Small Craft Advisory 25, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
405 PM AKST FRI JAN 9 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL FLOW IS ONCE AGAIN IN TRANSITION AS MULTIPLE CLOSED
LOWS AND HIGHS TRANSIT THE REGION. AN UPPER LEVEL RIDGE PERSISTS
FROM BRITISH COLUMBIA NORTHWESTWARD TO THE NORTHEAST PORTION OF
MAINLAND ALASKA. A DEEP CLOSED UPPER LEVEL LOW NORTH OF THE PRIBILOF
ISLANDS IS LIFTING NORTHWARD. A TROUGH AXIS EXTENDING FROM THIS
LOW ACROSS SOUTHWEST ALASKA AND INTO THE GULF IS BEGINNING SPLIT
INTO TWO TROUGHS...WITH SOME OF THE ENERGY LIFTING NORTHWARD ACROSS
WESTERN ALASKA AND SOME HEADED EASTWARD ACROSS THE GULF OF ALASKA.
TRANSPORT OF TROPICAL AIR HAS ENDED THOUGH THE AIR MASS IN PLACE
OVER THE GULF AND MUCH OF SOUTHWEST ALASKA REMAINS QUITE WARM.
RADAR IMAGERY SHOWS A BAND OF PRECIP AHEAD OF THE UPPER TROUGH
HEADED INLAND ACROSS SOUTHWEST ALASKA. COLDER AIR IS MOVING BACK
IN WITH THE TROUGH...BUT THERE REMAINS AREAS OF FREEZING RAIN OUT
AHEAD OF IT...PRIMARILY OVER THE SOUTHERN KUSKOKWIM VALLEY.

THE MAIN AREA OF PRECIP OVER SOUTHCENTRAL IS EASTERN PRINCE
WILLIAM SOUND UP TO THE COPPER BASIN AS UPPER SHORT-WAVES AHEAD
OF THE MAIN TROUGH AXIS TRACK NORTHWARD UP THE WEST SIDE OF THE
DOWNSTREAM RIDGE. FREEZING RAIN AND DRIZZLE ACROSS NORTHEAST
PRINCE WILLIAM SOUND AND THE COPPER RIVER BASIN BECAME ISOLATED
LATE THIS AFTERNOON. PRECIP ACROSS THE REMAINDER OF THE AREA IS
NOTABLY LIGHTER AND SPARSER.

MEANWHILE A TROUGH IS DIGGING EASTWARD ACROSS THE NORTH PACIFIC.
A SURFACE LOW HAS DEVELOPED SOUTH OF THE WESTERN ALEUTIANS WITH
SIGNS OF TRIPLE POINT DEVELOPMENT RIGHT AT THE BASE OF THE TROUGH.
WOULD EXPECT THIS TREND OF MULTIPLE LOW DEVELOPMENT TO CONTINUE AS
THE TROUGH AND SUBTROPICAL JET CONTINUE EASTWARD ACROSS THE NORTH
PACIFIC. THE ALEUTIANS ARE NORTH OF THE TROUGH AT THE MOMENT...BUT
AS SURFACE LOWS DEVELOP THE TROUGH IS MAKING SLOW NORTHWARD PROGRESS
WITH STRONGER WINDS AND RAIN HEADED TOWARD THE ALEUTIANS.

&&

.MODEL DISCUSSION...
AS HAS BEEN THE CASE OF LATE ALL THE MODELS SHOW A SIMILAR EVOLUTION
OF THE LARGE SCALE PATTERN OVER THE NEXT COUPLE DAYS. THERE ARE SOME
MINOR DIFFERENCES WITH PLACEMENT OF A CLOSED LOW OVER THE GULF FRIDAY
NIGHT AND SATURDAY WHICH WILL DETERMINE HOW MUCH PRECIP WILL MOVE
ONSHORE ALONG THE NORTH GULF COAST. THERE IS ENOUGH OF A CONSENSUS
AMONG THE SOLUTIONS TO INCREASE POPS ALONG THE COAST AND AROUND PRINCE
WILLIAM SOUND. OTHER THAN THIS FEATURE THE PRIMARY FORECAST CHALLENGE
OVER THE SOUTHERN MAINLAND THE NEXT COUPLE DAYS WILL BE DETERMINING
THE DISTRIBUTION AND EXTENT OF FOG.

MODELS HAD BEEN ALL OVER THE PLACE THE LAST COUPLE DAYS WITH LOWS
SOUTH OF THE ALEUTIANS. THE 12Z GUIDANCE IS IN MUCH BETTER AGREEMENT.
THERE ARE STILL SOME MINOR DIFFERENCES IN LOW POSITIONS...BUT NOTHING
THAT GREATLY IMPACTS THE FORECAST ALONG THE ALEUTIAN CHAIN.
THUS...FORECAST CONFIDENCE IS INCREASING.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
FAIRLY BENIGN CONDITIONS CAN BE EXPECTED OVER THE NEXT SEVERAL
DAYS AS INLAND PORTIONS OF SOUTHCENTRAL AK BEGIN TO DRY OUT THIS
EVENING AND THEN REMAIN THAT WAY THROUGH THE WEEKEND WITH WEAK
HIGH PRESSURE MOVING OVERHEAD. THIS WILL INTRODUCE THE POTENTIAL
FOR FOG ACROSS THE COOK INLET REGION BEGINNING LATE TONIGHT AND
PERSISTING THROUGH SUNDAY MORNING. LIGHT SHOWER ACTIVITY WILL
PERSIST ALONG THE COAST IN THE VICINITY OF A WEAK UPPER LOW OVER
THE GULF...WITH SHOWERS INCREASING IN COVERAGE BY SATURDAY NIGHT
AS THE LOW RETROGRADES WESTWARD. PRECIPITATION TYPE WILL REMAIN A
CHALLENGE AS THE AIR ALOFT REMAINS FAIRLY WARM AND SURFACE
TEMPERATURES HOVER NEAR OR SLIGHTLY BELOW FREEZING...YIELDING A
MIX OF RAIN...SNOW...AND POTENTIALLY SOME LIGHT FREEZING RAIN AT
TIMES.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
AS THE LOW OVER THE NORTHERN BERING CONTINUES ITS TRACK NORTH
RIDGING WILL MOVE IN OVER THE SOUTHWEST. THIS WILL CLEAR OUT THE
REMAINDER OF THE PRECIPITATION TONIGHT AND MAKE WAY FOR FOG
DEVELOPMENT FOR THE AREA. TEMPERATURES SHOULD REMAIN ABOVE NORMAL
WITH THE WARM SOUTHEAST FLOW THAT WILL REMAIN OVER THE REGION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE SOUTHEASTERLY FLOW OVER THE ALEUTIANS WILL BRING UP MORE WARM
AIR AND MOISTURE TO THE ISLANDS THAT WILL TRANSITION THE RAIN AND
SNOW MIX OVER TO RAIN. THE WARM AIR WILL ALSO PUSH INTO THE BERING
BRINGING RAIN TO THE PRIBILOF ISLANDS TOMORROW NIGHT. AT THIS SAME
TIME COLDER AIR WILL MOVE BACK IN OVER THE WESTERN ALEUTIANS
TRANSITIONING THAT AREA BACK TO A RAIN AND SNOW MIX.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
SAME BASIC PATTERN CONTINUES WITH THE STRONG JET STREAM REMAINING
CENTERED AROUND 35N AND BLOCKING RIDGE OVER THE WEST COAST OF
NORTH AMERICA EXTENDING ACROSS NORTHERN ALASKA WITH LITTLE CHANGE
EXPECTED IN THESE LARGE SCALE FEATURES FOR THE NEXT WEEK. THE
RESULTS WILL BE A CONTINUING SERIES OF STRONG LOW PRESSURE SYSTEMS
DEVELOPING IN THE NORTH PACIFIC AND TRACKING TO THE EAST WITH MUCH
OF THE ENERGY STAYING SOUTH OF THE AREA. SEVERAL OF THE LOWS WILL
TURN NORTH AND MOVE INTO THE GULF OF ALASKA AS THEY FILL THEN
DISSIPATE. ONE WILL ARRIVE IN THE WESTERN GULF IN THE SUNDAY
NIGHT AND MONDAY TIME PERIOD...THE NEXT WILL TRACK INTO THE
CENTRAL GULF AROUND TUESDAY NIGHT AND A THIRD WILL MOVE INTO THE
WESTERN GULF THURSDAY OR FRIDAY. GIVEN THAT THESE SYSTEMS WILL ALL
BE WEAKENING AS THEY LIFT NORTH THE MAIN IMPACT WILL BE TO
CONTINUE TO BRING PRECIPITATION TO COASTAL AREAS AND OCCASIONALLY
FURTHER INLAND AND TO KEEP TEMPERATURES ABOVE NORMAL.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 174 175 176 177 178 411.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...SB
SOUTHCENTRAL ALASKA...CB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...JR