Small Craft Advisory 114, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE JUNEAU AK
339 PM AKST SUN JAN 31 2016

.SYNOPSIS...UPPER RIDGE OVER THE EASTERN GULF SLOWLY KICKING OUT
EASTWARD INTO B.C. THE SURFACE RIDGE ALSO REMAINS OFF THE COAST AND
IS WEAKENING. SATELLITE IMAGERY SHOWS SKIES CLEARING FROM CAPE
SUCKLING TO CAPE SPENCER AND INLAND AREAS. CIRRUS FROM AN
APPROACHING FRONT IS JUST MAKING IT TO 140W AND SHIP OBS AND BUOYS
ARE STILL 15 TO 20 KT AHEAD OF THE FRONT. UPR JET SPLITS INTO THE
RIDGE. RADAR SHOWS A FEW SHOWERS OFF THE COAST.

&&

.SHORT TERM...FIRST PROBLEM WITH CLEARING TONIGHT WILL BE RADIATION
FOG. WE STAYED WITH PATCHY BUT WILL HAVE TO WATCH IN SUBSEQUENT
SHIFTS. NEXT IS WIND AND PRECIP WITH THE APPROACHING FRONT. KEPT
THE WIND AND RAIN ALONG THE OUTER COAST MONDAY AFTERNOON/EVE. THIS
FRONT WILL WEAKEN A LOT AS IT COMES INTO THE UPPER AND SURFACE
RIDGE BUT IS THE FIRST TO START THE BREAKDOWN OF A BLOCKING HIGH.

.LONG TERM...A WET FORECAST IN STORE THROUGH THE END OF THE WEEK.

THE START OF THE LONG TERM FORECAST PERIOD WILL FEATURE A WEAK
AND DYING WEATHER FRONT SLOWLY PUSHING TOWARDS THE PANHANDLE. THIS
WEATHER FRONT IS GOING TO BRING IN WEAK WARM ADVECTION ACROSS THE
PANHANDLE. THERE WILL BE FAIRLY WEAK VERTICAL MOTION ASSOCIATED
WITH THIS FRONT, SO ONLY ANTICIPATING LIGHT PRECIPITATION ACROSS
THE AREA. THIS WEATHER FRONT WILL NOT BE STRONG ENOUGH TO BRING IN
ENOUGH WARM AIR INTO THE AREA, SO MOST OF THE PANHANDLE SHOULD
STILL BE UNDER THE INFLUENCE OF PRE-EXISTING POLAR CONTINENTAL
AIRMASS. PRECIPITATION TYPE SHOULD BE MOSTLY AS SNOW IN THE
INSIDE PASSAGE, WITH OUTER COAST SOUTH OF SITKA, AND KETCHIKAN
AREA SEEING MOSTLY RAIN. HIGHEST SNOWFALL AMOUNTS SHOULD BE UP
ALONG THE HAINES AND KLONDIKE AREAS, WHILE CENTRAL PANHANDLE
SHOULD ONLY SEE AN INCH OF SNOW OR TWO FOR MONDAY NIGHT INTO
TUESDAY. THIS WEATHER FRONT WILL DISSIPATE ON TUESDAY OVER THE
PANHANDLE.

ON TUESDAY NIGHT, A MUCH STRONGER WEATHER FRONT WILL PUSH TOWARDS
THE OUTER COAST. THIS WEATHER FRONT WILL BRING IN MUCH STRONGER
WARM AIR ADVECTION, AND THE WARM AIR WILL MAKE IT FURTHER INLAND.
HOWEVER, THERE WILL BE ALSO STRONGER VERTICAL MOTION ASSOCIATED
WITH THIS WEATHER FRONT, SO PRECIPITATION RATE WILL BE HIGHER.
WITH HIGHER PRECIPITATION RATE, THERE WILL BE MORE POTENTIAL FOR
EVAPORATIONAL COOLING. THIS WILL ALLOW SNOW TO MIX IN WITH THE
RAIN. RIGHT NOW, THINKING TEMPERATURES SHOULD BE HOVERING IN THE
LOW TO MID 30S WITH RAIN AND SNOW EXPECTED THROUGH THE WEEK. THIS
WILL BE A PRETTY BIG CHANGE COMPARED TO THE SNOWLESS JANUARY MOST
OF THE AREA HAVE SEEN. THE SWEET SPOT FOR SNOW WILL BE IN HAINES,
SKAGWAY, AND THE KLONDIKE AND HAINES HIGHWAYS.

FORECAST CONFIDENCE IS ABOUT AVERAGE. CONFIDENCE IS HIGHER ON THE
GENERAL WEATHER PATTERN, BUT LOWER CONFIDENCE ON THE DETAILS OF
INDIVIDUAL SHORT WAVE DISTURBANCES IMPACTING THE PANHANDLE.
UTILIZE A BLEND OF ECMWF/GEM/NAM IN UPDATING THE FORECAST PACKAGE.
&&

.AVIATION...VFR BEST FLYING FOR A WHILE IN THE SHORT TERM THIS
AFTERNOON/EVE. PESKY FOG TONIGHT SHOULD CAUSE MVFR AT SOME
AERODROMES AND PATCHY LIFR. ANY SIGNIFICANT WIND WILL END FOG.
MORNING CLEAR-OUT SHOULD GO QUICKLY AS THE FRONT APPROACHES.
&&

.MARINE...THINKING 25 KT OR SO AS THE FRONT GETS UP TO THE COAST
MONDAY AFTERNOON. SEAS WILL ALSO BUILD WITH THAT AND THERE IS
ALREADY SOME SWELL OUT THERE. INSIDE PROBLEM MAY BE FOG & WILL
MENTION AS PATCHY. ANY WIND WILL HELP TO PREVENT DENSE FOG.
&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022-036-041>043-051-052.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ053.
&&

JC/RCL

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