FXUS66 KSTO 291747
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
945 AM PST SUN NOV 29 2009

.DISCUSSION...
AN ELY GRADIENT OF 10 MBS FROM RNO-SAC SUPPORTING DOWNSLOPE FLOW 
OVER SIERNEV AND TOPOGRAPHICALLY INDUCED NLY WINDS FOR THE VALLEY. A 
WEAKENING OF UPPER LEVEL SUPPORT ALSO RESULTED IN A WEAKENING OF THE 
NLY BARRIER JET...BUT IT WAS STILL EVIDENT AT VCB/SUU FOR MUCH OF 
THE NITE AS INDICATED BY THE NAM 925 MBS WINDS. THESE WINDS ARE 
FORECAST TO CONTINUE TO WEAKEN SIGNIFICANTLY DURING THE AFTN AND 
WIND GUSTS SHOULD DIMINISH...ALLOWING FOR A PLEASANT AND MILD LATE 
NOV DAY IN NORCAL. ONLY A COUPLE OF SITES IN ZONE 69 REMAIN AT WAD 
CRITERIA...AND WILL LET IT EXPIRE AS GUSTS WILL DECREASE OVER THE 
HIGHER ELEVATIONS AS WELL.  

A POSITIVELY TILTED RIDGE WILL BUILD INLAND TODAY WITH GOOD SYNOPTIC 
WARMING. AREA MORNING RAOBS INCREASE SURFACE TEMPS BY 3 TO 7 
DEG...WHILE GREATER WARMING IS NOTED ALOFT. THUS THE HIGHER 
ELEVATIONS WILL BE WELL INTO THE TEMP INVERSION AND WILL HAVE SOME 
MILD DAYTIME TEMPS FOR THE NEXT COUPLE OF DAYS. A WEAK SHORT WAVE IS 
FORECAST TO RIDE OVER THE TOP OF THE RIDGE ON TUE WHICH MAY SUPPRESS 
HEIGHTS ENOUGH TO BRING SOME HIGH CLOUDS INTO THE AREA. OTHERWISE 
THE ERN PAC RIDGE WILL RE-AMPLIFY ALONG THE COAST AND CONTINUE DRY 
AND MILD WX CONDITIONS FOR NORCAL FOR THE REST OF THE WEEK. THE 
PATTERN IS FORECAST TO CHANGE BY NEXT WEEKEND WITH THE DETAILS STILL 
A LITTLE UNCERTAIN. 

WE EXPECT THE AIR MASS TO REMAIN QUITE DRY TONITE...AND LOOK FOR 
IMPROVEMENT IN DEWPOINTS AS PRESSURE GRADIENTS WEAKEN DURING THE DAY 
ON MON AND INTO TUE MORNING. THUS...SOME FOG MAY RETURN TO THE VLYS 
BY TUE MORNING...HOWEVER IT APPEARS LIGHT NLY FLOW WILL PRECLUDE 
WIDESPREAD FOG DEVELOPMENT THIS WEEK.       JHM

.EXTENDED DISCUSSION (THURSDAY THROUGH SUNDAY)...
HIGH PRESSURE WILL REMAIN OVER THE REGION FOR DRY WEATHER THURSDAY 
AND FRIDAY OF THIS WEEK. THERE IS A LOT OF UNCERTAINTY IN THE 
WEATHER PATTERN FOR NEXT WEEKEND. MODELS DIFFER WITH POSITIONS OF 
SYSTEMS...EITHER BRINGING A COUPLE THROUGH FROM THE WEST OF 
RETROGRADING A SYSTEM FROM OVER IDAHO BACK OVER THE REGION. EITHER 
WAY THE IF EITHER SOLUTION WORKS OUT THEN THERE COULD BE SOME 
UNSETTLED WEATHER OVER THE REGION. IF THE LATTER SOLUTION WORKS OUT 
THEN SOME COLD WEATHER COULD BE ADVECTING INTO THE REGION FOR NEXT 
WEEKEND AS WELL.

&&

.AVIATION...
VFR CONDITIONS ACROSS THE AREA OVER THE NEXT 24 HOURS. NORTHEAST TO 
EAST WIND GUSTS TO AROUND TO 35-50 KT OVER HIGHER TERRAIN AND 
THROUGH CANYONS THROUGH 18Z THIS MORNING. NORTHERLY FLOW 10-15 KT 
EXPECTED TODAY AT THE TAF SITES NORTH OF KSCK TODAY...WEAKENING BY 
MID AFTERNOON.
&& 

.STO WATCHES/WARNINGS/ADVISORIES...
...WIND ADVISORY EXPIRES AT 10 AM PST THIS MORNING FOR WEST SLOPE  
NORTHERN SIERRA NEVADA-WESTERN PLUMAS COUNTY/LASSEN PARK-            
NORTHEAST FOOTHILLS/SACRAMENTO VALLEY.

&&

$$