Small Craft Advisory 946, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKST WED NOV 27 2013

.ANALYSIS AND UPPER LEVELS...
A WEAKENING ELONGATED UPPER TROUGH STRETCHES FROM THE NORTHERN GULF
SOUTHEASTWARD THROUGH THE PANHANDLE. LIFT FROM THE AFOREMENTIONED
FEATURE IS PRODUCING LIGHT SNOW IN THE COPPER RIVER BASIN WITH LIGHT
RAIN ALONG THE NORTH GULF COAST. A CLOSED UPPER LOW IS DRIFTING INTO
NORTHWESTERN ALASKA WITH A STRONG NEGATIVELY TILTED SHORTWAVE PUSHING
ACROSS THE ALASKA RANGE. COLD AIR OVER THE SOUTHWEST INTERIOR IS
BEGINNING TO SPILL THROUGH THE GAPS INTO THE SOUTHCENTRAL AS
EVIDENCED BY INCREASING RADAR RETURNS NEAR THE MOUNTAINS...THOUGH
MOST OF THE SNOW FROM THE WESTERN KENAI PENINSULA THROUGH THE MAT-SU
IS BELOW THE RADAR BEAM. A RIDGE OF HIGH PRESSURE IS NOSING INTO THE
BERING SEA WHILE A STRONG CLOSED LOW OVER THE NORTHERN PACIFIC IS
FORMING A REX BLOCK OUT WEST.

.MODEL DISCUSSION...
SYNOPTICALLY GUIDANCE IS SHOWING A SIMILAR PATTERN THROUGH THE
BEGINNING OF THE WEEKEND. THE REX BLOCK OVER THE BERING/NORTH PACIFIC
WILL ACT TO SLOW THE PATTERN AND AMPLIFY THE JET AND UPPER LEVEL
PATTERN OVER THE WESTERN BERING SEA/KAMCHATKA WHILE THE UPPER LOW
ENTERING THE STATE TODAY WILL SINK OVER THE SOUTHCENTRAL AND SLOWLY
PROGRESS EASTWARD WHILE ELONGATING FROM THE YUKON THROUGH THE
NORTHEASTERN GULF OF ALASKA. AS COLD AIR SETTLES IN BEHIND THE UPPER
TROUGH SINKING SOUTHWARD HIGH PRESSURE WILL BUILD IN THE INTERIOR AS
WEAK TROUGHING/LOW PRESSURE LINGERS ALONG THE NORTH GULF COAST. THE
ENHANCED PRESSURE GRADIENT WILL FAVOR AN OUTFLOW PATTERN AGAIN WITH
STRONG WINDS THROUGH FAVORED AREAS ALONG THE NORTH GULF COAST.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...LIGHT SNOW WILL CONTINUE EARLY THIS AFTERNOON.
AS THE AREA BECOMES MORE UNDER THE INFLUENCE OF THE SHORTWAVE
APPROACHING FROM THE WEST...SNOWFALL INTENSITY WILL INCREASE FROM THE
SUSITNA VALLEY THROUGH THE MATANUSKA VALLEY AND ANCHORAGE AS WELL AS
THE NORTHERN KENAI PENINSULA. THE HEAVIEST SNOWFALL WILL BE IN THE
LATE AFTERNOON...WINDING DOWN THROUGH EVENING HOURS. SNOW COULD
LINGER INTO THE OVERNIGHT HOURS...MAINLY ALONG THE MOUNTAINS AS THE
AREA REMAINS ENTRENCHED IN CYCLONIC FLOW AND COLD AIR CONTINUES TO
FILTER IN FROM THE NORTHWEST AND PUSH UP AGAINST THE TERRAIN. SNOW
WILL LINGER THE LONGEST IN THE COPPER RIVER BASIN BEFORE TAPERING
TOMORROW EVENING. STRONG GUSTY WINDS WILL CONTINUE TO INCREASE ALONG
THE WESTERN PRINCE WILLIAM SOUND AREA AS COLD AIR SPILLS THROUGH THE
GAPS BEFORE SPREADING ALONG THE NORTH GULF COAST TOMORROW INTO
FRIDAY.

SOUTHWEST ALASKA...RAPID DESTABILIZATION BEHIND THE COLD FRONT HAS
ALLOWED FOR SNOW SHOWERS TO PROPAGATE INTO THE KUSKOKWIM DELTA REGION
TODAY. AS WINDS PICK UP BEHIND THE FRONT LOW CLOUDS ALONG THE BRISTOL
BAY COAST WILL SCOUR OUT LATER THIS EVENING. A DISTURBANCE ENTERING
THE BACKSIDE OF THE UPPER LOW TOMORROW EVENING WILL SPREAD LIGHT SNOW
OVER THE KUSKOKWIM DELTA THURSDAY NIGHT INTO FRIDAY MORNING. WINDS
WILL REMAIN GUSTY ALONG THE COAST OF THE KUSKOKWIM DELTA WITH LIGHTER
WINDS FOR BRISTOL BAY AND THE KUSKOKWIM VALLEY.

BERING SEA AND ALEUTIANS...MOST OF THE BERING REMAINS BETWEEN WEATHER
SYSTEMS WITH A LARGE LOW OVER THE NORTHERN PACIFIC AND HIGH PRESSURE
OVER THE NORTHERN BERING. THE FORECAST WILL REMAIN MOSTLY DRY AS
NORTHEASTERLY WINDS OFF THE MAINLAND INCREASE TODAY AND TONIGHT. FOG
AND LOW STRATUS WILL BE THE MAIN CONCERNS UNDER THE HIGH PRESSURE
WHILE GUSTY NORTHEASTERLY WINDS WILL REMAIN THROUGH THE EARLY
WEEKEND.

.LONG TERM FORECAST...
GUIDANCE IN DECENT AGREEMENT WITH THE EVOLUTION OF THE PATTERN PAST
THE SHORT TERM. RATHER THAN COMPLETELY BREAK THE BLOCK IN THE BERING
SEA DOWN GUIDANCE SHIFTS THE CLOSED HIGH OVER THE MAINLAND AS A WEAK
DISORGANIZED LOW REMAINS IN THE NORTHERN PACIFIC. THE NET EFFECT
WOULD BE COLDER AND DRIER CONDITIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...STORM 130 131
         GALE 121 127 132 172 173 174 175 176
FIRE WEATHER...NONE

MTL NOV 13