Small Craft Advisory 987, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST MON DEC 9 2013

.ANALYSIS AND UPPER LEVELS...THE UPPER LEVEL RIDGE THAT HAS BEEN OVER
THE STATE IS STILL IN PLACE BUT IS WEAKENING AS AN UPPER LEVEL TROUGH
IN THE BERING SEA MOVES EASTWARD AND UNDERCUTS IT. THIS IS IN
CONJUNCTION WITH A PATTERN CHANGE WHICH WILL PUT THE UPPER LEVEL LOW
OVER THE MAINLAND PART OF THE STATE WITH A RIDGE OVER THE WESTERN
BERING SEA FOR THE SECOND HALF OF THE WEEK. THIS WILL ALSO BRING MORE
SEASONAL TEMPERATURES OVER THE STATE AS THE WARMEST AIR MOVES ON TO
THE SOUTHEAST.
AT THE SURFACE THE IS HIGH PRESSURE PERSISTING OVER THE MAINLAND PART
OF THE STATE...EXTENDING OUT OF THE LARGE RIDGE IN THE GULF OF
ALASKA. THE LOW SOUTH OF THE ALASKA PENINSULA IS PUSHING NORTHEAST
AND WILL DISPLACE THE SURFACE RIDGE AS THE UPPER LEVEL PATTERN
SHIFTS.

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT WITH THE SYNOPTIC
PATTER FOR MOST OF THE WEEK. THE BIGGEST DIFFERENCE IN THE MODELS IS
IN REGARD TO THE LOW THAT IS CURRENTLY WELL SOUTH OF THE ALASKA
PENINSULA THAT WILL TRACK INTO THE GULF OF ALASKA LATER IN THE WEEK.
THE MODELS ALL TRACK TO LOW TO A SIMILAR LOCATION...HOWEVER THERE IS
NO AGREEMENT IF THE LOW WILL ELONGATE INTO MULTIPLE CENTERS AND IF SO
WHICH CENTER WILL HAVE THE GREATEST AMOUNT OF ENERGY. AS SUCH THE
CENTRAL PRESSURES VARY BY AROUND 10 MB ON THESE MODELS AS WELL. THESE
DIFFERENCES WILL LIKELY GET IRONED OUT AS THE WEEK GOES ON AND THE
MODELS GET A BETTER HANDLE ON THE DEVELOPMENT OF THIS LOW.

.SHORT TERM FORECAST...FOG IS DISSIPATING OVER SOUTH CENTRAL ALASKA
AS THE UPPER LEVEL WARM CORE RIDGE WEAKENS. THERE WILL ALSO BE
PARTIAL CLEARING AS THE LOW MOVES INTO THE GULF AND THE SURFACE RIDGE
PERSISTS OVER NORTHERN ALASKA. AN UPPER LEVEL SHORT WAVE WILL MOVE
OUT OF NORTHERN ALASKA AND INTO SOUTH CENTRAL ALASKA BY LATE TUESDAY.
THIS WILL KEEP THE AREA FROM CLEARING OUT COMPLETELY...AND THE COPPER
RIVER BASIN WILL LIKELY REMAIN CLOUDY UNDER THIS SHORT WAVE.
THIS PATTERN IS ALSO SHAPING UP FOR SOME STRONG OUTFLOW WINDS TO
DEVELOP ALONG THE NORTH GULF COAST AND NORTH-SOUTH ORIENTED THROUGH
CHANNELED TERRAIN.

SOUTHWEST ALASKA....THERE SHOULD BE AN OVERALL TREND OF DECREASING
CLOUDS OVER THE NEXT DAY OR TWO. THERE WILL BE SOME AREAS OF FOG
TONIGHT BUT THOSE SHOULD ALSO DIMINISH TOMORROW AS THE PRESSURE
GRADIENT INCREASES AND BRINGS BETTER MIXING TO THE ATMOSPHERE.

.LONG TERM FORECAST...MODELS ARE ALL SUPPORTING A BROAD UPPER LEVEL
TROUGH CENTERING OVER THE SOUTHERN MAINLAND AT THE END OF THE WEEK
WITH A RIDGE AMPLIFYING OVER KAMCHATKA. COLD TEMPERATURES WILL STAY
IN PLACE ACROSS MUCH OF THE STATE THROUGH THE WEEKEND. HOWEVER...A
WARM FRONT WILL PUSH INTO THE THE GULF WATERS AT THE END OF THE WEEK
BRINGING A WARM MOIST AIR MASS TO THE NORTHERN GULF. DISTURBANCES
ASSOCIATED WITH THE TROUGH BRING INCREASED PRECIPITATION CHANCES
ACROSS SOUTHERN ALASKA AND THE BERING INTO THE WEEKEND.
THIS WILL BRING A CHANCE FOR SOME SNOW INTO SOUTH CENTRAL ALASKA THIS
WEEKEND BUT ACTUAL LOCATION OF THE LOW AND HOW FAR THE FRONT PUSHES
WESTWARD WILL BE KEY INGREDIENTS AS TO WHETHER THERE IS SNOW OR IF
THERE IS ENOUGH WARM AIR MOVING IN TO CAUSE SOME OF IT TO TURN TO
RAIN. THIS SYSTEM WILL BE ONE TO WATCH AS THE WEEK PROGRESSES.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 150 155.
FIRE WEATHER...NONE.

DEC 13