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
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