Small Craft Advisory 27, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
408 PM AKST SAT JAN 10 2015

.ANALYSIS AND UPPER LEVELS...

ALASKA REMAINS LOCKED IN A PATTERN DOMINATED BY STRONG RIDGING
OVER WESTERN NORTH AMERICA AND A TROUGH OVER THE NORTH
PACIFIC. THIS HAS BEEN BRINGING GENERAL SOUTHERLY FLOW AND
SURGES OF UNSEASONABLY WARM AIR INTO MUCH OF THE STATE. WE FIND A
SIMILAR PATTERN THIS MORNING...THOUGH MOST OF THE MAINLAND IS IN A
BREAK BETWEEN WEATHER SYSTEMS RESULTING IN SOME NICE BREAKS OF
SUNSHINE AROUND COOK INLET TODAY. AN UPPER LOW IN THE CENTRAL GULF
IS MAKING A WESTWARD TRANSIT THROUGH A WEAKNESS IN THE
AFOREMENTIONED STRONG RIDGE...AND IS BRINGING SOME BANDS OF LIGHT
PRECIPITATION TO THE PRINCE WILLIAM SOUND AREA...FALLING LARGELY
IN THE FORM OF RAIN. LIFT ASSOCIATED WITH THIS LOW IS BEING
ENHANCED OVER THE COPPER RIVER BASIN BY AN ACTIVE DEFORMATION ZONE
IN THE AREA...AND IS RESULTING IN SOME LIGHT SNOW FALLING MAINLY
OVER THE CENTRAL BASIN.

WEST OF THE ALASKA RANGE...MIDLEVEL RIDGING IS BUILDING BACK IN
ACROSS THE SOUTHWEST MAINLAND...WHICH HAS AIDED THE DEVELOPMENT
OF AREAS OF DENSE FOG AROUND THE DELTA AND BRISTOL BAY. THIS FOG
HAS BEEN SLOW TO BURN OFF WITH WEAK INSOLATION AND CONTINUED
SUBSIDENCE ALOFT...BUT AS THE GRADIENT CONTINUES TO SLOWLY TIGHTEN
AHEAD OF A BERING SEA TROUGH...A GRADUAL IMPROVEMENT TREND IS
EXPECTED THIS AFTERNOON INTO THIS EVENING. OTHERWISE...CONDITIONS
ARE BENIGN WITH SOME PASSING CIRRUS MOVING OVER FROM THE SOUTH.

WAY OUT WEST...AN ELONGATED AREA OF UNSETTLED WEATHER IS CHURNING
SOUTH OF THE ALEUTIANS...AND IS LOCATED ON THE POLEWARD SIDE OF A
PERSISTENT AND STRONG 200 KT EAST ASIAN JET. A RELATIVELY
DISORGANIZED FRONT IS IMPACTING THE CENTRAL AND EASTERN ALEUTIANS
WITH MORE WARM AIR...RAIN...AND GALE FORCE WINDS. THIS FRONT IS
MAKING SLOW BUT STEADY PROGRESS NORTHWARD AND EASTWARD...AND WILL
REACH THE ALASKA PENINSULA THIS EVENING.

&&

.MODEL DISCUSSION...

WITH THE LONGWAVE PATTERN LOCKED IN PLACE...THE MODELS ARE ALL
DOING RELATIVELY WELL. THE NAM IS HANGING THE UPPER LOW IN THE
GULF TOO FAR EASTWARD...AND WAS DISCARDED IN FAVOR OF THE GLOBAL
MODELS. THIS WILL RESULT IN THE CONTINUATION OF SHOWER ACTIVITY
OVER THE NEXT DAY OR TWO ALONG THE GULF COAST...RATHER THAN
KEEPING IT CONFINED TO THE AREA EAST OF CORDOVA (AS DEPICTED BY
THE NAM). OUT WEST...SIMILAR STORY WITH THE BROAD LOW SOUTH OF THE
ALEUTIANS. THE GFS AND NAM BOTH SEEM A BIT TOO FAR TO THE WEST
WITH THE UPPER LOW BEYOND 36 HOURS...WHILE THE ECMWF/GEM HAVE BEEN
MORE CONSISTENT AND ARE FAVORED FOR THE FORECAST TODAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE WARMER THAN AVERAGE PATTERN CONTINUES FOR MUCH OF THE FORECAST
AREA TODAY WITH NO END IN SIGHT. A WEAKENING SYSTEM IN THE
NORTHEASTERN GULF WILL DRIFT WESTWARD BRINGING RAIN SHOWERS TO
THE PRINCE WILLIAM SOUND AREA BEFORE DISSIPATING OVERNIGHT. THE
COOK INLET REGION WILL STAY CLEAR EARLY IN THE EVENING TONIGHT
BEFORE A MID-LEVEL DECK SPREADS OVERHEAD WITH THE APPROACHING GULF
SYSTEM. ON MONDAY A FRONT MOVING FROM SOUTH TO NORTH IN THE GULF
WILL BRING THE NEXT CHANCE FOR PRECIPITATION TO THE SOUTHCENTRAL.
THE MAJORITY OF THE COOK INLET REGION SHOULD REMAIN DRY UNDER
DOWNSLOPE CONDITIONS WHILE KACHEMAK BAY WILL SEE RAIN SHOWERS.
MOST OF THE PRECIPITATION WILL STAY CONFINED TO THE NORTH GULF
COAST...FALLING AS RAIN BUT COULD MIX WITH OR CHANGE TO SNOW AT
HIGHER ELEVATIONS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A RIDGE ALOFT OVER SOUTHWEST ALASKA IS BRINGING FAIRLY QUIET
WEATHER TO THE AREA TODAY. THE MAIN CONCERN AND FORECAST CHALLENGE
IS THE FOG AND LOW STRATUS DRIFTING AROUND THE AREA FOLLOWING THE
WARM ADVECTION AND PRECIPITATION WHICH OCCURRED YESTERDAY. WITH
CONTINUED STABLE CONDITIONS AND SOUTHEASTERLY FLOW...IMPROVEMENT
WILL BE FAIRLY GRADUAL BUT SHOULD SEE AREAS OF FOG BECOMING MORE
PATCHY AND TRANSITIONING MORE TO STRATUS TONIGHT AND TOMORROW
MORNING. THINGS SHOULD CLEAR MORE RAPIDLY OUT SUNDAY AFTERNOON
THROUGH SUNDAY NIGHT AS EASTERLY WINDS ALOFT AND NORTHEAST
OFFSHORE SURFACE WINDS BEGIN TO INCREASE MORE SUBSTANTIALLY IN
RESPONSE TO A SURFACE LOW TRACKING TOWARDS THE WESTERN GULF. THE
NORTHEASTERLY GRADIENT TIGHTENS FURTHER ON MONDAY WITH SURFACE
WINDS CONTINUING TO BUILD PARTICULAR THROUGH AND DOWNWIND OF
CHANNELED TERRAIN. ALSO MIDDAY A BROAD FRONT WILL REACH THE ALASKA
PENINSULA THEN BEGIN TO SPREAD PRECIPITATION FURTHER INTO
SOUTHWEST ALASKA MONDAY AFTERNOON AND EVENING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE CURRENT FRONTAL SYSTEM STRETCHING ALONG THE ALEUTIANS WILL
LIFT SLOWLY NORTH AS THE PARENT LOW TO THE SOUTH OF THE DRIFTS TO
THE WEST NORTHWEST TONIGHT. THE FRONTAL SYSTEM WILL CONTINUE NORTH
INTO THE BERING AND WEAKEN SUNDAY AND SUNDAY NIGHT AS THE PARENT
LOW CURVES TO THE SOUTHWEST AS IT BECOMES VERTICALLY STACKED WITH
THE UPPER LOW. THE LOW WILL REMAIN TO THE SOUTH OF THE WESTERN
ALEUTIANS THROUGH MONDAY WITH A SECOND WRAP OF THE FRONT ROTATING
UP TOWARDS SHEMYA ON MONDAY AND BRINGING ANOTHER ROUND OF GALES.
WINDS IN THE EASTERN ALEUTIANS WILL PICK UP OUT OF THE NORTH TO
NORTHEAST ON MONDAY AS THE LARGE LOW MOVES INTO THE WESTERN GULF.

&&

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

WITH VERY LITTLE CHANGE IN THE FLOW PATTERN OVER THE SOUTHERN
MAINLAND THROUGH EARLY NEXT WEEK...THERE IS INCREASING CONFIDENCE
THAT A SLOW MOVING/DEEPENING NORTH PACIFIC LOW SOUTH OF THE
AKPEN WILL BRING GALE FORCE WINDS TO THE GULF MONDAY AFTERNOON. HEAVY
RAIN AND GUSTY WINDS APPEAR LIKELY FROM THIS SYSTEM FOR KODIAK
ISLAND AND NORTHERN GULF COAST. PRECIPITATION WILL THEN SPREAD
TOWARDS THE SOUTHWEST MAINLAND AND INTERIOR SOUTHCENTRAL BY EARLY
TUESDAY...HOWEVER WARMER AIR ALOFT WILL LIKELY BE SUFFICIENT
ENOUGH FOR THIS PRECIPITATION TO FALL AS RAIN (WITH A POSSIBILITY
OF FREEZING RAIN).

SAME BASIC PATTERN CONTINUES THEREAFTER...WITH A STRONG ZONAL JET
REMAINING JUST SOUTH OF 40N AND A PERSISTENT BLOCKING RIDGE OVER
THE WEST COAST OF NORTH AMERICA EXTENDING ACROSS NORTHERN ALASKA.
LITTLE CHANGES ARE 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 MOSTLY SOUTH AND WEST OF
THE SOUTHCENTRAL MAINLAND. SEVERAL OF THE LOWS WILL TURN NORTH
AND MOVE INTO THE GULF OF ALASKA AS THEY FILL THEN DISSIPATE.
GIVEN THAT THESE SYSTEMS WILL ALL BE WEAKENING AS THEY LIFT
NORTHWARD...THEY WILL PRIMARILY BRING PRECIPITATION TO COASTAL
AREAS AND OCCASIONALLY FURTHER INLAND WITH TEMPERATURES CONTINUING
TO REMAIN ABOVE NORMAL.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 131 138 150 155 172 174 175 176 177 178.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...AD
SOUTHCENTRAL ALASKA...MTL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JER
LONG TERM...TP