AREA FORECAST DISCUSSION

 
 FXUS66 KHNX 241410 AAA
 AFDHNX
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE SAN JOAQUIN VALLEY - HANFORD CA
 610 AM PST TUE NOV 24 2009
 
 .UPDATE...
 PATCHY DENSE FOG HAS DEVELOPED THIS MORNING IN THE MERCED-ATWATER 
 AND HANFORD-VISALIA AREAS...AS WELL AS WESTERN MADERA COUNTY. 
 SATELLITE LOOPS SHOW A NARROW BAND OF FOG/STRATUS FROM CENTRAL 
 MERCED COUNTY SOUTH THROUGH WESTERN MADERA AND FRESNO COUNTIES INTO 
 NORTHEASTERN KINGS COUNTY. VISIBILITIES ELSEWHERE IN THE CENTRAL AND 
 SOUTHERN SAN JOAQUIN VALLEY AT 1230Z /0530 PST/ GENERALLY WERE 
 BETWEEN 2-4 MILES...EXCEPT FOR 7+ MILES ON THE WEST SIDE OF THE 
 VALLEY NEAR COALINGA AND N.A.S. LEMOORE. HAVE ISSUED A SPECIAL 
 WEATHER STATEMENT /SFOSPSHNX OR WWUS86 KHNX/ ON THE FOG AS THE 
 EXTENT IS LIMITED AT THIS TIME.
 
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 .SYNOPSIS...SKIES WILL BE MOSTLY CLEAR FOR THE NEXT COUPLE DAYS 
 EXCEPT FOR LATE NIGHT AND EARLY MORNING FOG. 
 
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 .DISCUSSION...
 AS FEARED...MONDAY/S STRATUS OVER THE CENTRAL AND SOUTHERN SAN 
 JOAQUIN VALLEY RESULTED IN A WIDER RANGE OF HIGH TEMPERATURES THAN 
 IS NORMALLY SEEN. HIGHS RANGED FROM 53 /AT MERCED MUNICIPAL AIRPORT/ 
 TO 65 AT COALINGA. THE WARM SPOT FOR THE HANFORD WARNING/FORECAST 
 AREA WAS THE RIVER KERN RAWS...WHICH REPORTED A HIGH OF 67 DEGREES.
 
 THE STRATUS FINALLY CLEARED OUT OF THE CENTRAL AND SOUTHERN SAN 
 JOAQUIN VALLEY THIS AFTERNOON...AND SKIES ARE CLEAR ACROSS THE 
 REGION THIS MORNING. THE IMMEDIATE FORECAST CONCERN IS WHETHER THERE 
 WILL BE SUFFICIENT RADIATIONAL COOLING FOR WIDESPREAD FOG DEVELOPMENT
 IN THE CENTRAL AND SOUTH VALLEY. 
 
 THE 00Z MODELS ARE IN GOOD AGREEMENT WITH AN UPPER-LEVEL RIDGE OVER 
 CALIFORNIA THROUGH WEDNESDAY. AN UPPER-LEVEL TROUGH WILL DEVELOP OVER
 THE GULF OF ALASKA TODAY AND DEEPEN AS IT MOVES EASTWARD WEDNESDAY. 
 THE TROUGH IS FORECAST TO BE ALONG 130W BY 00Z FRIDAY...THEN MOVE 
 INTO CALIFORNIA BY 12Z FRIDAY. THIS IS FORECAST TO BE A FAST MOVING 
 SYSTEM...WITH THE TROUGH AXIS MOVING ACROSS THE HANFORD FORECAST/ 
 WARNING AREA BETWEEN 12-18Z FRIDAY. THE GFS...ECMWF AND NAM-12 ALL 
 KEEP 850-700-MB MOISTURE NORTH OF THE CENTRAL CALIFORNIA INTERIOR 
 FRIDAY AS THE TROUGH MOVES THROUGH...SO DO NOT EXPECT ANY 
 PRECIPITATION FROM THIS SYSTEM.
 
 ALTHOUGH FRIDAY/S TROUGH WILL BE DRY OVER THE CENTRAL CALIFORNIA 
 INTERIOR...IT WILL BRING A COLD AIRMASS. THE 00Z GFS LOWERS 850-MB 
 TEMPERATURES OVER CENTRAL CALIFORNIA BY 4 C FRIDAY...AND THE 00Z 
 ECMWF BY 6 C. 1000-500-MB THICKNESSES OVER THE REGION ARE FORECAST 
 TO FALL BY AS MUCH AS 60 METERS. THE GFS MEX GUIDANCE FOR THE CENTRAL
 AND SOUTHERN SAN JOAQUIN VALLEY HAS ONLY 0-2 DEGREES COOLING FOR 
 FRIDAY...AND THIS SEEMS TOO LITTLE BASED OF 850-MB TEMPERATURE AND 
 1000-500-MB THICKNESS TRENDS. THE CURRENT FORECAST HAS 5-7 DEGREES 
 COOLING FRIDAY...AND THIS SEEMS MORE IN LINE WITH THE MODELS.
 
 THE UPPER-LEVEL TROUGH IS FORECAST TO LINGER OVER THE GREAT BASIN 
 FRIDAY NIGHT AND SATURDAY...AND THE 00Z ECMWF EVEN RETROGRESSES IT 
 BACK INTO CALIFORNIA BY 00Z SUNDAY. THIS...COMBINED WITH THE LOW- 
 LEVEL COLD POOL TRAPPED OVER THE SAN JOAQUIN VALLEY...WILL KEEP 
 TEMPERATURES COOL FOR ONE MORE DAY.
 
 AN UPPER-LEVEL EAST-PACIFIC RIDGE BEGINS BUILDING INTO CALIFORNIA 
 SUNDAY AND WILL BE OVER THE REGION MONDAY INTO NEXT TUESDAY. THIS 
 WILL ALLOW TEMPERATURES TO WARM TO A FEW DEGREES ABOVE NORMAL. MEX 
 GUIDANCE HAS COOLING NEXT TUESDAY DESPITE THE RIDGE...BUT BELIEVE 
 THIS IS THE GUIDANCE TRENDING TOWARD CLIMATOLOGY AT THE END OF THE 
 PERIOD. 
 
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 .AVIATION...
 AREAS OF MVFR CONDITIONS WITH LOCAL IFR IN FOG WILL CONTINUE ACROSS 
 THE SAN JOAQUIN VALLEY THROUGH 18Z TUESDAY. IFR CONDITIONS WILL 
 BECOME MORE WIDESPREAD THROUGH 15Z AND THEN BEGIN DISSIPATING AFTER 
 SUNRISE. OTHERWISE...VFR CONDITIONS WILL PREVAIL ELSEWHERE IN THE 
 CENTRAL CALIFORNIA INTERIOR THROUGH 12Z WEDNESDAY.
 
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 .AIR QUALITY ISSUES...
 ON TUESDAY NOVEMBER 24 2009...FIREPLACE/WOOD STOVE BURNING IS
 PROHIBITED IN KERN COUNTY. FURTHER INFORMATION IS AVAILABLE AT
 VALLEYAIR.ORG
 
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 .HNX WATCHES/WARNINGS/ADVISORIES...
 NONE.
 
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