Gale Warning 368, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
357 PM AKST THU NOV 5 2015

.SYNOPSIS...STRONG FRONT APPROACHING THE COAST FROM THIS WEST IS ON
TRACK TO BRING RAIN AND WIND TO SE ALASKA TONIGHT AND INTO FRIDAY.
THE UPPER LEVEL TROF SUPPORTING THIS FRONT IS POSITIVELY TILTED AND
HAS -32C AT 500 HPA WHICH IS COLD. METHINKS THAT THIS IS UNSTABLE
ENOUGH TO WARRANT A MENTION OF MARITIME THUNDERSTORMS OUTSIDE.
FREEZING LEVELS WILL LOWER LATER ON FRIDAY FOR SNOW IN THE
MOUNTAINS AND STAYED WITH THE ADVISORY FOR THE KLONDIKE HIGHWAY.
700 HPA WIND IS ALIGNED WITH LYNN CANAL LATER TONIGHT BUT GETS SOME
WEST COMPONENT TOMORROW.

&&

.SHORT TERM...RAIN HAS STARTED AT YAKUTAT. GALES HAVE STARTED
OUTSIDE. MOST AREAS DRY AT THIS WRITING BUT RADAR SHOWS THE BAND TO
CROSS SOUND AND KRUZOFF ISLAND. INCREASING REFLECTIVITY AS THE BAND
GETS CLOSER. NAM & RFC QPF SHOWS 0.5 INCHES IN MAXES IN THE
MOUNTAINS FOR 6 HOURS LATER TONITE. THE IR SATELLITE SHOWS A MONDO
CIRRUS SHIELD OVER US.

.LONG TERM...THE LOW MOVING INTO THE NORTHERN GULF BY FRIDAY NIGHT WILL
BEGIN TO WEAKEN AND THEN DRIFT SOUTHEASTWARD THROUGH EARLY SUNDAY
WHILE A RIDGE OF HIGH PRESSURE MOVES EASTWARD OVER THE AK GULF.
SHOWERS WILL BEGIN TO TO DIMINISH THROUGH SATURDAY BUT ENOUGH
ONSHORE FLOW TO KEEP SCATTERED SHOWERS AND MOSTLY CLOUDY SKIES
OVER THE PANHANDLE. SUNDAY WILL BE THE BEST CHANCE FOR DRY WEATHER
BUT MODELS ARE NOT INDICATING A WEAK WAVE FORMING OVER THE RIDGE
ON SUNDAY WHICH MAY KEEP MORE ISOLATED SHOWERS OVER THE REGION.

NEXT FRONTAL BAND IS ASSOCIATED WITH A LOW MOVING INTO THE
CHUKCHI SEA WILL MOVE INTO THE EASTERN GULF THROUGH MONDAY
BRINGING IN MORE PRECIP TO THE PANHANDLE. WHAT IS MORE SIGNIFICANT
WITH THIS PATTERN IS THE POTENTIAL COLD AIR DROPPING DOWN FROM
THE INTERIOR, WHICH IS GIVING THE FIRST REAL POTENTIAL FOR SNOW AT
SEA LEVEL FOR THE NORTHERN AND CENTRAL PANHANDLE. THE BIG QUESTION
ON THIS IS...SOME NEW MODEL RUNS ARE MOVING A LOW UP FROM THE
SOUTH, EACH RUN TRACKING IT FURTHER NORTH...WHICH PUTS THE
PANHANDLE RIGHT BACK INTO RAIN. BY THIS TIME USED OF AN ENSEMBLE
METHOD WITH WPC GRIDS WHICH WERE LEANING TOWARD THE COLDER
SOLUTION. DID LOWER TEMPS A FEW DEGREES AND SNOW LEVELS AGL WITH
THE LOWER TEMPS. BUT IF SNOW DOES FALL AT LEAST FOR NOW 12 HOUR
QPF VALUES ARE ON THE LOWER SIDE SO ANY ACCUMULATION AT THE
SURFACE LOOKS ONLY TO BE A FEW INCHES. ANOTHER WELL DEFINED LOW
TRACKS ACROSS THE AK GULF NEXT THURSDAY, WHICH FOR NOW HAS A
SLIGHTLY WARMER AIR MASS.

AK GULF WINDS AND SEAS WILL DROP AS THE LOW EXITS AND SW SWELL
DIMINISHES. NEXT BURST OF SMALL CRAFT WINDS OVER THE GULF WILL BE
LATE SUNDAY AS NEXT WAVE MOVES IN. INNER CHANNEL WINDS WILL
GENERALLY BE LESS THAN 20 KTS WITH SOME HIGHER WINDS DUE TO
INCREASING PRESSURE GRADIENT OVER N LYNN MONDAY.

AS NO ONE MODEL HAD A COMPLETE HANDLE ON THE POSITION OF THE
WEAKENING GULF LOW USED A BLEND OF 12Z ECMWF/GFS. THESE MODELS
LINED UP AGAIN AS THE NEXT FRONT MOVES IN BY MONDAY. USED WPC FOR
DAY 5 ONWARD TO INCORPORATE THE ENSEMBLE SPREAD. FORECAST
CONFIDENCE IS AVERAGE THROUGH THE WEEKEND THEN DROPS AS THE NEXT
SYSTEM MOVE IN ON MONDAY.

&&

.AVIATION...STAYED WITH THE IDEA OF LLWS AS THE FRONT GETS CLOSE TO
THE INDIVIDUAL TAFS. BROUGHT MANY DOWN TO MVFR IN RAIN LATER THIS
EVENING. EXPECT SHRA THROUGHOUT THE DAY TOMORROW WITH CBS ON THE
OUTER COAST.

&&

.MARINE...WHOLE GALES TONIGHT THEN A SHIFT TO SW VERY LATE. SEAS
WILL CONTINUE TO BUILD WITH A LONG LONG FETCH ESPECIALLY ALOFT.
MARINE LIGHTNING IS A REAL POSSIBILITY FOR THE OUTSIDE WATERS.

&&

.HYDROLOGY...EXPECT RISES TONIGHT AND TOMORROW BUT NO FLOODING.
SOME RAINFALL WILL BE LOCKED UP AS SNOW IN THE MOUNTAINS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 3 AM AKST FRIDAY FOR AKZ026.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ020-021-024-027.
         STRONG WIND FROM 9 PM THIS EVENING TO 3 AM AKST FRIDAY FOR
     AKZ025-028.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ022-023.
         WINTER WEATHER ADVISORY UNTIL 9 AM AKST FRIDAY FOR AKZ018.
MARINE...GALE WARNING FOR PKZ022-031-033-035-036-041>043-051>053.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-032-034.

&&

JC/PRB

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU