Small Craft Advisory 118, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
435 PM AKST FRI FEB 6 2015

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL RIDGE IS NOW CENTERED OVER THE NORTHWEST BERING
SEA AS THE UPPER LEVEL TROUGH HAS DESCENDED OUT OF THE
ARCTIC...ALONG THE ALCAN BORDER...AND THEN INTO THE NORTHERN GULF
OF ALASKA. THIS IS MOVING THE TIGHTER GRADIENT ALOFT (WHICH SET
OFF THE HIGH WINDS IN SOUTHCENTRAL ALASKA) TO THE WEST. WINDS
WILL INCREASE OVER SOUTHWEST ALASKA AS A RESULT. AN UPPER LEVEL
SHORT WAVE EMBEDDED IN THIS STRONGER GRADIENT IS NEAR THE BROOKS
RANGE THIS AFTERNOON BUT WILL MOVE QUICKLY SOUTHWARD OVER THE
SOUTHWEST MAINLAND TONIGHT. THE SURFACE PATTERN REMAINS LARGELY
UNCHANGED FROM THE PAST FEW DAYS WITH HIGH PRESSURE OVER THE
NORTHERN BERING SEA AND THE INTERIOR OF THE STATE WITH LOWER
PRESSURE IN THE SOUTHEAST GULF OF ALASKA. THE PRESSURE GRADIENT
ALONG THE NORTH GULF COAST REMAINS EXTREMELY TIGHT AND COMBINED
WITH THE UPPER LEVEL SUPPORT AND COLD AIR ADVECTING OVER THE AREA
FROM THE INLAND AREAS CAUSED THE WARNING-LEVEL HIGH WINDS IN THE
MATANUSKA VALLEY AND VALDEZ AREA.

&&

.MODEL DISCUSSION...
MODELS REMAIN IN VERY GOOD SYNOPTIC AGREEMENT WITH THE COMPLEX LOW
DEVELOPMENT IN THE GULF OF ALASKA BEING THE ONLY DIFFERENCE OF
NOTE. AS HAS BEEN DISCUSSED THE PAST FEW DAYS THE NAM HAS BEEN THE
MOST AGGRESSIVE IN DEVELOPING A STRONGER LOW THAT BEARS DOWN ON
KODIAK ISLAND TOMORROW NIGHT. THE OTHER MODELS ARE ALSO SHOWING A
SOLUTION THAT IS MORE IN THIS DIRECTION WITH EACH RUN. WHILE SUCH
LOWS ARE DYNAMIC AND CAN CHANGE RAPIDLY THE OVERALL IDEA OF IT
BRINGING SOME SIGNIFICANT WINDS AND SNOWFALL TO KODIAK ISLAND
PERHAPS AS EARLY AS LATE SATURDAY AFTERNOON IS BECOMING MORE
LIKELY.

&&
.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)...

NORTHERLY WINDS HAVE LARGELY PEAKED AND ARE BEGINNING A VERY
GRADUAL DOWNWARD TREND AS UPPER LEVEL FORCING BEGINS TO TRANSITION
WEST TO THE SOUTHWEST MAINLAND. HOWEVER...LOCALLY STRONG GUSTS
CAPABLE OF MINOR PROPERTY DAMAGE OR ISOLATED POWER OUTAGES ARE
STILL POSSIBLE THROUGH THIS EVENING PARTICULARLY WHERE WARNINGS
REMAIN ACTIVE. WINDS WILL CONTINUE THROUGH THE WEEKEND BUT SLOWLY
SUBSIDE IN MOST AREAS.

THE ONE EXCEPTION WILL BE ALONG THE NORTHERN GULF OF ALASKA
THROUGH THE BARREN ISLANDS REGION AS WELL AS SHELIKOF
STRAIT...WHERE A DEVELOPING LOW OVER THE CENTRAL GULF WILL MOVE
WEST AND BECOME STATIONARY JUST SOUTH TO SOUTHEAST OF KODIAK
ISLAND. THIS WILL ALLOW FOR COLD AIR JUST TO THE NORTH AND WEST TO
MOVE TOWARD THE LOW WHILE JUST ALOFT STRONG INSTABILITY AND
MOISTURE WILL ADVECT ACROSS THE ISLAND. THE RESULT WILL BE THE
POTENTIAL FOR WIDESPREAD BLIZZARD CONDITIONS ACROSS MUCH OF THE
ISLAND...PARTICULARLY SATURDAY NIGHT.

CONDITIONS SHOULD GRADUALLY IMPROVE INTO SUNDAY AS WARMER
TEMPERATURES BEGIN TO MOVE INTO THE AREA FROM THE
EAST...ESPECIALLY NEAR KODIAK CITY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...SATURDAY AND
SUNDAY)...THE BIG STORY FOR THE NEXT FEW DAYS WILL BE THE COLD AND
THE WIND. NORTHEAST WINDS ARE ALREADY STARTING TO INCREASE ACROSS
MUCH OF THE KUSKOKWIM DELTA AND BRISTOL BAY AREA. THESE WINDS
SHOULD ONLY CONTINUE TO INCREASE TONIGHT AND SATURDAY AS YET
ANOTHER REINFORCING SHOT OF COLD AIR PLOWS THROUGH THE AREA. THERE
IS ALSO SOME UPPER LEVEL SUPPORT PROGGED TO MOVE THROUGH THE AREA
TOMORROW MORNING THAT SHOULD HELP TO REALLY ADD TO THE DOWNWARD
MOMENTUM. THUS...ANY INVERSIONS THAT ARE HOLDING ON...SUCH AS IN
PARTS OF THE KUSKOKWIM VALLEY WHERE WINDS REMAIN LIGHT...WILL
FINALLY ALLOW THESE STRONGER WINDS TO MIX DOWN TO THE SURFACE.
INITIALLY THIS MAY ACTUALLY BRING TEMPERATURES UP A FEW DEGREES AS
SOME OF THE WARM AIR TRAPPED IN THE INVERSION GETS MIXED OUT. BUT
AFTER THAT INITIAL WARM BURST...COLDER TEMPERATURES WILL MOVE IN
FROM THE ARCTIC. WINDS WILL CONTINUE TO BLOW...AND COUPLED WITH
THIS COLD AIR...SHOULD MAKE FOR DANGEROUS WIND CHILLS FOR MUCH OF
THE WEEKEND. PLEASE SEE THE WIND CHILL ADVISORIES FOR DETAILS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...SATURDAY
AND SUNDAY)...REMARKABLY QUIET WEATHER CONTINUES ACROSS THIS AREA.
IT SEEMS THAT IT HAS BEEN DAYS UPON DAYS OF COLD DRY NORTHEAST
FLOW COMING OFF THE MAINLAND AND THEN OFF THE ICE PACK. THE FLOW
CONTINUES TO THEN PICK UP SOME MOISTURE ONCE IT HITS THE OPEN
WATERS OF THE BERING AND BRING SNOW SHOWERS TO MUCH OF THE
ALEUTIANS...ESPECIALLY ON THE BERING SIDE. A WEAK AREA OF LOW
PRESSURE WILL MOVE PARALLEL TO THE WESTERN AND CENTRAL ALEUTIANS
AS IT DRIFTS EAST OVER THE WEEKEND. THIS WILL KEEP MODERATE WINDS
ACROSS MUCH OF THE AREA AND COULD BRING IN A BIT MORE MOISTURE TO
AID IN THE SHOWER DEVELOPMENT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
MODELS CONTINUE TO BE IN GOOD AGREEMENT BIG PICTURE WISE
SUPPORTING THE IDEA OF A MAJOR PATTERN SHIFT NEXT WEEK. OFFSHORE
FLOW WILL BEGIN TO DIMINISH GRADUALLY ON MONDAY AS A WEAKENING
SURFACE LOW TRACKS INTO THE NORTHERN GULF AND THEN DISSIPATES...RELAXING
THE OFFSHORE COASTAL PRESSURE GRADIENT. SURFACE HIGH PRESSURE
INLAND AND COLD DENSE INTERIOR AIR HOWEVER WILL KEEP GUSTY
DOWNSLOPE AND GAP WINDS GOING THOUGH SLIGHTLY LIGHTER AND BECOMING
PROGRESSIVELY SHALLOWER THROUGH MIDWEEK.

A RIDGE ALOFT WILL BEGIN BUILDING OVER THE GULF OF ALASKA ON
MONDAY IN RESPONSE TO A DEEPENING NORTH PACIFIC LOW. AS THE NEW
LOW BECOMES IN PHASE WITH THE UPPER LOW OVER THE GULF IT WILL
WEAKEN AND PULL THAT FEATURE AWAY AND OUT OF THE GULF TO
CONSOLIDATE INTO A SINGLE BROAD CLOSED LOW WELL SOUTH OF THE
ALASKA PENINSULA AND ALEUTIANS. THE UPPER LEVEL RIDGE WILL
CONTINUE TO AMPLIFY MONDAY NIGHT AND TUESDAY AS IT SHIFTS EAST
OVER SOUTHEAST ALASKA AND WESTERN ALASKA WHERE IT WILL PERSIST AND
STRENGTHEN THROUGH THE END OF THE WEEK.

SOUTHERLY FLOW ALONG THE WEST SIDE OF THE RIDGE WILL BRING A
SERIES OF INCREASINGLY WARM FRONTAL SYSTEMS UP INTO THE GULF AND
SOUTHWEST AND SOUTHCENTRAL ALASKA BEGINNING TUESDAY AND CONTINUE
THROUGH AT LEAST THE END OF THE WEEK. INITIALLY THE FRONTAL
SYSTEMS WILL HAVE A HARD TIME MAKING IT PAST THE COAST AS THEY
RUN INTO THE COLD DRY OFFSHORE FLOW. HOWEVER EACH ONE WILL MAKE IT
A BIT FURTHER INLAND AND PROGRESSIVELY ERODE THE COLD AIR FROM
THE TOP DOWN MAKING FREEZING RAIN A POTENTIAL CONCERN AS EARLY
AS TUESDAY NEAR THE GULF COAST AND WEDNESDAY AND THURSDAY FURTHER
INLAND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING 111 131
         BLIZZARD WATCH 171
         WIND CHILL ADVISORY 141 152 155 161
MARINE...STORM 120 131
         GALE 119 121 132 136 137 138 139 150 155 160 165 170
         179 180 181
         HEAVY FREEZING SPRAY 121 125 129 130 138 139 140 141 150
         155 160 165 170 179 180 185
FIRE WEATHER...NONE

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MSO
LONG TERM...JER