Small Craft Advisory 414, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
301 PM AKDT SUN JUL 15 2012

.SHORT TERM...A WEAK FRONT WILL MOVE OVER THE NORTHERN PANHANDLE
TONIGHT AND MONDAY ASSOC WITH A BROAD UPPER LEVEL TOUGH AND VORT
MAX. LIGHT RAIN HAS STARTING IN THE YAKUTAT AREA AS A RESULT OF
THIS AND WILL MOVE INTO THE NORTHERN PANHANDLE OVERNIGHT AND INTO
MONDAY MORNING. ALONG WITH THIS WE WILL SEE OVERCAST SKIES AND
AREAS OF FOG AND DRIZZLE. TO THE SOUTH A RIDGE OF HIGH PRESSURE
WILL BE PUSHED OFF AND REDEVELOP OVER THE GULF. THIS RIDGE WILL
KEEP THE SOUTHERN AREAS MOSTLY DRY THROUGH THE PERIOD...HOWEVER
HIGH CLOUDS WILL INCREASE OVERNIGHT.

 FLOW WILL BECOME WESTERLY ONSHORE AT ALL LEVELS OVERNIGHT. THIS
WILL HELP TO PUSH A MARINE LAYER INTO THE COASTAL AREAS AND
THROUGH THE INSIDE WATERS OPEN TO THE GULF. THUS HAVE CONTINUED
WITH DRIZZLE AND AREAS OF FOG THROUGH MONDAY MORNING...HOWEVER
NOT AS CONFIDENT WITH HOW DENSE THE FOG WILL BE AS CURRENT
SATELLITE SHOWS IT THINNING SOME. AS THE RIDGE STRENGTHENS IN THE
GULF MONDAY FLOW WILL TURN MORE NORTHWESTERLY AND HELP TO
DECREASE THE LIGHT RAIN/DRIZZLE AND AREAS OF FOG.

 CURRENTLY THE RIDGE ALONG THE PANHANDLE IS CAUSING MAINLY
SOUTHERLY WINDS NORTH OF FREDERICK SOUND AND NWLY WINDS TO THE
SOUTH. STRONGEST WINDS OF UP TO 30KT ARE NORTH OF SULLIVAN ISLAND
IN LYNN CANAL AND UP TO 25 KT IN CLARENCE STRAIT. TOMORROW
MORNING THE RIDGE WILL CAUSE THE LINE OF NWLY WINDS TO SHIFT UP
TO THE ICY STRAIT AREA. WINDS WILL INCREASE AGAIN TO SMALL CRAFT
LEVEL MONDAY AFTERNOON IN NORTHERN LYNN CANAL NEAR TAIYA INLET AS
WELL AS NEAR CAPE DECISION AND CLARENCE STRAIT. THE REMAINING N-S
INSIDE WATERS WILL SEE RELATIVELY LIGHT WINDS OF 10-15KT.

 MODELS HAVE BEEN IN GOOD AGREEMENT WITH THE IDEA OF THE RIDGE
TIPPING OVER AND RE-DEVELOPING IN THE GULF. USED MAINLY THE ECMWF
AND NAM12 TO START THEN ADJUSTED FOR LOCAL EFFECTS. FORECASTER
CONFIDENCE IS ABOVE AVERAGE.

 &&

 .LONG TERM...HIGH PRESSURE RIDGE EXTENDING FROM THE NORTHEAST
PACIFIC INTO THE AK GULF WILL REMAIN IN PLACE THOUGH MID WEEK. A
WEAK SHORT WAVE IN THE YUKON MOVING OVER THE RIDGE MONDAY INTO
TUESDAY WILL KEEP SLIGHT CHANGE OF RAIN FOR THE NORTHERN AREAS.
THIS WAVE WILL DROP THROUGH BRITISH COLUMBIA WEDNESDAY INTO
THURSDAY BUT EXPECTING MOST PRECIP TO REMAIN TO THE EAST OF THE
COAST MOUNTAINS...WITH THE EXCEPTION OF HYDER. VERTICALLY STACKED
LOW PRESSURE SYSTEM WILL MOVE ACROSS THE ALEUTIANS WEDNESDAY
REACHING THE NORTHWESTERN GULF SOMETIME THURSDAY. FRONTAL BAND
ASSOCIATED WITH THE LOW SHOULD REACH THE EASTERN GULF AND
PANHANDLE THURSDAY AFTERNOON INTO THE EVENING. SOME TIMING AND
POSITION QUESTIONS WITH THE LOW AND FRONT SO HAVE ONLY LIKELY POPS
FOR THURSDAY EVENING. BY THE WEEKEND EXPECT THE LOW TO WEAKEN TO
AN OPEN WAVE TROUGH WITH DIMINISHING WINDS AND PRECIP. 850 MB
TEMPS OVER THE PANHANDLE BEING TO DROP WITH THE INCOMING LOW BUT
WITH EXPECTED INVERSION AND MARINE LAYER HAVE KEPT SURFACE
TEMPERATURES LOWER THAN PROJECTED MOS GUIDANCE.

 HIGH PRESSURE RIDGE IN THE AK GULF AND LOW IN BRITISH COLUMBIA
WINDS OVER EAST-WEST ORIENTATED CHANNELS WILL INCREASE MONDAY
NIGHT INTO TUESDAY. NORTHWESTERLY FLOW DUE TO THE AK GULF HIGH
HAVE NORTHERLY WINDS OVER INSIDE CHANNELS SOUTH OF ICY STRAIT.
WINDS WILL SHIFT BACK TO THE SOUTH AS INCOMING LOW PUSHES HIGH
PRESSURE RIDGE FROM THE GULF OVER THE AK PANHANDLE.

 MODELS WERE IN FAIR AGREEMENT AT THE START OF THE LONG TERM WITH
ONLY MINOR DIFFERENCES IN INITIALIZATION. ECMWF AND NAM WERE
SHOWING BEST AGREEMENT THROUGH 12Z WEDNESDAY. GFS BECAME MORE OF
AN OUTLIER MOVING A STRONGER LOW INTO THE GULF THE MID WEEK MUCH
FASTER COMPARED TO THE ECMWF. GFS KEPT THE LOW INTACT LONGER AND
WITH A TRACK FURTHER TO THE SOUTHEAST. RUN TO RUN CONSISTENCY OF
THE ECMWF HAS BEEN BETTER THAN THE GFS AND WAS MORE IN LINE OF
ENSEMBLE MEANS. ANCHORAGE AND HPC INDICATED SIMILAR ANALYSIS AND
UTILIZED MORE ECMWF. UPDATED GRIDS WITH A 12Z NAM/ECMWF BLEND
THROUGH DAY 4 THEN TRANSITIONED TO A ECMWF/HPC BLEND.

 FORECAST CONFIDENCE IS AVERAGE WITH MOST MODELS INDICATING
SIMILAR SYNOPTIC PATTERN BUT LOWER CONFIDENCE DUE TO
INCONSISTENCIES WITH TIMING OF SURFACE FEATURES.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-013-033>036-041-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043.

&&

HANNON/PRB