Heavy Snow in Alaska, February 8 to 10, 2009

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
144 PM AKST SUN FEB 8 2009

.SHORT TERM...MORNING SATELLITE LOOP SHOWS S WEAK RESIDUAL LOW
IN THE NORTHEAST GULF AND A DISSIPATING OCCLUDED FRONT STRETCHING
SOUTHEASTWARD FROM THE LOW ACROSS THE COAST MOUNTAIN RANGE. A
CONSOLIDATING PRECIPITATION BANDS AROUND THE LOW INDICATES AN
ORGANIZING SURFACE TROUGH JUST WEST OF PANHANDLE COAST. A WEAK
HIGH PRESSURE REBUILDS OVER SOUTHWESTERN YUKON AND GENERATES
MODERATE NORTHERLY PRESSURE GRADIENT ACROSS THE NORTHERN
PANHANDLE. RELATIVELY COLD AIR CONTINUES TO DOMINATE ACROSS THE
SOUTHEAST ALASKA WITH CONDITIONALLY UNSTABLE ATMOSPHERE OVER THE
OUTSIDE COASTAL WATERS. MODELS ARE IN GENERAL AGREEMENT WITH THE
WEAK RESIDUAL LOW IN THE NE GULF CONTINUES TO WEAKEN THROUGH LATE
TONIGHT THEN DISSIPATES BY MONDAY AFTERNOON AS A DEVELOPING STORM
IN THE WESTERN GULF EARLY MONDAY TRACKS EAST-SOUTHEASTWARD TO THE
SE GULF BY LATE MONDAY NIGHT. LATEST SATELLITE IMAGERY PICKS UP
THE LEADING EDGE OF A DEVELOPING STORM...SOUTH OF DUTCH
HARBOR...ENTERS THE FAR WESTERN GULF. PREFER TO LEAN OVER THE
NAM12 SOLUTIONS BLENDING INTO THE INHERITED GRIDS TO KEEP THE
CONSISTENCY FROM THE PREVIOUS FORECAST.

 LIGHT SNOW SHOWERS AROUND EAST AND SOUTHEAST QUADRANTS OF THE
WEAK RESIDUAL LOW WILL CONTINUE TO MOVE ONSHORE ACROSS THE
CENTRAL PANHANDLE THROUGH EARLY TONIGHT. BASED ON THE MID TO
UPPER LEVEL VORT MAX FIELD...THE MAIN SNOW CORRIDOR WILL BE FROM
GLACIER BAY EAST TO HAINES AND JUNEAU WITH ABOUT 1 TO 2 INCHES OF
ACCUMULATION. NORTH OF THE LOW...WEAK OFFSHORE FLOW WILL CONTINUE
ACROSS THE YAKUTAT AREA. AS MID TO UPPER LEVEL DYNAMICS WEAKEN
EARLY TONIGHT AND MOVE INTO BRITISH COLUMBIA...THE ATMOSPHERE
OVER THE SOUTHEAST ALASKA WILL BECOME MORE STABILIZED WITH
LOWERED POPS. HOWEVER...UNTIL THE STABILIZATION SETS MORE FIRMLY
BY EARLY TONIGHT....WILL NEED TO MENTION ISOLATED CONVECTIONS
ACROSS SOUTHERN TWO THIRD OF OUTSIDE WATERS THIS EVENING. WINDS
WILL REMAIN ON THE LIGHTER SIDE WITHIN 10 TO 20 KTS RANGE EXCEPT
THE NORTHERN LYNN CANAL WHERE MODERATE NORTHERLY PRESSURE
GRADIENT CONTINUES TO PRODUCED NORTHERLY SMALL CRAFT WIND
TONIGHT. LONG PERIOD OF SOUTHWEST SWELLS ACROSS THE GULF WILL
MAINTAIN SMALL CRAFT SEAS ACROSS THE ENTIRE OUTSIDE WATERS
THROUGH MONDAY.

.LONG TERM...THE LONG TERM OPERATIONAL MODELS ARE IN FAIR TO GOOD
AGREEMENT THROUGH MOST OF THE WEEK WITH NO SIGNIFICANT STRONG SYSTEMS
TO MOVE OVER THE PANHANDLE. THERE WAS NOT MUCH CHANGE FROM THE
PREVIOUS FORECAST BUT WHERE CHANGES WERE MADE USED A BLEND OF THE
12ZGFS/EC THROUGH TUE NIGHT THEN 12EC AND HPC THROUGH DAY 7.
FORECASTER CONFIDENCE IS GOOD THROUGH MOST OF THE WEEK BUT
ENSEMBLE MEMBER SPREADS INCREASE LATE IN THE WEEK INTO THE WEEKEND
SO CONFIDENCE GOES DOWN.

WITH SPLIT FLOW AT THE UPPER LEVEL OVER THE GULF MON NIGHT THERE
WILL NOT BE MUCH OF A CHANCE OF PRECIP OVER THE PANHANDLE. A
SHORT WAVE FROM NORTHERN STREAM WILL DIG SOUTH AND GRAZE THE
NORTHERN AREAS OF THE PANHANDLE TUE AFTERNOON/EVENING. THIS WILL INCREASE
THE THREAT OF SNOW AS TEMPS WILL REMAIN TO BE ON THE COLD SIDE. A
UPPER RIDGE WILL BUILD OVER THE GULF ONCE THIS SHORTWAVE MOVES
INTO CANADA TUE NIGHT WITH A TROF ENTERING THE WESTERN GULF. THIS
TROF WILL DEVELOP A WEAK SURFACE LOW IN THE NORTHERN GULF A SEND A
WEAKENING WEATHER FRONT OVER THE PANHANDLE WED NIGHT INTO THURSDAY. THIS
FRONT WILL PRODUCE SNOW OVER MAJORITY OF THE PANHANDLE WITH POSSIBLE
SOME MIX PRECIP OVER THE FAR SOUTHERN AREAS. THERE UNCERTAINTY WITH
THIS SYSTEM AS THE GFS IS SHEARING THIS FEATURE AND SENDING IT
SOUTH INTO THE NORTH PACIFIC.

FOR THE REST OF THE WEEK INTO THE WEEKEND THERE WILL BE SYSTEMS
MOVING INTO THE GULF BUT THE TREND IS FOR THE TO FALL APART
BEFORE THEY GET INTO THE EASTERN GULF AND OVER THE PANHANDLE.
TEMPS FOR THE WEEK WILL REMAIN NEAR OR BELOW NORMAL.

WIND WISE IT DOES SEEM LIKE THERE WILL ANY BE WIND EVENTS THROUGH
THE WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-041>043-051-052.

&&

SJA/ABJ