Small Craft Advisory 644, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
404 PM AKDT TUE AUG 26 2014

.ANALYSIS AND UPPER LEVELS...
THE REMNANTS OF A STACKED AND DECAYING LOW PRESSURE SYSTEM /NOW AN
OPEN WAVE/ CAN BE SEEN SWIRLING TO THE EAST ACROSS THE GULF THIS
AFTERNOON...WITH RADAR SURFACE REFLECTIONS NOW WELL TO THE EAST OF
CAPE SUCKLING. THE NEXT OF TWO SYSTEMS CAN VISIBLE ON WATER VAPOR
IMAGERY. THE FIRST UPPER LEVEL SYSTEM IS DIVING SOUTH FROM SIBERIA
AND WILL SCOOT ACROSS THE WESTERN MAINLAND COAST BEFORE MOVING INTO
THE GULF. THE SECOND UPPER LEVEL FEATURE IS JUST SOUTH OF THE
KAMCHATKA PENINSULA AND WILL PRIMARILY IMPACT THE WESTERN BERING
THROUGH THE WEEKEND. AT THE SURFACE...SHOWERS ARE WORKING ACROSS
SOUTHWESTERN ALASKA AND THE KENAI PENINSULA...IN RESPONSE TO WEAK
SHORTWAVES ROTATING THROUGH.

&&

.MODEL DISCUSSION...
OVERALL SYNOPTIC MODELS ARE IN EXCELLENT AGREEMENT IN THE UPPER
LEVELS THROUGH THE SHORT TERM. ALL GUIDANCE IS LOCK IN STEP WITH
EACH OTHER ON THE EXIT OF THE OPEN WAVE SHIFTING THROUGH THE
NORTHERN PANHANDLE. THE UPPER LEVEL LOW ACROSS THE BERING STRAIT
IS BEING HANDLED WELL ACROSS THE BOARD. DIFFERENCES BEGIN TO
EMERGE AT THE SURFACE BETWEEN GUIDANCE AS THE FEATURE MOVES
ACROSS THE AKPEN TOMORROW AFTERNOON. OVERALL TIMING AND INTENSITY
IS SIMILAR. THE NAM AND CANADIAN ARE THE STRONGEST AND SLOWEST
WHEN COMPARED TO THE GFS AND ECMWF...THOUGH THE DIFFERENCES WERE
ONLY WITHIN 1-2 HPA AND 100 NM OF EACH OTHER. ALL MODELS CONTINUE
TO HINT AT A FRONT MOVING ACROSS THE INTERIOR WITH A BIG SURGE OF
COLD AIR DIVING IN BEHIND IT. PERHAPS IT IS A SIGN OF THE CHANGING
SEASONS...

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
RELATIVELY DECENT CONDITIONS WILL PERSIST FOR MUCH OF SOUTHCENTRAL
THROUGH THE EVENING HOURS. CLOUD COVER WILL CONTINUE TO EXPAND
AND SHIFT EAST A HEAD OF THE NEXT SYSTEM...HELPING TO KEEP THE
OVERNIGHT LOWS WARMER TONIGHT. FLOW WILL GRADUALLY TURN
SOUTHWESTERLY INTO TOMORROW MORNING AND AFTERNOON BRINGING IN THE
INCREASED CHANCE FOR SHOWERS INTO THE AFTERNOON HOURS ON WEDNESDAY.
AS THE LOW WORKING ACROSS THE ALASKA PENINSULA DIVES INTO THE GULF
OVERNIGHT WEDNESDAY...FLOW WILL BACK TO THE SOUTHEAST AND EXPECT
THE TYPICAL RAIN SHADOW TO DEVELOP ACROSS THE LEE OF THE
CHUGACH...WHILE ANOTHER INCH OR MORE OF RAIN WILL FALL ACROSS
WESTERN PRINCE WILLIAM SOUND.

SOUTHWEST ALASKA...
ONSHORE FLOW WILL CONTINUE INTO TOMORROW AFTERNOON WITH GENERAL
OFF AND ON SHOWERS PERSISTING THROUGH THE OVERNIGHT HOURS. THE LOW
PRESSURE SYSTEM THAT IS SET TO DIVE SOUTH ACROSS THE WESTERN
COASTLINE WILL BE THE DOMINANT WEATHER OF THE NEXT FEW DAYS. AS IT
SLIDES ACROSS THE AKPEN...PRECIP WILL OVERSPREAD AREAS SOUTH AND
EAST OF DILLINGHAM. RAIN WILL CONTINUE THROUGH TOMORROW NIGHT
UNTIL RIDGING MOVES OVERHEAD...BRINGING BACK A LULL IN RAINS.

BERING SEA/ALEUTIANS...
THE COMBINATION OF THE UPPER LEVEL LOW DIVING SOUTH ACROSS THE
BERING STRAIT AND A STRENGTHENING SURFACE LOW ACROSS THE BERING
SEA...WILL BRING A QUICK BLAST OF RAIN TO THE PRIBS OVERNIGHT AND
MOVE OUT BY TOMORROW MORNING. ONCE THE RAINS HIT...CEILINGS WILL
FALL AND WILL LINGER THROUGH THE WEEK. ON THE BACK SIDE OF THE
SYSTEM IS A DECENT PUSH OF COLD AIR. WINDS WILL INCREASE TO NEAR
GALE FORCE IN RESPONSE. A NORTHWEST PACIFIC LOW/FRONT WILL
APPROACH THE WESTERN ALEUTIANS TOMORROW AND THURSDAY.

&&

.LONG TERM FORECAST...
AN UPPER LEVEL WEAK RIDGE WILL CONTINUE TO BUILD OVER THE
NORTHERN GULF OF ALASKA COASTLINE RESULTING IN THE TURNAGAIN ARM
WINDS PICKING UP THROUGH THIS UPCOMING WEEKEND. A LOW PRESSURE
SYSTEM WILL BE MOVING THROUGH THE BRISTOL BAY REGION HEADING INTO
THE WEEKEND. THE FRONTAL BOUNDARY ASSOCIATED WITH THIS SYSTEM
WILL BE POSITIONED NEAR KODIAK ISLAND RESULTING IN SOUTHWESTERLY
FLOW AIDING IN BRINGING MOISTURE UP THROUGH THE COOK INLET INTO
THE SOUTHEAST MAINLAND. BY MONDAY AFTERNOON THE LOW WILL BE
LOCATED NEAR SEWARD WITH MOISTURE BEING PUSHED FARTHER INLAND INTO
THE SOUTHEAST MAINLAND. THE MATANUSKA VALLEY AND COOK INLET
EXTENDING FARTHER SOUTHWARD WILL BE ON THE BACKSIDE OF THE LOW
PRESSURE SYSTEM RESULTING IN NORTHERLY WINDS BY MONDAY GOING INTO
TUESDAY. A LOW PRESSURE SYSTEM WILL BE POSITIONED OVER THE
EASTERN BERING SEA SATURDAY MORNING WITH THE FRONTAL BOUNDARY
MOVING INLAND OVER THE SOUTHWEST ALASKA COASTLINE. THIS SYSTEM
WILL TRACK THROUGH THE BRISTOL BAY AREA BRINGING MORE CLOUDS AND
RAIN TO THE SOUTHWEST ALASKA REGION THROUGH THE WEEKEND. BY MONDAY
THE MAJORITY OF THE BERING SEA AND SOUTHWEST ALASKA WILL HAVE AN
UPPER LEVEL RIDGE MOVING INTO THE AREA. THIS WILL RESULT IN
NORTHWESTERLY FLOW AND DRIER CONDITIONS HEADING INTO THE EARLY
PART OF NEXT WEEK.

&&

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

SS/PLD - AUG 14