Small Craft Advisory 14, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1230 PM AKST FRI JAN 4 2013

.ANALYSIS AND UPPER LEVELS...
A BROAD LONGWAVE TROUGH REMAINS OVER THE BERING SEA...WHICH IS
ALLOWING SOUTHERLY FLOW ACROSS MUCH OF MAINLAND ALASKA TO KEEP
TEMPERATURES ABOVE NORMAL. THERE IS A LOW LOCATED WELL SOUTH OF THE
GULF OF ALASKA...NEAR 50N...THAT HAS BOTTOMED OUT AND BEGUN TO
WEAKEN. A SHORTWAVE OVER SOUTHCENTRAL THAT BROUGHT SOME LIGHT SNOW
EARLIER TO THE AREA IS MOVING RAPIDLY OFF TO THE NORTH...WITH A
LITTLE SNOW CONTINUING TO FALL OVER THE SUSITNA VALLEY. SCATTERED
SNOW SHOWERS ARE EMBEDDED IN WEAK SOUTHERLY FLOW ACROSS THE SOUTHWEST
MAINLAND. FURTHER WEST...A LARGE BUT FAIRLY WEAK LOW WITH MULTIPLE
CIRCULATION CENTERS IS CROSSING INTO THE WESTERN BERING SEA. AN
ASSOCIATED FRONT IS STRETCHING OUT ACROSS THE ALEUTIAN CHAIN AND
WEAKENING AS THE JET CARRIES IT RAPIDLY TOWARD THE ALASKA PENINSULA.
A SHORT BUT INTENSE PERIOD OF PRECIP ASSOCIATED WITH THE FRONT HAS
DROPPED SOME SNOW ACROSS THE EASTERN ALEUTIANS...WHICH WILL BE MOVING
INTO THE ALASKA PENINSULA AND PRIBILOFS LATER THIS AFTERNOON.

.MODEL DISCUSSION...
THE MODELS AGREE ON THE OVERALL SYNOPTIC EVOLUTION OF THE MAJOR
FEATURES...BUT DISAGREE SIGNIFICANTLY WITH THE SMALLER-SCALE DETAILS.
THE GENERAL PATTERN IS CHARACTERIZED BY THE JET STREAM STAYING SOUTH
OF OUR AREA...THIS HAS LED TO FREQUENT TRIPLE-POINT LOW DEVELOPMENT
OVER THE LAST 10 DAYS...A TREND WHICH WILL GENERALLY CONTINUE OVER
THE NEXT SEVERAL. THE FIRST MAJOR DISAGREEMENT ARISES WITH THE LOW
THAT DEVELOPS SOUTH OF KODIAK ISLAND EARLY SATURDAY MORNING. THE
ECMWF HAD BEEN TRYING TO CARRY THE ENERGY WELL OFF TO THE EAST AND
OUT INTO THE GULF. THE GFS IS HUGGING THE ALASKA PENINSULA...WHILE
THE NAM SPLITS THE DIFFERENCE A BIT AND TAKES THE LOW NORTHWARD JUST
TO THE EAST OF KODIAK ISLAND. THE 12Z EC TRENDED STRONGLY BACK TOWARD
THE NAM SOLUTION...AND THUS A FORECAST TRACK IN LINE WITH THE NAM/EC
SOLUTION IS PREFERRED. BY SUNDAY...THE LARGE LOW CURRENTLY IMPACTING
THE WESTERN BERING MOVES SIGNIFICANTLY TO THE EAST AND WILL BE
LOCATED SOMEWHERE NEAR THE ALASKA PENINSULA. MODELS ARE ALL OVER THE
PLACE WITH THE NUMBER AND PLACEMENT OF SURFACE LOWS...SO WILL OPT FOR
A CONTINUED BROAD-BRUSHED APPROACH TO THE FORECAST THAT DOES NOT
ATTEMPT TO GET TOO FANCY WITH THE DETAILS.

.SHORT TERM FORECAST...
MAINLAND...SOUTHEAST WINDS WILL INCREASE ACROSS THE MAINLAND TONIGHT
IN ADVANCE OF THE WEAKENING BERING SEA FRONT. EVEN THOUGH THERE WILL
NOT BE AN EXCESSIVE AMOUNT OF PRECIP WITH THE FRONT...TEMPERATURES
WILL LIKELY REMAIN COLD ENOUGH TO PRODUCE SOME AREAS OF BLOWING SNOW
ALONG THE DELTA COAST TONIGHT. SIMILARLY...THE FRONT SHOULD BE MOVING
SLOW ENOUGH FOR SEVERAL INCHES OF SNOW TO ACCUMULATE OVER INTERIOR
PORTIONS OF THE BRISTOL BAY ZONE OVERNIGHT INTO SATURDAY MORNING. BY
SATURDAY MORNING THE FRONT MOVES THROUGH KODIAK ISLAND AND INTO THE
KENAI PENINSULA. MOST OF SOUTHCENTRAL WILL BE DOWNSLOPED ONCE AGAIN
FOR THIS STORM...WHICH WILL BRING ANOTHER ROUND OF MODERATE SNOW TO
THE KENAI MOUNTAINS AND PRINCE WILLIAM SOUND.

BERING SEA AND ALEUTIANS...LARGE AND COMPLEX LOW WILL CONTINUE TO
BRING UNSETTLED BUT RELATIVELY QUIET WEATHER TO THE REGION. WINDS
ALONG THE FRONT ARE AT GALE-FORCE...BUT WILL BE WEAKENING WITH TIME.
AS MENTIONED IN THE MODEL DISCUSSION...WITH SO MANY WEAK SURFACE LOWS
ROTATING AROUND UNDERNEATH THE UPPER LEVEL LOW...MANY OF THE FINER
DETAILS ARE VERY DIFFICULT TO PINPOINT MORE THAN 12 HOURS IN ADVANCE.
WEATHER ACROSS THE PRIBILOFS WILL BE GOING DOWNHILL THIS AFTERNOON AS
THE DECAYING FRONT MOVES IN...AND WILL BECOME SHOWERY LATER THIS
EVENING AS ANOTHER LOW STARTS TO FORM NEAR THE ISLANDS. SNOW SHOWERS
AND LIGHT NORTHERLY WINDS WILL BE THE RULE FOR MUCH OF THE REST OF
THE BERING FOR THE START OF THE WEEKEND. BY MONDAY...MODELS ARE
BEGINNING TO AGREE ON A MORE SUBSTANTIAL LOW DEVELOPING NEAR THE
ALASKA PENINSULA. IF THIS HAPPENS...IT WOULD SERVE TO ENHANCE THE
NORTHERLY WINDS AND COLDER AIR MOVING INTO THE EASTERN HALF OF THE
BERING.

.LONG TERM FORECAST...
AS MENTIONED ABOVE...THE MODELS ARE IN GOOD AGREEMENT THAT THE
COMPLEX LOW THAT HAS BEEN PERSISTING OVER THE BERING SEA FOR MORE
THAN A WEEK WILL GRADUALLY SHIFT EASTWARD BY THE END OF THE WEEKEND.
THIS WILL BRING THIS PATTERN OF NUMEROUS WEAK SURFACE LOWS INTO THE
GULF REGION. THIS PATTERN WILL CONTINUE TO LIMIT MOST OF THE
RAIN/SNOW TO THE COASTLINES...WITH GENERALLY DRY CONDITIONS INLAND.
AS THE OVERALL FLOW BECOMES A MORE MORE NORTHWESTERLY TEMPERATURES
SHOULD BEGIN TO GRADUALLY COOL TOWARD MORE NORMAL VALUES.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 120 150 155 160 170 172 175 176 180 185
         HEAVY FREEZING SPRAY 185
FIRE WEATHER...NONE

AMD JAN 13