Small Craft Advisory 51, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
321 PM AKST SAT JAN 17 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED OVER THE NORTHERN BERING SEA.
AN ASSOCIATED TROUGH STRETCHES FROM THE SOUTHWEST ALASKA MAINLAND
SOUTHWARD INTO THE WESTERN GULF. AN UPPER LEVEL "WAVE" IS
CURRENTLY DISSIPATING OVER SOUTH CENTRAL ALASKA. A NEGATIVELY
TILTED UPPER LEVEL RIDGE IS OVER WESTERN CANADA AND NORTHEAST
ALASKA. A DECENT COLD FRONT IS WORKING ITS WAY THROUGH SOUTHWEST
ALASKA...WHILE SOUTHWEST FLOW ALOFT IS DEVELOPING OVER SOUTH
CENTRAL.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH ABOUT 60
HOURS INTO THE FORECAST (MONDAY AFTERNOON) THEN BEGIN TO SHOW
DIFFERENCES WITH A LOW MOVING INTO THE GULF FROM THE SOUTH.
FORECAST CONFIDENCE FOR THE AFTERNOON PACKAGE IS NEAR
NORMAL...ONLY JUST MISSING BEING ABOVE NORMAL DUE TO THE SHOWERY
NATURE OF THE PATTERN.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
BROAD SOUTHWEST FLOW ALOFT WILL KEEP A SHOWERY REGIME OVER THE
AREA THROUGH MONDAY...WITH THE DOMINANT PRECIPITATION TYPE
GRADUALLY TRANSITIONING TO SNOW BY SUNDAY AS MODEST COLD ADVECTION
CONTINUES. SHOWERS LOOK TO REMAIN MOSTLY SCATTERED IN NATURE FROM
ANCHORAGE INTO THE MAT-SU WITH LITTLE IF ANY ACCUMULATING SNOW
EXPECTED GIVEN THE LACK OF ANY SIGNIFICANT FEATURES MOVING
OVERHEAD IN THE NEXT 48 HOURS.

&&

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

A SHARP COLD FRONT WILL CONTINUE TO SWEEP ACROSS SOUTHWEST
TONIGHT...MAKING ITS WAY EAST FROM BRISTOL BAY INTO THE LOWER
KUSKOKWIM VALLEY. A CHANGEOVER TO ALL SNOW WILL OCCUR BY LATE
THIS EVENING...WITH ACCUMULATING SNOW ALONG THE FRONT. BEHIND THE
FRONT...COLD HIGH PRESSURE WILL SETTLE IN THROUGH MONDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

SNOW SHOWERS WILL REMAIN A THREAT ACROSS THE ENTIRE BERING AND
ALEUTIANS AS THE REGION REMAINS UNDER THE INFLUENCE OF AN ARCTIC
TROUGH. A WEAK FRONTAL ZONE WILL THEN TRACK EAST ACROSS THE
WESTERN AND CENTRAL BERING...BRINGING MORE SNOW SHOWERS BEFORE
WEAKENING LATE MONDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
MODEL GUIDANCE IN THE MID AND LONG TERM IS INCONSISTENT IN BOTH
RUN TO RUN CONSISTENCY AND BETWEEN THE VARIOUS MODELS. THIS LEADS
TO A LOW CONFIDENCE LONG TERM FORECAST. WHAT THERE IS SOME
AGREEMENT ON IS A BROAD AREA OF LOW PRESSURE SOUTH OF THE
ALEUTIANS THAT WILL SLOWLY TRACK EAST THROUGH THE WEEK. VARIOUS
SHORTWAVES WILL MOVE AHEAD OF THIS LOW INTO THE GULF BRINGING WARM
SOUTHERLY FLOW WITH THEM. THE EXACT TIMING AND POSITION OF THESE
FEATURES VARIES GREATLY BETWEEN THE AVAILABLE MODELS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY WARNING 160 180 181 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...CB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...DK