Small Craft Advisory 483, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
505 AM AKDT THU JUL 12 2012

.ANALYSIS AND UPPER LEVELS...
AN UPPER-LVL RIDGE AXIS EXTENDS FROM THE AK PANHANDLE UP ALONG THE
ALCAN BORDER INTO NORTHEASTERN AK. A STACKED UPPER-LVL LOW IS
CENTERED JUST SOUTH OF NUNIVAK ISLAND AND IS DRIFTING SLIGHTLY TO THE
WEST...WITH PERIPHERAL PRECIPITATION CONTINUING OVER SOUTHWEST AK. AN
80 KT JET MAX HAS ROUNDED THE BASE OF THE UPPER LOW AND IS OVER THE
LOWER KUSKOKWIM VALLEY AND INTERIOR BRISTOL BAY. SOME SPEED
DIVERGENCE ALOFT BETWEEN THE JET AND SOUTHCENTRAL AK IS FACILITATING
SOME LIGHT RAIN OVER TYPICALLY DOWNSLOPED AREAS IMMEDIATELY NORTHWEST
OF THE CHUGACH/KENAI RANGES. AT THE SURFACE A FRONT IS DRAPED OVER
THE NORTHERN GULF OF AK AND IS STALLING OUT AND WEAKENING...THOUGH IT
STILL SUPPORTS GUSTY GAP WINDS THROUGH TURNAGAIN ARM/PORTAGE VALLEY
AND SOME LINGERING GALES OVER THE NORTHERN GULF. STEADY RAIN PERSISTS
IN THE GENEROUS ONSHORE OVER THE SOUTHERN TO EASTERN KENAI PENINSULA
AND PRINCE WILLIAM SOUND. A WEAK WAVE OF LOW PRESSURE IS DEVELOPING
AROUND 60 MILES EAST OF SITKINAK ROTATING NORTH...BRINGING KODIAK
ISLAND A REINFORCING SHOT OF RAIN. BENIGN WEATHER EXISTS OVER MUCH OF
THE BERING SEA/ALEUTIAN REGION WITH TYPICAL FOG/STRATUS. ALSO OF NOTE
IS A DEVELOPING PACIFIC LOW AROUND 500 MILES SOUTH OF KISKA MOVING
EAST.

.MODEL DISCUSSION...
MODELS REASONABLY CAPTURE THE MAIN FEATURES AND PATTERN IN GENERAL.
THE FRONT IN THE GULF IS DEPICTED WEAKENING IN PLACE THROUGH
TODAY...WHILE THE LOW NEAR KODIAK ISLAND IS SHOWN WEAKENING AND
DISSIPATING AROUND 90 MILES NORTHEAST OF KODIAK CITY ON FRI. A
SUPPORTING SHORTWAVE PUSHES ONSHORE THE SOUTHERN MAINLAND THIS
EVENING AND SLIPS NORTH OF THE COPPER BASIN AND SUSITNA VALLEY ON
FRI. IN IT'S WAKE...WEAK HIGH PRESSURE IS DEPICTED BUILDING OVER THE
GULF FRI NIGHT AND EARLY SAT BEFORE PERIPHERAL MOISTURE FROM THE
PACIFIC LOW WORKS UP FOR THE LATTER PART OF THE WEEKEND.

FURTHER WEST...MODELS SHOW THE UPPER-LOW WILL DRIFT TO AROUND 40
MILES NORTH OF THE PRIBILOF ISLANDS ON SAT MORNING. THE PACIFIC LOW
SOUTH OF KISKA TRACKS TO AROUND 200 MILES SOUTH OF DUTCH HARBOR ON
SAT MORNING...THEN TO NEAR CAPE NEWENHAM ON SUN MORNING. THERE IS
GOOD AGREEMENT WITH THE GFS AND ECWMF ON THIS DEVELOPMENT...THOUGH
THE NAM TENDS TO TRACK THE BULK OF THE ENERGY SOUTH OF THE AK
PENINSULA TO NEAR THE SOUTHERN MOUTH OF SHELIKOF STRAIT AT THE
AFOREMENTIONED SUN TIME-FRAME. HAVE GENERALLY KEPT THE MORNING
FORECAST PACKAGE LEANING ON THE GFS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
ALONG COASTAL AREAS...STEADY RAIN LOOKS TO BEGIN TAPERING TO LIGHT
PASSING SHOWERS FROM SOUTHWEST TO NORTHEAST THROUGH FRI AS THE FRONT
DISSIPATES AND ONSHORE FLOW WEAKENS. THE STRONGEST WINDS ALSO LOOK TO
DIMINISH. NORTH AND WEST OF THE CHUGACH/KENAI RANGES...DYNAMIC
SUPPORT FOR LIGHT RAIN MAY PERSIST THROUGH LATE TONIGHT AS DIVERGENCE
ALOFT IS REINFORCED BY LIFT FROM THE APPROACHING SHORTWAVE TO THE
SOUTH. WEAK CYCLONIC FLOW IN IT'S WAKE TO KEEP THINGS MAINLY ON THE
CLOUDY SIDE WITH A FEW PASSING SHOWERS ON FRI. THE NEXT FRONT
APPROACHES THE SOUTHWESTERN GULF DURING THE DAY SAT WITH MORE RAIN
AND WIND...THOUGH IT LOOKS TO BE A BIT WEAKER THAN THE CURRENT
SYSTEM.

SOUTHWEST...
RAIN IS PERSISTING OVER THE SW MAINLAND AS THE UPPER-LOW IS
MEANDERING JUST OFF-SHORE. AS IT MOVES FURTHER AWAY THE NEXT COUPLE
OF DAYS...THE KUSKOKWIM VALLEY SHOULD SEE A LET UP IN THE STEADIEST
PRECIPITATION...THOUGH FLOW WILL STILL BE ONSHORE OVER BRISTOL BAY
AND THE KUSKOKWIM DELTA...ALLOWING FOR AMPLE CLOUDS AND PERIODS OF
RAIN. THIS ONLY GETS REINFORCED THIS WEEKEND WITH THE NEXT PACIFIC
SYSTEM APPROACHING.

BERING SEA/ALEUTIANS...
THE PACIFIC LOW STEERS WELL SOUTH OF THE WESTERN AND CENTRAL
CHAIN...BUT THEN PINWHEELS BACK NORTHEAST TO THE EASTERN ALEUTIANS
AND AKPEN ON SAT. THUS LOOK FOR THE SENSIBLE WEATHER IMPACTS OF RAIN
AND GUSTY WINDS TO BE EAST OF ATKA.

.LONG TERM FORECAST...
CONSIDERABLE DIFFERENCES IN THE MODELS FOR NEXT WEEK. GFS AND ECMWF
BOTH GENERALLY SHOW THE PERSISTENT UPPER-LVL LOW IN THE BERING SEA TO
EJECT EAST MID TO LATE NEXT WEEK. HOWEVER THE ECMWF TENDS TO DO THIS
IN A COUPLE OF STAGES WITH ONE PIECE OF ENERGY PUSHING THROUGH THE
SOUTHERN MAINLAND ON TUE AND THEN THE PARENT LOW OVER THE SOUTHERN
GULF WED INTO THU. THE GFS ALSO DRAGS THE LOW EAST WED INTO THU...BUT
NOT THE INITIAL PUSH ON TUE. THUS THERE IS RATHER LOW CONFIDENCE IN
THE LONG TERM FORECAST.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...120 130 351
FIRE WEATHER...NONE

MALOY