Small Craft Advisory 818, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
446 PM AKDT SUN OCT 18 2015

.ANALYSIS AND UPPER LEVELS...

A BROAD UPPER LEVEL TROUGH THAT COVERS THE ENTIRE BERING AND
WESTERN MAINLAND ALASKA IS DRIVING THE WEATHER ACROSS THE REGION
TODAY. AN UPPER LEVEL LOW CONTINUES TO LINGER JUST OFFSHORE OF
THE KUSKOKWIM DELTA...WHILE AN ASSOCIATED SHORTWAVE IS PUSHING
NORTHWARDS INTO PRINCE WILLIAM SOUND. MEANWHILE...A DEVELOPING
UPPER LOW IS LOCATED JUST TO THE SOUTH OF THE CENTRAL ALEUTIAN
ISLANDS AND IS EXPECTED TO IMPACT WEATHER ACROSS THE SOUTHWEST
MAINLAND AND SOUTH CENTRAL OVER THE NEXT FEW DAYS. AT THE
SURFACE...A WEAKENING LOW IS BRINGING OCCASIONAL SHOWERS TO THE
SOUTHWEST MAINLAND...WHILE A LOW IN THE NORTHERN GULF HAS BEEN
SUPPORTING WIDESPREAD RAINFALL ACROSS SOUTHCENTRAL.

&&

.MODEL DISCUSSION...

MODELS ARE IN GENERAL AGREEMENT IN THE RAPID DEVELOPMENT OF A LOW
PRESSURE SYSTEM SOUTH OF THE CENTRAL ALEUTAINS MOVING NORTHWARD
TOWARDS THE AKPEN AND EVENTUALLY SOUTHCENTRAL OVER THE NEXT FEW
DAYS. THE GFS MODEL HAS THE MOST CONSISTENT SOLUTION AND HAS THE
BEST TIMING FOR ITS PROGRESSION...AND WAS THE MODEL OF CHOICE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL TROUGH MOVING NORTHWARD OVER SOUTHCENTRAL WILL
BRING YET ANOTHER ROUND OF RAIN TO SOUTHCENTRAL INTO MONDAY
MORNING. AS THIS RAIN BEGINS TO CLEAR FROM THE SOUTH LATE
TONIGHT...AREAS OF FOG AND LOW STRATUS ARE LIKELY TO FORM
THROUGHOUT THE COOK INLET REGION AS THE BOUNDARY LAYER REMAINS
VERY WET FROM RECENT RAINS AND LIGHT WINDS. OTHER THAN THE CHANCE
OF FOG AND LOW STRATUS...CONDITIONS THROUGHOUT THE AREA WILL BE
GENERALLY QUIETER ON MONDAY AS WEAK RIDGING MOVES OVERHEAD IN
ADVANCE OF THE NEXT GULF LOW EXPECTED TO ENTER THE SOUTHERN GULF
MONDAY AFTERNOON. THIS LOW WILL THEN BE THE WEATHER MAKER
(ESPECIALLY FOR GULF COAST COMMUNITIES) INTO TUESDAY. GENERALLY
GALES ARE EXPECTED ACROSS THE GULF IN ADVANCE/WITH THE ASSOCIATED
FRONT AS IT MOVES NORTH WITH STORM FORCE WINDS LIKELY OVER
SHELIKOF STRAIT MON EVENING. GUSTY WINDS AND RAIN SPREAD TOWARDS
PRINCE WILLIAM SOUND BY TUESDAY.

ONE PIECE OF GOOD NEWS FROM THIS SYSTEM IS THAT THERE IS
INCREASING CONFIDENCE THAT THE LOW WILL STAY FAR ENOUGH SOUTH IN
THE GULF TO KEEP MUCH OF SOUTHCENTRAL DRY WITH EVEN A FEW BREAKS
IN THE CLOUDS FROM LATE MONDAY INTO TUESDAY. NORTHEASTERLY WINDS
FROM THE MATANUSKA VALLEY INTO COOK INLET WILL ALSO HELP IN
KEEPING ANY RAIN CONFINED TO THE GULF COAST...AND WILL ALSO FORCE
ANY FOG/STRATUS THAT DOES FORM AROUND COOK INLET TO DISSIPATE BY
TUESDAY MORNING.

&&

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

AN UPPER LOW SITUATED JUST OVER THE KUSKOKWIM BAY WILL CONTINUE TO
DRIFT NORTH ALONG THE KUSKOKWIM DELTA COAST THROUGH MONDAY AND
WILL BRING SOME RAIN SHOWERS MAINLY TOWARD COASTAL AREAS. AS
THIS FEATURE MOVES NORTH...A STRONG GALE FORCE FRONT WILL MOVE
SOUTH OF THE ALASKA PENINSULA MONDAY INTO TUESDAY...BRINGING
INCREASING EASTERLY WINDS ACROSS THE BRISTOL BAY REGION ALONG WITH
RAIN THREATS TO THE SOUTHWEST COAST EXTENDING INTO INTERIOR
BRISTOL BAY. WINDS AND PRECIPITATION WILL SLOWLY SUBSIDE BEGINNING
TUESDAY NIGHT AS THE PRIMARY LOW MOVES EAST AWAY FROM THE AREA
ACROSS THE GULF OF ALASKA.

&&

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

A BROAD UPPER TROUGH OVER THE CENTRAL BERING WILL CONTINUE TO
SUPPORT SPOTTY SHOWERS ALONG WITH WEAKENING NORTHERLY WINDS
THROUGH MONDAY. A GALE FORCE FRONT WILL MOVE INTO THE FAR EASTERN
ALEUTIANS AND ALASKA PENINSULA ON MONDAY INTO TUESDAY...WITH A
POSSIBLE SECONDARY LOW DEVELOPING ALONG THE SURFACE FRONT NORTH OF
PORT HEIDEN TUESDAY AS THE PRIMARY LOW MOVES EAST ACROSS THE
SOUTHERN GULF OF ALASKA. MEANWHILE...A SHARPLY-DEFINED COLD FRONT
MOVES EAST ACROSS THE WESTERN ALEUTIANS MONDAY AND MONDAY NIGHT
AND EXTENDS TO INCLUDE THE CENTRAL ALEUTIANS FOR TUESDAY AND
TUESDAY NIGHT BEFORE SHOWING SIGNS OF WEAKENING. STRONG WEST
WINDS TO NEAR GALE FORCE AND RAIN WILL IMPACT THESE AREAS ALONG
THIS FRONT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE PATTERN LOOKS TO BE ACTIVE FOR THE SECOND HALF OF THE WEEK AND
MOVING INTO THE WEEKEND. TUESDAY NIGHT THERE IS GOOD AGREEMENT ON
A LOW MOVING INTO THE GULF FROM THE SOUTHWEST BRINGING WARM AIR
TO THE SOUTHCENTRAL AND RAIN ALONG THE NORTH GULF COAST. THIS
SYSTEM WILL PUSH OFF TO THE EAST AND THEN THE MODELS BECOME MORE
CHAOTIC. SOMETIME ON WEDNESDAY ANOTHER LOW WILL APPROACH THE
WESTERN ALEUTIANS BUT THERE IS DISCREPANCY ON WHERE THE LOW WILL
SETUP OR IF AND WHERE A TRIPLE POINT LOW WILL DEVELOP RESULTING IN
LOWER CONFIDENCE. BECAUSE OF THE VARIATION IN DETERMINISTIC
SOLUTIONS A COMBINATION OF ENSEMBLES WAS USED...PRIMARILY THE EC
ENSEMBLE AND THE NAEFS. THIS NEW SOLUTION BRINGS AN ELONGATED LOW
INTO THE WESTERN ALEUTIANS THURSDAY EVENING AND THEN TRACKS IT
OVER THE ALASKA PENINSULA FRIDAY NIGHT AND INTO THE GULF SATURDAY
NIGHT INTO SUNDAY. WITH THIS MORE SOUTHERLY TRACK THE MAJORITY OF
THE RAIN WILL BE ALONG THE ALEUTIANS AND EVENTUALLY THE NORTH GULF
COAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 138. GALES 119 120 130 131 132 136 137 150 155 160
165 351 352.

&&

SYNOPSIS AND MODEL DISCUSSION...EN
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...DK