Heavy Snow in Alaska, December 27 to 29, 2008

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
133 PM AKST SAT DEC 27 2008

.SHORT TERM...MORNING SATELLITE LOOP SHOWS A WELL DEFINED LOW IN
THE NORTH CENTRAL GULF...NEAR MIDDLETON ISLAND...WITH ASSOCIATED
OCCLUDED FRONT STRETCHING EASTWARD ACROSS THE NORTHERN PANHANDLE.
SEVERAL CLUSTERS OF SNOW BANDS ALONG THE FRONTAL BOUNDARY ARE
MOVING NORTHEASTWARD ACROSS THE LOCAL REGION WITH PREVAILING
LIGHT SNOW FOR MOST OF REPORTING STATIONS ACROSS THE SOUTHEAST
ALASKA THIS MORNING. COLDER AIR ALOFT MOVES IN FROM THE NORTH AND
THE ATMOSPHERE BECOMES A LITTLE MORE UNSTABLE WITH INCOMING PULSE
ENERGIES SOUTH AND SOUTHEAST OF THE LOW CENTER. ISOLATED
LIGHTNINGS HAVE BEEN DETECTED ALONG THE CENTRAL COASTAL SECTIONS
FROM SITKA TO PELICAN. SNOW HAS TAPERED OFF OVER MOST OF CENTRAL
INLAND AREAS WITH A LITTLE BREAK IN OVERCAST.

 MODELS ARE IN FAIR AGREEMENT WITH A PERSISTING UPPER LEVEL
SHORTWAVE OVER THE GULF THROUGH THE WEEKEND. PREFER TO LEAN OVER
THE NAM SOLUTIONS WITH ITS GOOD INITIALIZATION CONDITIONS ON
SLOWLY WEAKENING SURFACE LOW FOR TONIGHT AND SUNDAY. A 985 MB LOW
IN THE NORTH CENTRAL GULF THIS EVENING WILL SLOWLY WEAKEN AS IT
MOVES A LITTLE TO THE SOUTHEAST. HIGH PRESSURE WILL CONTINUE TO
EXPAND TO THE NORTH FROM THE ALASKAN INTERIOR THROUGH SUNDAY. AN
EVEN COLDER AIR ALOFT WILL MOVE INTO THE LOCAL REGION FROM THE
NORTH. THIS WILL MAINTAIN THE LOCAL ATMOSPHERE A BIT MORE
UNSTABLE. A FRONT ASSOCIATED WITH THE LOW LOOKS RATHER WEAK BUT
UNDER CONVECTIVELY UNSTABLE CONDITIONS...THIS WILL PRODUCE
ISOLATED CONVECTIONS OVER NORTH CENTRAL OUTSIDE WATERS THIS
EVENING.

 ANOTHER PULSE ENERGY MOVING ACROSS THE CENTRAL GULF THIS MORNING
IS EXPECTED TO ARRIVE NEAR CAPE SPENCER THIS EVENING...BRINGING
ADDITIONAL SIGNIFICANT SNOWFALL OVER ELFIN COVE AND PELICAN AREAS
THROUGH LATE EVENING HOURS. SNOWFALL IN STEWART AREA IS
DECREASING BUT THE AMOUNT WAS UP TO 10 INCHES THROUGH EARLY THIS
MORNING. EXPECT SNOW WILL CONTINUE ACROSS THE HYDER AREA SUNDAY
MORNING. THE NAM HAS HINTED ANOTHER PULSE ENERGY SWEEPING ACROSS
THE WESTERN GULF...SOUTHWEST OF KODIAK...WILL MOVE ACROSS THE
GULF ALONG THE SOUTH SIDE OF WEAKENING LOW AND ARRIVE NEAR DIXON
ENTRANCE BY SUNDAY MORNING. WILL SHORTEN THE SNOW ADVISORY FOR
INLAND AREAS OF NORTHERN PANHANDLE BY 12 NOON BUT EXTEND THE
ADVISORY FOR ELFIN COVE AND PELICAN AREAS THROUGH LATE TONIGHT.
HYDER AREA WILL GO THROUGH EARLY SUNDAY MORNING. WITH THE HIGH
PRESSURE BUILDING IN YUKON STRONG NORTHERLY GRADIENT WILL DEVELOP
AND VERY COLD AIR MOVING INTO THE NORTHERN MOST ZONE WILL
GENERATE WIND CHILLS DOWN TO 40 BELOW ZERO TONIGHT THROUGH EARLY
MONDAY MORNING.

.LONG TERM...THE LONG RANGE CONTINUES TO SHOW THE SAME TREND THIS
MORNING AS IT HAS BEEN FOR THE PAST COUPLE OF DAYS SO WITH THAT
SAID DID NOT MAKE MANY CHANGES TO THE PREVIOUS FORECAST. CONTINUE
TO LOWER TEMPS THROUGH THE WEEK AS THE FORECAST MODELS SHOW VERY
COLD AIR MOVING OVER THE PANHANDLE THROUGH MOST OF THE WEEK. ALSO
ADDED FREEZING SPRAY TO THE MARINE FORECAST AS WITH THE VERY COLD
AIR AND STRONG NORTHERLY GALES IT WILL PRODUCE SOME NASTY
CONDITIONS OVER THE NORTHERN HALF OF THE MARINE AREAS. FORECASTER
CONFIDENCE REMAINS TO BE ABOVE AVERAGE THROUGH MOST OF THE LONG
RANGE BUT THE MODEL ARE STILL HAVING A HARD TIME WITH A LOW MOVING
ALONG THE NORTH PACIFIC AND LIFTS OVER THE CHARLOTTES. THE EC IS
MUCH FURTHER NORTH WITH THIS FEATURE BUT THE NEW 12Z RUN IS
TRENDING FURTHER SOUTHER AND WEAKER...MORE IN LINE WITH THE GFS. CHANGES
WERE MAINLY MADE FROM DAY 5 THROUGH 8 AND CAUSED VERY MINOR
CHANGES AND USED A BLEND OF THE GFS AND THE CURRENT GRIDS ALONG
WITH THE HPC FOR A MORE ENSEMBLE FORECAST APPROACH.

THE OVERALL SYNOPTIC PATTERN WILL KEEP A LONG WAVE TROF OVER THE
GULF THROUGH THE LONG RANGE. THIS WILL KEEP THE SE AK WELL BELOW
NORMAL FOR TEMPS AS THE FLOW WILL COMING OUT OF THE NORTH AND
ORIGINATING IN THE ARCTIC. THE VERTICALLY STACKED LOW IN THE GULF
SUN AFTERNOON WILL CONTINUE TO SLIDE SE THROUGH THE EARLY PART OF
THE WEEK. THIS WILL KEEP SNOW SHOWERS LIKELY AS STRONG VORT MAXS
WILL CONTINUE TO ROTATE AROUND THE UPPER LOW AND MOVE OVER THE
SOUTHERN AREA. THE CHANCE OF SNOW WILL DECREASE SOME OVER THE
SOUTHERN HALF MID- WEEK AS THE UPPER LEVEL FLOW BECOMES MORE OUT
OF THE NORTH WITH THE MAIN UPPER LOW MOVING EAST AND THE BLOCKY
RIDGE OVER THE BERING STRENGTHENS. THE NORTHERN AREAS WILL SEE THE
SCATTERED SNOW SHOWERS DIMINISH THROUGH SUN NIGHT AS A 1035MB HIGH
BUILDS OVER THE YUKON AND TO INCREASE THE OFFSHORE FLOW AT THE
SURFACE. AS THE PRESSURE GRADIENT INCREASES THE WINDS WILL
INCREASE THE WIND ADVY NEAR INTERIOR GAPS. THIS WILL ALSO CAUSE
VERY COLD WIND CHILLS AND AREAS OF BLOWING SNOW. OVER THE MARINE
WATERS THE NORTHERN WINDS WILL INCREASE TO STRONG GALES SUN AND
CONTINUE INTO MID-WEEK. THE STRONG WINDS AND COLD TEMPS WILL CAUSE
FREEZING SPRAY FOR THE NORTHERN HALF AND HEAVY FREEZING SPRAY OVER
THE FAR NORTHERN AREAS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL MIDNIGHT AKST TONIGHT FOR AKZ022.
         WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM AKST MONDAY
     FOR AKZ018.
         WINTER WEATHER ADVISORY UNTIL 6 AM AKST SUNDAY FOR AKZ029.
MARINE...GALE WARNING FOR PKZ011.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-022-033-034-036-041>043-
     051-052.

&&

SJA/ABJ