856
FXUS65 KPSR 170816
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
116 AM MST SAT OCT 17 2026
KEY MESSAGES
- WIND ADVISORIES CONTINUE ACROSS PORTIONS OF THE REGION THROUGH
THIS MORNING WITH GUSTS OCCASIONALLY OVER 35 MPH RESULTING IN
AREAS OF BLOWING DUST AND DIFFICULT TRAVEL FOR HIGH PROFILE
VEHICLES.
- A SLIGHT CHANCE OF LIGHT RAIN WILL ARRIVE INTO PARTS OF SOUTH- CENTRAL
ARIZONA OVER THE WEEKEND WITH THE BETTER CHANCES FOCUSED OVER
HIGHER TERRAIN LOCATIONS.
- A PACIFIC LOW PRESSURE SYSTEM MOVING INTO THE SOUTHWEST DURING
THE MIDDLE OF NEXT WEEK WILL LEAD TO MUCH BETTER RAINFALL
CHANCES WITH THE POSSIBILITY OF A FEW EMBEDDED THUNDERSTORMS, AS
WELL AS COOLER TEMPERATURES
SHORT TERM /TODAY THROUGH SUNDAY/
A DEFINED REX BLOCK CAN BE SEEN ON BOTH GOES WV IMAGERY AND
RAP-40 500MB ANALYSIS. THE CORE OF THE HIGH IS CURRENTLY OVER
ROCKIES AND THE CORE OF THE CUT OFF LOW REMAINS POSITIONED OVER
THE NORTHERN COAST LINE OF THE BAJA PENINSULA. THE HIGH PRESSURE
WILL CONTINUE TO PUSH EASTWARDS INTO THE NORTHERN PLAINS
THROUGHOUT THE AFTERNOON TODAY AND THE PRESSURE GRADIENT THAT
BROUGHT WIDE SPREAD WINDY CONDITIONS ACROSS THE REGION WILL BEGIN
TO WEAKEN. UNTIL THEN LINGERING STRONG GUSTS WILL LINGER
THROUGHOUT THE MORNING HOURS TODAY, WITH POTENTIAL FOR AREAS OF
LOFTED DUST. THATS SAID A WIND ADVISORY REMAINS IN EFFECT UNTIL 11
AM MST FOR MOST OF PINAL COUNTY AND THE HIGHER TERRAIN EAST OF
PHOENIX OF SOUTHERN GILA COUNTY, WHERE GUSTS BETWEEN 40-55 MPH
WILL BE POSSIBLE, ESPECIALLY ALONG THE MOUNTAIN PEAKS. AFTERWARDS
THE COMBINED EFFECT OF A WEAKENING PRESSURE GRADIENT WITH AN
INCREASE IN THICKER CLOUD COVERAGE AS THE CUT OFF LOW OPENS OPEN
THROUGH THE REGION WILL LEAD TO LESS MIXING AND THEREFORE CUTTING
WINDS DOWN BELOW ADVISORY LEVEL LEADING INTO THE AFTERNOON.
AS MENTIONED PREVIOUSLY THE REX BLOCK IS EXPECTED TO OPEN BY TONIGHT
AND DRIFT THROUGH THE REGION OVER THE WEEKEND. THIS IS EXPECTED TO
ADVECT A DECENT AMOUNT OF MID TO HIGH LEVEL MOISTURE INTO THE REGION
WITH PWATS FORECASTED TO RISE NEAR TO SLIGHTLY ABOVE 1" OVER THE
WEEKEND. WHILE THIS AMOUNT OF MOISTURE IS BETWEEN 150-200% OF
NORMAL, THE LOWER LEVELS ARE EXPECTED TO REMAIN QUITE DRY
RESTRICTING MUCH RAINFALL FROM REACHING THE SURFACE IN MOST AREAS.
HOWEVER, POPS BETWEEN 20-35% REMAINS IN THE FORECAST FOR TODAY-
SUNDAY ACROSS SOUTH-CENTRAL AND THE HIGHER TERRAIN AREAS EAST OF
PHOENIX. BY LATE SUNDAY AFTERNOON POPS REDUCE TO BELOW 10% CWA WIDE
AS THE OPEN WAVE TROUGH LIFTS INTO NORTHERN ARIZONA.
LONG TERM /MONDAY THROUGH THURSDAY/
BY EARLY NEXT WEEK NEXT WEEK THE HIGH PRESSURE WILL BE WELL OVER
NE CONUS AND THE OPEN WAVE TROUGH WILL BEGIN TO BE ABSORBED INTO
THE MEAN SW FLOW HEAD OF THE NEXT INCOMING LOW PRESSURE SYSTEM
DIVING DOWN THE WESTERN COASTLINE. ANOTHER LOW CHANCE (20-30%) OF
SHOWERS MANIFEST MONDAY MORNING ACROSS THE HIGHER TERRAIN, HOWEVER
YET AGAIN, IF ANYTHING DOES DEVELOP TOTAL ACCUMULATIONS ARE
EXPECTED TO BE NEAR ZERO. BY TUESDAY, DEEP TROUGHING AND STRONG
NEGATIVE HEIGHT ANOMALIES WILL AMPLIFY AND INTENSIFY ALONG THE
WEST COAST, HOWEVER CONFIDENCE IS EXACT THE TIMING AND DEPTH OF
THIS FEATURE REMAINS LOW TO MODERATE. THE ECMWF DETERMINISTIC IS
FORECASTING A SLOWER AND MORE ROBUST RAINFALL SCENARIO, WHILE THE
GFS DETERMINISTIC PROVIDES A FASTER AND MORE MILD RAINFALL
POTENTIAL. REGARDLESS, THE TIMING OF ANY RAINFALL POTENTIAL IS
HIGHLIGHTING WEDNESDAY AND THURSDAY. ADDITIONALLY, WITH THE
UNCERTAINTY OF THIS NEXT SYSTEM A WIDE SPREAD IN NBM TEMPERATURES
HAVE PRESENTED THEMSELVES THROUGHOUT THE WEEK, THOUGH BELOW
NORMAL HIGHS ARE LIKELY.
AVIATION
UPDATED AT 0545Z.
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
MAIN AVIATION CONCERNS WILL BE CONTINUED BREEZINESS AND LINGERING
SLANTWISE VIS REDUCTION DUE TO LOFTED DUST. WINDS THROUGH SUNRISE
WILL BEHAVE SIMILAR TO THE PREVIOUS NIGHT WITH RELATIVELY ELEVATED
SUSTAINED SPEEDS AROUND 10-15 KT AND SPORADIC GUSTS UPWARDS OF 25
KT OR SO. KSDL WILL BE MORE SUSCEPTIBLE TO THESE GUSTS DUE TO
THEIR CLOSER PROXIMITY TO TERRAIN FEATURES AND ORIENTATION OF THE
OVERALL FLOW. THOUGH NOT INCLUDED IN THE TAFS, LOCALIZED LLWS
COULD CREATE OPERATIONAL IMPACTS OVERNIGHT DUE TO WINDS 35-45 KT
A FEW THOUSAND FEET ABOVE THE SURFACE. MORE PERSISTENT BREEZINESS
WILL REEMERGE AFTER SUNRISE BEFORE A NOTICEABLE DOWNTREND IN
SPEEDS TAKE PLACE DURING THE BACK-HALF OF THE FORECAST WINDOW.
SLANTWISE VIS SHOULD BEGIN TO IMPROVE IN CONJUNCTION WITH THE
WEAKENING WINDS. CONSIDERABLE CLOUD COVER WILL BE PRESENT OVER THE
REGION, WITH BASES DROPPING TO 9-12 KFT BY SATURDAY AFTERNOON.
THE THICK CLOUD COVER WILL BE ACCOMPANIED BY ISOLATED SHOWER CHANCES
STARTING SATURDAY AFTERNOON AND EVENING AND VCSH HAS BEEN ADDED TO
EACH OF THE TAFS FROM ABOUT 00Z TO THE END OF THE FORECAST. HOWEVER,
CONFIDENCE IN THIS TIMING IS LOW, AND IT IS NOT OUT OF THE QUESTION
THAT SHOWER ACTIVITY MOVES IN A FEW HOURS SOONER. WITH THAT BEING
SAID, MENTION OF -SHRA HAS BEEN EXCLUDED FROM THE TAFS AS
OPERATIONAL IMPACTS WILL BE MINIMAL AT BEST WITH POTENTIAL ACTIVITY.
TEMPOS THAT INCLUDE THE MENTION OF RAINFALL MAY BE ADDED IN
SUBSEQUENT FORECASTS IF CONFIDENCE INCREASES OR GREATER IMPACTS ARE
EXPECTED.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
NO MAJOR AVIATION CONCERNS ARE EXPECTED DURING THE NEXT 24 HOURS.
OUTSIDE OF PERIODS OF VRB CONDITIONS, NE'RLY FLOW WILL BE FAVORED
AT BOTH TERMINALS THROUGH MUCH OF THE FORECAST. ISOLATED GUSTS
UPWARDS OF 25 KT CANNOT BE RULED OUT AT KBLH THROUGH SUNRISE.
ISOLATED SHRA WILL BE SEEN OVER THE REGION TONIGHT, WITH SOME
MOVING WITHIN THE VICINITY OF KIPL. HOWEVER, NO IMPACTS ARE
EXPECTED WITH THIS ACTIVITY. CONSIDERABLE CLOUD COVER WILL BE
PRESENT THROUGH SATURDAY AFTERNOON, WITH THE LOWEST BASES AROUND
9-12 KFT.
FIRE WEATHER
STRONG EAST WINDS WILL CONTINUE THROUGH THIS MORNING ACROSS
SOUTHERN ARIZONA WITH THE MOST PRONOUNCED GUSTS OVER MOUNTAIN TOPS
OF EASTERN DISTRICTS. GUSTS 40-45 MPH MAY BE COMMON OVER THESE
LOCATIONS WITH A PORTION OF THESE WINDS BUILDING INTO LOWER
ELEVATIONS BY LATE MORNING, BEFORE WEAKENING HEADING INTO THE
AFTERNOON HOURS, WITH EVEN WEAKER WINDS SUNDAY THROUGH THE MIDDLE
OF NEXT WEEK. LIGHT SHOWERS ARE POSSIBLE THIS WEEKEND, AND
PARTICULARLY OVER EASTERN DISTRICTS, BUT THE CHANCE FOR WETTING
RAIN IS LOW (~10%). THE STRONG EAST WINDS WILL RESULT IN MINIMUM
HUMIDITY LEVELS 15-30% TODAY, BUT INCREASING CLOSER TO A 30-50%
RANGE THEREAFTER. OVERNIGHT RECOVERY SHOULD BE GOOD TO EXCELLENT.
A PACIFIC WEATHER DISTURBANCE WILL BRING INCREASED CHANCES OF
WETTING RAINFALL, BREEZY WINDS, AND COOLER TEMPERATURES DURING THE
LATTER HALF OF NEXT WEEK.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...WIND ADVISORY UNTIL 11 AM MST SATURDAY FOR AZZ547-552-553-555-
557-558-560>562.
CA...NONE.
SHORT TERM...RYAN
LONG TERM...RYAN
AVIATION...RW
FIRE WEATHER...18/RYAN
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