FXUS66 KSTO 251716
AFDSTO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
900 AM PST WED NOV 25 2009
.DISCUSSION...
UPPER LEVEL RIDGE OF HIGH PRESSURE OVER THE AREA THIS MORNING AND
WILL MOVE EAST DURING THE DAY. THIS WILL BRING ANOTHER NICE FALL DAY
TODAY WITH TEMPERATURES IN THE MID 60S TO LOWER 70S IN THE VALLEY TO
THE MID 50S TO MID 60S IN THE HIGHER ELEVATIONS. PATCHY FOG FROM
AROUND MARYSVILLE SOUTH THIS MORNING TO AROUND MODESTO IS STARTING
TO DISSIPATE AND SHOULD DIMINISH BY AROUND 10 AM. THIS MORNINGS LOW
TEMPERATURES GENERALLY IN THE MID TO UPPER 30S IN THE
VALLEY...EXCEPT RED BLUFF IS WARMER WITH THE NORTHERLY WINDS
CONTINUING OVERNIGHT FOR A LOW OF ONLY 45. MOUNTAIN LOW TEMPERATURES
GENERALLY VARIED FROM THE MID 30S TO 40S. LOCALLY GUSTY NORTHEAST
WINDS IN THE SIERRA AGAIN THIS MORNING WITH SURFACE HIGH PRESSURE
OVER THE GREAT BASIN.
THE WEATHER PATTERN CHANGES TOMORROW WITH THE RIDGE SHIFTING TO THE
EAST AND A TROUGH APPROACHING THE WEST COAST. THE 12Z MODELS HAVE
THIS SYSTEM ENTERING INTERIOR NORTHERN CALIFORNIA EARLY FRIDAY
MORNING AND SPREADING SOUTHEAST ACROSS THE AREA BY NOON. THE 12Z GFS
HAS PRECIPITATION FURTHER SOUTH THAN THE 06Z RUN AND THAN THE
CURRENT FORECAST SO WILL PROBABLY BUMP UP POPS FOR FRIDAY AFTER LOOK
AT ALL 12Z MODELS. PRECIPITATION WATER AROUND A HALF TO 0.75 INCHES
WITH MOST OF THE PLUME STAYING ALONG THE COAST. DYNAMICS NOT REAL
STRONG WITH A 100 KT NORTH-SOUTH ORIENTED JET MOVING THROUGH NORTH
OF INTERSTATE 80 EARLY FRIDAY MORNING. GFS IS COLDER WITH THIS
SYSTEM THAN THE NAM WITH 700 MB TEMPERATURES AROUND -4 AND
1000-500MB THICKNESSES AROUND 5520M COMPARED TO -2 AND 5500M,
RESPECTIVELY ON THE NAM AT 12Z FRIDAY. SNOW LEVELS WILL BE AROUND
5000 TO 6000 FEET...WITH LOCALLY LOWER LEVELS POSSIBLE. THE HIGHER
MOUNTAIN PASSES MAY GET A FEW INCHES OF SNOW FRIDAY. RIDGE OF HIGH
PRESSURE BUILDS IN BEHIND THIS SYSTEM FOR DRIER AND WARMER WEATHER
FOR THE WEEKEND. NORTH TO EAST WINDS ARE ALSO EXPECTED TO RETURN
OVER THE WEEKEND.
.PREVIOUS EXTENDED DISCUSSION (SUNDAY THROUGH WEDNESDAY)...
HIGH AMPLITUDE RIDGE REBUILDS OFF THE WEST COAST SUNDAY AND SHIFTS
INLAND MONDAY. THE ECMWF FLATTENS THE RIDGE SOMEWHAT MONDAY AS A
SHORTWAVE MOVES BY TO THE NORTH...HOWEVER THE GEM AND GFS KEEP THIS
FEATURE TOO FAR NORTH TO HAVE ANY INFLUENCE ON THE RIDGE. 850MB
TEMPERATURES RECOVER TO THE 6C-9C RANGE AND SURFACE HIGH PRESSURE
OVER THE GREAT BASIN WILL CONTINUE THE PATTERN OF LOCALLY BREEZY
NORTH TO EAST WINDS. FOG SHOULD BE PATCHY AND LIMITED TO THE LATE
NIGHT AND EARLY MORNING HOURS IN PRONE AREAS. THIS PATTERN WOULD
FAVOR ABOVE NORMAL TEMPERATURES. THE MODELS AMPLIFY THE RIDGE WELL
NORTH INTO BRITISH COLUMBIA/YUKON BY TUESDAY...WITH VARYING AMOUNTS
OF SHORTWAVE ENERGY DROPPING DOWN THE BACK SIDE OF THE RIDGE. THE
18Z DGEX AND 12Z GFS FROM YESTERDAY WERE SUGGESTING THAT AN
UNDERCUTTING OF THE WESTERLIES COULD OCCUR TOWARD THE MIDDLE OF NEXT
WEEK...AND SEVERAL OF THE GFS ENSEMBLES SUPPORT THIS AS WELL. BUT
THE 06Z DGEX AND GFS HAVE BACKED AWAY FROM THIS. SG
&&
.AVIATION...
HIGH PRESSURE ALOFT REMAINS IN PLACE OVER CALIFORNIA WITH SURFACE
HIGH PRESSURE OVER THE GREAT BASIN. AREAS MVFR CIGS VSBY IN FOG WILL
IMPACT KSMF...KSAC AND KMHR UNTIL 17Z THIS MORNING. OTHERWISE VFR
CONDITIONS EXPECTED BEYOND 18Z ALL AREAS. LOCAL E SFC WNDS G30-40KT
THIS MORNING ALONG W SLOPE OF THE SIERRA CANYONS. FOG MAY BE A
CONCERN AGAIN THU MORN. JMC
&&
.STO WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
