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AREA FORECAST DISCUSSION

 
 FXUS65 KTWC 132041
 AFDTWC
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE TUCSON AZ
 140 PM MST TUE MAY 13 2008
 
 .SYNOPSIS...STRONG LOW PRESSURE WILL CROSS SOUTHEAST ARIZONA THIS
 AFTERNOON AND THIS EVENING...BEFORE EXITING INTO NEW MEXICO LATE
 TONIGHT.  SUNNY AND WARMER WEDNESDAY...ALTHOUGH WITH TEMPERATURES STILL
 BELOW NORMAL FOR MID-MAY.  THE NEXT STORM SYSTEM BRINGS AN OPPORTUNITY
 FOR SOME RAIN SHOWERS FOR THE EASTERN AND SOUTHEAST COUNTIES THURSDAY
 NIGHT INTO FRIDAY.
 
 &&
 
 .DISCUSSION...AS EXPECTED...NOT YOUR TYPICAL MID-MAY DAY FOR SOUTHEAST
 ARIZONA. STRONG COLD UPPER LOW APPEARS TO BE ON TRACK AND ON SCHEDULE
 NEAR PHOENIX THIS AFTERNOON. LIMITED SUNSHINE AND COLD AIR ADVECTION
 ASSOCIATED WITH THE APPROACHING LOW HAS KEPT MOST OF US IN THE 
 70S...SOME 10-15 DEGREES BELOW CLIMO. KEMX WSR-88D SHOWS THE FIRST 
 WAVE OF SHOWERS AND THUNDERSTORMS AFFECTING MUCH OF PINAL AND PIMA 
 COUNTIES EARLY THIS AFTERNOON. GUSTY WINDS TO 50 MPH...BLOWING 
 DUST...OCCASIONAL LIGHTNING AND SMALL HAIL ARE POSSIBLE WITH ANY 
 THUNDERSTORM THROUGH THIS AFTERNOON. STRONG DYNAMICS AND MODEST 
 INSTABILITY WILL COMBINE TO CONTINUE TO PRODUCE SCATTERED SHOWERS 
 AND THUNDERSTORMS THROUGH THIS EVENING. MOISTURE HAS IMPROVED 
 MARGINALLY...WITH SURFACE DEWPOINTS IN THE 20S AND 30S. NOT A 
 LOT...BUT THAT SHOULD HELP MORE LOCATIONS MEASURE SOME MORE 
 MEANINGFUL RAINFALL. MEANWHILE...VERY STRONG WINDS AND FIRE DANGER 
 HAVE BEEN THE CONCERNS FOR SANTA CRUZ AND COCHISE COUNTIES THIS 
 AFTERNOON...BUT THE PRESSURE GRADIENT HERE WILL RELAX BY THIS 
 EVENING AS THE MAIN LOW APPROACHES...AND INCREASED CLOUD COVER 
 DECREASES MIXING.  SEE FIRE WEATHER SECTION BELOW. NOT TO BE LEFT 
 OUT...WE HAVE LEFT SNOW GRIDS INTACT FOR OUR NORTHEAST ZONES...WITH 
 ACCUMULATIONS OF 1-3 INCHES FOR THE WHITE MOUNTAINS NEAR HANNAGAN 
 MEADOW BY EARLY WEDNESDAY MORNING. NOTHING LIKE THE 11 INCHES 
 REPORTED AT SUNSET CRATER IN FLAGSTAFF`S CWA...BUT VERY IMPRESSIVE 
 FOR MID-MAY TO SAY THE LEAST.
 
 STRONG SYSTEM WILL EXIT INTO NEW MEXICO BY WEDNESDAY MORNING.  STRONG
 SUBSIDENCE ON THE BACKSIDE SHOULD CLEAR SKIES BY SUNRISE TO ALLOW 
 FOR DECENT RADIATIONAL COOLING...WITH LOWS TONIGHT IN THE 40S AND 
 LOWER 50S.  SUNSHINE RETURNS WITH WARMER TEMPERATURES...BUT STILL WITH
 TEMPERATURES RUNNING ABOUT 5 DEGREES BELOW THE NORM FOR MID-MAY.
 
 NEXT ON THE AGENDA IS AN ADDITIONAL SLUG OF ENERGY THAT DIVES DOWN 
 THE EAST SIDE OF THE WEST COAST RIDGE AND CUTS OFF ANOTHER CLOSED 
 LOW NEAR SOUTHEAST ARIZONA LATE THURSDAY INTO EARLY FRIDAY.  12Z GFS 
 AND ECMWF AGREE ON THIS ASPECT...BUT 12Z ECMWF APPEARS MUCH MORE
 REALISTIC WEAKENING AND OPENING THIS WAVE AND MOVING IT EAST AWAY 
 FROM US AND ALLOWING HIGH PRESSURE TO BEGIN BUILDING INTO ARIZONA. 
 12Z GFS WOULD SUGGEST SEVERAL DAYS WITH RAIN CHANCES LATER THIS WEEK
 INTO THE WEEKEND WHICH OBVIOUSLY IS STARKLY AGAINST SOUTHEAST 
 ARIZONA CLIMATOLOGY IN MAY. SO...OUR FORECAST POP GRIDS ARE CONFINED 
 TO THE LATE THURSDAY AND EARLY FRIDAY TIMEFRAME AND LEAN TOWARD THE 
 ECMWF.
 
 && 
 
 .FIRE WEATHER...A RED FLAG WARNING CONTINUES FOR SANTA CRUZ AND COCHISE
 COUNTIES THROUGH 7 PM THIS EVENING.  RELATIVE HUMIDITIES LESS THAN 
 15 PERCENT AND STRONG SOUTHWEST WINDS HAVE CREATED HIGH FIRE DANGER 
 WHICH WILL CONTINUE INTO THIS EVENING BEFORE THE GRADIENT RELAXES 
 AFTER 7 PM. LESS FIRE DANGER WEDNESDAY WITH TYPICAL DIURNAL WINDS.
 
 &&
 
 .AVIATION...MOSTLY CLOUDY SKIES THROUGH THIS EVENING.  ISOLATED TO 
 SCATTERED SHOWERS AND THUNDERSTORMS WILL MOVE FROM WEST TO EAST 
 ACROSS SOUTHEAST ARIZONA THROUGH THE EVENING WITH CLOUD BASES BROKEN 
 TO OVERCAST AT 7-10K FEET AGL.  STRONG SOUTHWEST WINDS OF 20-30 
 KTS WITH HIGHER GUSTS WILL CONTINUEINTO THIS EVENING.  CLEARING 
 SKIES BY 12Z WEDNESDAY..WITH WINDS RETURNING TO TYPICAL DIURNAL DIRECTIONS
 AND SPEEDS ON WEDNESDAY.
 
 &&
 
 .TWC WATCHES/WARNINGS/ADVISORIES...RED FLAG WARNING FOR SANTA CRUZ   
        AND COCHISE COUNTIES THROUGH 7PM THIS EVENING.
 
 

 
 TURNER
 
 WEATHER.GOV/TUCSON
 
 
 
 
 
 
 
 
 
 
 

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