Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000
FXUS65 KPSR 011622
AFDPSR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
920 AM MST WED JUL 1 2015

.SYNOPSIS...
AFTER A RATHER ACTIVE EARLY WEEK START...SOMEWHAT MORE STABLE AIR
MOVING INTO THE REGION WILL REDUCE THUNDERSTORM ACTIVITY SOMEWHAT
OVER THE REGION TODAY. BUILDING HIGH PRESSURE ALONG WITH A SLIGHTLY
DRIER AIRMASS IS EXPECTED TO GRADUALLY REDUCE CONVECTIVE ACTIVITY
FURTHER FROM THURSDAY INTO SATURDAY. INCREASING SOUTHERLY FLOW ALOFT
ALONG WITH A RETURN OF MOISTURE WILL BRING BACK A BETTER CHANCE FOR
SHOWERS AND THUNDERSTORMS ON SUNDAY BEFORE ANOTHER SHIFT IN THE
UPPER PATTERN FROM THE SOUTHWEST TRENDS DOWN THUNDERSTORM POTENTIAL
EARLY NEXT WEEK.

&&

.DISCUSSION...
SCATTERED THUNDERSTORM ACTIVITY CONTINUES ALONG AND PARALLEL TO I-10
FROM ABOUT QUARTZSITE ALL THE WAY TO THE CWA BORDER AT JTNP AND NEAR
THERMAL/PALM SPRINGS THIS MORNING. REGIONAL SATELLITE IMAGERY THIS
AM SHOWS THE EXTENSIVE DEBRIS AND STORM CLOUDS OVER FAR WESTERN AZ
AND NEARLY THE SOUTHERN HALF OF CA...WITH SOME THINNING DEBRIS
FIELDS ACROSS SOUTH-CENTRAL AND SOUTHEAST AZ. ML/UL UPPER RIDGE
CIRCULATION CONTINUES TO MIGRATE TOWARDS THE FOUR CORNERS...WITH THE
300/250MB HIGH CENTERS NOW PLOTTED OVER NORTHERN NM...TRANSITION
FLOW ALOFT MORE SOUTHEASTERLY WITH ITS REPOSITIONING.

MORNING MODEL STREAMLINE FCSTS SHOW REMNANT MCV/300 MB INVERTED
TROUGH OVER SOUTHWEST AZ...WITH FAIRLY CONFLUENT SOUTHEASTERLY FLOW
UPSTREAM OVER NORTHERN MEXICO. THE 1.93 INCH READINGS ON THIS
MORNING`S KPSR BALLOON IS AT NEAR-RECORD LEVELS...BUT LIKELY
CONTAMINATED/WATER WEIGHTED AS PLENTY OF DEBRIS CLOUDINESS AND A
EVEN ROGUE SHOWER OR TWO REMAINED OVER THE AREA. 500-300MB WINDS
REMAIN ON THE ELEVATED SIDE...WITH 35-40KTS...BUT ARE FCST TO
GRADUALLY WEAKEN AS WE GET THROUGH THE DAY. FCST SOUNDINGS DROP
CAPES AT OR BELOW 800 J/KG READINGS BY THE AFTERNOON AND THERE IS
SOME QUESTION AS TO HOW WARM WE`LL GET TODAY TO HELP SUPPORT AND
EVEN FIRE CONVECTION OFF THE HIGHER TERRAIN. HI-RES AND
DETERMINISTIC MODELS KEEP ANY PRECIP ACTIVITY OF INTEREST GNLY ON
THE FCST AREA PERIPHERY THROUGH THE EVENING HOURS. THIS SOLUTION
SEEMS REASONABLE AND ALREADY REFLECTED IN THE GRIDS FOR TODAY...WITH
SLIGHT CHANCES ALREADY IN PLACE FOR THE AFTN/EVENING HOURS.

&&

.PREVIOUS DISCUSSION /ISSUED AT 310 AM MST/PDT/...
TODAY AND TONIGHT...
AFTER A RATHER ACTIVE DAY ON TUESDAY...WHEN A RATHER STRONG INVERTED
TROF MOVED WESTWARD ACROSS THE REGION...ALONG WITH A RATHER STRONG
JET MAX...WITH WINDS IN EXCESS OF 50 KNOTS IN THE 200-300MB
LAYER...AND A VERY UNSTABLE AIRMASS...WITH MIXED LAYER CAPES AOA
1000 J/KG...IT APPEARS THAT TODAY WILL BE SOMEWHAT QUIETER. THE
LATEST GFS MODEL OUTPUT IS SHOWING 200-300MB WINDS WILL DROP INTO
THE 15-20 KNOT WITH MIXED LAYER CAPES FALLING INTO THE 500-600 J/KG
RANGE ACROSS SOUTH-CENTRAL ARIZONA...WHICH REPRESENTS A SUBSTANTIAL
DECREASE IN INSTABILITY AND MID-HIGH LEVEL SHEAR WHEN COMPARED TO
TUESDAY. IN FACT...AFTER THIS MORNING...THE HI-RES ARW AND NMM
MODELS ARE ACTUALLY SHOWING A COMPLETE ABSENCE OF CONVECTIVE
ACTIVITY ACROSS OUR ENTIRE CWA TODAY. HOWEVER...GIVEN THE FACT THAT
PWATS WILL BE STILL ON THE HIGH SIDE...IN THE 1.40-1.60 INCH
RANGE...WITH SOME MODEST INSTABILITY REMAINING IN THE COLUMN...THE
CURRENT FEELING IS THAT THERE SHOULD BE AT LEAST SOME
SHOWER/THUNDERSTORM DEVELOPMENT THIS AFTERNOON ACROSS THE HIGHER
TERRAIN OF SOUTH-CENTRAL AZ TODAY...WITH ISOLATED STORMS PUSHING
THEIR WAY INTO THE LOWER DESERTS LATER THIS AFTERNOON/EVENING. THE
MAIN IMPACTS FROM THESE STORMS THIS AFTERNOON WILL BE LOCALLY GUSTY
WINDS AND HEAVY DOWNPOURS...WITH THE EXPECTED SLOWER STORM MOTION
INCREASING THE RISK OF LOCALIZED FLOODING SOMEWHAT. BLOWING DUST
SHOULD NOT BE A MAJOR PROBLEM WITH THE STORM MOTION STILL MORE FROM
A EAST-WEST DIRECTION RATHER THEN FROM A SOUTHEAST-NORTHWEST ONE.

THURSDAY THROUGH SATURDAY...
A FURTHER DECREASE IN SHOWER/THUNDERSTORM ACTIVITY IS EXPECTED
DURING THIS PERIOD...AS THE MAIN HIGH CENTER ALOFT REPOSITIONS
ITSELF RIGHT OVER OUR CWA...AND SOMEWHAT DRIER AIR FILTERS INTO THE
REGION...WITH PWATS FALLING INTO THE 1.20-1.40 INCH RANGE. THE
EXPECTATIONS FOR THE PERIOD AT THIS POINT IS THAT THE VAST MAJORITY
OF THUNDERSTORM ACTIVITY WILL BE CONFINED TO THE HIGHER TERRAIN
NORTH AND EAST OF PHOENIX...WITH MAINLY JUST SOME OUTFLOW ACTIVITY
FROM THESE STORMS MAKING THEIR WAY INTO THE LOWER DESERTS. ALTHOUGH
THERE WILL BE LESS CLOUDINESS AND MOISTURE AROUND DURING THIS
TIME...HIGH TEMPERATURES SHOULD NOT GET TOO FAR ABOVE NORMAL...AS
THE MAIN 500MB HIGH CENTER WEAKENS SOMEWHAT...WITH  HEIGHTS STAYING
MAINLY IN THE 590-292DM RANGE...LIKELY KEEPING HIGHS MAINLY AOB 110
ACROSS THE SOUTH-CENTRAL AZ LOWER DESERTS.

SUNDAY THROUGH WEDNESDAY...
BOTH THE GFS AND EURO MODELS ARE SHOWING A TEMPORARY INCREASE IN
SOUTHERLY FLOW ALOFT AHEAD OF AN UPPER TROF THAT IS EXPECTED TO
APPROACHING THE WEST COAST...WITH 200-300MB WINDS RISING AOA 40KTS
AND PWATS RISING SMARTLY INTO THE 1.60-1.80 INCH RANGE. THUS...A
SIGNIFICANT INCREASE IN THUNDERSTORM ACTIVITY IS QUITE LIKELY ON
SUNDAY...WITH SOME STORMS ONCE AGAIN BECOMING QUITE STRONG.
CONVECTIVE ACTIVITY IS THEN EXPECTED TO TAKE A DOWNWARD TREND FROM
MONDAY INTO NEXT WEDNESDAY AS THE FLOW ALOFT BECOMES MORE SW-
LY...AND BEGINS TO IMPORT SOMEWHAT DRIER AIR INTO THE REGION.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
THUNDERSTORM POTENTIAL WILL REMAIN THE BIGGEST AVIATION CONCERN
THROUGH LATE TONIGHT. ISOLD SHRA SHOULD REMAIN ON THE WEST SIDE OF
THE METRO THIS MORNING...THOUGH BE AS CLOSE AS LUKE AFB/WHITE TANKS.
REGARDLESS...CIGS SHOULD REMAIN ABOVE 10K FT. VERY LOW CONFIDENCE
FORECAST FOR THIS EVENING AND OVERNIGHT...WITH MOST MODEL OUTPUT
SUGGESTING NO ADDITIONAL THUNDERSTORM ACTIVITY. HOWEVER..WITH
MOISTURE IN PLACE...A ROGUE STORM IMPACTING ONE OF THE CNTRL
ARIZONA AERODROMES MAY BE POSSIBLE.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH...
SCT SHRA AND ISOLD TSRA WILL AFFECT PARTS OF SERN CALIFORNIA THROUGH
MUCH OF THE MORNING HOURS...AND POSSIBLY INTO THE AFTERNOON. WHILE
CIGS WILL REMAIN AOA 10K FT...ABRUPT WIND SHIFTS AND VERY LOCALIZED
TERRAIN OBSCURATION WILL BE POSSIBLE. SHOWERS SHOULD MOVE WELL AWAY
FROM TERMINALS BY LATE AFTERNOON...AND VERY LITTLE TO NO MODEL DATA
SUGGESTS REDEVELOPMENT THROUGH THURSDAY MORNING.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
THURSDAY THROUGH MONDAY...
A LOW GRADE MONSOON PATTERN WILL BE IN PLACE THROUGH THE WEEK...
CHARACTERIZED BY NEAR OR SLIGHTLY ABOVE NORMAL TEMPERATURES...AND
WIDELY SCATTERED AFTERNOON AND EVENING SHOWERS/THUNDERSTORMS THAT
MOVE FROM EAST TO WEST OFF THE MOUNTAINS AND INTO THE LOWER DESERTS
EACH DAY. FOR THURSDAY INTO SATURDAY THE STORMS WILL PRIMARILY FOCUS
OVER THE HIGHER TERRAIN WITH RATHER LOW CHANCES OF SURVIVING INTO
THE LOWER DESERTS. SUNDAY INTO EARLY NEXT WEEK...AS HUMIDITIES RISE
THERE WILL BE A BETTER CHANCE OF THUNDERSTORMS AND SHOWERS MOVING
INTO THE CENTRAL DESERTS DURING THE OVERNIGHT HOURS. DAYTIME
HUMIDITY VALUES GENERALLY WILL BE IN THE UPPER TEENS TO MID 20
PERCENT RANGE THROUGH SATURDAY WITH HUMIDITIES RISING SEVERAL
PERCENT BY MONDAY. VERY GOOD OVERNIGHT RECOVERY IS EXPECTED EACH
NIGHT. WINDS EACH DAY WILL BE LIGHT AND FAVOR SOUTHWESTERLY
DIRECTIONS THROUGH FRIDAY...BECOMING SOUTHERLY BY THE WEEKEND.

&&

.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...NOLTE
PREVIOUS DISCUSSION...PERCHA
AVIATION...MO
FIRE WEATHER...CB



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