Heavy Rain in Arizona, July 3, 2015

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
246 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...
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 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 HAVE RE-DEVELOPED THIS AFTERNOON BUT HAVE LARGELY AVOIDED
THE PHOENIX TERMINALS. THIS TREND SHOULD CONTINUE THROUGH LATE
AFTERNOON AND I WILL KEEP ANY MENTION OF SHRA OUT OF THE TAFS
THROUGH EARLY EVENING.

CONDITIONS COULD TURN INTERESTING AGAIN LATE TONIGHT AS SOME OF THE
BETTER PERFORMING HI-RES GUIDANCE IS SUGGESTING ANOTHER ROUND OF
NOCTURNAL CONVECTION MOVING IN FROM THE EAST. MODEL SOLUTIONS ARE ALL
OVER THE PLACE TODAY BUT ENOUGH ARE SUGGESTING THIS POSSIBILITY THAT
I MENTIONED VCSH IN THE PHOENIX TERMINALS AFTER MIDNIGHT TONIGHT.
UNFORTUNATELY...LOW CONFIDENCE FORECAST FROM MID EVENING ONWARD.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
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.

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.
&&

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