390
FXUS65 KPSR 162350
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
450 PM MST SAT OCT 16 2021
UPDATE
00Z AVIATION DISCUSSION.
SYNOPSIS
HIGH PRESSURE OVER THE REGION WILL YIELD MOSTLY CLEAR SKIES AND
QUITE SEASONABLE TEMPERATURES THIS WEEKEND THOUGH PERIODICALLY
BREEZY CONDITIONS WILL BE COMMON THROUGH SOUTH-CENTRAL ARIZONA. A
WEAK COLD FRONT WILL RESULT IN SOMEWHAT COOLER TEMPERATURES MONDAY
AND TUESDAY, HOWEVER SUBTLE WARMING WILL RESUME WEDNESDAY AND
THURSDAY. DRY WEATHER IS EXPECTED THROUGH THE END OF NEXT WEEK.
DISCUSSION
PRONOUNCED RIDGING REMAINS POSITIONED OVER THE SW CONUS THIS
AFTERNOON WITHIN A PROGRESSIVE HEMISPHERIC FLOW PATTERN, ALBEIT WITH
WEATHER DISTURBANCES PRIMARILY DEFLECTED NORTH OF THE FORECAST AREA
AND THROUGH THE NORTHERN HALF OF THE CONUS. OBJECTIVE ANALYSIS AND
REGIONAL SOUNDINGS EXHIBIT LITTLE CHANGE IN HEIGHTS/THERMAL PROFILES
ALOFT OVER ARIZONA, HOWEVER DO REVEAL SUBSTANTIAL WARMING IN THE SFC-
H7 LAYER RESULTING IN FORECAST TEMPERATURES FINALLY REBOUNDING TO
THE SEASONAL AVERAGE THROUGH SUNDAY (I.E. LOWER ELEVATION
COMMUNITIES AROUND THE 90F THRESHOLD). DUE TO THE CONFIGURATION OF
THE RIDGE AXIS, SURFACE PRESSURE RISES HAVE BEEN FAVORED OVER THE
ROCKIES RESULTING IN A STEEP GRADIENT OVER THE ELEVATION TRANSITION
IN THE EASTERN CWA. MECHANICAL MIXING HAS TRANSLATED A PORTION OF
THE HIGHER MOMENTUM AIR TOWARDS THE SURFACE, AND WIDESPREAD GUSTS 20-
25 MPH HAVE BEEN COMMON ACROSS THE PHOENIX METRO AND SURROUNDING
AREAS. A SUBTLE RECONFIGURATION OF THE RIDGE WITH MODEST HEIGHT
FALLS BEGINNING TO ENTER THE REGION WILL ALLOW THE PRESSURE GRADIENT
TO RELAX SUNDAY YIELDING FAR LESS GUSTINESS.
DURING THE FIRST PART OF NEXT WEEK, A MORE SIGNIFICANT TROUGH WILL
MOVE ACROSS NORTHERN/CENTRAL CALIFORNIA INTO THE GREAT BASIN
STRENGTHENING THE MID-LEVEL TROPOSPHERIC FLOW ACROSS THE SOUTHWEST.
GIVEN THE ANTECEDENT DRY AIRMASS IN PLACE AND WESTERLY LOW LEVEL
TRAJECTORIES ACCOMPANYING THIS SYSTEM, BETTER QUALITY MOISTURE
SHOULD REMAIN FAR REMOVED FROM THE FORECAST AREA WITH THE BEST
PRECIPITATION CHANCES CONFINED TO COASTAL SOUTHERN CALIFORNIA.
PERIODS OF HIGH CIRRUS CLOUD COVER AND LOCALLY BREEZY CONDITIONS ARE
REALLY THE ONLY WEATHER IMPACTS OF CONSEQUENCE ACROSS SOUTHEAST
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY ON MONDAY. AT THIS
TIME, MORE NOTABLE WIND ANOMALIES PER NAEFS OUTPUT SHOULD REMAIN
NORTH OF THE FORECAST AREA WITH THE MORE TYPICAL DOWNSLOPING GUSTS
IN SW IMPERIAL COUNTY.
MIDTROPOSPHERIC HEIGHT RISES WILL AGAIN ENVELOP THE REGION DURING THE
LATTER HALF OF NEXT WEEK WITH H5 HEIGHTS POTENTIALLY REBOUNDING BACK
ABOVE 588DM. WHILE DIURNAL MIXING DEPTHS ARE MORE SHALLOW THIS TIME
OF YEAR, THERE IS AT LEAST A 50% CHANCE HIGH TEMPERATURES AT THE END
OF THE WEEK REACH INTO THE LOWER 90S (THOUGH STILL WELL SHORT OF
RECORD TERRITORY). WHERE AS FORECAST CONFIDENCE IS EXCELLENT THROUGH
MUCH OF NEXT WEEK, UNCERTAINTY GROWS MORE SUBSTANTIALLY NEXT WEEKEND
(AND BEYOND) AS A DOWNSTREAM BLOCKING PATTERN RETROGRADES BACK INTO
NORTH AMERICA. ENSEMBLE TRENDS SUGGEST A SOMEWHAT LESS CHANCE FOR
SHARP TROUGHING TO ENTER THE SOUTHWEST, BUT RATHER A PREPONDERANCE
OF GUIDANCE INDICATES NEGATIVE HEIGHT ANOMALIES BECOMING QUASI-
STATIONARY ALONG THE PACIFIC NW COAST WHILE STRONGER ZONAL FLOW
PREDOMINATES THE LOCAL FORECAST AREA. THIS CONFIGURATION WOULD
SUPPORT CONTINUED DRY WEATHER WITH TEMPERATURE NOT FAR FROM
CLIMATOLOGY.
AVIATION
UPDATED AT 2350Z.
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
EASTERLY FLOW WILL PERSIST INTO EARLY SUNDAY AFTERNOON. BREEZY
CONDITIONS ARE ALSO LIKELY EARLY THIS AFTERNOON BEFORE WINDS
SUBSIDE SOMEWHAT EARLY THIS EVENING. LATER TONIGHT (PRIMARILY
AFTER 5Z), LOCALIZED POCKETS OF LLWS WILL LIKELY DEVELOP AROUND
THE VALLEY. WHERE WINDS DROP OFF AT THE SURFACE, 25 KT OF SHEAR IS
POSSIBLE. THESE WINDS WILL THEN MIX DOWN TO THE SURFACE RESULTING
IN AREAS WITH SUSTAINED WINDS OF 10-15 KTS. DUE TO ELEVATED WIND
SPEEDS, THERE MAY BE BLOWING DUST (MORE LIKELY AT KIWA). WINDS
WILL REMAIN ELEVATED NEAR 10 KTS IN THE AFTERNOON ON SUNDAY,
BEFORE SUBSIDING A BIT SUNDAY EVENING. SKIES WILL BE MOSTLY CLEAR
BEFORE THICKER MID AND HIGH-LEVEL CLOUDS MOVE INTO THE REGION LATE
TOMORROW MORNING AND PERSIST THROUGH THE AFTERNOON.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
WINDS WILL RETAIN NORTHERLY AND WESTERLY COMPONENTS THROUGH
SUNDAY MORNING WITH SPEEDS GENERALLY LESS THAN 15 KT. SUNDAY
AFTERNOON, A SHIFT TO SOUTHWESTERLY FLOW IS LIKELY WITH SPEEDS
REMAINING ELEVATED AROUND 10-15 KTS. AT KBLH, GUSTS TO 20 KTS WILL
ALSO BE POSSIBLE TOMORROW AFTERNOON.
FIRE WEATHER
MONDAY THROUGH FRIDAY:
BREEZY CONDITIONS ARE ANTICIPATED ON MONDAY ACROSS SOUTHEAST
CALIFORNIA AND THE LOWER COLORADO RIVER VALLEY AS A DRY LOW PRESSURE
SYSTEM ADVANCES ACROSS THE SOUTHWEST. TEMPERATURES WILL BE A FEW
DEGREES BELOW NORMAL MONDAY THROUGH WEDNESDAY IN ASSOCIATION WITH
THIS SYSTEM AND PERIODIC UPPER-LEVEL CLOUD COVER. WINDS WILL WEAKEN
DURING THE MIDDLE PART OF THE WEEK AS HIGH PRESSURE REBUILDS, AND
TEMPERATURES CLIMB BACK INTO THE UPPER 80S TO NEAR 90 THURSDAY AND
FRIDAY. MIN AFTERNOON RH VALUES WILL MOSTLY FALL BETWEEN 15-20%
ACROSS THE LOWER DESERTS TO 20-25% ACROSS THE HIGH TERRAIN.
OVERNIGHT RECOVERIES WILL MOSTLY REACH BETWEEN 30-50% THROUGH THE
PERIOD.
SPOTTER INFORMATION STATEMENT
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...NONE.
DISCUSSION...18/ROGERS
AVIATION...FELDY/HIRSCH
FIRE WEATHER...ROGERS
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