Small Craft Advisory 256, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
415 PM AKDT SUN MAR 22 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS A VERTICALLY STACKED LOW CENTERED JUST SOUTH OF THE GULF
OF ALASKA. AN ELONGATED FRONT STRETCHES EAST-WEST ALONG THE
SOUTHERN GULF AND JUST INTO THE ALASKA PENINSULA. THERE IS AN
INVERTED TROUGH OVER THE EASTERN ALEUTIANS AND EASTERN BERING SEA.
THERE IS AN UPPER LEVEL RIDGE BUILDING OVER THE NORTHERN GULF AND
SOUTHERN ALASKA AND A RIDGE OVER THE WESTERN BERING SEA THAT IS
SLOWLY RETREATING WESTWARD.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT THROUGH THE SHORT
TERM. GENERALLY USED THE GFS FOR THE AFTERNOON FORECAST. FORECAST
CONFIDENCE IS THUS ABOVE NORMAL TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (TONIGHT THROUGH TUESDAY)...

A CUT OFF UPPER LEVEL HIGH HAS SITUATED ITSELF ACROSS SOUTHCENTRAL
ALASKA THIS AFTERNOON AS EVIDENT BY THE CLEARING SKIES. TEMPERATURES
WARMED NICELY INTO THE MID TO UPPER 40S WITH A FEW PLACES IN THE
MATANUSKA VALLEY SURPASSING THE 50 DEGREE MARK. AS TEMPERATURES
BEGIN TO COOL UNDER CLEAR SKIES TONIGHT AND WITH THE SUBSIDENCE
ASSOCIATED WITH THE UPPER LEVEL HIGH...SOME PATCHY FOG IS EXPECTED
TO DEVELOP FROM THE KENAI PENINSULA...TO ANCHORAGE...THE COPPER
RIVER BASIN AND UP INTO THE MAT-SU VALLEY. THE FOG WILL BE BURN
OFF DURING THE LATE MORNING HOURS AND GIVE WAY TO ANOTHER WARM AND
BEAUTIFUL SPRING AFTERNOON.

MEANWHILE...KODIAK ISLAND WILL REMAIN ON THE NORTHERN PERIPHERY OF
A LOW TRAPPED IN THE NORTH PACIFIC. MULTIPLE WEAK SYSTEMS WILL
ROTATE AROUND THIS LOW AND CONTINUE A SPELL OF CLOUDY SKIES AND
RAIN SHOWERS. BEST CHANCES FOR RAINFALL WILL BE SEEN MONDAY
AFTERNO0N AS AN UPPER LEVEL LOW PUSH ACROSS THE ISLAND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)... A LOW
JUST SOUTH OF THE GULF OF ALASKA IS STARTING TO PUSH RAIN TO THE
ALASKA PENINSULA THIS AFTERNOON AND EVENING. SOME WIND IS
ACCOMPANYING THIS FRONT. OVER THE INTERIOR...HIGH PRESSURE IS
DOMINATING THE SITUATION WITH ONLY HIGH CLOUD COVER.
HOWEVER...ALONG THE COAST OF THE KUSKOKWIM DELTA...STRATUS REMAINS
AND WILL MOVE OFF THE COAST AS THE FRONT ALONG THE ALASKA
PENINSULA MOVES INTO THE EASTERN BERING SEA TOMORROW. DUE TO
STRATUS AND SOME SUN TODAY IN THE INTERIOR OF THE KUSKOKWIM
DELTA...SOME FOG IS EXPECTED TONIGHT INTO THE MORNING.

AS A SECONDARY UPPER LEVEL LOW MOVES UP OUT OF THE NORTH PACIFIC
MONDAY NIGHT...MORE RAIN WILL PUSH TO THE ALASKA PENINSULA. THIS
FRONT WILL BE PUSHED FARTHER NORTH TUESDAY AS A SURFACE LOW MOVES
TO 50N 155W. MODERATE WINDS WILL CONTINUE ALONG THE ALASKA
PENINSULA WITH SHOWERS MOVING INTO THE BRISTOL BAY AREA. IN
ADDITION...AN UPPER LEVEL FRONT MOVES INTO THE NORTHERN BERING SEA
AND ACTS WITH THE FRONT FROM THE SOUTH TO CREATE AN AREA OF SHOWERS
EXTENDING FROM KUSKOKWIM BAY NORTH TO UNALAKLEET. AS THE SURFACE
LOW IN THE NORTH PACIFIC PUSHES NEAR THE SHUMAGIN ISLANDS
WEDNESDAY AFTERNOON...MORE PRECIP IS ANTICIPATED AROUND BRISTOL
BAY TO JUST EAST OF BETHEL.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
AN UPPER LEVEL FEATURE MOVING THROUGH THE CENTRAL BERING CREATING
SOME RAIN AND SNOW SHOWERS AND MODERATE WINDS FOR FREEZING SPRAY
NORTH OF 55N. A FRONT MOVING TO THE ALASKA PENINSULA ALSO BRINING
RAIN AND MODERATE WINDS TO THE AREA. THE FRONT WILL MOVE TO THE
WEST THROUGH TOMORROW NIGHT WITH MOSTLY SNOW OVER THE BERING AND
RAIN ALONG THE ALEUTIANS EAST OF ADAK. THE LOW WILL ROTATE AROUND
IN THE SOUTH CENTRAL BERING SEA INTO WEDNESDAY WITH SHOWERS OVER
THE CENTRAL AND WESTERN BERING SEA. FOG WILL REMAIN OVER THE
WESTERN BERING SEA UNDER HIGH PRESSURE. IN THE EASTERN BERING
SEA...A MODERATE SURFACE LOW NEAR THE SHUMAGIN ISLANDS BRINING
MORE RAIN TO THE EASTERN BERING BUT TEMPERATURES WILL REMAIN COLD
ENOUGH FOR SNOW OVER THE PRIBILOF ISLANDS.

&&

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

MODELS ARE GENERALLY IN GOOD AGREEMENT WITH THE SYNOPTIC PATTERN
DURING THE LONG RANGE...THEREFORE A BLEND OF THE ECMWF AND GFS WAS
USED TO UPDATE THE FORECAST. THE MAIN FOCUS FOR THE EXTENDED
PERIODS IS A STACKED STORM SYSTEM THAT ORGANIZES NEAR KODIAK
ISLAND WEDNESDAY INTO THURSDAY. THIS NEXT SYSTEM DEVELOPS AS A
WAVE OF ENERGY ROUNDS THE BASE OF THE UPPER TROUGH OVER THE
BERING/NORTH PACIFIC CUTTING OFF A NEW LOW CENTER JUST SOUTH OF
KODIAK ISLAND. THERE STILL IS UNCERTAINTY ON THE TRACK AND
STRENGTH OF THIS SYSTEM THURSDAY INTO THE WEEKEND AND SHOULD BE
MONITORED AS MAX GALE WINDS OR POTENTIALLY STRONGER MAY OCCUR
DEPENDING ON HOW THIS SYSTEM EVOLVES.

EARLY WEDNESDAY MORNING...RAIN AND GUSTY WINDS DEVELOP ALONG A
FRONTAL BOUNDARY MOVING INTO SOUTHERN GULF AND THEN MOVES INTO
THE NORTHERN GULF BY THE AFTERNOON. THE FRONT STALLS ALONG THE
COAST THROUGH SATURDAY NIGHT BRINGING A PROLONGED WET AND WINDY
EVENT...MAINLY ALONG THE GULF COASTAL LOCATIONS. FOR THE ALASKA
PENINSULA AND BERING...GUSTY NORTHERLY WINDS AND PRECIPITATION
CHANCES INCREASE ALONG THE BACKSIDE OF THE LOW WEDNESDAY INTO
THURSDAY AS THE OCCLUDED SURFACE LOW NEARS KODIAK ISLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...MMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JN
LONG TERM...KH