307
FXUS65 KPSR 291019
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
319 AM MST SUN JUN 29 2025
KEY MESSAGES
- HOT AND DRY CONDITIONS WILL PERSIST THROUGH THE FIRST HALF OF
THE WEEK AS LOWER DESERT HIGH TEMPERATURES TOP OUT BETWEEN 110
AND 115 DEGREES THROUGH TUESDAY.
- EXTREME HEAT WARNINGS ARE IN EFFECT FOR THE PHOENIX METRO
STARTING TODAY THROUGH TUESDAY WITH THE WARNING IN EFFECT FOR
THE REST OF THE LOWER DESERTS MONDAY AND TUESDAY AS AREAS OF
MAJOR HEATRISK DEVELOP.
- AN INCREASE IN MOISTURE WILL LEAD TO INCREASED CHANCES OF
SHOWERS AND THUNDERSTORMS DURING THE MIDDLE AND LATTER HALF OF
THE WEEK ACROSS PORTIONS OF AZ, WITH THE BEST CHANCES FOR
ACTIVITY CONFINED ACROSS THE HIGHER TERRAIN AREAS.
DISCUSSION
THE MAIN FORECAST CONCERN THROUGH THE FIRST HALF OF THE WEEK WILL BE
THE EXTREME HEAT CONDITIONS EXPECTED TO MATERIALIZE AS A STRENGTHENING
SUBTROPICAL RIDGE WILL SET UP NEAR THE AZ/NM BORDER THROUGH
MONDAY AND NEAR THE FOUR CORNERS REGION BY TUESDAY WITH 500 MB
HEIGHT FIELDS INCREASING TO 591-594DM. THE STRENGTHENING RIDGE OF
HIGH PRESSURE IS AIDED IN PART BY AN UPPER-LEVEL LOW SITUATED OFF
THE WEST COAST OF SOUTHERN CA. AFTERNOON HIGH TEMPERATURES TODAY
ACROSS THE LOWER DESERTS WILL RANGE BETWEEN 111-114 DEGREES WITH
READINGS SLIGHTLY HOTTER ON MONDAY AS VALUES ARE EXPECTED TO PEAK
BETWEEN 112-116 DEGREES. AS A RESULT OF THESE TEMPERATURES, AREAS
OF MAJOR HEATRISK ARE EXPECTED TO MATERIALIZE WITH THE GREATEST
CONCENTRATION OF MAJOR HEATRISK EXPECTED FOR MAINLY THE PHOENIX
AREA TODAY AND THEN EXPANDING ACROSS THE REST OF THE LOWER DESERTS
AS WELL AS SOME OF THE HIGHER TERRAIN ZONES OF EASTERN MARICOPA
AND SOUTHERN GILA COUNTIES ON MONDAY. AS A RESULT, EXTREME HEAT
WARNINGS ARE IN EFFECT. FOR THE PHOENIX AREA, THERE IS A DECENT
SHOT (>60%) OF THE DAILY RECORD HIGH OF 115 DEGREES BEING
TIED/BROKEN ON MONDAY. TEMPERATURES ON TUESDAY ARE EXPECTED TO
SLIGHTLY DECREASE, HOWEVER, STILL HIGH ENOUGH FOR WIDESPREAD AREAS
OF MAJOR HEATRISK TO CONTINUE AND THUS THE EXTREME HEAT WARNINGS
HAVE BEEN EXTENDED FOR ALL OF THE LOWER DESERT LOCATIONS.
AS THE SUBTROPICAL RIDGE SETTLES ACROSS THE FOUR CORNERS REGION AND
THE AFOREMENTIONED UPPER-LEVEL LOW SETTLES NEAR THE SOUTHERN CA
COAST TUESDAY THROUGH EARLY WEDNESDAY, A SOUTH TO SOUTHEASTERLY FLOW
WILL SETTLE ACROSS MOST OF ARIZONA, HELPING TO ADVECT MODEST
MOISTURE NORTHWARD. THEREFORE, AN INCREASE IN SHOWER AND
THUNDERSTORM ACTIVITY IS LIKELY STARTING ON TUESDAY ACROSS THE
EASTERN ARIZONA HIGHER TERRAIN AREAS WITH BETTER COVERAGE ON
WEDNESDAY. ACTIVITY ACROSS THE HIGHER TERRAIN AREAS COULD DIRECT
SOME OUTFLOWS INTO THE LOWER DESERTS BOTH DAYS, ESPECIALLY DURING
THE EVENING HOURS, WITH GUSTY WINDS AND BLOWING DUST ACROSS THE
DUST PRONE AREAS.
THE MAIN CHALLENGE WITH THIS FORECAST AND ONE THAT IS STILL OF LOW
CONFIDENCE IS THE POTENTIAL FOR THUNDERSTORM ACTIVITY TO MATERIALIZE
ACROSS THE LOWER DESERTS OF SOUTH-CENTRAL AZ AS MOISTURE LEVELS ARE
EXPECTED TO BE MARGINAL AT BEST WITH THE LATEST EPS AND GEFS NOW
SHOWING PWATS ONLY PEAKING AT AROUND 1.2-1.3" FOR THE PHOENIX AREA.
THIS DOWNWARD TREND IN MOISTURE IS DUE TO THE LATEST TREND IN THE
MODEL GUIDANCE SHOWING THE UPPER-LEVEL LOW TRACKING FURTHER SOUTH
AND SLIGHTLY FASTER, DECREASING THE RESIDENCE TIME OF THE DEEPER
MOISTURE ADVECTION INTO THE REGION. NEVERTHELESS, THERE IS THE
POTENTIAL FOR SOME THUNDERSTORM ACTIVITY TO MATERIALIZE, ESPECIALLY
LATE WEDNESDAY NIGHT THROUGH THURSDAY AS THE UPPER-LEVEL FORCING
FROM THE JET ASSOCIATED WITH THE UPPER-LEVEL LOW APPROACHES FROM THE
WEST, WHICH MAY COMPENSATE FOR THE MARGINAL MOISTURE IN PLACE. IT IS
DURING THIS TIME FRAME OF WEDNESDAY NIGHT THROUGH THURSDAY WHEN NBM
POPS ARE AT ITS HIGHEST ACROSS THE LOWER DESERTS OF SOUTH-CENTRAL
AZ, RANGING BETWEEN 20-40%. AS THE TROUGH CONTINUES TO MOVE FURTHER
INLAND THROUGH MUCH OF THE DESERT SOUTHWEST, THE WESTERLY FLOW
ALOFT IS LIKELY TO SCOUR OUT MOST OF THE MOISTURE, LEADING TO A
DOWNWARD TREND IN MONSOONAL THUNDERSTORM ACTIVITY STARTING ON
FRIDAY AND LASTING INTO NEXT WEEKEND.
WITH THE DECREASING HEIGHTS ALOFT FROM THE INCOMING TROUGH,
TEMPERATURES DURING THE MIDDLE TO LATTER HALF OF THE WEEK ARE
EXPECTED TO TAKE A NOTICEABLE DOWNWARD TREND. FORECAST HIGHS BY
WEDNESDAY ARE EXPECTED TO BE NEAR NORMAL, BEFORE DROPPING A COUPLE
OF DEGREES BELOW NORMAL THURSDAY AND FRIDAY. THEREAFTER, AS THE
TROUGH LIFTS AWAY AND UPPER-LEVEL HEIGHT FIELDS START TO INCREASE
ONCE AGAIN BY NEXT WEEKEND, TEMPERATURES WILL BE ON SLIGHT UPWARD
TREND. THE GOOD NEWS IS THAT TEMPERATURES SHOULD REMAIN NEAR
NORMAL WITH NO EXTREME HEAT CONDITIONS EXPECTED THROUGH THE 4TH
OF JULY HOLIDAY WEEKEND.
AVIATION
UPDATED AT 0510Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, KDVT:
WESTERLY WINDS WILL CONTINUE INTO THE OVERNIGHT HOURS WITH SPEEDS
AOB 8 KT. WINDS AT KIWA WILL DO THEIR TYPICAL SHIFT TO SE'RLY
AROUND 10Z BEFORE GOING BACK WESTERLY LATE TOMORROW MORNING. AT
THE OTHER TAF SITES, WINDS MAY NOT GO FULLY EASTERLY OVERNIGHT AND
MAY JUST BE LIGHT AND VARIABLE. WESTERLY WINDS WILL REDEVELOP AT
ALL TAF SITES BY LATE TOMORROW MORNING/EARLY TOMORROW AFTERNOON.
GUSTS UP NEAR 20 KT ARE ANTICIPATED AGAIN TOMORROW AFTERNOON AND
EARLY EVENING. SKIES WILL REMAIN MOSTLY CLEAR WITH FEW CLOUDS AOA
10 KFT TOMORROW MORNING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
WESTERLY WINDS AT KIPL WILL GO LIGHT AND VARIABLE TOMORROW MORNING
AND THEN BECOME WESTERLY AGAIN TOMORROW NIGHT. AT KBLH, WINDS WILL
FAVOR A SW COMPONENT BEFORE GOING SOUTHERLY TOMORROW AFTERNOON
BEFORE GOING SOUTHWESTERLY AGAIN TOMORROW EVENING. WIND SPEEDS AT
BOTH TERMINALS WILL BE AOB 10 KT. SKIES WILL REMAIN MOSTLY CLEAR.
LOFTED SMOKE/HAZE MAY AT TIMES LOWER SLANTWISE VISIBILITY DURING
THE LATE AFTERNOON/EVENING HOURS, MAINLY AT KIPL.
FIRE WEATHER
VERY HOT AND DRY CONDITIONS WILL PERSIST DURING THE NEXT COUPLE OF
DAYS AS LOWER DESERT HIGHS EXCEED 110 DEGREES. MINRH VALUES
THROUGH MONDAY WILL RANGE BETWEEN 5-15% WITH POOR OVERNIGHT
RECOVERIES. THE OVERALL WIND PATTERN WILL CONTINUE TO FOLLOW THE
FAMILIAR DIURNAL TRENDS WITH THE TYPICAL AFTERNOON UPSLOPE
BREEZINESS. STARTING ON TUESDAY, INCREASING MOISTURE WILL LEAD TO
HIGHER RELATIVE HUMIDITIES AS WELL AS INCREASING CHANCES FOR
SHOWER AND THUNDERSTORM ACTIVITY ACROSS THE HIGHER TERRAIN AREAS.
THERE WILL BE SOME INITIAL CONCERNS FOR DRY LIGHTNING ACTIVITY
BEFORE A FURTHER INCREASE IN MOISTURE LEVELS LEADS TO A BETTER
POTENTIAL FOR WETTING RAINS LATER IN THE WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...EXTREME HEAT WARNING FROM 10 AM MONDAY TO 8 PM MST TUESDAY FOR
AZZ530>536-538-539-553-554-559.
EXTREME HEAT WARNING FROM 10 AM THIS MORNING TO 8 PM MST TUESDAY
FOR AZZ537-540-542>544-546-548-550-551.
EXTREME HEAT WARNING FROM 10 AM TO 8 PM MST MONDAY FOR AZZ541-
545-547-549-552-555-556-560>562.
CA...EXTREME HEAT WARNING FROM 10 AM MONDAY TO 8 PM PDT TUESDAY FOR
CAZ562-565>567-569-570.
DISCUSSION...LOJERO
AVIATION...BERISLAVICH
FIRE WEATHER...LOJERO
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