Small Craft Advisory 616, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
348 PM AKDT MON OCT 22 2012

.SHORT TERM...SATELLITE LOOP DEPICTS A LARGE ARCTIC HIGH ANCHORS
OVER THE ALASKAN INTERIOR AND YUKON AND AN INVERTED TROUGH
EXTENDS NORTHWESTWARD ACROSS THE EASTERN GULF FROM A LOW NEAR
BRITISH COLUMBIA COAST. A FEW MID CLOUDS DRIFT WESTWARD ACROSS
THE NORTHERN MOST PANHANDLE. LOCALLY STRONG OFFSHORE WINDS
CONTINUE IN DOWNTOWN JUNEAU AND SOUTH DOUGLAS WITH PEAK WINDS OF
35 TO 40 MPH. SOLID GALE PREVAIL OVER NORTHERN LYNN CANAL AND
SMALL CRAFT WINDS OVER CROSS SOUND INTO THE CENTRAL OUTSIDE
WATERS. STRONG GUSTY WINDS CONTINUE OUT OF INTERIOR PASSES. AS
DAYTIME INSOLATION INCREASES...TEMPERATURES SLOWLY SOAR UP INTO
THE 40S FOR MOST AREAS EXCEPT NORTHERN PANHANDLE WHERE THE ARCTIC
AIR MAKES A DIRECT CONTACT. THE EARLY AFTERNOON MERCURY READINGS
REMAIN IN THE LOWER TO MID 30S FOR YAKUTAT...SKAGWAY AND HAINES.

 MODELS REMAIN FAIRLY PERSISTENT WITH HIGH PRESSURE ACROSS THE
ALASKAN INTERIOR AND YUKON PERSISTS THROUGH TUESDAY WHILE A
TROUGH OF LOW PRESSURE REMAINS OVER THE EASTERN GULF. REFRESHED
THE INHERITED FORECAST PACKAGE WITH THE NAM FOR TONIGHT AND
TUESDAY. THE OVERALL CHANGES WERE MINOR. BETWEEN THE ANCHORED
HIGH AND AN INVERTED TROUGH...NORTHERLY PRESSURE GRADIENT WILL
REMAIN TIGHT AND MODERATE TO STRONG OFFSHORE FLOW WILL CONTINUE
WITH STRONG OUTFLOW WINDS NEAR AND ALONG INTERIOR PASSES. KEPT
GALE FORCE WINDS OVER NORTHERN LYNN CANAL THROUGH LATE TUESDAY
MORNING AND SMALL CRAFT WINDS FOR MUCH OF THE REMAINING COASTAL
WATERS...INCLUDING YAKUTAT BAY. THE STRONG WINDS IN DOWNTOWN
JUNEAU AND SOUTH DOUGLAS WILL EASE DOWN EARLY THIS EVENING.

 &&

 .LONG TERM...SYNOPTIC PATTERN REMAINS STABLE AND HAVE VERY GOOD
AGREEMENT BETWEEN MODELS FOR THE REMAINDER OF THIS WEEK. BETWEEN
NOW AND THEN, BOTH GFS AND ECMWF DEPICT A SHARPLY DEFINED UPPER
LEVEL OMEGA BLOCK WITH AXIS THAT EXTENDS FROM THE BERING SEAS
SOUTH ACROSS THE ALEUTIANS AND INTO THE NORTHERN PACIFIC. BOTH
ALSO DEPICT THIS FEATURE MORPHING INTO A SHORT LIVED REX BLOCK AS
A VIGOROUS, SHARPLY DEFINED SHORT WAVE DIGS SOUTHEAST FROM
KAMCHATKA TUESDAY EVENING. MODEL AGREEMENT BREAKS DOWN ON
SATURDAY WHEN GFS RE-ESTABLISHES AN UPPER LEVEL OMEGA BLOCK WITH
AN AXIS THAT EXTENDS FROM THE BERING STRAIT SOUTHEAST INTO THE
CENTRAL GULF. AT THIS SAME TIME, ECMWF DROPS AN UPPER LOW SOUTH
FROM THE BEAUFORT SEA AND MERGES THIS LOW WITH THE KAMCHATKA LOW
OVER THE FAR SOUTHWEST GULF ON SUNDAY. THIS LOW WILL, IN TURN,
PUMP UP A UPPER RIDGE DOWN STREAM OVER THE PANHANDLE. OPTED FOR A
SOLUTION THAT WAS MORE IN LINE WITH THE 00Z ECMWF FROM THURSDAY
ONWARD AND THIS IS IN KEEPING WITH HPC TODAY. EARLIER PORTIONS OF
THE EXTENDED RANGE FORECAST HEAVILY BIASED TOWARDS THE 12Z NAM FOR
PRESSURE AND WIND.

STRONG NORTHERLY/NORTHEASTERLY LOW LEVEL FLOW WILL CONTINUE
THROUGH THURSDAY AFTERNOON WITH SMALL CRAFT LEVEL WINDS OVER THE
NORTHERN INNER CHANNELS AND STRONG GUSTY CONDITIONS COMING OUT OF
INTERIOR PASSES ALONG STEPHENS PASSAGE. SURFACE TEMPERATURES WILL
REMAIN BELOW NORMAL IN TERMS OF DAYTIME HIGHS AND OVERNIGHT LOWS
AS A RESULT OF THE ARCTIC AIR SPILLING INTO THE PANHANDLE FROM THE
CANADIAN SIDE OF THE COAST MOUNTAINS AND MOSTLY CLEAR SKIES AT
NIGHT. NO POP IN THE FORECAST UNTIL THIS COMING WEEKEND WHEN THE
NEXT WEATHER FRONT IS EXPECTED TO AFFECT SOUTHEAST ALASKA. BIG
QUESTION RIGHT NOW IS WHETHER OR NOT ENOUGH LOW LEVEL COLD AIR
WILL REMAIN IN PLACE LONG ENOUGH FOR OVERRUNNING PRECIPITATION TO
PRODUCE SNOW INSTEAD OF RAIN. RIGHT NOW, HAVE DAY TIME RAIN AND
NIGHT TIME SNOW IN THE FORECAST FOR LOCATIONS SOUTH OF THE ICY
STRAIT CORRIDOR.

TEMPERATURES ADJUSTED WITH BIAS CORRECTED MOS AND GFS. SNOW LEVELS
REFLECT GFS WET BULB TEMPS. POP AND QPF FROM ECMWF. FORECAST
CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ025.
MARINE...GALE WARNING FOR PKZ012-022-043.
         SMALL CRAFT ADVISORY FOR PKZ011-013-031-036-051.

&&

AHN/FRITSCH