Small Craft Advisory 870, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST SAT DEC 1 2012

.ANALYSIS AND UPPER LEVELS...
THE GENERAL UPPER LEVEL PATTERN REMAINS THE SAME THIS AFTERNOON WITH
A RIDGE CENTERED JUST SOUTH OF THE ALEUTIAN CHAIN EXTENDING NORTHWARD
OVER THE BERING SEA AND A TROUGH EXTENDING FROM THE YUKON TERRITORY
INTO THE FAR NORTHEASTERN PACIFIC. BROAD NORTHERLY FLOW BETWEEN THESE
TWO FEATURES CONTINUES TO PROMOTE COLD AND DRY CONDITIONS OVER MUCH
OF SOUTHERN ALASKA...WHILE A WEAK DISTURBANCE MOVING DOWN THE EASTERN
PERIPHERY OF THE RIDGE IS SPREADING CLOUDS AND A FEW SNOW SHOWERS
OVER THE KUSKOKWIM DELTA AND EASTERN BERING.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH THE SHORT TERM IN HANDLING THE
OVERALL SYNOPTIC FEATURES. THE RIDGE OVER THE BERING WILL BEGIN TO
BREAK DOWN BUT REMAIN IN PLACE THROUGH MONDAY AS AN UPPER LOW
ENCROACHES UPON IT FROM THE WEST. MEANWHILE...THIS WILL ALLOW THE
UPPER LOW OVER THE YUKON TERRITORY TO SLIDE SOUTHWARD ACROSS
SOUTHCENTRAL AK AND INTO THE GULF BY MONDAY AFTERNOON AS A 120 KT
UPPER LEVEL JET DIGS ALONG ITS WESTERN PERIPHERY.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
COLD AND DRY CONDITIONS WILL PREVAIL INTO THE EARLY PART OF THE WEEK
AS OFFSHORE FLOW CONTINUES. STRONG OUTFLOW WINDS WILL CONTINUE
THROUGH FAVORED GAPS IN THE TERRAIN ALONG THE NORTHERN GULF COAST.
WINDS WILL BE REINFORCED SUNDAY INTO MONDAY AS LOW PRESSURE MOVES
BACK INTO THE GULF AND COLD AIR ADVECTION COMMENCES OVER SOUTHCENTRAL
AK. THE COMBINATION OF STRONG WINDS AND LOW RELATIVE HUMIDITY WILL
CONTINUE TO SUPPORT RED FLAG CONDITIONS IN THE MATANUSKA VALLEY
THROUGH SUNDAY AFTERNOON.

SOUTHWEST ALASKA...
ISOLATED SNOW SHOWERS OVER THE KUSKOKWIM DELTA AND LOWER KUSKOKWIM
VALLEY WILL TAPER OFF BY SUNDAY MORNING AS THE UPPER LEVEL
DISTURBANCE MOVES SOUTH OF THE AREA...YIELDING CLEAR SKIES OVER THE
SOUTHWEST MAINLAND INTO THE EARLY PART OF THE WEEK. THE DISTURBANCE
WILL BRING SNOW TO THE AKPEN TONIGHT INTO SUNDAY MORNING AS IT MOVES
OVERHEAD. ADDITIONALLY...STRONG WINDS THROUGH CHANNELED TERRAIN WILL
PERSIST THROUGH MONDAY AS NORTHERLY FLOW CONTINUES.

ALEUTIANS/BERING SEA...
RELATIVELY BENIGN CONDITIONS WILL CONTINUE ACROSS THE BERING THROUGH
MONDAY AS HIGH PRESSURE REMAINS IN CONTROL. A WEAK FRONT WILL BRING
RAIN TO THE WESTERN ALEUTIANS ON SUNDAY NIGHT AND THEN CONTINUE TO
DISSIPATE AS IT MOVES TOWARD THE CENTRAL PART OF THE CHAIN ON MONDAY.

.LONG TERM FORECAST...
MODELS INDICATE THE RIDGE OVER THE BERING WILL BREAK DOWN BY MID
WEEK...ALLOWING A BROAD UPPER LEVEL TROUGH TO BECOME ESTABLISHED OVER
SOUTHCENTRAL ALASKA. THIS WILL BRING THE POSSIBILITY OF PRECIPITATION
RETURNING TO THE FORECAST MID TO LATE NEXT WEEK...MAINLY ALONG THE
GULF COAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE WARNING 121 126 130 132 150 155
         HEAVY FREEZING SPRAY WARNING 121 126 127 129 130 140 141
                                      150 160
FIRE WEATHER...RED FLAG WARNING 111

CB DEC 12