Small Craft Advisory 717, NWS Anchorage, AK

AREA FORECAST DISCUSSION...CORRECTED
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT WED SEP 17 2008

.MODEL DISCUSSION...
THE MODELS ARE IN GOOD AGREEMENT THROUGH FRIDAY NIGHT WITH ONLY MINOR
DIFFERENCES IN THE NORTHERN GULF DURING THE LAST FEW PERIODS. THE
CONFLICT IN THE GULF OCCURS WITH THE LOCATION OF THE WEAKENING LOW
FRIDAY AND FRIDAY NIGHT. THE NAM AND ECWMF PLACE THE LOW OVER THE
COOK INLET WHILE THE GFS AND UKMET MOVE IT INTO THE NORTHERN GULF.

.ANALYSIS AND UPPER LEVELS...
A LOW PRESSURE SYSTEM WHICH BROUGHT A LOT OF RAIN TO SOUTHCENTRAL
ALASKA MOVED INTO THE COPPER RIVER BASIN AND IS RAPIDLY FILLING. A
RIDGE BEHIND THE LOW WILL RAPIDLY MOVE INTO THE GULF AS WELL AS THE
SOUTHCENTRAL REGION, CLEARING SOME OF THE CLOUDS THIS AFTERNOON AND
EVENING.

AN UPPER LEVEL LOW OVER THE ALASKA PENINSULA REMAINS VERTICALLY
STACKED WITH A MODERATE LOW REFLECTED AT THE SURFACE. THIS LOW IS
MOVING TOWARDS KODIAK ISLAND. A WEATHER FRONT EXTENDING
SOUTH OF THE LOW IS BEGINNING TO SHOW SIGNS OF STRENGTHENING AS A
SUBTROPICAL JET BEGINS TO TAKE CONTROL OF IT.

HIGH PRESSURE IS BUILDING OVER THE WESTERN BERING WHILE NORTH WINDS
PERSIST OVER THE EASTERN BERING.

.SHORT TERM FORECAST...
AN UPPER LEVEL LOW NEAR CHIGNIK WILL BECOME NEARLY STATIONARY OVER
KODIAK ISLAND LATE TONIGHT AND WILL SLOWLY WEAKEN THROUGH FRIDAY
AFTERNOON. AN UPPER LEVEL TROUGH OVER WESTERN ALASKA WILL PERSIST AND
GET A LITTLE STRONGER AS A CLOSED UPPER LEVEL LOW FORMS OVER THE
SEWARD PENINSULA FRIDAY. CLOUDS AND ISOLATED SHOWERS WILL REMAIN OVER
THE SOUTHWEST INTERIOR THROUGH FRIDAY.

A MODERATE LOW SOUTH OF THE ALASKA PENINSULA WILL CONTINUE TO
STRENGTHEN AS IT MOVES NORTHEAST AND STALL OVER KODIAK ISLAND
TONIGHT. THE LOW WILL SLOWLY WEAKEN AS IT DRIFTS INTO THE LOWER COOK
INLET THROUGH FRIDAY AFTERNOON. A 300 MB SOUTHERLY JET WILL MOVE
INTO THE WESTERN GULF AND HELP INCREASE THE PRESSURE GRADIENT AHEAD
OF THE WEATHER FRONT TONIGHT AND INTO THURSDAY. LOCALLY STRONG WINDS
WILL BEGIN ON THE WEST SIDE OF CHANNELED TERRAIN OVER THE KENAI
PENINSULA, ANCHORAGE BOWL AND CHUGACH MOUNTAINS TONIGHT AND CONTINUE
UNTIL THE FRONT MOVES THROUGH. AREAS OF HEAVY RAIN WILL MOVE INTO THE
PRINCE WILLIAM SOUND TONIGHT AND THURSDAY AND WILL BECOME SHOWERS
THURSDAY NIGHT AND FRIDAY.

A RIDGE OVER THE WESTERN GULF WILL MOVE EAST AND WEAKEN AS A WEAK
SURFACE TROUGH MOVES INTO THE CENTRAL BERING FRIDAY.

.LONG TERM FORECAST...
AN UPPER LEVEL LOW NEAR SEWARD WILL MOVE NORTHWARD TOWARDS BARROW BY
SUNDAY. A TROUGH EXTENDING SOUTH OF THE LOW WILL SWING NORTH AND
THROUGH EASTERN ALASKA INTO THE WEEKEND AND WILL LIE ALONG THE
NORTHERN ALAKSA COAST AND NORTHWEST CANADA SUNDAY. CLOUDS AND SHOWERS
WILL REMAIN OVER MOST OF SOUTHERN MAINLAND THROUGH THE WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING FOR THE TURNAGAIN ARM, HILLSIDE AND
PORTAGE VALLEY LATE TONIGHT THROUGH THURSDAY EVENING.
MARINE...GALES 120, 125, 130, 132, 138, 140, 150, 155
FIRE WEATHER...NONE.

NM SEP 08