Small Craft Advisory 901, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
458 AM AKST WED NOV 12 2014

.ANALYSIS AND UPPER LEVELS...

AN UPPER LEVEL CLOSED HIGH PRESSURE IS LOCATED JUST NORTH OF
JUNEAU WITH THE AMPLIFIED RIDGE EXTENDING THROUGH THE NORTHWEST
INTO THE BEAUFORT SEA. THERE IS AN UPPER LEVEL CUT-OFF LOW OVER
THE CENTRAL ALEUTIANS WITH AN INVERTED TROUGH EXTENDING THROUGH
THE CENTRAL BERING SEA INTO THE KAMCHATKA PENINSULA. THE SURFACE
HAS A FRONTAL BOUNDARY PUSHING THROUGH JUST SOUTH OF KODIAK
EXTENDING THROUGH THE ALASKA PENINSULA INTO THE BRISTOL BAY
REGION. THERE IS A STRONG 130 KNOT SOUTH TO NORTH MERIDIONAL JET
STREAK OVER THE EASTERN ALEUTIANS THROUGH THE SOUTHWEST COASTLINE
INTO THE BERING STRAIT. THE SATELLITE IMAGERY IS SHOWING A LARGE
SHIELD OF MOISTURE THROUGH SOUTHWEST ALASKA INTO THE NORTH SLOPE
REGION. THERE IS ABUNDANT MOISTURE OVER KODIAK ISLAND EXTENDING UP
THROUGH THE COOK INLET AND FARTHER INLAND INTO SOUTHCENTRAL AREA.
THE GRADIENT CONTINUES TO STRENGTHEN THROUGH THE ALASKA RANGE
WITH SURFACE OBSERVATIONS FROM ILIAMNA AND SPARREVOHN REPORTING
GUSTS TO LOWER TO MID 50 KNOT RANGE. THE SURFACE TEMPERATURES
FROM KODIAK ISLAND THROUGH BRISTOL BAY ARE ALL IN THE MID 40S AND
SLIGHTLY COOLER INLAND. WITH THE SOUTH TO SOUTHEASTERLY FLOW
MOISTURE IS BEING TRANSPORTED INTO THE NORTHERN GULF COASTLINE.
RADAR IS SHOWING RAIN THROUGHOUT THE EASTERN KENAI PENINSULA INTO
THE PRINCE WILLIAM SOUND. THE ANCHORAGE BOWL IS STILL DOWNSLOPE
DRYING DUE TO SOUTHEASTERLY FLOW IN LOWER LEVEL BUT 500 MB WIND
FLOW IS MORE SOUTHERLY. THIS SHOULD EVENTUALLY ALLOW SOME
PRECIPITATION TO FILTER INTO THE ANCHORAGE BOWL.

&&

.MODEL DISCUSSION...

THE MODELS ARE IN GOOD AGREEMENT WITH THE NAM BEING THE PREFERRED
MODEL OF CHOICE FOR WIND DETAIL. A NORTH PACIFIC LOW WILL TRACK
TOWARDS THE EASTERN ALEUTIANS JUST SOUTH OF THE SHUMAGIN ISLANDS
BY WEDNESDAY NIGHT. A FRONTAL BOUNDARY ASSOCIATED WITH THIS LOW
PRESSURE SYSTEM WILL BE EXTENDING THROUGH THE KING COVE AREA INTO
THE EASTERN BERING SEA. THIS LOW WILL TRACK WESTWARD PARALLEL TO
THE EASTERN ALEUTAINS BRINGING GALE FORCE WINDS TO THE AREA...WHILE
MOVING JUST SOUTH OF DUTCH HARBOR BY THURSDAY NIGHT. THE OCCLUDED
LOW OVER NORTHWEST BERING SEA WILL TRACK TO THE SOUTH BEFORE
DISSIPATING BY THURSDAY MORNING. THE WESTERN ALEUTIANS WILL BE ON
THE BACKSIDE OF THIS LOW PRESSURE SYSTEM BRINGING GUSTY NORTHWEST
WINDS.

&&

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

THE SOUTHEASTERLY WINDS WILL REMAIN THROUGH THE GULF WITH THE
STRONGEST WINDS OVER THE WESTERN GULF. THE GUSTY WINDS WILL REMAIN
THROUGH THIS AFTERNOON BEFORE TAPERING OFF AS THE FRONTAL BOUNDARY
MOVES OUT OF THE AREA. THE MARINES WILL HAVE STORM FORCE WINDS
THROUGH THE BARREN ISLANDS EXTENDING INTO THE KAMISHAK BAY. THE
EASTERN KENAI PENINSULA WILL HAVE GALE FORCE WINDS THROUGH
WEDNESDAY NIGHT. THE TURNAGAIN ARM AND THROUGH PORTAGE
VALLEY...MATSU VALLEY AREA WILL CONTINUE TO HAVE GUSTY WINDS
BEFORE DIMINISHING BY LATE WEDNESDAY NIGHT. THE HEAVIEST RAINFALL
WILL BE OVER KODIAK ISLAND FROM THE FRONTAL BOUNDARY MOVING
THROUGH. THERE WILL BE WEAK SHORTWAVE TROUGHS MOVING THROUGH THE
WESTERN TO NORTHERN GULF FOR THE NEXT SEVERAL DAYS. THIS WILL
BRING PRECIPITATION ALONG THE NORTHERN GULF COASTLINE AND INTO
PRINCE WILLIAM SOUND. WITH THE NEGATIVE TILTED UPPER LEVEL RIDGE
LOCATED OVER THE YUKON TERRITORY...THE COPPER RIVER BASIN COULD
POSSIBLE SEE FOG UNDER THE STABLE ENVIRONMENT AS THE RIDGE
GRADUALLY MOVES WESTWARD.

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

A VERY STRONG THERMAL GRADIENT IS SETTING UP ACROSS THE AREA AS
COLD AIR FROM THE BERING SEA IS BEING PUSHED EASTWARD AND CLASHING
WITH VERY WARM AIR MOVING IN FROM THE GULF OF ALASKA. AIDED BY AN
IMPRESSIVE 130 KT SOUTHERLY JET...WINDS ACROSS THE AREA AND
ESPECIALLY ACROSS BRISTOL BAY HAVE BEGUN TO INCREASE. THE SECOND
OF TWO SHORTWAVES MOVING NORTH ALONG THE STATIONARY FRONT IS
EVIDENT ON SATELLITE IMAGERY SOUTH OF KODIAK ISLAND. AS THIS
DISTURBANCE PASSES JUST SOUTH OF BRISTOL BAY LATE TONIGHT...WINDS
WILL REACH PEAK INTENSITY AS THE STRONG PRESSURE GRADIENT IS
SQUEEZED EVEN MORE. NOT ONLY WILL WINDS ACCELERATE THROUGH THE
GAPS NEAR ILIAMNA LAKE...BUT A LAYER OF STABLE AIR ALOFT MAY HELP
SPREAD SOME OF THE STRONGEST WINDS FURTHER WEST AND AWAY FROM THE
IMMEDIATE VICINITY OF THE ALEUTIAN RANGE. MEANWHILE...HEAVY
PRECIPITATION ASSOCIATED WITH THE STALLING FRONT OVER THE AREA IS
ALREADY SPREADING INTO BRISTOL BAY AND THE LOWER KUSKOKWIM VALLEY.
MOST OF THIS WILL FALL AS RAIN...BUT SOME MIXING WITH SNOW CANNOT
BE RULED OUT IN HEAVIER PRECIP NEAR THE KILBUCK MOUNTAINS AND
ACROSS PARTS OF THE KUSKOKWIM DELTA. THIS PATTERN OF WIDESPREAD
RAIN AND GUSTY WINDS WILL CONTINUE THROUGH WEDNESDAY AFTERNOON
BEFORE A MORE SIGNIFICANT LOW PRESSURE SYSTEM IN THE NORTH PACIFIC
DRIFTS FAR ENOUGH NORTH TO WEAKEN THE STATIONARY FRONT AND PUSH
THE PRECIP OUT INTO THE EASTERN BERING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

A BROAD AND COMPLEX LOW PRESSURE SYSTEM WILL REMAIN OVER THE BERING
SEA FOR THE NEXT FEW DAYS. MULTIPLE WEAK LOW CENTERS AND SUBTLE
REINFORCEMENT OF COLD AIR FROM EASTERN RUSSIA WILL RESULT IN A
CONTINUATION OF THE SHOWERY PATTERN FOR MOST OF THE AREA.
TEMPERATURES ARE STILL WARM ENOUGH TO SUPPORT MOST RAIN AS THE
DOMINANT PRECIPITATION TYPE...EXCEPT THE WESTERN 1/3 OF THE
BERING/ALEUTIANS WHERE A RAIN/SNOW MIX CAN BE EXPECTED.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

A HIGH LATITUDE BLOCKING REGIME WILL REMAIN THOROUGHLY ENTRENCHED
THROUGH THE FIRST HALF OF THE NEXT WEEK. THIS INVOLVES A STRONG
RIDGE OF HIGH PRESSURE EXTENDING FROM THE NORTH PACIFIC THAT WILL
ENCOMPASS MUCH OF THE ALASKA MAINLAND...WHILE A BROAD AREA OF LOW
PRESSURE WITH MULTIPLE LOW CENTERS WILL ENCOMPASS THE BERING SEA.
SOUTHEASTERLY WINDS WILL BE SEEN ACROSS THE ALASKA MAINLAND AS A
RESULT OF THE BUILDING HIGH PRESSURE. THIS WILL BRING A PERIOD OF
UNSEASONABLY WARM TEMPERATURES TO MUCH OF ALASKA. HIGH TEMPERATURES
ACROSS SOUTHCENTRAL ALASKA ARE CURRENTLY FORECASTED TO BE AROUND
10 DEGREES ABOVE NORMAL...WITH LOW TEMPERATURES 10 TO 15 DEGREES
ABOVE NORMAL. FOR SOUTHWEST ALASKA...HIGH TEMPERATURES WILL BE
AROUND 10 TO 15 DEGREES ABOVE NORMAL WITH LOWS 15 TO 20 DEGREES
ABOVE NORMAL. FOR A COMPARISON...850 MB TEMPERATURES FOR ANCHORAGE
AVERAGE AROUND NEGATIVE 6 DEGREES CELSIUS FOR MID NOVEMBER AND THE
EXTENDED MODEL GUIDANCE SUGGESTS 850 MB TEMPERATURES FOR ANCHORAGE
TO BE POSITIVE 2 TO 4 DEGREES CELSIUS.

THE BROAD TROUGH OF LOW PRESSURE ACROSS THE BERING SEA WILL KEEP A
RELATIVELY SHOWERY REGIME IN PLACE THROUGH THE BEGINNING OF NEXT
WEEK ACROSS THE BERING SEA AND THE ALASKA PENINSULA. THE PATTERN
WILL BEGIN TO SHIFT A BIT ON FRIDAY AS A VERTICALLY STACKED NORTH
PACIFIC LOW SOUTH OF DUTCH HARBOR BEGINS TO INTERACT WITH A FRONT
AND UPPER LEVEL DISTURBANCE EXTENDING FROM A LOW OVER THE
KAMCHATKA PENINSULA. THIS WILL CREATE A STRONGER CLOSED LOW...BOTH
AT THE SURFACE AND ALOFT...WHICH SHOULD HELP AMPLIFY THE EXISTING
BLOCKING REGIME. A TRIPLE POINT LOW WILL DEVELOP ALONG THE FRONT
ASSOCIATED WITH THE NEW AREA OF LOW PRESSURE IN THE BERING SEA
WHICH SHOULD NUDGE THE RIDGE AXIS A BIT FURTHER EAST AND BRING
RAIN CHANCES BACK TO THE NORTHERN GULF COAST BY LATE SATURDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM...130 131
          GALE...119 120 132 136 137 138 139 141 150.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...PD
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...MMC