Small Craft Advisory 947, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AST SAT NOV 10 2007

.MODEL DISCUSSION...
MODELS ARE ACTUALLY FAIRLY CONSISTENT WITH THE LARGER SCALE FEATURES
AND SEEM TO HAVE CAUGHT ON TO THE FUNDAMENTAL SHIFT IN THE LONG WAVE
PATTERN THAT HAS BEGUN. HEMISPHERE IS TRANSITIONING FROM AN UNSTABLE
3 WAVE TO A MORE STABLE, SYMETRICAL 4 WAVE WITH THE LONG WAVE TROUGH
SETTING UP VICINITY 150W. THIS PATTERN IS VERY CONSISTENT WITH A
MODERATE LA NINA.

GFS ENSEMBLE MEMBER DIVERGENCE CONTINUES AT THE OUTSET WITH THE 12Z
RUN IN THE DETAILS OF THE LOW FORMING 47N/162W. INTERESTING IS THAT
THE GFS IS NOW KEEPING THE STORM TRACK FURTHER SOUTH IN LINE WITH
WHAT THE ECMF HAS BEEN DOING OVER THE PAST COUPLE OF DAYS. THE
CONVERGENCE OF THE MODELS GIVES ME INCREASING CONFIDENCE IN THE GFS
WITH THE NAM TOO SLOW AND TOO FAR SOUTH AT HOUR 30.

.ANALYSIS AND UPPER LEVELS...
MAIN SURFACE LOW TO THE SOUTHEAST OF KODIAK ISLAND WITH WEAKER
SECONDARY LOW FILLING AND MOVING ACROSS SOUTH CENTRAL ALASKA DURING
THE DAY. SYSTEM VERY SLOW TO MOVE OUT WITH DEFORMATION ZONE
QUASISTATIONARY ACROSS THE ANCHORAGE BOWL ACROSS THE UPPER KUSKOKWIM
VALLEY THROUGH THE EVENING HOURS.

SOUTHERLY BRANCH OF THE POLAR JETSTREAM WELL TO THE SOUTH OF THE
FORECAST AREA. RIDGE ACROSS NORTHWEST CANADA STRENGTHENING AND
UPSTREAM BERING RIDGE EXPECTED TO DEVELOP AT ABOUT HOUR 24. THIS IS
ALL RELATED TO THE SHIFT IN THE LONG WAVE PATTERN.

.SHORT TERM FORECAST...
LIGHT SNOW WILL TAPER OFF SLOWLY ACROSS SOUTH CENTRAL OVERNIGHT.
AMOUNTS WILL BE LIGHT EXCEPT FOR THE WEST SUSITNA VALLEY TOWARDS THE
ALASKA RANGE WHERE HEAVIER AMOUNTS ARE EXPECTED.

LOW CLOUDS WITH FOG AND FLURRIES EXPECTED IN THE SOUTHWEST UNDER AN
ONSHORE FLOW AHEAD OF A WEAK RIDGE. UNSTABLE FLOW WITH NORTHWEST
WINDS WILL COVER THE BERING AND WESTERN ALEUTIANS WITH THE USUAL GALE
FORCE WINDS AND SHOWERS AS LOW DROPS OUT OF SIBERIA.

.LONG TERM FORECAST...
RIDGE FORMING IN WEST BERING WILL ENHANCE COLD NORTHWEST FLOW AND
KEEP STORM TRACK TO THE SOUTH. LOW MOVING OUT OF SIBERIA WILL DROP
INTO BRISTOL BAY EARLY NEXT WEEK BRING STORMY WEATHER TO WESTERN
ALASKA AND THE ALASKA PENINSULA. THE LOW WILL EVENTUALLY DROP INTO
THE GULF OF ALASKA BY MID WEEK LEAVING MOST OF MAINLAND ALASKA IN A
DRY AND COLD PATTERN TYPICAL OF A LA NINA. THE CENTER OF ACTION WILL
REMAIN THE EASTERN BERING AND ALEUTIANS UNDER THE COLD NORTHWEST
FLOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 170 172 175 176.
FIRE WEATHER...NONE.

CAS NOV 07