Small Craft Advisory 365, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
330 PM AKDT SUN MAY 4 2014

.SHORT TERM...A RIDGE OF HIGH PRESSURE OVER THE CENTRAL GULF WILL
GRADUALLY SHIFT OVER THE EASTERN GULF THROUGH MONDAY AFTERNOON.
THIS IS CAUSING DRY NWLY FLOW OVER THE REGION. UNDER THE RIDGE
THERE IS A MARINE LAYER OF LOW CLOUDS AND FOG. THE MARINE LAYER
HAS BEEN QUITE PROGRESSIVE TODAY AND IS NOW JUST OFF THE COAST OF
YAKUTAT. AS THE RIDGE SHIFTS EAST THE MARINE LAYER WILL MOVE INTO
THE REST OF THE OUTER COASTAL AREAS LATER TONIGHT. YAKUTAT AND
ELFIN COVE CAN EXPECT AREAS OF LOW CLOUDS AND FOG IN THE
MORNING...BUT THIS MAY BACK OFF SOME IN THE AFTERNOON. SITKA AND
POW ISLAND WILL SEE THE MARINE LAYER AS WELL...BUT WILL LIKELY NOT
MOVE INLAND MUCH.

THE MARINE LAYER WILL LIMIT RADIATIONAL COOLING TONIGHT FOR THE
COASTAL AREAS AND ALSO LIMIT THE HEATING DURING THE DAY. THEREFORE
REDUCED THE DIURNAL TEMPERATURE RANGE ALONG THE COAST. INLAND AREAS
WILL SEE CLEAR SKIES AGAIN TONIGHT WITH LIGHTER WINDS. LOCATIONS
THAT SAW TEMPERATURES DIP BELOW FREEZING EARLY THIS MORNING CAN
EXPECT THAT AGAIN WITH THE ADDITION OF THE ANGOON AREA AND
KUPREANOF ISLAND. HAVE ISSUED A FROST ADVISORY FOR THE NORTHERN AND
CENTRAL INNER CHANNELS FOR THOSE WIND SHELTERED AREAS AWAY FROM THE
WATER.

MARINE WINDS WILL HAVE A NWLY DIRECTION. AFTERNOON SEA BREEZES
OVER THE NORTHERN INNER CHANNELS WILL COUNTER THIS AND HAVE A
SOUTHERLY SMALL CRAFT ADVISORY FOR NORTHERN LYNN CANAL LATE MONDAY
AFTERNOON. OVER THE SOUTHERN HALF OF THE PANHANDLE WHERE MOST SEA
BREEZE DIRECTIONS ARE NWLY ALREADY...THEY WILL SEE AN INCREASE IN
THE WIND IN THE LATE AFTERNOON SIMILAR TO TODAY.

USED MAINLY THE NAM12 FOR UPDATES TO PRESSURE AND WIND ALONG WITH
SOME LOCAL WRF MODEL FOR WIND DIRECTIONS. FORECAST CONFIDENCE IS
ABOVE AVERAGE FOR THE OVERALL PATTERN...BUT SLIGHTLY LOWER FOR THE
PROGRESSION OF THE MARINE LAYER.

.LONG TERM...GOOD AGREEMENT IN THE 04/12Z OPS MODELS AND ENSEMBLES
TODAY. THE NEWS IS GREATER CERTAINTY THAT THE BLOCKING RIDGE WILL
GIVE WAY TO ONSHORE FLOW ALOFT STARTING TUE EVENING. LOW LEVEL
ONSHORE FLOW DUE TO THE SURFACE RIDGE MOVING INTO THE EASTERN GULF
WILL BRING MARINE AIR AND WESTERLIES THOUGH LOTH TO CLOUD OVER THE
INLAND AREAS QUICKLY. PREFER 04/12Z ECMWF FOR PRES FIELDS FROM
MONDAY NIGHT UNTIL DAY 4 WHEN WPC WAS USED THOUGH DAY 8. TOWARD
NEXT WEEKEND LOOK FOR SOME SORT OF SPLIT FLOW ALOFT AND MOVING AN
UPPER AND SURFACE LOW S OF DIXON ENTRANCE SEEMS CORRECT. CONFIDENCE
MODERATELY HIGH FOR THIS SET OF MEDIUM RANGE FORECASTS.
&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FROST ADVISORY FROM 3 AM TO 8 AM AKDT MONDAY FOR
AKZ019>021-
     024>026.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-033.

&&

HANNON / JC