625
FXUS65 KPSR 260045
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
545 PM MST MON OCT 25 2021
UPDATE
UPDATED 00Z AVIATION DISCUSSION.
SYNOPSIS
A WEATHER SYSTEM MOVING THROUGH THE REGION TODAY WILL BRING GUSTY
WINDS, CHANCES FOR RAIN, AND COOLER TEMPERATURES. CHANCES FOR RAIN
WILL MOSTLY REMAIN LIMITED TO HIGH TERRAIN LOCATIONS AS A COLD
FRONT MOVES THROUGH LATE TONIGHT INTO TUESDAY. DRIER, COOLER
WEATHER WILL SET IN FOR TUESDAY BEFORE QUICKLY WARMING UP AGAIN
DURING THE SECOND HALF OF THE WEEK. INCREASING HIGH PRESSURE
DURING THE LATTER HALF OF THE WEEK WILL PUSH TEMPERATURES BACK TO
NEAR NORMAL READINGS WITH DRY CONDITIONS PREVAILING.
DISCUSSION
WATER VAPOR IMAGERY SHOWS THE CENTER OF A ROBUST MID-LEVEL
SHORTWAVE JUST OFF THE CENTRAL CALIFORNIA COAST WHILE AN
ATMOSPHERIC RIVER CONTINUES TO BRING RAIN AND SNOW TO PARTS OF THE
WEST. SHORT-TERM GUIDANCE TAKES THE WAVE ON A SOUTHEASTERLY
TRAJECTORY TONIGHT THROUGH SOUTHERN CALIFORNIA AND ARIZONA BEFORE
QUICKLY EJECTING INTO THE SOUTHERN ROCKIES TUESDAY. DESPITE ITS
EXPEDITIOUSNESS, THIS SYSTEM WILL CAUSE NOTICEABLE CHANGES TO OUR
MELLIFLUOUS WEATHER OF LATE.
FIRST, BREEZY TO WINDY CONDITIONS ARE SPREADING THROUGHOUT
SOUTHEASTERN CALIFORNIA AND SOUTHWESTERN ARIZONA WITH 25-35 MPH
GUSTS BECOMING COMMON BY THIS EVENING. A PERIOD OF SLIGHTLY
STRONGER GUSTS, PERHAPS AS STRONG AS 40-45 MPH, MAY OCCUR FOR A
SHORT TIME AS A COLD FRONT PASSES THROUGH THAT AREA BETWEEN 5 AND
8 PM. ASSESSING THE POTENTIAL FOR STRONGER GUSTS AND/OR WIDESPREAD
40+ MPH GUSTS IS LESS CERTAIN. THE LATEST ECMWF EFI, A USEFUL
TOOL TO ASSESS ANOMALOUS WIND GUSTS, SHOWS INDEX VALUES REACHING
0.6 TO 0.7 FOR PARTS OF THE WESTERN CWA, SUGGESTING CONDITIONS
WILL MOSTLY REFLECT THE CURRENT FORECAST. AS SUCH, A WIND ADVISORY
REMAINS IN EFFECT ONLY FOR THE MOUNTAIN SPRINGS AREA OF IMPERIAL
COUNTY THIS EVENING.
THE COLD FRONT AND BREEZY CONDITIONS WILL SPREAD EAST INTO SOUTH-
CENTRAL AZ LATER THIS EVENING. WIND GUSTS AROUND THE PHOENIX AREA
ARE FORECAST TO REACH 20-30 MPH BUT A FEW EXPOSED RIDGETOPS
AROUND THE AREA AND OVER IN GILA COUNTY COULD SEE A FEW BRIEF 40
MPH GUSTS. WITH THESE KINDS OF SPEEDS AND RECENT DRY CONDITIONS,
LOCALIZED BLOWING DUST CANNOT BE RULED ANYWHERE IN THE LOWER DESERT,
ESPECIALLY AROUND PLACES MORE SUSCEPTIBLE TO BLOWING DUST. IF THE
DUST DOES BLOW, SUSPENDED LOFTED DUST AND SUBSEQUENT HAZY SKIES
COULD LINGER FOR A DAY OR TWO.
BY TONIGHT, THE ASSOCIATED AR WILL ALSO TRANSITION SOUTHWARD WITH
THE MID-LEVEL WAVE BUT MOST OF THE MOISTURE WILL HAVE BEEN
DEPLETED OVER THE CALIFORNIA MOUNTAINS. NEITHER GUIDANCE NOR
OBSERVATIONAL TRENDS SIGNAL MUCH CONFIDENCE FOR RAIN HERE EVEN
THOUGH POPS REMAIN IN THE 20-40% RANGE ACROSS THE NORTHERN
PORTIONS OF THE CWA. THE NBM QPF PROBABILITIES ARE TELLING WITH
HARDLY ANY CHANCE FOR 0.10” OF TOTAL RAINFALL ANYWHERE IN THE
LOWER DESERT. OUTSIDE OF A FEW PLACES THAT MIGHT SEE A COUPLE
HUNDREDTHS, MOST PLACES SEEM POISED TO REMAIN DRY. THE BEST TIMING
FOR RAIN POTENTIAL COINCIDES WITH THE AFOREMENTIONED FRONTAL
PASSAGE.
COOLER, DRIER WEATHER SETS IN FOR TUESDAY AS CLEAR SKIES PREVAIL AND
AFTERNOON HIGHS ONLY TOP OUT IN THE UPPER 70S ACROSS THE LOWER
DESERTS, WHICH IS AROUND 10 DEGREES BELOW SEASONAL NORMALS. THE
BELOW NORMAL TEMPERATURES WON'T STICK AROUND FOR LONG AS HEIGHTS
QUICKLY RISE IN RESPONSE TO UPPER LEVEL RIDGING BUILDING BACK INTO
THE DESERT SOUTHWEST. TEMPERATURES ARE EXPECTED TO WARM BACK TO NEAR
NORMAL VALUES BY THURSDAY AS THE NBM SHOWS HIGH TEMPERATURES
CLIMBING INTO THE UPPER 80S FOR MOST LOWER ELEVATION LOCALES. NBM
SHOWS TEMPERATURES FURTHER WARMING ON FRIDAY WITH HIGHS FLIRTING
WITH 90 DEGREES. THE AVERAGE LAST 90 DEGREE DAY FOR PHOENIX IS
OCTOBER 30TH.
AVIATION
UPDATED AT 0044Z.
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:
WINDS WILL BECOME INCREASINGLY BREEZY OUT OF THE SW AHEAD OF A
COLD FRONT, WITH GUSTS CLIMBING UP TO 20-25 KTS AND BREEZIEST
CONDITIONS IN THE 3Z-8Z TIMEFRAME. A PRE-FRONTAL TROUGH SHOULD
SHIFT WINDS MORE WESTERLY AROUND 5Z-8Z AND FRONTAL PASSAGE IS
EXPECTED BETWEEN 8Z-11Z. WINDS SHOULD BEGIN SUBSIDING POST-FRONT,
BUT REMAIN WESTERLY THROUGH TUESDAY. THERE IS A SLIGHT CHANCE
(10-20%) ISOLATED LIGHT SHOWERS MAY ACCOMPANY THE FRONT, WITH
GREATER CHANCES FAVORING THE HIGHER TERRAIN TO THE NORTH AND EAST.
INCREASING CLOUDS JUST AHEAD OF THE FRONT IS EXPECTED. PRIMARY
CIGS ARE FAVORED AROUND 7-8 KFT, BUT COULD FALL AS LOW AS 4-5 KFT.
THE POTENTIAL FOR MVFR WILL MOSTLY BE BETWEEN 5Z-9Z, WITH CLOUDS
RAPIDLY CLEARING POST- FRONT.
STRONGER WINDS IN SOUTHEAST CA HAVE ALREADY GENERATED A LOT OF
LOFTED DUST THIS AFTERNOON. THE LOFTED DUST MAY BE CARRIED INTO
THE METRO AREA WITH THE COLD FRONT AND IMPACT SLANTWISE
VISIBILITY TUESDAY, ESPECIALLY IN THE MORNING AND POSSIBLY THE
EVENING.
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:
STRONG WIND GUSTS, UPWARDS OF 30-35 KTS, OUT OF THE WEST TO
SOUTHWEST WILL CONTINUE THROUGH THE NEXT FEW HOURS BEFORE
GRADUALLY FALLING FOLLOWING A COLD FRONT. THE STRONG WINDS ARE
GENERATING BLOWING DUST WHICH COULD LOWER VISIBILITY DOWN TO 4-5
SM AT TIMES, AS HAS BEEN OBSERVED AT KBLH. FRONTAL PASSAGE WILL
BE BETWEEN 3Z TO 6Z. MODERATE LLWS IS POSSIBLE AT KIPL THIS
EVENING POST- FRONT IF THE SURFACE IS ABLE TO DECOUPLE AND SURFACE
SPEEDS FALL BELOW 10 KTS. THE GRADIENT ALOFT, WITH 30-40 KT WINDS
ABOVE 1 KFT, SHOULD WEAKEN BY 12Z. BREEZY N TO NW WINDS STILL
EXPECTED TUESDAY, BUT WITH NOTABLY LOWER SPEEDS THAN TODAY. FEW TO
SCT MID AND HIGH CLOUDS SHOULD CLEAR RAPIDLY POST FRONT, BY
MIDNIGHT.
FIRE WEATHER
WEDNESDAY THROUGH SUNDAY:
BELOW NORMAL TEMPERATURES ON WEDNESDAY WILL QUICKLY GIVE WAY TO A
WARMING TREND ON THURSDAY AS HIGH PRESSURE BUILDS INTO THE REGION.
BY FRIDAY, NEAR TO SLIGHTLY ABOVE NORMAL TEMPERATURES ARE EXPECTED
AS AFTERNOON HIGHS APPROACH 90 DEGREES. MINIMUM AFTERNOON RH
VALUES WILL REMAIN IN THE TEENS THROUGH SATURDAY BEFORE INCREASING
TO AROUND 20-25% ON SUNDAY. MAXIMUM RHS WILL GENERALLY REMAIN
AROUND 40-50%. NORTH TO NORTHWESTERLY DAYTIME BREEZY CONDITIONS
ARE EXPECTED THROUGH THE MIDDLE PART OF THE WEEK BEFORE LIGHT AND
DIURNAL WINDS ARE SEEN STARTING ON FRIDAY.
SPOTTER INFORMATION STATEMENT
SPOTTERS SHOULD FOLLOW STANDARD REPORTING PROCEDURES.
PSR WATCHES/WARNINGS/ADVISORIES
AZ...NONE.
CA...WIND ADVISORY UNTIL 2 AM PDT TUESDAY FOR CAZ562.
BLOWING DUST ADVISORY UNTIL 9 PM PDT THIS EVENING FOR CAZ563>567.
WIND ADVISORY UNTIL 7 PM PDT THIS EVENING FOR CAZ563-566-567.
DISCUSSION...12/SMITH
AVIATION...BENEDICT
FIRE WEATHER...SMITH/KUHLMAN
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