Small Craft Advisory 470, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
412 PM AKDT MON AUG 27 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE FORECAST
AREA UNDER MOSTLY CLOUDY SKIES AS LOW OVER THE NORTHERN GULF
DRIFTS EAST. RAIN IS BEING REPORTED OVER THE NORTHEAST GULF COAST
AREAS ALONG NEAR CROSS SOUND. THE WEATHER FRONT IS JUICY WITH
MOISTURE AND ALONG WITH STRONG VERTICAL MOTION RAIN HAS BEEN
MODERATE TO HEAVY AT TIMES OVER THE NORTHERN GULF THIS AFTERNOON.
AS THE FRONT DRIFTS ACROSS THE REST OF THE FORECAST AREA THE RAIN
WILL SPREAD FROM NORTH TO SOUTH THROUGH TONIGHT. RAIN WILL BE
HEAVY AT TIMES MAINLY ALONG THE COAST MOUNTAINS FROM JUNEAU TO
WRANGELL FRO THIS AFTERNOON THROUGH LATE TONIGHT. AMOUNTS WILL
RANGE FROM .75-1.25 OF AN INCH FOR TONIGHT. THE WEATHER FRONT IS
FAST MOVING AND WILL BE OVER THE CENTRAL AREAS BY MID TUESDAY
MORNING WITH SCATTERED SHOWERS OVER THE NORTHERN GULF BUT SHOWERS
WILL PERSIST OVER THE NORTHERN HALF OF THE PANHANDLE AS THE UPPER
LEVEL LOW MOVES RIGHT OVER THE NORTHERN THIRD BY THE AFTERNOON.
AS THE UPPER LEVEL LOW DROPS THROUGH THE PANHANDLE THE SHOWERS
WILL BECOME SCATTERED OVER THE FAR NORTHERN INNER AREAS BY THE
AFTERNOON. THE SOUTHERN AREAS WILL CONTINUE TO SEE RAIN INTO TUE
AFTERNOON BUT THE COAST AREAS MAY SEE SOME MORE BREAKS.

 THERE IS A SURFACE RIDGE OVER THE PANHANDLE AND AS HAS SHARPEN
UP THROUGH TODAY AS THE LOW OVER THE NORTHERN GULF DRIFTS EAST.
THIS RIDGE HAS INCREASED THE PRESSURE GRADIENT OVER THE INNER
CHANNELS WITH SMALL CRAFT WINDS TO 30 KT OVER NORTHERN LYNN AND
STRONG GUSTY WINDS NEAR SKAGWAY. THE CLARENCE STRAIT AREA IS ALSO
SEEING SMALL CRAFT WINDS BUT THAT IS FROM A MESO HIGH OVER DIXON
ENTRANCE AND A TROUGH OFF THE COAST OF POW. THE REST OF THE AREA IS
SEEING FAIRLY LIGHTER WINDS BUT THAT WILL CHANGE THROUGH THE EARLY
EVENING AS THE FRONT APPROACHES. THE SOUTHEAST WINDS WILL INCREASE
TO BE FROM 10 TO 20 MPH THIS EVENING BUT AS THE LOW WEAKENS ALL
THE WINDS WILL DIMINISH EVENING THE MARINE WINDS OVER THE NORTHERN
HALF AS THE LOW SLIDES SE. THE SOUTHERN HALF WILL CONTINUE TO SEE
15 TO 20 KT THROUGH TONIGHT.

 AS THE LOW DROPS OVER THE CENTRAL AREAS THE WINDS OVER THE
NORTHERN HALF WILL GO LIGHT AS MENTIONED ABOVE AND THEN INCREASE
FROM THE NORTH AS A HIGH PRESSURE WILL BEGIN TO BUILD OVER THE
YUKON. WINDS OVER LYNN CANAL AND GLACIER BAY WILL INCREASE TO
15 KT BY THE WITH AFTERNOON. THE SOUTHERN AREAS WILL REMAIN NEAR
15 KT.

 USED A MAINLY THE NAM AS IT INITIALIZED THE BEST AND THERE IS
ABOUT AVERAGE FORECASTER CONFIDENCE FOR THE NEXT 24 HRS.

 &&

.LONG TERM...I MADE FEW CHANGES TO THE EXISTING FORECAST. MODELS
SEEMED TO LEND THE LOW ON TUESDAY NIGHT MORE CURVATURE AND LESS
ELONGATION SO MADE SOME ADJUSTMENTS TO WINDS OFFSHORE.
PRECIPITATION FIELDS LOOKED GOOD AND CONTINUED CONVECTIVE WORDING
ON THE BACK SIDE OF EXITING LOW. AS RIDGE PROGRESSES INTO THE GULF
BEHIND THE LOW I KEPT STRATUS AND FOG MID WEEK AS AREAS OF MID AND
UPPER LEVEL SUBSIDENCE COMPRESSES MARINE LAYER. TRANSITIONED TO
STRATIFORM PRECIPITATION WITH NEW SYSTEM LATE IN THE WEEK.

DID LOOK AT NORTHEAST FLOW WEDNESDAY MORNING DRYING THINGS OUT
OVER THE NORTHERN PANHANDLE WITH 30S LIKELY FOR YAKUTAT AND LOW
40S IN SKAGWAY. THEN THINGS BOUNCE BACK LATER IN THE WEEK AS
CLOUDS OVER RUN THE RIDGE...PREPARING US FOR THE NEXT SYSTEM BY
THE WEEKEND.

OVERALL FEW CHANGES IN THE FORECAST...SUGGESTING MODERATE
CONFIDENCE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ036.
         SMALL CRAFT ADVISORY FOR PKZ012-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043-051.

&&

ABJ/JWA