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
UPPER LEVEL PACIFIC LOW PRESSURE SYSTEM CONTINUED TO TREK STEADILY
EASTWARD ACROSS THE DESERT SOUTHWEST THIS MORNING...WITH THE LOW
CENTER MOVING ACROSS SOUTHWEST/SOUTHCENTRAL AZ AT 5 AM. SYSTEM IS
MODERATELY UNSTABLE...WITH H5 CORE TEMPS NEAR MINUS 18C...AND TUS
SOUNDING AT 12Z INDICATED A LIFTED INDEX NEARLY MINUS 5. TUS RAOB
ALSO SHOWED AN INVERTED VEE CHARACTER TO THE SOUNDING...WITH DRY AIR
REMAINING IN THE LOWER LAYERS...AND AS SUCH MIXED LAYER CAPE IS
RATHER LOW...MOSTLY BELOW 250 J/KG. VAPOR IMAGERY AT 8 AM INDICATED
THE PRESENCE OF A DISTINCT VORT MAX TREKKING ACROSS FAR NRN GULF OF
CA...AND INTO SERN AZ...AND IN THE PVA AREA AHEAD OF THE VORT MAX AN
AREA OF SHOWERS ALONG WITH ISOLD THUNDERSTORMS HAD DEVELOPED. THIS
AREA OF CONVECTION WILL LIFT TO THE NORTHEAST BUT SHOULD MOSTLY
REMAIN TO THE SOUTH AND EAST OF OUR CWA FOR THE REST OF TODAY. SREF
PROBABILITIES OF CAPE...WHETHER IT IS MOST UNSTABLE...SURFACE BASED
OR MIXED LAYER...SUGGEST BEST THREAT FOR SIGNIFICANT CONVECTION WILL
STAY SOUTH AND EAST OF OUR CWA...AND SOUTHEAST OF THE GREATER
PHOENIX AREA...DURING THE DAY TODAY. HOWEVER...THERE IS ALSO THE
THREAT FOR ISOLATED TO SCATTERED INSTABILITY SHOWERS OR EVEN
THUNDERSTORMS ACROSS THE CENTRAL DESERTS TODAY AS THE COLD CORE
ALOFT MOVES OVERHEAD. POP FORECASTS THAT WERE ALREADY IN PLACE
LOOKED GOOD...HOWEVER WE RAISED POPS SLIGHTLY ALONG THE BORDER WITH
TUCSON INTO THE 30-40 PERCENT BALLPARK TO BETTER BLEND WITH THEIR
FORECASTS...AND TO ACCOUNT FOR THE POSSIBILITY OF CONVECTION
ASSOCIATED WITH THE VORT MAX LIFTING NEWD AND INTO THE CENTRAL
DESERTS.

FOR THE REST OF TODAY...CHANCES FOR SHOWERS OR CONVECTION WEST OF
MARICOPA COUNTY LOOK RATHER SLIM...AS DRIER AND MORE SUBSIDENT AIR
WORK IN ON THE BACK SIDE OF THE PACIFIC LOW. CHANCES FOR SHOWERS
ACROSS THE GREATER PHOENIX AREA TODAY WILL STAY IN THE 20-30 PERCENT
BALLPARK...AND WE CANNOT RULE OUT AN ISOLATED THUNDERSTORM AT SOME
POINT. OTHERWISE...EXPECT PARTLY TO MOSTLY CLOUDY SKIES
TODAY...ALONG WITH HIGH TEMPERATURES NEAR SEASONAL NORMALS.

.PREVIOUS DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND SCATTERED CLOUD DECKS GENERALLY AOA 10KFT
WITH ISOLATED SHOWERS/THUNDERSTORMS THIS AFTERNOON MAINLY EAST OF
KPHX-KIWA-KSDL. THERE IS STILL THE POSSIBILITY OF STRONG GUSTY
ERRATIC WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE
AND CLEAR OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND FEW TO SCATTERED CLOUD DECKS AOA 12KFT EXPECTED
THROUGH THIS AFTERNOON. SKIES CLEAR OUT BY EARLY EVENING FOR MOSTLY
CLEAR SKIES THE REMAINDER OF THE TAF PERIOD.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
WESTERLY FLOW ALOFT WILL BRING WARM AND DRY CONDITIONS FOR TUESDAY
WITH WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. A COOLING TREND
ENSUES WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO
THE GREAT BASIN AND THE PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH
THIS SYSTEM WILL BE AN INCREASE IN WIND AREA-WIDE TUESDAY INTO
WEDNESDAY...WITH GUSTS UP TO 35 MPH POSSIBLE...AND EVEN STRONGER
GUSTS EXPECTED ACROSS SOUTHEAST CALIFORNIA AND PORTIONS OF THE LOWER
COLORADO RIVER VALLEY. MINIMUM HUMIDITY LEVELS ALSO BOTTOM OUT IN
THE SINGLE DIGITS DURING THIS TIME FRAME OF STRONG
WINDS...PRESENTING AN INCREASED FIRE DANGER THREAT AND THE POSSIBLE
ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS. LIGHT WINDS...WITH DRY
AND WARMER CONDITIONS ARE ON TAP THURSDAY THROUGH SATURDAY AS
HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS/KUHLMAN
FIRE WEATHER...MEYERS/KUHLMAN










000
FXUS65 KPSR 192005
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
105 PM MST SAT APR 19 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS...

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
UPPER LEVEL PACIFIC LOW PRESSURE SYSTEM CONTINUED TO TREK STEADILY
EASTWARD ACROSS THE DESERT SOUTHWEST THIS MORNING...WITH THE LOW
CENTER MOVING ACROSS SOUTHWEST/SOUTHCENTRAL AZ AT 5 AM. SYSTEM IS
MODERATELY UNSTABLE...WITH H5 CORE TEMPS NEAR MINUS 18C...AND TUS
SOUNDING AT 12Z INDICATED A LIFTED INDEX NEARLY MINUS 5. TUS RAOB
ALSO SHOWED AN INVERTED VEE CHARACTER TO THE SOUNDING...WITH DRY AIR
REMAINING IN THE LOWER LAYERS...AND AS SUCH MIXED LAYER CAPE IS
RATHER LOW...MOSTLY BELOW 250 J/KG. VAPOR IMAGERY AT 8 AM INDICATED
THE PRESENCE OF A DISTINCT VORT MAX TREKKING ACROSS FAR NRN GULF OF
CA...AND INTO SERN AZ...AND IN THE PVA AREA AHEAD OF THE VORT MAX AN
AREA OF SHOWERS ALONG WITH ISOLD THUNDERSTORMS HAD DEVELOPED. THIS
AREA OF CONVECTION WILL LIFT TO THE NORTHEAST BUT SHOULD MOSTLY
REMAIN TO THE SOUTH AND EAST OF OUR CWA FOR THE REST OF TODAY. SREF
PROBABILITIES OF CAPE...WHETHER IT IS MOST UNSTABLE...SURFACE BASED
OR MIXED LAYER...SUGGEST BEST THREAT FOR SIGNIFICANT CONVECTION WILL
STAY SOUTH AND EAST OF OUR CWA...AND SOUTHEAST OF THE GREATER
PHOENIX AREA...DURING THE DAY TODAY. HOWEVER...THERE IS ALSO THE
THREAT FOR ISOLATED TO SCATTERED INSTABILITY SHOWERS OR EVEN
THUNDERSTORMS ACROSS THE CENTRAL DESERTS TODAY AS THE COLD CORE
ALOFT MOVES OVERHEAD. POP FORECASTS THAT WERE ALREADY IN PLACE
LOOKED GOOD...HOWEVER WE RAISED POPS SLIGHTLY ALONG THE BORDER WITH
TUCSON INTO THE 30-40 PERCENT BALLPARK TO BETTER BLEND WITH THEIR
FORECASTS...AND TO ACCOUNT FOR THE POSSIBILITY OF CONVECTION
ASSOCIATED WITH THE VORT MAX LIFTING NEWD AND INTO THE CENTRAL
DESERTS.

FOR THE REST OF TODAY...CHANCES FOR SHOWERS OR CONVECTION WEST OF
MARICOPA COUNTY LOOK RATHER SLIM...AS DRIER AND MORE SUBSIDENT AIR
WORK IN ON THE BACK SIDE OF THE PACIFIC LOW. CHANCES FOR SHOWERS
ACROSS THE GREATER PHOENIX AREA TODAY WILL STAY IN THE 20-30 PERCENT
BALLPARK...AND WE CANNOT RULE OUT AN ISOLATED THUNDERSTORM AT SOME
POINT. OTHERWISE...EXPECT PARTLY TO MOSTLY CLOUDY SKIES
TODAY...ALONG WITH HIGH TEMPERATURES NEAR SEASONAL NORMALS.

.PREVIOUS DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND SCATTERED CLOUD DECKS GENERALLY AOA 10KFT
WITH ISOLATED SHOWERS/THUNDERSTORMS THIS AFTERNOON MAINLY EAST OF
KPHX-KIWA-KSDL. THERE IS STILL THE POSSIBILITY OF STRONG GUSTY
ERRATIC WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE
AND CLEAR OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND FEW TO SCATTERED CLOUD DECKS AOA 12KFT EXPECTED
THROUGH THIS AFTERNOON. SKIES CLEAR OUT BY EARLY EVENING FOR MOSTLY
CLEAR SKIES THE REMAINDER OF THE TAF PERIOD.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
TUESDAY THROUGH SATURDAY...
WESTERLY FLOW ALOFT WILL BRING WARM AND DRY CONDITIONS FOR TUESDAY
WITH WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES. A COOLING TREND
ENSUES WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO
THE GREAT BASIN AND THE PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH
THIS SYSTEM WILL BE AN INCREASE IN WIND AREA-WIDE TUESDAY INTO
WEDNESDAY...WITH GUSTS UP TO 35 MPH POSSIBLE...AND EVEN STRONGER
GUSTS EXPECTED ACROSS SOUTHEAST CALIFORNIA AND PORTIONS OF THE LOWER
COLORADO RIVER VALLEY. MINIMUM HUMIDITY LEVELS ALSO BOTTOM OUT IN
THE SINGLE DIGITS DURING THIS TIME FRAME OF STRONG
WINDS...PRESENTING AN INCREASED FIRE DANGER THREAT AND THE POSSIBLE
ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS. LIGHT WINDS...WITH DRY
AND WARMER CONDITIONS ARE ON TAP THURSDAY THROUGH SATURDAY AS
HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS/KUHLMAN
FIRE WEATHER...MEYERS/KUHLMAN











000
FXUS65 KPSR 191616
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
915 AM MST SAT APR 19 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
UPPER LEVEL PACIFIC LOW PRESSURE SYSTEM CONTINUED TO TREK STEADILY
EASTWARD ACROSS THE DESERT SOUTHWEST THIS MORNING...WITH THE LOW
CENTER MOVING ACROSS SOUTHWEST/SOUTHCENTRAL AZ AT 5 AM. SYSTEM IS
MODERATELY UNSTABLE...WITH H5 CORE TEMPS NEAR MINUS 18C...AND TUS
SOUNDING AT 12Z INDICATED A LIFTED INDEX NEARLY MINUS 5. TUS RAOB
ALSO SHOWED AN INVERTED VEE CHARACTER TO THE SOUNDING...WITH DRY AIR
REMAINING IN THE LOWER LAYERS...AND AS SUCH MIXED LAYER CAPE IS
RATHER LOW...MOSTLY BELOW 250 J/KG. VAPOR IMAGERY AT 8 AM INDICATED
THE PRESENCE OF A DISTINCT VORT MAX TREKKING ACROSS FAR NRN GULF OF
CA...AND INTO SERN AZ...AND IN THE PVA AREA AHEAD OF THE VORT MAX AN
AREA OF SHOWERS ALONG WITH ISOLD THUNDERSTORMS HAD DEVELOPED. THIS
AREA OF CONVECTION WILL LIFT TO THE NORTHEAST BUT SHOULD MOSTLY
REMAIN TO THE SOUTH AND EAST OF OUR CWA FOR THE REST OF TODAY. SREF
PROBABILITIES OF CAPE...WHETHER IT IS MOST UNSTABLE...SURFACE BASED
OR MIXED LAYER...SUGGEST BEST THREAT FOR SIGNIFICANT CONVECTION WILL
STAY SOUTH AND EAST OF OUR CWA...AND SOUTHEAST OF THE GREATER
PHOENIX AREA...DURING THE DAY TODAY. HOWEVER...THERE IS ALSO THE
THREAT FOR ISOLATED TO SCATTERED INSTABILITY SHOWERS OR EVEN
THUNDERSTORMS ACROSS THE CENTRAL DESERTS TODAY AS THE COLD CORE
ALOFT MOVES OVERHEAD. POP FORECASTS THAT WERE ALREADY IN PLACE
LOOKED GOOD...HOWEVER WE RAISED POPS SLIGHTLY ALONG THE BORDER WITH
TUCSON INTO THE 30-40 PERCENT BALLPARK TO BETTER BLEND WITH THEIR
FORECASTS...AND TO ACCOUNT FOR THE POSSIBILITY OF CONVECTION
ASSOCIATED WITH THE VORT MAX LIFTING NEWD AND INTO THE CENTRAL
DESERTS.

FOR THE REST OF TODAY...CHANCES FOR SHOWERS OR CONVECTION WEST OF
MARICOPA COUNTY LOOK RATHER SLIM...AS DRIER AND MORE SUBSIDENT AIR
WORK IN ON THE BACK SIDE OF THE PACIFIC LOW. CHANCES FOR SHOWERS
ACROSS THE GREATER PHOENIX AREA TODAY WILL STAY IN THE 20-30 PERCENT
BALLPARK...AND WE CANNOT RULE OUT AN ISOLATED THUNDERSTORM AT SOME
POINT. OTHERWISE...EXPECT PARTLY TO MOSTLY CLOUDY SKIES
TODAY...ALONG WITH HIGH TEMPERATURES NEAR SEASONAL NORMALS.

.PREVIOUS DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND BROKEN CLOUD DECKS GENERALLY AOA 10KFT WITH
ISOLATED SHOWERS/THUNDERSTORMS THIS MORNING NEAR KPHX-KIWA-KSDL...
ACTIVITY PERSISTING INTO THE AFTERNOON HOURS. STRONG GUSTY ERRATIC
WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE AND CLEAR
OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND SCATTERED TO BROKEN CLOUD DECKS AOA 12KFT EXPECTED
THROUGH 18Z. SKIES CLEAR OUT BY EARLY AFTERNOON FOR MOSTLY CLEAR
SKIES THE REMAINDER OF THE TAF PERIOD INTO SUNDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED THROUGH TUESDAY. A COOLING TREND ENSUES WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND THE
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE TUESDAY INTO WEDNESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...AND EVEN STRONGER GUSTS EXPECTED ACROSS SOUTHEAST
CALIFORNIA AND PORTIONS OF THE LOWER COLORADO RIVER VALLEY. MINIMUM
HUMIDITY LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS DURING THIS
TIME FRAME OF STRONG WINDS...PRESENTING AN INCREASED FIRE DANGER
THREAT AND THE POSSIBLE ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS.
LIGHT WINDS...WITH DRY AND WARMER CONDITIONS ARE ON TAP THURSDAY AND
FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS/CB








000
FXUS65 KPSR 191616
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
915 AM MST SAT APR 19 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
UPPER LEVEL PACIFIC LOW PRESSURE SYSTEM CONTINUED TO TREK STEADILY
EASTWARD ACROSS THE DESERT SOUTHWEST THIS MORNING...WITH THE LOW
CENTER MOVING ACROSS SOUTHWEST/SOUTHCENTRAL AZ AT 5 AM. SYSTEM IS
MODERATELY UNSTABLE...WITH H5 CORE TEMPS NEAR MINUS 18C...AND TUS
SOUNDING AT 12Z INDICATED A LIFTED INDEX NEARLY MINUS 5. TUS RAOB
ALSO SHOWED AN INVERTED VEE CHARACTER TO THE SOUNDING...WITH DRY AIR
REMAINING IN THE LOWER LAYERS...AND AS SUCH MIXED LAYER CAPE IS
RATHER LOW...MOSTLY BELOW 250 J/KG. VAPOR IMAGERY AT 8 AM INDICATED
THE PRESENCE OF A DISTINCT VORT MAX TREKKING ACROSS FAR NRN GULF OF
CA...AND INTO SERN AZ...AND IN THE PVA AREA AHEAD OF THE VORT MAX AN
AREA OF SHOWERS ALONG WITH ISOLD THUNDERSTORMS HAD DEVELOPED. THIS
AREA OF CONVECTION WILL LIFT TO THE NORTHEAST BUT SHOULD MOSTLY
REMAIN TO THE SOUTH AND EAST OF OUR CWA FOR THE REST OF TODAY. SREF
PROBABILITIES OF CAPE...WHETHER IT IS MOST UNSTABLE...SURFACE BASED
OR MIXED LAYER...SUGGEST BEST THREAT FOR SIGNIFICANT CONVECTION WILL
STAY SOUTH AND EAST OF OUR CWA...AND SOUTHEAST OF THE GREATER
PHOENIX AREA...DURING THE DAY TODAY. HOWEVER...THERE IS ALSO THE
THREAT FOR ISOLATED TO SCATTERED INSTABILITY SHOWERS OR EVEN
THUNDERSTORMS ACROSS THE CENTRAL DESERTS TODAY AS THE COLD CORE
ALOFT MOVES OVERHEAD. POP FORECASTS THAT WERE ALREADY IN PLACE
LOOKED GOOD...HOWEVER WE RAISED POPS SLIGHTLY ALONG THE BORDER WITH
TUCSON INTO THE 30-40 PERCENT BALLPARK TO BETTER BLEND WITH THEIR
FORECASTS...AND TO ACCOUNT FOR THE POSSIBILITY OF CONVECTION
ASSOCIATED WITH THE VORT MAX LIFTING NEWD AND INTO THE CENTRAL
DESERTS.

FOR THE REST OF TODAY...CHANCES FOR SHOWERS OR CONVECTION WEST OF
MARICOPA COUNTY LOOK RATHER SLIM...AS DRIER AND MORE SUBSIDENT AIR
WORK IN ON THE BACK SIDE OF THE PACIFIC LOW. CHANCES FOR SHOWERS
ACROSS THE GREATER PHOENIX AREA TODAY WILL STAY IN THE 20-30 PERCENT
BALLPARK...AND WE CANNOT RULE OUT AN ISOLATED THUNDERSTORM AT SOME
POINT. OTHERWISE...EXPECT PARTLY TO MOSTLY CLOUDY SKIES
TODAY...ALONG WITH HIGH TEMPERATURES NEAR SEASONAL NORMALS.

.PREVIOUS DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND BROKEN CLOUD DECKS GENERALLY AOA 10KFT WITH
ISOLATED SHOWERS/THUNDERSTORMS THIS MORNING NEAR KPHX-KIWA-KSDL...
ACTIVITY PERSISTING INTO THE AFTERNOON HOURS. STRONG GUSTY ERRATIC
WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE AND CLEAR
OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND SCATTERED TO BROKEN CLOUD DECKS AOA 12KFT EXPECTED
THROUGH 18Z. SKIES CLEAR OUT BY EARLY AFTERNOON FOR MOSTLY CLEAR
SKIES THE REMAINDER OF THE TAF PERIOD INTO SUNDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED THROUGH TUESDAY. A COOLING TREND ENSUES WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND THE
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE TUESDAY INTO WEDNESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...AND EVEN STRONGER GUSTS EXPECTED ACROSS SOUTHEAST
CALIFORNIA AND PORTIONS OF THE LOWER COLORADO RIVER VALLEY. MINIMUM
HUMIDITY LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS DURING THIS
TIME FRAME OF STRONG WINDS...PRESENTING AN INCREASED FIRE DANGER
THREAT AND THE POSSIBLE ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS.
LIGHT WINDS...WITH DRY AND WARMER CONDITIONS ARE ON TAP THURSDAY AND
FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...CB
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS/CB







000
FXUS65 KPSR 191241 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
541 AM MST SAT APR 19 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND BROKEN CLOUD DECKS GENERALLY AOA 10KFT WITH
ISOLATED SHOWERS/THUNDERSTORMS THIS MORNING NEAR KPHX-KIWA-KSDL...
ACTIVITY PERSISTING INTO THE AFTERNOON HOURS. STRONG GUSTY ERRATIC
WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE AND CLEAR
OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND SCATTERED TO BROKEN CLOUD DECKS AOA 12KFT EXPECTED
THROUGH 18Z. SKIES CLEAR OUT BY EARLY AFTERNOON FOR MOSTLY CLEAR
SKIES THE REMAINDER OF THE TAF PERIOD INTO SUNDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED THROUGH TUESDAY. A COOLING TREND ENSUES WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND THE
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE TUESDAY INTO WEDNESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...AND EVEN STRONGER GUSTS EXPECTED ACROSS SOUTHEAST
CALIFORNIA AND PORTIONS OF THE LOWER COLORADO RIVER VALLEY. MINIMUM
HUMIDITY LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS DURING THIS
TIME FRAME OF STRONG WINDS...PRESENTING AN INCREASED FIRE DANGER
THREAT AND THE POSSIBLE ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS.
LIGHT WINDS...WITH DRY AND WARMER CONDITIONS ARE ON TAP THURSDAY AND
FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS/CB







000
FXUS65 KPSR 191241 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
541 AM MST SAT APR 19 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS.

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A LOW PRESSURE SYSTEM WILL TRACK EAST ACROSS CENTRAL AZ THIS PERIOD.
EXPECT LIGHT WINDS AND BROKEN CLOUD DECKS GENERALLY AOA 10KFT WITH
ISOLATED SHOWERS/THUNDERSTORMS THIS MORNING NEAR KPHX-KIWA-KSDL...
ACTIVITY PERSISTING INTO THE AFTERNOON HOURS. STRONG GUSTY ERRATIC
WINDS POSSIBLE NEAR VIRGA SHAFTS AND STORMS. SKIES IMPROVE AND CLEAR
OUT LATER THIS EVENING AFTER 03Z AS LOW MOVES EAST.

SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
LIGHT WINDS AND SCATTERED TO BROKEN CLOUD DECKS AOA 12KFT EXPECTED
THROUGH 18Z. SKIES CLEAR OUT BY EARLY AFTERNOON FOR MOSTLY CLEAR
SKIES THE REMAINDER OF THE TAF PERIOD INTO SUNDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED THROUGH TUESDAY. A COOLING TREND ENSUES WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND THE
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE TUESDAY INTO WEDNESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...AND EVEN STRONGER GUSTS EXPECTED ACROSS SOUTHEAST
CALIFORNIA AND PORTIONS OF THE LOWER COLORADO RIVER VALLEY. MINIMUM
HUMIDITY LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS DURING THIS
TIME FRAME OF STRONG WINDS...PRESENTING AN INCREASED FIRE DANGER
THREAT AND THE POSSIBLE ISSUANCE OF RED FLAG WARNINGS IN SOME AREAS.
LIGHT WINDS...WITH DRY AND WARMER CONDITIONS ARE ON TAP THURSDAY AND
FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS/CB






000
FXUS65 KPSR 190942
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
240 AM MST SAT APR 19 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 17Z SAT...BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT SHOWER.
LIGHT EAST WIND UNDER 9 KNOTS. FROM 17Z SAT TO 23Z SAT...A PACIFIC
LOW PRESSURE SYSTEM WILL TRACK ACROSS CENTRAL AZ THIS PERIOD. A
CHANCE OF A FEW AFTERNOON INSTABILITY SHOWERS AND OR THUNDERSTORMS
IS EXPECTED. LIGHT WIND UNDER 10 KNOTS EXCEPT GUSTY AND ERRATIC NEAR
SHOWERS.


SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 07Z SAT...SCT TO BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT
SHOWER. SOUTH WIND 5 TO 10 KNOTS. FROM 07Z SAT TO 23Z SAT...SCT CLDS
BASED NEAR 12 THSD AGL. LIGHT SOUTH TO SOUTHWEST WIND UNDER 10
KNOTS.


AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED MONDAY THROUGH TUESDAY. A COOLING TREND IS EXPECTED
WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT
BASIN AND PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM
WILL BE AN INCREASE IN WIND AREA-WIDE ON TUESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. BREEZY
CONDITIONS FROM THE WEST WILL PERSIST WEDNESDAY. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT. CONTINUED DRY AND WARMER CONDITIONS
ARE ON TAP FOR FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE
AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/CB









000
FXUS65 KPSR 190942
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
240 AM MST SAT APR 19 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL CONTINUE TO AFFECT THE AREA TODAY WITH
MORE EXTENSIVE CLOUDINESS AND LOCALIZED CHANCES FOR SHOWERS AND
THUNDERSTORMS. THE BEST CHANCES FOR RAINFALL WILL OCCUR ACROSS
CENTRAL AND EASTERN ARIZONA THROUGH THIS AFTERNOON. TEMPERATURES
TODAY WILL END UP NEAR SEASONAL VALUES...HOWEVER QUICKLY WARM BACK
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM PASSES TO THE
NORTHEAST.

&&

.DISCUSSION...
TWO DISTINCT VORTICITY CENTERS CAN BE SEEN IN REGIONAL RADAR/WV
SATELLITE IMAGERY EARLY THIS MORNING ROTATING ABOUT THE LARGER SCALE
CIRCULATION CENTER/COLD CORE PROGRESSING INTO SWRN ARIZONA. THE
INITIAL VORT MAX HAS LIFTED TO NEAR LAKE HAVASU UNDERGOING
SUBSTANTIAL STRETCHING AND DEFORMATION...WHILE A SECONDARY
INTENSIFYING VORTICITY CENTER/PV ANOMALY CORE WAS LIFTING TO THE
NORTH ACROSS THE BAJA PENINSULA AHEAD OF THE COLD CORE ALOFT AND
COLLOCATED WITHIN THE CORRIDOR OF A STRONGER JET STREAK. RECENT
SATELLITE LOOPS ALSO INDICATE MODEST CLOUD TOP COOLING AHEAD OF THIS
LATTER VORTICITY CENTER WITH OBJECTIVE ANALYSIS DEPICTING INCREASING
DIFLUENCE AND ASCENT BEGINNING TO ENVELOPE THE REGION. IN FACT...A
NICE CLUSTER OF THUNDERSTORMS HAVE FORMED IN NERN SONORA WHERE JET
DYNAMICS HAVE BECOME JUXTAPOSED WITH A SMALL LOW LEVEL MOISTURE
SURGE...STEEPENING LAPSE RATES...AND RESULTANT MUCAPES AOA 500 J/KG.

WHILE PROPAGATION TRAJECTORIES WILL TAKE THIS INITIAL CLUSTER OF
STORMS ONLY THOUGH FAR SERN ARIZONA THIS MORNING...OVERALL MIDLEVEL
LAPSE RATES WILL RAPIDLY STEEPEN (AOA 7.5 C/KM) ACROSS MUCH OF THE
FORECAST AREA AS THE COLD CORE MOVES DIRECTLY OVERHEAD. COMBINED
WITH PERSISTENT UVV...SFC HEATING...AND MOISTURE ADVECTION...THE
ATMOSPHERE ACROSS THE EASTERN PARTS OF THE CWA WILL BECOME
SUPPORTIVE FOR SUSTAINED DEEP CONVECTION THROUGH THE AFTERNOON
HOURS. SREF PROBABILITIES STILL STRONGLY SHOW ARGUMENTS FOR LI/S
NEAR -2C AND SBCAPES BETWEEN 250 AND 500 J/KG BY EARLY AFTERNOON.
HIGH RESOLUTIONS MODELS ALSO FORECAST ISOLD/SCT SHOWERS AND STORMS
TO MATERIALIZE THROUGH CNTRL AND ERN ARIZONA AHEAD OF THE VORTICITY
CENTER AND WITHIN THE CYCLONIC CURVATURE REGION OF THE JET.

WHILE ALL THESE THERMODYNAMIC PARAMETERS APPEAR FAVORABLE FOR MORE
WIDESPREAD CONVECTION...BOUNDARY LAYER MOISTURE WILL STILL BE
PROBLEMATIC (PARTICULARLY AT LOWER ELEVATION LOCATIONS) WITH MIXING
RATIOS ONLY APPROACHING 7 G/KG ADVECTING INTO THE AREA. THUS...WITH
CLOUD BASES ONLY FALLING TO AROUND THE H7 LEVEL...SUBSTANTIAL
SUBCLOUD DRY AIR WILL STILL EXIST AND ONLY THE MORE WIDELY SPACED
HEAVIER SHOWERS MAY LEAD TO ACCUMULATING RAINFALL. WIDESPREAD SVR
WEATHER IS NOT EXPECTED WITH ANY STORMS THAT DO FORM AS BULK 0-6KM
SHEAR WILL BECOME ALMOST NON-EXISTENT WITHIN THE LARGER SCALE
CIRCULATION CENTER AND 0-1KM SHEAR VECTORS WILL BE SIMILARLY
WEAK...HOWEVER MUCH LIKE FRIDAY AFTERNOON EVAPORATIONAL COOLING AND
DESCENT OF RAIN COOLED AIR COULD LEAD TO VERY ISOLATED STRONGER WIND
GUSTS.

THE CONGLOMERATE OF VORTICITY MAXIMA AND OVERALL CIRCULATION CENTER
WILL WEAKEN AND LIFT NORTHEAST SUNDAY AS HEIGHT RISES AND SUBSIDENCE
SLOWLY BUILD INTO THE SWRN CONUS. ENOUGH RESIDUAL MOISTURE AND
COOLER AIR ALOFT MAY BE PRESENT OVER ERN ARIZONA TO SUPPORT SOME
ISOLD AFTERNOON SHOWERS...PRIMARILY OVER THE WHITE MOUNTAINS BUT
POTENTIALLY CLIPPING THE SAN CARLOS AREA. OTHERWISE...H5 HEIGHTS AOA
582DM WILL BECOME MAXIMIZED ON MONDAY AFTERNOON YIELDING HIGHS IN
THE MID/UPPER 90S FOR LOWER ELEVATION LOCATIONS (AND POSSIBLY
TOUCHING 100 IN PREFERRED LOCATIONS OF FAR WRN ARIZONA).

A WELL DEFINED STOUT PACIFIC WAVE WILL CRASH ASHORE TUESDAY ACROSS
THE PACIFIC NORTHWEST...EVENTUALLY PROGRESSING INTO THE CNTRL/NRN
ROCKIES. MODEL OUTPUT REMAINS VERY CONSISTENT IN KEEPING THE TROUGH
BASE LIMITED TO FAR NORTHERN ARIZONA...WITH THE ENTIRE FORECAST AREA
STUCK IN SUBSIDENT ANTI-CYCLONIC FLOW. BY FAR...THE GREATEST IMPACT
WILL BE STRONG GUSTY WINDS ALONG AND IMMEDIATELY BEHIND THE LOW
LEVEL FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS
SUBSTANTIALLY TUESDAY AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA
AND THE LOWER COLORADO RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST
PROLONGED AND FREQUENT HIGHER WIND GUSTS.

OPERATIONAL AND ENSEMBLE MODEL SPREAD IS SOMEWHAT HIGHER THAN SEEN
RECENTLY FOR THE END OF NEXT WEEK...HOWEVER STILL REMAINS RELATIVELY
SMALL IN A SEASONAL SENSE. FLAT RIDGING AND/OR QUASI-ZONAL FLOW
SHOULD PREDOMINATE THE GENERAL PATTERN FOR THE MAJORITY OF TIME WITH
H5 HEIGHTS HOVERING NOT FAR FROM 576DM. THIS MODEL AVERAGE SOLUTION
FOR HEIGHTS ALOFT IS SLIGHTLY HIGHER THAN PREVIOUS MODEL
ITERATIONS...AND CONSEQUENTLY HAVE EDGED FORECAST HIGHS SLIGHTLY
WARMER TO JUST ABOVE CLIMATOLOGICAL LEVELS. THERE IS STILL NO
EVIDENCE SUPPORTING ANY PRECIPITATION MUCH OF NEXT WEEK...WITH ONLY
VERY LIMITED OPPORTUNITY POSSIBLY ARRIVING NEXT WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 17Z SAT...BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT SHOWER.
LIGHT EAST WIND UNDER 9 KNOTS. FROM 17Z SAT TO 23Z SAT...A PACIFIC
LOW PRESSURE SYSTEM WILL TRACK ACROSS CENTRAL AZ THIS PERIOD. A
CHANCE OF A FEW AFTERNOON INSTABILITY SHOWERS AND OR THUNDERSTORMS
IS EXPECTED. LIGHT WIND UNDER 10 KNOTS EXCEPT GUSTY AND ERRATIC NEAR
SHOWERS.


SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 07Z SAT...SCT TO BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT
SHOWER. SOUTH WIND 5 TO 10 KNOTS. FROM 07Z SAT TO 23Z SAT...SCT CLDS
BASED NEAR 12 THSD AGL. LIGHT SOUTH TO SOUTHWEST WIND UNDER 10
KNOTS.


AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED MONDAY THROUGH TUESDAY. A COOLING TREND IS EXPECTED
WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT
BASIN AND PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM
WILL BE AN INCREASE IN WIND AREA-WIDE ON TUESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. BREEZY
CONDITIONS FROM THE WEST WILL PERSIST WEDNESDAY. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT. CONTINUED DRY AND WARMER CONDITIONS
ARE ON TAP FOR FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE
AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/CB








000
FXUS65 KPSR 190326
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
830 PM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL AFFECT THE AREA TONIGHT AND SATURDAY
BRINGING EXTENSIVE CLOUDS...INCREASED MOISTURE AND LOCALIZED CHANCES
FOR SHOWERS THROUGH SATURDAY AFTERNOON. BEST CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES THROUGH SATURDAY WILL END UP NEAR
SEASONAL VALUES...HOWEVER QUICKLY WARMING BACK INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
THE PACIFIC LOW PRESSURE CENTER WAS LOCATED NEAR IMPERIAL CA AT 03Z
AND WILL CONTINUE TO MOVE EAST AND ACROSS CENTRAL AZ SATURDAY
AFTERNOON. ALTHOUGH THE AIRMASS MOISTURE UP A BIT FROM HIGHER PRECIP
WATER ADVECTION FRIDAY AFTERNOON...MOST DYNAMICS/UPPER LEVEL SUPPORT
FOR SHOWERS WILL BE RELEGATED TO SOUTHEAST AZ TONIGHT...MAINLY EAST
AND SOUTHEAST OF PHOENIX AND ESPECIALLY NEAR THE AZ SOUTHEAST
CORNER. THEREFORE THERE IS A MINIMAL CHANCE OF A LIGHT SHOWERS OR
SPRINKLES OVERNIGHT IN OUR FORECAST AREA.

AS THE COLD CORE OF THE UPPER LOW CENTER TRACKS ACROSS CENTRAL AZ
SATURDAY...AFTERNOON INSTABILITY COMBINED WITH CURVATURE EFFECTS OF
THE TROF SHOULD LEAD TO ANOTHER THREAT OF AFTERNOON SHOWERS AND
POSSIBLE THUNDERSTORMS...MAINLY ACROSS SOUTH CENTRAL AZ INCLUDING
PHOENIX. PARTS OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY
SATURDAY AFTERNOON SHOULD BE UNDER THE STABILIZING SUBSIDENCE FIELDS
FOUND ON THE BACKSIDE OF THE TROF.

CURRENT FORECASTS LOOK OK FOR NOW. NO UPDATES NECESSARY. PREVIOUS
DISCUSSION BELOW STILL APPLIES.

.PREVIOUS DISCUSSION...118 PM MST...
THE PACIFIC LOW PRESSURE SYSTEM HAS PROGRESSED INLAND INTO SOUTHERN
CALIFORNIA SINCE THIS MORNING WITH THE LOW CENTER RIGHT OVER SAN
DIEGO. NEARLY UNIDIRECTIONAL SOUTHERLY FLOW OVER MUCH OF ARIZONA
CONTINUES TO ADVECT IN MOISTURE...MAINLY ABOVE 700MB. CURRENT WATER
VAPOR IMAGERY SHOWS AN ORGANIZED SYNOPTIC LOW STRUCTURE WITH A
BAROCLINIC LEAF STRETCHING FROM SONORA MEXICO THROUGH EASTERN AND
NORTHERN ARIZONA. BROAD ASCENT ENCOMPASSES MUCH OF ARIZONA EARLY
THIS AFTERNOON IN RESPONSE TO A REGION OF UPPER DIFLUENCE NORTH OF
AN UPPER JET MAX NOSING INTO SOUTHEAST ARIZONA. AS A RESULT...
EXTENSIVE CLOUDINESS CONTINUES TO AFFECT THE REGION AS WELL AS
ISOLATED LIGHT SHOWERS OR SPRINKLES. LATE THIS MORNING...A SMALL
CLUSTER OF LIGHT SHOWERS DEVELOPED ACROSS NORTHERN PIMA COUNTY
ASSOCIATED WITH A PV ANOMALY AND A KINK SEEN IN THE 500MB HEIGHT
FIELD. FOR THE MOST PART...ANY SHOWERS TODAY WILL HAVE A DIFFICULT
TIME REACHING THE SURFACE DUE TO DRY AIR BELOW 700MB AS SHOWN BY
AREA THE INVERTED V STRUCTURE ON FORECAST SOUNDINGS. GUSTY OUTFLOW
WINDS NEAR 40MPH ALREADY OCCURRED WITH THE FIRST CLUSTER OF SHOWERS
THAT MOVED ACROSS PHOENIX AND ANY FURTHER SHOWER ACTIVITY TODAY WILL
BRING THE POTENTIAL FOR GUSTY WINDS AND POSSIBLY BLOWING DUST.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS AND STEEPER
LAPSE RATES REPRESENT A SLIGHTLY MORE UNSTABLE ENVIRONMENT WHICH MAY
GIVE RISE TO ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO BY
MID AFTERNOON ACROSS SOUTHEAST CALIFORNIA. EARLY MORNING RUNS OF THE
HI-RES HRRR AND LOCAL HI-RES MODELS SHOWED CELLS BLOSSOMING BY
AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST CALIFORNIA...BUT UPDATED
MODEL RUNS HAVE BACKED OFF ON COVERAGE. STILL THINKING 10-15 POPS IN
THIS AREA FOR THIS AFTERNOON AND EARLY EVENING IS A GOOD BET...BUT
WITH THE FAIRLY DRY AIR BELOW 700MB...RAINFALL AMOUNTS SHOULD MAINLY
BE IN THE TRACE TO A COUPLE HUNDREDTH OF AN INCH CATEGORY.

TONIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS TO THE
EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV ANOMALY
AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER ARIZONA. DURING
THIS TRANSITION...RENEWED VORTICITY ADVECTION AND ASCENT WILL ROTATE
THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN THE PRESENCE OF
RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND SREF
PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING NORTH
INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING UNDER
THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 17Z SAT...BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT SHOWER.
LIGHT EAST WIND UNDER 9 KNOTS. FROM 17Z SAT TO 23Z SAT...A PACIFIC
LOW PRESSURE SYSTEM WILL TRACK ACROSS CENTRAL AZ THIS PERIOD. A
CHANCE OF A FEW AFTERNOON INSTABILITY SHOWERS AND OR THUNDERSTORMS
IS EXPECTED. LIGHT WIND UNDER 10 KNOTS EXCEPT GUSTY AND ERRATIC NEAR
SHOWERS.


SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 07Z SAT...SCT TO BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT
SHOWER. SOUTH WIND 5 TO 10 KNOTS. FROM 07Z SAT TO 23Z SAT...SCT CLDS
BASED NEAR 12 THSD AGL. LIGHT SOUTH TO SOUTHWEST WIND UNDER 10
KNOTS.


AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED MONDAY THROUGH TUESDAY. A COOLING TREND IS EXPECTED
WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT
BASIN AND PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM
WILL BE AN INCREASE IN WIND AREA-WIDE ON TUESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. BREEZY
CONDITIONS FROM THE WEST WILL PERSIST WEDNESDAY. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT. CONTINUED DRY AND WARMER CONDITIONS
ARE ON TAP FOR FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE
AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...VASQUEZ/KUHLMAN/MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/CB











000
FXUS65 KPSR 190326
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
830 PM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL AFFECT THE AREA TONIGHT AND SATURDAY
BRINGING EXTENSIVE CLOUDS...INCREASED MOISTURE AND LOCALIZED CHANCES
FOR SHOWERS THROUGH SATURDAY AFTERNOON. BEST CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES THROUGH SATURDAY WILL END UP NEAR
SEASONAL VALUES...HOWEVER QUICKLY WARMING BACK INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
THE PACIFIC LOW PRESSURE CENTER WAS LOCATED NEAR IMPERIAL CA AT 03Z
AND WILL CONTINUE TO MOVE EAST AND ACROSS CENTRAL AZ SATURDAY
AFTERNOON. ALTHOUGH THE AIRMASS MOISTURE UP A BIT FROM HIGHER PRECIP
WATER ADVECTION FRIDAY AFTERNOON...MOST DYNAMICS/UPPER LEVEL SUPPORT
FOR SHOWERS WILL BE RELEGATED TO SOUTHEAST AZ TONIGHT...MAINLY EAST
AND SOUTHEAST OF PHOENIX AND ESPECIALLY NEAR THE AZ SOUTHEAST
CORNER. THEREFORE THERE IS A MINIMAL CHANCE OF A LIGHT SHOWERS OR
SPRINKLES OVERNIGHT IN OUR FORECAST AREA.

AS THE COLD CORE OF THE UPPER LOW CENTER TRACKS ACROSS CENTRAL AZ
SATURDAY...AFTERNOON INSTABILITY COMBINED WITH CURVATURE EFFECTS OF
THE TROF SHOULD LEAD TO ANOTHER THREAT OF AFTERNOON SHOWERS AND
POSSIBLE THUNDERSTORMS...MAINLY ACROSS SOUTH CENTRAL AZ INCLUDING
PHOENIX. PARTS OF SOUTHEAST CA AND THE COLORADO RIVER VALLEY
SATURDAY AFTERNOON SHOULD BE UNDER THE STABILIZING SUBSIDENCE FIELDS
FOUND ON THE BACKSIDE OF THE TROF.

CURRENT FORECASTS LOOK OK FOR NOW. NO UPDATES NECESSARY. PREVIOUS
DISCUSSION BELOW STILL APPLIES.

.PREVIOUS DISCUSSION...118 PM MST...
THE PACIFIC LOW PRESSURE SYSTEM HAS PROGRESSED INLAND INTO SOUTHERN
CALIFORNIA SINCE THIS MORNING WITH THE LOW CENTER RIGHT OVER SAN
DIEGO. NEARLY UNIDIRECTIONAL SOUTHERLY FLOW OVER MUCH OF ARIZONA
CONTINUES TO ADVECT IN MOISTURE...MAINLY ABOVE 700MB. CURRENT WATER
VAPOR IMAGERY SHOWS AN ORGANIZED SYNOPTIC LOW STRUCTURE WITH A
BAROCLINIC LEAF STRETCHING FROM SONORA MEXICO THROUGH EASTERN AND
NORTHERN ARIZONA. BROAD ASCENT ENCOMPASSES MUCH OF ARIZONA EARLY
THIS AFTERNOON IN RESPONSE TO A REGION OF UPPER DIFLUENCE NORTH OF
AN UPPER JET MAX NOSING INTO SOUTHEAST ARIZONA. AS A RESULT...
EXTENSIVE CLOUDINESS CONTINUES TO AFFECT THE REGION AS WELL AS
ISOLATED LIGHT SHOWERS OR SPRINKLES. LATE THIS MORNING...A SMALL
CLUSTER OF LIGHT SHOWERS DEVELOPED ACROSS NORTHERN PIMA COUNTY
ASSOCIATED WITH A PV ANOMALY AND A KINK SEEN IN THE 500MB HEIGHT
FIELD. FOR THE MOST PART...ANY SHOWERS TODAY WILL HAVE A DIFFICULT
TIME REACHING THE SURFACE DUE TO DRY AIR BELOW 700MB AS SHOWN BY
AREA THE INVERTED V STRUCTURE ON FORECAST SOUNDINGS. GUSTY OUTFLOW
WINDS NEAR 40MPH ALREADY OCCURRED WITH THE FIRST CLUSTER OF SHOWERS
THAT MOVED ACROSS PHOENIX AND ANY FURTHER SHOWER ACTIVITY TODAY WILL
BRING THE POTENTIAL FOR GUSTY WINDS AND POSSIBLY BLOWING DUST.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS AND STEEPER
LAPSE RATES REPRESENT A SLIGHTLY MORE UNSTABLE ENVIRONMENT WHICH MAY
GIVE RISE TO ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO BY
MID AFTERNOON ACROSS SOUTHEAST CALIFORNIA. EARLY MORNING RUNS OF THE
HI-RES HRRR AND LOCAL HI-RES MODELS SHOWED CELLS BLOSSOMING BY
AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST CALIFORNIA...BUT UPDATED
MODEL RUNS HAVE BACKED OFF ON COVERAGE. STILL THINKING 10-15 POPS IN
THIS AREA FOR THIS AFTERNOON AND EARLY EVENING IS A GOOD BET...BUT
WITH THE FAIRLY DRY AIR BELOW 700MB...RAINFALL AMOUNTS SHOULD MAINLY
BE IN THE TRACE TO A COUPLE HUNDREDTH OF AN INCH CATEGORY.

TONIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS TO THE
EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV ANOMALY
AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER ARIZONA. DURING
THIS TRANSITION...RENEWED VORTICITY ADVECTION AND ASCENT WILL ROTATE
THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN THE PRESENCE OF
RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND SREF
PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING NORTH
INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING UNDER
THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THROUGH 17Z SAT...BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT SHOWER.
LIGHT EAST WIND UNDER 9 KNOTS. FROM 17Z SAT TO 23Z SAT...A PACIFIC
LOW PRESSURE SYSTEM WILL TRACK ACROSS CENTRAL AZ THIS PERIOD. A
CHANCE OF A FEW AFTERNOON INSTABILITY SHOWERS AND OR THUNDERSTORMS
IS EXPECTED. LIGHT WIND UNDER 10 KNOTS EXCEPT GUSTY AND ERRATIC NEAR
SHOWERS.


SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 07Z SAT...SCT TO BKN CLDS AOA 12 THSD AGL. ISOLATED LIGHT
SHOWER. SOUTH WIND 5 TO 10 KNOTS. FROM 07Z SAT TO 23Z SAT...SCT CLDS
BASED NEAR 12 THSD AGL. LIGHT SOUTH TO SOUTHWEST WIND UNDER 10
KNOTS.


AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED MONDAY THROUGH TUESDAY. A COOLING TREND IS EXPECTED
WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT
BASIN AND PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM
WILL BE AN INCREASE IN WIND AREA-WIDE ON TUESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. BREEZY
CONDITIONS FROM THE WEST WILL PERSIST WEDNESDAY. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT. CONTINUED DRY AND WARMER CONDITIONS
ARE ON TAP FOR FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE
AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...VASQUEZ/KUHLMAN/MO
AVIATION...VASQUEZ
FIRE WEATHER...MEYERS/CB










000
FXUS65 KPSR 182018
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
118 PM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL AFFECT THE AREA TONIGHT AND SATURDAY
BRINGING EXTENSIVE CLOUDS...INCREASED MOISTURE AND LOCALIZED CHANCES
FOR SHOWERS THROUGH SATURDAY AFTERNOON. BEST CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES THROUGH SATURDAY WILL END UP NEAR
SEASONAL VALUES...HOWEVER QUICKLY WARMING BACK INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
THE PACIFIC LOW PRESSURE SYSTEM HAS PROGRESSED INLAND INTO SOUTHERN
CALIFORNIA SINCE THIS MORNING WITH THE LOW CENTER RIGHT OVER SAN
DIEGO. NEARLY UNIDIRECTIONAL SOUTHERLY FLOW OVER MUCH OF ARIZONA
CONTINUES TO ADVECT IN MOISTURE...MAINLY ABOVE 700MB. CURRENT WATER
VAPOR IMAGERY SHOWS AN ORGANIZED SYNOPTIC LOW STRUCTURE WITH A
BAROCLINIC LEAF STRETCHING FROM SONORA MEXICO THROUGH EASTERN AND
NORTHERN ARIZONA. BROAD ASCENT ENCOMPASSES MUCH OF ARIZONA EARLY
THIS AFTERNOON IN RESPONSE TO A REGION OF UPPER DIFLUENCE NORTH OF
AN UPPER JET MAX NOSING INTO SOUTHEAST ARIZONA. AS A RESULT...
EXTENSIVE CLOUDINESS CONTINUES TO AFFECT THE REGION AS WELL AS
ISOLATED LIGHT SHOWERS OR SPRINKLES. LATE THIS MORNING...A SMALL
CLUSTER OF LIGHT SHOWERS DEVELOPED ACROSS NORTHERN PIMA COUNTY
ASSOCIATED WITH A PV ANOMALY AND A KINK SEEN IN THE 500MB HEIGHT
FIELD. FOR THE MOST PART...ANY SHOWERS TODAY WILL HAVE A DIFFICULT
TIME REACHING THE SURFACE DUE TO DRY AIR BELOW 700MB AS SHOWN BY
AREA THE INVERTED V STRUCTURE ON FORECAST SOUNDINGS. GUSTY OUTFLOW
WINDS NEAR 40MPH ALREADY OCCURRED WITH THE FIRST CLUSTER OF SHOWERS
THAT MOVED ACROSS PHOENIX AND ANY FURTHER SHOWER ACTIVITY TODAY WILL
BRING THE POTENTIAL FOR GUSTY WINDS AND POSSIBLY BLOWING DUST.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS AND STEEPER
LAPSE RATES REPRESENT A SLIGHTLY MORE UNSTABLE ENVIRONMENT WHICH MAY
GIVE RISE TO ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO BY
MID AFTERNOON ACROSS SOUTHEAST CALIFORNIA. EARLY MORNING RUNS OF THE
HI-RES HRRR AND LOCAL HI-RES MODELS SHOWED CELLS BLOSSOMING BY
AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST CALIFORNIA...BUT UPDATED
MODEL RUNS HAVE BACKED OFF ON COVERAGE. STILL THINKING 10-15 POPS IN
THIS AREA FOR THIS AFTERNOON AND EARLY EVENING IS A GOOD BET...BUT
WITH THE FAIRLY DRY AIR BELOW 700MB...RAINFALL AMOUNTS SHOULD MAINLY
BE IN THE TRACE TO A COUPLE HUNDREDTH OF AN INCH CATEGORY.

TONIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS TO THE
EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV ANOMALY
AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER ARIZONA. DURING
THIS TRANSITION...RENEWED VORTICITY ADVECTION AND ASCENT WILL ROTATE
THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN THE PRESENCE OF
RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND SREF
PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING NORTH
INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING UNDER
THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS WILL FAVOR THE SOUTH OR SOUTHEAST THROUGH
THE AFTERNOON ...WITH OCCASIONAL GUSTS OVER 25KT...OCCASIONALLY
VEERING TO THE SOUTHWEST...ALONG WITH BROKEN CLOUD DECKS GENERALLY
AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER NATURE OF THE
ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED AFTN THUNDERSTORMS WITH
STRONG GUSTY DOWNDRAFTS IN EXCESS OF 30KT POSSIBLE NEAR
KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE BLOWING DUST
ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO 4SM...BUT NOT
PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND THUNDERSTORM
ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL OVERNIGHT...BUT
WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED MONDAY THROUGH TUESDAY. A COOLING TREND IS EXPECTED
WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT
BASIN AND PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM
WILL BE AN INCREASE IN WIND AREA-WIDE ON TUESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. BREEZY
CONDITIONS FROM THE WEST WILL PERSIST WEDNESDAY. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT. CONTINUED DRY AND WARMER CONDITIONS
ARE ON TAP FOR FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE
AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN/MO
AVIATION...MEYERS/CB
FIRE WEATHER...MEYERS/CB







000
FXUS65 KPSR 182018
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
118 PM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL AFFECT THE AREA TONIGHT AND SATURDAY
BRINGING EXTENSIVE CLOUDS...INCREASED MOISTURE AND LOCALIZED CHANCES
FOR SHOWERS THROUGH SATURDAY AFTERNOON. BEST CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES THROUGH SATURDAY WILL END UP NEAR
SEASONAL VALUES...HOWEVER QUICKLY WARMING BACK INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
THE PACIFIC LOW PRESSURE SYSTEM HAS PROGRESSED INLAND INTO SOUTHERN
CALIFORNIA SINCE THIS MORNING WITH THE LOW CENTER RIGHT OVER SAN
DIEGO. NEARLY UNIDIRECTIONAL SOUTHERLY FLOW OVER MUCH OF ARIZONA
CONTINUES TO ADVECT IN MOISTURE...MAINLY ABOVE 700MB. CURRENT WATER
VAPOR IMAGERY SHOWS AN ORGANIZED SYNOPTIC LOW STRUCTURE WITH A
BAROCLINIC LEAF STRETCHING FROM SONORA MEXICO THROUGH EASTERN AND
NORTHERN ARIZONA. BROAD ASCENT ENCOMPASSES MUCH OF ARIZONA EARLY
THIS AFTERNOON IN RESPONSE TO A REGION OF UPPER DIFLUENCE NORTH OF
AN UPPER JET MAX NOSING INTO SOUTHEAST ARIZONA. AS A RESULT...
EXTENSIVE CLOUDINESS CONTINUES TO AFFECT THE REGION AS WELL AS
ISOLATED LIGHT SHOWERS OR SPRINKLES. LATE THIS MORNING...A SMALL
CLUSTER OF LIGHT SHOWERS DEVELOPED ACROSS NORTHERN PIMA COUNTY
ASSOCIATED WITH A PV ANOMALY AND A KINK SEEN IN THE 500MB HEIGHT
FIELD. FOR THE MOST PART...ANY SHOWERS TODAY WILL HAVE A DIFFICULT
TIME REACHING THE SURFACE DUE TO DRY AIR BELOW 700MB AS SHOWN BY
AREA THE INVERTED V STRUCTURE ON FORECAST SOUNDINGS. GUSTY OUTFLOW
WINDS NEAR 40MPH ALREADY OCCURRED WITH THE FIRST CLUSTER OF SHOWERS
THAT MOVED ACROSS PHOENIX AND ANY FURTHER SHOWER ACTIVITY TODAY WILL
BRING THE POTENTIAL FOR GUSTY WINDS AND POSSIBLY BLOWING DUST.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS AND STEEPER
LAPSE RATES REPRESENT A SLIGHTLY MORE UNSTABLE ENVIRONMENT WHICH MAY
GIVE RISE TO ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO BY
MID AFTERNOON ACROSS SOUTHEAST CALIFORNIA. EARLY MORNING RUNS OF THE
HI-RES HRRR AND LOCAL HI-RES MODELS SHOWED CELLS BLOSSOMING BY
AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST CALIFORNIA...BUT UPDATED
MODEL RUNS HAVE BACKED OFF ON COVERAGE. STILL THINKING 10-15 POPS IN
THIS AREA FOR THIS AFTERNOON AND EARLY EVENING IS A GOOD BET...BUT
WITH THE FAIRLY DRY AIR BELOW 700MB...RAINFALL AMOUNTS SHOULD MAINLY
BE IN THE TRACE TO A COUPLE HUNDREDTH OF AN INCH CATEGORY.

TONIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS TO THE
EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV ANOMALY
AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER ARIZONA. DURING
THIS TRANSITION...RENEWED VORTICITY ADVECTION AND ASCENT WILL ROTATE
THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN THE PRESENCE OF
RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND SREF
PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING NORTH
INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING UNDER
THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS WILL FAVOR THE SOUTH OR SOUTHEAST THROUGH
THE AFTERNOON ...WITH OCCASIONAL GUSTS OVER 25KT...OCCASIONALLY
VEERING TO THE SOUTHWEST...ALONG WITH BROKEN CLOUD DECKS GENERALLY
AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER NATURE OF THE
ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED AFTN THUNDERSTORMS WITH
STRONG GUSTY DOWNDRAFTS IN EXCESS OF 30KT POSSIBLE NEAR
KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE BLOWING DUST
ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO 4SM...BUT NOT
PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND THUNDERSTORM
ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL OVERNIGHT...BUT
WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
WESTERLY FLOW ALOFT WILL BRING A WARMING AND DRYING TREND TO THE
REGION THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER
THE INTERMOUNTAIN WEST. WELL ABOVE SEASONAL NORMAL HIGH TEMPERATURES
ARE EXPECTED MONDAY THROUGH TUESDAY. A COOLING TREND IS EXPECTED
WEDNESDAY AND THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT
BASIN AND PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM
WILL BE AN INCREASE IN WIND AREA-WIDE ON TUESDAY...WITH GUSTS UP TO
35 MPH POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. BREEZY
CONDITIONS FROM THE WEST WILL PERSIST WEDNESDAY. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT. CONTINUED DRY AND WARMER CONDITIONS
ARE ON TAP FOR FRIDAY AS HIGH PRESSURE ALOFT BUILDS BACK INTO THE
AREA.


&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN/MO
AVIATION...MEYERS/CB
FIRE WEATHER...MEYERS/CB








000
FXUS65 KPSR 181848 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
1145 AM MST FRI APR 18 2014

.UPDATE...UPDATED AVIATION DISCUSSION.

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA TODAY BRINGING
EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED CHANCES FOR
SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH TONIGHT...ANY RAINFALL
WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN LOCATIONS...WITH
SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY WILL FALL TO MORE
SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
REGIONAL SATELLITE IMAGERY SHOWS EXTENSIVE MID AND HIGH CLOUDS AND
THICK ENOUGH TO BE OPAQUE IN MOST AREAS. OVERNIGHT LOWS WERE ON THE
WARM SIDE DUE TO THE CLOUDS...ON THE ORDER OF 5-10 DEGREES ABOVE
NORMAL. THE SITUATION TODAY AND SATURDAY WILL INVOLVE A FAIRLY
IMPRESSIVE PACIFIC LOW CURRENTLY CENTERED NEAR SAN DIEGO WITH
COPIOUS MID LEVEL MOISTURE STREAMING INTO THE SOUTHERN HALF OF
ARIZONA AND SOUTHEAST CALIFORNIA. THERE ARE SOME LIGHT RADAR
RETURNS SHOWING UP TO THE WEST OF TUCSON AND OVER THE GULF OF
CALIFORNIA...BUT ALL OF THIS IS HIGH BASED AND LIKELY ONLY VIRGA.
LOCAL 12Z SOUNDINGS THIS MORNING SHOWED OVERALL DRY AIR BELOW 400MB
AT TUCSON AND FLAGSTAFF...BUT EXTENSIVE MOISTURE ABOVE 600MB AT SAN
DIEGO. WARM AND DRY MID LEVELS WILL KEEP ANY SUBSTANTIAL
SHOWER/THUNDERSTORM ACTIVITY FROM FORMING ACROSS SOUTHERN ARIZONA
THROUGH THIS AFTERNOON...BUT SHOULD SEE SOME ISOLATED TO SCATTERED
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS AND MOSTLY VIRGA ACROSS
THE DESERTS.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS...STEEPER LAPSE
RATES...AND THUS MORE UNSTABLE CONDITIONS ARE EXPECTED TO GIVE RISE
TO ISOLATED SHOWERS AND THUNDERSTORMS BY MID AFTERNOON ACROSS
SOUTHEAST CALIFORNIA. HI-RES HRRR AND LOCAL HI-RES MODELS SHOW CELLS
BLOSSOMING BY AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST
CALIFORNIA...BUT WITH FAIRLY DRY AIR BELOW 700MB RAINFALL AMOUNTS
WILL BE LIMITED TO GENERALLY LESS THAN A TENTH OF AN INCH. HAVE
BUMPED UP POPS SLIGHTLY FOR THIS AFTERNOON ACROSS OUR WESTERN
ZONES...BUT ONLY ON THE ORDER OF 5-10 PERCENT. GUSTY OUTFLOW WINDS
WILL REMAIN A CONCERN THROUGHOUT THE AREA DURING THE DAYLIGHT
HOURS...ESPECIALLY WEST OF MARICOPA COUNTY.

&&

.PREVIOUS DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS...DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS WILL FAVOR THE SOUTH OR SOUTHEAST THROUGH
THE AFTERNOON ...WITH OCCASIONAL GUSTS OVER 25KT...OCCASIONALLY
VEERING TO THE SOUTHWEST...ALONG WITH BROKEN CLOUD DECKS GENERALLY
AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER NATURE OF THE
ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED AFTN THUNDERSTORMS WITH
STRONG GUSTY DOWNDRAFTS IN EXCESS OF 30KT POSSIBLE NEAR
KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE BLOWING DUST
ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO 4SM...BUT NOT
PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND THUNDERSTORM
ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL OVERNIGHT...BUT
WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER THE
INTERMOUNTAIN WEST. A COOLING TREND IS EXPECTED WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE ON WEDNESDAY...WITH GUSTS UP TO 35 MPH
POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS/CB
FIRE WEATHER...MEYERS











000
FXUS65 KPSR 181848 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
1145 AM MST FRI APR 18 2014

.UPDATE...UPDATED AVIATION DISCUSSION.

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA TODAY BRINGING
EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED CHANCES FOR
SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH TONIGHT...ANY RAINFALL
WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN LOCATIONS...WITH
SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY WILL FALL TO MORE
SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
REGIONAL SATELLITE IMAGERY SHOWS EXTENSIVE MID AND HIGH CLOUDS AND
THICK ENOUGH TO BE OPAQUE IN MOST AREAS. OVERNIGHT LOWS WERE ON THE
WARM SIDE DUE TO THE CLOUDS...ON THE ORDER OF 5-10 DEGREES ABOVE
NORMAL. THE SITUATION TODAY AND SATURDAY WILL INVOLVE A FAIRLY
IMPRESSIVE PACIFIC LOW CURRENTLY CENTERED NEAR SAN DIEGO WITH
COPIOUS MID LEVEL MOISTURE STREAMING INTO THE SOUTHERN HALF OF
ARIZONA AND SOUTHEAST CALIFORNIA. THERE ARE SOME LIGHT RADAR
RETURNS SHOWING UP TO THE WEST OF TUCSON AND OVER THE GULF OF
CALIFORNIA...BUT ALL OF THIS IS HIGH BASED AND LIKELY ONLY VIRGA.
LOCAL 12Z SOUNDINGS THIS MORNING SHOWED OVERALL DRY AIR BELOW 400MB
AT TUCSON AND FLAGSTAFF...BUT EXTENSIVE MOISTURE ABOVE 600MB AT SAN
DIEGO. WARM AND DRY MID LEVELS WILL KEEP ANY SUBSTANTIAL
SHOWER/THUNDERSTORM ACTIVITY FROM FORMING ACROSS SOUTHERN ARIZONA
THROUGH THIS AFTERNOON...BUT SHOULD SEE SOME ISOLATED TO SCATTERED
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS AND MOSTLY VIRGA ACROSS
THE DESERTS.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS...STEEPER LAPSE
RATES...AND THUS MORE UNSTABLE CONDITIONS ARE EXPECTED TO GIVE RISE
TO ISOLATED SHOWERS AND THUNDERSTORMS BY MID AFTERNOON ACROSS
SOUTHEAST CALIFORNIA. HI-RES HRRR AND LOCAL HI-RES MODELS SHOW CELLS
BLOSSOMING BY AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST
CALIFORNIA...BUT WITH FAIRLY DRY AIR BELOW 700MB RAINFALL AMOUNTS
WILL BE LIMITED TO GENERALLY LESS THAN A TENTH OF AN INCH. HAVE
BUMPED UP POPS SLIGHTLY FOR THIS AFTERNOON ACROSS OUR WESTERN
ZONES...BUT ONLY ON THE ORDER OF 5-10 PERCENT. GUSTY OUTFLOW WINDS
WILL REMAIN A CONCERN THROUGHOUT THE AREA DURING THE DAYLIGHT
HOURS...ESPECIALLY WEST OF MARICOPA COUNTY.

&&

.PREVIOUS DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS...DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS WILL FAVOR THE SOUTH OR SOUTHEAST THROUGH
THE AFTERNOON ...WITH OCCASIONAL GUSTS OVER 25KT...OCCASIONALLY
VEERING TO THE SOUTHWEST...ALONG WITH BROKEN CLOUD DECKS GENERALLY
AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER NATURE OF THE
ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED AFTN THUNDERSTORMS WITH
STRONG GUSTY DOWNDRAFTS IN EXCESS OF 30KT POSSIBLE NEAR
KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE BLOWING DUST
ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO 4SM...BUT NOT
PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND THUNDERSTORM
ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL OVERNIGHT...BUT
WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER THE
INTERMOUNTAIN WEST. A COOLING TREND IS EXPECTED WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE ON WEDNESDAY...WITH GUSTS UP TO 35 MPH
POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS/CB
FIRE WEATHER...MEYERS










000
FXUS65 KPSR 181553
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
853 AM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA TODAY BRINGING
EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED CHANCES FOR
SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH TONIGHT...ANY RAINFALL
WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN LOCATIONS...WITH
SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY WILL FALL TO MORE
SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
REGIONAL SATELLITE IMAGERY SHOWS EXTENSIVE MID AND HIGH CLOUDS AND
THICK ENOUGH TO BE OPAQUE IN MOST AREAS. OVERNIGHT LOWS WERE ON THE
WARM SIDE DUE TO THE CLOUDS...ON THE ORDER OF 5-10 DEGREES ABOVE
NORMAL. THE SITUATION TODAY AND SATURDAY WILL INVOLVE A FAIRLY
IMPRESSIVE PACIFIC LOW CURRENTLY CENTERED NEAR SAN DIEGO WITH
COPIOUS MID LEVEL MOISTURE STREAMING INTO THE SOUTHERN HALF OF
ARIZONA AND SOUTHEAST CALIFORNIA. THERE ARE SOME LIGHT RADAR
RETURNS SHOWING UP TO THE WEST OF TUCSON AND OVER THE GULF OF
CALIFORNIA...BUT ALL OF THIS IS HIGH BASED AND LIKELY ONLY VIRGA.
LOCAL 12Z SOUNDINGS THIS MORNING SHOWED OVERALL DRY AIR BELOW 400MB
AT TUCSON AND FLAGSTAFF...BUT EXTENSIVE MOISTURE ABOVE 600MB AT SAN
DIEGO. WARM AND DRY MID LEVELS WILL KEEP ANY SUBSTANTIAL
SHOWER/THUNDERSTORM ACTIVITY FROM FORMING ACROSS SOUTHERN ARIZONA
THROUGH THIS AFTERNOON...BUT SHOULD SEE SOME ISOLATED TO SCATTERED
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS AND MOSTLY VIRGA ACROSS
THE DESERTS.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS...STEEPER LAPSE
RATES...AND THUS MORE UNSTABLE CONDITIONS ARE EXPECTED TO GIVE RISE
TO ISOLATED SHOWERS AND THUNDERSTORMS BY MID AFTERNOON ACROSS
SOUTHEAST CALIFORNIA. HI-RES HRRR AND LOCAL HI-RES MODELS SHOW CELLS
BLOSSOMING BY AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST
CALIFORNIA...BUT WITH FAIRLY DRY AIR BELOW 700MB RAINFALL AMOUNTS
WILL BE LIMITED TO GENERALLY LESS THAN A TENTH OF AN INCH. HAVE
BUMPED UP POPS SLIGHTLY FOR THIS AFTERNOON ACROSS OUR WESTERN
ZONES...BUT ONLY ON THE ORDER OF 5-10 PERCENT. GUSTY OUTFLOW WINDS
WILL REMAIN A CONCERN THROUGHOUT THE AREA DURING THE DAYLIGHT
HOURS...ESPECIALLY WEST OF MARICOPA COUNTY.

&&

.PREVIOUS DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS...DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS BECOME SOUTH-SOUTHWEST AND INCREASE WITH
GUSTS UP TO 20KTS AFTER 17Z...ALONG WITH BROKEN CLOUD DECKS
GENERALLY AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER
NATURE OF THE ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED THUNDERSTORMS
WITH STRONG GUSTY DOWNDRAFTS POSSIBLE LATER THIS AFTERNOON...MAINLY
AFTER 23Z NEAR KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE
BLOWING DUST ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO
4SM...BUT NOT PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND
THUNDERSTORM ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL
OVERNIGHT...BUT WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO
SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER THE
INTERMOUNTAIN WEST. A COOLING TREND IS EXPECTED WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE ON WEDNESDAY...WITH GUSTS UP TO 35 MPH
POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS








000
FXUS65 KPSR 181553
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
853 AM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA TODAY BRINGING
EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED CHANCES FOR
SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH TONIGHT...ANY RAINFALL
WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN LOCATIONS...WITH
SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER CHANCES FOR SHOWERS
AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS CENTRAL AND EASTERN
ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY WILL FALL TO MORE
SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL INTO THE 90S EARLY
NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
REGIONAL SATELLITE IMAGERY SHOWS EXTENSIVE MID AND HIGH CLOUDS AND
THICK ENOUGH TO BE OPAQUE IN MOST AREAS. OVERNIGHT LOWS WERE ON THE
WARM SIDE DUE TO THE CLOUDS...ON THE ORDER OF 5-10 DEGREES ABOVE
NORMAL. THE SITUATION TODAY AND SATURDAY WILL INVOLVE A FAIRLY
IMPRESSIVE PACIFIC LOW CURRENTLY CENTERED NEAR SAN DIEGO WITH
COPIOUS MID LEVEL MOISTURE STREAMING INTO THE SOUTHERN HALF OF
ARIZONA AND SOUTHEAST CALIFORNIA. THERE ARE SOME LIGHT RADAR
RETURNS SHOWING UP TO THE WEST OF TUCSON AND OVER THE GULF OF
CALIFORNIA...BUT ALL OF THIS IS HIGH BASED AND LIKELY ONLY VIRGA.
LOCAL 12Z SOUNDINGS THIS MORNING SHOWED OVERALL DRY AIR BELOW 400MB
AT TUCSON AND FLAGSTAFF...BUT EXTENSIVE MOISTURE ABOVE 600MB AT SAN
DIEGO. WARM AND DRY MID LEVELS WILL KEEP ANY SUBSTANTIAL
SHOWER/THUNDERSTORM ACTIVITY FROM FORMING ACROSS SOUTHERN ARIZONA
THROUGH THIS AFTERNOON...BUT SHOULD SEE SOME ISOLATED TO SCATTERED
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS AND MOSTLY VIRGA ACROSS
THE DESERTS.

FURTHER WEST NEAR THE LOW CENTER...COOLER MID LEVELS...STEEPER LAPSE
RATES...AND THUS MORE UNSTABLE CONDITIONS ARE EXPECTED TO GIVE RISE
TO ISOLATED SHOWERS AND THUNDERSTORMS BY MID AFTERNOON ACROSS
SOUTHEAST CALIFORNIA. HI-RES HRRR AND LOCAL HI-RES MODELS SHOW CELLS
BLOSSOMING BY AROUND 21Z THIS AFTERNOON ACROSS SOUTHEAST
CALIFORNIA...BUT WITH FAIRLY DRY AIR BELOW 700MB RAINFALL AMOUNTS
WILL BE LIMITED TO GENERALLY LESS THAN A TENTH OF AN INCH. HAVE
BUMPED UP POPS SLIGHTLY FOR THIS AFTERNOON ACROSS OUR WESTERN
ZONES...BUT ONLY ON THE ORDER OF 5-10 PERCENT. GUSTY OUTFLOW WINDS
WILL REMAIN A CONCERN THROUGHOUT THE AREA DURING THE DAYLIGHT
HOURS...ESPECIALLY WEST OF MARICOPA COUNTY.

&&

.PREVIOUS DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS...DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS BECOME SOUTH-SOUTHWEST AND INCREASE WITH
GUSTS UP TO 20KTS AFTER 17Z...ALONG WITH BROKEN CLOUD DECKS
GENERALLY AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER
NATURE OF THE ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED THUNDERSTORMS
WITH STRONG GUSTY DOWNDRAFTS POSSIBLE LATER THIS AFTERNOON...MAINLY
AFTER 23Z NEAR KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE
BLOWING DUST ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO
4SM...BUT NOT PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND
THUNDERSTORM ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL
OVERNIGHT...BUT WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO
SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER THE
INTERMOUNTAIN WEST. A COOLING TREND IS EXPECTED WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE ON WEDNESDAY...WITH GUSTS UP TO 35 MPH
POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS







000
FXUS65 KPSR 181314 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
611 AM MST FRI APR 18 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSION.

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA STARTING TODAY
BRINGING EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED
CHANCES FOR SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH
TONIGHT...ANY RAINFALL WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN
LOCATIONS...WITH SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS
CENTRAL AND EASTERN ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY
WILL FALL TO MORE SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS...DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS BECOME SOUTH-SOUTHWEST AND INCREASE WITH
GUSTS UP TO 20KTS AFTER 17Z...ALONG WITH BROKEN CLOUD DECKS
GENERALLY AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER
NATURE OF THE ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED THUNDERSTORMS
WITH STRONG GUSTY DOWNDRAFTS POSSIBLE LATER THIS AFTERNOON...MAINLY
AFTER 23Z NEAR KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE
BLOWING DUST ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO
4SM...BUT NOT PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND
THUNDERSTORM ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL
OVERNIGHT...BUT WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO
SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER THE
INTERMOUNTAIN WEST. A COOLING TREND IS EXPECTED WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE ON WEDNESDAY...WITH GUSTS UP TO 35 MPH
POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS







000
FXUS65 KPSR 181314 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
611 AM MST FRI APR 18 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSION.

&&

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA STARTING TODAY
BRINGING EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED
CHANCES FOR SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH
TONIGHT...ANY RAINFALL WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN
LOCATIONS...WITH SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS
CENTRAL AND EASTERN ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY
WILL FALL TO MORE SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS...DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

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

INCREASING CLOUDS...MOISTURE AND INSTABILITY ACROSS THE AREA WITH
THE APPROACH OF A PACIFIC LOW PRESSURE SYSTEM OFF THE SOUTHERN
CALIFORNIA COAST. WINDS BECOME SOUTH-SOUTHWEST AND INCREASE WITH
GUSTS UP TO 20KTS AFTER 17Z...ALONG WITH BROKEN CLOUD DECKS
GENERALLY AOB 12KFT AND LOCAL CIGS DOWN TO 10KFT AT TIMES. DRIER
NATURE OF THE ATMOSPHERE WILL LEAD TO VIRGA/ISOLATED THUNDERSTORMS
WITH STRONG GUSTY DOWNDRAFTS POSSIBLE LATER THIS AFTERNOON...MAINLY
AFTER 23Z NEAR KPHX/KIWA/KSDL. OUTFLOW HAS POTENTIAL TO GENERATE
BLOWING DUST ACROSS LOWER DESERTS AND LOWER VISIBILITY DOWN TO
4SM...BUT NOT PLACING ANY REDUCTIONS IN TAFS THIS TIME. SHOWER AND
THUNDERSTORM ACTIVITY TAPERS OFF OVER WESTERN TAF SITES KBLH/KIPL
OVERNIGHT...BUT WILL LINGER ACROSS SOUTH-CENTRAL ARIZONA INTO
SATURDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY AS A RIDGE OF HIGH PRESSURE ESTABLISHES OVER THE
INTERMOUNTAIN WEST. A COOLING TREND IS EXPECTED WEDNESDAY AND
THURSDAY AS A LOW PRESSURE SYSTEM MOVES INTO THE GREAT BASIN AND
PACIFIC NORTHWEST. THE BIGGEST IMPACT WITH THIS SYSTEM WILL BE AN
INCREASE IN WIND AREA-WIDE ON WEDNESDAY...WITH GUSTS UP TO 35 MPH
POSSIBLE...ESPECIALLY ACROSS SOUTHEAST CALIFORNIA. MINIMUM HUMIDITY
LEVELS ALSO BOTTOM OUT IN THE SINGLE DIGITS...PRESENTING AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...MEYERS
FIRE WEATHER...MEYERS






000
FXUS65 KPSR 180941
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
240 AM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA STARTING TODAY
BRINGING EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED
CHANCES FOR SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH
TONIGHT...ANY RAINFALL WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN
LOCATIONS...WITH SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS
CENTRAL AND EASTERN ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY
WILL FALL TO MORE SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS..DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

THROUGH 17Z FRI...BKN CLDS AOA 25 THSD MSL. LIGHT WIND UNDER 9
KNOTS. FROM 17Z FRI TO 23Z FRI...THICKENING AND LOWERING CLOUDS
BECOMING BKN 10 THSD AGL BY 19Z. AN INCREASING CHANCE OF SHOWERS AND
ISOLATED THUNDERSTORMS. INCREASING SOUTHWEST WIND 5 TO 15 KNOTS...
BUT GUSTY AND ERRATIC NEAR THUNDERSTORM DOWNBURSTS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 16Z FRI...BKN CLDS AOA 25 THSD MSL. LIGHT SOUTH WIND 5 TO 10
KNOTS. FROM 16Z FRI TO 23Z FRI...THICKENING AND LOWERING CLDS
BECOMING BKN 12 THSD AGL BY 18Z. A SLIGHT CHANCE OF SHOWERS AND
ISOLATED THUNDERSTORMS. INCREASING SOUTH TO SOUTHWEST WIND 5 TO 15
KNOTS...HOWEVER BECOMING ERRATIC AND GUSTY NEAR TSTM DOWNBURSTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...VASQUEZ
FIRE WEATHER...HIRSCH







000
FXUS65 KPSR 180941
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
240 AM MST FRI APR 18 2014

.SYNOPSIS...
A PACIFIC STORM SYSTEM WILL MOVE INTO THE AREA STARTING TODAY
BRINGING EXTENSIVE CLOUDS...INCREASING MOISTURE AND LOCALIZED
CHANCES FOR SHOWERS THROUGH SATURDAY AFTERNOON. THROUGH
TONIGHT...ANY RAINFALL WILL BE FOCUSED MAINLY OVER HIGHER TERRAIN
LOCATIONS...WITH SPRINKLES MORE LIKELY ACROSS THE DESERTS. BETTER
CHANCES FOR SHOWERS AND THUNDERSTORMS WILL OCCUR ON SATURDAY ACROSS
CENTRAL AND EASTERN ARIZONA. DAYTIME TEMPERATURES TODAY AND SATURDAY
WILL FALL TO MORE SEASONAL VALUES...HOWEVER QUICKLY WARM BACK WELL
INTO THE 90S EARLY NEXT WEEK AFTER THE STORM SYSTEM HAS PASSED.

&&

.DISCUSSION...
A SEASONABLY VIGOROUS SHORTWAVE TROUGH HAS PROGRESSED TO NEAR THE
121W LATITUDE EARLY THIS MORNING...WITH THE SMALL PV ANOMALY CORE
TUCKED IN THE BASAL PORTION OF THE WAVE AROUND 25N. OBJECTIVE
ANALYSIS SUGGESTS A -16C TO -18C H5 COLD CORE REMAINS SITUATED IN
THE UPSTREAM NLY FLOW QUADRANT...WITH THE EASTERN SECTION OF THE
WAVE STRUCTURE CHARACTERIZED BY DEEP MERIDIONAL WARM MOIST
ADVECTION. THIS CONFIGURATION MAY MEAN FURTHER DEEPENING AND FUTURE
NEGATIVE TILT EJECTION OF THE WAVE INTO THE FORECAST AREA. JET
DIFLUENCE AHEAD OF THE WAVE LOOKS IMPRESSIVE ON WV IMAGERY PARTIALLY
TAPPING A NARROW PLUME OF SUBTROPICAL MOISTURE AND BECOMING
MANIFESTED IN A BAROCLINIC LEAF TYPE STRUCTURE (FURTHER EVIDENCE OF
THE POTENCY OF THIS SYSTEM).

WITH MOIST MERIDIONAL FLOW AND UVV IN THE 600-400MB LAYER ALREADY
ESTABLISHED AHEAD OF THE WAVE...THICKER CLOUD COVER WILL HOLD OVER
THE REGION TODAY. BOTH GOES AND AMSU TOTAL PWAT ANALYSIS SHOW A
CORRIDOR OF 1.0 INCH AMOUNTS ADVECTING TOWARDS THE FORECAST AREA
ORIGINATING WEST OF THE BAJA CORRIDOR. FORECAST SOUNDINGS SUGGEST
MUCH OF THIS MOISTURE IS EITHER ALOFT ABOVE THE H7 LAYER...OR VERY
SHALLOW BELOW THE H9 LAYER WITH NOTABLE DRY AIR TRAPPED BETWEEN. IN
ADDITION...WITH THE INTRODUCTION OF THIS MOISTURE...MIDLEVEL LAPSE
RATES WILL SUFFER LIMITING ANY INSTABILITY BASED AID TOWARDS DEEPER
VERTICAL MOTIONS. THUS..DESPITE THE ROBUST SYNOPTIC SCALE ASCENT
THROUGHOUT THE DAY IN ASSOCIATION WITH VORTICITY ADVECTION...MUCH OF
THE HYDROMETEORS MAY BE LOST AS VIRGA. EXCEPTIONS TO THIS ANALYSIS
MAY BE ACROSS SERN CALIFORNIA WHERE THE COLD CORE ALOFT WILL BEGIN
TO INTERACT WITH THE HEATED SFC ALLOWING BETTER INSTABILITY LATE IN
THE AFTERNOON...AND OVER HIGH TERRAIN NORTHEAST OF PHOENIX WHERE THE
SUBCLOUD DRY LAYER WILL BE NATURALLY REDUCED BY ELEVATION.
REGARDLESS...WITH THE PRESENCE OF EXTENSIVE VIRGA AND VERTICAL
MOTIONS THROUGHOUT THE COLUMN...GUSTY OUTFLOW WINDS REMAIN A CONCERN
THROUGHOUT THE AREA DURING THE DAYLIGHT HOURS.

FRIDAY NIGHT THOUGH SATURDAY AFTERNOON...THE COLD CORE ALOFT PULLS
TO THE EAST OF THE SHORTWAVE AND BECOMES BETTER ALIGNED WITH THE PV
ANOMALY AS THE BULK OF THE ENTIRE WAVE LIFTS AND EJECTS OVER
ARIZONA. DURING THIS TRANSITION...RENEWED VORTICITY ADVECTION AND
ASCENT WILL ROTATE THROUGH THE TROUGH WHILE LAPSE RATES STEEPEN IN
THE PRESENCE OF RESIDUAL MOISTURE. A FEW HIGH RESOLUTION MODELS AND
SREF PROBABILITIES SUGGEST THE FIRST WAVE OF UVV/SHOWERS ROTATING
NORTH INTO CNTRL ARIZONA AS EARLY AS SUNRISE SATURDAY. SFC HEATING
UNDER THE COLD CORE DURING THE DAY MAY VERY WELL LEAD TO SUBSTANTIAL
INSTABILITY (SBCAPE AOA 250 J/KG AND LI/S AOB -2)...ESPECIALLY OVER
HIGHER TERRAIN. CONCEPTUALLY AND EVIDENTIALLY THROUGH MODEL
OUTPUT...POPS WERE INCREASED SIGNIFICANTLY FOR POINTS EAST OF
PHOENIX SATURDAY AFTERNOON.

THE AFOREMENTIONED WAVE WILL RAPIDLY WEAKEN AND LIFT INTO THE CNTRL
ROCKIES/PLAINS ON SUNDAY...ALLOWING RIDGING TO QUICKLY REBUILD OVER
THE FORECAST AREA. H5 HEIGHTS AOA 582DM WILL BECOME MAXIMIZED ON
MONDAY AFTERNOON YIELDING HIGHS IN THE MID/UPPER 90S FOR LOWER
ELEVATION LOCATIONS. THE NEXT PROGRESSIVE PACIFIC WAVE WILL MOVE
ONSHORE TUESDAY AFTERNOON...THOUGH MODEL OUTPUT AND TRENDS KEEP THE
VAST MAJORITY OF JET ENERGY AND MOISTURE FROM CNTRL CALIFORNIA
NORTHWARD. IF ANYTHING...THE FORWARD SPEED AND ARRIVAL INTO THE WRN
CONUS MAY BE A BIT SLOWER...AND HAVE DELAYED THE LOCAL ONSET OF
FROPA AND COOLING TO BEYOND TUESDAY. THE GREATEST IMPACT OF THIS
SYSTEM FOR ARIZONA MAY BE GUSTY WINDS ALONG AND IMMEDIATELY BEHIND
THE FRONTAL BOUNDARY AS THE PRESSURE GRADIENT TIGHTENS TUESDAY
AFTERNOON AND EVENING. SOUTHEAST CALIFORNIA AND THE LOWER COLORADO
RIVER VALLEY WOULD LIKELY EXPERIENCE THE MOST PROLONGED AND FREQUENT
HIGHER GUSTS.

WHILE HEIGHTS ALOFT WILL BE TEMPERED BACK INTO A 570-576DM RANGE FOR
THE REMAINDER OF THE WEEK UNDER QUASI-ZONAL FLOW...FEEL THE NET
EFFECT ON TEMPERATURES WILL ONLY BE LIMITED TO KEEPING DAILY
READINGS NEAR CLIMATOLOGY. ENSEMBLE SPREAD IS RELATIVELY LOW IN THE
DAY 5-8 RANGE...SO FORECAST CONFIDENCE IS SOMEWHAT HIGHER THAN
AVERAGE. AT THIS TIME...PRECIPITATION CHANCES APPEAR ALMOST
NON-EXISTENT FOR PRETTY MUCH THE ENTIRETY OF NEXT WEEK.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

THROUGH 17Z FRI...BKN CLDS AOA 25 THSD MSL. LIGHT WIND UNDER 9
KNOTS. FROM 17Z FRI TO 23Z FRI...THICKENING AND LOWERING CLOUDS
BECOMING BKN 10 THSD AGL BY 19Z. AN INCREASING CHANCE OF SHOWERS AND
ISOLATED THUNDERSTORMS. INCREASING SOUTHWEST WIND 5 TO 15 KNOTS...
BUT GUSTY AND ERRATIC NEAR THUNDERSTORM DOWNBURSTS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 16Z FRI...BKN CLDS AOA 25 THSD MSL. LIGHT SOUTH WIND 5 TO 10
KNOTS. FROM 16Z FRI TO 23Z FRI...THICKENING AND LOWERING CLDS
BECOMING BKN 12 THSD AGL BY 18Z. A SLIGHT CHANCE OF SHOWERS AND
ISOLATED THUNDERSTORMS. INCREASING SOUTH TO SOUTHWEST WIND 5 TO 15
KNOTS...HOWEVER BECOMING ERRATIC AND GUSTY NEAR TSTM DOWNBURSTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...MO
AVIATION...VASQUEZ
FIRE WEATHER...HIRSCH








000
FXUS65 KPSR 180310
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
810 PM MST THU APR 17 2014

.SYNOPSIS...
A PACIFIC STORM WILL MOVE INTO THE AREA STARTING TONIGHT BRINGING
INCREASING MOISTURE AND CLOUDS. BY FRIDAY AFTERNOON THIS SYSTEM WILL
SUPPORT SLIGHT CHANCES FOR SHOWERS FROM THE COLORADO RIVER EAST
ACROSS SOUTH CENTRAL ARIZONA AND INTO THE HIGHER TERRAIN. DAYTIME
TEMPERATURES FOR FRIDAY AND SATURDAY WILL FALL TO MORE SEASONAL
VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE EAST ON
SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR EARLY NEXT
WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
CONSIDERABLE HIGH CLOUDS WERE BEGINNING TO STREAM INTO THE REGION
FROM THE WEST THIS EVENING...ASSOCIATED WITH THE APPROACHING PACIFIC
TROF. MODELS CONTINUE TO MOVE THIS SYSTEM INTO ARIZONA LATE FRIDAY
FRIDAY THROUGH SATURDAY NIGHT AND IS A CONCERN. A SYSTEM AS
DYNAMICAL AS THIS...MOVING OVER A VERY WARM AFTERNOON BOUNDARY LAYER
ALWAYS HAS POTENTIAL FOR GREAT INSTABILITY...INCLUDING THUNDERSTORMS
IF MOISTURE IS AVAILABLE. EVEN ONLY MID LEVEL MOISTURE OVER A VERY
DRY BOUNDARY LAYER COULD GENERATE HIGH BASED SHOWERS/STORMS
RESULTING IN STRONG DOWNBURST WINDS AND AREAS OF BLOWING DUST ON THE
DESERTS.

AFTER REVIEWING THIS EVENINGS COASTAL WEATHER BALLOON SOUNDINGS
THIS SYSTEM WAS STILL TOO FAR WEST TO MEASURE ANY APPRECIABLE
MOISTURE. HOWEVER...UPPER LEVEL STREAMLINES DRAWN FROM 00Z VAPOR
IMAGERY LOOPS SHOW HIGHLY DIFLUENT FLOW ALOFT JUST OFF THE SOUTHERN
CA/NORTHERN BAJA COASTS...INDICATING INCREASING VERTICAL MOTION. AND
UNDER THIS DIFLUENT FIELD...OFFSHORE PRECIP WATER AMOUNTS CONTINUED
TO GROW WITH EVERY PASSING HOUR...I.E. A LARGE FIELD OF 0.75 TO 0.90
INCHES WITH EXPANDING AREAS OF 1.05 INCHES.

SUPPOSING AN INCREASED MOISTURE FIELD WITH A DYNAMICAL SYSTEM...
INCLUDING WARM DESERT TEMPERATURES...AN ARGUMENT CAN BE MADE FOR
EXPANDING A SHWR/TSTM THREAT OVER A LARGE AREA SOUTHWEST AND SOUTH
CENTRAL AZ. UPDATED FORECASTS...INCLUDING A HAZARDOUS WEATHER
OUTLOOK...WERE SENT EARLIER TO REFLECT THIS.

ON SATURDAY THE UPPER LEVEL COLD POOL WITH CONSIDERABLE MID LEVEL
MOISTURE CIRCULATING AROUND THE LOW CENTER SHOULD CONTINUE A THREAT
FOR SHOWERS AND THUNDERSTORMS INTO SATURDAY EVENING.

PREVIOUS DISCUSSION...213 PM MST...
AS THE LOW APPROACHES THE DESERT SOUTHWEST TONIGHT...EXPECT CLOUDS
TO THICKEN FROM THE SOUTHWEST TO THE NORTHEAST LATE TONIGHT INTO
FRIDAY MORNING. SKIES WILL LIKELY BECOME MOSTLY CLOUDY AND POSSIBLY
CLOUDY AT TIMES DURING MUCH OF THE DAYTIME HOURS FRIDAY. MODELS SHOW
WEAK TO MODERATE DIFLUENCE ALOFT AND SUFFICIENT OMEGA IN A NEAR
SATURATED 600-400MB LAYER STARTING FRIDAY MORNING. AM EXPECTING SOME
HIGH BASED...12-15K FEET...SHOWERS TO DEVELOP SOMETIME FRIDAY
MORNING INTO EARLY FRIDAY AFTERNOON...ESPECIALLY ALONG AND JUST
BEHIND THE LEADING EDGE OF THE MID LEVEL MOISTURE PLUME. SINCE THE
SUB-CLOUD LAYER WILL BE DRY...NOT QUITE BONE DRY...NOT EXPECTING TOO
MANY LOCATIONS TO SEE RAIN HITTING THE GROUND...MAINLY HIGHER
TERRAIN LOCALES.

CHANCES INCREASE FRIDAY AFTERNOON AND EARLY FRIDAY EVENING...BUT
OVERALL COVERAGE WILL BE LIMITED AND POPS STILL ONLY IN THE SLIGHT
CHANCE CATEGORY AND MAINLY COVERING THE HIGHER TERRAIN. THE WARM AND
DRY SUB-CLOUD LAYERS MAY BRING THE POTENTIAL FOR GUSTY WINDS AND
OUTFLOWS IF A STORM GETS ORGANIZED ENOUGH. THE MAIN UPPER LOW
CIRCULATION WILL HANG BACK ACROSS SOUTHEAST CALIFORNIA FRIDAY
AFTERNOON...THEN SLOWLY PROGRESSING INTO CENTRAL ARIZONA DURING THE
DAY SATURDAY. SLIGHT CHANCE POPS WILL REMAIN THROUGH FRIDAY NIGHT
INTO SATURDAY EVENING ACROSS SOUTH-CENTRAL ARIZONA WITH CHANCE POPS
ACROSS THE HIGHER TERRAIN IN GILA COUNTY. QPF AMOUNTS FOR THE ENTIRE
EVENT WILL BE NEAR ZERO ACROSS THE LOWER DESERTS TO AROUND A TENTH
OF AN INCH ACROSS GILA COUNTY.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...

THROUGH 17Z FRI...BKN CLDS AOA 25 THSD MSL. LIGHT WIND UNDER 9
KNOTS. FROM 17Z FRI TO 23Z FRI...THICKENING AND LOWERING CLOUDS
BECOMING BKN 10 THSD AGL BY 19Z. AN INCREASING CHANCE OF SHOWERS AND
ISOLATED THUNDERSTORMS. INCREASING SOUTHWEST WIND 5 TO 15 KNOTS...
BUT GUSTY AND ERRATIC NEAR THUNDERSTORM DOWNBURSTS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
THROUGH 16Z FRI...BKN CLDS AOA 25 THSD MSL. LIGHT SOUTH WIND 5 TO 10
KNOTS. FROM 16Z FRI TO 23Z FRI...THICKENING AND LOWERING CLDS
BECOMING BKN 12 THSD AGL BY 18Z. A SLIGHT CHANCE OF SHOWERS AND
ISOLATED THUNDERSTORMS. INCREASING SOUTH TO SOUTHWEST WIND 5 TO 15
KNOTS...HOWEVER BECOMING ERRATIC AND GUSTY NEAR TSTM DOWNBURSTS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...VASQUEZ/KUHLMAN/NOLTE
AVIATION...VASQUEZ
FIRE WEATHER...HIRSCH













000
FXUS65 KPSR 172113
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
213 PM MST THU APR 17 2014

.SYNOPSIS...
A PACIFIC STORM WILL MOVE INTO THE AREA STARTING TONIGHT BRINGING
INCREASING MOISTURE AND CLOUDS. BY FRIDAY AFTERNOON THIS SYSTEM WILL
SUPPORT SLIGHT CHANCES FOR SHOWERS FROM THE COLORADO RIVER EAST
ACROSS SOUTH CENTRAL ARIZONA AND INTO THE HIGHER TERRAIN. DAYTIME
TEMPERATURES FOR FRIDAY AND SATURDAY WILL FALL TO MORE SEASONAL
VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE EAST ON
SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR EARLY NEXT
WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
HIGH THIN CLOUDS ARE STARTING TO OVERSPREAD SOUTHEAST CALIFORNIA
INTO SOUTHWEST ARIZONA THIS AFTERNOON. CURRENT WATER VAPOR IMAGERY
AND OBJECTIVE ANALYSIS SHOWS AN UPPER LEVEL LOW CIRCULATION NEAR
31N/124W WITH EXTENSIVE MOISTURE AHEAD OF THE LOW AND SOME
SUB-TROPICAL MOISTURE WRAPPING INTO THE LOW FROM THE SOUTHWEST. AS
THE LOW APPROACHES THE DESERT SOUTHWEST TONIGHT...EXPECT CLOUDS TO
THICKEN FROM THE SOUTHWEST TO THE NORTHEAST LATE TONIGHT INTO FRIDAY
MORNING. SKIES WILL LIKELY BECOME MOSTLY CLOUDY AND POSSIBLY CLOUDY
AT TIMES DURING MUCH OF THE DAYTIME HOURS FRIDAY. MODELS SHOW WEAK
TO MODERATE DIFLUENCE ALOFT AND SUFFICIENT OMEGA IN A NEAR
SATURATED 600-400MB LAYER STARTING FRIDAY MORNING. AM EXPECTING SOME
HIGH BASED...12-15K FEET...SHOWERS TO DEVELOP SOMETIME FRIDAY
MORNING INTO EARLY FRIDAY AFTERNOON...ESPECIALLY ALONG AND JUST
BEHIND THE LEADING EDGE OF THE MID LEVEL MOISTURE PLUME. SINCE THE
SUB-CLOUD LAYER WILL BE DRY...NOT QUITE BONE DRY...NOT EXPECTING TOO
MANY LOCATIONS TO SEE RAIN HITTING THE GROUND...MAINLY HIGHER
TERRAIN LOCALES.

CHANCES INCREASE FRIDAY AFTERNOON AND EARLY FRIDAY EVENING...BUT
OVERALL COVERAGE WILL BE LIMITED AND POPS STILL ONLY IN THE SLIGHT
CHANCE CATEGORY AND MAINLY COVERING THE HIGHER TERRAIN. THE WARM AND
DRY SUB-CLOUD LAYERS MAY BRING THE POTENTIAL FOR GUSTY WINDS AND
OUTFLOWS IF A STORM GETS ORGANIZED ENOUGH. THE MAIN UPPER LOW
CIRCULATION WILL HANG BACK ACROSS SOUTHEAST CALIFORNIA FRIDAY
AFTERNOON...THEN SLOWLY PROGRESSING INTO CENTRAL ARIZONA DURING THE
DAY SATURDAY. SLIGHT CHANCE POPS WILL REMAIN THROUGH FRIDAY NIGHT
INTO SATURDAY EVENING ACROSS SOUTH-CENTRAL ARIZONA WITH CHANCE POPS
ACROSS THE HIGHER TERRAIN IN GILA COUNTY. QPF AMOUNTS FOR THE ENTIRE
EVENT WILL BE NEAR ZERO ACROSS THE LOWER DESERTS TO AROUND A TENTH
OF AN INCH ACROSS GILA COUNTY.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A GRADUAL INCREASE IN MID AND HIGH CLOUDS IS EXPECTED OVER THE NEXT
24 HOURS AHEAD OF A LOW PRESSURE SYSTEM. WITH THE LOW IN OUR
VICINITY...WINDS WILL ALSO RETAIN MORE OF A SOUTHERLY COMPONENT
THROUGH FRIDAY AFTERNOON. HOWEVER...THROUGH 18Z FRIDAY...WINDS WILL
REMAIN DIURNAL AND GENERALLY LESS THAN 10 KT. GIVEN THE DRY
CONDITIONS NEAR THE SURFACE...THERE ALSO IS THE POTENTIAL FOR VIRGA
PRODUCING LOCALIZED DOWNBURST WINDS...PERHAPS AS EARLY AS FRIDAY
MORNING BUT MORE LIKELY FRIDAY AFTERNOON.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHERLY WINDS WILL BE THE PRIMARY AVIATION WEATHER IMPACT...WITH
OCCASIONAL GUSTS TO AROUND 20 KT THIS AFTERNOON. WINDS WILL ABATE
OVERNIGHT BEFORE INCREASING AGAIN FRIDAY AFTERNOON AHEAD OF A LOW
PRESSURE SYSTEM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN/NOLTE
AVIATION...HIRSCH
FIRE WEATHER...HIRSCH









000
FXUS65 KPSR 171948
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1250 PM MST THU APR 17 2014

.UPDATE...UPDATED FIRE WEATHER DISCUSSION.

&&

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE
EAST ON SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR
NEXT WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL HEIGHT ANALYSIS CURRENTLY SHOWS A RIDGE AXIS MOVING INTO
OUR REGION FROM THE WEST AND FORECAST TO PASS TO OUR EAST BY
MIDNIGHT TONIGHT. GIVEN THE CLEAR SKIES ACROSS ARIZONA...AND
INCREASING THIN CLOUDS ACROSS WESTERN CALIFORNIA AHEAD OF A PACIFIC
LOW...WE SHOULD EXPECT SIMILAR HIGHS TODAY COMPARED TO YESTERDAY.
A COUPLE DEGREE PULLBACK ACROSS SOUTHEAST CALIFORNIA IS
LIKELY DUE TO THE INCREASING HIGH CLOUDS THIS AFTERNOON. THESE HIGH
CLOUDS ARE A PRECURSOR TO THE SMALL AND COMPACT SHORTWAVE TROUGH
THAT WILL AFFECT OUR REGION FRIDAY AND SATURDAY. OVERALL...THIS
PACIFIC SYSTEM WILL BE MOISTURE STARVED BELOW 10K FEET...BUT AMPLE
MID LEVEL MOISTURE AND SUFFICIENT UPPER DYNAMICS SHOULD RESULT IN
VIRGA SHOWERS AND ISOLATED SPRINKLES ACROSS THE LOWER DESERTS AND
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS STARTING LATE FRIDAY
MORNING OR EARLY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A GRADUAL INCREASE IN MID AND HIGH CLOUDS IS EXPECTED OVER THE NEXT
24 HOURS AHEAD OF A LOW PRESSURE SYSTEM. WITH THE LOW IN OUR
VICINITY...WINDS WILL ALSO RETAIN MORE OF A SOUTHERLY COMPONENT
THROUGH FRIDAY AFTERNOON. HOWEVER...THROUGH 18Z FRIDAY...WINDS WILL
REMAIN DIURNAL AND GENERALLY LESS THAN 10 KT. GIVEN THE DRY
CONDITIONS NEAR THE SURFACE...THERE ALSO IS THE POTENTIAL FOR VIRGA
PRODUCING LOCALIZED DOWNBURST WINDS...PERHAPS AS EARLY AS FRIDAY
MORNING BUT MORE LIKELY FRIDAY AFTERNOON.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHERLY WINDS WILL BE THE PRIMARY AVIATION WEATHER IMPACT...WITH
OCCASIONAL GUSTS TO AROUND 20 KT THIS AFTERNOON. WINDS WILL ABATE
OVERNIGHT BEFORE INCREASING AGAIN FRIDAY AFTERNOON AHEAD OF A LOW
PRESSURE SYSTEM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...NOLTE
AVIATION...HIRSCH
FIRE WEATHER...HIRSCH







000
FXUS65 KPSR 171948
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1250 PM MST THU APR 17 2014

.UPDATE...UPDATED FIRE WEATHER DISCUSSION.

&&

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE
EAST ON SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR
NEXT WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL HEIGHT ANALYSIS CURRENTLY SHOWS A RIDGE AXIS MOVING INTO
OUR REGION FROM THE WEST AND FORECAST TO PASS TO OUR EAST BY
MIDNIGHT TONIGHT. GIVEN THE CLEAR SKIES ACROSS ARIZONA...AND
INCREASING THIN CLOUDS ACROSS WESTERN CALIFORNIA AHEAD OF A PACIFIC
LOW...WE SHOULD EXPECT SIMILAR HIGHS TODAY COMPARED TO YESTERDAY.
A COUPLE DEGREE PULLBACK ACROSS SOUTHEAST CALIFORNIA IS
LIKELY DUE TO THE INCREASING HIGH CLOUDS THIS AFTERNOON. THESE HIGH
CLOUDS ARE A PRECURSOR TO THE SMALL AND COMPACT SHORTWAVE TROUGH
THAT WILL AFFECT OUR REGION FRIDAY AND SATURDAY. OVERALL...THIS
PACIFIC SYSTEM WILL BE MOISTURE STARVED BELOW 10K FEET...BUT AMPLE
MID LEVEL MOISTURE AND SUFFICIENT UPPER DYNAMICS SHOULD RESULT IN
VIRGA SHOWERS AND ISOLATED SPRINKLES ACROSS THE LOWER DESERTS AND
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS STARTING LATE FRIDAY
MORNING OR EARLY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A GRADUAL INCREASE IN MID AND HIGH CLOUDS IS EXPECTED OVER THE NEXT
24 HOURS AHEAD OF A LOW PRESSURE SYSTEM. WITH THE LOW IN OUR
VICINITY...WINDS WILL ALSO RETAIN MORE OF A SOUTHERLY COMPONENT
THROUGH FRIDAY AFTERNOON. HOWEVER...THROUGH 18Z FRIDAY...WINDS WILL
REMAIN DIURNAL AND GENERALLY LESS THAN 10 KT. GIVEN THE DRY
CONDITIONS NEAR THE SURFACE...THERE ALSO IS THE POTENTIAL FOR VIRGA
PRODUCING LOCALIZED DOWNBURST WINDS...PERHAPS AS EARLY AS FRIDAY
MORNING BUT MORE LIKELY FRIDAY AFTERNOON.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHERLY WINDS WILL BE THE PRIMARY AVIATION WEATHER IMPACT...WITH
OCCASIONAL GUSTS TO AROUND 20 KT THIS AFTERNOON. WINDS WILL ABATE
OVERNIGHT BEFORE INCREASING AGAIN FRIDAY AFTERNOON AHEAD OF A LOW
PRESSURE SYSTEM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SUNDAY THROUGH THURSDAY...
WESTERLY FLOW WILL BRING A WARMING AND DRYING TREND TO THE REGION
THROUGH TUESDAY. THEREAFTER...A COOLING TREND IS EXPECTED AS AN AREA
OF LOW PRESSURE MOVES THROUGH THE WESTERN STATES. THE BIGGEST IMPACT
WITH THIS SYSTEM WILL BE AN INCREASE IN WIND...PARTICULARLY ON
WEDNESDAY. LOW RHS DURING THE MIDWEEK PERIOD WILL ALSO PRESENT AN
INCREASED FIRE DANGER THREAT.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...NOLTE
AVIATION...HIRSCH
FIRE WEATHER...HIRSCH






000
FXUS65 KPSR 171825
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1125 AM MST THU APR 17 2014

.UPDATE...UPDATED AVIATION DISCUSSION.

&&

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE
EAST ON SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR
NEXT WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL HEIGHT ANALYSIS CURRENTLY SHOWS A RIDGE AXIS MOVING INTO
OUR REGION FROM THE WEST AND FORECAST TO PASS TO OUR EAST BY
MIDNIGHT TONIGHT. GIVEN THE CLEAR SKIES ACROSS ARIZONA...AND
INCREASING THIN CLOUDS ACROSS WESTERN CALIFORNIA AHEAD OF A PACIFIC
LOW...WE SHOULD EXPECT SIMILAR HIGHS TODAY COMPARED TO YESTERDAY.
A COUPLE DEGREE PULLBACK ACROSS SOUTHEAST CALIFORNIA IS
LIKELY DUE TO THE INCREASING HIGH CLOUDS THIS AFTERNOON. THESE HIGH
CLOUDS ARE A PRECURSOR TO THE SMALL AND COMPACT SHORTWAVE TROUGH
THAT WILL AFFECT OUR REGION FRIDAY AND SATURDAY. OVERALL...THIS
PACIFIC SYSTEM WILL BE MOISTURE STARVED BELOW 10K FEET...BUT AMPLE
MID LEVEL MOISTURE AND SUFFICIENT UPPER DYNAMICS SHOULD RESULT IN
VIRGA SHOWERS AND ISOLATED SPRINKLES ACROSS THE LOWER DESERTS AND
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS STARTING LATE FRIDAY
MORNING OR EARLY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A GRADUAL INCREASE IN MID AND HIGH CLOUDS IS EXPECTED OVER THE NEXT
24 HOURS AHEAD OF A LOW PRESSURE SYSTEM. WITH THE LOW IN OUR
VICINITY...WINDS WILL ALSO RETAIN MORE OF A SOUTHERLY COMPONENT
THROUGH FRIDAY AFTERNOON. HOWEVER...THROUGH 18Z FRIDAY...WINDS WILL
REMAIN DIURNAL AND GENERALLY LESS THAN 10 KT. GIVEN THE DRY
CONDITIONS NEAR THE SURFACE...THERE ALSO IS THE POTENTIAL FOR VIRGA
PRODUCING LOCALIZED DOWNBURST WINDS...PERHAPS AS EARLY AS FRIDAY
MORNING BUT MORE LIKELY FRIDAY AFTERNOON.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHERLY WINDS WILL BE THE PRIMARY AVIATION WEATHER IMPACT...WITH
OCCASIONAL GUSTS TO AROUND 20 KT THIS AFTERNOON. WINDS WILL ABATE
OVERNIGHT BEFORE INCREASING AGAIN FRIDAY AFTERNOON AHEAD OF A LOW
PRESSURE SYSTEM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...NOLTE
AVIATION...HIRSCH
FIRE WEATHER...VASQUEZ/LEINS







000
FXUS65 KPSR 171825
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1125 AM MST THU APR 17 2014

.UPDATE...UPDATED AVIATION DISCUSSION.

&&

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE
EAST ON SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR
NEXT WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL HEIGHT ANALYSIS CURRENTLY SHOWS A RIDGE AXIS MOVING INTO
OUR REGION FROM THE WEST AND FORECAST TO PASS TO OUR EAST BY
MIDNIGHT TONIGHT. GIVEN THE CLEAR SKIES ACROSS ARIZONA...AND
INCREASING THIN CLOUDS ACROSS WESTERN CALIFORNIA AHEAD OF A PACIFIC
LOW...WE SHOULD EXPECT SIMILAR HIGHS TODAY COMPARED TO YESTERDAY.
A COUPLE DEGREE PULLBACK ACROSS SOUTHEAST CALIFORNIA IS
LIKELY DUE TO THE INCREASING HIGH CLOUDS THIS AFTERNOON. THESE HIGH
CLOUDS ARE A PRECURSOR TO THE SMALL AND COMPACT SHORTWAVE TROUGH
THAT WILL AFFECT OUR REGION FRIDAY AND SATURDAY. OVERALL...THIS
PACIFIC SYSTEM WILL BE MOISTURE STARVED BELOW 10K FEET...BUT AMPLE
MID LEVEL MOISTURE AND SUFFICIENT UPPER DYNAMICS SHOULD RESULT IN
VIRGA SHOWERS AND ISOLATED SPRINKLES ACROSS THE LOWER DESERTS AND
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS STARTING LATE FRIDAY
MORNING OR EARLY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
A GRADUAL INCREASE IN MID AND HIGH CLOUDS IS EXPECTED OVER THE NEXT
24 HOURS AHEAD OF A LOW PRESSURE SYSTEM. WITH THE LOW IN OUR
VICINITY...WINDS WILL ALSO RETAIN MORE OF A SOUTHERLY COMPONENT
THROUGH FRIDAY AFTERNOON. HOWEVER...THROUGH 18Z FRIDAY...WINDS WILL
REMAIN DIURNAL AND GENERALLY LESS THAN 10 KT. GIVEN THE DRY
CONDITIONS NEAR THE SURFACE...THERE ALSO IS THE POTENTIAL FOR VIRGA
PRODUCING LOCALIZED DOWNBURST WINDS...PERHAPS AS EARLY AS FRIDAY
MORNING BUT MORE LIKELY FRIDAY AFTERNOON.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHERLY WINDS WILL BE THE PRIMARY AVIATION WEATHER IMPACT...WITH
OCCASIONAL GUSTS TO AROUND 20 KT THIS AFTERNOON. WINDS WILL ABATE
OVERNIGHT BEFORE INCREASING AGAIN FRIDAY AFTERNOON AHEAD OF A LOW
PRESSURE SYSTEM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...KUHLMAN
PREVIOUS DISCUSSION...NOLTE
AVIATION...HIRSCH
FIRE WEATHER...VASQUEZ/LEINS






000
FXUS65 KPSR 171603
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
903 AM MST THU APR 17 2014

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE
EAST ON SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR
NEXT WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL HEIGHT ANALYSIS CURRENTLY SHOWS A RIDGE AXIS MOVING INTO
OUR REGION FROM THE WEST AND FORECAST TO PASS TO OUR EAST BY
MIDNIGHT TONIGHT. GIVEN THE CLEAR SKIES ACROSS ARIZONA...AND
INCREASING THIN CLOUDS ACROSS WESTERN CALIFORNIA AHEAD OF A PACIFIC
LOW...WE SHOULD EXPECT SIMILAR HIGHS TODAY COMPARED TO YESTERDAY.
A COUPLE DEGREE PULLBACK ACROSS SOUTHEAST CALIFORNIA IS
LIKELY DUE TO THE INCREASING HIGH CLOUDS THIS AFTERNOON. THESE HIGH
CLOUDS ARE A PRECURSOR TO THE SMALL AND COMPACT SHORTWAVE TROUGH
THAT WILL AFFECT OUR REGION FRIDAY AND SATURDAY. OVERALL...THIS
PACIFIC SYSTEM WILL BE MOISTURE STARVED BELOW 10K FEET...BUT AMPLE
MID LEVEL MOISTURE AND SUFFICIENT UPPER DYNAMICS SHOULD RESULT IN
VIRGA SHOWERS AND ISOLATED SPRINKLES ACROSS THE LOWER DESERTS AND
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS STARTING LATE FRIDAY
MORNING OR EARLY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
HIGH CLOUDS WILL INCREASE THROUGH THE DAY BUT SHOULD BE OF LITTLE
AVIATION IMPACT. WINDS WILL BE LIGHT AND WILL FOLLOW TYPICAL DIURNAL
DIRECTIONS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH CLOUDS WILL STEADILY INCREASE THROUGH THE DAY BUT LOWER CIGS
SHOULD HOLD OFF UNTIL LATE FRIDAY MORNING. WINDS WILL INCREASE THIS
AFTERNOON AND COULD BE GUSTY AT TIMES /AROUND 20KTS/ BUT SHOULD
DECREASE AFTER 00-02Z.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

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










000
FXUS65 KPSR 171603
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
903 AM MST THU APR 17 2014

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES. AFTER THE STORM AND CLOUDS MOVE TO THE
EAST ON SUNDAY...TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR
NEXT WEEK WITH MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UPPER LEVEL HEIGHT ANALYSIS CURRENTLY SHOWS A RIDGE AXIS MOVING INTO
OUR REGION FROM THE WEST AND FORECAST TO PASS TO OUR EAST BY
MIDNIGHT TONIGHT. GIVEN THE CLEAR SKIES ACROSS ARIZONA...AND
INCREASING THIN CLOUDS ACROSS WESTERN CALIFORNIA AHEAD OF A PACIFIC
LOW...WE SHOULD EXPECT SIMILAR HIGHS TODAY COMPARED TO YESTERDAY.
A COUPLE DEGREE PULLBACK ACROSS SOUTHEAST CALIFORNIA IS
LIKELY DUE TO THE INCREASING HIGH CLOUDS THIS AFTERNOON. THESE HIGH
CLOUDS ARE A PRECURSOR TO THE SMALL AND COMPACT SHORTWAVE TROUGH
THAT WILL AFFECT OUR REGION FRIDAY AND SATURDAY. OVERALL...THIS
PACIFIC SYSTEM WILL BE MOISTURE STARVED BELOW 10K FEET...BUT AMPLE
MID LEVEL MOISTURE AND SUFFICIENT UPPER DYNAMICS SHOULD RESULT IN
VIRGA SHOWERS AND ISOLATED SPRINKLES ACROSS THE LOWER DESERTS AND
LIGHT SHOWERS ACROSS HIGHER TERRAIN AREAS STARTING LATE FRIDAY
MORNING OR EARLY AFTERNOON.

&&

.PREVIOUS DISCUSSION...
PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
HIGH CLOUDS WILL INCREASE THROUGH THE DAY BUT SHOULD BE OF LITTLE
AVIATION IMPACT. WINDS WILL BE LIGHT AND WILL FOLLOW TYPICAL DIURNAL
DIRECTIONS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH CLOUDS WILL STEADILY INCREASE THROUGH THE DAY BUT LOWER CIGS
SHOULD HOLD OFF UNTIL LATE FRIDAY MORNING. WINDS WILL INCREASE THIS
AFTERNOON AND COULD BE GUSTY AT TIMES /AROUND 20KTS/ BUT SHOULD
DECREASE AFTER 00-02Z.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

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









000
FXUS65 KPSR 171127 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
427 AM MST THU APR 17 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS...

&&

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES WHILE THE STORM AND CLOUDS CLEAR TO THE
EAST. TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR NEXT WEEK WITH
MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UNDER CLEAR SKIES...TEMPERATURES THIS MORNING OVER THE FORECAST AREA
HAVE BEEN SLOWER TO COOL COMPARED TO YESTERDAY...WITH MID 60S TO LOW
70S IN THE LATEST 2AM OBS. TODAY`S TEMPERATURE FORECAST NEAR CARBON
COPY OF WEDNESDAY`S...WITH LOW TO MID 90S ACROSS THE DESERTS AND 80S
FOR THE FOOTHILL/HIGHER TERRAIN LOCALES. HIGH LEVEL CLOUDS WILL
GRADUALLY INCREASE FROM THE WEST THROUGH THE DAY...AHEAD OF A EAST
PACIFIC LOW MOVING ONSHORE.

PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
HIGH CLOUDS WILL INCREASE THROUGH THE DAY BUT SHOULD BE OF LITTLE
AVIATION IMPACT. WINDS WILL BE LIGHT AND WILL FOLLOW TYPICAL DIURNAL
DIRECTIONS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH CLOUDS WILL STEADILY INCREASE THROUGH THE DAY BUT LOWER CIGS
SHOULD HOLD OFF UNTIL LATE FRIDAY MORNING. WINDS WILL INCREASE THIS
AFTERNOON AND COULD BE GUSTY AT TIMES /AROUND 20KTS/ BUT SHOULD
DECREASE AFTER 00-02Z.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

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






000
FXUS65 KPSR 171127 AAA
AFDPSR

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
427 AM MST THU APR 17 2014

.UPDATE...UPDATED AVIATION AND FIRE WEATHER DISCUSSIONS...

&&

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES WHILE THE STORM AND CLOUDS CLEAR TO THE
EAST. TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR NEXT WEEK WITH
MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UNDER CLEAR SKIES...TEMPERATURES THIS MORNING OVER THE FORECAST AREA
HAVE BEEN SLOWER TO COOL COMPARED TO YESTERDAY...WITH MID 60S TO LOW
70S IN THE LATEST 2AM OBS. TODAY`S TEMPERATURE FORECAST NEAR CARBON
COPY OF WEDNESDAY`S...WITH LOW TO MID 90S ACROSS THE DESERTS AND 80S
FOR THE FOOTHILL/HIGHER TERRAIN LOCALES. HIGH LEVEL CLOUDS WILL
GRADUALLY INCREASE FROM THE WEST THROUGH THE DAY...AHEAD OF A EAST
PACIFIC LOW MOVING ONSHORE.

PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
HIGH CLOUDS WILL INCREASE THROUGH THE DAY BUT SHOULD BE OF LITTLE
AVIATION IMPACT. WINDS WILL BE LIGHT AND WILL FOLLOW TYPICAL DIURNAL
DIRECTIONS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
HIGH CLOUDS WILL STEADILY INCREASE THROUGH THE DAY BUT LOWER CIGS
SHOULD HOLD OFF UNTIL LATE FRIDAY MORNING. WINDS WILL INCREASE THIS
AFTERNOON AND COULD BE GUSTY AT TIMES /AROUND 20KTS/ BUT SHOULD
DECREASE AFTER 00-02Z.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

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







000
FXUS65 KPSR 170956
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
256 AM MST THU APR 17 2014

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES WHILE THE STORM AND CLOUDS CLEAR TO THE
EAST. TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR NEXT WEEK WITH
MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UNDER CLEAR SKIES...TEMPERATURES THIS MORNING OVER THE FORECAST AREA
HAVE BEEN SLOWER TO COOL COMPARED TO YESTERDAY...WITH MID 60S TO LOW
70S IN THE LATEST 2AM OBS. TODAY`S TEMPERATURE FORECAST NEAR CARBON
COPY OF WEDNESDAY`S...WITH LOW TO MID 90S ACROSS THE DESERTS AND 80S
FOR THE FOOTHILL/HIGHER TERRAIN LOCALES. HIGH LEVEL CLOUDS WILL
GRADUALLY INCREASE FROM THE WEST THROUGH THE DAY...AHEAD OF A EAST
PACIFIC LOW MOVING ONSHORE.

PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
WEAK WEATHER DISTURBANCE PASSING INTO NEW MEXICO TONIGHT. SURFACE
WINDS WILL BE LIGHT OVERNIGHT. HOWEVER...MODELS DEPICT WEST WINDS IN
THE LOW LEVELS ABOVE THE SURFACE INCREASING TO 20-25 KTS AROUND 2000
FT MSL BETWEEN 06-07Z AND DISSIPATING BY 09Z. THE INCREASE IN WEST
WINDS PROBABLY NOT QUITE ENOUGH TO INSERT LLWS IN THE PHOENIX AREA
TAFS BUT THE POTENTIAL SHOULD BE NOTED. OTHERWISE...SURFACE WINDS
BECOME SOUTHWEST AND WEST IN THE AFTERNOON THOUGH GUSTS SHOULD
REMAIN WELL BELOW 20 KTS. SOME INCREASING CIRRUS THURSDAY AFTERNOON
AHEAD OF AN APPROACHING UPPER LOW.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHWEST AND WEST SURFACE WINDS WILL WEAKEN OVERNIGHT THOUGH A
SOUTHERLY COMPONENT WILL PREVAIL IN THE WINDS ABOVE THE SURFACE.
SOUTH AND SOUTHEAST SURFACE WINDS WILL DEVELOP BY MIDDAY THURSDAY
WITH GUSTS TO 20 KNOTS. CIRRUS WILL BE ON THE INCREASE TOWARD
MORNING AHEAD OF AN APPROACHING UPPER LOW.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...NOLTE
AVIATION....AJ
FIRE WEATHER...VASQUEZ







000
FXUS65 KPSR 170956
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
256 AM MST THU APR 17 2014

.SYNOPSIS...
ANOTHER WARM AFTERNOON EXPECTED TODAY BEFORE A PACIFIC STORM MOVES
INTO THE AREA FRIDAY. THE PACIFIC LOW WILL SPREAD INCREASING MOISTURE
AND CLOUDS INTO THE AREA...SUPPORTING SLIGHT CHANCES FOR SHOWERS FROM
THE COLORADO RIVER EAST ACROSS SOUTH CENTRAL ARIZONA AND INTO THE
HIGHER TERRAIN. DAYTIME TEMPERATURES FOR FRIDAY AND SATURDAY WILL
FALL TO MORE SEASONAL VALUES WHILE THE STORM AND CLOUDS CLEAR TO THE
EAST. TEMPERATURES QUICKLY WARM BACK INTO THE 90S FOR NEXT WEEK WITH
MOSTLY SUNNY SKIES.

&&

.DISCUSSION...
UNDER CLEAR SKIES...TEMPERATURES THIS MORNING OVER THE FORECAST AREA
HAVE BEEN SLOWER TO COOL COMPARED TO YESTERDAY...WITH MID 60S TO LOW
70S IN THE LATEST 2AM OBS. TODAY`S TEMPERATURE FORECAST NEAR CARBON
COPY OF WEDNESDAY`S...WITH LOW TO MID 90S ACROSS THE DESERTS AND 80S
FOR THE FOOTHILL/HIGHER TERRAIN LOCALES. HIGH LEVEL CLOUDS WILL
GRADUALLY INCREASE FROM THE WEST THROUGH THE DAY...AHEAD OF A EAST
PACIFIC LOW MOVING ONSHORE.

PACIFIC LOW PRESSURE WILL MOVE INTO SO-CAL EARLY FRIDAY...SPREADING
MID AND HIGH LEVEL MOISTURE FROM THE SUBTROPICAL PACIFIC AHEAD OF IT.
FIRST AREA OF UPPER LOW DIFLUENCE AND 400-200MB OMEGA MOVE INTO
WESTERN ARIZONA BY FRIDAY AFTERNOON...SO SLIGHT CHANCE POPS WERE
EXPANDED TO THE LOWER COLORADO RIVER VALLEY. LOW END SLIGHT CHANCES
(MOSTLY 10 PERCENT) THEN EXPAND INTO THE SOUTH-CENTRAL DESERTS FOR
LATE FRIDAY AND SATURDAY AS THE LOW SLOWLY TRAVELS THROUGH THE AREA.
ADDITIONAL VORT ENERGY ON THE BACK OF THE LOW PROGGED TO SWEEP
THROUGH THE AREA SATURDAY...PROVIDING SOME ADDITIONAL LIFT TO
PERSIST SLIGHT CHANCES BEFORE THE SYSTEM EXITS TO THE EAST OVERNIGHT
SATURDAY/EARLY SUNDAY. MOSTLY CLOUDY TO OVERCAST SKIES ARE EXPECTED
FRIDAY WITH A VERY SLIGHT COOL DOWN IN TEMPERATURES...MOSTLY INTO THE
80S FOR THE LOWER DESERT ELEVATIONS.

MODELS HAVE BEEN GENERALLY BEEN CONSISTENT WITH THE OVERALL MOISTURE
PROFILE FOR THIS SYSTEM...GENERATING NEARLY SATURATED/SATURATED MID-
LEVEL SOUNDING PROFILES WITH VERY DRY SUB-CLOUD LAYERS AND INVERTED
V TRACES. WHILE CHANCES FOR LIGHT SHOWER AND ISOLATED THUNDER
ACTIVITY CONTINUE LOOK DECENT WITH THIS SYSTEM...WETTING OR EVEN
MEASURABLE RAINS ARE NOT EXPECTED. THE WARM AND DRY SUB-CLOUD LAYERS
LEND THEMSELVES MORE TOWARDS HIGH-BASED DEVELOPMENT WITH THE
POTENTIAL FOR GUSTY WINDS AND OUTFLOWS. THAT BEING SAID...CONSISTENCY
IN THE MODEL QPF PLACEMENT AND AMOUNTS HAS VARIED EVEN IN RECENT
FORECAST RUNS. ALSO CONSIDERING PAST UNDER-PERFORMANCES THIS SPRING
WITH OTHER EAST PACIFIC SYSTEMS MOVING INTO THE SOUTHWEST...BROAD
BRUSH SLIGHT CHANCES WITH NEAR ZERO QPF VALUES FROM FRIDAY MIDDAY
THROUGH SATURDAY MIDDAY WERE ADJUSTED INTO THE POP GRIDS.

DRY WESTERLY FLOW TRANSITIONS INTO THE AREA SUNDAY...QUICKLY WARMING
TEMPERATURES BACK INTO THE 90S FOR EARLY NEXT WEEK. BROAD AREA OF
PACIFIC TROUGHING STILL PROGGED TO SWEEP INTO THE WEST LATE MONDAY
INTO TUESDAY...ALTHOUGH LATEST MODEL RUNS VARY IN THEIR DEPTH AND
STRENGTH AS IT MOVES IN FROM THE NORTHEAST PACIFIC. THE SET-UP STILL
LOOKS PROMISING FOR A RETURN TO COOLER (AND MORE SEASONAL)
TEMPERATURES BY MIDDLE PART OF NEXT WEEK...BUT ANY CHANCES FOR RAIN
LOOK PRETTY REMOTE. MAINTAINED SOME INFLUENCE OF CLIMATOLOGY IN THE
POP GRIDS GIVEN THE PRESENCE OF TROUGHING...BUT UNLESS THE MODELS
EXPAND THE SOUTHERN EXTENT OF THE SYSTEM...EVEN THOSE SINGLE DIGIT
VALUES MAY BE OVERDONE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
WEAK WEATHER DISTURBANCE PASSING INTO NEW MEXICO TONIGHT. SURFACE
WINDS WILL BE LIGHT OVERNIGHT. HOWEVER...MODELS DEPICT WEST WINDS IN
THE LOW LEVELS ABOVE THE SURFACE INCREASING TO 20-25 KTS AROUND 2000
FT MSL BETWEEN 06-07Z AND DISSIPATING BY 09Z. THE INCREASE IN WEST
WINDS PROBABLY NOT QUITE ENOUGH TO INSERT LLWS IN THE PHOENIX AREA
TAFS BUT THE POTENTIAL SHOULD BE NOTED. OTHERWISE...SURFACE WINDS
BECOME SOUTHWEST AND WEST IN THE AFTERNOON THOUGH GUSTS SHOULD
REMAIN WELL BELOW 20 KTS. SOME INCREASING CIRRUS THURSDAY AFTERNOON
AHEAD OF AN APPROACHING UPPER LOW.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SOUTHWEST AND WEST SURFACE WINDS WILL WEAKEN OVERNIGHT THOUGH A
SOUTHERLY COMPONENT WILL PREVAIL IN THE WINDS ABOVE THE SURFACE.
SOUTH AND SOUTHEAST SURFACE WINDS WILL DEVELOP BY MIDDAY THURSDAY
WITH GUSTS TO 20 KNOTS. CIRRUS WILL BE ON THE INCREASE TOWARD
MORNING AHEAD OF AN APPROACHING UPPER LOW.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
SATURDAY THROUGH WEDNESDAY...
DRY WESTERLY FLOW ALOFT WITH WARMER AFTERNOON TEMPERATURES ARE
EXPECTED. HOWEVER BY WEDNESDAY A STRONG PACIFIC STORM IS FORECAST TO
MOVE INTO THE WESTERN STATES...RESULTING IN VERY STRONG SOUTHWEST
WINDS AND A CHANCE OF SHOWERS. OTHERWISE...MINIMUM HUMIDITIES SAT
THROUGH TUE SHOULD REMAIN IN THE 10 TO 15 PERCENT RANGE...INCREASING
WEDNESDAY.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

$$

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

DISCUSSION...NOLTE
AVIATION....AJ
FIRE WEATHER...VASQUEZ








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