747
FXUS65 KPSR 131752
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1052 AM MST THU AUG 13 2020
UPDATE
UPDATED AVIATION DISCUSSION.
SYNOPSIS
STRONG HIGH PRESSURE WILL REMAIN SITUATED ACROSS THE SOUTHWESTERN
U.S. INTO NEXT WEEK BRINGING CONTINUED HOT CONDITIONS. HIGH
TEMPERATURES ACROSS THE LOWER DESERTS WILL APPROACH OR EXCEED 115
DEGREES STARTING TODAY AND LASTING THROUGH AT LEAST EARLY NEXT
WEEK. ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE TODAY BEFORE
CHANCES DECREASE TOMORROW. POTENTIAL FOR A SLIGHTLY BETTER
MONSOON SET-UP THIS WEEKEND OR EARLY NEXT WEEK.
DISCUSSION
STRONG HIGH PRESSURE OVER SOUTHERN NEW MEXICO WILL CONTINUE TO
STRENGTHEN AND PROGRESS NORTHWESTWARD, POSITIONING ITSELF OVER US
FRIDAY AND NEAR THE NEVADA/UTAH BORDER BY SUNDAY. THE CENTER OF
THE HIGH THEN APPEARS TO SLOWLY DRIFT BACK SOUTH TOWARDS THE
MIDDLE OF NEXT WEEK. THIS WILL KEEP VERY WARM TEMPERATURES IN
PLACE, WITH HIGHS APPROACHING OR EXCEEDING 115 DEGREES EACH DAY.
THE EXCESSIVE HEAT WARNING WILL EXPAND AND COVER THE ENTIRE
FORECAST AREA BY TOMORROW AND WILL REMAIN IN EFFECT THROUGH
MONDAY.
IN TERMS OF MOISTURE, SOUTH-SOUTHWEST FLOW ON THE WESTERN
PERIPHERY OF THE HIGH IS CURRENTLY STREAMING IN THICKER MID- AND
UPPER-LEVEL MOISTURE. THIS IS ADVECTING THICKER CLOUDS, EMBEDDED
WITH ISOLATED VIRGA, INTO OUR FORECAST AREA. THESE THICKER CLOUDS
WILL LIKELY PROHIBIT TEMPERATURES FROM DROPPING TOO MUCH
OVERNIGHT, WITH PHOENIX LIKELY ADDING ANOTHER 90 DEGREE OR ABOVE
LOW TEMPERATURE TO THE TALLY. 1 INCH OR GREATER PWS WILL BE LIKELY
AGAIN TODAY, WITH THE GREATEST VALUES ACROSS THE WESTERN PORTIONS
OF MARICOPA & PINAL COUNTIES WESTWARD INTO THE COLORADO RIVER
VALLEY. BEST STORM COVERAGE WILL BE IN THIS AREA, AS WELL AS
ACROSS THE MOUNTAINOUS TERRAIN NORTH, SOUTH, AND EAST OF PHOENIX.
ANY SHOWER OR STORM THAT MANAGES TO DEVELOP WILL BE BRIEF AND BE
CAPABLE OF PRODUCING LIGHTING, GUSTY ERRATIC WINDS, HEAVY RAIN,
AND BLOWING DUST.
AS HIGH PRESSURE MOVES OVERHEAD TOMORROW, STORM CHANCES WILL
DECREASE A BIT DUE TO A MORE STABLE AIRMASS A LOFT. HOWEVER, IT
DOES APPEAR THAT ONCE THE CENTER OF THE HIGH IS NORTH OF US,
PRETTY MUCH SATURDAY ONWARD, THERE WILL BE A MORE FAVORABLE
PATTERN ALOFT THAT COULD POTENTIALLY DRIVE SOME STORMS INTO THE
LOWER DESERTS, ESPECIALLY ON SUNDAY. ON SUNDAY, THERE CURRENTLY APPEARS
TO BE BETTER POTENTIAL FOR A STRONGER OUTFLOW TO PUSH IN FROM THE
EAST AND INTERACT WITH A MOIST AND UNSTABLE ATMOSPHERE IN THE
LOWER DESERTS AND POSSIBLY REGENERATE NEW STORMS. DUE TO THIS
POTENTIAL FOR STORMS ON SUNDAY, THE NBM IS SHOWING A DECENT SPREAD
IN THE HIGH TEMPERATURE FORECAST. WE WILL CONTINUE TO MONITOR THE
SITUATION, ANY LITTLE CHANGE IN THE FORECASTED POSITION OF THE
HIGH, COULD LEAD TO STORM CHANCES SHIFTING TO ANOTHER DAY. DUE TO
THE UNCERTAINTIES, THE EXCESSIVE HEAT WARNING WAS NOT EXTENDED
INTO THE MIDDLE OF NEXT WEEK AT THIS TIME. HOWEVER, IF
TEMPERATURES CONTINUE TO TREND AS WARM AS THEY HAVE BEEN TRENDING,
THE WARNING MAY NEED TO BE EXTENDED.
AVIATION
UPDATED AT 1750Z.
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
WINDS WILL REMAIN VERY LIGHT AND OFTEN VARIABLE FOR THE NEXT FEW
HOURS BEFORE BECOMING PREDOMINANTLY WESTERLY BETWEEN 19-21Z. WINDS
ARE LIKELY TO REMAIN WESTERLY THROUGH THE EVENING WITH THE
NIGHTLY EASTERLY WINDS OCCURRING A FEW HOURS AFTER SUNSET.
OCCASIONAL AFTERNOON BREEZES OF 15-20 KTS ARE POSSIBLE. AFTERNOON
THUNDERSTORMS ARE FAVORED TO REMAIN SOUTH AND NORTH OF THE
TERMINAL AREA. HOWEVER, THERE IS A 20-30% CHANCE ISOLATED
THUNDERSTORMS COULD FORM OVER WESTERN MARICOPA COUNTY, INCLUDING
THE WESTERN HALF OF THE PHOENIX AREA. FOR NOW, CONFIDENCE IN
STORMS DIRECTLY IMPACTING ANY PARTICULAR TERMINAL IS TOO LOW TO
MENTION IN THE TAFS, BUT OF ALL THE SITES, KDVT AND KSDL SEEM THE
MOST LIKELY TO SEE STORMS (LESS THAN 20% CHANCE). IF THESE STORMS
DO DEVELOP, ANY OUTFLOWS WOULD LIKELY REINFORCE THE WESTERLY WINDS
AT STRONGER SPEEDS THAN WHAT IS CURRENTLY IN THE TAFS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
FOR KIPL, WINDS ARE EXPECTED TO FOLLOW TYPICAL DIURNAL TRENDS AT
SPEEDS MOSTLY AOB 10 KTS. AT KBLH, WINDS WILL BECOME WESTERLY BY
THE LATE AFTERNOON AND THEN SOUTHERLY DURING THE OVERNIGHT HOURS,
ESPECIALLY IF OUTFLOWS FROM DISTANT THUNDERSTORMS CAN REACH THE
AREA. OTHERWISE, THERE MAY ALSO BE EXTENDED PERIODS OF A
LIGHT/VARIABLE WIND AT BOTH SITES.
FIRE WEATHER
SATURDAY THROUGH WEDNESDAY:
VERY HOT TEMPERATURES AND OVERALL DRY CONDITIONS WILL PERSIST
THROUGH THE MIDDLE OF NEXT WEEK. MINIMUM HUMIDITIES THROUGH THE
PERIOD WILL DROP INTO THE TEENS EACH DAY WITH OVERNIGHT RECOVERIES
GENERALLY BETWEEN 25-50%. WINDS WILL GENERALLY FOLLOW TYPICAL
DIURNAL/TERRAIN INFLUENCES WITH SPEEDS REMAINING LIGHT ASIDE FROM
SOME TYPICAL AFTERNOON BREEZES. THUNDERSTORM ACTIVITY WILL BE
LIMITED WITH ISOLATED STORMS POSSIBLE BUT FAVORING THE HIGH
TERRAIN.
CLIMATE
RECORD HIGH TEMPERATURES:
DATE PHOENIX YUMA EL CENTRO
---- ------- ---- ---------
8/13 115 IN 2012 117 IN 2012 116 IN 2012
8/14 117 IN 2015 115 IN 2019 116 IN 2015
8/15 115 IN 2015 117 IN 2015 118 IN 2019
8/16 113 IN 2013 115 IN 1992 117 IN 2016
8/17 114 IN 2013 114 IN 1992 115 IN 2015
8/18 112 IN 2011 116 IN 1960 115 IN 2015
SPOTTER INFORMATION STATEMENT
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXCESSIVE HEAT WARNING UNTIL 8 PM MST MONDAY FOR AZZ530>556-
559>562.
HEAT ADVISORY UNTIL 8 PM MST MONDAY FOR AZZ557-558-563.
CA...EXCESSIVE HEAT WARNING UNTIL 8 PM PDT MONDAY FOR CAZ565>567-569-
570.
EXCESSIVE HEAT WARNING FROM 10 AM FRIDAY TO 8 PM PDT MONDAY FOR
CAZ560>564-568.
DISCUSSION...FELDKIRCHER
AVIATION...ROGERS/MO
FIRE WEATHER...FELDKIRCHER
CLIMATE...MO
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