Small Craft Advisory 440, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
329 PM AKDT SAT AUG 4 2012

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWING A
DEVELOPING LOW PRESSURE SYSTEM IN A BAROCLINIC ZONE SOUTH OF THE
AK PENINSULA WITH ASSOCIATED FRONTAL BOUNDARY PUSHING INTO THE
WESTERN AK GULF. THE LOW WILL CONTINUE TO DEEPEN AS IT TRACKS
EASTWARD WITH THE FRONT PUSHING INTO THE EASTERN GULF TONIGHT AND
THEN MOVING OVER THE PANHANDLE BY SUNDAY AFTERNOON. A HIGH
PRESSURE RIDGE AHEAD OF THE FRONT IN THE EASTERN GULF WILL MOVE
OVER THE AK PANHANDLE TONIGHT THEN MOVE INTO CANADA BY SUNDAY.
REMNANTS OF BAROCLINIC ZONE OVER DIXON ENTRANCE KEEPING LOW CLOUD
COVER OVER THE SOUTHERN PANHANDLE WHILE THE CENTRAL AND NORTHERN
PANHANDLE HAVE SEEN INCREASING SUN THROUGH THE DAY. THE SUNSHINE
WILL NOT LAST AS SEEN OVER THE NORTHWESTERN PANHANDLE CLOUDS HAVE
BEEN MOVING IN FROM THE WEST THROUGH THE DAY. MAY SEE SOME
ISOLATED SHOWER ACTIVITY THIS EVENING...MAINLY NEAR THE MOUNTAINS.
AS THE WEATHER FRONT TRACK EAST IN ADDITION TO INCREASING CLOUD
COVER WILL SEE LIGHT RAIN AND DRIZZLE DEVELOP OVERNIGHT AND INTO
SUNDAY AFTERNOON. AREAS SOUTH OF FREDERICK SOUND WILL STAY A BIT
DRIER WITH THE MID LEVEL SOUTHEASTERLY FLOW.

WINDS HAVE BEEN GENERALLY LIGHT TODAY WITH A SEA BREEZE
DEVELOPING THIS AFTERNOON AS DAY TIME TEMPERATURES INCREASED DUE
TO CLEARING SKIES. WINDS WILL SHIFT FROM THE NORTH AND WEST TO THE
SOUTH AND EAST OVER THE INNER CHANNELS AS THE HIGH PRESSURE RIDGE
MOVES OVER THE PANHANDLE THIS EVENING. HOWEVER WINDS WILL
GENERALLY BE LESS THAN 20 KTS. FOR THE NORTHWEST COASTAL WATERS
BARRIER JET FORMATION WITH THE APPROACHING FRONT WILL INCREASE
WINDS TO THE 25 TO 30 KTS RANGE THROUGH SUNDAY.

MODELS WERE IN FAIR AGREEMENT WITH GOOD INITIALIZATION. USED A
NAM/GFS BLEND WITH THE POSITION OF THE PANHANDLE RIDGE AND AS
THERE WERE INDICATIONS THAT THE RIDGE WOULD BE SLIGHTLY WEAKER
THAN PREVIOUS MODEL RUNS. FORECAST CONFIDENCE IS ABOVE AVERAGE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...UPPER LEVEL LOW
SETTLES OVER THE CENTRAL GULF SUNDAY NIGHT THROUGH TUESDAY. THIS
IS A STACKED LOW DOWN TO THE SURFACE. 20-25KT WINDS WILL WRAP
AROUND THE LOW AND ALONG THE FRONTAL BOUNDARY. THE 20KT SOUTHERLY
WINDS MENTIONED IN THE SHORT TERM SECTION THROUGH NORTHERN LYNN
CANAL WILL CONTINUE INTO SUNDAY EVENING WITH OTHER INSIDE WATERS
SEEING 15KT.

THIS LOW IN THE GULF WILL CAUSE STRONG MOIST S-SWLY ONSHORE FLOW OVER
THE REGION SUNDAY NIGHT INTO MONDAY WITH WIDESPREAD RAIN EXPECTED.
THE FAR SOUTHEASTERN AREAS LOOK TO HAVE LESS LIKELY RAIN FALL.
LATER MONDAY AND TUESDAY THE MID-LEVEL FLOW TURNS MORE S-SELY AND
THE PRECIP WILL MOVE INTO THE SOUTHERN AREAS AND THE YAKUTAT AREA
WILL HAVE A DECREASING TREND.

ON WEDNESDAY THE UPPER LEVEL LOW BEGINS TO WEAKEN BECOMING A TROUGH
THURSDAY AND MOVING EAST OVER THE EASTERN GULF FRIDAY AS THE NEXT
LOW DROPS OUT OF THE BERING. THE SURFACE LOW ALSO WEAKENS ON
WEDNESDAY AND THE RIDGE REDEVELOPS OVER THE PANHANDLE WEDNESDAY
NIGHT THROUGH FRIDAY. MID-LEVEL FLOW REMAINS ONSHORE THROUGH MUCH
OF THIS TIME FRAME KEEPING RAIN SHOWERS IN THE FORECAST.

MODELS DIVERGE AS THE LOW WEAKENS ON WEDNESDAY BUT HAVE SIMILAR IDEA
OF THE RIDGE REBUILDING. MADE MINOR CHANGES TO THE FORECAST
OVERALL. BIGGEST ADJUSTMENTS WERE TO INCREASE MINIMUM TEMPERATURES
AS CLOUD COVER EACH NIGHT WILL LIMIT RADIATIONAL COOLING.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ043-051-052.

&&

PRB/HANNON