Area Forecast Discussion
Issued by NWS Phoenix, AZ

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000 FXUS65 KPSR 262118 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 215 PM MST SUN APR 26 2015 .SYNOPSIS... A LOW PRESSURE SYSTEM WILL EXIT INTO NEW MEXICO TONIGHT WITH A FEW LINGERING SHOWERS OVER EASTERN ARIZONA INTO MONDAY AFTERNOON. DRY WEATHER WITH A SIGNIFICANT WARMING TREND WILL COMMENCE RAPIDLY THIS WEEK...WITH TEMPERATURES IN THE LOWER ELEVATION POPULATION CENTERS APPROACHING THE 100 DEGREE MARK DURING THE MIDWEEK TIME FRAME. && .DISCUSSION... THE WELL ADVERTISED TROUGH AXIS...CIRCULATION CENTER...AND COLD CORE ALOFT HAS TRANSLATED INTO SOUTHWEST NEW MEXICO THIS AFTERNOON. AN ASSOCIATED ELONGATED LOBE OF PV HAS BEEN FILLING INTO THE TROUGH BASE...AND DELINEATING A SHARP MIDTROPOSPHERIC FRONT AND AREAS OF ASCENT/DESCENT THROUGH CENTRAL ARIZONA. MEANWHILE...A SECONDARY WING OF VORTICITY HAS ROTATED BACK SOUTH TOWARDS THE COLD CORE ACTING UPON LOW LEVEL DESTABILIZATION...AND FORCING CONVECTIVE SHOWERS WITHIN THE COLD CORE CYCLONIC CURVATURE REGION. WHILE LOSS OF DAYTIME HEATING WILL LIMIT FURTHER CONVECTIVE GROWTH (ESPECIALLY ALONG THE WESTERN PERIPHERY THROUGH THE PHOENIX METRO)...AMPLE MIDLEVEL MOISTURE AND SYNOPTIC SCALE ASCENT WILL KEEP SOME SHOWERS GOING THROUGH PARTS OF SRN GILA COUNTY. HIGHER HEIGHTS ALOFT WILL GRADUALLY PROPAGATE EASTWARD MONDAY AS UPSTREAM WEST COAST RIDGING AMPLIFIES. HOWEVER...NORTHERLY FLOW ALOFT AND COOLER MIDTROPOSPHERIC TEMPERATURES COINCIDENT WITH RESIDUAL MOISTURE AND MORE INTENSE SPRING INSOLATION WILL SUPPORT MORE ISOLD/SCT CONVECTIVE SHOWERS OVER FAR EASTERN ARIZONA...POTENTIALLY CLIPPING THE SAN CARLOS REGION OF SRN GILA COUNTY. OTHERWISE...THE VAST MAJORITY OF THE FORECAST AREA WILL FALL UNDER STRONGER SYNOPTIC SCALE SUBSIDENCE AS H5 HEIGHTS INCREASE TO 573-579DM YIELDING AFTERNOON HIGHS 5-10F WARMER THAN TODAY. STRONG RIDGING WITH H5 HEIGHTS IN EXCESS OF 580DM WILL FOLD OVER INTO THE FORECAST AREA TUESDAY THROUGH THURSDAY. WHILE SOME THIN CIRRUS IS POSSIBLE...MUCH OF THE REGION WILL BE CHARACTERIZED BY FULL INSOLATION AND MIXING DEPTHS AOA 600MB. WITH H8 TEMPERATURES REACHING THE +25C LEVEL...AFTERNOON HIGHS FLIRTING WITH (OR EXCEEDING) THE 100F THRESHOLD WILL BE COMMON WEDNESDAY AND THURSDAY. THIS IS WELL SHORT OF RECORD HIGHS AND NOT UNCOMMON FOR THIS TIME OF YEAR...WITH THE AVERAGE FIRST 100F DAY IN PHOENIX OCCURRING ON MAY 2ND...AND IN YUMA APRIL 23RD. A WEAK SHORTWAVE SHOULD SETTLE OVER THE EASTERN PACIFIC ALONG THE CALIFORNIA COAST LATE IN THE WEEK...HELPING EDGE THE CORE OF THE HIGHEST HEIGHTS ALOFT INTO THE SOUTHERN PLAINS. THIS WILL ALLOW FOR A CONTINUATION OF DRY CONDITIONS OVER THE SWRN CONUS...AND ONLY A SLIGHT COOLING SOMEWHAT CLOSER TO THE CLIMATOLOGICAL NORMAL FOR THE BEGINNING OF MAY. && .AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL... SCT LIGHT SHOWERS WILL MOVE EAST OF TERMINALS AND DISSIPATE THIS EVENING...WITH LOWER CIGS AND MOUNTAIN OBSCURATION ON EASTERLY APPROACHES THE PRIMARY AVIATION CONCERN. CIGS IN A 5K-7K FT LEVEL WILL LIFT AND SCT WITH SUNSET THIS EVENING...THOUGH SOME SCT-BKN CLOUDS ABV THE 10K FT LEVEL WILL BE POSSIBLE INTO THE OVERNIGHT. NORTHWEST WINDS WITH SOME GUSTS WILL WEAKEN AND EVENTUALLY TURN EASTERLY TOWARDS SUNRISE MONDAY...HOWEVER ONLY MODEST CONFIDENCE IN TIMING WIND SHIFTS EXISTS. SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND KBLH... OCCASIONALLY GUSTY N/NW WINDS WILL BE THE PRIMARY AVIATION CONCERN THROUGH MONDAY UNDER MOSTLY CLEAR SKIES. WHILE GUSTS MAY ABATE WITH SUNSET...A STRENGTHENING NLY LLJ TOWARDS SUNRISE MAY MIX TO THE SFC AT KBLH. OTHERWISE...SFC WINDS IN A 10-20KT RANGE WILL BE COMMON ACROSS SE CALIFORNIA. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... TUESDAY THROUGH SATURDAY... SOME PERIODS OF ELEVATED NORTHEASTERLY BREEZES ARE POSSIBLE OVER SOUTH-CENTRAL AZ THRU MIDWEEK... LIKELY DURING THE EARLY MORNING HOURS ENHANCING THE ALREADY TYPICAL DRAINAGE PATTERN. TEMPERATURES WILL BEGIN TO WARM SUBSTANTIALLY AND APPROACH THE TRIPLE DIGIT MARK DURING THE MIDDLE OF THE WEEK AS HIGH PRESSURE STRENGTHENS. AFTERNOON HUMIDITIES WILL DROP INTO THE LOWER TEENS AND UPPER SINGLE DIGITS WITH FAIR OVERNIGHT RECOVERIES. DURING THE LATTER HALF OF THE WEEK...WINDS WILL GENERALLY BE LIGHT FOLLOWING TYPICAL DIURNAL PATTERNS. && VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...MO AVIATION...MO FIRE WEATHER...MO/NOLTE

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