Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 040440 AAA
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
940 PM MST FRI JUL 3 2015


.SYNOPSIS...
RELATIVELY HIGH MONSOON HUMIDITY AND UNSETTLED SOUTHERLY FLOW ALOFT
WILL KEEP THE CHANCE OF SHOWERS AND THUNDERSTORMS OVER SOUTH CENTRAL
ARIZONA TODAY...GENERALLY FROM PHOENIX EASTWARD. THE THREAT FOR
SHOWERS THIS WEEKEND WILL EXPAND INTO PARTS SOUTHWEST ARIZONA DURING
THE AFTERNOON AND EVENINGS. BY NEXT WEEK...DRIER WESTERLY FLOW WILL
WORK INTO THE REGION AND PUSH MOST OF THE MONSOON MOISTURE INTO
EASTERN ARIZONA WHERE THE THREAT OF THUNDERSTORMS WILL CONTINUE.

&&

.DISCUSSION...
ONCE AGAIN...LATE EVENING CONVECTION HAS DEVELOPED OVER PORTIONS OF
THE PHOENIX METRO DESPITE PALTRY LOOKING INSTABILITY PER PSR
SOUNDING AND SPC MESOANALYSIS. SEVERAL RUNS OF HRRR HAD BEEN
DEPICTING OUTFLOW FROM YAVAPAI COUNTY MOVING SOUTHWARD INTO PHOENIX
METRO THIS EVENING BUT WITHOUT THE STORM DEVELOPMENT THAT WE ARE
SEEING. THOUGH SURFACE DEW POINTS ARE NOT IMPRESSIVE...PWAT VALUES
ARE STILL A GOOD 1.5 INCHES OVER CENTRAL ARIZONA...LESS SO FURTHER
WEST...AND THUS THE STORMS ARE PRODUCING NOTABLE RAINFALL. IN
FACT...THE STRONGEST STORMS HAVE PRODUCED LOCALIZED STREET FLOODING.
ISOLATED SHOWERS AND THUNDERSTORMS HAVE ALSO DEVELOPED FURTHER WEST
OVER WESTERN MARICOPA COUNTY AND LA PAZ COUNTY. CONVECTION HAS BEEN
MUCH MORE WIDESPREAD OVER NORTHERN ARIZONA BUT GIVEN THE SOUTHERLY
COMPONENT TO THE STEERING FLOW...NOT ANTICIPATING THAT ACTIVITY TO
ADVECT IN A BIG WAY OVER OUR AREA. OVERALL...ANTICIPATE LESS
ACTIVITY TONIGHT THAN WHAT WE HAD LAST NIGHT. THERE IS STILL A
POSSIBILITY OF VERY LATE NIGHT AND MORNING DEBRIS CLOUDS/SHOWERS
FROM SONORA BUT THAT ACTIVITY IS ALSO LESS ROBUST TONIGHT THAN LAST
NIGHT. ACCORDINGLY...ANTICIPATE LESS CLOUDINESS/SHOWERS SATURDAY
MORNING THAN WHAT WE HAD THIS MORNING.

&&

.PREVIOUS DISCUSSION ISSUED 246 PM MST/PDT...

RAIN SHOWER AND ISOLATED THUNDERSTORMS STILL CONTINUE UNDERNEATH AN
UPPER DEFORMATION ZONE STRETCHING ACROSS WEST CENTRAL NM AND
SPANNING WESTWARD INTO AZ AND EVEN ACROSS THE CO RIVER VALLEY. BROAD
CLOUD SHIELD OVER MUCH OF CENTRAL AZ THROUGH THE DAY HAS KEPT MOST
TEMPERATURES AROUND THE AREA SIGNIFICANTLY COOL...WITH MANY SITES
AROUND PHOENIX-COOLIDGE-WICKENBURG STILL IN THE 90S. CLOUD COVER HAS
EXPANDED TOWARDS AND OVER THE CO RIVER VALLEY BUT TEMPERATURES
REMAIN ON TRACK FOR THEIR FORECAST HIGHS IN PLACES LIKE YUMA AND
IMPERIAL AROUND 103-106F. AROUND THE REGION...INVERTED TROUGH
CIRCULATION EVIDENT ON SATELLITE LOOPS AND UA ANALYSIS THIS MORNING
ACROSS NORTHERN/CENTRAL AZ WAS MOSTLY CAPTURED IN THE 12Z
DETERMINISTIC MODEL INITIALIZATION...HOWEVER MOISTURE FIELDS WERE
STILL GENERALLY UNDERDONE. EVEN WITHOUT A FAIR INITIALIZATION...FCST
MOISTURE VALUES ACROSS THE REGION STILL QUITE EXCESSIVE FOR THIS
EARLY IN THE MONSOON WITH 850MB DEWPOINTS 10-12C AND 700MB DEWPOINTS
STILL IN THE 3-6C RANGE. LOOK FOR LIGHT SHOWERS TO PERCOLATE FOR THE
REST OF THE AFTERNOON WHILE GRADUALLY DRIFTING WEST-NORTHWESTWARD.
MEANWHILE...THUNDERSTORM ACTIVITY WILL CONTINUE TO DEVELOP OVER THE
NORTHERN/EASTERN HIGHER TERRAIN...WITH WHAT IS EXPECTED TO BE A
SLOWER START TO CONVECTION ACROSS THE SOUTHEAST AZ/NORTHERN SONORA
CORNER OF THE WORLD.

WITH SUCH A RICH MOISTURE SFC...ANY RIPPLE/DISTURBANCE/OUTFLOW/MCV
THAT TRAVELS INTO THE AREA COULD HELP GEN-UP PRECIPITATION ACTIVITY
ACROSS THE AZ DESERT LOCALES. THE BETTER INITIALIZED HI-RES MODELS
INDICATE AN ACTIVE AFTN/EVENING ON THE RIM COULD SEND SOME OUTFLOWS
DOWN FROM THE NORTH. ALSO...CURRENT FORECAST RATIONALE FROM OUR
NEIGHBORS IN TUCSON LENDS ITSELF TO ANOTHER LARGE SONORA STORM
COMPLEX THAT COULD FURTHER ADD STORM ACTIVITY INTO THE EVENING. WILL
MAINTAIN SLIGHT CHANCES OVERNIGHT FROM LA PAZ TO GILA...MARICOPA AND
PINAL COUNTIES OVERNIGHT. GRADUALLY DECREASING ML/UL WIND FIELDS
WILL GENERALLY POINT TO SLOWER MOVING STORMS AND AGAIN WITH ABUNDANT
MOISTURE ACROSS THE REGION...HEAVY RAINFALL OVER AN AREA IN A SHORT
PERIOD OF TIME WILL BE A CONCERN WITH ANY DEVELOPMENT LATER INTO THE
EVENING.

300/250 MB HIGH CENTERS WILL CONTINUE TO MIGRATE THROUGH NM SATURDAY
AND SUNDAY...VEERING SOME OF THE ABOVE MENTIONED NOCTURNAL CONVECTION
COULD SPREAD AS FAR
WEST AS BLH AND I ALSO INCLUDED A VCSH MENTION AFTER 09Z. NEARLY ALL
GUIDANCE KEEPS IPL DRY ALTHOUGH THEY WILL ALMOST CERTAINLY SEE
INCREASED CLOUD COVER OVERNIGHT AS STORMS DEVELOP/DISSIPATE OVER
MEXICO.
G THE BELT OF STRONG UL WINDS AND STEERING FLOW
FURTHER INTO SOCAL AND THE CO RIVER VALLEY. MODEL STREAMLINE
FORECASTS DO NOT POINT TO ANYONE PARTICULAR DISTURBANCE OR INVERTED
TROUGH PASSAGE FOR SATURDAY...BUT DO HAVE POTENTIAL FOR SOMETHING
MORE ORGANIZED TO COME UP FROM THE GULF OF CA FOR SUNDAY. THE AREA
IS ALSO PROGGED TO GET ANOTHER SURGE OF MOISTURE THE SOUTH...TAPPING
INTO A POTENTIAL 2 INCH PWAT SURFACE ACROSS SONORA...PUSHING 850MB
AND 700MB DEWPOINTS BEYOND THE 8 AND 10C MONSOON LEVELS EARLY
SUNDAY. SATURDAY CARRIES A SLIGHT CHANCE OF STORMS ACROSS THE LOWER
AZ DESERT ELEVATIONS...WITH INCREASING CHANCES IN TERMS OF
PERCENTAGES AND AREAL COVERAGE FOR SUNDAY. BELOW-NORMAL TEMPERATURES
LOOK TO THE BE RULE THIS PERIOD...WITH PLENTY OF RAIN-COOLED AIR AND
DEBRIS CLOUDS LEAVING DAYTIME TEMPS RUNNING THE UPPER 90 TO 105
RANGE OR SO.

MONDAY THROUGH FRIDAY...
LATEST GFS MODEL FORECASTS HAVE CHANGED SINCE YDA...AND NOW
FORECASTS THE MID/UPPER LEVEL FLOW TO BECOME MORE WESTERLY THRU
FRIDAY. ONLY ONE PERTURBATION IS FORECAST TO MOVE INTO AZ ABOUT
TUESDAY. AS A RESULT...MOST OF THE BOUNDARY LAYER MOISTURE GETS
PUSHED INTO THE EASTERN HALF OF THE STATE. THEREFORE THE CONVECTIVE
POTENTIAL WILL FAVOR THE MOUNTAINS NORTH THROUGH EAST OF PHOENIX.
MID LEVEL STEERING CURRENTS ALSO BECOME WESTERLY. THEREFORE A ONLY A
SLIGHT CHANCE OF LATE AFTERNOON/EVENING STORMS ARE FORECAST ON THE
SOUTH CENTRAL DESERTS...WITH SLIGHTLY HIGHER PROBABILITIES IN OUR
MOUNTAINOUS ZONE 24 EAST OF PHOENIX.

NEXT SATURDAY...
MODELS FORECAST AN INVERTED TROF IN THE EASTERLIES TO ROTATE OUT OF
WEST TEXAS THURSDAY NIGHT...AND INTO SOUTHERN AZ FRIDAY NIGHT OR
SATURDAY MORNING. NOT MUCH CREDENCE IS PUT INTO THE EXTENDED MODEL
FORECASTS DURING THE MONSOON...THEREFORE WE WILL CONTINUE WITH THE
LOW GRADE MONSOON THREAT OF AFTN/EVE SHWRS AND TSTMS OVER
PINAL...EASTERN MARICOPA...AND SOUTHERN GILA COUNTIES.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...KSDL...
ISOLATED SHOWERS AND THUNDERSTORMS OVER FAR NORTHERN MARICOPA
COUNTY AS OF 04Z ARE LIKELY TO EXPAND FURTHER SOUTH INTO THE PHOENIX
METRO. MOST LIKELY TAF SITE TO BE AFFECTED WILL BE KSDL. NOT
ANTICIPATING AS MUCH ACTIVITY AS LAST NIGHT BUT KPHX WILL HAVE A
50/50 CHANCE OF GETTING TSRA AND GUSTY/VARIABLE WINDS BETWEEN 04Z-
08Z. HOWEVER...NOT ANTICIPATING STORMS TO BE SEVERE. CIGS
SHOULD REMAIN ABOVE 5 KFT MSL BUT HEAVIEST SHOWERS COULD CAUSE
LOCALIZED VISIBILITY TO DROP BELOW 3SM. AFTER 09Z...DEBRIS CLOUDS
AND ISOLATED LIGHT SHOWERS ARE POSSIBLE FROM REMNANTS OF SONORA
MEXICO STORMS. THUS THE MENTION OF VCSH.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
ISOLATED SHOWERS AND THUNDERSTORMS CAN BE EXPECTED OVER MAINLY LA
PAZ AND RIVERSIDE COUNTIES TONIGHT...WITH POTENTIAL TO LINGER INTO
THE MORNING HOURS. NOT ANTICIPATING STORMS TO BE SEVERE AND CIGS
SHOULD REMAIN ABOVE 5 KFT MSL. HEAVIEST SHOWERS COULD CAUSE
LOCALIZED VISIBILITIES TO DROP BELOW 3SM.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
FLOW ALOFT WILL BECOME MORE SOUTHWESTERLY NEXT WEEK...ALLOWING THE
DEEPEST MOISTURE TO BE RE-POSITIONED TO THE NORTH/EAST OF PHOENIX.
THIS WILL RESULT IN A DECREASED CHANCE OF DESERT SHOWERS AND
THUNDERSTORMS NEXT WEEK...WITH FAIRLY TYPICAL AFTERNOON ACTIVITY
ACROSS SOUTHERN GILA COUNTY. HUMIDITIES WILL FALL INTO THE 10-15
PERCENT RANGE ACROSS THE DESERTS WITH FAIR TO GOOD OVERNIGHT
RECOVERIES ANTICIPATED ALL WEEK. HIGHER VALUES WILL BE SEEN IN THE
MOUNTAINS. AS FOR WINDS...LIGHT/DIURNALLY DRIVEN SPEEDS/DIRECTIONS
WILL DOMINATE ALL WEEK.

&&

.SPOTTER INFORMATION STATEMENT...
SPOTTERS ARE ENCOURAGED TO REPORT ANY SIGNIFICANT WEATHER CONDITIONS
ACCORDING TO STANDARD OPERATING PROCEDURES.

&&

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

$$

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

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


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