AREA FORECAST DISCUSSION

 
 FXUS65 KTWC 241757 AAA
 AFDTWC
 
 AREA FORECAST DISCUSSION...UPDATED
 NATIONAL WEATHER SERVICE TUCSON AZ
 1055 AM MST TUE NOV 24 2009
 
 UPDATED SYNOPSIS
 
 .SYNOPSIS...HIGH PRESSURE ALOFT WILL PROVIDE DRY CONDITIONS WITH 
 ABOVE NORMAL DAYTIME TEMPERATURES THROUGH FRIDAY. A SERIES OF 
 PACIFIC WEATHER SYSTEMS WILL THEN BRING A COOLING TREND TO THE AREA 
 THIS WEEKEND.
 
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 .DISCUSSION...CLEAR SKIES PREVAIL OVER SE AZ THIS MORNING ALONG WITH 
 LIGHT SURFACE WINDS. BONE-DRY SURFACE REGIME WITH DEWPOINTS VALID 
 16Z RANGING FROM THE TEENS-LOWER 20S. 24/12Z KTWC SOUNDING DEPICTED 
 A VERY DRY PROFILE AS WELL...WITH PRECIP WATER VALUE OF 0.20 INCH. 
 NO SIGNIFICANT TEMP CHANGE THROUGHOUT THE COLUMN VERSUS 24 HOURS 
 AGO. 24/12Z UPPER AIR PLOTS INDICATED HIGH PRESSURE RIDGE ADJACENT 
 THE WEST COAST AND RIDGE OVER THE ERN CONUS. LOW PRESSURE SYSTEM WAS 
 OVER FAR NE KANSAS WITH LIGHT WLY/NWLY FLOW OVER SE AZ.
 
 HIGH PRESSURE ALOFT TO BUILD EWD OVER THE AREA THRU THANKSGIVING DAY 
 AS WEAK LOW PRESSURE DEVELOPS OVER THE BAJA CALIFORNIA REGION. DRY 
 CONDITIONS TO PREVAIL TODAY-THUR ALONG WITH ABOVE NORMAL DAYTIME 
 TEMPS. STILL CONTINUED WARM AND DRY FRI AS UPPER RIDGE SHIFTS EWD 
 AND SHORTWAVE TROUGH MOVES ACROSS THE PACIFIC NW. THEREAFTER...
 UPPER TROUGH TO DEEPEN OVER THE SWRN CONUS THIS WEEKEND. THERE WERE 
 DIFFERENCES BETWEEN THE 24/00Z GFS/ECMWF SOLUTIONS REGARDING THE 
 EVOLUTION OF THIS SYSTEM...WITH THE ECMWF STRONGER/DEEPER/SLOWER 
 VERSUS THE GFS. AT ANY RATE...THE INHERITED FORECASTS DEPICT A 
 SLIGHT CHANCE OF SHOWERS ACROSS THE WHITE MOUNTAINS SAT...AS WELL AS 
 A SLIGHT CHANCE OF SHOWERS ERN ZONES SAT NIGHT AND SUN. COOLER SAT 
 AND MUCH COOLER SUN WITH FORECAST HIGH TEMPS NEARLY 10 DEGS OR SO 
 BELOW NORMAL. PRECIP-FREE CONDITIONS AREAWIDE NEXT MON AS THE UPPER 
 LOW MOVES EWD AND RIDGE BUILDS ALONG THE WEST COAST.
 
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 .AVIATION...CLEAR SKIES AND SURFACE WINDS GENERALLY LESS THAN 10 KTS 
 WILL PREVAIL INTO WEDNESDAY MORNING. AVIATION DISCUSSION NOT UPDATED 
 FOR TAF AMENDMENTS.
 
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 .FIRE WEATHER...NO FIRE WEATHER CONCERNS THROUGH FRIDAY. A PACIFIC 
 LOW PRESSURE SYSTEM IS THEN EXPECTED TO MOVE INTO THE AREA THIS 
 WEEKEND. THIS SYSTEM WILL BRING MUCH COOLER TEMPERATURES...GUSTY 
 WINDS AT TIMES...AND A SLIGHT CHANCE OF SHOWERS TO FIRE ZONES 146 
 AND EASTERN 148...OR AREAS EAST OF TUCSON. DRY CONDITIONS WITH LESS 
 WIND NEXT MONDAY AS THE LOW PRESSURE SYSTEM MOVES EASTWARD.
 
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 .TWC WATCHES/WARNINGS/ADVISORIES...NONE.
 
 

 
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