Gale Warning 436, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
421 PM AKST SUN DEC 23 2012

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWS A SMALL LOW
IN THE EASTERN GULF AT THE END OF A TROUGH EXTENDING FROM A
LARGER LOW IN THE WESTERN GULF. THIS SMALL LOW AND TROUGH AXIS
WILL WEAKEN AS IT PROGRESSES NORTH THIS EVENING. IN THE
MEANTIME...THERE ARE SOME CONVECTIVE CLOUDS WRAPPING AROUND THE
SMALL LOW WITH SNOW SHOWERS SHOWING UP ON THE RADAR BELOW THEM.
THE COLD AIR OVER THE RELATIVELY WARM OCEAN IS ENHANCING THE
INSTABILITY...SO HAVE INCLUDED A SLIGHT CHANCE OF THUNDERSTORMS
FOR THE OUTSIDE WATERS SOUTH OF CAPE FAIRWEATHER THIS EVENING.
ISOLATED TO SCATTERED SNOW SHOWERS WILL SPREAD NORTH INTO THE
PANHANDLE THIS EVENING WITH UP TO AN INCH TONIGHT AND ANOTHER
INCH MONDAY MORNING...MAINLY NEAR YAKUTAT BY THAT TIME. THE
SOUTHERN AREAS WILL SEE PARTLY CLOUDY TO MOSTLY CLEAR SKIES.

THE TROUGH OF LOW PRESSURE IN THE GULF AND THE CANADIAN HIGH
PRESSURE SHIFTING SLIGHTLY TO THE EAST OVER B.C. HAS CAUSED WINDS
TO BE THE STRONGEST THROUGH E-W ORIENTED CHANNELS TODAY AND THE
N-S CHANNELS TO EASE SLIGHTLY. HAVE CONTINUED WITH GALE FORCE
WINDS TO 45KT FOR NORTHERN LYNN DESPITE THIS EASING SINCE THE
GRADIENT WILL TIGHTEN AGAIN AS THE TROUGH MOVES NORTH. THIS WILL
ALSO CAUSE THE WIND DIRECTION THROUGH CHATHAM STRAIT TO SHIFT TO
THE SE BEHIND THE TROUGH...THEN FLIP BACK TO THE NORTH MONDAY
AFTERNOON AS A NEW LOW DISCUSSED IN THE EXTENDED FORECAST MOVES UP
FROM THE SOUTH. THE NORTHEAST GAP FLOW TONIGHT AND CONTINUED COLD
AIR...ALTHOUGH NOT A COLD AS IT HAS BEEN...WILL WARRANT KEEPING
FREEZING SPRAY IN MANY OF THE MARINE ZONES.

EXPECT TEMPERATURES TO DROP BY A COUPLE DEGREES WITH SUNSET
ANYWHERE THAT HAS BREAKS IN THE CLOUD COVER...THEN LEVEL OFF AND
GRADUALLY WARM THROUGH MONDAY. THE WARMING TREND WILL OCCUR ONCE
THE TROUGH PASSES AND FLOW TURNS MORE SOUTHERLY. MOST PLACES WILL
BE A COUPLE DEGREES WARMER ON MONDAY THAN TODAY WAS...ALTHOUGH
REMAINING BELOW FREEZING EVERYWHERE BUT THE EXTREME SOUTHERN
COAST.

USED THE ECMWF AND NAM12 FOR PRESSURE FOR THEIR SUPERIOR
INITIALIZATION OVER THE INSIDE PASSAGE. OVERALL MODELS HAD A VERY
SIMILAR IDEA FOR THE SHOWERS EXPECTED TONIGHT. FORECAST CONFIDENCE
IS AVERAGE.

.LONG TERM...THE HIGHLIGHT OF THE LONG RANGE PERIOD WILL BE A
MORE UNSETTLED WEATHER PATTERN AND MODERATING TEMPERATURES FOR
SOUTHEAST ALASKA. THE UPPER LEVEL FLOW WHICH HAS BEEN DOMINATED BY
THE OMEGA BLOCK WITH HIGH PRESSURE OVER THE BERING AND A COLD
UPPER LOW OVER THE GULF WILL CONTINUE TO BREAK DOWN. THIS UPPER
LOW IN THE GULF WILL RETROGRADE INTO THE BERING BY MIDWEEK SETTING
UP SOUTHWESTERLY FLOW ACROSS THE GULF AND INTO THE PANHANDLE. AT
THE SURFACE...THE LOW PRESSURE SYSTEM MENTIONED ABOVE WILL
CONTINUE LIFTING NORTH INTO THE FAR SOUTHERN GULF AT THE BEGINNING
OF THE LONG RANGE PERIOD. THE INFLUENCE OF THE HIGH PRESSURE
SYSTEM IN THE YUKON AND BC WILL CAUSE THE LOW TO TURN TO THE
SOUTHEAST TUESDAY. THE LOW WILL ALSO BE QUICKLY WEAKENING AS THE
UPPER LEVEL JET SUPPORT PUSHES TO THE EAST. A STRENGTHENING SYSTEM
ENTERING THE WESTERN GULF ON WEDNESDAY WILL SEND A WEATHER FRONT
RACING ACROSS THE GULF AND REACH THE PANHANDLE EARLY THURSDAY.
RIGHT ON ITS HEELS A SECOND LOW WILL SEND ANOTHER FRONT INTO THE
PANHANDLE OVER THE WEEKEND.

AS THE LOW PUSHES NORTHEAST INTO THE FAR SOUTHERN GULF MONDAY
EVENING WINDS WILL INCREASE TO GALE FORCE ACROSS THE SOUTHERN
OUTSIDE COASTAL ZONES. WINDS WILL ALSO INCREASE ALONG THE
SOUTHERN COASTAL LAND AREAS BUT AM EXPECTING THEM TO STAY BELOW
BELOW STRONG WIND CRITERIA. NORTHERLY WINDS IN THE INSIDE CHANNELS
WILL INCREASE AS A RESULT OF THIS SYSTEM TIGHTENING THE GRADIENT
MONDAY NIGHT INTO TUESDAY. THEREAFTER...CONTINUED WEAKENING OF THE
HIGH TO THE NORTH WILL LEAD TO DIMINISHING NORTHERLY WINDS. WINDS
WILL INCREASE TO GALE FORCE AGAIN LATE WEDNESDAY INTO THURSDAY
WITH THE APPROACH OF THE NEXT FRONT. AS THIS LOW PULLS INTO THE
GULF ON THURSDAY WINDS IN THE INNER CHANNELS WILL LIKELY BECOME
MORE SOUTHERLY. THESE WEAKENING WINDS AND EVENTUALLY SHIFT TO A
SOUTHERLY DIRECTION LATER THIS WEEK WILL RESULT IN MODERATING
TEMPERATURES.

PRECIPITATION CHANCES WILL BE ON THE INCREASE LATE WEDNESDAY NIGHT
INTO EARLY THURSDAY AS A FRONT MOVES INTO THE AREA. AT THIS
TIME...INDICATIONS ARE A GOOD PORTION OF THE PANHANDLE WILL SEE
THIS BEGIN AS SNOW. INCREASING SOUTHEASTERLY WINDS WILL ADVECT
WARM AIR IN AND GRADUALLY CHANGE PRECIPITATION OVER TO RAIN
THURSDAY AFTERNOON INTO FRIDAY. HOWEVER...THERE IS THE POTENTIAL
FOR ACCUMULATING SNOW ACROSS THE CENTRAL AND NORTHERN PANHANDLE
BEFORE THIS OCCURS. A BRIEF BREAK IN THE PRECIPITATION EARLY IN
THE WEEKEND BEFORE THE SECOND FRONT MOVES IN AND BRINGS ANOTHER
ROUND OF PRECIPITATION TO THE ENTIRE PANHANDLE.

USED THE NAM FOR THE FIRST PORTION OF THE PERIOD DUE TO ITS
INITIALIZATION OF THE DEVELOPING WAVE IN THE NORTHERN PACIFIC.
TRANSITIONED TO A BLEND OF EC/GFS/HPC FOR THE REST OF THE
EXTENDED. CONFIDENCE IS ABOVE AVERAGE ON A SHIFT TO A MORE
UNSETTLED PATTERN AND INCREASING PRECIPITATION CHANCES BUT THERE
REMAINS NOTABLE TIMING AND STRENGTH DIFFERENCES BETWEEN MODELS.
THIS LEADS TO AVERAGE CONFIDENCE ON THE DETAILS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 3 AM AKST MONDAY FOR AKZ025.
         STRONG WIND THROUGH MONDAY AFTERNOON FOR AKZ019.
         WINTER WEATHER ADVISORY UNTIL 9 AM AKST MONDAY FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ013-031.
         HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         GALE WARNING FOR PKZ012-013-022-031-035-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011-021-032>034-041-042-053.

&&

HANNON/TPS