Small Craft Advisory 937, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SUN NOV 24 2013

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE BERING SEA. A WEAK WARM FRONT
ASSOCIATED WITH THIS LOW IS OVER SOUTH CENTRAL ALASKA...AND AN
OCCLUDED FRONT IS OVER SOUTHWEST ALASKA AND STRETCHES SOUTHWARD.
ALONG THIS FRONT THERE IS A DEVELOPING LOW SOUTH OF KODIAK MOVING
TOWARD THE NORTH-NORTHEAST. THERE IS A RIDGE OF HIGH PRESSURE OVER
THE NORTHERN GULF. THERE IS ANOTHER RIDGE OVER KAMCHATKA WHICH WILL
PLAY A SIGNIFICANT ROLE IN THE FORECAST BY MID-WEEK.

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE ONLY IN FAIR AGREEMENT TODAY. THEY ARE
STRUGGLING WITH TIMING/LOCATION OF A LOW MOVING INTO THE NORTHERN
GULF AND WITH HOW THEY ARE HANDLING THE SITUATION FURTHER SOUTH IN
THE SOUTHERN GULF THROUGH WEDNESDAY. ALL THE MODELS ARE HANDLING THE
DEVELOPMENT OF THE BLOCK OVER THE BERING VERY WELL. THE ECMWF IS THE
PREFERRED SOLUTION...WITH THE GEM A CLOSE SECOND. FOR THE EXTENDED
FORECAST (PAST WEDNESDAY) THE GLOBAL MODELS AGREE ON THE LOCATION OF
THE BLOCK FAIRLY WELL...BUT THE DETAILS ON HOW THEY HANDLE THE
DOWNSTREAM FLOW SHOWS QUITE A BIT OF SPREAD.

.SHORT TERM FORECAST...
FOR SOUTH CENTRAL ALASKA...THE WARM FRONT WILL MOVE THROUGH SOUTH
CENTRAL ALASKA AND DISSIPATE TONIGHT. THE RIDGE OVER THE NORTHERN
GULF WILL SLIDE NORTH INTO THE AREA BY MONDAY MORNING. THE SYSTEM
SOUTH OF KODIAK WILL PUSH NORTH-NORTHEAST TO THE GULF COAST MONDAY
AFTERNOON AND THEN FURTHER INLAND MONDAY NIGHT. MOST OF THE
PRECIPITATION WITH THIS SYSTEM WILL BE ALONG THE GULF COAST AND
PRINCE WILLIAM SOUND (PWS). FOR THE COPPER RIVER BASIN AS WELL AS
THE WESTERN KENAI THROUGH ANCHORAGE AND THE MATANUSKA/SUSITNA AREAS
THE CHANCES ARE LOWER WITH LESS MOISTURE AND SOME MOUNTAIN
PROTECTION. PRECIPITATION TYPE WITH THIS SYSTEM WILL BE A MIX OF
RAIN AND SNOW ALONG THE GULF AND PWS...WITH SNOW FOR THE COPPER
RIVER BASIN AND FOR MOST OF THE WESTERN AREAS. THIS SYSTEM WILL
DISSIPATE ON TUESDAY. BY THIS TIME THE MAIN UPPER LOW THAT HAD BEEN
OVER THE BERING SEA WILL HAVE MOVED INTO THE GULF. THIS WILL KEEP
SOME MOISTURE AND WEAK DYNAMICS OVER SOUTH CENTRAL FOR SOME
LINGERING SHOWERS.

ON WEDNESDAY THE BEGINNINGS OF A PATTERN CHANGE WILL START TO BE
FELT OVER THE AREA. THE FORMER KAMCHATKA RIDGE WILL HAVE TAKEN THE
PLACE OF THE FORMER BERING LOW AND BE IN THE PROCESS OF FORMING A
BLOCK...SPECIFICALLY A REX BLOCK (UPPER HIGH TO THE NORTH OF A LOW).
THIS WILL PUT ALASKA FIRMLY IN THE ARCTIC JET...WITH UPPER LEVEL
NORTHWESTERLY FLOW DEVELOPING OVER ALASKA. THE COLD AIR WILL NOT
YET HAVE ARRIVED IN SOUTH CENTRAL ON WEDNESDAY...BUT THE UPPER LOW
WILL BE IN THE PROCESS OF BEING "EJECTED" BY A SYSTEM RIDING THE
NORTHWEST FLOW.

FOR SOUTHWEST ALASKA...THE FRONT OVER THE AREA WILL REMAIN BASICALLY
STATIONARY THROUGH MONDAY NIGHT THEN DISSIPATE ON TUESDAY. SOUTHEAST
FLOW THROUGH MONDAY WILL CONTINUE TO PUSH WARM AIR INTO SOUTHWEST
ALASKA. ON MONDAY NIGHT AND TUESDAY COLDER AIR WILL RETURN AS THE
LOW LEVEL FLOW TURNS MORE NORTHERLY. EVEN COLDER AIR WILL BEGIN TO
PUSH INTO THE AREA ON WEDNESDAY AS THE PATTERN CHANGE MENTIONED
ABOVE BEGINS TO BE FELT.

.LONG TERM FORECAST...
ALTHOUGH THE MODELS DISAGREE ON THE LOCATION...DETAILS...AND
MAGNITUDE OF THE UPCOMING PATTERN...THEY ALL AGREE ON A SIGNIFICANT
BLOCK OVER THE BERING SEA. THIS WILL TEMPERATURES BELOW NORMAL.
PRECIPITATION WILL PROBABLY BE BELOW NORMAL AS WELL...BUT WITH THE
MODEL DIFFERENCES THE CONFIDENCE IN THIS IS NOT HIGH.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 119 120.
      HEAVY FREEZING SPRAY 181.
FIRE WEATHER...NONE.

LUDWIG NOV 13