Small Craft Advisory 99, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST FRI FEB 16 2007

.SYNOPSIS...
.SHORT RANGE...
A FAIRLY STRONG LOW IN THE NORTH PACIFIC WILL MOVE NORTHEAST INTO
THE GULF OF ALASKA SATURDAY. HOWEVER...MOST OF THE STRONGER
PRECIPITATION AND WIND FOR THE PANHANDLE WILL COME WITH THE
OCCLUDED FRONT OUT AHEAD OF THE LOW...WITH PRECIPITATION
SPREADING FROM SOUTH TO NORTH THROUGH THE NIGHT. GFS INITIALIZED
WELL WITH THE LOW AND MOISTURE FIELDS THIS MORNING...AND IS THE
MODEL OF CHOICE.

POSSIBILITY FOR SNOW IS A CONCERN FOR THE NORTHERN AND NORTH
CENTRAL PANHANDLE TONIGHT. EXPECT WINDS TO QUICKLY COME BACK
AROUND TO THE NORTH FOR THESE AREAS THIS EVENING AS THE OCCLUSION
APPROACHES. THESE WINDS SHOULD REACH GALE FORCE BY LATE TONIGHT
FOR LYNN CANAL...WITH LOCALIZED STRONG WINDS NEAR DOWNTOWN JUNEAU
AS WELL. ALONG WITH THIS NORTHERLY WIND SHIFT WILL COME THE
POSSIBILITY OF A SHOT OF SIGNIFICANT SNOW AS THE OCCLUSION
APPROACHES. TEMPERATURES WILL BE MARGINAL...WITH READING HOVERING
RIGHT AROUND FREEZING. EXPECT THE NORTH CENTRAL PANHANDLE TO
CHANGE OVER TO RAIN BY MIDDAY SATURDAY AS THE FRONT PASSES.
LOCALLY HEAVY RAINFALL WILL OCCUR BEGINNING THIS EVENING FOR THE
CENTRAL AND SOUTHERN PANHANDLE...ALONG WITH STRONG WINDS FOR SOME
AREAS. PRECIPITATION WILL CONTINUE OVER THE ENTIRE AREA THROUGH
THE DAY SATURDAY...AS THE MAIN LOW WILL STILL BE JUST OFF THE
COAST.

.LONG RANGE...FORCAST PACKAGE THROUGH NEXT WEDNESDAY WILL
CHANGE LITTLE...INCLUDING TEMPERATURES FROM NEAR FREEZING
TO A FEW DEGREES ABOVE WITH MOST FORECAST PERIODS IN CENTRAL
SOUTHEAST ALASKA HAVING BOTH SNOW AND RAIN THROUGH WEDNESDAY.
MODEL CONSENSUS FOR THE LONG RANGE IS GOOD AND THE GFS
CONTINUES TO BE THE PRIMARY GUIDANCE...MODELS DISCUSSED
BELOW.

MOST IMPORTANT TREND IS WED AND THU...WITH THE DETERMINISTIC
MODELS DEPICTING A TROUGH ALOFT DEVELOPING FROM OVER NORTHWAY
AND SPREADING S TO THE EASTERN GULF.  THIS TROUGH...ALONG WITH
AN UPSTREAM RIDGE OF HIGH AMPLITUDE...WILL PROVIDE AN ARCTIC
OUTBREAK OVER THE GULF THAT SHOULD GENERATE STRONG SHOWERS
IN THE EASTERN GULF BEGINNING WED.  AFTER THE CONVECTIVE
AVAIABLE POTENTIAL ENEERGY...CALLED CAPE...GETS MORE USED
UP LATE IN THE WEEK...THE NORTHERN PANHANDLE SHOULD GET
NUMEROUS SNOW SHOWERS.  SOLN WILL BE TO LIMIT THE
COOLING UNTIL SUCCESSIVE RUNS COME IN THAT COULD VERIFY
THE TREND...IE...WE HAVE LEAST CONFIDENCE FURTHEST OUT IN
THE FUTURE.

MODELS...GFS RUNS ARE CONSISTENT...IE..LITTLE DIFFERENCE
FROM THE ENSEMBLE MEAN.  THE ENSEMBLE HAS LITTLE SPREAD AT
500 MB THROUGH NEXT WEDNESDAY.  EUROPEAN HAS SYNOPTIC AGREEMENT.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND ADVISORY ZONES 18 19 25 27 28.
         SNOW ADVISORY ZONE 19.

MARINE...GALE WARNINGS ZONES 12 13 36 41 42 43 310.
         SMALL CRAFT ADVISORIES ELSEWHERE.

TF JT