Small Craft Advisory 27, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST TUE JAN 8 2013

.ANALYSIS AND UPPER LEVELS...THERE IS A HIGH AMPLITUDE PATTERN OF
RIDGING AND TROUGHS IN THE UPPER LEVELS OVER THE STATE TODAY. A SHARP
UPPER LEVEL TROUGH EXTENDS OUT OF THE YUKON INTO THE EASTERN GULF OF
ALASKA WITH A SHARP RIDGE EXTENDING OUT OF THE NORTH PACIFIC OVER THE
ALASKA PENINSULA AND THEN UP ALONG THE WEST COAST OF THE STATE.
FARTHER WEST LIES A STRONG UPPER LEVEL LOW CENTERED NEAR THE
KAMCHATKA PENINSULA THAT TIGHTENS THE UPPER LEVEL FLOW ACROSS THE
BERING SEA AND ALEUTIANS. THE JET STREAM AT 250 MB IS CURRENTLY
MOVING ACROSS JAPAN AT NEARLY 190 KT AND THEN SPLITS INTO TWO WEAKER
PARTS SOUTH OF ATTU WITH THE NORTHERN LIMB EXTENDING INTO THE CENTRAL
ALEUTIANS THROUGH THE ALASKA PENINSULA.
AT THE SURFACE THERE IS A STRONG LOW NEAR KAMCHATKA WITH A MUCH
WEAKER LOW IN THE CENTRAL GULF OF ALASKA. A SURFACE RIDGE EXTENDS OUT
OF THE PACIFIC INTO EASTERN BRISTOL BAY AND THEN INTO THE INTERIOR OF
THE STATE.

.MODEL DISCUSSION...MODELS ARE DOING WELL WITH THE SYNOPTIC PATTERN
BUT ARE STRUGGLING SOME WITH THE DETAILS OF THE COMPLEX LOW IN THE
BERING SEA. THE COMPLEX LOW IN THE GULF IS WEAKENING AND MODELS ALL
HAVE A COMMON TRACK AND ARE DISSIPATING IT WEDNESDAY MORNING.
THE ECMWF MODELS LOOKS TO HAVE INITIALIZED THE BEST AROUND THE LOW IN
THE BERING SEA AS IT IS THE ONLY ONE TO DETECT THE SECONDARY LOW
CENTER ALONG THE FRONT IN THE NORTHERN BERING.
THE MODELS ARE HAVING A ROUGH PERIOD FROM THURSDAY NIGHT THROUGH
FRIDAY NIGHT WITH A LOW THAT WILL TRACK ACROSS THE GULF FROM THE
SOUTHWEST. THE ECMWF IS BY FAR THE SLOWEST AND STRONGEST OF THE
SOLUTIONS WHILE THE NAM AND GFS ARE MUCH FASTER BUT DIFFER ON TRACK
BY A FEW HUNDRED MILES.
AFTER THIS THE MODELS ACTUALLY IMPROVE AS BOTH THE ECMWF AND GFS HAVE
LOCKED ON TO A STRONG LOW THAT WILL DEVELOP IN THE NORTH PACIFIC
LATER THIS WEEK AND MOVE INTO THE BERING SEA SATURDAY.

.SHORT TERM FORECAST..
THE COMPLEX LOW IN THE WESTERN BERING SEA WILL CONTINUE TO BRING RAIN
AND SNOW SHOWERS TO THE WESTERN AND CENTRAL ALEUTIANS WITH THE FRONT
ASSOCIATED WITH THIS LOW IN THE EASTERN BERING SEA. THIS WILL BRING
RAIN AND STRONG WINDS TO THE EASTERN ALEUTIANS AND ALASKA PENINSULA
THROUGH THE NIGHT.
AREAS OF STRATUS AND FOG ARE OCCURRING IN SOUTHWEST ALASKA UNDER THE
RIDGE. THIS WILL LIFT SOME AS THE FRONT IN THE BERING SEA MOVES OVER
SOUTHWEST ALASKA TONIGHT AND THEN EASTWARD INTO THE BRISTOL BAY
REGION BY EARLY MORNING.
THERE ARE SOME GUSTY OUTFLOW WINDS ALONG THE NORTH GULF COAST AND
KODIAK ISLANDS BUT NOT NEARLY AS STRONG AS THEY OFTEN ARE. LOW LEVEL
CONVERGENCE BETWEEN THE GULF LOW AND THE SOUTHWEST ALASKA RIDGE IS
CAUSING SOME SNOW TO FALL IN THE CHUGACH AND KENAI MOUNTAINS BUT
SHOULD DIMINISH OVERNIGHT AS THE LOW WEAKENS AND MOVES FARTHER
SOUTHEAST.

.LONG TERM FORECAST...BY LATE IN THE WEEK THE GULF OF ALASKA WILL
ONCE AGAIN HAVE A WEAK LOW COMPLEX IN IT WITH A RIDGE IN THE EASTERN
BERING SEA. HOWEVER THE ENERGY IN THE BERING SEA WILL BE ABSORBED
INTO A DEVELOPING NORTH PACIFIC LOW THAT WILL ENTER THE BERING SEA ON
SATURDAY SOMEWHERE BETWEEN 955 AND 960 MB. THIS VERY STRONG LOW WILL
AMPLIFY THE RIDGE OVER THE EASTERN GULF SATURDAY THROUGH MONDAY. THE
RESULT WILL BE VERY STRONG WARM ADVECTION OVER SOUTHERN ALASKA WITH
DUE SOUTH UPPER LEVEL FLOW IN SOUTHWEST ALASKA BRISTOL BAY ON
SUNDAY...SHIFTING OVER SOUTH CENTRAL ALASKA MONDAY. SHOULD THIS
PATTERN VERIFY IT WILL BRING WIDESPREAD RAIN AND WINDS TO SOUTHERN
ALASKA AT TIMES FROM THIS WEEKEND INTO EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 130 132 150 155 170 175 176 185.
FIRE WEATHER...NONE.

JAN 13