FXAK67 PAJK 242304
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
204 PM AKST THU DEC 24 2009

.SHORT TERM... ANALYSIS - MAJOR UPR LOW CENTER WELL S OF COLD
BAY THIS MORNING WITH NOT VERY COLD AIR ALF. SOME -32C AT 500 HPA
ADVECTING INTO THE SYSTEM FROM THE NEXT LOW UPSTREAM. A 960 MB
STORM CENTER IS STACKED UNDER THIS MAJOR WITH A MATURE OCCLUDED
FRONT WITH THE MASSIVE WARM SECTOR EVER S & E OF 55N 140W. A
MONDO ZONAL JET AT 250 HPA STARTS AT THE RED SEA WITH A 90 DEGREE
EXIT SPLIT AT 35N 140W. THE SOUTH BRANCH OF THIS JET IS LOADED
WITH TROPICAL MOISTURE. LOOK AT A MERCATOR PROJECTION OF WATER
VAPOR AND THE CONNECTION IS ALMOST FROM NEW GUINEA. WATER AND
WARM AIR RULES.  

IT IS HOLIDAY JOY THAT THE 12Z OPS MODELS ARE IN VERY GOOD
AGREEMENT IN HANDLING THE WARM AIR AND ALL OF THIS MOISTURE THRU
48 HOURS. WILL USE 12Z AK-GFS-40 AS GOOD AS ANY FOR GRIDS WITH
SREF FOR QPF AND POPS. NOTE THAT MAIN SFC LOW IS FILLING THOUGH
STATIONARY FOR A LAST FRONT COMING UP TO THE COAST EARLY FRI
EVENG. WILL HAVE TO KEEP SOME SMALL CRAFT AND GALE WINDS
PRE-FRONTAL ON FRI. 12Z GFS BOUNDARY LAYER WIND SEZ BARRIER JET N
GULF COAST FRI...SUPPORTED BY 925 AND 850 HPA WIND PROGS. 18Z GFS
AND NAM SAY SOLID 45 KT SO WILL STICK TO A STORM WARNING ISSUED
EARLIER. WILL KEEP NIGHTTIME TEMPS WARMING TO OR ABOVE 32F AND
WILL HAVE A HARD LOOK AT FREEZING & SNOW LEVELS. RAIN IS THE MAIN
WORD FOR THE DAY.   

&& 

.LONG TERM...FORECAST MODELS WERE IN FAIRLY GOOD AGREEMENT AT
LEAST TO 00Z SUNDAY AND THEN THE GFS SOLUTION WAS THE ODD MAN OUT
AS IT DEVELOPED A SURFACE LOW OVER THE EASTERN GULF OF ALASKA.
FROM THAT TIME FRAME LEANED MORE TO TOWARDS THE HPC GUIDANCE WHICH
WAS PRIMARILY INFLUENCE BY ENSEMBLE MEANS AND ONE OF THEM WAS THE
ECMWF ENSEMBLE MEAN.

PREDOMINATE WEATHER FEATURE INTO NEXT WEEK IS AREA OF LOW PRESSURE THAT
IS ANCHORED SOUTH OF THE EASTERN ALEUTIANS WITH A WEAK OR JUST
STRONG ENOUGH RIDGE OVER WESTERN CANADA. SOUTH TO SOUTHWEST FLOW
IS THE EXPECTED FLOW SO NO MAJOR COOLING EXPECTED ACROSS THE AREA.
PRECIPITATION SHOULD BE RAIN...WITH SOME LOCALLY MIXED IN SNOW.

CONFIDENCE IN THE FORECAST IS GOOD THROUGH SATURDAY BUT THEN
DIMINISHES AS THE MAIN TREND IS THERE IT WILL BE THE MATTER OF
TIMING SMALLER FEATURES THAT ENSEMBLE MEANS CAN NOT DEPICT SMALL
SCALE FEATURES. 

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 6 PM AKST FRIDAY FOR AKZ027.
         WIND ADVISORY UNTIL 6 PM AKST THIS EVENING FOR AKZ022-023.
         WINTER WEATHER ADVISORY UNTIL 9 PM AKST THIS EVENING FOR AKZ019.
MARINE...STORM WARNING FOR PKZ051-052. 
         GALE WARNING FOR PKZ022-036-041>043. 
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031>035-053. 

&&

$$

JCC/BEZENEK