Small Craft Advisory 298, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
418 PM AKDT SUN APR 3 2016

.ANALYSIS AND UPPER LEVELS...
A BROAD LONGWAVE TROUGH REMAINS OVER THE CENTRAL NORTH PACIFIC
WITH A STRONG RIDGE TO THE WEST AND A LESS AMPLIFIED RIDGE TO THE
EAST. THE AXIS OF THE RIDGE TO THE EAST STRETCHES FROM THE
SOUTHEAST ALASKA COAST NORTHWESTWARD OVER THE MAINLAND AND EXTENDS
THROUGH THE SEWARD PENINSULA. A STACKED LOW PRESSURE SYSTEM
LOCATED JUST SOUTH OF DUTCH HARBOR IS SENDING A FRONTAL BOUNDARY
NORTHWARD TO THE SOUTHERN ALASKA PENINSULA AND EASTERN ALEUTIAN
ISLANDS. ANOTHER FRONT...LOCATED OVER THE SOUTHEASTERN GULF AND
ADVANCING NORTHWESTWARD IS ASSOCIATED WITH ANOTHER STACKED LOW
THAT IS CURRENTLY SOUTH OF THE GULF.

DRIVING THIS PATTERN OVERALL IS A STRONG AMPLIFYING JET STREAK
OVER THE NORTH PACIFIC WITH THE LEFT EXIT REGION OF THIS JET
LOCATED SOUTH OF THE ALASKA PENINSULA. THIS IS SUPPORTING
STRENGTHENING OF DISTURBANCES ROTATING AROUND THE BASE OF THE
LONGWAVE TROUGH AND SUBSEQUENT WEAKENING OF THE SYSTEMS AS THEY
TRACK FURTHER NORTH TOWARDS THE MAINLAND AND AWAY FROM THE UPPER-
LEVEL SUPPORT.

OVER THE MAINLAND...WEAK UPPER-LEVEL WAVES WITHIN MOIST
SOUTHEASTERLY FLOW ARE SUPPORTING SHOWERS OVER SOUTHWEST ALASKA.
SOUTHCENTRAL ALASKA REMAINS UNDER THE INFLUENCE OF THE UPPER-LEVEL
RIDGE AND A GRADUALLY WEAKENING SURFACE HIGH...LEADING TO ANOTHER
MILD AND DRY SPRING DAY. FURTHER WEST...NORTHERLY FLOW WITH COLD
AIR ADVECTION OVER THE BERING IS SUPPORTING THE TYPICAL SHOWERS
OVER THE ALEUTIANS AND THE PRIBILOF ISLANDS.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO HAVE A GOOD HANDLE ON THE SYNOPTIC FEATURES
THROUGH THE MID TERM. THE LOW PRESSURE SYSTEM SOUTH OF THE
ALEUTIANS WILL TRACK NORTHEASTWARD WHILE UPPER-LEVEL RIDGING OVER
THE MAINLAND WILL PERSIST THROUGH THE SHORT TERM. LATEST MODEL
RUNS ARE TRENDING TOWARDS SLIGHTLY HIGHER QPF AMOUNTS OVER COASTAL
SOUTHCENTRAL AS THE FRONT PUSHES ONSHORE TOMORROW AFTERNOON INTO
THE EVENING. OTHER THAN THAT...MODELS ARE STILL INDICATING A
PRECIP SHADOW OVER THE WESTERN KENAI PENINSULA AND OVER ANCHORAGE
WITH THE MAJORITY OF THE MOISTURE REMAINING ON THE WINDWARD SIDE
OF THE COASTAL MOUNTAINS. AS HAS BEEN THE TREND RECENTLY...THE NAM
WAS USED FOR THE FORECAST PACKAGE FOR ITS HIGHER RESOLUTION.
FORECAST CONFIDENCE REMAINS ABOVE AVERAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2...MON AND TUE)...
A VERY SPRING-LIKE DAY HAS SET UP FOR MUCH OF SOUTH CENTRAL AK.
ABUNDANT SUNSHINE AND LIGHT WINDS THIS MORNING GAVE WAY TO SOME
FAIR-WEATHER AFTERNOON CUMULUS CLOUDS AND SEA BREEZES THIS
AFTERNOON. THE CLOUDS SHOULD DISSIPATE THIS EVENING AFTER DAYTIME
HEATING AND MAKE FOR MOSTLY CLEAR SKIES AND DECENT AURORA VIEWING
CONDITIONS FOR MANY PLACES. THE EXCEPTION TO THIS IS KODIAK. A
WEAK FRONT IS STRETCHED ACROSS THE ISLAND FROM SOUTHEAST TO
NORTHWEST. THIS IS BRINGING GUSTY SOUTHEAST WINDS AND LIGHT
PRECIPITATION TO MUCH OF THE ISLAND...ESPECIALLY AREAS NEAR
AKHIOK. THIS FRONT WILL FALL APART THIS EVENING BEFORE BEING
REINFORCED BY YET ANOTHER FRONT ON MON. THE NEW FRONT WILL BE
COURTESY OF A LOW APPROACHING FROM THE NORTH PACIFIC NEAR COLD
BAY. THIS LOW WILL BECOME THE DOMINANT SYNOPTIC FEATURE TO START
THE WORK WEEK. AS THE FRONT SLIDES NORTH THROUGH KODIAK...IT WILL
JOIN FORCES WITH ANOTHER WEAK FRONT OVER THE NORTHEAST GULF. THIS
WILL ALL WORK IN TANDEM TO INCREASE THE OFFSHORE PRESSURE GRADIENT
WHICH SHOULD HELP TO RAMP UP SOME OF THE LOCAL OUTFLOW WINDS
(MATANUSKA VALLEY...THOMPSON PASS...RESURRECTION BAY).

BY TUE...THE ELONGATED FRONT WILL SWING INTO THE COAST. THIS WILL
USHER CLOUD COVER BACK OVER THE MAINLAND AND SPREAD A HEALTHY
AMOUNT OF RAIN TO COASTAL SITES. IT WILL ALSO MAKE FOR A MINIMUM
GALE-FORCE BARRIER JET. MANY INLAND LOCATIONS COULD REMAIN DRY
THROUGH TUE UNDER CROSS-BARRIER FLOW. BUT WE CANNOT RULE OUT THE
POSSIBILITY OF SOME LIGHT SPILL OVER PRECIPITATION...ESPECIALLY
LATER TUE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
SOME RAIN AND SNOW SHOWERS WILL LINGER AROUND THE COASTAL AREAS OF
THE SOUTHWEST MAINLAND THIS EVENING...AS THE WEAK TROUGH TRACKS
FURTHER NORTHWEST AND OUT OF THE FORECAST AREA TONIGHT. A FRONT
ATTACHED TO A LOW JUST SOUTH OF THE EASTERN ALEUTIANS WILL
CONTINUE TO BRING RAIN AND GUSTY WINDS TO THE ALASKA PENINSULA AND
PARTS OF THE BRISTOL BAY AREA THROUGH MONDAY AFTERNOON. THIS
FRONT WILL STRUGGLE TO MOVE FURTHER INLAND AS THE PARENT LOW
WEAKENS AND STALLS SOUTH OF COLD BAY MONDAY MORNING....LIMITING
THE AMOUNT OF PRECIPITATION SEEN ACROSS THE SOUTHWEST MAINLAND.
THE BULK OF THE PRECIPITATION WILL START OFF CONFINED TO UPSLOPE
LOCATIONS OF THE ALEUTIAN RANGE THROUGH MONDAY NIGHT...BEFORE A
FEW SHOWERS BEGIN TO MOVE INLAND ON TUESDAY. TEMPERATURES ACROSS
THE AREA REMAIN UNSEASONABLY WARM...AND THE MODELS SHOW THAT THIS
ABNORMALLY WARM PERIOD OF WEATHER SHOWS NO SIGNS OF CHANGING IN
THE SHORT TERM.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
NORTHEASTERLY WINDS WILL PREVAIL ACROSS MUCH OF THE BERING SEA
THROUGH MONDAY...BEFORE A FRONT ASSOCIATED WITH A NORTH PACIFIC
LOW ENTERING THE FAR WESTERN BERING SEA TUESDAY MORNING. PRIOR TO
THAT...A LOW CURRENTLY SOUTH OF DUTCH HARBOR WILL MOVE SOUTH OF
COLD BAY MONDAY AFTERNOON...PUSHING A FRONT THROUGH THE
SOUTHEASTERN BERING SEA THROUGH TUESDAY MORNING. THIS WILL
CONTINUE TO BRING SOME GUSTY WINDS AND RAIN TO THE EASTERN
ALEUTIANS AND ALASKA PENINSULA THROUGH EARLY TUESDAY MORNING.
MUCH OF THE ALEUTIANS WILL CONTINUE TO SEE TEMPERATURES A GOOD BIT
ABOVE NORMAL. HOWEVER...THE PRIBILOF ISLANDS WILL CONTINUE TO
FEEL THE EFFECT OF A COLDER AIR MASS THAT CONTINUES TO DROP SOUTH
FROM SIBERIA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A BROAD UPPER LEVEL LOW WILL STRETCH ACROSS THE BERING WITH ITS
MAIN CENTER IN THE SOUTHERN BERING LATE ON TUESDAY. THIS WILL
BRING PRECIPITATION TO THE BERING AND NORTH GULF COAST. EARLY
FRIDAY RIDGING WILL BUILD BACK IN OVER EASTERN ALASKA WHILE THE
TROUGH STAYS OVER THE BERING WHICH WILL BRING ANOTHER PUSH OF
WARM SOUTHERLY FLOW TO THE SOUTHERN MAINLAND. THERE IS OVERALL
DECENT AGREEMENT AMONGST THE MODELS WITH PLACEMENT OF THE MAJOR
FEATURES...ESPECIALLY WITH THE RIDGE. HOWEVER...THEY ARE STILL
STRUGGLING WITH SMALLER LOWS THAT WILL MOVE THROUGH THE BROAD
TROUGH.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119 120 130 131 138 150 155 172 173 174.

&&

SYNOPSIS AND MODEL DISCUSSION...RD
SOUTHCENTRAL ALASKA...MO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PEPE
LONG TERM...DK