Small Craft Advisory 509, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
509 AM AKDT SUN SEP 9 2012

.SHORT TERM...EARLY MORNING SATELLITE LOOP SHOWS AN EXITING
FRONTAL PASSAGE OVER THE SOUTHEASTERN PANHANDLE AND AN INCOMING
FRONT ACROSS THE EASTERN GULF. MODERATE TO HEAVY RAIN SHOWERS HAVE
BEEN PASSING ACROSS THE CENTRAL PANHANDLE. BIORKA RADAR DETECTS A
STRONG SHOWER BAND OVER THE CENTRAL OUTSIDE WATERS...HEADING
TOWARD SITKA AREA. THE INCOMING FRONTAL PASSAGE IS ALSO
ACCOMPANYING THE SMALL CRAFT WINDS/SEAS OVER THE OFFSHORE WATERS AT
THIS TIME.

RELATIVELY COOL AIR ALOFT MOVES OVER THE OUTER WATERS AROUND THE
LOW. EAST TO SOUTHEAST OF THE LOW CENTER...INSTABILITIES HAVE
INCREASED TO LEAD POTENTIAL THUNDERSTORMS ACROSS THE SOUTHERN
OUTSIDE WATERS...INCLUDING SOUTHWESTERN PANHANDLE COAST TO NEAR
PORT ALEXANDER.

MODELS ARE FAIRLY CONSISTENT WITH THE GFS AND ECMWF MAKE A GOOD
CONSENSUS FOR THE NEAR STATIONARY LOW OVER THE EASTERN GULF THIS
MORNING MOVES A LITTLE TO THE NORTH WHILE SLOWLY WEAKENING THROUGH
LATE TONIGHT. THE INCOMING FRONT WILL CONTINUE TO MOVE SLOWLY
SOUTHEASTWARD ACROSS THE CENTRAL AND SOUTHERN PANHANDLE THROUGH
TONIGHT. RAIN SHOWERS WILL TAPER OFF OVER THE NORTHERN AREAS THIS
AFTERNOON AND CONTINUE TO DIMINISH ACROSS THE CENTRAL AREAS LATE
THIS EVENING. ALONG WITH THE FRONTAL BOUNDARY SMALL CRAFT
WINDS/SEAS WILL REMAIN OVER THE SOUTHERN AND CENTRAL OUTSIDE
WATERS THROUGH TONIGHT.

&&

.LONG TERM...IN THE MID TO UPPER LEVEL PATTERN MODEL SOLUTIONS IN
FAIRLY GOOD AGREEMENT WITH EACH OTHER AND THE IDEA THE PREVIOUS
FORECAST PACKAGE WAS WRITTEN USING. THIS LASTS INTO ABOUT THE MID
WEEK TIME FRAME. ISSUES WITH MODEL CONSISTENCY APPEAR HEADED INTO
NEXT WEEKEND WITH A THE SYSTEM MOVING OUT OF RUSSIA AND ACROSS THE
WESTERN BERING SEA...AND TO THE NORTH PACIFIC. THE GENERAL RESULT
OF THIS DIGGING FEATURE IS THE RIDGE BUILDING ALONG THE COAST
REGION.

A RIDGE BUILDING OVER THE WESTERN GULF CUTS OFF THE MOISTURE TAP
TO THE MID TROPICS OVER THE CENTRAL PACIFIC AND WE HAVE THE
REMAINS OF THE LOW MOVING INTO THE WESTERN CANADIAN PROVINCES WITH
WEAK TROUGH PERSIST OVER THE NORTHEAST GULF AND NORTH CENTRAL
PANHANDLE THERE... AND MINOR CONNECTION WESTWARD OVER THE NORTHERN
GULF TO SYSTEM IN THE BERING SEA.

THE SYSTEM THAT MOVES ACROSS THE BERING  WILL BE SPREADING ITS
FRONTAL AND TRIPLE POINT INTO THE WESTERN GULF MONDAY AND COLD
FRONT WILL BE TRAILING BACK TO THE SOUTHWEST. THE INITIAL MOISTURE
PLUME BASED ON SATELLITE READINGS HAS A FAIRLY GOOD MOISTURE PLUME
WITH IT...THEN IT TAPS BACK TO MID TROPICS ON LATE MONDAY/TUESDAY
WITH DEEPENING LONG WAVE TROUGH.

LATE TUESDAY AND THROUGH WEDNESDAY THIS SYSTEM WILL MOVE ACROSS
THE EASTERN GULF AND INTO THE PANHANDLE WITH ITS TRAILING FRONTAL
BAND TO THE SOUTHWEST. THERE IS SOME HINT THAT A WAVE MAY DEVELOP
ALONG IT TO IMPACT THE PANHANDLE LIKELY LATER WEDNESDAY. WITH THE
SLOW MOVING SOUTHWARD MOVEMENT RAINFALL AMOUNTS COULD BE LOCALLY
HEAVIER THAN NORMAL.

FORECAST CONFIDENCE BETTER THAN AVERAGE THROUGH ABOUT MID WEEK AND
THEN AVERAGE OR SO LATER HALF OF THE WEEK AND INTO THE NEXT
WEEKEND.

.HYDROLOGY..A COUPLE OF THE STREAMS ARE FLIRTING WITH BANK FULL
DUE TO THE HEAVIER PRECIPITATION. MONTANA CREEK WITH BURSTS OF
HEAVIER RAIN HAVE SPIKED UP TO JUST OVER 14.5 FT...WHICH IS
SUFFICIENT TO START SPREADING SOME WATER OVER THE ROAD IN JUNEAU.
THIS LASTS FOR A COUPLE OF HOURS THEN THE WATER DRAINS AWAY
QUICKLY. THE OTHER STREAM/RIVER THREATENING SOME FLOODING IN THE
NEAR FUTURE IT THE TAIYA RIVER NEAR SKAGWAY. WATER LEVELS ABOUT
HALF FOOT BELOW 16 FEET WHICH IS WHEN WATER BEGINS TO SPREAD
ACROSS PORTIONS OF THE CHILKOOT TRAIL. THIS SHOULD SUBSIDE TODAY.
A FEW OF THE SMALL QUICK STREAMS OVER THE SOUTHERN PANHANDLE TODAY
COULD SPIKE AS A MOISTURE LADEN SHOWER SPREAD ACROSS THE REGION.
THEN THERE SHOULD BE A DAY OR TWO TO RELAX BEFORE THE NEXT MORE
SIGNIFICANT THREAT TO STREAMS ON WEDNESDAY WITH THE NEXT BATCH OF
HEAVIER RAINS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ041-042.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043.

&&

AHN/BEZENEK