Small Craft Advisory 802, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
546 AM AKST FRI NOV 13 2015

.SHORT TERM...A GALE FORCE LOW OVER THE NE GULF WILL SLOWLY WEAKEN
THROUGH TONIGHT. A SERIES OF SHORTWAVE TROFS WILL MOVE ACROSS THE
AREA THROUGH TONIGHT. A WEAK ARCTIC FRONT WILL DRIFT INTO THE FAR
N TODAY THEN WAVER BACK AND FORTH TONIGHT. MODELS WERE NOT IN
AGREEMENT ON HOW STRONG EACH WAVE WAS GOING TO BE AND POTENTIAL
FOR STRONGER SFC REFLECTIONS. ENDED UP BASICALLY KEEPING THE SFC
PRESSURES AS IS AND MADE ONLY SMALL WIND CHANGES FOR THE MOST
PART. GIVEN THE DIFFERENCES ON THE SMALLER SCALE FEATURES
CONFIDENCE IN THE DETAILS IS NO HIGHER THAN AVERAGE.

JUST ABOUT EVERY ASPECT OF THE FORECAST IS GOING TO BE TRICKY. THE
HIGHEST CONFIDENCE PART OF THE FORECAST IS THAT SHOWERS SHOULD
OCCUR OVER MUCH OF THE AREA THROUGH TONIGHT WITH THE LOW OVER THE
NE GULF. THERE MAY BE LARGER BREAKS IN THE SHOWERS THAN THE POPS
WOULD SUGGEST THOUGH DEPENDING ON SMALLER SCALE FEATURES COMING
ACROSS THE AREA. ANOTHER ISSUE IS HOW MUCH COLDER AIR WILL MOVE
INTO THE FAR NRN PANHANDLE AS THE WEAK ARCTIC FRONT MOVES IN
TODAY...THEN WAVERS N-S SOME TONIGHT. THINK DEEPER PUSH OF COLDER
AIR WILL OCCUR LATE TONIGHT AS UPPER TROF LIFTS OUT. THIS SHOULD
CAUSE PRECIP OVER THE FAR N TO BECOME MAINLY SNOW SHOWERS BY LATE
TONIGHT. COULD SEE A FEW INCHES OF SNOW ESPECIALLY AT HIGHER
ELEVATIONS OF THE HAINES AND KLONDIKE HIGHWAYS.

WINDS HAVE BEEN LOCALLY STRONG EARLY THIS MORNING OVER THE INNER
CHANNELS...BUT THEY SHOULD GRADUALLY DECREASE THROUGH TONIGHT AS
SFC LOW WEAKENS OVER THE NE GULF. HOWEVER...THERE MAY BE
OCCASIONAL BURSTS OF STRONGER WINDS AS SHORTWAVES COME ACROSS THE
AREA ESPECIALLY TODAY. BY TONIGHT...THINK STRONGEST WINDS WILL BE
OVER THE FAR SW CORNER OF THE GULF OFFSHORE WATERS...WITH GALES
THERE. FOR THE REST OF THE AREA...ANY GALES GOING ON NOW SHOULD
DROP TO SCA LEVELS OR LESS BY THIS EVENING.

HAVE REMOVED MENTION OF TSTMS FROM THE FORECAST AS IT APPEARS
THAT THOSE WILL REMAIN S OF THE AREA THROUGH TONIGHT. IF ANY TSTMS
WERE TO GET INTO THE AREA THOUGH...THEY WOULD BE OVER THE FAR SRN
GULF AND ADJACENT COASTAL AREAS.

.LONG TERM...MODELS BEGIN THE PERIOD ON SATURDAY IN GENERALLY GOOD
AGREEMENT ON THE SYNOPTIC PATTERN WITH THE WEAKENING LOW IN THE
NORTHERN GULF. CONTINUED ONSHORE FLOW OVER THE PANHANDLE WILL KEEP
SHOWERS IN THE FORECAST. AS DISCUSSED IN THE SHORT TERM
SECTION...SHOWERS ACTIVITY WILL CONTINUE TO BE DRIVEN BY WEAK
IMPULSES ROTATING AROUND THE LOW AND THE BROAD TROUGH OVER THE
GULF. CAA ALOFT WILL RESULT IN MORE OF THESE SHOWERS FALLING AS
SNOW AT SEA LEVEL OVER THE NORTHERN PANHANDLE. AM NOT EXPECTING
SIGNIFICANT ACCUMULATIONS BUT A FEW INCHES IS LIKELY BY THE END OF
THE WEEKEND. AND THEN THIS IS WHERE THE FUN BEGINS...

SIGNIFICANT MODEL DIFFERENCES HAS LED TO A VERY LOW CONFIDENCE
FORECAST FOR THE MON-EARLY TUE TIME FRAME. A 160 KT SOUTHWESTERLY
JET AT 250 MB WILL MOVE INTO THE GULF AS A POTENT SHORTWAVE DROPS
SOUTH INTO THE WESTERN GULF. MODELS ARE STRUGGLING WITH
INTERACTION BETWEEN THE SOUTHERN AND NORTHERN STREAM. THE GFS IS
PHASING THIS ENERGY WITH NORTHERN STREAM ENERGY RESULTING IN A
DEEPENING LOW PRESSURE SYSTEM AT AROUND 980 MB CROSSING THE
CENTRAL PANHANDLE MONDAY NIGHT. THE GEM HAS A SIMILAR SOLUTION BUT
IS A BIT QUICKER WITH THE SYSTEM CROSSING THE PANHANDLE ON MONDAY
EVENING. THE 00Z ECMWF DOES NOT PHASE THE ENERGY AND LEADS TO A
MUCH WEAKER AND FARTHER SOUTH SCENARIO WITH THE SYSTEM TRACKING
OVER THE FAR SOUTHERN PANHANDLE. BASED UPON CONSISTENCY OPTED TO
GO WITH THE WEAKER 00Z ECMWF SOLUTION. HOWEVER THIS PORTION OF
THE FORECAST WOULD BE SIGNIFICANTLY ALTERED IF THE STRONGER AND
FARTHER NORTH SOLUTION VERIFIES. SIGNIFICANT SNOWFALL WOULD BE
LIKELY NORTH OF THE LOW TRACK WITH STRONG SOUTHERLY WINDS OVER THE
SOUTHERN PANHANDLE. STAY TUNED...

FIRST WINTER AIR OF THE YEAR WILL FILTER INTO THE PANHANDLE
TUE AND MID WEEK WITH 850 MB TEMPERATURES FALLING TO AS LOW AS -22
C AT WHITE PASS...-12 TO -14 C FROM GUSTAVUS TO JUNEAU AND -6 TO
-8 OVER THE SOUTHERN PANHANDLE. THIS WILL YIELD BELOW FREEZING
HIGH TEMPERATURES BY MID NEXT WEEK OVER THE NORTHERN PANHANDLE. A
TIGHTENING NORTHERLY PRESSURE GRADIENT WILL ALSO RESULT IN STRONG
OUTFLOW WINDS. THE FIRST TAKU EVENT OF THE SEASON IS A POSSIBILITY
ESPECIALLY LATER TUE INTO WEDNESDAY. IT DOES NOT APPEAR THIS COLD
AIR OUTBREAK WILL LAST LONG HOWEVER AS MODEL GUIDANCE INDICATES A
WARMING TREND AS WE HEAD INTO THE END OF NEXT WEEK.

USED THE 06Z NAM AND 00Z ECMWF FOR UPDATES TO THE FORECAST THROUGH
DAY 4. ASIDE FROM TEMPERATURE ADJUSTMENTS LEFT THE REMAINDER OF
THE FORECAST FROM DAYS 5 THROUGH 8 AS IS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ033-035-041-042.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-022-031-032-034-036-043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051>053.

&&

RWT/TPS

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