Small Craft Advisory 888, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST MON DEC 5 2011

.ANALYSIS AND UPPER LEVELS...UPPER LEVEL PATTERN TODAY HAS THE RIDGE
OVER THE PACIFIC NORTHWEST AND A TROUGH IN THE FAR WESTERN BERING
SEA. THIS IS PRODUCING SOUTHWEST TO WEST UPPER LEVEL FLOW OVER THE
SOUTHERN PART OF THE STATE TODAY. THERE ARE ALSO SOME SHORT WAVES
MOVING EASTWARD ACROSS THE KUSKOKWIM VALLEY THAT WILL MOVE ACROSS THE
SUSITNA VALLEY AND INTO THE COPPER RIVER BASIN OVERNIGHT.
THE UPPER LEVEL PATTERN WILL AMPLIFY INTO MID WEEK WITH A RIDGE
BUILDING NORTHWARD OVER THE EASTERN GULF OF ALASKA AND THE TROUGH
DIGGING SOUTHWARD AND MOVING TO THE EAST. THIS WILL INCREASE THE
SOUTHWEST JET OVER THE MAINLAND PART OF THE STATE MIDWEEK.

AT THE SURFACE THERE IS HIGH PRESSURE BUILDING INTO SOUTH CENTRAL
ALASKA WITH A MODERATE LARGE IN THE WESTERN ALEUTIANS. THIS LOW WILL
DEVELOP A TRIPLE POINT LOW TOMORROW THAT WILL MOVE INTO THE NORTHERN
BERING SEA BY MIDWEEK AND BECOME THE DOMINANT WEATHER FEATURE BY
THEN.

.MODEL DISCUSSION...OVERALL THE MODELS ARE DOING WELL. THERE IS SOME
DIFFERENCE IN THE RESOLVING OF THE LOW AND DEVELOPING TRIPLE POINT
LOW IN THE CENTRAL AND WESTERN ALEUTIANS THROUGH MID WEEK. THE
GFS/NAM SOLUTIONS TAKING IT FARTHER NORTH AND EAST. THE ECMWF/UKMET
SOLUTIONS HAS THE TRIPLE POINT ROTATING BACK TO THE NORTHWEST AROUND
THE DISSIPATING PARENT LOW WHICH WILL NOT PUSH THE WARM AIR AS FAR
NORTH WITH THIS SOLUTION. THE CONSISTENCY OF THE ECMWF AND UKMET
SOLUTIONS IS A BIT BETTER THAN THE NAM OF GFS AND THE UPPER LEVEL
FLOW IS MORE CONDUCIVE FOR THE ECMWF SOLUTION SO THAT WAS USED IN THE
WESTERN PART OF THE AREA.
THE MODELS ARE ALL HINTING AT THE DEVELOPMENT OF A TRIPLE POINT LOW
IN THE NORTHWEST GULF OF ALASKA WEDNESDAY WHICH WILL BE A BIG PLAYER
IN HOW MUCH PRECIPITATION AND WHAT TYPE OF PRECIPITATION MOVES INTO
SOUTH CENTRAL ALASKA MID WEEK. AS OF NOW THE NAM PROBABLY HAS THE
BEST HANDLING OF THIS FEATURE.

.SHORT TERM FORECAST...A FRONT WELL AHEAD OF THE LOW IN THE WESTERN
ALEUTIANS WILL MOVE TOWARD THE SOUTHWEST ALASKA COAST TUESDAY. THE
POTENTIAL FOR BLIZZARD CONDITIONS ALONG THE COAST IN THE KUSKOKWIM
DELTA HAS PROMPTED THE BLIZZARD WATCH. THE BIGGEST QUESTION ABOUT
WHETHER THIS WILL FULLY MATERIALIZE IS DUE TO THE AMOUNT OF WARM AIR
THAT WILL MOVE INTO THE AREA. THE TEMPERATURES MAY  GET WARM ENOUGH
TO TURN THE PRECIPITATION TO RAIN TOMORROW. IF NOT THERE WILL LIKELY
BE BLIZZARD CONDITIONS. THAT IS THE BIG QUESTION AT THIS TIME.
THE SHORT WAVES MOVING ACROSS THE KUSKOKWIM VALLEY BRING THE CHANCE
OF SNOW SHOWERS TO THIS AREA AS WELL AS THE MATSU AREA OVERNIGHT.
PRECIPITATION WILL BE MOSTLY ALONG THE MOUNTAINS AND NOT EXPECTED TO
AMOUNT TO MUCH.
BY WEDNESDAY THERE IS MORE WARM AIR MOVING INTO THE GULF REGION AND
SOUTH CENTRAL ALASKA. THIS IS NOT NEARLY AS WARM AS THE PUSH THIS
WEEKEND AND A TRIPLE POINT LOW IS EXPECTED TO DEVELOP IN THE
NORTHWEST GULF WEDNESDAY WHICH WILL PUSH THE WARMEST AIR EASTWARD AND
ALONG THE NORTH GULF COAST. THE ANCHORAGE AREA COULD SEE A MIXED BAG
OF PRECIPITATION TYPES WITH THIS SYSTEM BUT MOST LIKELY WILL HAVE
PRECIPITATION CUT OFF BY DOWNSLOPING WEDNESDAY AND THEN BE COOL
ENOUGH FOR SNOW WEDNESDAY NIGHT WHEN PRECIPITATION IS MORE LIKELY.
THE KENAI PENINSULA THROUGH MATANUSKA VALLEY IS ON THE EDGE OF THE
RAIN SNOW LINE SO THERE IS STILL A BIT OF UNCERTAINTY ABOUT THE
PRECIPITATION TYPES AT THIS TIME.

.LONG TERM FORECAST...THE AMPLIFIED PATTERN WILL REMAIN THE NORM
THROUGH THE EXTENDED FORECAST WITH A STORM TRACK SIMILAR TO THE LAST
WEEK. LOWS WILL MOVE UP INTO THE BERING STRETCHING FRONTS EASTWARD
ACROSS THE SOUTHERN MAINLAND. INTERMITTENT BREAKS IN THE WEATHER WILL
OCCUR BETWEEN FRONTS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 155.
MARINE...GALE 120 150 160 171 172 175 176 179 180 185.
         STORM 155 170.
         HEAVY FREEZING SPRAY 185.
FIRE WEATHER...NONE.

DEC 11