Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 031510
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
805 AM MST MON AUG 3 2015

.SYNOPSIS...
MUCH DRIER WEATHER IS IN STORE THROUGH MIDWEEK...WITH STORM CHANCES
CONFINED TO THE HIGHER TERRAIN EAST OF PHOENIX. HOT TEMPERATURES ARE
EXPECTED THROUGH WEDNESDAY...WITH HIGHS AROUND 110 DEGREES ACROSS
THE DESERTS OF SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA. MODEST
MONSOONAL MOISTURE MAY RETURN TO THE REGION LATE IN THE WEEK
ALLOWING FOR AN UPTICK IN SHOWER AND THUNDERSTORM CHANCES ACROSS THE
SOUTH-CENTRAL ARIZONA DESERTS.

&&

.DISCUSSION...
A STABLE AND DRIER AIRMASS WILL CONTINUE TO SPREAD ACROSS OUR
FORECAST AREA...SOUTHEAST CA TO SOUTH CENTRAL AZ...THROUGH TUESDAY
PRECLUDING ANY AFTN TSTM ACTIVITY.

REGIONAL WEATHER BALLOON ANALYSIS SHOWED THE MONSOON MOISTURE
BOUNDARY...I.E. 8 DEG C 800 MB DEWPOINT...YESTERDAY EXTENDED IN WIDE
PLUME WITH ITS AXIS EXTENDING FROM LAS TO PHX AND TUS.  THIS MORNING
THIS BOUNDARY HAD SHIFTED EAST AND SOUTH...AND NOW EXTENDS FROM
TUCSON SOUTH INTO NORTHWEST MEXICO. IN OTHER WORDS...BOUNDARY LAYER
DRYING HAS TAKEN PLACE ACROSS MOST OF AZ THIS MORNING.

THIS ASIDE...BASED ON THE CURRENT BOUNDARY LAYER MOISTURE LEVELS...
AFTN CONVECTIVE TRIGGER TEMPERATURES ACROSS VARIOUS TERRAIN
ELEVATIONS OVER THE SOUTHEAST QUARTER OF THE STATE...FROM 1200
FT TO 6 THSD FT MSL...WERE AT FORECAST HIGH TEMPERATURES FOR
THE DAY. ON TOP OF THIS...UPPER LEVEL WINDS WERE TRENDING
TOWARD STRONG ANTI-CYCLONIC SHEAR. THE BUILDING RIDGE SNUFFING OUT
ANY CHANCE OF AFTERNOON MTN STORMS TODAY.  DITTO ON TUESDAY AS 500
MB TEMPS ARE FORECAST TO WARM FROM MINUS 6 DEG C TODAY...WHICH IS
NORMAL...TO MINUS 4 DEG C TUESDAY.

CURRENT DRY FORECASTS LOOK GOOD THROUGH TUESDAY. NO UPDATES PLANNED.
PREVIOUS DISCUSSION BELOW STILL APPLIES.



.PREVIOUS DISCUSSION...515 AM MST...

IR SATELLITE IMAGERY SHOWS WHAT IS LEFT OF ANY STORM ACTIVITY
CONFINED TO FAR SOUTHEAST ARIZONA THIS MORNING. A MUCH DRIER
SUBSIDENT ATMOSPHERE IS IN PLACE OVER SE CALIFORNIA AND SW ARIZONA
IN THE WAKE OF A WEAK SHORT WAVE THAT MOVED THROUGH THE REGION
YESTERDAY AFTERNOON. WITH THE DRIER SOUTHWESTERLY-WESTERLY FLOW
ALOFT...PRECIPITABLE WATER VALUES DROPPED EVEN FURTHER TO JUST SHY
OF AN INCH IN THE 00Z KPSR SOUNDING -- CONDITIONS ARE NOT VERY
FAVORABLE FOR AFTERNOON/EVENING THUNDERSTORMS OVER SOUTH-CENTRAL
TODAY. PRECIPITATION CHANCES...ALBEIT SLIGHT...WILL BE FOCUSED OVER
THE HIGHER TERRAIN ELEVATIONS WELL NORTH AND EAST OF PHOENIX FOR THE
NEXT COUPLE OF DAYS.

THE LATEST GFS/NAM STILL CONTINUE TO SUGGEST FURTHER DRYING TUESDAY
AND WEDNESDAY AS THE UPPER LEVEL RIDGE THAT IS CURRENTLY FLATTENED
AND STRETCHED ACROSS NORTHERN MEXICO INTO TEXAS BEGINS TO SHIFT AND
POSITION A 594-596DM 500MB HEIGHTS BACK OVER ARIZONA. THE DRIER
PATTERN WILL ALLOW TEMPERATURES TO RISE ABOVE SEASONAL NORMALS. SOME
OF THE WARMEST GUIDANCE...INCLUDING THE ECMWF/GFS...INTRODUCE TEMPS
THAT ARE PRETTY HOT -- IN THE 110 TO 115 RANGE -- FOR SOME LOWER
DESERTS SITES. WITH FURTHER DRYING OF THE ATMOSPHERE THESE TEMPS
COULD EASILY BE ACHIEVED TUESDAY AND WEDNESDAY. RIGHT NOW...THE
WARMEST DAYTIME HIGHS ARE FORECAST FOR SOUTHEAST CALIFORNIA AND THE
SOUTHWEST ARIZONA DESERTS THROUGH MIDWEEK.

AS THE HIGH REPOSITIONS...THERE WILL BE WINDOWS OF OPPORTUNITY FOR
LOW-MID LEVEL MOISTURE TO BEGIN SNEAKING BACK INTO THE REGION. A
GOOD INTRUSION OF MOISTURE MIGHT BE JUST ENOUGH TO KNOCK A DEGREE OR
TWO OFF DAYTIME HIGHS...BUT ANY HUMIDITY INCREASE WILL KEEP THOSE
OVERNIGHT LOWS QUITE WARM. OVERALL -- IT WILL BE HOT -- SO WILL BE
ENCOURAGING THE PUBLIC THROUGH SOCIAL MEDIA CHANNELS TO STAY COOL
AND HYDRATED OVER THE NEXT FEW DAYS.

BY THURSDAY AND FRIDAY...MOISTURE MAKES A MORE SUBSTANTIAL RETURN...
AND LOW LEVEL WIND FLOW RETURNS TO A SOUTH-SOUTHEASTERLY DIRECTION.
AS SUCH...STORM CHANCES ARE SLATED TO GRADUALLY IMPROVE INTO THE
WEEKEND.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH...

DRY WESTERLY FLOW ALOFT WILL CONTINUE TO OVERSPREAD THE AREA TODAY
INTO TUESDAY KEEPING SKIES GENERALLY CLEAR. THERE MAY BE A FEW HIGH
BASED CUMULUS IN THE CENTRAL DESERTS THIS AFTERNOON AND EARLY
EVENING BUT THEY WILL MAINLY STAY ON THE NORTHERN AND EASTERN
FRINGES OF THE GREATER PHOENIX AREA. WINDS WILL FAVOR NORMAL DIURNAL
TENDENCIES IN THE CENTRAL DESERTS...WITH WEST WINDS DEVELOPING AFTER
NOON...AND PERSISTING WELL INTO THE OVERNIGHT HOURS. NO AVIATION
CONCERNS FOR ANY OF THE TERMINALS OVER THE NEXT 24 HOURS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
WEDNESDAY THROUGH SUNDAY...DRY AND STABLE FLOW ALOFT WEDNESDAY WILL
TRANSITION INTO A WEAK MONSOON PATTERN WHERE MOISTURE FROM MEXICO
WILL RETURN MAINLY TO CENTRAL AND EASTERN ARIZONA. A SLIGHT CHANCE
OF AFTERNOON AND EARLY EVENING SHOWERS AND THUNDERSTORMS WILL RETURN
TO SOUTH CENTRAL ARIZONA THURSDAY THROUGH SUNDAY WITH THE BEST
CHANCES FOR STORMS TO FOCUS OVER HIGHER TERRAIN AREAS EAST OF
PHOENIX. MINIMUM RELATIVE HUMIDITIES WILL INCREASE GENERALLY INTO
THE 15 TO 20 PERCENT RANGE...EXCEPT NEAR 30 PERCENT IN THE MOUNTAINS
OF SOUTHERN GILA COUNTY...WITH SOME DRYING AGAIN FROM THE WEST
EXPECTED OVER THE WEEKEND AS HUMIDITIES OVER THE WESTERN AND CENTRAL
DESERTS FALL BELOW 15 PERCENT BY SUNDAY. ABOVE NORMAL HIGH
TEMPERATURES THROUGH THURSDAY WILL COOL TO AROUND SEASONAL NORMALS
FRIDAY THROUGH THE END OF THE WEEK. TYPICAL DIURNAL SOUTHWEST WINDS
10 TO 15 MPH WILL DEVELOP DURING THE AFTERNOONS. FAIR OVERNIGHT
RECOVERY.

&&

.SPOTTER INFORMATION STATEMENT... SPOTTERS ARE ENCOURAGED TO REPORT
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...VASQUEZ/MEYERS
AVIATION...CB
FIRE WEATHER...VASQUEZ/CB



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