Small Craft Advisory 107, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
507 AM AKST SUN JAN 31 2016

.ANALYSIS AND UPPER LEVELS...

THE BROAD MULTI-CENTER LOW REMAINS OVER THE BERING AND ALEUTIANS
WITH AN AMPLIFYING RIDGE STRETCHING FROM THE CENTRAL GULF NORTH
AND INLAND THROUGH SOUTH CENTRAL AND INTERIOR ALASKA. A VARIETY OF
SMALLER LOW PRESSURE CIRCULATIONS...TROUGHS AND FRONTAL WAVES
CONTINUE TO SPIN AROUND THE LARGER LOW. THE NORTHERN MOST
CIRCULATION IS UP NEAR 60N AND 180 WITH SEVERAL TROUGHS SWINGING
THROUGH THE ALEUTIAN BRINGING WITH THEM AREAS OF MORE ORGANIZED
SHOWERS. A SECONDARY WRAP AROUND LOW IN THE CENTRAL BERING RUNS
JUST TO THE WEST OF THE PRIBILOF ISLANDS BRINGING ANOTHER ROUND OF
SNOW SHOWERS.

THE MAIN FRONTAL SYSTEM ASSOCIATED WITH THE LARGE BERING LOW
STRETCHES ACROSS THE EASTERN BERING...ALASKA PENINSULA AND INTO
THE NORTH PACIFIC AND IS CURRENTLY PUSHING ONSHORE INTO SOUTHWEST
ALASKA BRINGING WINDY CONDITIONS WITH IT. FURTHER TO THE EAST
HIGH PRESSURE PREVAILS WITH THE LOCATIONS OF PATCHY DENSE FOG AND
LOW STRATUS BEING THE MAIN CHALLENGE FOR THE NIGHT.

&&

.MODEL DISCUSSION...

MODELS ARE CURRENTLY IN FAIR AGREEMENT WITH REGARDS TO THE
POSITION OF THE LARGE SCALE LOW IN THE BERING AND THE RIDGE IN
GULF. HOWEVER...THEY ARE MORE CHALLENGED BY THE NUMBER AND
COMPLEXITY OF SMALLER SCALE CIRCULATIONS ROTATING AROUND THE LOW.
ONE FEATURE OF PARTICULAR CONCERN IS THE FRONTAL WAVE BEGINNING TO
SPIN UP SOUTH OF THE ALASKA PENINSULA. THE NAM...EC AND CANADIAN
MODELS SPIN THIS UP INTO A CLOSED SURFACE LOW WHILE THE GFS DOES
NOT APPEAR TO BE PICKING UP ON IT VERY WELL. IMPLICATIONS TO THE
FORECAST INCLUDE A SLOWING OF THE MAIN FRONTAL SYSTEMS PROGRESSION
EASTWARD AS THE NEW LOW LIFTING NORTH UP THE FRONT.

THE NEXT POINT OF MODEL DISAGREEMENT IS WITH REGARDS TO THE TROUGH
OR SURFACE LOW MOVING NORTH THROUGH THE WESTERN GULF ON MONDAY.
THE NAM LOOKS TO BE THE OUTLIER DEVELOPING THE LOW INTO A CLOSED
SURFACE LOW WHILE THE OTHER MODELS KEEP IT AN OPEN TROUGH. FURTHER
OUT IN TIME...THE MODELS ARE COMING INTO BETTER AGREEMENT ON THE
POSITION OF THE NEXT BIGGER SURFACE LOW LIFTING NORTH OUT OF THE
NORTH PACIFIC EARLY NEXT WEEK AS WELL AS TRENDING IT STRONGER.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
WITH THE EXCEPTION OF THE COPPER RIVER BASIN...INCREASED
NORTHERLY FLOW DEVELOPING ACROSS SOUTHCENTRAL THIS AFTERNOON WILL
END THE FOG THREAT FOR THE NEXT DAY OR SO. THAT SAID...THERE IS
STILL DENSE FOG POTENTIAL IN THE ANCHORAGE BOWL (KNIK ARM SOURCE
REGION) THIS MORNING.

A BROAD RIDGE ACROSS SOUTHCENTRAL/GULF WILL SLOWLY WEAKEN AND
DRIFT EAST AND WEAKEN THROUGH MON. THIS WILL ALLOW UPPER SHORT
WAVES AND SURFACE FEATURES (FRONTS/LOWS) TO PUSH FURTHER
NORTH...INCREASING THE CHANCES FOR PRECIPITATION AND STRONG WINDS
THROUGH MON NIGHT MAINLY ACROSS COASTAL LOCATIONS. A STRONG
SURFACE LOW OVER THE NORTHEAST PACIFIC MOVES NORTH INTO BRISTOL
BAY THIS EVENING. THIS SYSTEM AND ITS ASSOCIATED FRONTAL TROUGH
WILL BRING GALES TO THE WESTERN AND CENTRAL GULF THIS MORNING
WHICH WILL THEN PUSH SLOWLY NORTH TONIGHT AND MON. MARGINAL GALE
CONDITIONS MAY LINGER ON IN THE NORTHERN GULF MARINES MON
NIGHT...DEPENDING ON INTENSITY OF A NORTH MOVING FRONTAL WAVE.
RAIN IS EXPECTED TO IMPACT KODIAK ISLAND TODAY...WITH SNOW OR MIX
REACHING THE SOUTHERN KENAI LATER THIS MORNING. COASTAL AREAS OF
THE KENAI WILL LIKELY SEE SOME MIXED PRECIPITATION TYPES WITH
INLAND AREAS OF THE EASTERN KENAI PEN GENERALLY SNOW. AREAS TO THE
LEE (WEST) OF THE CHUGACH/KENAI MOUNTAINS WILL BE LARGELY ON THE
DRY SIDE DUE TO DOWNSLOPE (SE CROSS BARRIER FLOW).

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A FRONTAL BOUNDARY IS IN THE PROCESS OF STALLING OUT OVER THE
MAINLAND. THE TIGHT PRESSURE GRADIENT AHEAD OF THE SYSTEM WILL
CONTINUE TO BRING STRONG WIND TO THE BRISTOL BAY AREA WHILE WINDS WILL
SLACKEN SOMEWHAT OVER THE KUSKOKWIM DELTA TODAY. STRONG CROSS-BARRIER
FLOW WILL KEEP MOST AREAS ON THE DRY SIDE ALTHOUGH SOME SPRINKLES
ARE POSSIBLE. HOWEVER THE COASTAL AREAS OF THE KUSKOKWIM DELTA
WILL SEE STEADIER RAIN...MIXED WITH SNOW AT TIMES. UPSLOPE AREAS
OF THE AHKLUN MOUNTAINS WILL EXPERIENCE STEADIER RAIN AS WELL.
THIS AFTERNOON A SHORTWAVE MARCHING NORTH IN THE PACIFIC ALONG THE
FRONT WILL GIVE THE BOUNDARY A NUDGE...SHIFTING INLAND BY THE
OVERNIGHT HOURS TONIGHT...BRINGING AREAS OF RAIN TO THE NORTH OF
DILLINGHAM AND WEST OF ILIAMNA. ONCE THE WINDS BEGIN TO WANE
OVERNIGHT TOWARD MORNING FOR INTERIOR BRISTOL BAY PRECIPITATION
SHOULD TURN FROM RAIN TO SNOW. UNCERTAINTY WITH THIS FRONT IS
LARGER THAN NORMAL WITH SOME GUIDANCE STALLING THE FRONT IN ONE
PLACE AND OTHERS SLOWLY MOVING IT EASTWARD. IF THE BAND SITS IN
ONE PLACE FOR TOO LONG...SNOW ACCUMULATION COULD PILE UP PRETTY
QUICKLY...HOWEVER THIS IS A LOW CONFIDENCE SOLUTION AT THIS POINT.
OTHERWISE THE MAINLAND WILL BE CHARACTERIZED BY DECREASING
CLOUDS/WINDS...AND FALLING TEMPERATURES FROM THE RECENT WARM
SPELL.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A SHOWERY PATTERN CONTINUES FOR MUCH OF THE BERING AS A MATURE
SYSTEM SPINS OVERHEAD. VERY COLD UPPER LEVEL TEMPERATURES ARE PROMOTING
MARGINAL CONVECTIVE INSTABILITY OVER THE CENTRAL BERING SEA...WITH AN
ISOLATED LIGHTNING STRIKE POSSIBLE TODAY AS THIS AREA SHIFTS
TOWARD UNALASKA. COVERAGE OF SHOWERS SHOULD DECREASE THROUGH
MONDAY AS THE RESPONSIBLE LOW PRESSURE SYSTEM MOVES NORTHWARD OUT
OF THE AREA.

&&

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

ANOTHER STRONG LOW APPROACHES THE AKPEN AND KODIAK FROM THE SOUTH
TUESDAY AND PUSHES A FRONT TO THE SOUTHERN MAINLAND THROUGH
WEDNESDAY AND THURSDAY. A TRAIN OF SYSTEMS CONTINUES THEREAFTER
THROUGH THE REMAINDER OF THE WEEK...SETTING UP AN ACTIVE PATTERN
FOR THE SOUTHERN MAINLAND THROUGH NEXT WEEKEND.

PRECIPITATION-TYPE WILL BE THE PRIMARY CONCERN FOR MUCH OF
SOUTHERN ALASKA...WITH THE POTENTIAL FOR LIQUID PRECIPITATION AS
FAR NORTH AS ANCHORAGE AT TIMES WITH CONTINUED WARM
TEMPERATURES. WINDS TO GALE-FORCE AND PERHAPS TO STORM-FORCE WITH
POTENTIAL BARRIER JET FORMATION WILL BE THE MAIN CONCERN FOR NORTH GULF
COASTAL LOCATIONS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 120 130-132 136-139 150 155 160 175 177 179-181 185 351
         352 411-414.
         HEAVY FREEZING SPRAY 185.

&&

SYNOPSIS AND MODEL DISCUSSION...JR
SOUTHCENTRAL ALASKA...BC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...CC