Small Craft Advisory 119, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
432 PM AKST SAT FEB 7 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED NEAR KODIAK ISLAND WITH AN
ASSOCIATED SURFACE LOW OVER THE GULF TO THE SOUTHEAST OF KODIAK.
THERE IS AN UPPER HIGH OVER THE CENTRAL/EASTERN BERING SEA AND
EXTREME NORTHEAST SIBERIA...POSITIVELY TILTING OVER NORTHERN
ALASKA. SURFACE HIGH PRESSURE IS OVER NORTHERN AND CENTRAL
ALASKA...AND THIS COMBINED WITH THE LOW PRESSURE OVER THE GULF IS
KEEPING THE FLOW STRONGLY OFFSHORE OVER SOUTHERN ALASKA.

&&

.MODEL DISCUSSION...
THE MODELS ARE KIND OF ALL OVER THE PLACE WITH THE EXACT LOCATION
OF THE SURFACE LOW OVER THE WESTERN GULF TONIGHT. SINCE THIS HAS
A STRONG IMPACT ON THE POTENTIAL FOR BLIZZARD CONDITIONS ON
KODIAK ISLAND...IT IS FAIRLY IMPORTANT TO CHOOSE THE CORRECT
MODEL. THE NAM WAS CHOSEN FOR THE FORECAST EARLY ON DUE TO ITS
HANDLING OF CONDITIONS THROUGH THE MORNING OVER THE NORTHERN GULF.
A SECOND LOW FORMING OVER THE GULF FURTHER EAST LATE TONIGHT AND
MOVING ACROSS THE NORTHERN GULF THROUGH SUNDAY EVENING IS ALSO
CAUSING SOME MODEL ISSUES. FOR THIS LOW SIDED AGAIN WITH THE
NAM...POSSIBLY BLENDED WITH SOME GFS...BUT WITH LOWER CONFIDENCE.
AFTER THIS (LATE SUNDAY NIGHT THROUGH MONDAY NIGHT) THE MODELS
STILL DIFFER...BUT THE IMPACTS ON THE FORECAST ARE MINOR.

&&

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

THE GUSTY WINDS THAT HAVE BEEN OCCURRING FROM THE MATANUSKA
VALLEY INTO PORTIONS OF THE ANCHORAGE BOWL OVER THE PAST FEW DAYS
WILL CONTINUE TO GRADUALLY DIMINISH THROUGH LATE TONIGHT. THIS
WILL BE ESPECIALLY APPARENT OVER WEST ANCHORAGE WHERE THE
DIMINISHING WINDS SHOULD ALLOW TEMPERATURES OVERNIGHT TONIGHT TO
FALL BACK INTO THE SINGLE DIGITS. WINDS OUT OF THE MATANUSKA
VALLEY HOWEVER WILL REMAIN GUSTY INTO MONDAY MORNING AS ANOTHER
ROUND OF COLD AIR DUMPS INTO IN THE COPPER RIVER
BASIN...PREVENTING THESE WINDS FROM DIMINISHING VERY QUICKLY.

THE STORM FORCE LOW CURRENTLY MOVING THROUGH THE WESTERN GULF WILL
BRING ANOTHER ROUND OF LIGHT ACCUMULATING SNOW TO THE SOUTHERN
KENAI PENINSULA...THEN BRING BLIZZARD CONDITIONS INTO KODIAK
ISLAND AS THE SYSTEM MOVES TO THE SOUTHWEST. IT DOES NOT APPEAR
THAT BLIZZARD CONDITIONS WILL ENCOMPASS ALL OF THE
ISLAND...LARGELY DUE TO LITTLE OR NO PRE-EXISTING SNOWPACK.
HOWEVER...CONFIDENCE IS GOOD THAT WHERE HEAVIEST SNOWFALL OCCURS
BLIZZARD CONDITIONS WILL ALSO EXIST.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE COLD ARCTIC AIR COMBINED WITH GUSTY NORTHERLY WINDS WILL
REMAIN THROUGH THE WEEKEND. THEREFORE...THE WIND CHILL ADVISORIES
WILL REMAIN IN EFFECT ACROSS THE KUSKOKWIM DELTA...THE LOWER
KUSKOKWIM VALLEY AND THE BRISTOL BAY REGION. BY SUNDAY EVENING THE
WINDS WILL HAVE WEAKENED AND THE TEMPERATURES WILL WARM ENOUGH TO
RISE ABOVE WIND CHILL ADVISORY LEVELS. BY MONDAY AN UPPER LEVEL
RIDGE WILL BUILD INTO THE SOUTHERN ALASKA PENINSULA FROM THE SOUTH
BRINGING WARMER TEMPERATURES TO THE REGION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
HIGH PRESSURE REMAINS OVER THE EASTERN SIBERIA WITH A RIDGE
EXTENDING IN THE CENTRAL BERING SEA. AN UPPER LEVEL TROUGH WILL
PUSH IN FROM THE NORTH OVER SOUTHWEST ALASKA INTO THE EASTERN
BERING SEA AND EASTERN ALEUTIANS. THIS WILL CONTINUE TO PRODUCE
SNOW SHOWERS AND AREAS OF BLOWING SNOW...MAINLY ON THE BERING
SIDE FOR THE EASTERN ALEUTIANS AND AKPEN AS WELL AS ACROSS THE PRIBILOF
ISLANDS THIS EVENING. THERE IS A WEATHER FRONT APPROACHING THE
EASTERN ALEUTIANS FROM THE NORTH PACIFIC SIDE BY MONDAY ASSOCIATED
WITH A STORM FORCE LOW POSITIONED NEAR 44N 165W. THIS WILL START
TO BRING WARMER TEMPERATURES AND MOISTURE TO THE CENTRAL TO
EASTERN ALEUTIANS BEFORE SPILLING OVER INTO THE BERING SIDE
HEADING INTO THE EARLY PART OF NEXT WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...A RATHER LARGE VERTICALLY
STACKED LOW CENTERED WELL SOUTH OF THE EASTERN ALEUTIANS WILL
SLOW AS IT DRIFTS EAST TUESDAY TO BECOME STATIONARY SOUTH OF THE
ALASKA PENINSULA AND WESTERN GULF WHERE IT WILL REMAIN THROUGH
LATE WEEK. AN UPPER LEVEL RIDGE OUT AHEAD OF THE LOW WILL AMPLIFY
OVER THE EASTERN PACIFIC AND GULF OF ALASKA ON MONDAY THEN SHIFT
EAST OVER SOUTHEAST AND SOUTHCENTRAL ALASKA TUESDAY BEFORE SETTING
UP RESIDENCE AS A CONTINENTAL SCALE BLOCKING RIDGE STRETCHING
ACROSS THE WESTERN US AND WESTERN CANADA. THESE TWO VERY LARGE
SCALE FEATURES WILL STEER WARMER MOISTER AIR AND A SERIES OF LOW
PRESSURE SYSTEMS UP INTO THE GULF THROUGH THE WEEK.

WHILE MODEL DIFFERENCES IN THE TIMING AND STRENGTH OF THE
INDIVIDUAL LOW PRESSURE WAVES HAVE INCREASED SINCE YESTERDAY THERE
IS STILL GOOD CONSISTENCY IN THE LARGE SCALE FLOW PATTERN...SO
CONFIDENCE REMAINS HIGH IN THE PATTERN SHIFT OCCURRING AND THE
TREND OF INCREASING TEMPERATURES AND INCREASING PRECIPITATION
THROUGH THE WEEK...ESPECIALLY ALONG THE COAST. WITH COLD AIR WELL
ENTRENCHED INLAND FREEZING RAIN CONTINUES TO BE A CONCERN AS DOES
ALL OTHER PRECIPITATION TYPES HOWEVER THE SPECIFIC TRACK OF THE
INDIVIDUAL LOWS (WHICH CONFIDENCE IS LOWER ON) WILL BE KEY IN
DETERMINING WHICH AREAS GET WHAT PRECIPITATION TYPES. STRONG WINDS
ESPECIALLY IN THE MARINE AREAS WILL ALSO LIKELY BE A SIGNIFICANT
IMPACT THROUGH THE WEEK WITH MANY OF THE FRONTAL WAVES.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...BLIZZARD WARNING 171
         WIND CHILL ADVISORY 152 155 161
MARINE...STORM 120 130 131 138
         GALE 119 127 128 132 136 137 139 150 155 165 170
         173 175 179 180 181 185
         HEAVY FREEZING SPRAY 121 125 126 127 128 130 138
         139 140 141 150 155 165 170 179 180 185
FIRE WEATHER...NONE

&&

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