Small Craft Advisory 692, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
637 AM AKST SAT NOV 17 2012

.SHORT TERM...AN ARCTIC AIRMASS OUTFLOW HAS CONTINUED INTO THE
PANHANDLE FROM THE NORTH AND IS REACHING LOCATIONS IN
CENTRAL SOUTHEAST ALASKA. A 975 MB LOW 200 NM S OF KETCHIKAN
WILL WEAKEN WHILE MOVING N TODAY, AND WILL CONTINUE TO PROVIDE
A WEAK CONTRIBUTION TO THE NORTHERLY LOW LEVEL WINDS ALONG THE
PANHANDLE. A HIGH WIND WARNING HAD BEEN ISSUED FOR A MOUNTAIN
WAVE WIND EVENT THAT IS CALLED "TAKU WIND". GUSTS OF 60 MPH
ARE EXPECTED IN DOUGLAS AND IN DOWNTOWN JUNEAU BEGINNING BETWEEN
9 AM AKST AND NOON TODAY, AND EXTENDING UNTIL MIDNIGHT. CONFIDENCE
IS AVERAGE.

A LARGE ARCTIC AIRMASS IN THE INTERIOR CONTINUES TO BE SUPPORTED
BY A LARGE-SCALE RIDGE ALOFT THAT EXTENDS N ALONG MERIDIAN 180
DEGREES. THE SOUNDING AT WHITEHORSE YT SHOWS THE DEPTH OF ARCTIC
AIR TO BE DEEP ENOUGH TO ENHANCE THE OUTFLOW INTO THE PANHANDLE.
THIS ARCTIC OUTFLOW IS SUFFICIENT FOR THE FREEZING SPRAY ADVISORY
FOR LYNN CANAL, GLACIER BAY, AND SOME OF THE INTERIOR PASSES TO
STEPHENS PASSAGE. PLEASE NOTE THE MARINE AND PUBLIC TABLES BELOW.

&&

.LONG TERM...ENDED UP USING THE 00Z ECMWF OUT TO MON NIGHT...THEN
TRANSITIONED OVER TO LATEST HPC BY TUE NIGHT. THE ECMWF SEEMED TO
HAVE A LITTLE BETTER HANDLE ON SYSTEMS THAT WILL BE MOVING NORTH
THROUGH THE AREA SUN AND SUN NIGHT. LOOKS LIKE MOST OF THE PRECIP
WITH THESE SYSTEMS WILL BE OVER THE SOUTHERN HALF OF THE
AREA...BUT SOME PRECIP WILL LIKELY MAKE IT TO THE NORTH-CENTRAL
AREA ALSO. EXCEPTION TO THIS MAY BE LOCALLY AROUND JUNEAU DUE TO
DOWNSLOPING EASTERLY RIDGE TOP WINDS KEEPING LOWER LEVELS VERY DRY
AND NOT ALLOWING PRECIP TO REACH SEA LEVEL. THERE WAS SOME MODEL
DISAGREEMENT ON THIS HOWEVER...SO KEPT IN CHANCE POPS AROUND
JUNEAU WHILE GOING WITH LIKELY TO THE SW OF THE AREA. SOME OF THE
PRECIP WILL OCCUR FROM OVERRUNNING THE ARCTIC FRONT WHICH WILL LIE
ACROSS THE CENTRAL AREA SUN AND SUN NIGHT. THINK SNOWFALL AMOUNTS
WILL REMAIN ON THE LIGHT SIDE THOUGH AS MAIN UPPER SUPPORT FOR THE
SYSTEMS SHEARS APART AS THEY TRY TO GET INTO THE NORTH.

FOR MON-TUE...WILL KEEP HIGHER PRECIP THREAT OVER THE SOUTH AS
MORE WEAK SYSTEMS MOVE INTO THAT AREA. THE ARCTIC AIRMASS WILL
DRIFT SLOWLY SOUTH INTO THE SOUTHERN AREA BUT SHOULD GENERALLY
REMAIN NORTH OF THE FAR SOUTH. DID LOWER TEMPS SOME OVER THE NORTH
SUN INTO MON. THERE MAY BE ANOTHER TAKU WIND EVENT IN JUNEAU SUN
NIGHT INTO MON BUT WILL NOT MENTION YET DUE TO THE CURRENT HIGH
WIND WARNING FOR THE SAME AREA.

LATER IN THE WEEK...00Z GFS AND ECMWF SUGGEST POTENTIAL FOR A
STORM TO MOVE INTO THE FAR SE GULF AREA...BUT THEY DIFFERED ON
TIMING AND POSITION ENOUGH TO MAKE THAT A LOWER CONFIDENCE DETAIL.
THE HPC DOES NOT HAVE A STRONG SYSTEM FOR LATE WEEK BUT GIVEN THE
MODEL DIFFERENCES DO NOT WANT TO JUMP ON IT YET AS IT IS STILL
WELL OUT IN THE FUTURE. OF INTEREST...THE 06Z GFS DID TREND IN THE
DIRECTION OF THE 00Z EC ON THIS...WHICH WAS A DAY LATER AND
FURTHER EAST WITH THE STORM THAN THE 00Z GFS WAS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 9 AM THIS MORNING TO MIDNIGHT
AKST TONIGHT FOR AKZ025. STRONG WIND THROUGH THIS AFTERNOON FOR
AKZ018-019.
MARINE...STORM WARNING FOR PKZ012. GALE WARNING FOR
PKZ011-013-022-043. SMALL CRAFT ADVISORY FOR
PKZ021-031>035-041-042-051-052.

 &&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HIGH WIND WARNING FROM 9 AM THIS MORNING TO MIDNIGHT AKST
TONIGHT FOR AKZ025. STRONG WIND THROUGH THIS AFTERNOON FOR
AKZ018-019. WIND CHILL ADVISORY FROM 9 PM THIS EVENING TO 9 AM
SUNDAY FOR AKZ018.
MARINE...STORM WARNING FOR PKZ012. GALE WARNING FOR
PKZ011-013-022-043. SMALL CRAFT ADVISORY FOR
PKZ021-031>035-041-042-051-052.

&&

JBT/RWT