AREA FORECAST DISCUSSION

 
 FXUS65 KPSR 101428 AAB
 AFDPSR
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE PHOENIX AZ
 725 AM MST WED FEB 10 2010
 
 .UPDATE...BASED ON LATEST SAT/RADAR TRENDS AND OBSERVATIONS THIS 
 MORNING...THE WINTER STORM ADVISORY FOR JOSHUA TREE NATIONAL PARK IN 
 SOUTHEAST CALIFORNIA HAS BEEN CANCELLED. 
 
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 .SYNOPSIS...
 A LOW PRESSURE SYSTEM WILL BRING RAIN AND MOUNTAIN SNOW SHOWERS...AS 
 WELL AS A SLIGHT CHANCE OF THUNDERSTORMS...FROM SOUTHEAST CALIFORNIA 
 TO SOUTH-CENTRAL ARIZONA THROUGH TODAY. SHOWERS WILL MOVE TO THE 
 SOUTHEAST OUT OF THE AREA BY LATE TONIGHT. DRY AND WARMER WEATHER 
 WILL COMMENCE FRIDAY. SIGNIFICANTLY WARMER WEATHER THIS WEEKEND WILL 
 CONTINUE THROUGH EARLY NEXT WEEK AS HIGH PRESSURE ALOFT FROM THE 
 PACIFIC BECOMES ESTABLISHED OVER THE WESTERN UNITED STATES.
 
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 .DISCUSSION...
 CENTER OF CIRCULATION IS APPROACHING SAN DIEGO AT THIS TIME. BROAD 
 BAND OF SHOWERS DEVELOPED IN THE JUXTAPOSITION AREA OF WEAK MOISTURE 
 ADVECTION AND STRONG 500MB HEIGHT FALL ADVECTION...WHICH EXTENDED 
 FROM THE NORTHERN TIP OF THE GULF OF CALIFORNIA NORTH INTO SRN NV. 
 SMALL LINE OF THUNDERSTORMS HAS MOST RECENTLY DEVELOPED OVER AND 
 SOUTH OF YUMA...LIKELY ASSOCIATED WITH THE H7-H5 FRONTOGENETICAL 
 FORCING.
 
 MODELS CONTINUE TO SHOW RELATIVELY GOOD AGREEMENT AND RUN-TO-RUN 
 CONSISTENCY WITH THE EXPECTED PATH OF THIS SYSTEM. PREFER THE 03Z 
 SREF DATA FOR THE DETAILS. H5 LOW WILL BEGIN TO TAKE A MORE ELY 
 DIRECTION THIS MORNING. STRONGEST FORCING CONTINUES TO BE FOCUSED ON 
 SE CA AND SW AZ THROUGH THIS MORNING WHICH IS WHERE POPS AND QPF ARE 
 HIGHEST AND SLIGHT CHANCES FOR THUNDERSTORMS WILL CONTINUE. AS THE 
 LOW MOVES ALONG THE INTERNATIONAL BORDER THIS AFTERNOON IT TAKES ON 
 AN INCREASINGLY POSITIVE TILT RESULTING IN A WEAKENING TREND. THUS 
 AS THE LOW SKIRTS TO THE SOUTH PRECIP SHOULD BE STARTING TO FALL 
 APART ACROSS SOUTH CENTRAL ARIZONA /INCLUDING THE PHOENIX AREA/. 
 GIVEN THE SATURATED BL AND HIGH CLOUD COVER HIGH TEMPERATURES ARE 
 STILL EXPECTED TO BE FAIRLY COOL TODAY. THE LOW CONTINUES TO MOVE 
 EAST TONIGHT. PRECIP CHANCES WILL QUICKLY END FROM WEST TO EAST BY 
 THURSDAY MORNING.
 
 BASED ON SOUNDING INFORMATION AND SFC OBS...SNOW LEVEL IS AROUND 
 4000 FEET. AS THE COLDEST AIR WILL BE MOVING TO THE SOUTH... MORE 
 INTO NORTHERN BAJA AND SONORA...SNOW LEVELS ARE EXPECTED TO REMAIN 
 AROUND 4000 FEET FOR SE CA AND AROUND 5000 FEET FOR SRN GILA COUNTY. 
 
 FRIDAY INTO NEXT WEEK GFS AND ECMWF CONTINUE TO FORECAST A LONG WAVE 
 RIDGE DEVELOPING OVER THE WESTERN CONUS. I ZEROED OUT THE POPS 
 DURING THIS PERIOD AND INCREASED TEMPERATURES A BIT FROM THE CURRENT 
 FORECAST. ABOVE NORMAL TEMPERATURES SHOULD ARRIVE BY SATURDAY AND 
 REMAIN THROUGH MID-WEEK WITH PLENTY OF CLEAR SKY.
 
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 .AVIATION...
 KPHX AND KIWA...
 CEILINGS ARE EXPECTED TO LOWER TO NEAR 4 THOUSAND FEET AFTER 1400 GMT
 THIS MORNING WITH CEILINGS AND VISIBILITIES DROPPING TO NEAR 3 
 THOUSAND FEET AND 3 MILES IN HEAVIER SHOWERS AND THUNDERSTORMS 
 ASSOCIATED WITH A COLD FRONT FROM THE WEST FROM ABOUT 1700 GMT THIS 
 MORNING TO 2100 GMT THIS AFTERNOON. AFTER THAT...SHOWERS ARE 
 EXPECTED TO DECREASE...BUT CEILINGS NEAR 4 TO 6 THOUSAND FEET COULD 
 REMAIN INTO THIS EVENING...THEN BECOME SCATTERED CLOUDS AROUND 5 TO 
 7 THOUSAND FEET BY 0600 GMT TONIGHT. GUSTY VARIABLE WINDS ARE 
 POSSIBLE NEAR STORMS...OTHERWISE WINDS NEAR 10 KNOTS ARE EXPECTED TO 
 REMAIN MOSTLY FROM THE EAST AND SOUTHEAST THROUGH EARLY THIS 
 AFTERNOON...BECOMING MOSTLY FROM THE NORTHWEST BY THIS EVENING.
 
 KIPL...
 SCATTERED TO BROKEN CLOUDS AT OR ABOVE 5 THOUSAND FEET ARE EXPECTED 
 THIS MORNING AND MOSTLY BETWEEN 5 AND 10 THOUSAND FEET THIS 
 AFTERNOON. CLOUDS ARE EXPECTED TO DECREASE TO A FEW CLOUDS NEAR 5 
 THOUSAND FEET AFTER 0100 GMT TONIGHT. WINDS ARE EXPECTED TO BE FROM 
 THE NORTHWEST NEAR 11 KNOTS TODAY AND FROM THE WEST AROUND 6 KNOTS 
 AFTER 0100 GMT TONIGHT.
 
 KBLH...
 CEILINGS NEAR 4 THOUSAND FEET WITH CEILINGS AND VISIBILITIES 
 DROPPING TO NEAR 2 THOUSAND FEET AND 3 MILES IN HEAVIER SHOWERS
 UNTIL ABOUT 2000 GMT THIS AFTERNOON. AFTER THAT...SHOWERS ARE 
 EXPECTED TO DECREASE...BUT CEILINGS NEAR 4 TO 6 THOUSAND FEET COULD 
 REMAIN INTO THIS EVENING...THEN BECOME A FEW CLOUDS AROUND 5 
 THOUSAND FEET 0300 GMT TONIGHT. WINDS ARE EXPECTED TO BE FROM THE 
 NORTHWEST NEAR 11 KNOTS TODAY...FROM THE NORTH AFTER 2300 GMT LATE 
 THIS AFTERNOON INTO THIS EVENING...THEN DECREASING TO 6 KNOTS FROM 
 THE NORTH AFTER 0300 GMT TONIGHT.
 
 AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
 
 &&
 
 .FIRE WEATHER...
 FRIDAY THROUGH TUESDAY...
 HIGH PRESSURE ALOFT FROM THE PACIFIC WILL BRING A RETURN TO 
 RELATIVELY DRIER AIR AND A RECOVERY OF TEMPERATURES FRIDAY. THIS 
 HIGH PRESSURE SYSTEM WILL BUILD OVER THE WESTERN UNITED STATES WITH 
 SIGNIFICANTLY WEATHER THIS WEEKEND. MINIMUM RELATIVE HUMIDITY IS 
 EXPECTED TO GENERALLY REMAIN NEAR OR ABOVE 20 PERCENT WITH GOOD TO 
 EXCELLENT RECOVERY AT NIGHT. A BIT OF BREEZINESS FROM THE NORTH AND 
 NORTHEAST IS EXPECTED THIS WEEKEND AND EARLY NEXT WEEK...
 ESPECIALLY DOWN THE LOWER COLORADO RIVER VALLEY THIS WEEKEND.
   
 &&
 
 .PSR WATCHES/WARNINGS/ADVISORIES...
 
 AZ...NONE.
 
 CA...NONE.
 
 
 &&
 
 $$
 
 NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
 
 WEATHER.GOV/PHOENIX
 
 DISCUSSION...WANEK/INIGUEZ
 AVIATION...ELLIS
 FIRE WEATHER...ELLIS