FXUS66 KSTO 281800
AFDSTO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
930 AM PST SAT NOV 28 2009

.DISCUSSION...
THE NLY MFR-SAC GRADIENT HAS NOW INCREASED TO 17 MBS WITH RDD-SAC AT 
8 MBS...AND THE DEVELOPMENT OF A NLY BARRIER JET. STAUDENMAIER 
(1994) DISCUSSED HOW 3 FACTORS CAN BE OBSERVED ON THE KOAK SOUNDING 
FOR SUCH A PHENOMENON: 1) DEEP NELY FLOW, 2) STRONG STABILITY AND 3) 
A CAPPING INVERSION. THE 18Z NAM 925 MBS WINDS SHOW A BAND OF N TO 
NELY WINDS FROM THE UPPER 30S KT RANGE AROUND RDD TO NEAR 50 KTS IN 
WRN SOLANO CO...AND THESE WINDS ARE INDICATIVE OF THE GUSTS THAT 
HAVE/ARE OCCURRING AROUND THE AREA...SUU G49 KTS...VCB G43 
KTS...SAC G37 KTS. THE WINDS ACROSS THE NRN HALF OF THE SAC VLY HAVE 
NOT QUITE MATERIALIZED YET...BUT BUFKIT MOMENTUM TRANSFER INDICATES 
THE POTENTIAL FOR GUSTS OVER 35 KTS AT SOME LOCATIONS AS SURFACE 
HEATING/MIXING INCREASE BY MIDDAY. FOR THE TIME BEING...THE WRN 
FOOTHILL LOCATIONS ARE VERIFYING THE WAD WHERE THE BARRIER JET IS 
LOCATED. THE 925 MBS WIND FORECAST SUGGESTS THE BARRIER JET WILL 
WEAKEN AFT 00Z...ALTHO IT MAY PERSIST IN WRN SOLANO CO INTO THE 
EVENING...03Z-06Z OR SO. THIS WILL BE ONE AREA WHERE WE MAY NEED TO 
EXTEND THE WAD FOR SEVERAL HRS...WHILE WINDS WILL BE DECREASING 
ELSEWHERE. 

FOR THE MTNS IT IS A LITTLE DIFFERENT SCENARIO AS THE NLY GRADIENT 
IS FORECAST TO SHIFT TO A MORE ELY GRADIENT TONITE AND SUN AS 
SURFACE HIGH PRESSURE OVER ORE MOVES INLAND TO ID AND NV. STRONG 
SUBSIDENCE OF 12 UBAR/S IS FORECAST OVER THE W SLOPE OVERNITE BUT 
WINDS ALOFT ARE FORECAST TO WEAKEN FROM 33-55 KTS TODAY TO 25-30 KTS 
TONITE AND SUN. THE STRONGEST WINDS WILL BE IN THE MORE E TO W 
ORIENTED CANYONS...AND ELSEWHERE WIND GUSTS WILL NOT BE AS STRONG AS 
THIS MORNING. 

OTHERWISE DRY WX IS EXPECTED OVER INTERIOR NORCAL AS A POSITIVELY 
TILTED RIDGE BUILDS OVER THE AREA FOR THE NEXT FEW DAYS...AND 
YESTERDAY'S CLOSED LOW...NOW OVER SOCAL...DROPS SWD INTO OLD MEX. 
CYCLONIC FLOW N OF THE CLOSED LOW WILL TRANSITION TO ANTICYCLONIC 
TONITE AND SUN...AND THE BACKWASH CLOUDS BANKING UP AGAINST THE E 
SLOPES OF THE SIERNEV IN OUR SRN ZONE 69 WILL BE ERODING/ 
DISSIPATING. RADAR DETECTS SOME LIGHT SNOW OR FLURRIES SPILLING OVER 
THE E SLOPES AND INTO OUR ALPINE CO AND ERN TUOLUMNE COUNTIES. THIS 
OFFSHORE FLOW PATTERN WILL PRECLUDE FOG...RESULT IN MAINLY CLEAR 
SKIES...COLD MINS DUE TO DRY CONDITIONS AND STRONG RADIATIONAL 
COOLING WHERE WINDS DIMINISH...AND SEASONABLY MILD DAYTIME TEMPS FOR 
THE NEXT FEW DAYS.     JHM              

.EXTENDED DISCUSSION (WEDNESDAY THROUGH SATURDAY)...MODELS 
INDICATING VARYING SOLUTIONS DURING THE EXTENDED PERIOD. A LOW 
PRESSURE AREA THAT WILL BE OFF THE COAST IS EITHER PROJECTED TO 
SWING WELL SOUTH OF OUR AREA OR MOVE PARTIALLY INTO THE REGION ON 
WEDNESDAY. HAVE CONTINUED THE DRY FORECAST FOR NOW BUT THAT COULD 
CHANGE. THE OTHER HINT OF ANYTHING COMES NEXT FRIDAY WITH A 
SHORTWAVE MOVING INTO THE PACIFIC NORTHWEST. THE GFS IS INDICATING A 
LOW FORMING ALONG THE COAST WHILE THE EUROPEAN KEEP THE SHORTWAVE TO 
THE NORTH. AGAIN HAVE CONTINUED THE DRY FORECAST FOR NOW UNTIL THE 
MODELS CAN COME INTO A BETTER AGREEMENT INTO WHAT IS GOING ON.

&&

.AVIATION...
VFR CONDITIONS OVER THE SACRAMENTO AND NORTHERN SAN JOAQUIN VALLEYS 
WITH JUST SOME LIGHT LINGERING SNOW SHOWERS CREATING MVFR CONDITIONS 
ALONG THE CREST WHICH WILL END BY AROUND 21Z. NORTH WINDS 15-30KT 
WITH LOCAL GUSTS UP TO 45KT WILL BLOW DOWN THE VALLEY...WITH THE 
STRONGEST WINDS ALONG THE WEST SIDE OF THE VALLEY. VALLEY WINDS WILL 
BEGIN TO SUBSIDE BY 00Z. MOUNTAINS GUSTS 40-60 KT POSSIBLE OVER 
HIGHER TERRAIN AND THROUGH CANYONS TONIGHT.

&& 

.STO WATCHES/WARNINGS/ADVISORIES...
...WIND ADVISORY THROUGH 5 PM PST THIS EVENING FOR SACRAMENTO AND    
   NORTHERN SAN JOAQUIN VALLEYS INCLUDING THE DELTA REGION ALONG     
   WITH THE COASTAL RANGE INCLUDING SOUTHWESTERN SHASTA AND LAKE     
   COUNTIES. 
...WIND ADVISORY THROUGH 8 AM PST SUNDAY FOR WEST SLOPE NORTHERN     
   SIERRA NEVADA-WESTERN PLUMAS COUNTY/LASSEN PARK.

&&

$$