Gale Warning 523, NWS Anchorage, AK

522 
FZAK61 PAFC 161156
OFFAER

OFFSHORE WATERS FORECAST
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 AM AKDT TUE AUG 16 2011

OFFSHORE WATERS FORECAST FOR THE GULF OF ALASKA WEST OF 144W

WIND FORECASTS REFLECT THE PREDOMINANT SPEED AND DIRECTION
EXPECTED. SEA FORECASTS REPRESENT AN AVERAGE OF THE HIGHEST
ONE-THIRD OF THE COMBINED WIND WAVE AND SWELL HEIGHT.

PKZ399-170300-
400 AM AKDT TUE AUG 16 2011
.SYNOPSIS FOR THE WESTERN GULF OF ALASKA...A WEAK TROUGH WILL
CONTINUE ALONG THE GULF COAST TODAY. WEAK RIDGING WILL BUILD ALONG
THE GULF COAST TONIGHT THROUGH WEDNESDAY NIGHT.

$$

PKZ351-170300-
GULF OF ALASKA OFFSHORE NORTH OF 57N AND WEST OF 144W
400 AM AKDT TUE AUG 16 2011

.TODAY...W WIND 25 KT. SEAS 8 FT. 
.TONIGHT...W WIND 15 KT. SEAS 5 FT. 
.WED...VARIABLE WIND 10 KT. SEAS 4 FT. 
.WED NIGHT...SE WIND 20 KT. SEAS 6 FT. 
.THU...SE WIND 25 KT. SEAS 8 FT.
.FRI...S WIND 25 KT. SEAS 11 FT. 
.SAT...SW WIND 20 KT. SEAS 13 FT.  

$$

PKZ352-170300-
GULF OF ALASKA OFFSHORE SOUTH OF 57N NORTH OF 55N AND WEST OF
144W
400 AM AKDT TUE AUG 16 2011

.TODAY...W WIND 25 KT. SEAS 9 FT. 
.TONIGHT...W WIND 20 KT. SEAS 6 FT. 
.WED...S WIND 15 KT. SEAS 5 FT. 
.WED NIGHT...SE WIND 20 KT. SEAS 6 FT. 
.THU...S WIND 20 KT. SEAS 7 FT. 
.FRI...SW WIND 30 KT. SEAS 15 FT. 
.SAT...SW WIND 25 KT. SEAS 15 FT.  

$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
155 PM AKDT MON AUG 15 2011

.ANALYSIS AND UPPER LEVELS...A COLD UPPER LEVEL LOW HAD DROPPED
DOWN INTO THE NORTHERN GULF THIS MORNING AND IS NOW HEADING OFF
TO THE EAST. RADAR IMAGERY SHOWS THE BULK OF RAIN WITH THIS HAS
MOVED OFFSHORE. SUBSIDENCE ALONG WITH DRIER AIR ON THE BACK SIDE
OF THE LOW HAVE RESULTED IN PARTIAL CLEARING ACROSS SOUTHWEST
ALASKA AND WESTERN PORTIONS OF SOUTHCENTRAL. HOWEVER...THE COLD
AIR ALOFT IS CAUSING CUMULUS TO POP UP AS THE SUN HEATS UP THE
SURFACE. IN ADDITION...WEAK WAVES EMBEDDED IN THE FLOW AROUND THE
LOW CENTER ARE PROVIDING AREAS OF WEAK LIFT WHICH WILL WORK WITH
AN UNSTABLE AIR MASS TO PRODUCE SHOWERS.

A SURFACE LOW OUT AHEAD OF THE UPPER LOW CONTINUES TO DEEPEN OVER
THE NORTH CENTRAL GULF. BUOY 46082 AND MIDDLETON ISLAND RADAR BASE
VELOCITY SHOW INDICATE GALE FORCE NORTHEASTERLIES ON THE NORTH TO
WEST SIDE OF THE LOW CENTER. A TIGHTENING PRESSURE GRADIENT ALONG
THE NORTH GULF COAST ALONG WITH SUPPORTIVE OFFSHORE FLOW ALOFT HAS
CAUSED AN INCREASE IN GAP WINDS ACROSS THE WESTERN PRINCE WILLIAM
SOUND REGION.

OUT WEST...THERE IS SPLIT UPPER LEVEL FLOW WITH A WEAK UPPER LOW
NEAR ADAK WITH TROUGH EXTENDING DUE SOUTHWARD AND A RIDGE OVER-TOP
OF IT FROM THE NORTH CENTRAL BERING TO THE CHUKCHI SEA. AT THE
SURFACE A WEAK LOW AND FRONTAL SYSTEM ARE FOCUSING AREAS OF RAIN
ALONG THE CENTRAL TO EASTERN ALEUTIANS AND SOUTHERN BERING.

.MODEL DISCUSSION...MODELS ALL SEEM TO BE A BIT WEAK ON CENTRAL
PRESSURE OF SURFACE LOW IN THE GULF...SO PREFER A COUPLE MILLIBARS
DEEPER THAN THE NAM WHICH IS THE DEEPEST SOLUTION. GFS BOUNDARY
LAYER WINDS ARE CLOSEST TO VERIFYING BUT STILL A LITTLE ON THE
WEAK SIDE. SO PLAN TO BUMP WINDS UP IN THE VICINITY OF THIS LOW.
OTHERWISE...MODELS ARE IN DECENT AGREEMENT OVER THE SOUTHERN
MAINLAND AND GULF AND WILL MAKE USE OF NAM DUE TO ITS SUPERIOR
HANDLING OF GAP WINDS ALONG THE COAST. MODELS CONTINUE TO STRUGGLE
WITH DEVELOPING LOW MOVING INTO THE GULF WEDNESDAY NIGHT AND
THURSDAY. PLAN TO TREND TOWARD THE NAM WHICH PROVIDES FOR AN
INTERMEDIATE SOLUTION BETWEEN THE ECMWF AND GFS AND CONSISTENCY
WITH PREVIOUS FORECAST UNTIL MODELS LOCK ON TO A COMMON SOLUTION.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...GAP WINDS WILL STRENGTHEN ALONG THE GULF COAST
THIS AFTERNOON AND EVENING AND THEN VERY GRADUALLY DIMINISH DURING
THE DAY TUESDAY AS THE GULF LOW DISSIPATES NEAR SOUTHEAST ALASKA.
WINDS WILL WEAKEN IN TIME FOR A LIGHT SEA BREEZE TO FORM DURING THE
MID TO LATE AFTERNOON TUESDAY. HOWEVER...OFFSHORE FLOW WILL LAST
LONG ENOUGH PRIOR TO THAT FOR TEMPERATURES TO RISE WELL INTO THE 60S
AND POSSIBLE NEAR 70...JUST A LITTLE COOLER THAN A SIMILAR EVENT AT
THE END OF LAST WEEK. OTHER THAN LOCALIZED WINDS THE BIG STORY FOR
THE NEXT FEW DAYS WILL BE CONVECTION. AIR ALOFT WILL REMAIN COLD
WITH UPPER LOW SLOWLY EXITING TO THE EAST AND ANOTHER WEAK TROUGH
DROPPING INTO SOUTHWEST ALASKA TUESDAY PROVIDING SOME REINFORCEMENT
OF COLDER AIR. MEANWHILE...LOW LEVELS WILL WARM A LITTLE WITH SOLAR
HEATING AND WEAK UPPER IMPULSES WILL CONTRIBUTE TO LIFT. TUESDAY
LOOKS LIKE THE MOST UNSTABLE DAY WITH A GOOD AMOUNT OF SUNSHINE TO
START THE DAY UNLIKE TODAY WHILE WEDNESDAY LOOKS MORE STABLE IN TH
NEAR SURFACE LAYER AS UPPER LEVEL FLOW SHIFTS TO SOUTHWEST WITH WEAK
SHORT-WAVE MOVING IN FROM THE WEST. THEREFORE...PLAN TO INCREASE
THE AREA OF THUNDERSTORMS SOUTHWARD ACROSS ANCHORAGE AND DOWN TO
THE KENAI PENINSULA. WEDNESDAY IS LOOKING MUCH CLOUDIER AND COOLER
OVER COASTAL AREAS SO THUNDERSTORM CHANCES WILL BE CONFINED TO
INTERIOR PORTIONS OF THE SUSITNA VALLEY AND THE COPPER RIVER BASIN.
THE UPPER TROUGH WILL PUSH THROUGH ON THURSDAY WITH MORE UNSTABLE
AIR ACROSS THE ENTIRE AREA BUT LITTLE IN THE WAY OF UPWARD VERTICAL
MOTION. THUS EXPECT A MOSTLY CLOUDY DAY WITH ISOLATED TO SCATTERED
SHOWERS.

SOUTHWEST ALASKA...INTERIOR SOUTHWEST ALASKA WILL ALSO SEE FAVORABLE
CONDITIONS FOR THUNDERSTORMS AHEAD OF SHORT-WAVE DROPPING DOWN
FROM THE NORTH TUESDAY AND WEDNESDAY. COASTAL LOCATIONS WILL REMAIN
MOSTLY DRY WITH AREAS OF FOG UNDER LIGHT WINDS. MORE UNSTABLE AIR
WILL MOVE IN THURSDAY BEHIND THE SHORT-WAVE AND THE FRONT EDGE OF
A LOW MOVING INTO THE BERING WILL LIKELY REACH THE COAST BY
AFTERNOON.

BERING SEA/ALEUTIANS...A TROUGH DIGGING INTO THE FAR WESTERN BERING
SEA WILL LEAD TO CYCLOGENESIS TONIGHT AND TUESDAY. THE LOW WILL
REMAIN WEST OF THE FORECAST AREA...BUT A FRONT WILL PUSH EASTWARD
ACROSS THE WESTERN BERING AND ALEUTIANS. ANOTHER SHORT-WAVE DROPPING
INTO THE BACK SIDE OF THE TROUGH WILL LEAD TO DEVELOPMENT OF ANOTHER
LOW ALONG THE ALEUTIANS WEDNESDAY NIGHT. MODELS SHOW POOR CONSISTENCY
IN THE DEPTH AND TRACK OF THIS LOW...SO FORECAST CONFIDENCE IS BELOW
AVERAGE. ALL SOLUTIONS DO TRACK THE LOW TO THE EASTERN BERING BY
THE END OF THE WEEK SPREADING RAIN AND STRONG WINDS ALONG ITS PATH.

.LONG TERM FORECAST...EVEN WITH THE MODEL DIFFERENCES IN TRACK OF
SURFACE LOW ACROSS THE BERING SEA THERE IS GOOD AGREEMENT IN THE
GENERAL EVOLUTION OF THE SYSTEM. EXPECT THE LOW TO TRACK INTO THE
GULF LATE NEXT WEEK INTO THE WEEKEND BRINGING A GOOD SHOT OF RAIN
TO THE SOUTHERN MAINLAND. A WEAK RIDGE WILL BUILD IN ACROSS THE
BERING SEA BEHIND THE LOW AND BRING A RETURN TO MORE BENIGN
CONDITIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

SEB AUG 11