Small Craft Advisory 883, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SAT NOV 9 2013

.MODEL DISCUSSION...
MODEL SYNOPTIC FIELDS OVERALL ARE IN GOOD AGREEMENT. DIFFERENCES
ARISE WITH THE SPEED OF THE COLD FRONT MOVING ACROSS SOUTHCENTRAL
ALASKA AND THE POSITION OF THE FRONTAL WAVE NEAR THE KENAI PENINSULA.
THE NAM CONTINUES TO BE THE MOST PROGRESSIVE WITH THE MOVEMENT OF THE
COLD AIR THROUGH THE ANCHORAGE BOWL/COOK INLET REGION SUN AFTERNOON.
THE GFS TENDS TO HOLD THE WARM AIR ACROSS THE AREA UNTIL EARLY SUN
EVENING. THE ECMWF WHICH MAY BE MORE REASONABLE IS BETWEEN THE TWO.
THE GFS/NAM ALSO TEND TO SHUT OFF THE SNOW ACROSS THE ANCHORAGE BOWL
AND EASTERN KENAI RATHER QUICKLY SUN NIGHT THOUGH THE 500 MB TROUGH
STILL IS WEST OF THE AREA. THINKING THAT THE BRUNT OF THE SNOW SHOULD
BE TAPERING OFF EARLY MON MORNING AS THE COOK INLET/ANCHORAGE BOWL
ARE WELL INTO THE COLD AIR AND THE UPPER JET SUPPORT SHIFTS EAST.
THERE MOST LIKELY WILL BE SNOW SHOWERS AROUND UNTIL THE UPPER TROUGH
PASSAGE MON AFTERNOON/EVENING.

.UPPER LEVELS...
,500 MB...THE LONG WAVE OVER THE EASTERN BERING SEA SHARPENS AS IT
MOVES EAST AND EXTENDS SOUTH ACROSS SOUTHCENTRAL ALASKA (MATSU/KENAI)
MON AFTERNOON...THEN MOVES TO WESTERN CANADA TUE AFTERNOON. A HIGH
AMPLITUDE RIDGE BUILDS OVER THE CENTRAL BERING SEA SUN AND THE
EASTERN BERING SEA/WESTERN ALASKA MON AND TUE.

...SHORT TERM...
SOUTHCENTRAL ALASKA...
PERIODS OF LIGHT SNOW AND RAINW ARE EVIDENT ACROSS THE KENAI
PEN...WITH SNOW AND POCKETS OF FREEZING DRIZZLE OVER THE ANCHORAGE
BOWL AND MATANUSKA VALLEY. WARMING IS A LITTLE SLOW TO PROGRESS
NORTH. THE NAM THICKNESS FIELDS HAVE A GOOD HANDLE ON THIS AND SLOWLY
BRINGS TEMPS ABOVE FREEZING ACROSS THE ANCHORAGE BOWL AND PORTIONS OF
THE MATANUSKA VALLEY TONIGHT. LOWER ELEVATIONS IN THE MATANUSKA
VALLEY WILL LIKELY START AS SNOW THIS EVENING THEN SHOULD BECOME
MIXED AND EVENTUALLY CHANGE OVER TO RAIN...HIGHER ELEVATIONS WILL
LIKELY HOLD ON TO THE SNOW THROUGH TONIGHT. RAIN WILL LIKELY BE HEAVY
AT TIMES ACROSS THE THE KENAI/ANCHORAGE BOWL TONIGHT AND INTO EARLY
SUN AFTERNOON. RAINFALL WILL CAUSE WATER LEVELS TO RISE ON SMALL
STREAMS IN THE ANCHORAGE BOWL WHICH WILL CREATE SOME MINOR FLOOD
ISSUES SUN. SNOW WILL INCREASE OVER THE SUSITNA VALLEY THROUGH
TONIGHT AND CREATE ADVISORY LEVEL ACCUMULATIONS. COLD AIR STARTS TO
MOVE ACROSS THE WESTERN END OF SOUTHCENTRAL SUN AFTERNOON WITH THE
COLD FRONT. PLACES HAVING RAIN SHOULD SHIFT TO SNOW AT THAT POINT AND
CONTINUE THROUGH THE EARLY MORNING HOURS MON...THEN SHIFT TO SNOW
SHOWERS ON SUN UNTIL UPPER TROUGH  PASSAGE. THE 850 MB FLOW SHIFTS
AROUND TO THE SE OVER THE COPPER RIVER BASIN ON SUN EVENING AND THE
SNOW SHOULD INCREASE IN INTENSITY WITH ADVISORY LEVEL ACCUMULATIONS
THROUGH MON AFTERNOON.

SOUTHWEST...THE COLD FRONT MOVES ACROSS THE DELTA EARLY THIS EVENING
AND THE EASTERN BRISTOL BAY EARLY SUN MORNING. RAIN SHOULD SHIFT TO
SNOW SHOWERS WITH PASSAGE. COLD AIR WILL SETTLE INTO THE AREA THROUGH
MONDAY BEFORE ANOTHER WARM FRONT APPROACHES MIDWEEK.

BERING SEA AND ALEUTIAN ISLANDS...GUSTY WINDS WILL ALSO BE SEEN
THROUGHOUT THE DAY IN ASSOCIATION WITH THE PRESSURE GRADIENT WITH A
LOW LOCATED OVER THE NORTHERN BERING SEA. THE WINDS SHOULD DIMINISH
THIS EVENING AS THE LOW PUSHES TOWARD THE BERING STRAIT. COLD AIR
WILL RESIDE OVER THE BERING SEA AND THE ALEUTIAN ISLANDS THROUGH THE
MAJORITY OF SUNDAY WITH SCATTERED RAIN AND SNOW SHOWERS OBSERVED
ACROSS THE BERING SEA. ON SUNDAY...A RIDGE OF HIGH PRESSURE BUILDS IN
FROM THE SUBTROPICS AND BRINGS WARMER AIR BACK TO THE REGION.

.LONG TERM FORECAST...

AN OMEGA BLOCKING PATTERN THAT WILL BRING ABOVE AVERAGE TEMPERATURES
TO MUCH OF ALASKA WILL BE BREAKING DOWN AT THE BEGINNING OF THE LONG
TERM FORECAST. A RIDGE OF HIGH PRESSURE OVER THE BERING SEA WILL
BEGIN TO BREAK DOWN AND ALLOW A SERIES OF WEAK DISTURBANCES ALOFT TO
PUSH ACROSS THE LONG-WAVE PATTERN. THESE DISTURBANCES WILL ENHANCE AN
UPPER LEVEL TROUGH...LEAD TO COLD AIR DROPPING DOWN FROM THE ARCTIC
AND BRINGING COOLER TEMPERATURES BACK TO THE REGION ON SATURDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 170 172 173 174 175 176 177 178 179 181 185.
FIRE WEATHER...NONE.

RMC NOV 13