020  
FXUS65 KPSR 211156  
AFDPSR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PHOENIX AZ  
456 AM MST MON JUL 21 2025  
   
UPDATE
 
UPDATED AVIATION DISCUSSION.  
 

 
   
KEY MESSAGES
 
 
- BELOW NORMAL TEMPERATURES EARLY THIS WEEK WILL GRADUALLY WARM  
CLOSER TO THE SEASONAL AVERAGE BY THE END OF THE WEEK RESULTING IN  
WIDESPREAD MINOR HEATRISK INCREASING TO A MODERATE LEVEL.  
 
- CHANCES FOR SHOWERS AND THUNDERSTORMS WILL LINGER THROUGH THE  
FIRST HALF OF THE WEEK WITH THE BETTER CHANCES FOCUSED OVER THE  
ARIZONA HIGH TERRAIN BEFORE DRIER AIR SWEEPS INTO THE REGION.  
 

 
   
SHORT TERM /TODAY THROUGH TUESDAY/
 
 
EARLY MORNING WV IMAGERY DEPICTS A CONVOLUTED FLOW PATTERN WITH THE  
SW CONUS STUCK BETWEEN A WEAK, SUBTROPICAL ANTI-CYCLONE OVER THE  
SOUTHERN PLAINS AND AN ELONGATED, DEEPENING TROUGH ALONG THE  
CALIFORNIA COAST. THIS PATTERN OF STRONG S/SE FLOW HAS BEEN QUITE  
CONDUCIVE TOWARDS IMPORTING THICK MIDTROPOSPHERIC MOISTURE INTO THE  
FORECAST AREA, HOWEVER NOT AS FAVORABLE TOWARDS RETAINING BETTER  
QUALITY BOUNDARY LAYER MOISTURE. IN FACT, OBJECTIVE ANALYSIS  
SUGGESTS LOW LEVEL 10 G/KG MIXING RATIOS STILL SEQUESTERED NEAR THE  
INTERNATIONAL BORDER WITH A SUB-OPTIMAL 8 G/KG ONLY EXTENDING INTO  
CENTRAL ARIZONA. DESPITE THIS MARGINAL MOISTURE PROFILE, INCREASED  
JET ENERGY AND COOLING MIDLEVEL TEMPERATURES FROM THE APPROACHING  
TROUGH WILL SUPPORT A FEW PERIODIC THUNDERSTORMS OVER THE NEXT 48  
HOURS WITH GUSTY OUTFLOW WINDS THE PRIMARY HAZARD, THOUGH SOME BRIEF  
HEAVY DOWNPOURS WILL ALSO BE POSSIBLE.  
 
CONVECTIVE COVERAGE TODAY REMAINS VERY UNCERTAIN AS A LARGELY  
FAVORABLE SYNOPTIC PATTERN IS COUNTERACTED BY LIMITED DEEP MOISTURE  
AVAILABILITY. WHILE TEMPERATURES ALOFT ARE CERTAINLY NOT UNUSUALLY  
WARM (-6C AT H5), REDUCED MIXING RATIOS AND LIMITED HEATING WITHIN  
THE BOUNDARY LAYER SHOULD PRECLUDE MUCH INSTABILITY OVER LOWER  
ELEVATIONS AS MOIST ADIABATIC LAPSE RATES LINGER OVER THE CWA. HREF  
MEMBERSHIP REMAINS FAIRLY CONSISTENT IN DEVELOPING DEEP CONVECTION  
OVER THE TYPICAL AREAS SUCH AS TABLE TOP WILDERNESS SOUTH OF I-8 AND  
TERRAIN FEATURES OF EASTERN PINAL/GRAHAM COUNTIES. ASCENT AIDED BY  
RIGHT ENTRANCE REGION JET DYNAMICS AND DCAPE VALUES AROUND 1000 J/KG  
SHOULD FOSTER MOVEMENT OFF TERRAIN FEATURES, HOWEVER ACTIVITY SHOULD  
QUICKLY DECAY HEADING INTO LOWER ELEVATION LEAVING ONLY RESIDUAL  
OUTFLOW BOUNDARIES (AND POSSIBLY SOME BLOWING DUST). NBM POPS ONCE  
AGAIN LEAVE MUCH TO BE DESIRED WITH POOR TIMING AND PLACEMENT THAT  
HAS BEEN EVIDENT OVER THE PAST SEVERAL MONTHS, AND MANY NOTABLE  
ADJUSTMENTS WERE MADE TO THE MANDATED INITIALIZATION GIVEN THIS  
SUBJECTIVE SYSTEMATIC BIAS.  
 
FORECAST UNCERTAINTY GROWS SUBSTANTIALLY TUESDAY WITH SEVERAL  
DIFFERENT SCENARIOS POSSIBLY UNFOLDING ACROSS SOUTH-CENTRAL ARIZONA.  
SYNOPTIC FORCING APPEARS TO REMAIN VERY FAVORABLE WHILE THERE IS  
ALSO EVIDENCE OF A BOUNDARY LAYER MOISTURE INFLUX SURGING NORTH FROM  
CONVECTIVE REMNANTS YIELDING MIXING RATIOS 11-12 G/KG AND TOTAL  
COLUMN PWATS CLOSER TO 1.75". HOWEVER, SIMILAR TO YESTERDAY, AND  
SUPPORTED BY BOTH HI-RES AND COARSER GLOBAL MODELS, THIS MOISTURE  
FLUX MAY COME IN THE FORM OF EXTENSIVE CLOUD COVER AND MORNING  
SHOWERS. UNLIKE YESTERDAY MORNING WHERE A WELL DEFINED MCV ENSURED A  
LACK OF INSTABILITY, WEAKER AND MORE DISORGANIZED SYNOPTIC LIFT MAY  
ALLOW FOR SOME MODEST INSOLATION TUESDAY AFTERNOON REALIZING MLCAPE  
IN EXCESS OF 1000 J/KG. ALL TOLD, THE PREPONDERANCE OF MODEL OUTPUT  
SUGGESTS THE BETTER THUNDERSTORM CHANCES REMAINING OUTSIDE THE CWA  
(MORE LIKELY TOWARDS TUCSON) WHERE BETTER HEATING AND DEEPER  
MOISTURE PROFILES SHOULD BE COLLOCATED. NEVERTHELESS, A FEW STORMS  
AND GUSTY OUTFLOW WINDS STILL SEEM A REASONABLE OUTCOME FOR SOME  
COMMUNITIES IN THE EASTERN HALF OF THE CWA.  
 

 
   
LONG TERM /WEDNESDAY THROUGH SUNDAY/
 
 
ENSEMBLE MEMBERSHIP REMAINS IN EXCELLENT AGREEMENT ADVERTISING AN  
EXPANSIVE SUBTROPICAL ANTI-CYCLONE SPRAWLING ACROSS THE SE CONUS  
WHILE DEEP NEGATIVE HEIGHT ANOMALIES BECOME ESTABLISHED ALONG THE  
CALIFORNIA COAST WITH STRONG SW FLOW IMPINGING INTO THE FORECAST  
AREA. WITH H5 HEIGHTS BARELY ECLIPSING 590DM, TEMPERATURES WILL  
CONTINUE TO HOVER BELOW THE DAILY NORMALS DURING THE MIDDLE OF THE  
WEEK WITH ONLY MODEST WARMING TOWARDS THE END OF THE WEEK AS  
SUBTROPICAL RIDGING SLOWLY BEGINS TO RETROGRADE INCURRING MINOR  
HEIGHT RISES BY THE WEEKEND. THE AFOREMENTIONED SW FLOW WILL  
CONTINUE TO STRENGTHEN HELPING RAPIDLY ERODE MOISTURE ACROSS THE  
REGION DURING THE LATTER HALF OF THE WEEK. LATEST GFS BUFR SOUNDINGS  
SUGGEST MIXING RATIOS FALLING BELOW 5 G/KG AND TOTAL COLUMN PWATS  
NEAR 0.50" BY WEDNESDAY AFTERNOON ESSENTIALLY PRECLUDING  
THUNDERSTORM DEVELOPMENT OUTSIDE OF MOUNTAIN LOCATIONS. WIDESPREAD  
DRY WEATHER SEEMS AN ALMOST CERTAINTY DURING THE END OF THE WEEK,  
AND IT WILL TAKE THE REESTABLISHMENT OF STRENGTHENING HIGH PRESSURE  
OVER THE FOUR CORNERS EARLY NEXT WEEK TO RESUME DEEP SE FLOW AND  
START THE WHOLE MONSOON FLOW PROCESS AND CONVECTIVE PROGRESSION  
OVER.  
 

 
   
AVIATION
 
UPDATED AT 1155Z.  
 
SOUTH CENTRAL ARIZONA INCLUDING KPHX, KIWA, KSDL, KDVT:  
THE PRIMARY AVIATION CONCERN WILL BE THE POTENTIAL FOR GUSTY  
OUTFLOW WINDS LATE AFTERNOON INTO THE EVENING AS A RESULT OF  
THUNDERSTORMS SOUTH OF PHOENIX. WINDS WILL FAVOR SE THIS MORNING  
AND SHIFT S-SW BY LATE MORNING/EARLY AFTERNOON, A SLOWER THAN  
USUAL TRANSITION. A FEW ISOLATED STORMS MAY FORM TO THE SW AT  
FIRST DURING THE AFTERNOON, AND SO OUTFLOWS FROM THOSE (IF THEY  
REACH THE TERMINALS) WOULD NOT CHANGE THE PREVAILING SW/W WINDS.  
HOWEVER, BY THE EVENING, HI-RES GUIDANCE INDICATES POTENTIALLY A  
MORE ORGANIZED OUTFLOW SHIFTING WINDS S AND THEN SE. THE DETAILS  
ARE STILL UNCERTAIN AT THIS POINT AND HIGHLY DEPENDENT ON IF/WHERE  
THUNDERSTORM DEVELOPMENT IS MORE FOCUSED. WITH ANY LATE  
AFTERNOON/EVENING OUTFLOWS, THERE IS A 10-30% CHANCE FOR WIND  
GUSTS UPWARDS OF 30 KTS. CLOUDS DECKS WILL GENERALLY BE SCT-BKN  
AND REMAIN AOA 8 KFT AGL. CHANCES FOR VCSH/VCTS CONDITIONS TODAY  
REMAIN LOW (10% OR LESS EXCEPT AT KIWA, WHERE IT IS CLOSER TO  
20%), SO THEY ARE NOT MENTIONED IN THE TAF.  
 
SOUTHEAST CALIFORNIA/SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH:  
NO MAJOR AVIATION WEATHER CONCERNS ARE EXPECTED THROUGH THE NEXT 24  
HOURS UNDER MOSTLY CLEAR SKIES. WINDS WILL OTHERWISE CONTINUE TO  
PREDOMINANTLY FAVOR THE E-SE AT KIPL AND S AT KBLH WITH SOME  
AFTERNOON AND EARLY EVENING GUSTS TO AROUND 20 KTS.  
 

 
   
FIRE WEATHER
 
 
A WARMING AND DRYING TREND WILL PREDOMINATE THE REGION THIS WEEK AS  
TEMPERATURES SEVERAL DEGREES BELOW THE DAILY NORMALS RETURN CLOSER  
TO THE SEASONAL AVERAGE BY THE END OF THE WEEK. THE CHANCE FOR  
SHOWERS OVER EASTERN DISTRICTS THE NEXT COUPLE DAYS WILL RETREAT  
INTO HIGHER TERRAIN AREAS, THEN EVENTUALLY OUTSIDE OF THE FORECAST  
AREA BY THE LATTER HALF OF THE WEEK. EVEN WITH A FEW SHOWERS THE  
NEXT COUPLE DAYS, WETTING RAINFALL CHANCES ARE QUITE LOW. OTHERWISE,  
MINIMUM AFTERNOON HUMIDITY VALUES IN A 15-30% RANGE WILL FALL INTO A  
5-10% RANGE DURING THE SECOND HALF OF THE WEEK. SIMILARLY, FAIR TO  
GOOD OVERNIGHT RECOVERY OF 30-70% WILL DECREASE INTO A POOR TO FAIR  
RANGE OF 20-40% LATE IN THE WEEK. WINDS SHOULD BE FAIRLY TYPICAL  
THROUGH THE WEEK WITH ONLY THE TYPICAL AFTERNOON UPSLOPE GUSTINESS.  
 

 
   
PSR WATCHES/WARNINGS/ADVISORIES
 
 
AZ...NONE.  
CA...NONE.  

 
 

 
 
SHORT TERM...18  
LONG TERM...18  
AVIATION...WHITTOCK/SMITH  
FIRE WEATHER...18  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab AZ Page
The Nexlab CA Page Main Text Page