Heavy Snow in Alaska, February 2 to 4, 2008

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST SAT FEB 2 2008

.SYNOPSIS...
.SHORT RANGE...COMPLEX LOW PATTERN OVER THE GULF ALASKA STILL
PARTIALLY EVIDENT IN THE SATELLITE AND WIND PATTERNS FORM THE
SCATTEROMETER PASS THIS MORNING.  THINK THAT THE NORTHERN OF THE
OF THE LOWS IN THE GULF THAT WAS JUST EAST OF KODIAK ISLAND THIS
MORNING WILL BECOME THE MORE DOMINATE OF THE TWO TO STAY IN THE
GULF... THE FURTHEST SOUTH MOVING OFF TOWARDS THE PACIFIC
NORTHWEST AS EXPECTED.

THE MAIN LOW WILL MOVE EAST ACROSS THE NORTHERN GULF BRINGING
WITH IT THE MOISTURE AND THE UPPER LEVEL SUPPORT FOR A FAIRLY
SIGNIFICANT SNOW EVENT ACROSS THE PANHANDLE.  THE YAKUTAT ZONE
SHOULD SEE THE SNOW THIS EVENING TO THIS MORNING...WITH AROUND 8
INCHES OR SO.  ACROSS THE NORTHERN PANHANDLE SNOW WILL START
TONIGHT AND CONTINUE INTO THE SUNDAY MORNING TIME FRAME BEFORE
TAPERING OFF. GENERAL AMOUNTS OF 8 TO 16 INCHES OR SO EXPECTED.
WRANGELL AND PETERSBURG WILL SEE THE SNOWS START CLOSER TO
SUNRISE THROUGH AFTERNOON AND WILL LIKELY SEE ABOUT 6 TO 10
INCHES.

FOR THE PRESENT ONLY SNOW ADVISORIES FOR THE SITKA AND SKAGWAY
ZONES DUE TO WARMER CONDITIONS AFFECTING ACCUMULATION (SITKA) AND
A LESS FAVORABLE FLOW PATTERN (SKAGWAY) FOR THE HEAVIER AMOUNTS.

WINDS FOR THE MARINE FORECASTS DO NOT APPEAR TO BE HIGHER THAN
SMALL CRAFT LEVELS WITH THIS SYSTEM.  BMB

.LONG RANGE...CURRENT GFS RUN NOW LOOKING A LOT MORE LIKE ECMWF
THROUGH 05/12Z WITH BOTH DEPICTING A POSITIVELY TILTED TROUGH IN
THE CENTRAL GULF AND A SHORTWAVE ROUNDING THE BASE OF THIS TROUGH
PARALLEL TO AND JUST OFFSHORE THE PANHANDLE COAST. ECMWF IS
TRENDING A LITTLE MORE AMPLIFIED IN THE UPPER AIR PATTERN AFTER
THIS TIME UNTIL 08/00Z WHEN GFS BECOMES QUICKER TO MOVE ANOTHER
SHORTWAVE AROUND THE UPPER LOW AND INTO THE CENTRAL GULF. BY
09/00Z...THESE TWO MODELS ARE FAIRLY WELL OUT OF PHASE WITH GFS
UNDER-CUTTING A RIDGE OVER WESTERN ALASKA AND ECMWF MAINTAINING A
DEEPER UPPER LOW ANCHORED OVER THE PRINCE WILLIAM SOUND AREA.
ADDING TO THIS...AGREEMENT BETWEEN THE 00Z GFS ENSEMBLE MEAN AND
THE 12Z OPERATION RUN IS ABYSMAL FROM 09/12Z ONWARD...SO NOT VERY
MUCH CONFIDENCE IN THE LONG RANGE GFS MODEL PREDICTIONS AT THIS
POINT.

DIFFERENCES IN MODEL GUIDANCE AFTER 08/00Z REFLECTED IN HPC
COMMENTS AND SO WILL BE SPENDING MOST OF MY TIME CONCENTRATING ON
THE FIRST THREE DAYS OF THE EXTENDED RANGE FORECAST. ECMWF LAYER
RELATIVE HUMIDITY INITIALIZED VERY WELL WHEN COMPARED TO WATER
VAPOR IMAGERY. BOTH GFS AND ECMWF DID A FAIRLY GOOD JOB WITH
UPPER LEVEL WINDS AND JET STREAM LOCATION. HOWEVER...BELIEVE GFS
HAS OVER DONE THE STRENGTH OF THE JET BASED ON CORRESPONDING
SATELLITE WINDS. AT THE SURFACE...SYNOPTIC DATA GIVES ECMWF THE
ADVANTAGE HERE TOO.

A LOW WILL TRACK EAST ACROSS THE SOUTHERN GULF AND INTO THE
BRITISH COLUMBIAN COASTLINE ON TUESDAY. THE ASSOCIATED FRONT WILL
LIFT NORTH ACROSS THE SOUTHERN THIRD OF THE PANHANDLE MONDAY
NIGHT INTO TUESDAY AND LOCATIONS SOUTH OF SUMNER STRAIT SHOULD
SEE A TRANSITION TO RAIN MONDAY NIGHT. MIXED PRECIP SHOULD SPREAD
AS FAR NORTH AS ICY STRAIT BEFORE THE RAIN-SNOW LINE MOVES SOUTH
AGAIN. ALL PANHANDLE LOCATIONS SHOULD BE BACK INTO SNOW BY LATE
TUESDAY AFTERNOON WITH WHAT LITTLE PRECIP IS LEFT BY THIS POINT
AS ANOTHER ARCTIC OUTBREAK SPREADS SOUTH AND IS EXPECTED TO
REMAIN IN PLACE FOR THE REMAINDER OF THE WEEK. FCF

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...HEAVY SNOW WARNING AKZ017-019>022-024>026
      ...SNOW ADVISORY AKZ018-023

MARINE...SML CRFT ADVY PKZ011-021-022-031-034-035-041>043-051>052