Small Craft Advisory 57, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
525 AM AKST MON JAN 19 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL CLOSED LOW POSITIONED OVER THE BERING
STRAIT WITH AN ASSOCIATED TROUGH EXTENDING TO THE SOUTHWEST JUST
NORTHWEST OF THE WESTERN ALEUTIANS. THIS IS REFLECTED AT THE
SURFACE WITH A WEAK LOW JUST SOUTH OF SAINT LAWRENCE ISLAND AND A
SECOND WEAK LOW JUST NORTH OF SHEMYA. THE 300 MB IS SHOWING A 90
KNOT ZONAL JET STREAK LOCATED OVER THE WESTERN TO CENTRAL BERING
SEA THIS MORNING. THE SOUTHCENTRAL ALASKA REGION EXTENDING SOUTH
IN THE WESTERN GULF IS AN UPPER LEVEL RIDGE. THE SATELLITE IMAGERY
IS SHOWING MOSTLY STRATUS IN THE GULF. THE SPORT MODIS NIGHTTIME
MICROPHYSICS IMAGERY WAS PICKING UP THE LOW STRATUS AND FOG IN THE
COPPER RIVER BASIN. THIS COINCIDES WITH THE SURFACE OBSERVATIONS
IN THE AFOREMENTIONED REGION. THE EASTERN GULF AT 500 MB IS
SHOWING A CLOSED LOW LOCATED OFF THE COAST NEAR SITKA. THE
SURFACE ANALYSIS IS SHOWING A WEAK LOW JUST SOUTHWEST OF SITKA
WITH THE ASCAT SCATTEROMETER WINDS SHOWING UPPER END SMALL CRAFT
ADVISORY WINDS WITH THIS SYSTEM. THE OTHER KEY FEATURE IS AN
UPPER LEVEL TROUGH OVER THE EASTERN ALEUTIANS NEAR COLD BAY. THE
SATELLITE IMAGERY IS SHOWING AN AREA OF LOW CLOUDS ASSOCIATED WITH
THIS TROUGH AND THE WATER VAPOR SATELLITE HAS THE BACK EDGE OF
THE TROUGH JUST EAST OF COLD BAY THIS MORNING.

&&

.MODEL DISCUSSION...
THE MODELS HAVE SOME UNCERTAINTY WITH A NORTH PACIFIC LOW ENTERING
THE GULF BY TUESDAY MORNING. THE NAM/GFS MODELS TRACK THE LOW
FARTHER EAST IN THE EASTERN GULF. WHILE...THE GEM-REG/EC MODELS
TRACK THE LOW MORE TOWARDS THE WEST INTO THE MIDDLE OF THE GULF.
THIS LOW PRESSURE SYSTEM THEN MOVES INLAND BY TUESDAY EVENING. THE
MODELS ARE STRUGGLING WITH THE COMPLEX NORTH PACIFIC LOW APPROACHING
THE CENTRAL TO EASTERN ALEUTIANS. THE EC MODEL SEEMS TO HAVE HAD
BETTER RUN-TO-RUN CONSISTENCY WITH THIS COMPLEX LOW PRESSURE
SYSTEM. THE FORECAST CONFIDENCE REMAINS BELOW AVERAGE DUE TO THE
UNCERTAINTY WITH TIMING AND LOCATION OF SYNOPTIC SYSTEMS.

&&

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

A SHORT WAVE LIFTING NORTHEAST ACROSS SOUTHCENTRAL TONIGHT WILL
BRING INCREASED CHANGES FOR LIGHT SNOW ACROSS COOK INLET...MAT-
SU...AND THE KENAI PEN WITH A MIXTURE ALONG THE NORTH GULF COAST.
GENERAL OFFSHORE FLOW SETS UP AFTER THE PASSAGE OF THE SHORT WAVE
ON TUE. THIS WILL LEAD TO DECREASING CLOUDS...HOWEVER SOME LOW
CLOUDS AND FOG MAY REFORM OVER THE COPPER RIVER BASIN TUE NIGHT.
PRESSURE GRADIENTS WILL ALSO BUILD IN THE WAKE OF THE WAVE AND
GIVE RISE TO BRISK OUTFLOW WINDS ACROSS THE NORTH GULF AND EASTERN
KENAI PENINSULA TUE AND TUE NIGHT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
WEAK HIGH PRESSURE WILL BUILD OVER THE REGION...WHICH WILL KEEP
MOST LOCATIONS DRY THROUGH TUESDAY. THE EXCEPTION WILL BE A WEAK
SURFACE CIRCULATION DISSIPATING AS IT MOVES OVER KODIAK ISLAND
TONIGHT...BRINGING SOME SNOW SHOWERS NEAR THE ALASKA AND ALEUTIAN
RANGES THROUGH TUESDAY. OTHERWISE...COLDER TEMPERATURES AND
OFFSHORE FLOW WILL CONTINUE TO DOMINATE THE SOUTHWEST MAINLAND
THROUGH MID WEEK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A WEAKENING FRONTAL ZONE BRINGING SNOW SHOWERS AND GUSTY WINDS TO
THE PRIBILOF ISLANDS THIS MORNING...WILL CONTINUE TO TRACK
INTO THE NORTHERN BERING AND DISSIPATE TUESDAY. OTHERWISE...RATHER
QUIESCENT WEATHER FOR THE BERING SEA WILL BE THE DOMINANT MODE AS
WEAK HIGH PRESSURE ALOFT BUILDS OVER THE BERING MONDAY INTO
TUESDAY. NEAR GALE FORCE EASTERLY WINDS AND SHOWERY CONDITIONS
WILL DEVELOP ACROSS THE ALEUTIAN CHAIN TUESDAY AS A NORTH PACIFIC
FRONT MOVES APPROACHES THE AREA.

&&

.LONG TERM FORECAST (WEDNESDAY THROUGH SUNDAY)...
THE MAJOR PLAYERS IN THE EXTENDED FORECAST REMAIN MUCH THE SAME. A
LARGE COMPLEX STACKED LOW CENTER SITS JUST SOUTH OF THE ALEUTIANS
WITH A BAROCLINIC ZONE STRETCHING NORTHEASTWARD INTO THE GULF.
THESE FEATURES WILL BE THE FOCUS FOR ACTIVE WEATHER IN THE COMING
WEEK. LIGHT WINDS AND NEAR SEASONABLE TEMPERATURES WILL HANG
AROUND WEDNESDAY WHEN THE AFOREMENTIONED FRONT WILL SWING OVER THE
COASTAL MOUNTAINS AND PUSH ONTO THE MAINLAND ON THURSDAY. BEYOND
THAT TIME PERIOD MODEL GUIDANCE DIFFERS ON HOW TO HANDLE THESE
FEATURES AS WELL AS A LINGERING UPPER LOW PRESSURE TO THE NORTH.
IT APPEARS HOWEVER THAT A MORE ACTIVE WEATHER REGIME WILL SET UP
AND CONTINUE FOR THE WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY 185.
         GALE 155 172 173 174 175 176 177.
FIRE WEATHER...NONE.

&&

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