Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 152228
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
330 PM MST MON SEP 15 2014

.SYNOPSIS...
ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE ACROSS THE REGION
TODAY ALONG WITH SOME AREAS OF BLOWING DUST. HOWEVER...MOISTURE WILL
INCREASE SUBSTANTIALLY ACROSS THE AREA ON TUESDAY AND THERE WILL BE
AN ELEVATED RISK OF HEAVY RAIN AND FLOODING ACROSS THE AREA THROUGH
THE END OF THE WEEK.

&&

.DISCUSSION...
CONSENSUS OF CONVECTIVE-ALLOWING MODELS STILL SUGGESTS SHOWER AND
THUNDERSTORM ACTIVITY WILL REMAIN CONCENTRATED ACROSS SOUTHERN AZ
AND ALONG THE MOGOLLON RIM LATE THIS AFTERNOON AND THIS EVENING.
LATEST SPC MESOANALYSIS SHOWS 500-1000 J/KG OF CAPE ACROSS EASTERN
GILA COUNTY WITH SIGNIFICANT INHIBITION NOTED FURTHER WEST ACROSS
THE LOWER DESERTS OF YUMA AND SOUTHERN MARICOPA COUNTIES. LATEST
HRRR ALSO SHOWS SOME POTENTIAL FOR CONVECTION ACROSS MARICOPA AND
PINAL COUNTIES THIS EVENING AND EVEN AFTER MIDNIGHT...LIKELY AIDED
BY THE LOW-LEVEL CONVERGENCE ASSOCIATED WITH AN APPROACHING OUTFLOW
BOUNDARY DROPPING SOUTHWESTWARD FROM THE HIGHER TERRAIN AND THE
SURGE OF TROPICAL MOISTURE LIFTING NORTHWARD FROM SOUTHERN AZ.

ANY STORMS THAT DEVELOP ACROSS SOUTHERN AZ ALSO HAVE THE POTENTIAL
TO PRODUCE AREAS OF BLOWING DUST. HI-RES WRFS SUGGEST THAT CLOUDS
AND SHOWER ACTIVITY MAY ALSO LINGER INTO TUESDAY AND POPS WERE
INCREASED TUESDAY MORNING...THOUGH ANY RAIN THAT DEVELOPS WILL
LIKELY BE QUITE LIGHT. FOCUS INSTEAD REMAINS ON THE POTENTIAL FOR
HEAVY RAIN LATER THIS WEEK.

&&

.PREVIOUS DISCUSSION...
OBVIOUSLY THE MAIN FOCUS OF THE FORECAST IS ON THE IMPACTS
ASSOCIATED WITH HURRICANE ODILE. THE SURGE OF MOISTURE WILL OCCUR
LATE TONIGHT /FOLLOWING THIS EVENING`S DECAYING STORMS/ AND PWATS
WILL SKYROCKET CLOSE TO 2 INCHES BY TUESDAY MORNING. THESE VALUES
WOULD NORMALLY BE UNHEARD OF FOR SEPTEMBER...EXCEPT WE SAW SIMILAR
VALUES JUST LAST WEEK. ELEVATED PWATS WILL REMAIN ACROSS THE REGION
THROUGH AT LEAST THURSDAY...IF NOT INTO FRIDAY WHEN A LARGER SCALE
TROUGH USHERS IN SOUTHWESTERLY FLOW ALOFT. IF ANYTHING HAS CHANGED
WITH RECENT MODEL RUNS...IT WOULD APPEAR THE AXIS OF HIGHEST
MOISTURE HAS SHIFTED A BIT TO THE EAST. WHERE THE AXIS WAS ONCE
POSITIONED SQUARELY OVER THE COLORADO RIVER...ITS NOW SPREAD OVER A
GOOD PORTION OF SOUTH-CENTRAL ARIZONA. AS USUAL...TRYING TO PINPOINT
THE EXACT TIMING/PLACEMENT OF THE HEAVIEST RAIN IS NEARLY IMPOSSIBLE
WITH TROPICAL SYSTEMS. THE 00Z RUNS OF THE ECMWF AND GFS BOTH SEEM
TO INDICATE A SHORTWAVE TROUGH MOVING THROUGH THE AREA ON WEDNESDAY
/PERHAPS AS EARLY AS WEDNESDAY MORNING/...WITH A SECONDARY TROUGH
SWEEPING THROUGH THURSDAY. I HAVE INCREASED POPS DURING THIS TIME
AND WILL HIGHLIGHT THESE TIMES AS THE MOST LIKELY TO SEE HEAVY
RAINFALL/FLOODING IMPACTS.

EVENTUALLY A LARGE SCALE TROUGH WILL MOVE THROUGH CALIFORNIA LATE IN
THE WEEK AND BEGIN ADVECTING SOMEWHAT DRIER AIR INTO THE REGION FROM
THE WEST. BOTH THE ECMWF AND GFS INDICATE STRONG SOUTHWESTERLY FLOW
AND A SHORTWAVE TROUGH MOVING THROUGH ON FRIDAY...WHICH WOULD LIKELY
RESULT IN ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS MAINLY EAST OF
THE COLORADO RIVER. THE EMPHASIS LATE IN THE WEEK WOULD SHIFT TO THE
NORTH/EAST OF PHOENIX GIVEN FAVORABLE UPSLOPE FLOW ALTHOUGH
SCATTERED SHOWERS WOULD STILL BE POSSIBLE ACROSS THE DESERTS. IT
LOOKS LIKE THE DEEPEST PWATS SHOULD BE ADVECTED EAST OF ARIZONA THIS
WEEKEND BUT UNTIL THEN...I KEPT POPS WELL ABOVE CLIMATOLOGICAL
NORMALS UNTIL SUNDAY.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
MODELS STILL SUGGEST SFC WINDS WILL TURN TO A W/NW DIRECTION JUST
BEFORE SUNSET...THOUGH MAY REMAIN VRBL FOR EXTENDED PERIODS.
CONFIDENCE IS WANING THAT MORE ORGANIZED SE OUTFLOW WILL IMPACT
TERMINALS...INSTEAD POSSIBLY A WEAKER OUTFLOW FROM THE NE MOVING
INTO THE PHOENIX METRO. REGARDLESS...A SUBSTANTIAL INCREASE IN
MOISTURE OVERNIGHT MAY LEAD TO REDUCED SLANTWISE VSBY TUESDAY
MORNING WITH MORE EXTENSIVE DEBRIS CLOUDS WITH CIGS AS LOW AS 7K FT
WITH POSSIBLE VIRGA. THOUGH CONFIDENCE IS STILL LOW...A FEW
SHRA/TSRA MAY BE POSSIBLE EVEN AS EARLY AS LATE TUESDAY MORNING.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
NO SIGNIFICANT AVIATION IMPACTS EXPECTED THROUGH TUESDAY AFTERNOON
AS SHRA/TSRA SHOULD REMAIN WELL SOUTH AND EAST OF SERN CALIFORNIA
TERMINALS. HOWEVER...THERE MAY BE A PERIOD OF GUSTY SOUTH WINDS
OVERNIGHT (ESPECIALLY AT KBLH) ASSOCIATED WITH A SURGE OF A VERY
HUMID AIRMASS FROM THE GULF OF CALIFORNIA. THOUGH CONFIDENCE IS
LOW...THERE MAY BE AREAS OF CIGS NEAR THE 3K FT MVFR THRESHOLD
TUESDAY MORNING IN COMBINATION WITH THE GULF SURGE.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
UNUSUALLY WET CONDITIONS WILL BE LIKELY THURSDAY AND FRIDAY ACROSS
ARIZONA...WITH THE POTENTIAL FOR SOMEWHAT LESS ACTIVITY OVER SERN
CALIFORNIA. SEVERAL AREAS COULD EXPERIENCE HEAVY RAINFALL AND
LOCALIZED FLOODING AS A RESULT. SHOWERS AND THUNDERSTORMS SHOULD
BECOME LESS NUMEROUS OVER THE WEEKEND...THOUGH WILL STILL LIKELY
PREVAIL OVER PARTS OF CNTRL ARIZONA. WITH THE VERY MOIST
CONDITIONS...AFTERNOON HUMIDITY VALUES WILL ONLY FALL INTO A 20-40
PERCENT RANGE WITH EXCELLENT OVERNIGHT RECOVERY. WINDS WILL
GENERALLY FAVOR A SOUTHERLY DIRECTION AND COULD BECOME GUSTY AROUND
THUNDERSTORMS.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...

AZ...FLASH FLOOD WATCH FROM WEDNESDAY MORNING THROUGH THURSDAY
     AFTERNOON AZZ021>024-027-028.

CA...NONE.

&&

$$

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

DISCUSSION...HIRSCH
PREVIOUS DISCUSSION...LEINS
AVIATION...MO
FIRE WEATHER...MO




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