967
FXUS65 KPSR 251715
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
1015 AM MST SUN OCT 25 2026
UPDATE
UPDATED 18Z AVIATION DISCUSSION.
KEY MESSAGES
- TEMPERATURES FOR THE UPCOMING WEEK WILL GENERALLY BE WITHIN THE
NORMAL RANGE FOR LATE OCTOBER WITH LOWER DESERT HIGHS MOSTLY IN
THE MID EIGHTIES.
- DRY AND TRANQUIL WEATHER CONDITIONS WILL LAST THROUGH THE MIDDLE
OF WEEK.
- A RETURN TO INCLEMENT WEATHER WITH INCREASED RAINFALL CHANCES IS
LIKELY TOWARDS THE END OF THE WEEK.
SHORT TERM /TODAY THROUGH WEDNESDAY/
THE CENTER OF THE UPPER LOW THAT BROUGHT SOME SCATTERED SHOWERS
AND A FEW THUNDERSTORMS ON SATURDAY IS STILL HANGING OUT OVER
ARIZONA, BUT MORE OVER NORTHERN PORTIONS OF THE STATE. AS IT
CONTINUES TO WEAKEN AND LIFT NORTHEASTWARD TODAY, ANY RAIN
CHANCES WILL EXIST ONLY ACROSS NORTHEASTERN ARIZONA. DRIER AIR
WILL ALSO FILL BACK IN FROM THE SOUTHWEST TODAY WITH GENERALLY
CLEAR SKIES ACROSS THE LOWER DESERTS. TEMPERATURES WILL ALSO BEGIN
TO TREND UPWARD WITH THE EXITING OF THE UPPER LOW WITH READINGS
INTO THE LOWER 80S FOR PHOENIX TO AROUND 85 DEGREES IN YUMA AND EL
CENTRO.
A QUIET WEATHER PATTERN WILL THEN STAY OVER THE SOUTHWESTERN U.S.
DURING THE FIRST HALF OF THIS WEEK WITH QUASI-ZONAL WESTERLY DRY
FLOW LASTING THROUGH WEDNESDAY. UPPER LEVEL HEIGHTS WILL ALSO
STAY NEAR NORMAL OVER THE NEXT SEVERAL DAYS ALLOWING NEAR NORMAL
TEMPERATURES UNDER CLEAR TO MOSTLY CLEAR SKIES. NBM FORECAST HIGHS
DO SHOW READINGS NUDGING A BIT MORE TOWARD THE UPPER 80S FOR
TUESDAY AND WEDNESDAY, BUT THERE IS CURRENTLY ONLY A 25% CHANCE
(FOR KPHX) AT REACHING 90 DEGREES THIS WEEK.
LONG TERM /THURSDAY THROUGH NEXT SUNDAY/
MODELS CONTINUE TO SUGGEST A MORE ORGANIZED LARGE SCALE TROUGHING
PATTERN SETTING UP LATER THIS WEEK WITH THE PARENT LOW SETTING UP
ALONG THE BRITISH COLOMBIA COAST BEFORE DIVING SOUTHWARD INTO THE
PACIFIC NORTHWEST BY THURSDAY. A SECONDARY SHORTWAVE OR WEAK
CLOSED LOW MAY ALSO FORM WEST OF CALIFORNIA WEDNESDAY INTO
THURSDAY, MORE ASSOCIATED WITH THE SUB-TROPICAL JET. WHAT IS
LIKELY TO BE MORE IMPORTANT IS THE EVENTUAL PHASING OF THE POLAR
JET OVER THE PACIFIC NORTHWEST WITH THE STRONGER SUBTROPICAL JET
BY NEXT FRIDAY. BOTH THE EPS AND GEFS SUPPORT THIS PHASING, WHILE
ALSO STRENGTHENING THE SUBTROPICAL JET TO NEAR RECORD STRENGTH
FOR THIS TIME OF YEAR JUST WEST OF BAJA ON FRIDAY. GUIDANCE THEN
SUPPORTS A FAIRLY STRONG WEATHER SYSTEM (WITH H5 HEIGHTS WITHIN
THE 10TH PERCENTILE OF CLIMATOLOGY) DEVELOPING WITHIN THE BASE OF
THE TROUGH BY NEXT WEEKEND. ALTHOUGH WE ARE AT AROUND 5-7 DAYS
OUT FROM THIS NEXT EXPECTED WEATHER EVENT, THERE IS ENOUGH MODEL
EVIDENCE FOR US TO BEGIN WORRYING ABOUT ANOTHER SIGNIFICANT
PRECIPITATION EVENT. A BIT MORE THAN 50% OF THE ENSEMBLE MEMBERS
FAVOR THE TROUGH DEEPENING JUST OFF THE WEST COAST FRIDAY INTO
NEXT WEEKEND, LIKELY PUSHING A MODEST TO STRONG ATMOSPHERIC RIVER
(AR) SOMEWHERE INTO THE SOUTHWESTERN U.S. NEXT WEEKEND.
AS THE TROUGH FIRST BEGINS TO SET UP DURING THE MIDDLE PART OF THE
WEEK, THERE IS HIGH CONFIDENCE IN STRONG NORTHWARD MOISTURE
ADVECTION IN THE UPPER LEVELS OUT OF MEXICO WEDNESDAY NIGHT INTO
THURSDAY. THIS SHOULD BE FOLLOWED BY LOWER LEVEL MOISTURE
ADVECTION LATER THURSDAY INTO FRIDAY. ALTHOUGH THE TIMING MAY
CHANGE AND ASSUMING THE POSITIONING OF THE SUBTROPICAL JET IS
CORRECT, SHOWER CHANCES MAY BEGIN AS EARLY AS LATE THURSDAY AND
CARRY INTO FRIDAY UNDER BROAD DIVERGENCE ALOFT AND MODEST UPSLOPE
SOUTHERLY FLOW. THIS FIRST PERIOD OF RAIN CHANCES VERY WELL COULD
CHANGE AND CONFIDENCE IS STILL QUITE LOW IN HOW MUCH RAIN COULD
FALL.
SCATTERED MOSTLY HIGH TERRAIN RAIN CHANCES MAY CONTINUE INTO
SATURDAY BEFORE THE MAIN WEATHER SYSTEM TRAVERSES THE REGION AT
SOME POINT SATURDAY NIGHT AND SUNDAY. ADDITIONAL MOISTURE
ADVECTION IS LIKELY TO OCCUR, ASSOCIATED WITH THE AR, RIGHT AHEAD
OF THE WEEKEND SYSTEM, BUT IT IS TOO EARLY TO KNOW WHERE EXACTLY
THE BEST MOISTURE AND FORCING WILL END UP. EVEN IF WE DO NOT GET A
DIRECT HIT, ENSEMBLE GUIDANCE IS HEAVILY FAVORING AT LEAST A
PARTIAL HIT FROM THE AR LATE SATURDAY INTO SUNDAY. PRELIMINARY QPF
NUMBERS SHOW UPWARDS OF AN INCH MAY BE POSSIBLE OVER THE SOUTH-
CENTRAL ARIZONA LOWER DESERTS TO UPWARDS OF 2" POSSIBLE IN THE
HIGH TERRAIN NORTH AND EAST OF PHOENIX. THESE NUMBERS VERY WELL
COULD CHANGE AND SEEM TO LEAN MORE ON THE OPTIMISTIC SIDE. IF THE
UPPER END OF PRECIP GUIDANCE COMES TO FRUITION, LOCATIONS ACROSS
CENTRAL ARIZONA ARE EXPECTED TO HAVE TO WORRY ABOUT RISING STREAM
AND RIVER LEVELS AGAIN, BUT IT IS DOUBTFUL THERE WILL BE BIG
FLOOD CONCERN DUE TO THE LONGER DURATION OF THE EVENT. GIVEN WE
ARE STILL OUTSIDE THE WINTER SEASON, THIS WEATHER SYSTEM WILL BE
ON THE WARMER SIDE WITH SNOW LEVELS LIKELY STAYING ABOVE 9-10K
FEET.
AVIATION
UPDATED AT 1715Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
NO AVIATION CONCERNS ARE EXPECTED THROUGH MONDAY MORNING. WINDS
WILL FOLLOW LIGHT AND DIURNAL TRENDS WITH PERIODS OF VRB
CONDITIONS DURING DIRECTIONAL SHIFTS. MOSTLY CLEAR SKIES WILL GIVE
WAY TO INCREASING COVERAGE OF HIGH CIRRUS.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO AVIATION CONCERNS ARE EXPECTED DURING THE NEXT 24 HOURS.
OUTSIDE OF EXTENDED PERIODS OF VRB CONDITIONS, WINDS WILL FAVOR A
W'RLY COMPONENT AT KIPL, WHILE KBLH SHIFTS BETWEEN NE AND NW.
CLEAR SKIES WILL GIVE WAY TO INCREASING COVERAGE OF HIGH CIRRUS
THIS EVENING.
FIRE WEATHER
HIGH PRESSURE WILL SETTLE BACK INTO THE REGION OVER THE NEXT
COUPLE OF DAYS LEADING TO DRIER CONDITIONS AND TEMPERATURES
RETURNING INTO THE NORMAL RANGE. MINIMUM HUMIDITY LEVELS WILL
FALL INTO A 20-40% RANGE THIS AFTERNOON AND THEN 15-35% ON
MONDAY. OVERNIGHT RECOVERIES WILL REMAIN GOOD AT 45-70% ACROSS THE
AREA. WINDS WILL REMAIN LIGHT EACH DAY FAVORING TYPICAL DIURNAL
PATTERNS. A SHIFT IN THE WEATHER PATTERN LATE THIS WEEK AND INTO
NEXT WEEKEND MAY BRING ABOUT COOLER, WETTER, AND BREEZIER
CONDITIONS.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
SHORT TERM...KUHLMAN
LONG TERM...KUHLMAN
AVIATION...RW
FIRE WEATHER...KUHLMAN
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