Small Craft Advisory 896, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
448 PM AKST WED NOV 11 2015

.ANALYSIS AND UPPER LEVELS...
THE DEEP LOW THAT BROUGHT HURRICANE FORCE WINDS TO THE EASTERN
BERING/ALEUTIANS THIS MORNING IS MOVING OVER THE ALASKA
PENINSULA ON ITS WAY INTO THE GULF. THE JET CAN STILL BE SEEN
RIDING ALONG THE SOUTHERN EDGE OF THIS LOW OVER THE NORTH
PACIFIC...AND HAS WEAKENED SOMEWHAT IN THE LAST 12 HOURS TO 130
KTS. TO THE EAST OF THIS LOW A FRONT HAS MOVED THROUGH KODIAK
ISLAND AND IS CONTINUING TO STRENGTHEN TO STORM FORCE AS IT
PROGRESSES TOWARDS THE NORTH GULF COAST THIS EVENING. TO THE WEST
OF THE BERING LOW...A SHORT WAVE ASSOCIATE WITH ANOTHER WEAKER
LOW MOVING THROUGH THE EXTREME NORTHERN BERING CAN BE SEEN
STRETCHING FROM SAINT MATTHEW ISLAND...THROUGH THE PRIBILOFS AND
NEARLY TO THE EASTERN ALEUTIANS. EVEN FURTHER TO THE WEST
WIDESPREAD COLD AIR ADVECTION IS PRESENT WITHIN THE NORTHERLY FLOW
OVER THE CENTRAL AND WESTERN BERING...AS INSTABILITY RAIN/SNOW
SHOWERS DEVELOP OVER THE STILL RELATIVELY WARM WATERS OF THE
BERING SEA.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN GOOD AGREEMENT WITH THE MAJOR SYNOPTIC
FEATURES THROUGH THE SHORT TERM...ESPECIALLY WITH REGARDS TO THE
STRENGTH AND TIMING OF THE FRONT AND ASSOCIATED LOW MOVING INTO
THE GULF THIS EVENING. THERE IS SOME DISAGREEMENT IN HOW LONG A
DEVELOPING DEFORMATION BAND SETTING UP OVER WESTERN BRISTOL BAY
THIS EVENING WILL PERSIST...WHICH IS RESULTING IN LOWER CONFIDENCE
IN THE SNOW FORECAST FOR THE DILLINGHAM AREA THIS EVENING. THE
GLOBAL GFS/EC STALL THIS FEATURE MORE THAN THE HIGHER RESOLUTION
NAM/GEM REGIONAL...RESULTING IN SNOWFALL THAT COULD PERSIST INTO
THE EARLY MORNING HOURS. BY LATE IN THE WORK WEEK THERE ARE ALSO
SOME MINOR DIFFERENCES WITH THE EXACT PLACEMENT AND INTENSITY OF
THE LOW CURRENTLY MOVING INTO THE GULF...BUT THIS IS LARGELY OUT
OF THE AOR AND SHOULD NOT HAVE AN SIGNIFICANT IMPACT IN FORECAST
CONFIDENCE FOR OUTFLOW WINDS AND COLDER TEMPERATURES DEVELOPING AT
THAT TIME.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

A STRONG STORM FORCE LOW IS RAPIDLY MOVING INTO THE GULF OF
ALASKA THIS EVENING...BRINGING RAIN AND SNOW TO COASTAL LOCATIONS
ALONG WITH STORM FORCE WINDS TO THE NORTHERN GULF COAST INTO
SOUTHERN COOK INLET. SNOW WILL BE HEAVY AT TIMES THROUGH WHITTIER
AND INTO PORTAGE VALLEY...WITH MUCH LOWER AMOUNTS OVER EASTERN
PRINCE WILLIAM SOUND DUE TO THE STRONG EASTERLY FLOW. INTERIOR
LOCATIONS WILL SEE A STRONG DOWNSLOPE SHADOW. AS THIS POWERFUL LOW
TRACKS EAST TOMORROW...WINDS WILL RAPIDLY BECOME OUTFLOW ACROSS
THE REGION...WITH PRECIPITATION ENDING AND OFFSHORE WINDS RAMPING
UP QUICKLY TONIGHT AND LASTING INTO THE WEEKEND. THE COMBINATION
OF COLD AIR ADVECTION AND A TIGHT PRESSURE GRADIENT WILL FAVOR
ALL GAPS...INCLUDING INLAND GAPS SUCH AS THE MATANUSKA VALLEY AND
DOWN TURNAGAIN ARM. TEMPERATURES WILL COOL THROUGH THE REST OF
THE FORECAST PERIOD AS COLD AIR FILTERS IN...AND SKIES CLEAR OUT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

THE STRONGEST WINDS ACROSS THE ALASKA PENINSULA PEAK THIS EVENING
AND THEN BEGIN A DOWNWARD TREND AS THE SURFACE LOW TRACKS INTO THE
SOUTHERN GULF. PRECIPITATION TONIGHT WILL MAINLY BE SNOW ACROSS
THE SOUTHWEST MAINLAND WITH SCATTERED RAIN SHOWERS DURING THE
EVENING NEAR THE ALEUTIAN RANGE AND ALASKA PENINSULA. SNOW AMOUNTS
WERE SLIGHTLY INCREASED ACROSS BRISTOL BAY...NORTH AND WEST OF
KING SALMON...ALONG A DEFORMATION ZONE THAT FORMED THIS AFTERNOON
BETWEEN A WARM MOIST AIR MASS ACROSS EASTERN BRISTOL BAY AND COLD
AIR TO THE WEST. NORTHERLY FLOW TAKES OVER LATE TONIGHT AND
ADVECTS A COLDER AND DRIER CONDITIONS INTO THE SOUTHWESTERN AND
ALASKA PENINSULA THROUGH FRIDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A PERSISTENT PATTERN UNDER NORTH TO WESTERLY FLOW ENSUES FOR THE
END OF THE WEEK WITH LOW PRESSURE IN THE GULF AND RIDGING IN THE
NORTHERN PACIFIC. COLDER AIR ADVECTS THROUGH THE BERING AND KEEPS
SHOWERY PRECIPITATION ALL SNOW.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE MODELS ARE IN GOOD AGREEMENT WITH THE STORM FORCE LOW AS IT
FILLS AND BECOMES ALMOST STATIONARY NEAR YAKUTAT IN THE NORTHERN
GULF THROUGH SATURDAY. THIS SYSTEM WILL GET PHASED INTO A SECONDARY
LOW PRESSURE SYSTEM THAT WILL ENTER THE WESTERN GULF BY SUNDAY.
THE MAJORITY OF THE PRECIPITATION WILL REMAIN ALONG THE NORTHERN
GULF COASTAL MARINE AREAS WITH SOME MOISTURE MAKING IT INTO THE
INTERIOR. THE BIGGEST CHANGE HEADING INTO THE WEEKEND WILL BE THE
COOLER TEMPERATURES FOR THE ANCHORAGE BOWL AND THE COPPER RIVER
BASIN THROUGH THE EARLY PART OF NEXT WEEK. TEMPERATURES WILL DROP
BELOW ZERO DEGREES IN MAJORITY OF THE SOUTHCENTRAL REGION DUE TO
THE COLD AIR ADVECTION AND THE NORTHERLY WINDS. LOOK FOR THE
COLDEST TEMPERATURES IN THE MAT-SU VALLEYS AND THE COPPER RIVER
BASIN.

ON THE BERING SEA THE MODELS ARE IN DISAGREEMENT WITH NEXT
WEATHER SYSTEM ENTERING THE NORTHERN BERING SEA FROM THE KAMCHATKA
PENINSULA BY FRIDAY. THE GFS TRACKS THIS LOW NEAR SAINT LAWRENCE
ISLAND AND THE NAM/ECMWF MODELS TRACK THIS SYSTEM NEAR THE PRIBILOF
ISLANDS HEADING INTO THE WEEKEND. THEREFORE...THE FORECAST
CONFIDENCE IS LOW DUE TO TIMING AND PLACEMENT DISCREPANCIES BEFORE
MOVING INTO THE GULF BY SUNDAY. THIS SYNOPTIC FEATURE WILL PULL
DOWN MORE COLD AIR FROM THE NORTH RESULTING IN A CONTINUED
SHOWERY WEATHER REGIME. BY MONDAY EVENING ANOTHER WEATHER SYSTEM
WILL DROP OFF THE KAMCHATKA PENINSULA BEFORE ENTERING THE WESTERN
BERING SEA. THIS WILL BE ACCOMPANIED BY WIDESPREAD RAIN IN THE
LOWER BERING SEA BEFORE TRANSITIONING ALL SNOW AS IT TRACKS TO THE
NORTHERN BERING BY TUESDAY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING 181
MARINE...HURRICANE FORCE 155
         STORMS 119 121 130 139 150 165 352 414
         GALES 125 127 132 138 141 170 171 172 351 413 129.

&&

SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHCENTRAL ALASKA...JA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...PD