269  
FXUS65 KPSR 240507  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
1007 PM MST THU MAR 23 2023  
   
UPDATE  
UPDATED AVIATION DISCUSSION.  
 
 
   
SYNOPSIS  
 
DRY AND TRANQUIL WEATHER WILL PREDOMINATE THROUGH THE WEEKEND THOUGH  
TEMPERATURES WILL CONTINUE TO HOVER AROUND 10 DEGREES BELOW THE  
SEASONAL NORMAL. A WARMING TREND WILL TAKE HOLD EARLY NEXT WEEK  
BEFORE THE NEXT WEATHER DISTURBANCE SWEEPS THROUGH THE REGION. THIS  
SYSTEM WILL RESULT IN MODEST RAINFALL CHANCES AND A RETURN TO COOLER  
THAN NORMAL TEMPERATURES TOWARDS THE LATTER HALF OF NEXT WEEK.  
 
 
   
DISCUSSION  
 
A BROAD, LOW AMPLITUDE TROUGHING PATTERN WILL BE MAINTAINED OVER THE  
SW CONUS THROUGH THE WEEKEND WITH SEVERAL EMBEDDED VORTICITY CENTERS  
TRAPPED IN THE FLOW ACROSS NORTHERN AZ. SUFFICIENT LINGERING LOW  
LEVEL MOISTURE COMBINED WITH FAVORABLE UPSLOPE FLOW AND COOLER  
TEMPERATURES ALOFT WILL BE SUPPORTIVE OF A FEW ISOLATED SHOWERS  
ACROSS THE NORTHEAST CWA THROUGH TONIGHT BEFORE THE NEXT REINFORCING  
SHOT OF DRIER AIR ARRIVES FRIDAY AFTERNOON. FORECAST CONFIDENCE IS  
EXCELLENT THAT PERSISTENT GREAT BASIN TROUGHING WILL FORCE A QUASI-  
ZONAL PATTERN OVER THE FORECAST AREA AND H5 HEIGHTS STUCK NEAR  
564DM. VERY NARROW ENSEMBLE SPREADS SUGGEST AFTERNOON HIGHS  
SEQUESTERED AROUND 10F BELOW THE SEASONAL NORMAL THROUGHOUT THE  
WEEKEND WITH INTERMITTENT CLOUD COVER.  
 
THERE IS VERY GOOD MODEL AGREEMENT THAT SHORTWAVE RIDGING WILL BUILD  
INTO THE SOUTHWEST EARLY NEXT WEEK IN RESPONSE TO DEEPER NEGATIVE PV  
ANOMALIES INTENSIFYING OFF THE CALIFORNIA COAST. NOT ONLY WILL  
HEIGHTS EXPERIENCE A MODEST BUMP DURING THE MON-TUE TIME FRAME, BUT  
THERMAL PROFILES WILL WARM MARKEDLY. RECENT NBM OUTPUT CONTINUES TO  
HIGHLIGHT TUESDAY AS THE WARMEST DAY WITH BETTER THAN A 50% CHANCE  
MOST LOWER ELEVATION COMMUNITIES BREACH THE 80F THRESHOLD. TIMING  
AND DEPTH ISSUES ABOUND IN RECENT ENSEMBLE OUTPUT REGARDING THE NEXT  
WEATHER DISTURBANCE ENTERING THE WESTERN CONUS NEXT WEEK. IN  
GENERAL, GEFS MEMBERSHIP FAVORS A FASTER MOVING, LESS AMPLIFIED  
OUTCOME, WHILE EPS MEMBERS LEAN TOWARDS A DEEPER, SLOWER MOVING  
WAVE. TRENDS IN ENSEMBLES SEEM TO FAVOR THE SLOWER OUTCOME, ALBEIT  
SIMILAR TO THE MOST RECENT SYSTEM WHERE ONLY THE TRAILING TROUGH  
AXIS AFFECTS THE CWA. RECENT NBM POPS REMAIN VERY MEAGER WITH THIS  
SYSTEM (LESS THAN 10%) THOUGH CONTINUE TO ADVERTISE TEMPERATURES  
RETREATING BACK TOWARDS NEARLY 10F BELOW CLIMATOLOGY DURING THE  
LATTER PART OF THE WEEK.  
 
 
   
AVIATION  
UPDATED AT 0510Z.  
 
SOUTH-CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, AND KDVT:  
STRATOCU WILL THICKEN OVERNIGHT AS A WEAK LOW PRESSURE SYSTEM  
MOVES THROUGH THE AREA. CEILINGS ARE GENERALLY EXPECTED TO REMAIN  
ABOVE 7000 FT, THOUGH A BRIEF DROP TO 6000 FT IS POSSIBLE,  
PARTICULARLY AT KSDL AND POSSIBLY AT KPHX (20% CHANCE). THERE IS  
ALSO A 10 PERCENT CHANCE OF A SHOWER AROUND SUNRISE, WHICH WILL BE  
FOLLOWED BY A RAPID CLEARING TREND.  
 
WINDS WILL GENERALLY REMAIN WESTERLY OVERNIGHT, HOWEVER A BRIEF  
SWITCH TO EASTERLY NOW LOOKS LIKELY AROUND 12Z. THE WESTERLY FLOW  
WILL THEN REDEVELOP DURING THE LATE MORNING. BREEZY CONDITIONS ARE  
ALSO ANTICIPATED FRIDAY AFTERNOON WITH GUSTS LIKELY REACHING 20  
KT.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
WESTERLY WINDS WILL PERSIST THROUGH FRIDAY AS A WEAK LOW PRESSURE  
SYSTEM PASSES BY TO THE NORTH OVERNIGHT. GUSTS WILL LIKELY REACH  
30 KT AT KIPL TONIGHT FOLLOWED BY SOMEWHAT LIGHTER WINDS FRIDAY.  
 
 
   
FIRE WEATHER  
 
TEMPERATURES WILL REMAIN BELOW AVERAGE THROUGH THE WEEKEND, BEFORE  
WARMING EARLY NEXT WEEK THEN COOLING AGAIN BY MIDWEEK. SOME LATE  
AFTERNOON BREEZINESS CAN BE EXPECTED IN IMPERIAL COUNTY TODAY,  
OTHERWISE LIGHT TO MODERATE DIURNAL WINDS WILL PERSIST ACROSS THE  
LOWER DESERTS THROUGH THE WEEKEND. A DRYING TREND IS EXPECTED  
THROUGH THE REST OF THE WEEK, WITH LITTLE TO NO WETTING RAINS  
EXPECTED THROUGH THE REST OF THE FORECAST PERIOD. MAXRH'S WILL BE  
NEAR 70-90% TODAY, BEFORE DECREASING TO AROUND 40-60% THROUGH THE  
WEEKEND. WHILE MINRH'S IN THE 25-45% RANGE WILL DIP BACK INTO THE  
LOW TO MID TEENS PERCENT BY THE END OF THIS WEEKEND.  
 
 
   
HYDROLOGY  
 
DOWNSTREAM IMPACTS CONTINUE ACROSS OUR EASTERN CWA FROM THE  
EXCESSIVE RAINFALL EVENT OVER NORTH-CENTRAL ARIZONA THE LAST 48-60  
HOURS. AS OF THIS MORNING, FLOOD WARNINGS ARE IN EFFECT FOR PORTIONS  
OF THE SALT, VERDE, AND GILA RIVERS. ACCORDING TO SRP DATA, THE  
WATERSHED IS 95% FULL WITH ONGOING RELEASES AT BARTLETT AND STEWART  
MOUNTAIN DAMS. AT GRANITE REEF, THE LATEST RELEASE VOLUME IS 38,000  
CFS. DESPITE VERY LITTLE ADDITIONAL FORECAST PRECIPITATION,  
SUBSTANTIAL RUNOFF IS STILL OCCURRING WITHIN THESE BASINS. THUS,  
FLOOD WARNINGS ALONG THESE RIVERS WAS EXTENDED UNTIL MARCH 31.  
PLEASE CONTINUE TO AVOID RIVER BANKS AND RECREATIONAL PLANS ALONG  
THESE RIVERS, AND HEED ALL PARK AND ROAD CLOSURES!!  
 
AT TONTO CREEK, THE FLOOD WARNING WAS EXTENDED UNTIL MARCH 29 AS LOW  
WATER CROSSINGS ARE STILL IMPASSIBLE. FINALLY, WE CONTINUE TO  
MONITOR SMALLER RIVERS/STREAMS AROUND MARICOPA COUNTY. THE NEW RIVER  
NEAR PEORIA AND PORTIONS OF THE HASSAYAMPA RIVER ARE STILL ABOVE  
ALARM STAGE. THESE SMALLER STREAMS AND RIVERS WILL SLOWLY FALL OVER  
THE NEXT 24-48 HOURS AS SIGNIFICANT PRECIPITATION IS NO LONGER  
FALLING ACROSS THEIR RESPECTIVE BASINS.  
 
 
   
PSR WATCHES/WARNINGS/ADVISORIES  
 
AZ...NONE.  
CA...NONE.  
 
 
 
 
DISCUSSION...18  
AVIATION...HIRSCH  
FIRE WEATHER...LEFFEL  
HYDROLOGY...HEIL  
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