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AREA FORECAST DISCUSSION

 
 FXUS65 KTWC 040910
 AFDTWC
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE TUCSON AZ
 210 AM MST SAT JUL 4 2009
 
 .SYNOPSIS...ABUNDANT MOISTURE WILL BRING SCATTERED SHOWERS AND 
 THUNDERSTORMS THIS HOLIDAY WEEKEND. AS A TROUGH PROGRESSES INTO THE 
 WEST COAST...DRIER AIR WILL MOVE INTO ARIZONA NEXT WEEK FOR A 
 DECREASE IN MOISTURE AND THUNDERSTORM ACTIVITY.
 
 &&
 
 .DISCUSSION...WATER VAPOR IMAGERY SHOWS HIGH PRESSURE CENTERED OVER 
 THE SOUTHERN PLAINS WITH A WEAK TROUGH OVER THE WEST COAST. PLENTY 
 OF DRY MID LEVEL AIR COVERS MUCH OF THE EASTERN PACIFIC AND 
 EXTENDING INTO THE DESERT SOUTHWEST. THIS DEMARCATION BETWEEN DRY 
 AND MOIST MID LEVEL AIR CURRENTLY DIVIDES THE STATE IN HALF. THIS IS 
 ALSO WHERE STORMS DEVELOPED FRIDAY AFTERNOON AND ESPECIALLY INTO THE 
 EVENING HOURS. RAINFALL WAS WIDESPREAD ACROSS MUCH OF EASTERN PIMA 
 COUNTY INCLUDING THE TUCSON METRO AREA WITH 6 HOUR TOTALS WELL ABOVE 
 A HALF INCH IN MOST PLACES AND NUMEROUS LOCATIONS RECEIVING MORE 
 THAN 1 INCH. SATELLITE AND RADAR DATA INDICATES THAT THE ACTIVITY IS 
 WINDING DOWN WITH LIGHT TO MODERATE RAIN OVER EASTERN PIMA COUNTY 
 AND INTO NORTHERN PORTIONS OF SANTA CRUZ COUNTY. 
 
 TODAYS FORECAST WILL BE A TRICKY ONE. WITH THE EXTENSIVE DEBRIS 
 CLOUDS FROM THIS MORNINGS RAIN IT SHOULD TAKE A WHILE FOR THE CLOUDS 
 TO THIN OUT. IF THAT IS THE CASE...THEN HIGH TEMPS WILL STRUGGLE TO 
 MAKE IT INTO THE 90S...AND RAIN SHOULD BE SPOTTY IN NATURE WITH NOT 
 VERY MANY STRONG STORMS. ON THE OTHER HAND...IF THE CLOUDS ARE ABLE 
 TO ERODE...AND WE DO GET SIGNIFICANT SUNSHINE...THEN EXPECT HIGHS TO 
 REACH THE MID 90S OR SO AND EXPECT ANOTHER ROUND OF POTENTIALLY 
 STRONG STORMS WITH PLENTY OF RAINFALL. FOR NOW I OPTED THE SECOND 
 CHOICE...WITH SOME INSOLATION AND ANOTHER ROUND OF STORMS. THIS IS 
 BASED MAINLY ON SATELLITE IMAGERY WHICH SHOWS CLOUD TOPS WARMING 
 QUICKLY AND THE BACK EDGE OF THE CLOUDS ARE GENERALLY JUST WEST OF 
 TUCSON. DAY SHIFT CAN ALWAYS ADJUST TODAYS FORECAST IF IT LOOKS LIKE 
 THE CLOUDS WILL LINGER LONGER THAN EXPECTED. 
 
 MODELS INDICATE THAT WE SHOULD STILL BE "IN THE SOUP" FOR ANOTHER 
 DAY OR TWO WITH PWAT VALUES AROUND AN INCH AND HALF OR MORE. BY LATE 
 SUNDAY INTO MONDAY THE HIGH TO OUR EAST IS EXPECTED TO SHIFT WEST OR 
 RECONSOLIDATE OVER THE EASTERN PACIFIC...GIVING THE DESERT SOUTHWEST 
 WEST OR NORTHWEST FLOW ALOFT. THE HIGH BEGINS TO MOVE EAST OVER 
 ARIZONA BY MIDWEEK AND BOTH THE GFS AND ECMWF DRY US OUT 
 CONSIDERABLY. GFS IS ALSO SUGGESTING THAT HIGHS WILL CLIMB INTO THE 
 100 TO 105 RANGE FROM AROUND THE MIDDLE OF THE WEEK AND INTO THE 
 WEEKEND. THIS WOULD RESULT IN A REDUCTION OF THE MOISTURE TAP THAT 
 WE HAVE HAD FOR A WHILE. STILL LOOKING AT A SLIGHT CHANCE TO CHANCE 
 OF AFTERNOON AND EVENING THUNDERSTORMS EACH DAY THROUGH THE WORK 
 WEEK WITH MOST OF THE ACTIVITY FROM TUCSON EASTWARD. AS THE MODELS 
 GET A BETTER HANDLE ON THIS SITUATION WE WILL BE ABLE TO FINE TUNE 
 THE FORECAST IN THE EXTENDED PERIOD.     
  
 &&
 
 .AVIATION...NUMEROUS LIGHT SHOWERS PERSIST THIS MORNING WITH LOWER 
 THAN NORMAL CLOUD CEILINGS. AS THE NIGHT PROGRESSES SHOULD SEE RAIN 
 GRADUALLY TAPER OFF WITH CEILINGS SLOWLY CLIMBING THROUGH THE 
 MORNING HOURS. EXPECT SCATTERED SHOWERS AND THUNDERSTORMS AGAIN 
 TODAY WITH CEILINGS LOWER NEAR THUNDERSTORMS. AVIATION DISCUSSION 
 NOT UPDATED FOR TAF AMENDMENTS.
 
 &&
 
 .FIRE WEATHER...A MOIST ATMOSPHERE ACROSS SOUTHEAST ARIZONA WILL 
 RESULT IN SCATTERED THUNDERSTORMS THROUGH THE WEEKEND. A TROUGH 
 MOVING TOWARDS THE WEST COAST WILL SHIFT A DRIER WESTERLY FLOW INTO 
 ARIZONA NEXT WEEK...ALTHOUGH ENOUGH MOISTURE SHOULD REMAIN IN PLACE 
 TO MINIMIZE ANY FIRE WEATHER RISKS AND CONCERNS.
 
 &&
 
 .TWC WATCHES/WARNINGS/ADVISORIES...NONE.
 
 

 
 MOLLERE
 
 WEATHER.GOV/TUCSON
 
 
 
 
 
 
 

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