686 FXUS65 KPSR 290920 AFDPSR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PHOENIX AZ 220 AM MST WED JAN 29 2014 .SYNOPSIS... STRONG HIGH PRESSURE ALOFT WILL KEEP DRY CONDITIONS IN PLACE ACROSS THE REGION...WITH WELL ABOVE NORMAL TEMPERATURES TODAY AND THURSDAY. THEN...A SERIES A WEAK WEATHER DISTURBANCES THAT ARE FORECAST TO MOVE INLAND ACROSS THE DESERT SOUTHWEST WILL BRING COOLER TEMPERATURES AND AN INCREASE IN CLOUDINESS AND WINDS...WITH A SLIGHT CHANCE FOR SHOWERS FOR THE HIGHER TERRAIN NORTH AND EAST OF PHOENIX BEGINNING ON FRIDAY...AND CONTINUING INTO EARLY NEXT WEEK. && .DISCUSSION... TODAY AND THURSDAY... STRONG RIDGING THAT HAS DOMINATED THE WEATHER OVER THE DESERT SOUTHWEST FOR THE PAST SEVERAL WEEKS IS EXPECTED TO BRING THE REGION TWO MORE DAYS OF WELL-ABOVE NORMAL TEMPERATURES AS IT SHIFTS EASTWARD...AND BEGINS TO BE FLATTENED BY A SERIES OF SHORTWAVES THAT WILL BE MOVING INLAND INTO THE PACIFIC NORTHWEST AND NORTHERN CALIFORNIA. 850 MB TEMPERATURES IN THE 14-16C RANGE WILL BE HIGH ENOUGH TO ALLOW TEMPERATURES TO RISE WELL INTO THE 70S AT MOST LOWER DESERT LOCATIONS TODAY...WITH INCREASING LOW-LEVEL SOUTHERLY FLOW ALLOWING HIGHS TO APPROACH...OR EVEN EXCEED 80F ON THURSDAY. THE ONLY THING THAT WILL LIKELY KEEP PHOENIX SKY HARBOR FROM BREAKING ITS DAILY RECORD OF 82F ON THURSDAY IS INCREASING HIGH CLOUDINESS...THAT WILL LIMIT SOLAR RADIATION A BIT ON THURSDAY AFTERNOON. FRIDAY THOROUGH MONDAY... MODELS CONTINUE TO INDICATE A LARGE-SCALE PATTERN CHANGE...THAT WILL BRING UNSETTLED...AND COOLER WEATHER TO THE REGION FROM FRIDAY ONWARD INTO AT LEAST THE EARLY PART OF NEXT WEEK. LATEST GLOBAL COMPOSITE WV IMAGERY NOW SHOWS A SERIES OF SHORTWAVES BEGINNING TO LINE UP ACROSS THE PACIFIC AS A MODERATELY STRONG SUBTROPICAL JET BEGINS TO UNDERCUT THE VERY STRONG RIDGE THAT HAS BEEN DOMINATING THE WEATHER ACROSS THE WESTERN US FOR THE LAST SEVERAL WEEKS. AT LEAST THREE DISTINCT FEATURES ARE FORECAST BY BOTH THE GFS AND EURO TO MOVE INLAND INTO THE DESERT SOUTHWEST OVER THE NEXT SEVERAL DAYS. ALTHOUGH THERE CONTINUES TO BE SOME UNCERTAINTY CONCERNING THE TIMING OF THIS SHORTWAVES...BOTH THE MODELS AND SATELLITE IMAGERY ARE INDICATING THAT THESE SYSTEMS WILL NOT BE MAJOR PRECIPITATION PRODUCERS...GIVEN THE FACT THAT THEY WILL BE TRACKING TOO FAR NORTH TO TAP MUCH MOISTURE FROM THE TROPICS...WITH A RELATIVE LACK OF DEEP CONVECTION ACROSS WESTERN AND CENTRAL PACIFIC ALSO LIMITING THE AMOUNT OF MOISTURE THAT IS AVAILABLE FOR THESE SYSTEMS . HOWEVER...THERE APPEARS TO BE AT LEAST ENOUGH AGREEMENT ACROSS THE MODEL SUITES TO ALLOW POPS TO BE INCREASED INTO AT LEAST THE SLIGHT CHANCE RANGE BEGINNING ON FRIDAY ACROSS THE HIGHER TERRAIN OF SOUTH-CENTRAL ARIZONA...WITH PWATS RISING INTO THE 0.6 TO 0.8 INCH RANGE ACROSS SOUTH-CENTRAL AZ. TEMPERATURES WILL BE NOTICEABLY COOLER STARTING ON FRIDAY...REMAINING IN THE LOWER 70S AT MOST LOWER DESERT LOCATIONS...WITH HIGHS IN THE 60S LIKELY ON SUNDAY AND MONDAY. STRONGER WINDS ALOFT WILL LIKELY BRING SOME AFTERNOON BREEZES TO THE REGION AS WELL...BUT WINDS ARE EXPECTED TO REMAIN WELL BELOW ADVISORY CRITERIA. TUESDAY AND WEDNESDAY... THERE ARE INDICATIONS ON BOTH THE GFS AND EURO MODEL RUNS THAT RIDGING WILL ATTEMPT TO REBUILD NORTHWARD ACROSS THE EASTERN PACIFIC...WITH DRY CONDITIONS AND WARMER TEMPERATURES RETURNING TO OUR REGION. && .AVIATION... SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...SOUTHWEST ARIZONA AND SOUTHEAST CALIFORNIA INCLUDING KIPL AND KBLH... THROUGH AT LEAST 20Z WED...VARIABLE HIGH CLDS AOA 25 THSD MSL. LIGHT WIND UNDER 7 KNOTS. AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS. && .FIRE WEATHER... THURSDAY THROUGH MONDAY... HIGH PRESSURE WILL BEGIN TO WEAKEN THURSDAY AS A LOW PRESSURE SYSTEM PASSES TO THE NORTH. THIS WILL ALLOW FOR STRONGER WESTERLY WINDS ALOFT WHICH WILL TRANSLATE TO MODERATE BREEZINESS THURSDAY AND FRIDAY...MAINLY OVER SOUTHEAST CALIFORNIA AND AT RIDGETOPS ELSEWHERE. A COOLING TREND IS EXPECTED TO BEGIN FRIDAY AND CONTINUE INTO EARLY NEXT WEEK LEADING TO HIGH TEMPERATURES AT OR SLIGHTLY BELOW NORMAL BY MONDAY. THERE WILL ALSO BE A SLIGHT CHANCE OF SHOWERS MONDAY OVER THE HIGHER TERRAIN. MINIMUM HUMIDITIES WILL BE LOW THURSDAY THEN INCREASE CONSIDERABLY FRIDAY BEFORE TRENDING DOWNWARD AGAIN. MAXIMUM HUMIDITIES WILL REMAIN GOOD. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...NONE. CA...NONE. && $$ VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX DISCUSSION...PERCHA AVIATION...VASQUEZ FIRE WEATHER...AJ