Small Craft Advisory 952, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
541 AM AKST SUN NOV 30 2014

.ANALYSIS AND UPPER LEVELS...

NEGATIVE TILT LONGWAVE TROUGH RESIDES FROM NORTHERN KAMCHATKA
RUSSIA SOUTH AND EAST ACROSS ATTU AND INTO THE NORTH PACIFIC TO
THE SOUTH OF THE WESTERN AND CENTRAL ALEUTIAN CHAIN THIS MORNING.
A 982 MB SURFACE LOW RESIDES NEAR 180 LONGITUDE 320 NM SOUTH OF
AMCHITKA...WITH THE PARENT LOW OVER THE WEST-CENTRAL BERING SEA
LOOPING TO THE NORTH AND WEST. A WARM FRONT ATTACHED TO THIS LOW
IS PUSHING ACROSS THE NORTHERN AND EASTERN BERING SEA HEADED
TOWARD THE SOUTHWEST MAINLAND.

OVER THE MAINLAND...A STRONG UPPER LEVEL RIDGE PERSISTS FROM THE
SOUTHERN ALASKA PENINSULA NORTH TO THE COASTLINE OF THE Y-K DELTA.
NUMEROUS SHORTWAVE DISTURBANCES CAN BE SEEN MOVING NORTH AND EAST
AND OVER THE RIDGE AXIS TOWARD SOUTHCENTRAL ALASKA.

OVER SOUTHCENTRAL...A STRONG NORTHWESTERLY JET STREAK PERSISTS
ALOFT WITH AN EMBEDDED DISTURBANCE OVER NORTHERN AND EASTERN
PRINCE WILLIAM SOUND MOVING EAST. STRONG SUBSIDENCE BEHIND THIS
FEATURE IS RESULTING IN PATCHY FOG OVER THE COOK INLET
REGION...ESPECIALLY NEAR PALMER AND ANCHORAGE BUT ALSO EXTENDING
SOUTH AND EAST TO NEAR CORDOVA.

&&

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT SYNOPTICALLY IN BRINGING THE LOW
SOUTH OF AMCHITKA NORTH AND EAST TO NEAR THE PRIBILOFS MONDAY
WHILE ABSORBING THE LOOPING LOW OVER THE WESTERN BERING. THIS WILL
ALLOW FOR A LARGE AND WELL-DEFINED DOUBLE-BARRELED CIRCULATION TO
FORM OVER THE BERING SEA AND EXTENDING TOWARD KODIAK ISLAND BY
TUESDAY. THIS WILL OF COURSE CAUSE THE CURRENT RIDGE MOVING OVER
THE SOUTHWEST MAINLAND TODAY TO WEAKEN AND PROGRESS ACROSS
SOUTHCENTRAL TUESDAY INTO MID-WEEK...WHILE THE WELL-DEFINED AND
VIGOROUS UPPER LEVEL LOW MOVES EAST TOWARD THE WESTERN GULF MID-
WEEK.

A STRONG PUSH OF WARM MOIST AIR WILL BE MOVING OVER THE
RIDGE TODAY THROUGH MONDAY AND TUESDAY...RESULTING IN SIGNIFICANT
OVERRUNNING IN THE LOWER LEVELS OF THE ATMOSPHERE. THE EXTENT OF
OVERRUNNING PRECIPITATION INTO SOUTHCENTRAL LATE SUNDAY NIGHT
THROUGH MONDAY WILL BE DEPENDENT IN PART ON THE LOCATION AND
STRENGTH OF WEAK SHORTWAVE DISTURBANCES...WHICH AT THIS POINT IN
TIME IS TOO DIFFICULT TO PINPOINT PAST TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

THE DIFFICULT PART OF TODAY'S FORECAST IS FIGURING OUT THE EXTENT
AND MAGNITUDE OF FOG...AND IF IT DOES PERSIST...HOW LONG DOES IT
LAST INTO THE AFTERNOON. CURRENTLY...THE THINKING IS THAT THERE
WILL BE SOME PATCHY FOG WHICH MAY LINGER WELL INTO THE EARLY
AFTERNOON GIVEN THE POOR SUN ANGLE AND STRONG SUBSIDENCE
ALOFT ALONG WITH THE FRESH SNOW PACK PROVIDING LOW-LEVEL
MOISTURE...ESPECIALLY IN SHELTERED AREAS FROM VERY WEAK NORTHERLY
COLD ADVECTION JUST ABOVE THE SURFACE.

FOG MAY REDEVELOP FOR A TIME TONIGHT AS WARM ADVECTION IN THE
LOW-LEVELS BEGINS TO MOVE TOWARD THE AREA AND HELP FORM AN
INVERSION. THE NAM AND GEM-REG MODELS ARE PICKING UP ON A WEAK AND
(CURRENTLY) ALMOST INDISCERNIBLE SHORTWAVE SOUTH OF THE ALEUTIANS
THAT WILL QUICKLY MOVE NORTH AND EAST OVER THE RIDGE AXIS AND
TOWARD SOUTHCENTRAL LATE TONIGHT INTO MONDAY. MODELS SUGGEST SOME
LIGHT OVERRUNNING SNOW DEVELOPING AS THIS DISTURBANCE APPROACHES
THE COOK INLET REGION MONDAY MORNING INTO MONDAY AFTERNOON. FOR
NOW...WILL GO WITH CHANCE WORDING IN THE FORECAST AND LET THE DAY
SHIFT HOPEFULLY GET A BETTER HANDLE WITH THE POTENTIAL WITH THIS
SYSTEM.

OTHERWISE...THE TUESDAY AND WEDNESDAY PERIODS LOOK TO BE MORE OF
THE SAME...WITH A WEATHER FRONT APPROACHING FROM THE SOUTH AND
WEST BRINGING ANOTHER ROUND OF LIGHT SNOW TO THE REGION.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE WARM FRONT STALLED ALONG THE WESTERN COAST IS THE FOCUS FOR
SNOW DEVELOPING THIS MORNING AS TEMPERATURES ARE IN THE MID TO
UPPER 20S. A WEAK SHORTWAVE WILL SPREAD SNOW INLAND THROUGH THE
AFTERNOON WITH A MUCH STRONGER WAVE APPROACHING THIS EVENING. THE
SUBTROPICAL AIR MASS OVER THE BERING PUSHES INTO THE SOUTHWEST
OVERNIGHT BRINGING HIGHER PRECIPITATION AMOUNTS OVERNIGHT AND
MIXED PRECIPITATION OF SNOW...FREEZING RAIN AND RAIN.
TEMPERATURES WILL WARM ABOVE FREEZING ACROSS THE SOUTHWEST EARLY
MONDAY ENDING THE WINTRY MIX. PRECIPITATION TAPERS OFF BRIEFLY ON
MONDAY AS THE BERING LOW SHIFTS EAST MONDAY NIGHT BRINGING RAIN TO
BRISTOL BAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A NORTH PACIFIC STACKED LOW IS MOVING TOWARD THE CENTRAL
ALEUTIANS THIS MORNING WITH A REINFORCING SURGE OF MOISTURE BRINGING
RAIN AND GUSTY WINDS TO THE CENTRAL AND EASTERN ALEUTIANS. STRONG GUSTY
WINDS WILL CONTINUE TO IMPACT THE ALEUTIAN CHAIN THROUGH TUESDAY
MORNING WITH SOUTHEASTERLY FLOW BECOMING WEST TO NORTHWEST BEHIND
THE SYSTEM AS IT SHIFTS EAST MONDAY NIGHT. COLD AIR ADVECTION
ACROSS THE WESTERN BERING/ALEUTIANS WILL BRING A MIX OF RAIN AND
SNOW MONDAY NIGHT WITH STORM FORCE WINDS ACROSS THE WESTERN
BERING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

THE MODELS ARE STARTING TO COME INTO BETTER AGREEMENT MID WEEK AS
AN UPPER TROUGH DESCENDS INTO THE BERING SEA FROM THE ARCTIC
OCEAN AND INTERACTS WITH A BERING TROUGH MOVING INTO THE NORTH
PACIFIC.

BEYOND WEDNESDAY...FORECAST CONFIDENCE THEN QUICKLY DIMINISHES
WITH HOW FAR SOUTH THE ARCTIC TROUGH WILL DIVE INTO THE BERING AND
THIS TROUGH BECOMES NEARLY STATIONARY. FOR THIS REASON WPC WAS
USED HEAVILY FOR THE FORECAST LATE THIS WEEK. CONFIDENCE IS AT ITS
LOWEST WITH THE TRACK OF A POSSIBLE LOW NEAR THE GULF LATE IN THE
WEEK. OUT WEST...THERE IS DECENT AGREEMENT THAT A SERIES OF LOWS
WILL DEVELOP OVER THE BERING MID-LATE NEXT WEEK...BUT WITH LOW
CONFIDENCE AS TO WHERE THESE MAY FORM.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FREEZING RAIN ADVISORY 152 155
		 WINTER WEATHER ADVISORY 161
MARINE...STORM WARNING 176 178
		 GALE WARNING 150 155 165 170 172 173 174 175 177 179
					  180 181 185
FIRE WEATHER...NONE

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...DEK