Small Craft Advisory 959, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SUN DEC 1 2013

.MODEL DISCUSSION...
MODELS OVERALL ARE COMING INTO BETTER AGREEMENT ON THE HANDLING OF
THE LOW COMPLEX OVER THE NORTH PACIFIC. THE GFS/EC ARE IN BETTER
AGREEMENT ON THE POSITIONING OF THE SURFACE FEATURES. THE GFS SEEMS
TO BE A LITTLE SLOW IN BRING PRECIPITATION INTO SOUTHCENTRAL ALASKA.
THE NAM/UKMET/EC ARE IN FAIRLY GOOD AGREEMENT WITH BRINGING A CHANCE
OF SNOW TO SOUTHCENTRAL TUE NIGHT/WED MORNING. THINKING WE WILL AS A
MINIMUM INCREASE CLOUD COVER ACROSS SOUTHCENTRAL TUE NIGHT.

.UPPER LEVELS...
THE OMEGA BLOCK AND IS EXPECTED TO SHIFT EAST SOME THROUGH MID-WEEK.
THOUGH THE RIDGE IN THE BLOCK REMAINS AMPLIFIED ITS EASTWARD MOVEMENT
BRINGS SOUTHERLY WINDS TO WESTERN ALASKA AND WESTERN SOUTHCENTRAL AND
ALLOWS MOISTURE TO CREEP FURTHER WEST. STRONG SUBSIDENCE UNDER THE
HIGH OVER WESTERN ALASKA PRODUCED SIGNIFICANT LOWER TROPOSPHERIC
WARMING AND STRONG NEAR SURFACE INVERSIONS. THESE TYPE OF CONDITIONS
ARE EXPECTED TO SPREAD EAST WITH THE RIDGE STRENGTHENING INVERSIONS
AND CREATE THE POTENTIAL FOR STRATUS AND FOG DEVELOPMENT INTO
SOUTHCENTRAL OVER THE NEXT COUPLE OF DAYS.

STRONG PRESSURE AND TEMPERATURE GRADIENTS CONTINUED ACROSS
SOUTHCENTRAL ALASKA THIS MORNING WITH HIGH WIND WARNING OUTFLOW
CONDITIONS OVER WESTERN AND NORTHERN PRINCE WILLIAM SOUND.

.SHORT TERM FORECAST...
SOUTHCENTRAL...GAP FLOWS WILL DIMINISH THROUGH TODAY AS UPPER JET
SUPPORT SHIFTS EAST AND THE LOWER TROPOSPHERE WARMS. THE RESULTANT
LOOSENING OF THE SURFACE PRESSURE GRADIENTS AND REDUCTION OF THE
OMEGA FIELDS SHOULD ALLOW THE HIGH WIND WARNING IN 131 TO EXPIRE THIS
AFTERNOON. THE 135 WARNING CONDITIONS THROUGH THE COPPER RIVER DELTA
MAY HOLD ON A LITTLE LONGER AS DEEP COLD AIR OVER THE COPPER RIVER
WILL MAINTAIN POTENTIAL FOR STRONG DRAINAGE FLOWS. WILL KEEP AN EYE
ON CONDITIONS AND MAKE A CALL BEFORE THE 4PM PACKAGE ISSUANCE.
MOISTURE SPREADS INTO THE WESTERN GULF TUE AFTERNOON AND SOUTHCENTRAL
TUE NIGHT AND WED.

SOUTHWEST ALASKA...MOISTURE SPREADS INTO SOUTHWEST ALASKA TUE AS THE
UPPER RIDGE MOVES EAST. A SHALLOW COLD LAYER NEAR THE SURFACE AND
WARMING ALOFT WILL BRING THE POTENTIAL FOR FREEZING RAIN TUE AS THE
LOWER ATMOSPHERE BECOMES SATURATED. TEMPS SHOULD WARM ENOUGH ON WED
TO ALL BUT ELIMINATE THE FREEZING RAIN POTENTIAL EXCEPT FOR A FEW
COLD POCKETS OVER THE KUSKOKWIM VALLEY. SOUTHEAST FLOW WILL ALSO
SPREAD ACROSS THE SW MAINLAND AND PROBABLY PRODUCE SOME LOCALIZED
DIRECTIONAL WIND SHEAR BEFORE THE SHALLOW NEAR SURFACE COLD AIR
ERODES.

.BERING SEA/ALEUTIAN CHAIN...UPPER RIDGING WILL
A COUPLE OF WEAK LOWS AND FRONTAL TROUGHS WILL BRING SOME RAIN AND
SNOW TO THE ALEUTIANS AND BERING SEA THROUGH MIDWEEK.

.LONG TERM FORECAST...MODELS ARE INDICATING THAT THE UPPER RIDGE WILL
REMAIN STRONG OVER THE MAINLAND THROUGH THE END OF THE WEEK...BUT
MODELS DIVERGE FOR NEXT WEEKEND. THERE WILL BE SOME CHANCES FOR
PRECIPITATION ESPECIALLY WEST OF THE COOK INLET REGION FOR THE
WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNINGS (ENDING) 131 AND 135.
MARINE...GALE 150 155 178
FIRE WEATHER...NONE.

RMC DEC 13