High Wind in Alaska, September 19 to 20, 2013

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
609 AM AKDT THU SEP 19 2013

.SHORT TERM...STRONG STORM MOVING INTO THE PANHANDLE AND
SOUTHEAST GULF IS THE MAIN STORY OF THE DAY. AT THE MOMENT THE
MAIN LOW HAS STRENGTHENED TO AROUND 976 MB AND IS CENTERED AROUND
50N AND 140W. SATELLITE IMAGES SHOW A VERY WELL DEFINED
BAROCLINIC LEAF WITH A VERY EVIDENT DRY SLOT WRAPPING AROUND THE
LOW CENTER. THE ASSOCIATED FRONT STRETCHES NE INTO THE DIXON
ENTRANCE AREA AND THEN SOUTH ACROSS THE NE PACIFIC. THE LOW WILL
RETAIN MUCH OF ITS STRENGTH AS IT MOVES INTO THE SE GULF LATER
TODAY THANKS TO A 120 KT JET STREAK OVER THE SYSTEM.

 GUSTY WINDS AND HEAVY RAIN IS ALREADY STARTING TO IMPACT THE
SOUTHERN PANHANDLE THIS MORNING. HIGHEST GUSTS SO FAR THIS
MORNING ARE 43 KT AT METLAKATLA, 37 KT AT HYDABURG, 35 KT AT
KETCHIKAN, AND 33 KT AT ANNETTE. FARTHER NORTH WINDS HAVE YET TO
BECOME GUSTY AND ARE EVEN STILL OUT OF THE NORTH IN THE NORTHERN
HALF OF THE PANHANDLE. THE HEAVY RAIN HAS ALSO YET TO MAKE IT
FARTHER NORTH THEN THE EXTREME SOUTHERN PANHANDLE BUT IT WILL DO
SO THROUGH THE DAY.

 WINDS ACROSS THE PANHANDLE WILL CONTINUE TO INCREASE THIS
MORNING PARTICULARLY IN THE SOUTH AS THE SYSTEM CONTINUE TO MOVE
NORTH. HIGH WIND WARNINGS FOR ZONES 27 AND 28 AND A STORM WARNING
FOR CLARENCE STRAIT REMAIN UP AS MODEL 850 MB WINDS FORECASTS
CONTINUE TO SHOW 70 TO 80 KT WINDS OVER THE SOUTHERN PANHANDLE
LATER TODAY AND TONIGHT. SURFACE OBS ACROSS HAIDA GWAII SEEM TO
CONFIRM THIS AS WINDS HAVE RAMPED UP RATHER NOTICEABLY AFTER THE
FIRST FRONT MOVED THROUGH THE REGION. ROSE SPIT HAS REPORTED
GUSTS UP TO 59 KT IN THE LAST HOUR OR TWO. FARTHER NORTH ZONES
26 AND 23 HAVE STRONG WIND HEADLINES UP AND VARIOUS INNER
CHANNELS HAVE GALE OR SMALL CRAFT ADVISORIES FOR TODAY AND
TONIGHT AS THE INITIAL FRONT SPREADS THE HIGHER WINDS FARTHER
NORTH TODAY. CHATHAM STRAIT AND STEPHENS PASSAGE WHICH ARE
CURRENTLY SHOWING NORTH WINDS MAY SWITCH AROUND TO A SE WIND LATE
THIS AFTERNOON OR EVENING AS THE SYNOPTIC WINDS BEHIND THE FRONT
OVERPOWER THE PRESSURE GRADIENT WINDS IN THOSE CHANNELS. LYNN
CANAL WILL LIKELY STAY NORTH THROUGH THE PERIOD AS THE FRONT GOES
ALOFT OVER THE NORTHERN PANHANDLE. GALE WARNINGS ARE UP IN THE
GULF AS WINDS UP TO 45 KT AND SEAS UP TO 22 FT LASH THE SE GULF
TODAY AND TONIGHT.

 AS FOR RAIN, RAINFALL AMOUNTS ARE ALREADY REACHING QUARTER INCH
TO .4 INCHES IN ONE HOUR IN VARIOUS AREAS OF THE SOUTHERN
PANHANDLE. RADAR IS SHOWING THAT THE AREA OF HIGH RAINFALL HAS
REACHED SOUTHERN BARANOF AND IS SLOWLY MOVING NORTHWARD. THE
NORTHERN HALF OF THE PANHANDLE HAS SOME SCATTERED SHOWERS STILL
AROUND BUT THE RAIN WILL BECOME MORE STEADY AND HEAVIER AS THE
DAY WARES ON. TONIGHT WILL STILL BE RATHER WET BUT QPF AMOUNTS
WILL NOT BE AS HIGH AS THEY WERE FORECAST TO BE DURING THE DAY.
SOME SMALLER STREAMS COULD RISE TODAY DUE TO THE RAINFALL BUT
MOST ARE FORECAST TO REMAIN BELOW BANKFULL STAGE.

 SHORT RANGE MODELS WERE IN DECENT AGREEMENT WITH A FEW
EXCEPTIONS. THE NAM DID NOT SEEM TO INITIALIZE THIS SYSTEM VERY
WELL AT ALL. IT INITIALLY PLACED THE SURFACE LOW TOO FAR
SOUTHWEST AND IS STILL AN OUTLIER AS THE LOW GET CLOSER TO THE
PANHANDLE (PLACES THE LOW CLOSER TO THE COAST THEN MOST OF THE
OTHER MODELS ARE SUGGESTING). THE ECMWF AND GEM WERE THE BEST AT
DEPICTING THE SYSTEM SO THEY WERE THE MODELS OF CHOICE FOR
OVERALL UPDATES TODAY WITH SOME HIGHER RES MODELS USED FOR WIND
DIRECTION DETAILS IN THE INNER CHANNELS.

.LONG TERM...THERE CONTINUES TO BE DIFFERENCES IN THE OPERATIONAL
AND ENSEMBLE MODELS FROM LATE THIS WEEKEND INTO NEXT WEEK BUT THEY
ARE GETTING BETTER WITH EACH MODEL RUN. BEFORE THAT THE MODELS ARE
COMING INTO AGREEMENT AND THE FORECASTER CONFIDENCE IS GETTING
BETTER FOR FRIDAY AND SATURDAY. THERE WAS SOME CHANGES IN THE MID
RANGE FROM THE PREVIOUS FORECAST...MAINLY IN WIND DIRECTION OVER
THE INNER CHANNELS DUE TO LOW FROM THE GULF LIFTING NORTH INTO
CANADA AND BUILDING A RIDGE OVER THE INNER CHANNELS. USED A BLEND
OF THE GFS/EC FOR FRIDAY AND SATURDAY BUT THEN TRANSITIONED TOWARD
WPC WITH SOME GFS THROUGH NEXT WEEK.

AT THE START OF THE LONG TERM PERIOD THE LOW TALKED ABOUT IN THE
SHORT TERM PERIOD WILL BE WEAKENING OVER THE EASTERN GULF BUT
STILL PRODUCING STRONG WINDS OVER THE COASTAL AND SOUTHERN AREAS.
THE HIGH WIND WARNING FOR THE FAR SOUTHERN AREA AND STRONG WIND
GUSTS OVER THE CENTRAL AREAS WILL SLOWLY DECREASE THROUGH FRIDAY
AS THE LOW WEAKENS AND THE DRIFTS NORTH. AS THIS HAPPENS THE NORTH
CENTRAL AREAS WILL SEE INCREASED WIND GUSTS IN EXPOSED AREAS. THERE
WILL ALSO BE MODERATE TO HEAVY RAINS THROUGH FRIDAY WITH AROUND 1
TO 2 INCHES OF RAIN THAT WILL RAISE SMALL STREAM WATER LEVELS. THE LOW
WILL MOVE INTO NORTH INTO CANADA THROUGH FRIDAY NIGHT AND A RIDGE
WILL BUILD OVER THE INNER CHANNELS. THIS WILL SWITCH THE WINDS
FROM THE NORTH TO SOUTH AND INCREASE THEM TO RANGE FROM 20 TO 30
KT. THERE WILL ALSO BE STRONG WESTERLY WINDS NEAR CROSS SOUND AD
THE LOW REDEVELOPS IN CANADA. THERE WILL NOT BE MUCH OF A BREAK
BETWEEN SYSTEMS AS ANOTHER STRONG DEVELOPING LOW WILL MOVES EAST
FROM THE WESTERN GULF AND SEND A WEATHER FRONT OVER THE EASTERN
GULF SATURDAY AND THEN OVER THE INNER CHANNELS THAT NIGHT. THERE
HAS BEEN SOME DIFFERENCES BUT THE EC HAS MOVED TOWARDS THE GFS AND
THEY ARE IN MUCH BETTER AGREEMENT.

THE TREND FOR THIS LOW IS FOR IT STICK IN THE GULF INTO SUNDAY
BEFORE IT SLIDES SOUTHEAST THROUGH MONDAY AND INTO THE NORTH
PACIFIC. THERE ARE DETAIL DIFFERENCES BUT THE OVERALL TREND FROM
MODELS ARE ON TRACK. THERE IS INDICATION THAT ANOTHER LARGE AND
WET SYSTEM WILL MOVE INTO THE NORTHERN GULF ON WEDNESDAY BUT THERE
ARE LARGE SPREADS IN THE ENSEMBLES SO THERE IS LOW FORECASTER
CONFIDENCE AT THIS TIME. THE GLARING MESSAGE IS THAT THE GULF
WILL REMAIN ACTIVE WITH MULTIPLE LOW PRESSURE SYSTEMS MOVING INTO
AND OUT.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THROUGH FRIDAY EVENING FOR AKZ023-026.
         HIGH WIND WARNING UNTIL 1 PM AKDT FRIDAY FOR AKZ027-028.
MARINE...STORM WARNING FOR PKZ036-041.
         GALE WARNING FOR PKZ033-035-042-043.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-022-031-032-034-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

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EAL/ABJ