Small Craft Advisory 45, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST MON JAN 14 2013

.ANALYSIS AND UPPER LEVELS...THERE ARE A NUMBER OF STRONG UPPER LEVEL
FEATURES ON TODAY WEATHER MAP. A STRONG UPPER LEVEL LOW OVER EASTERN
RUSSIA HAS A SHARP TROUGH DIGGING DOWN OVER THE CENTRAL BERING SEA
AND THE WELL INTO THE NORTHERN PACIFIC. THIS STRONG TROUGH COMBINED
WITH A STRONG UPPER LEVEL RIDGE OFF THE WEST COAST OF NORTH AMERICA
IS CREATING A 250 MB JET IN EXCESS OF 160 KT TO MOVE OUT OF THE
PACIFIC AND OVER KODIAK ISLAND AND FROM THERE THROUGH THE COPPER
RIVER BASIN. THIS IS THE MAIN MOISTURE TAP AND SOURCE OF THE STRONG
WARM ADVECTION OVER SOUTH CENTRAL ALASKA.
AT THE SURFACE THE STRONG SURFACE LOW IS LOCATED IN NORTHWEST ALASKA
WITH A FRONT EXTENDING OUT OF IT INTO COOK INLET THIS AFTERNOON.
BEHIND THIS FRONT THERE IS STRONG COLD ADVECTION THAT HAS DROPPED
MOST OF THE TEMPERATURES IN SOUTHWEST ALASKA BELOW FREEZING BY NOON
TODAY. THIS COLD AIR WILL MOVE RAPIDLY INTO SOUTH CENTRAL ALASKA
OVERNIGHT TONIGHT.
THERE IS ALSO A LARGE STORM OFF THE COAST OF JAPAN WITH A CENTRAL
PRESSURE AROUND 936 MB WHICH IS MOVING TOWARD THE BERING SEA. THIS
STORM WILL BECOME THE MAIN WEATHER FEATURE IN THE BERING SEA AND
ALEUTIAN ISLANDS THROUGH THE MIDDLE OF THE WEEK.

.MODEL DISCUSSION...MODELS ARE DOING VERY WELL IN THE BERING SEA
HANDLING THE LARGE LOW THAT IS SOUTHWEST OF ATTU AND MOVING IT TOWARD
THE BERING SEA. IN THE GULF OF ALASKA THE FEATURES ARE MUCH WEAKER
AND THE MODELS ARE SHOWING THE SAME BASIC PATTERN BUT THE DETAILS ARE
A BIT MORE MUDDLED. THE BEST COMBINATION IN THE EAST LOOKS TO BE  THE
NAM FOR THE FIRST DAY OR TWO WITH THE ECMWF PREFERRED AFTER THAT. THE
BERING SEA MODEL SOLUTIONS SHOW VERY GOOD CONSISTENCY IN BOTH THE
STRENGTH AND MOVEMENT OF THIS LARGE STORM.

.SHORT TERM FORECAST...THE BERING SEA AND SOUTHWEST ALASKA AREAS ARE
IN THE COLD ADVECTION BEHIND THE FRONT. THIS IS ALSO USHERING IN SOME
SNOW SHOWERS TO THESE AREAS. THIS COLD AIR WILL MOVE INTO SOUTH
CENTRAL TONIGHT. A QUESTION ABOUT THE WEATHER IN THE COOK INLET
REGION ESPECIALLY IS WHETHER THERE WILL BE WIDESPREAD FOG AND STRATUS
OR JUST A LITTLE PATCHY FOG. NORMALLY AFTER A SIGNIFICANT WINTER TIME
RAIN EVENT WIDESPREAD FOG AND STRATUS DEVELOPS AS THE COLD AIR MOVES
IN AND AFTER THE WIND DIMINISHES. THERE ARE SOME SIGNS THAT THIS MAY
OT BE THE CASE THIS TIME DUE TO WEAK LOW LEVEL LIFTING REMAINING OVER
THE COOK INLET REGION AND THE PERSISTENCE OF MID LEVEL CLOUDS.
HOWEVER IN AREAS WHERE IT DOES CLEAR OUT THERE WILL LIKELY BE FOG AND
STRATUS DEVELOPMENT.

.LONG TERM FORECAST...
THE LATTER PORTION OF THE WEEK WILL HAVE THE UPPER LEVEL RIDGE IN THE
EASTERN BERING WEAKENING AS ITS CREST PINCHES OFF INTO AN UPPER HIGH
OVER EASTERN SIBERIA. IMPULSES OF ENERGY FROM THE ALEUTIAN SYSTEM
WILL BEGIN TO NUDGE THE SOUTHERN PORTION OF THE RIDGE EAST INTO THE
GULF OF AK. THIS WEEKEND INTO EARLY NEXT WEEK...A COMPLEX UPPER LOW
WILL MEANDER OVER THE ALEUTIAN CHAIN WHILE THE AFOREMENTIONED RIDGE
BUILDS INTO THE EASTERN GULF. THIS WILL EVENTUALLY ALLOW
ENERGY/MOISTURE TO MOVE BACK NORTH TOWARDS THE SOUTHERN MAINLAND
AND ONCE AGAIN BRING SOME WARMING TEMPERATURES...THOUGH NOT AS WARM
AS TEMPERATURES FROM THIS PAST WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH 191.
MARINE...GALE 172. STORM 175 176. HEAVY FREEZING SPRAY 185.
FIRE WEATHER...NONE.

JAN 13