Small Craft Advisory 655, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT WED AUG 28 2013

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER SOUTHWEST ALASKA PHASING WITH A
SHORT-WAVE TROUGH NEAR KODIAK ISLAND. THIS IS SPINNING UP A FAIRLY
STRONG SYSTEM OVER SOUTHERN ALASKA. THERE IS AN UPPER LEVEL RIDGE
BUILDING INTO THE BERING SEA AHEAD OF A STRONG UPPER LOW CENTERED
OVER THE SOUTHERN TIP OF THE KAMCHATKA PENINSULA. A DEEP UPPER LOW
(519 DM AT 500 MB) IS OVER THE CHUKCHI SEA.

.MODEL DISCUSSION...
FORECAST GUIDANCE IS IN PRETTY GOOD AGREEMENT. THERE ARE SOME
DIFFERENCES ON THE LOCATION OF A LOW IN THE GULF WEDNESDAY AFTERNOON
THROUGH WEDNESDAY NIGHT. THE GFS AND NAM ARE TAKING A NORTHERLY TRACK
WHILE THE ECMWF...UKMET...GEM ARE CLUSTERED IN A MORE SOUTHERLY
POSITION. THE AFTERNOON FORECASTS ARE GENERALLY A BLEND OF THE TWO
SOLUTIONS.

.SHORT TERM FORECAST...
THE PHASING LOW WILL BRING WIDESPREAD PRECIPITATION TO MUCH OF SOUTH
CENTRAL ALASKA TONIGHT AND THURSDAY AS WELL AS THE EASTERN PORTION
OF SOUTHWEST ALASKA NEAR THE ALASKA/ALEUTIAN RANGES. THE SURFACE LOW
WITH THIS SYSTEM WILL MOVE TO JUST SOUTHEAST OF KODIAK ISLAND LATE
TONIGHT AND THEN DROP SOUTH ON THURSDAY. THIS SYSTEM NEVER BECOMES
VERTICALLY STACKED AS THE UPPER LOW RAPIDLY SLIDES SOUTH. THE UPPER
LOW WILL BE NORTHWEST OF THE SURFACE LOW THIS EVENING...WEST OF IT
LATE TONIGHT AND THEN SOUTH OF IT THURSDAY AFTERNOON. PRECIPITATION
WILL DIMINISH TO SCATTERED SHOWERS THURSDAY NIGHT AS THE LOW MOVES
WELL SOUTH OF THE AREA BY LATE THURSDAY NIGHT.

ON THURSDAY THE UPPER RIDGE OVER THE BERING SEA WILL BE PUSHED INTO
THE EASTERN BERING SEA AND INTO SOUTHWEST ALASKA THURSDAY NIGHT.
THIS IS IN RESPONSE TO THE KAMCHATKA LOW MOVING EAST AND SPREADING
A FRONTAL SYSTEM ACROSS THE BERING SEA AND ALEUTIANS. THIS SYSTEM
WILL REACH THE WEST COAST OF ALASKA FRIDAY NIGHT AND INTO SOUTHWEST
ALASKA ON SATURDAY...PUSHING THE RIDGE EAST AND SLOWLY FLATTENING
IT. THE CHUKCHI SEA LOW WILL DIVE SOUTH TO THE NORTHWEST COAST OF
ALASKA EARLY FRIDAY AND THEN EAST ACROSS NORTHERN ALASKA FRIDAY NIGHT
AND SATURDAY. THIS WILL PUT SOUTHERN ALASKA INTO FAST WESTERLY FLOW
ALOFT BY SATURDAY...AND COMPLETELY SQUASH THE RIDGE INTO THE
NORTHEAST PACIFIC.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 120 125 130 132 138 150 155 176.
FIRE WEATHER...NONE.

LUDWIG AUG 13