Gale Warning 422, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
628 AM AKST SAT DEC 21 2013

.SHORT TERM...A COMPLEX WEATHER FRONT IS HEADED TOWARD THE
PANHANDLE. PRECIP ALONG A PRE-FRONTAL TROUGH WILL CAUSE SOME
LIGHT SNOW OVER THE NORTH COAST TODAY THEN THE MAIN FRONT WILL
MOVE INTO THE SOUTHERN OUTER COAST LATER THIS AFTERNOON. EXPECT
PRECIP TO SPREAD OVER THE REST OF THE PANHANDLE THROUGH THE
EVENING. BIGGEST FORECAST CHALLENGE WITH THIS FRONT IS THE
RAIN/SNOW LINE AND TEMPERATURES. THE SYSTEM WILL BE BRINGING IN
MUCH WARMER AIR ALOFT...MEANWHILE THE NORTHERN HALF OF THE AREA
WILL REMAIN UNDER NORTHERLY OUTFLOW WITH TEMPERATURES STARTING
OFF THIS MORNING IN THE SINGLE DIGITS ALONG THE HAINES HIGHWAY
AND IN THE MENDENHALL VALLEY. THIS WILL RESULT IN YET ANOTHER
OVERRUNNING SNOW EVENT. LOCATIONS AT THE RAIN/SNOW INTERFACE MAY
SEE A PERIOD OF FREEZING RAIN BEFORE THE TEMPERATURES RISE ABOVE
FREEZING. ONLY WENT WITH A SLIGHT CHANCE IN THE FORECAST BECAUSE
CONFIDENCE IN THE DURATION AND HOW WIDESPREAD IT WILL BE IS LOW.
SNOWFALL AMOUNTS WILL BE GREATEST IN JUNEAU AND HAINES WHERE A
WINTER WEATHER ADVISORY HAS BEEN ISSUED THIS MORNING. EXPECT
JUNEAU TO START TO MIX WITH RAIN LATE SATURDAY NIGHT AS WINDS
SHIFT SE...BUT THE NORTHERN HIGHWAY AND INNER VALLEY AREAS WILL
STAY SNOW LONGER. EXPECT 4-6 INCHES THROUGH SATURDAY NIGHT THEN
BE MAINLY RAIN SUNDAY MORNING...THEN THERE MAY BE A MIX AGAIN
SUNDAY AFTERNOON ONCE THE FRONT PASSES. IN HAINES THE NORTHERLY
WINDS WILL LAST LONGER...SO THE SNOW WILL TOO. THAT ADVISORY GOES
INTO SUNDAY EVENING WITH ABOUT 2-6 INCHES EVERY 6 HOURS WITH A
TOTAL OF 9-16 INCHES FROM THIS EVENING THROUGH SUNDAY EVENING.
THE CENTRAL PANHANDLE AND ALONG THE COASTAL MOUNTAINS WILL SEE A
COUPLE INCHES WITH THIS EVENT BUT EXPECT THOSE AREAS TO CHANGE
OVER TO RAIN A BIT SOONER THAN THE ADVISORY AREAS.

 WINDS WILL PICK UP TO GALE FORCE WITH THE FRONT AS IT MOVES INTO
THE EASTERN GULF. HAVE STRONG WIND HEADLINES FOR THE SITKA AND
ELFIN COVE AREAS THIS EVENING. AS THE FRONT MOVES INLAND THE
CENTRAL INSIDE WATERS WILL INCREASE 25-30KT WITH CLARENCE STRAIT
AND CROSS SOUND REACHING 40KT. ONCE THE FRONT PASSES WINDS WILL
SHIFT TO THE WEST. EXPECT THE INNER AREAS LIKE JUNEAU TO SEE THAT
WIND SHIFT LATE SUNDAY AFTERNOON.

 BLENDED THE INHERITED FORECAST WITH THE NAM12 THEN ADJUSTED WIND
SPEEDS UP WITH THE FRONT. FOR TEMPERATURES WENT WITH A GRADUAL
INCREASE FROM THIS AFTERNOON THROUGH SUNDAY AFTERNOON.

 &&

 .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY NIGHT/...ACTIVE WEATHER
PATTERN CONTINUES THROUGH NEXT WEEK.

 SHOWERS LEFT OVER FROM THE WEEKEND EVENT WILL STILL BE IN THE
AREA AT THE BEGINNING OF THE EXTENDED RANGE FORECAST PERIOD
SUNDAY NIGHT. A PROGRESSIVE SURFACE RIDGE WILL BUILD IN FROM THE
SOUTH OVER THE GULF AND MOVE EAST OVER SOUTHEAST ALASKA ON
TUESDAY, DRYING OUT THE LAST OF THE SHOWER ACTIVITY. THE BREAK
WILL BE BRIEF, AS THE NEXT FRONT SHOVES THE RIDGE OUT OF THE WAY
TO THE EAST AND APPROACHES THE OUTER COAST ON THE AFTERNOON OF
CHRISTMAS EVE. GFS AND ECMWF IN FAIRLY GOOD AGREEMENT ON THE
TIMING OF THIS NEXT FRONT, WITH ECMWF BEING SLIGHTLY FASTER.
PRECIP FROM THIS FRONT WILL BE HEAVY AT TIMES ON CHRISTMAS DAY
ALONG THE CENTRAL OUTER COAST AND SOUTHERN INNER CHANNELS. THE
FRONT IT SELF WILL PASS TO THE EAST BY THURSDAY MORNING, BUT A
DEVELOPING WAVE ALONG THE FRONTAL BOUNDARY WILL KEEP
PRECIPITATION LIKELY THROUGH FRIDAY MORNING BEFORE TAPERING OFF.

 TEMPERATURES WERE THE BIGGEST FORECAST CHALLENGE OVERNIGHT, AS
THEY HAVE TREMENDOUS IMPACT ON SNOW LEVELS AND PRECIPITATION
TYPE. TABULAR GUIDANCE STARTS OFF OUT OF SYNC WITH REALITY, BEING
SIGNIFICANTLY WARMER THAN WHAT IS DEPICTED IN GRAPHICAL MODELS.
OPTED TO FOLLOW GRAPHICAL MODEL DATA EARLY ON AND USED 850 MB
TEMPS AS A BENCHMARK TO CHANGES MADE. MOS MORE IN STEP WITH
GRAPHIC BY NEXT TUESDAY. USED A COMBINATION OF BIAS CORRECTED
GFS40 AND MOS FROM THEN ON. POP AND QPF ARE A BLEND OF GFS, GEM,
AND ECMWF. OVERALL FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM AKST
     SUNDAY FOR AKZ025.
         STRONG WIND FROM 6 PM AKST THIS EVENING THROUGH THIS EVENING FOR
     AKZ022-023.
         WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 9 PM AKST
     SUNDAY FOR AKZ019.
MARINE...GALE WARNING FOR PKZ022-036-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011-021-031>035-041-042-053.

&&

FERRIN/FRITSCH