Small Craft Advisory 463, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
449 AM AKDT SAT MAY 30 2015

.ANALYSIS AND UPPER LEVELS...

AN UPPER LEVEL RIDGE OVER ALASKA HAS AN AXIS THAT EXTENDS FROM
THE KENAI PENINSULA TO THE NORTHWEST COAST. A FEW CLOUDS ARE
MOVING ALONG A SHORTWAVE OVER THE SOUTHERN ALCAN BORDER AND ALSO
ACROSS THE WEST COAST WHERE A FRONT STALLED JUST OFF THE COAST.
OTHERWISE...MAINLY CLEAR CONDITIONS WITH CALM WINDS ACROSS THE
SOUTHERN MAINLAND. TO THE WEST...AN UPPER LEVEL LOW IS CENTERING
NEAR KAMCHATKA WITH A TROUGH AXIS THAT EXTENDS SOUTH OF THE
EASTERN ALEUTIANS. THE MAIN LOW IS SENDING SHORTWAVE THAT CAN BE
SEEN ON WATER VAPOR SATELLITE IMAGERY THIS MORNING...TRAVELING
EAST ALONG THE SOUTH SIDE OF THE CENTRAL ALEUTIANS. AT THE
SURFACE...A RIDGE REMAINS CENTERED NEAR THE SOUTHERN GULF OF
ALASKA WITH BROAD LOW PRESSURE ACROSS THE BERING. A FRONT BETWEEN
THESE TO FEATURES IS BRINGING LIGHT RAIN AND FOG ACROSS THE
EASTERN BERING WITH A FEW SHOWERS MAKING IT INTO THE KUSKOKWIM
DELTA.

&&

.MODEL DISCUSSION...

MODELS CONTINUE IN GOOD AGREEMENT WITH THE CURRENT SYNOPTIC
PATTERN...HOWEVER ALL MODELS MOVED TOWARD A MORE AGGRESSIVE
APPROACH WITH THE LOW PRESSURE SYSTEM THAT DROPS A COLDER AIR
MASS ACROSS THE EASTERN BROOKS RANGE ON MONDAY. A PERSISTENT
PATTERN IS A REASONABLE FORECAST THROUGH THE WEEKEND AS THE ACTIVE
JET STREAM REMAINS ALONG 40N LEAVING THE AMPLIFIED WAVE PATTERN TO SLOWLY
EVOLVE FROM WEAK ENERGY ALONG THE PERIMETER OF THE UPPER LEVEL SYSTEMS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

WARM AND DRY CONDITIONS ARE EXPECTED TODAY ACROSS THE REGION WITH
THE POSSIBILITY OF RECORD HIGHS IN TALKEETNA...SEWARD...AND
GLENNALLEN. WINDS WILL BE GENERALLY LIGHT...EXCEPT FOR GUSTY
OUTFLOW NEAR WHITTIER WITH WEAKER OUTFLOW FOR SEWARD AND VALDEZ.
HIGH PRESSURE WILL BEGIN TO WEAKEN FROM THE NORTHEAST ON
SUNDAY...AND WHILE TEMPERATURES WILL BEGIN TO SHOW A COOLING
TREND IT WILL STILL BE WARM AND DRY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE STALLED FRONTAL SYSTEM WILL REMAIN STRETCHED FROM THE ALASKA
PENINSULA TO JUST OFFSHORE OF THE SOUTHWEST ALASKA COAST TODAY
AND TONIGHT...CONTINUING TO BRING PERIODS RAIN AND PATCHY FOG TO
THE PENINSULA AND WESTERN MOST COASTAL AREAS. THE FRONTAL SYSTEM
WILL START BREAKING UP ON SUNDAY HOWEVER THE REMNANT MOISTURE
WILL COMBINE WITH INSTABILITY FROM THE THERMAL TROUGH BUILDING IN
FROM THE EAST AND A SMALL SHORTWAVE TROUGH ALOFT TO BRING SHOWERS
AS WELL AS SOME ISOLATED THUNDERSTORMS TO PORTIONS OF INLAND
SOUTHWEST ALASKA SUNDAY AFTERNOON AND EVENING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BROAD VERTICALLY STACKED LOW IN THE BERING WILL CONTINUE TO
WEAKEN AND FILL TODAY...DISSIPATING TONIGHT. A WEAK SURFACE LOW
WILL FORM IN THE CENTRAL ALEUTIANS TODAY THEN SLIDE TO THE EAST
SOUTHEAST FOLLOWING AN UPPER LEVEL TROUGH. A SOMEWHAT STRONGER
FRONTAL SYSTEM WILL APPROACH THE WESTERN ALEUTIANS SUNDAY NIGHT
BRINGING AN AREA OF GALES WITH IT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE HOT AND DRY CONDITIONS THIS WEEKEND WILL GIVE WAY TO A COOLER
AND MORE SHOWERY PATTERN BY EARLY NEXT WEEK AS THE HIGHLY
AMPLIFIED RIDGE IN PLACE OVER MAINLAND ALASKA BEGINS TO BREAK
DOWN WITH THE HELP OF A SHORTWAVE TROUGH DIVING DOWN ITS EASTERN
PERIPHERY AND A BROAD NORTH PACIFIC LOW PASSING SOUTH OF THE GULF.
THIS WILL EVENTUALLY YIELD A DIFFUSE LONGWAVE TROUGH EXTENDING
FROM THE CANADIAN ARCTIC ACROSS THE MAINLAND AND ALASKA PENINSULA
INTO THE NORTH PACIFIC BY THE MIDDLE OF THE WEEK...USHERING IN A
MODERATING TREND IN TEMPERATURES TO NEAR OR SLIGHTLY ABOVE NORMAL
VALUES AND INCREASING CHANCES FOR DIURNAL CONVECTION.
MEANWHILE...BENIGN CONDITIONS WILL DOMINATE MUCH OF THE BERING
BENEATH WEAK UPPER LEVEL FLOW.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...DS
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...CB