Small Craft Advisory 804, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT MON OCT 14 2013

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL PLANETARY TROUGH EXTENDS FROM EASTERN RUSSIA TO THE
CANADIAN ROCKIES THIS MORNING WITH SMALLER SCALE TROUGHS OVER THE
WESTERN BERING AND THE CENTRAL GULF OF ALASKA. A CUT-OFF UPPER LOW IS
OVER THE WESTERN BERING. RIDGES ARE WEST OF KAMCHATKA AND OVER THE
CANADIAN ROCKIES WITH A SMALLER RIDGE OVER THE EASTERN BERING. AT THE
SURFACE...A DEEP LOW IS NEAR ATTU WITH AN OCCLUDED FRONT EXTENDING
ACROSS THE NORTHERN BERING TO THE EASTERN ALEUTIANS. A SMALL TROUGH
OF LOW PRESSURE IS DISSIPATING OVER THE NORTHWEST GULF WITH
ASSOCIATED RAIN AND SHOWERS STREAMING INTO SOUTHCENTRAL AND PRINCE
WILLIAM SOUND.

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT.

THE RESIDUAL TROUGH OVER THE NORTHWEST GULF WILL DISSIPATE LATER
TODAY...WITH SHOWERS ON ITS LEADING EDGE OVER SOUTH CENTRAL AND
PRINCE WILLIAM SOUND SLOWLY TAPERING OFF. THE DISSIPATION OF THIS
TROUGH WILL CREATE AN UNINTERRUPTED UPPER FLOW FROM WELL SOUTH OF THE
CENTRAL ALEUTIANS TO THE ALCAN. A STRONG JET WILL CAUSE RAPID
NORTHEAST PROGRESSION OF WEATHER SYSTEMS OVER THE AREA FROM THE AKPEN
EAST TUE THROUGH THU.

IN THE MEANTIME...THE ATTU LOW WILL MOVE TO THE EASTERN BERING BY TUE
MORNING AND THEN DRIFT SLOWLY NORTH THROUGH THU. THE ASSOCIATED FRONT
WILL REACH SOUTHWEST AK THIS AFTERNOON AND LOSE INTEGRITY AS IT
CROSSES THE AK AND ALEUTIAN RANGES ON TUE. IT WILL STILL CREATE A
TIGHT PRESSURE GRADIENT OVER SOUTHCENTRAL ON TUE.

A KAMCHATKA LOW AND FRONT WILL ENTER THE WESTERN ALEUTIANS TUE AND
WEAKEN ON WED AS THE LOW CROSSES THE CENTRAL ALEUTIANS ON ITS WAY TO
THE NORTH PACIFIC. AT THE SAME TIME IT WILL PASS A WAVE MOVING
RAPIDLY NORTH TO THE AKPEN...WHICH WILL REACH SOUTHWEST AK ON THU.

FINALLY...THE WEAKENING REMNANTS OF A TYPHOON WILL BEGIN TO AFFECT
THE WESTERN ALEUTIANS ON THU.

THE FORECAST UTILIZES THE GFS AND NAM IN THE SHORT TERM AND THEN
TRANSITIONS TO THE EC AND WPC GUIDANCE FOR MID AND LONG RANGE.

.SHORT TERM FORECAST...

IN THE WEST...RAIN AND GALES WILL SPREAD ACROSS THE REGION THROUGH
WED AS FIRST THE ATTU LOW AND THEN THE KAMCHATKA LOW AFFECT THE AREA.
A BRIEF BREAK IS EXPECTED THU AND THEN MORE RAIN AND GALES WILL
ACCOMPANY THE TYPHOON REMNANTS BEGINNING THU NIGHT.

FOR SOUTHWEST AK...RAIN AND SHOWERS WILL AFFECT THE AREA AS THE FRONT
FROM THE ATTU LOW MOVES INLAND TODAY AND IS IMMEDIATELY FOLLOWED BY A
WAVE MOVING AROUND THE ATTU LOW...WHICH BY THIS TIME IS OVER THE
EASTERN BERING...TUE INTO WED. THIS IS THEN FOLLOWED BY WIND AND RAIN
AS THE NORTH PACIFIC LOW RACES NORTH ON THU.

SOUTH AND EAST OF THE AK RANGE...EXPECT PERIODS OF RAIN AND SHOWERS
INTO FRI AS FIRST THE NORTHWEST GULF TROUGH DISSIPATES TODAY...THE
ATTU FRONT WEAKENS OVERHEAD ON TUE...WHICH WITH ITS TIGHTENING OF THE
PRESSURE GRADIENT ACROSS SOUTH CENTRAL WILL SET UP VERY STRONG WINDS
THROUGH CHANNELED TERRAIN...THE WAVE MOVING AROUND THE ATTU LOW
ARRIVES TUE NIGHT INTO WED...AND THE NORTH PACIFIC LOW MOVES ACROSS
THE AKPEN ON THU.

.LONG TERM FORECAST...

THE TYPHOON REMNANTS WILL SPREAD RAIN AND WIND ACROSS THE ENTIRE
FORECAST AREA THROUGH THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALES 120 130 131  132 136 138 150 155 165 170 172 175 176
177 178 185
FIRE WEATHER...NONE

DS OCT 13