Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 061059
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
400 AM MST MON JUL 6 2015

.SYNOPSIS...

ISOLATED SHOWERS AND THUNDERSTORMS THIS MORNING WILL BE LIMITED TO
PORTIONS OF SOUTH-CENTRAL ARIZONA. STORM CHANCES REDEVELOP THIS
AFTERNOON EAST OF THE LOWER COLORADO RIVER VALLEY BUT WITH LESS
ACTIVITY THAN WAS SEEN SUNDAY. DRIER SOUTHWESTERLY FLOW ALOFT IS
FORECAST TO DEVELOP OVER THE REGION WITH THE APPROACH AND PASSAGE OF
AN UPPER LEVEL TROUGH. THIS WILL RESULT IN MONSOON MOISTURE BEING
CONFINED OVER EASTERN ARIZONA TUESDAY THROUGH FRIDAY. ANTICIPATE
TEMPERATURES TO BE SLIGHTLY BELOW NORMAL. NEXT WEEKEND...HIGH
PRESSURE IS ANTICIPATED TO STRENGTHEN OVER THE REGION FOR SOMEWHAT
WARMER TEMPERATURES AND POSSIBLY AN INCREASE IN MOISTURE.

&&

.DISCUSSION...

TODAY...

LATE NIGHT STORMS DEVELOPED EARLIER OVER NORTHERN LA PAZ COUNTY FROM
BACK-BUILDING STORMS THAT HAD BEEN OVER SOUTHERN MOHAVE COUNTY AND
FAR SOUTHWEST YAVAPAI. THOSE STORMS HAVE PRODUCED OUTFLOW ALONG WITH
EVEN EARLIER STORMS FROM CENTRAL YAVAPAI WHICH APPEARS TO HAVE
TRIGGERED NEW STORMS OVER NORTHWEST MARICOPA COUNTY AND AS OF THIS
WRITING ISOLATED WEAK ECHOES OVER METRO PHOENIX. THERE IS A MOISTURE
GRADIENT NEAR THE LOWER COLORADO RIVER VALLEY WITH DRIER AIR OVER
SOUTHEAST CALIFORNIA AND MORE MOIST AIR OVER ARIZONA. EARLIER
TONIGHT THE SURFACE DEW POINT AT YUMA AND EL CENTRO HAD DROPPED TO
THE UPPER 40S AND BLYTHE DROPPED TO NEAR 50. DEW POINTS HAVE GONE
BACK UP...MOST NOTICEABLY AT YUMA AND EL CENTRO. MEANWHILE DEW
POINTS HAVE STAYED WELL INTO THE 60S OVER MARICOPA AND PINAL
COUNTIES. ANTICIPATE ISOLATED SHOWER/THUNDERSTORM DEVELOPMENT OVER
METRO PHOENIX INTO THE MORNING HOURS...POSSIBLY MORE NUMEROUS
WESTERN AND NORTHERN PORTIONS. THERE MAY BE AN UPPER LEVEL SHORT
WAVE...EMANATING FROM THE UPPER LOW CENTERED OFF THE CALIFORNIA
COAST...WHICH IS HELPING TO SUSTAIN THE CONVECTION DESPITE THE LARGE
AMOUNT OF CIN DEPICTED IN THE SPC MESOANALYSIS. THE HRRR HAS BEEN
INDICATING ISOLATED CONVECTION OVER SOUTH-CENTRAL ARIZONA THIS
MORNING THOUGH NOT AS MUCH AS WE HAVE ALREADY SEEN. FOR LATER
TODAY...MODELS NOT OPTIMISTIC ON STORM COVERAGE FOR OUR AREA AS
DRIER AIR BEGINS TO MAKE ITS WAY EASTWARD. THE NAM APPEARS TO BE
MORE AGGRESSIVE THAN OTHER MODELS. WHILE WE TEND NOT TO GET MUCH
ACTIVITY WITH SOUTHWESTERLY FLOW ALOFT...MORE THAN ONE MODEL IS
INDICATING A 500 MB SHORT WAVE TRACKING OVER THE AREA LATER TODAY.
THIS COMBINED WITH LINGERING MOISTURE SHOULD PROVIDE AT LEAST A
SLIGHT CHANCE OVER THE LOWER DESERTS OF ARIZONA. THUS REINTRODUCED
POPS IN THOSE AREAS FOR THIS AFTERNOON/EVENING. ANTICIPATE BETTER
CHANCES OVER THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX.

TUESDAY AND WEDNESDAY...

EXPECT LOW GRADE MONSOON CONDITIONS AS DRIER AIR FROM THE WEST TAKES
OVER. ACCORDINGLY...HUMIDITIES WILL DECREASE AND DIURNAL TEMPERATURE
RANGES WILL INCREASE.

THURSDAY AND FRIDAY...

AS THE UPPER LOW BECOMES CENTER MOVES OVER CALIFORNIA THURSDAY...A
DEEPER SOUTHERLY FLOW IS ANTICIPATED TO INCREASE MOISTURE OVER THE
EASTERN THIRD OF ARIZONA...WITH DRY AIR WEST OF THERE. ALSO A VORT
LOBE SWINGS THROUGH MAINLY SOUTHEAST CALIFORNIA AND WESTERN ARIZONA
AS DEPICTED BY BOTH THE GFS AND ECMWF. IN ADDITION...THEY ARE
INDICATING SOME DIFFLUENCE RELATED UPPER LEVEL DIVERGENCE. NOT
KNOWING JUST HOW MUCH MOISTURE WILL BE AVAILABLE...MADE SOME JUST
SOME SUBTLE UPWARD ADJUSTMENTS TO THE POPS OVER OUR EASTERN AREAS.
THE LOW WEAKENS AND SHIFTS NORTHEASTWARD THURSDAY BUT IS REPLACED
WITH RENEWED TROUGHING NEAR THE CALIFORNIA COAST ON FRIDAY. THUS THE
MOISTURE OVER EASTERN ARIZONA MAY REMAIN IN PLACE FOR LITTLE CHANGE
IN THE FORECAST. WITH THE RIDGE BEING SHIFTED FURTHER EAST...TEMPS
COOL A LITTLE BIT.

SATURDAY AND SUNDAY...

FOR NEXT WEEKEND...MEDIUM RANGE MODELS DEPICT A WESTWARD EXPANSION
OF THE HIGH CENTERED TO OUR EAST WITH MOISTURE IMPROVING OVER THE
LOWER DESERTS. THE GFS IS MORE GENEROUS WITH THE MOIST ADVECTION THE
ECMWF. WITH STRONGER HIGH PRESSURE...TEMPERATURES ALOFT WILL BE
WARMER AND WHICH COULD OFFSET TO SOME DEGREE THE MOISTURE INCREASE.
TOOK CONSERVATIVE APPROACH AND ONLY EXPANDED POPS TO PINAL COUNTY.
ANTICIPATE TEMPERATURES TO BE WARMER AT THE SURFACE AS WELL WITH
HIGHS NUDGING UP ABOVE 105.

&&


.AVIATION...

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

RAIN-COOLED OUTFLOW WINDS HAVE SIGNIFICANTLY STABILIZED THE BOUNDARY
LAYER AND THE THREAT OF CONVECTION FOR THE REST OF TONIGHT IS RATHER
LOW. STILL...CANNOT RULE OUT A SHOWER OVERNIGHT BUT CONFIDENCE IS
TOO LOW TO MENTION IN THE AREA TAFS.

WINDS HAVE BEEN VERY PROBLEMATIC THIS EVENING. DURING THE LATE
AFTERNOON STRONG SOUTHERLY OUTFLOW WINDS MOVED INTO THE AREA...
GUSTING OVER 30 MPH...AND SHIFTING THE PREDOMINANT WEST WIND TO A
SOUTH OR SOUTHEAST DIRECTION. HAVE EXPECTED WINDS TO RETURN BACK TO
THE WEST...AS ALL GUIDANCE HAS SUGGESTED...AFTER THE OUTFLOW WINDS
DISSIPATED BUT THIS HAS NOT HAPPENED AND CONFIDENCE IS NOW LOW THAT
WE WILL SEE A RETURN TO A WESTERLY COMPONENT LATER THIS
EVENING...ESPECIALLY AT KPHX. CANNOT RULE OUT WINDS LATER RETURNING
TO THE WEST DUE TO A LONG-TRAVELING OUTFLOW WIND GENERATED FROM
STORMS IN LA PAZ COUNTY...BUT WILL NOT PUT THIS POTENTIAL OUTCOME
INTO THE TAFS AT THIS TIME. THUS...HAVE REMOVED WEST WINDS FROM THE
PHOENIX TAFS FOR THE NEXT 6 HOURS.

LESS OF A THREAT FOR STORMS TOMORROW AFTERNOON/EVENING AS FLOW ALOFT
BECOMES MORE SOUTHWESTERLY AND STORMS THAT DEVELOP SHOULD REMAIN
OVER THE HIGHER TERRAIN EAST OF PHOENIX.

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

LITTLE TO NO AVIATION IMPACTS EXPECTED NEXT 24 HOURS AS FLOW ALOFT
BECOMES MORE SOUTHWESTERLY. SKIES TO BE GENLY CLEAR AT KIPL AND KBLH
THROUGH MONDAY EVENING. WINDS SHOULD CONTINUE TO FAVOR THE SOUTH
NEXT 24 HOURS AT KBLH...BECOMING LOCALLY GUSTY AGAIN MONDAY AFTN.
LESS CONFIDENCE WITH WINDS AT KIPL...THEY SHOULD FAVOR THE SOUTHEAST
LESS THAN 15KT BUT MAY BRIEFLY SWING TO THE WEST LATER THIS EVENING
AND PERSIST INTO THE MORNING HOURS BEFORE BECOMING LIGHT/VARIABLE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...
ATMOSPHERIC FLOW WILL BECOME MORE WESTERLY/SOUTHWESTERLY THROUGHOUT
THIS WEEK...PUSHING DEEP MOISTURE AND THUNDERSTORM CHANCES WELL TO
THE EAST OF PHOENIX OVER HIGHER TERRAIN LOCATIONS. EVEN THE
TYPICALLY ACTIVE REGIONS IN SOUTHERN GILA COUNTY MAY LACK
THUNDERSTORM DEVELOPMENT AND COVERAGE FOR MUCH OF THE WEEK.
AFTERNOON HUMIDITY LEVEL WILL RETREAT BACK INTO A 10-15 PERCENT
RANGE ACROSS LOWER ELEVATIONS WITH FAIR TO GOOD OVERNIGHT RECOVERY.
SOMEWHAT HIGHER HUMIDITY VALUES WILL BE EXPERIENCED IN MOUNTAIN
LOCATIONS. GENERALLY LIGHT AND DIURNALLY DRIVEN WINDS SPEEDS AND
DIRECTIONS WILL PREDOMINATE ALL WEEK...WITH SOMEWHAT MORE AFTERNOON
UPSLOPE GUSTINESS THAN IS TYPICAL DURING MONSOON SEASON.

&&

.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
AVIATION...CB
FIRE WEATHER...MO


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