Gale Warning 20, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
133 PM AKST FRI JAN 2 2009

.SHORT TERM...SATELLITE IMAGERY SHOWS LOW PRESSURE IN THE
NORTHEAST GULF CONTINUING TO BRING IN BANDS OF SNOW OVER THE AK
PANHANDLE AS FRONTAL BANDS ASSOCIATED WITH THE LOW TRACKS NORTH.
BEHIND THE FRONT SHOWERY BANDS APPROACH THE COAST AND BEGIN TO
MERGE TO MORE STRATIFORM PRECIP AS THEY ENCOUNTER PANHANDLE
TOPOGRAPHY. THE SLOW MOVING FRONT WILL KEEP WINTER WEATHER
ADVISORY OVER NIGHT AND INTO TOMORROW FOR THE CENTRAL PANHANDLE
WITH MOST SNOW IN THE PAEL-PAJN CORRIDOR. WITH MOST SNOW DUE TO
THE OVERRUNNING EVENT. LATEST FORECAST QPF VALUES ARE A LITTLE
LOWER...SO BACKED OFF SNOW FOR ZONE 26 OVERNIGHT KEEPING THEM JUT
BELOW ADVISORY LEVELS. SNOW AMOUNTS NEAR 8 INCHES IN 24 HOURS FOR
ZONE 29 BUT FELT IT WAS TOO CLOSE TO PUT OUT AND ADVISORY ATTM
AND WILL LEAVE THAT TO THE NIGHT SHIFT TO RE-EVALUATE. MODERATE
OUTFLOW WINDS OVER MOST OF THE REGION WITH ADVISORY LEVEL WINDS
CONTINUING IN PAGY AND PAYA AND LOCALLY WINDY CONDITIONS OUT OF
INTERIOR PASSES ALONG THE COASTAL MOUNTAINS. WITH THE
WINDS...EXPECTING BLOWING SNOW OVER N AND GALES WINDS IN THE N
INSIDE CHANNELS. WITH HIGH PRESSURE OVER YUKON AND THE LOW
REMAINING IN THE GULF EXPECTING THESE WINDS TO CONTINUE INTO
TOMORROW. WITH COLD ARCTIC AIR REMAINING IN PLACE OVER THE REGION
WITH COLDEST TEMPS ALONG THE N ZONES WITH COLD WIND CHILLS ABOVE
2000 FT IN PAGY. WITH WEAK WARM AIR ADVECTION EXPECTING LITTLE
DIURNAL CHANGE WITH SOME TEMPERATURES RISING THROUGH THE NIGHT.

 UPPER LEVELS TROF CONTINUES TO ELONGATE AND FLATTEN OUT CREATING
SOME UNCERTAINTY IN START AND STOP TIMES OF THE SNOW EVENTS. ALSO
UNCERTAINTY WITH SNOW AMOUNTS AS OVER RUNNING INDEX KEEPS AMOUNTS
HIGHER BUT WITH RELATIVELY LOW QPF GENERATED SOME LOWER SNOW
TOTALS.

 USED A BLEND OF THE GFS40, UKMET, AND INHERITED GRIDS THROUGH
MOST OF THE SHORT TERM. LITTLE CHANGE OCCURRED TO MOST GRIDS WITH
SOME MINOR CHANGES. FORECAST CONFIDENCE IS AVERAGE WITH REMAINING
UNCERTAINTY IN SNOW TOTALS AND EVENT START AND STOP TIMES.

.LONG TERM...
ZONAL FLOW SETS UP ACROSS THE N PAC THROUGH THE WEEKEND. A LOW
WILL MOVE SOUTH OF THE ALEUTIANS AND ACROSS THE N PAC FRI NIGHT
AND SAT...MAKING LANDFALL ALONG THE SOUTHERN PANHANDLE SUN. THE
LOW MOVES INLAND AND INTO B.C. SUN NIGHT/MON MORNING AS A RESIDUAL
LOW REMAINS OVER THE NORTHERN GULF.

MODELS SEEM TO HAVE FAIR AGREEMENT TO THE OVERALL PATTERN AND
TREND. HOWEVER...THEY ARE STILL HAVING A DIFFICULT TIME RESOLVING
TIME AND STRENGTH DIFFERENCES. UPDATED GRIDS WITH THE ECMWF AS IT
INITIALIZED THE CONDITIONS UPSTREAM BEST AS WELL AS BEING THE
PREFERRED MODEL THE LAST COUPLE OF DAYS. FOR PRESSURE...USED A 50/50
BLEND OF 12Z ECMWF AND INHERITED GRIDS THROUGH TUE THEN BLENDED
WITH HPC GUIDANCE BEYOND THAT. MADE ONLY MINOR CHANGES TO THE
OTHER GRIDS.

AS THE LOW TRACKS ACROSS THE N PAC SAT AND SUN...EXPECT STRONGEST
WINDS TO REMAIN SOUTH OF THE FORECAST AREA. WAVES EXPECTED TO REMAIN
AT SMALL CRAFT LEVELS ACROSS THE SOUTHERN OUTER WATERS AND
GRADUALLY SPREAD NORTHWARD AS WESTERLY SWELL MOVES IN BEHIND THE
LOW. PRECIP TYPE WILL BE A MIX OF SNOW AND RAIN ACROSS THE
SOUTHERN ZONES WITH ALL SNOW NORTH OF FREDERICK SOUND. A WEAK
RIDGE WILL MOVE ACROSS THE N GULF THROUGH THE MIDDLE OF NEXT WEEK
WITH A LONG WAVE TROUGH LOOKING TO SET UP ACROSS THE ALEUTIANS BY
THE END OF NEXT WEEK. KEPT CHANCE OF PRECIP ACROSS SE AK THROUGH
MIDDLE OF NEXT WEEK THEN GRADUALLY INCREASED IT AS SW FLOW
INCREASES TOWARDS THE END OF NEXT WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 6 AM AKST SATURDAY FOR
AKZ021-024.
 WINTER WEATHER ADVISORY UNTIL 12 PM AKST SATURDAY FOR
AKZ025.
  WINTER WEATHER ADVISORY UNTIL 9 PM AKST THIS EVENING FOR
        AKZ020-022.
 WIND ADVISORY UNTIL 6 PM AKST SATURDAY FOR AKZ017-018.
  WIND CHILL ADVISORY UNTIL 6 PM AKST SATURDAY FOR AKZ018.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011>013.
  GALE WARNING FOR PKZ011-012-022-051.
  SMALL CRAFT ADVISORY FOR PKZ013-021-031>036-041>043-052.

PRB/MAM