Severe Thunderstorm Warning 54, NWS Phoenix, AZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PHOENIX AZ
419 PM MST SUN AUG 17 2014

.UPDATE...UPDATED AVIATION DISCUSSION...

&&

.SYNOPSIS...
ISOLATED SHOWERS AND THUNDERSTORMS WILL AGAIN BE POSSIBLE ACROSS THE
REGION THIS EVENING AS MONSOON MOISTURE BEGINS TO SLOWLY INCREASE.
BY MONDAY...AN EARLY SEASON PACIFIC LOW PRESSURE SYSTEM WILL
APPROACH THE AREA AND DRAW EVEN MORE MONSOON MOISTURE NORTHWARD BACK
INTO ARIZONA. MORE WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY IS
EXPECTED ACROSS ARIZONA FROM LATE MONDAY THROUGH WEDNESDAY. WITH THE
INCREASE IN HUMIDITIES AND CLOUDS...BELOW NORMAL TEMPERATURES ARE
POSSIBLE BY TUESDAY AND MAY CONTINUE LATER INTO THE WORK WEEK.

&&

.DISCUSSION...
BROAD AREA OF DEFORMATION STRETCHES FROM WESTERN NM THOUGH SOUTHWEST
AZ...WHERE THE STRONGEST STORM ACTIVITY OF THE DAY SO FAR HAS BEGUN
DEVELOPING. WITH EARLIER INVERTED WAVE ENERGY STILL LINGERING ACROSS
THE SOUTHERN AZ BORDER...EXPECT STORM COVERAGE FOR THE REMAINDER OF
THIS AFTERNOON AND EVENING TO BE MARGINALLY MORE THAN THAT OF THE
PAST FEW NIGHTS...WITH THE STRONGEST STORMS OVER THE HIGHER TERRAIN
AND MORE ISOLATED SHORT-LIVED ACTIVITY PULSING OVER THE WESTERN AND
SOUTHWESTERN DESERTS. DAYTIME TEMPERATURES ON TARGET TO TOP OUT JUST
ABOVE MID-AUGUST NORMALS...WITH THE WARMEST LOCALES ACROSS THE
WESTERN DESERTS INCLUDING EL CENTRO...YUMA...AND TACNA...WARMING TO
OR ABOVE 110F DEGREES. EXPECT PARTLY CLOUDY SKIES BACK ACROSS SOUTH-
CENTRAL AND EASTERN AZ THROUGH THE EVENING...WITH MOSTLY CLEAR SKIES
ALONG AND WEST OF THE CO RIVER VALLEY. ANY DAYTIME CU SHOULD QUICKLY
DISSIPATE AFTER SUNSET...WITH AREAS DEBRIS CLOUDS AND CIRRUS FROM
STORMS LINGERING.

BEGINNING MONDAY AND LASTING AT LEAST THROUGH LATE
TUESDAY...POSSIBLY BEYOND...WE'LL BE LOOKING AT INCREASING MOISTURE
LEVELS AS WELL AS UPPER LEVEL DYNAMICS THAT COULD LEAD TO MORE WIDELY
ACTIVE AFTERNOONS/EVENINGS ACROSS ARIZONA AND TO A LESSER EXTENT
SOUTHEAST CA. SEVERAL FACTORS WILL COME TOGETHER TO SUPPORT THE
TRANSPORT OF DEEPER MOISTURE AND UPPER LEVEL DYNAMICS ACROSS THE
REGION. THE FIRST BEING A RATHER VIGOROUS EARLY-SEASON UPPER LOW
CENTER MOVING SOUTHWARD ALONG THE CA COAST AND THE NEXT BEING THE
SHIFTING UPPER HIGH CENTER EASTWARD FROM AZ INTO TX. THIS PATTERN
ALLOWS THE FLOW ALOFT TO BECOME MORE SOUTHERLY...ALLOWING A
CONSIDERABLE AMOUNT OF MOISTURE THAT IS NOW OVER NORTHERN MEXICO TO
BE DRAWN NORTHWARD INTO AZ. IN ADDITION TO BACKGROUND MOISTURE
LEVELS ALREADY OVER NORTHERN MEXICO...A VERY SWIFT MOVING AREA OF
ENERGY AND STORMS HAS RACED UP ALONG THE MEXICAN COAST DURING THE
DAY NOW OBSERVED OVER SINALOA...COVERING ALMOST 600 MILES OF
COASTLINE OVER THE LAST 12 HOURS. WILL BE LOOKING FOR THAT FEATURE
TO AT LEAST BE THE LEADING EDGE OF THE ANTICIPATED MOISTURE SURGE
INTO THE SOUTHWEST DESERTS OVERNIGHT AND INTO TUESDAY.

IT APPEARS THAT SOUTHEAST CA'S CHANCES FOR THUNDERSTORMS COULD BE
FAR LESS...DUE TO THE AFOREMENTIONED UPPER LOW SPREADING MUCH DRIER
AIR INTO THE REGION. THE MAIN IMPACTS FROM THUNDERSTORMS
MONDAY...TUESDAY AND POSSIBLY OVERNIGHT INTO WEDNESDAY WILL BE
LOCALLY HEAVY RAIN AND WET MICROBURSTS...DUE TO THE VERY MOIST
ENVIRONMENT IN THE LOWER LEVELS OF THE ATMOSPHERE THAT IS FORECAST TO
DEVELOP OVER THE REGION. THE ONLY LIMITING FACTOR FOR WIDESPREAD
THUNDERSTORM DEVELOPMENT MAY BE THE FACT THAT SOUTHWESTERLY FLOW
ALOFT IS FORECAST TO DEVELOP OVER THE REGION AHEAD OF THIS UPPER LOW
CENTER...WHICH IS GENERALLY LESS FAVORABLE FOR THUNDERSTORM
DEVELOPMENT OVER THE LOWER DESERTS DURING THE MONSOON SEASON THAN
DURING PERIODS OF EASTERLY FLOW ALOFT.

WHERE CONFIDENCE IS GROWING FOR AN ACTIVE MONDAY-EARLY WEDNESDAY TIME
PERIOD...AS THE PREVIOUS SHIFT PUT IT BEST AT THE SHIFT
BRIEFING THIS AM...CONFIDENCE ALL BUT COLLAPSES FOR THE REMAINDER OF
THE WORK WEEK. THIS IS DUE TO THE FACT THAT THE GFS MAINTAINS THE
SOLUTION OF BRINGING ANOTHER EVEN LARGER AREA OF MOISTURE NORTHWARD
INTO THE REGION FROM A DYING TROPICAL CYCLONE THAT IS FORECAST TO
DEVELOP WELL SOUTH OF BAJA AS THE MAIN UPPER LOW SWINGS SLOWLY
NORTHEASTWARD INTO NORTHERN AZ. THE EURO AND GEM...ON THE OTHER
HAND...RETROGRADE THIS SAME UPPER LOW OFF TO OUR WEST OVER THE EAST
PACIFIC AND KEEPS ANY TROPICAL MOISTURE WELL OFF TO OUR
SOUTHWEST...AS IT REBUILDS A DRIER MAIN UPPER RIDGE BACK OVER THE
DESERT SOUTHWEST. GIVEN THESE CONTINUED MODEL DISCREPANCIES...BUT
MARGINAL IMPROVEMENT IN RUN-TO-RUN CONSISTENCY...HAVE KEPT THE
REMAINDER OF THE FORECAST FOR THE WORK WEEK TOWARDS A LOW TO MEDIUM
GRADE MONSOON PATTERN...WHICH CLIMATOLOGICALLY IS THE MORE LIKELY
SOLN FOR MID-AUGUST AROUND HERE. THE BEST CHANCES FOR STORM ACTIVITY
OVER THE MOUNTAINS AND ISOLATED POTENTIAL FOR ACTIVITY LASTING OVER
THE LOWER DESERTS IN THE AFTERNOON AND EVENINGS.

FRIDAY THROUGH SUNDAY...
GIVEN THE FACT THAT BOTH THE GFS AND EURO AND NOW BOTH A FAIRLY
MAJOR LOW-WAVE TROF (FOR MID-AUG) SOUTHWARD INTO THE WESTERN CONUS
DURING THIS PERIOD...WHICH TYPICALLY MEANS A REDUCTION OF MONSOON
ACTIVITY AS THIS TROF USUALLY KEEPS THE MAIN MONSOON PLUME WELL OFF
TO OUR SOUTH AND EAST...HAVE DECIDED TO GO WITH SLIGHTLY BELOW CLIMO
POPS ACROSS THE REGION...AND NEAR-NORMAL TEMPS FOR NOW.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...
CONVECTION CONTINUES TO BLOSSOM EAST OF PHOENIX BUT IS NOT EXPECTED
TO SURVIVE ACROSS THE DESERTS. I AM CONCERNED HOWEVER THAT THE
STORMS WILL PUSH NORTHEASTERLY WINDS THROUGH THE METRO LATER THIS
EVENING AND I HAVE INTRODUCED A WIND SHIFT BETWEEN 02Z-04Z. STORMS
ARE STILL A LONG WAY OFF SO MY CONFIDENCE IN THE EXACT TIMING OF ANY
POTENTIAL WIND SHIFT IS LOW. NOT OVERLY CONCERNED ABOUT WIDESPREAD
BLDU GIVEN THE NORTHEASTERLY FETCH OVER THE MOUNTAINS BUT KIWA WOULD
BE THE MOST LIKELY LOCATION TO SEE BLDU.

SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA INCLUDING KIPL AND KBLH...
STORMS HAVE BEEN SHORT LIVED ACROSS SOUTHWEST ARIZONA AND DEBRIS
CLOUDS SHOULD BE ABOUT THE ONLY THING TO CONTEND WITH THE REST OF
THE AFTERNOON/EVENING. SOME MODEL GUIDANCE IS SUGGESTING STORMS WILL
DEVELOP ACROSS THE AREA WELL AFTER MIDNIGHT /ASSOCIATED WITH A
COMPLEX OF STORMS OVER SOUTHERN SONORA/. I WANT TO SEE WHAT HAPPENS
WITH THAT COMPLEX AND HOW LONG IT SURVIVES BEFORE I INTRODUCE ANY
MENTION OF RAIN OR THUNDER IN EITHER SE CA TAF.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
DEEP MONSOON MOISTURE WILL CONTINUE THIS PERIOD WITH HIGHER THAN
NORMAL RELATIVE HUMIDITY. A GOOD CHANCE OF AFTERNOON AND EVENING
THUNDERSTORMS ARE EXPECTED OVER HIGHER MOUNTAINS OF SOUTHERN GILA
COUNTY EACH DAY...WITH A SLIGHT CHANCE OF THUNDERSTORMS ON THE LOWER
SOUTHWEST AND SOUTH CENTRAL DESERTS. MINIMUM RELATIVE HUMIDITIES WILL
RANGE FROM 25 TO 30 PERCENT. OVERNIGHT RECOVERY WILL BE FAIR.
AFTERNOON TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL THIS PERIOD.
ADDITIONALLY...AFTERNOON/EARLY EVENING WINDS WILL BE SOUTHWESTERLY
AND GENERALLY UNDER 20 MPH...EXCEPT NEAR THUNDERSTORMS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...NONE.

CA...NONE.

&&

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

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PHOENIX AZ
314 PM MST SUN AUG 17 2014

AZZ021>024-026>028-181500-
WEST CENTRAL DESERTS-NORTHWEST MARICOPA COUNTY-GREATER PHOENIX AREA-
SOUTHERN GILA COUNTY/TONTO NATIONAL FOREST FOOTHILLS-
SOUTHWEST DESERTS-SOUTHWEST MARICOPA COUNTY-
NORTHWEST AND NORTH CENTRAL PINAL COUNTY-
314 PM MST SUN AUG 17 2014

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST-CENTRAL ARIZONA...SOUTH-
CENTRAL ARIZONA...SOUTHWEST ARIZONA AND WEST-CENTRAL ARIZONA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

ANOTHER ROUND OF AFTERNOON AND EVENING MONSOON THUNDERSTORMS ARE
POSSIBLE OVER THE HIGHER TERRAIN AND FOOTHILLS EAST OF THE PHOENIX
METROPOLITAN AREA AS WELL AS THE WESTERN ARIZONA DESERTS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THE COMBINATION OF A RATHER STRONG UPPER LEVEL LOW CENTER (FOR MID-
AUGUST) APPROACHING FROM THE NORTHWEST AND INCREASING MOISTURE FROM
THE SOUTH WILL LEAD TO A RISING THREAT OF AFTERNOON AND EVENING
THUNDERSTORMS FOR MONDAY AND TUESDAY. HEAVY RAIN...LOCALIZED
FLOODING AND STRONG GUSTY WINDS ARE THE PRIMARY WEATHER HAZARDS
ASSOCIATED WITH ANY STORM THAT DEVELOPS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED FOR MONDAY AND TUESDAY. WEATHER
SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS
ACCORDING TO STANDARD OPERATIONS PROCEDURES.

AZZ020-025-CAZ031>033-181500-
LOWER COLORADO RIVER VALLEY AZ-YUMA/MARTINEZ LAKE AND VICINITY-
LOWER COLORADO RIVER VALLEY CA-RIVERSIDE COUNTY/EASTERN DESERTS-
IMPERIAL COUNTY-
314 PM MST SUN AUG 17 2014 /314 PM PDT SUN AUG 17 2014/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EXTREME SOUTHWEST
ARIZONA...EXTREME WEST-CENTRAL ARIZONA AND EXTREME SOUTHEAST
CALIFORNIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THE COMBINATION OF A RATHER STRONG UPPER LEVEL LOW CENTER (FOR MID-
AUGUST) APPROACHING FROM THE NORTHWEST...AND INCREASING MOISTURE
FROM THE SOUTH WILL LEAD TO A RISING THREAT OF AFTERNOON AND EVENING
THUNDERSTORMS FOR MONDAY AND TUESDAY. STRONG GUSTY WINDS...HEAVY
RAIN...AND LOCALIZED FLOODING ARE THE PRIMARY WEATHER HAZARDS
ASSOCIATED WITH ANY STORM THAT DEVELOPS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED FOR MONDAY AND TUESDAY. WEATHER
SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS
ACCORDING TO STANDARD OPERATING PROCEDURES.

NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT

WEATHER.GOV/PHOENIX

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PHOENIX AZ
423 PM MST SUN AUG 17 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0421 PM     TSTM WND GST     3 ENE CLAYPOOL          33.45N 110.77W
08/17/2014  M70 MPH          GILA               AZ   TRAINED SPOTTER

&&

EVENT NUMBER PSR1400199

LEINS

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PHOENIX AZ
425 PM MST SUN AUG 17 2014

AZZ024-180000-
GILA AZ-PINAL AZ-
425 PM MST SUN AUG 17 2014

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  SOUTH CENTRAL GILA COUNTY IN EAST CENTRAL ARIZONA
  NORTH CENTRAL PINAL COUNTY IN SOUTH CENTRAL ARIZONA

UNTIL 500 PM MST

AT 422 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 6 MILES SOUTH OF CUTTER...MOVING WEST AT 25 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
   PINAL PEAK...

LAT...LON 3317 11051 3313 11059 3314 11062 3311 11066
      3311 11068 3309 11068 3308 11069 3306 11079
      3308 11085 3324 11095 3322 11100 3336 11100
      3335 11050
TIME...MOT...LOC 2325Z 087DEG 22KT 3327 11070

18

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PHOENIX AZ
428 PM MST SUN AUG 17 2014

AZZ024-180000-
GILA AZ-MARICOPA AZ-
428 PM MST SUN AUG 17 2014

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  CENTRAL GILA COUNTY IN EAST CENTRAL ARIZONA
  EXTREME EAST CENTRAL MARICOPA COUNTY IN SOUTH CENTRAL ARIZONA

UNTIL 500 PM MST

AT 427 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 6 MILES NORTH OF ROOSEVELT DAM...MOVING SOUTHWEST
AT 15 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
   PUNKIN CENTER...
   ROOSEVELT DAM... ROOSEVELT AND TONTO NATIONAL MONUMENT...FOUR
PEAKS...

LAT...LON 3380 11115 3376 11097 3365 11092 3367 11088
      3366 11085 3354 11108 3370 11145 3386 11135
      3388 11123
TIME...MOT...LOC 2329Z 042DEG 15KT 3376 11118

18

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PHOENIX AZ
430 PM MST SUN AUG 17 2014

AZZ024-180000-
GILA AZ-MARICOPA AZ-
430 PM MST SUN AUG 17 2014

...SIGNIFICANT WEATHER ADVISORY...

THE NATIONAL WEATHER SERVICE IN PHOENIX HAS ISSUED A

SIGNIFICANT WEATHER ADVISORY FOR...
  WEST CENTRAL GILA COUNTY IN EAST CENTRAL ARIZONA
  NORTHEASTERN MARICOPA COUNTY IN SOUTH CENTRAL ARIZONA

UNTIL 500 PM MST

AT 427 PM MST...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 11 MILES NORTHWEST OF SYCAMORE CREEK...MOVING
SOUTH AT 15 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THIS STORM.

LOCATIONS IMPACTED INCLUDE...
   SYCAMORE CREEK...
   SUNFLOWER...

LAT...LON 3370 11140 3384 11186 3401 11177 3400 11151
      3401 11150 3402 11143
TIME...MOT...LOC 2330Z 011DEG 11KT 3399 11165

18

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