Gale Warning 125, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
602 AM AKST SUN FEB 13 2011

.SHORT TERM...THE LARGE-SCALE PATTERN CHANGE IS BEGINNING. WHAT
HAS BEEN A PERSISTENT TROUGH EXTENDING S FM OVER PAFA AND
EXTENDING S FM OVER PAMD HAS BEGUN TO MOVE E AND WILL BEGIN TO
WEAKEN, AND THE OUTFLOW OF ARCTIC AMS FM NW CAN HAS BEGUN.

 THE LARGE-SCALE TROUGH ALOFT HAS BEEN SUPPORTING A QSTNRY 979 MB
LOW INVOF PAMD THAT STILL HAS A LARGE SCALE CIRCULATION. AN
ARCTIC AIRMASS CONTINUES TO ADVECT SE OVER THE AK PEN AND THE WRN
GLFALSK BUT, DUE TO THE LARGE CYCLONIC FLOW, CONTINUES TO PROVIDE
A LONG TRAJECTORY OVER RELATIVELY WARM WATER BEFORE REACHING THE
ERN GLFALSK AND THE PNHDL.

 THE PRIMARY CHANGES ARE AN INCREASE IN THE SNOWFALL IN THE
NORTHERN PANHANDLE AND THE ADDITION OF WIND ADVISORIES FOR THE
SKAGWAY ZONE AS WELL AS THE YAKUTAT ZONE. THE YAKUTAT ZONE WIND
ADVISORY IS FOR THE VICNITY OF INTERIOR PASSES ONLY, AND NOT FOR
THE TOWN OF YAKUTAT. THE REMAINING CHANGES TO THE FORECASTS FOR
THE FIRST 24 HRS ARE SMALL. CONFIDENCE IS AVERAGE.

 980 MB LOW ABT 300 NM S OF PAYA IS TRACKING N AND ALREADY AT OR
NEAR GREATEST DEPTH. ABOUT 06Z THIS EVENING THIS LOW SHOULD BE
ABOUT 983 MB ABT 100 NM SE OF PAYA. THE ASSOCD FRONTAL BAND IS
POORLY ORGANIZED, BUT THE CIRCULATION ASSOCD WITH THE LOW IS
PROVIDING A STRONG ON ONSHORE FLOW EVEN AS AN ARCTIC OUTBREAK
MOVES S TOWARD CENTRAL SE AK.

 THE ARCTIC OUTBREAK HAS ALREADY REACHED PAGY WHICH FELL FROM
35F TO 21F IN THE 2 1/2 HOURS ENDING AT 1332Z.

 THE MODELS FELL INTO TWO GROUPS ON THE LOWS IN THE GLFALSK WITH
THE ECMWF/UKMET SOLN KEEPING THEM DISTINCT AND THE GFS/NAM
SOLUTIONS MERGING THEM TOGETHER.  THE ECMWF/UKMET SOLN WAS
APPLIED.

.LONG TERM...AT THE START OF THE LONG TERM PERIOD THE ARCTIC FRONT WILL
BE DROPPING SOUTH FROM THE YUKON AS A UPPER AND SURFACE TROF
ASSOCIATED WITH THE LOW OVER THE GULF DRIFTS NORTH OVER THE
CENTRAL PANHANDLE. THERE IS SOME SLIGHT DIFFERENCES WITH THE
POSITION OF THE TROF AND HAS MADE THIS PORTION OF THE FORECAST
VERY TRICKY. THE CONSENSUS IS THAT THERE WILL BE STRONG VERTICAL
MOTION FROM THIS INTERACTIONS IN THE VICINITY OF THE NORTH
CENTRAL INNER CHANNELS FROM PAOH TO PAJN SOUTH ALONG THE EAST SIDE
OF BARANOF TO THE FAR NORTHERN AREAS OF ZONE 26. COLD AIR WILL BE
IN PLACE WITH CAA FROM THE ARCTIC FRONT BUT THE MAIN ISSUE WILL BE
MOISTURE AVAILABILITY. THE LATEST SOUNDS INDICATE THAT THERE WILL
BE AROUND HALF INCH OF PERCEPTIBLE WATER AND COULD PRODUCE AROUND
4 INCHES THROUGH MON AFTERNOON BEFORE THE COLD DRY AIR PUSHES
SOUTH MON NIGHT. THE SOUTHERN HALF OF THE PANHANDLE WILL SEE A MIX
OF RAIN AND SNOW BUT CHANGE OVER TO ALL SNOW BY MON NIGHT AS A LOW
LIFTS NORTH OUT OF EASTERN PACIFIC. THE FAR NORTHERN AREAS WILL
SEE DRY CONDITIONS AS THE STRONG NORTHERLY WINDS CONTINUE TO
INCREASE USHERING DRIER CONDITIONS.

AS THE SURFACE HIGH BUILDS OVER THE YUKON THROUGH MONDAY THE STRONG
NORTHERN WINDS WILL INCREASE OVER THE NORTHERN INNER CHANNELS
ALONG OVER THE NORTHERN GULF FROM INTERIOR GAPS. SO WITH THAT SAID
STORM FORCE WINDS WILL DEVELOP THROUGH MON OVER NORTHERN LYNN WITH
MAX GALES OVER THE REST OF THE NORTHERN HALF OF THE INNER
CHANNELS. VERY STRONG GUSTS WILL ALSO DEVELOP OVER THE NORTHERN
GULF TO 60 KT. THESE CONDITIONS WILL PERSIST INTO TUE AFTERNOON.
ALONG WITH THE STRONG WINDS THE COLD AIR MOVING OVER THE AREA WILL
PRODUCE FREEZING SPRAY MONDAY AND SPREAD SOUTHWARD THROUGH TUE.
OVER LAND AS THE NORTHERLY PRESSURE GRADIENT STRENGTHENS THROUGH
MON WIND ADVY GUSTS NEAR PAGY WILL INCREASE TO NEAR HIGH WIND
WARNING BY MON NIGHT WITH A 10+MB GRADIENT FROM PAGY-PAJN. OTHER
PLACES WILL SEE LOCALLY WINDY CONDITIONS THROUGH TUE. THE SURFACE
HIGH OVER THE YUKON WILL SLIDE IN NORTHERN BC THROUGH MON NIGHT.
THIS WILL INCREASE THE CROSS BARRIER FLOW FROM THE EAST AND THE
DEVELOPMENT OF TAKU WINDS WILL OCCUR. SO GUSTS WILL INCREASE TO
50 MPH NEAR DOWNTOWN JUNEAU AND DOUGLAS MON NIGHT ALSO GUSTS OUT
OF INTERIOR PASSES WILL INCREASE TO 60KT ALONG STEPHENS PASSAGE
THROUGH TUE.

THERE WAS NOT MUCH CHANGE FOR THE REST OF THE WEEK DUE TO DIFFERENCES
IN HOW THE UPPER HIGH BREAKS DOWN WITH A TROF MOVING INTO THE
GULF BY WED. THE SURFACE REFLECTION ON THE GFS IS MUCH WEAKER THAN
THE EC. THE ENSEMBLES ARE TRENDING TOWARDS THE EC BUT ATTM DID NOT
FEEL STRONG ENOUGH TO MAKE LARGE CHANGES. ANOTHER ISSUE IS HOW A
UPPER HIGH MOVING EAST FROM THE BERING LATE IN THE WEEK. THE EC
HAS A MUCH HIGHER AMPLITUDE HIGH WHILE THE GFS IS MUCH FLATTER. SO
FOR FROM WED THROUGH NEXT WEEKEND THERE IS LOW CONFIDENCE FOR THAT
PORTION WITH ABOUT AVERAGE TO SLIGHTLY ABOVE FROM MON THROUGH WED.
USED A BLEND OF THE EC/UKMET WITH SOME NAM TO ACCOUNT FOR THE
OUTFLOW WINDS THROUGH TUE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR
     AKZ024-026.
         WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 9 PM AKST THIS
     EVENING FOR AKZ025.
         WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 5 AM AKST
     MONDAY FOR AKZ019.
         WIND ADVISORY FROM 6 PM THIS EVENING TO 4 PM AKST TUESDAY FOR
     AKZ018.
         WIND ADVISORY FROM 6 PM THIS EVENING TO 9 AM AKST TUESDAY FOR
     AKZ017.
         WINTER WEATHER ADVISORY UNTIL 9 PM AKST THIS EVENING FOR AKZ029.
MARINE...GALE WARNING FOR PKZ011-012.
         SMALL CRAFT ADVISORY FOR PKZ013-021-022-033>036-041>043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

&&

JBT/ABJ