Small Craft Advisory 249, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
331 PM AKST FRI MAR 11 2016

.SHORT TERM...ONE OF THE GREATEST PLEASURES IN METEOROLOGY IS TO
WATCH A FORECAST EVOLVE INTO REALITY. THIS WAS A PARTICULARLY
PLEASING AFTERNOON. CONVECTIVE SHOWERS BEGAN DIMINISHING FROM WEST
TO EAST ACROSS THE NORTHERN PANHANDLE AS RIDGING NOSED IN FROM
WESTERN CANADA. HEAVY SHOWERS OCCASIONALLY DRENCHED YAKUTAT WITH
ICE PELLETS AT TIMES. THERE, SHOWERS WILL END EARLY THIS EVENING
AS SKIES BEGIN CLEARING FROM THE EAST. FARTHER EAST OVER THE
NORTHERN INNER CHANNELS...THE SHOWERS ENDED MAINLY THIS MORNING.
SUNSHINE CRACKED THROUGH THE CLOUDS AROUND MID-DAY AND SPILLED
OPENLY ACROSS THE VISTAS IN THE AFTERNOON. THE SOUTH BASKED IN SUN
FROM EARLY HOURS OF MORNING INTO THE AFTERNOON BUT NOW A WEAK
DISTURBANCE IS BEGINNING CHANGE THE SKY COLOR FROM A BRILLIANT
BLUE TO AN OLD FAMILIAR GREY. BRISK SOUTHERLIES THIS MORNING ARE
WEAKENING THIS AFTERNOON AND WILL START TO TURN NORTH AS PRESSURE
GRADIENTS ALIGN PARALLEL WITH A STALLED FRONT TO THE SOUTH AND
HIGH PRESSURE OVER NORTHWEST CANADA.

TEMPERATURES REBOUNDED WITH A BANG THIS AFTERNOON, ECLIPSING 50 IN
THE FAR SOUTH AND REACHING IT ACROSS PARTS OF THE INTERIOR
CENTRAL AREAS INCLUDING OUR OFFICE. JUNEAU/MENDENHALL VALLEY,
SNETTISHAM, HAINES, AND SKAGWAY HAVE EITHER MATCHED OR SET RECORDS
THIS AFTERNOON. THUS WE ADJUSTED TEMPERATURES UPWARD TOMORROW BY A
FEW DEGREES FOR A SIMILAR WARMTH. MOS GUIDANCE IT SEEMS IS MUCH
TOO CHILLY. WE ALSO EXPANDED THE EXTENT OF SCATTERED SHOWERS TO
THE NORTH TO JUST SOUTH OF JUNEAU AND HOONAH SATURDAY AFTERNOON AS
A FRONT LIFTS ACROSS THE PANHANDLE. CLOUDS WILL ADVANCE EVEN
FARTHER AHEAD OF THIS FEATURE. WE DID STUDY THE POTENTIAL FOR
STRONG WIND GUSTS THROUGH DOWNTOWN JUNEAU SATURDAY MORNING AS AN
INFLECTION POINT AT 500 MB TRACKS NORTHWARD ACROSS THE COAST
MOUNTAINS. WHILE 06Z HIGH-RES MODELS SHOW INCREASING WINDS ACROSS
THE BARRIER TOWARD SATURDAY MORNING, THIS WAS HARDLY AN
UNAMBIGUOUS ENDORSEMENT FOR 40 PLUS MPH GUSTS. AT THIS POINT 35
MPH SEEMS A GOOD BASE POINT, AND WE LEFT THE CURRENT FORECAST IN
PLACE.

THERE IS SOME AMBIGUITY IN HOW A LOW TO THE SOUTH MEANDERS INTO
THE SOUTHEAST GULF SATURDAY AFTERNOON. THUS FEW CHANGES WERE MADE
FOR GULF WINDS AND THE SOUTHERN PANHANDLE. OVERALL FORECAST
CONFIDENCE IS GOOD DESPITE THE UNCERTAINTY INTO THE WEEKEND TO THE
SOUTH. NAM/NAMDNG WERE USED FOR SOME CHANGES IN SHOWER COVERAGE.

.LONG TERM...A WEAK BUT LARGE UPPER LEVEL LOW DOMINATES THE GULF
AT THE START OF THE LONG RANGE FORECAST PERIOD. WITH UPPER LEVEL
STEERING FLOW TO THE SOUTH, THIS LOW WILL NOT MOVE OUT OF THE
AREA PROMPTLY, BUT RATHER SLOWLY WEAKEN AS IT DRIFTS NORTH. BEFORE
IT WEAKENS COMPLETELY, IT WILL ROTATE ONE MORE UPPER LEVEL SHORT
WAVE NORTH OVER THE PANHANDLE AND SPREAD SCATTERED SHOWER ACTIVITY
OVER THE SOUTHERN ZONES AS WELL AS THE OUTER COAST AS FAR NORTH AS
SITKA THROUGH SUNDAY AFTERNOON. SCATTERED TO ISOLATED SHOWERS
REMAIN IN THE FORECAST FOR THE SOUTHERN ZONES THROUGH MONDAY
NIGHT. ELSEWHERE, DRY WEATHER IS EXPECTED UNTIL AT LEAST TUESDAY
MORNING. AT THAT TIME, A FRONT WILL BE APPROACHING SOUTHEAST
ALASKA FROM THE SOUTHWEST AND POPS INCREASE THROUGH THURSDAY
MORNING. MODEL AGREEMENT ON THIS FRONT, THE ASSOCIATED SURFACE
LOW, AND LOW LEVEL TEMPERATURE ADVECTION IS STILL POOR, HENCE THE
VERY BROAD AND WEAK POP GRADIENT IN THE FORECAST. IN FACT, MUCH OF
THE EXTENDED RANGE FORECAST REPRESENTS A PROBABILISTIC RATHER THAN
DETERMINISTIC VIEW ON THE WEATHER FOR THE UPCOMING WEEK.

EXTENDED RANGE FORECAST REMAINS UNCHANGED THROUGH WEDNESDAY
AFTERNOON DUE TO FORECAST UNCERTAINTY. REMAINDER WAS UPDATED USING
THE LATEST WPC. OVERALL FORECAST CONFIDENCE IS BELOW AVERAGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041.
     SMALL CRAFT ADVISORY FOR PKZ012-022-031-036-042-043-051-052.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ053.
&&

JWA/FRITSCH

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU