Gale Warning 49, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
215 PM AKST FRI JAN 15 2010

.SHORT TERM...SATELLITE LOOP THIS MORNING SHOWS A LOT OF OPEN
CELL CUMULUS BETWEEN 40N AND 50N SOUTH OF THE ALEUTIANS BEING
DRIVEN EAST BY A 215KT JET. VERY UNIFORM ZONAL FLOW OF THE JET
STREAM NOTED AS WELL. CYCLOGENESIS IN THE LDQ OF THE JET SOUTH OF
KODIAK IN PROGRESS. MODELS STRUGGLING WITH WHICH WAVE TO DEVELOP
INTO A MAJOR LOW WHICH HAS SOME BEARING ON MODEL CHOICE TODAY.
BELIEVE THE UKMET IS DEVELOPING ITS MAJOR LOW A LITTLE TOO FAR
UPSTREAM RELATIVE TO WHERE THE NOSE OF THE JET IS. FEATURES
MOVING INTO THE NAM MODEL DOMAIN TOO RAPIDLY TO HAVE HIGHEST
CONFIDENCE IN THAT SOLUTION EITHER. ALL ARE SLIGHTLY UNDER
SELLING THE STRENGTH OF THE JET. MODELED MID LEVEL MOISTURE IN
BOTH GFS AND NAM A VERY GOOD MATCH TO WATER VAPOUR IMAGERY THIS
MORNING. GFS ENSEMBLE SPREAD BOTH AT THE SURFACE AS WELL AS ALOFT
VERY GOOD TODAY AND ENSEMBLE MEAN IS A CLOSE FIT TO ECMWF.

 BIG EVENTS TAKING PLACE IN THERECAST AS
CYCLOGENESIS AND FRONTOGENESIS OCCUR SOUTH OF THE GULF TODAY WITH
EXCELLENT UPPER LEVEL JET SUPPORT. STRONG SOUTHEASTERLY WINDS IN
ADVANCE OF THE FRONT WILL ENTER THE EASTERN GULF TONIGHT AND
COASTAL MARINE ZONES SHOULD STEADILY RAMP UP THROUGH THE NIGHT.
HAVE AS HIGH AS STORM FORCE WINDS FOR PKZ041 TOMORROW. ALSO WILL
BE ISSUING WIND ADVISORIES FOR ZONES 23...27...AND 28 WITH THE
AFTERNOON FORECAST. THESE ARE EXPECTED TO EXTEND INTO THE INITIAL
PORTION OF THE LONG RANGE FORECAST PERIOD. ELSEWHERE...WINDY
CONDITIONS DEVELOPING AS THE GRADIENT TIGHTENS UP AND OUTFLOW
WINDS INCREASE. GALES OVER SUMNER...CLARENCE...SOUTHERN
CHATHAM...AND CROSS SOUND.

 THE OTHER BIG ISSUE IS RAIN VERSUS SNOW. BELIEVE THE RAIN-SNOW
LINE WILL DROP FAR ENOUGH SOUTH TONIGHT TO RESULT IN
ACCUMULATIONS OVER ANGOON AND POSSIBLY PETERSBURG. NOT EXPECTING
SNOW ALONG THE OUTER COAST SOUTH OF CAPE FAIRWEATHER...SO LITTLE
IF ANY ACCUMULATION FOR ELFIN COVE. THE BIG CONCERN IS NORTH OF
THERE. PLANNING ON ISSUING WINTER WEATHER ADVISORIES FOR ZONES
17...18...AND 25 WHICH WILL EXTEND INTO THE INITIAL PORTION OF
THE EXTENDED RANGE FORECAST. SNOW TOTALS IN ZONE 19 WILL RESULT
IN A WINTER STORM WARNING. PRIMARY CONCERN THERE IS NOT SO MUCH
DOWNTOWN HAINES OR OTHER LOCATIONS NEAR LYNN CANAL BUT RATHER
ALONG THE HAINES HIGHWAY WHICH SHOULD SEE OROGRAPHIC LIFT IN
ADDITION TO OVER RUNNING. HAVE 24 HOUR TOTALS IN THE 12 INCH
RANGE. NUMBERS FOR THE KLONDIKE HIGHWAY ARE A LITTLE LOWER AT
9 INCHES.

 FORECAST CONFIDENCE ABOVE AVERAGE. OPTED TO USE GFS AS PRIMARY
GUIDANCE TODAY WITH A BLEND OF NAM OVER LAND TO CAPTURE HIGHER
RESOLUTION DETAILS.

&&

.LONG TERM...START OF LONG TERM FORECAST HEAVILY INFLUENCED BY
COORDINATION WITH SHORT TERM DESK. MODELS WERE IN GOOD AGREEMENT
THAT SOMETHING WAS GOING TO HAPPEN...HOWEVER NONE OF THEM AGREED
ON EXACTLY WHAT THAT WAS GOING TO BE. DECIDED TO USE THE GFS WITH
SOME NAM BLENDED IN FOR DETAILS OUT TO DAY 4. GFS WAS DEALING THE
BEST WITH JET STREAM CYCLOGENESIS. MODEL DISAGREEMENT DIMINISHES
BY DAY 4 AS ECMWF AND GFS FALL MORE INTO LINE WITH SOME FAIR
AGREEMENT. USED A BLEND OF EC WITH HPC GUIDANCE FOR THE REMAINDER
OF THE TIME.

HEMISPHERIC 5 WAVE AT 500MB DEPICTS LONG WAVE TROUGH INTO THE W
GULF SLOWLY DIGGING SOUTH AND TRACKING EAST WITH A LARGE
AMPLITUDE RIDGE BUILDING BEHIND. STRONG JET MAX TO THE SOUTH WILL
CONTINUE TO ADVECT EAST. SURFACE LOW IN THE GULF FROM SHORT TERM
DISCUSSION WILL CONTINUE TO WEAKEN SAT NIGHT AS IT TRACKS TOWARD
PRINCE WILLIAM SOUND. RIDGE OF HIGH PRESSURE WILL BUILD OVER THE
PANHANDLE SUN NIGHT AND MOVE EAST TOWARDS BRITISH COLUMBIA. NEXT
MAJOR LOW PRESSURE SYSTEM WILL TRACK INTO THE SE GULF FORM THE N
PAC WED INTO THU. WITH WINDS SHIFTING TO OFFSHORE FLOW WILL SEE A
DRYING TREND AS THE START OF NEXT WEEK BEFORE NEXT FRONTAL BAND
MOVES BACK OVER THEN PANHANDLE. EXPECTING A QUIETER PATTERN
DEVELOPING AT THE START OF THE LONG TERM.FOR THE SOUTHERN
PANHANDLE WINDS WILL BEGIN TO DIE DOWN THROUGH SAT NIGHT. FOR THE
NORTHERN PANHANDLE WILL SEE SNOW FALL DIMINISHING AS FRONT MOVES
N. THAT SAID DECIDE TO KEEP WARNING AND ADVISORIES IN EFFECT
UNTIL MID NIGHT SAT. WINDS ALONG THE OUTSIDE WATERS WERE BROUGHT
DOWN MUCH FASTER WITH CURRENT MODEL CHOICE SO HAVE GALES DROPPING
DOWN TO SMCR BY SUN AFTERNOON FOR ZONES 41 TO 43.

FORECAST CONFIDENCE FOR THE START OF THE LONG TERM WAS FAIRLY
LOW. CORRECT MODEL CHOICE WILL BE THE DETERMINING FACTOR IN
SUCCESS. CONFIDENCE IMPROVES OVER TIME AS PATTERN SIMPLIFIES AND
MODELS FALL ORE INTO LINE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 9 AM SATURDAY TO MIDNIGHT AKST
SATURDAY NIGHT
     FOR AKZ023-027-028.
         WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO
MIDNIGHT AKST
     SATURDAY NIGHT FOR AKZ017-018-025.
         WINTER STORM WARNING FROM 6 PM THIS EVENING TO MIDNIGHT
AKST
     SATURDAY NIGHT FOR AKZ019.
MARINE...STORM WARNING FOR PKZ041.
         GALE WARNING FOR PKZ011-022-033-035-036-042-043-051-052.

         SMALL CRAFT ADVISORY FOR PKZ012-013-021-031-032-034.

&&

FRITSCH/PRB