Gale Warning 409, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1242 PM AKST TUE DEC 2 2008

.SHORT TERM...COLD MERCURY READINGS WOKE UP THE PANHANDLE THIS
MORNING. SATELLITE LOOP SHOWS MID TO HIGH CLOUD SHIELDS SPREADING
SOUTHEAST AND FILTERING SUNSHINE ACROSS THE AREA. UNDER A STRONG
CONTINENTAL HIGH...MID TO UPPER LEVEL RIDGE CONTINUES ACROSS THE
EASTERN GULF AND SOUTHEAST ALASKA WITH DRY CONDITIONS AND
MODERATE OFFSHORE FLOW. NORTHERLY GRADIENT CONTINUES TO ENHANCE
OVER SKAGWAY AND HAINES AREA. MODELS ARE IN FAIR AGREEMENT FOR
THE SHORT TERM PERIODS AND WILL BLEND THE INHERITED GRIDS WITH
THE NAM TO MAXIMIZE THE CONTINUITY.

 AS THE HIGH MOVES A LITTLE MORE TO THE EAST...NORTHERLY PRESSURE
GRADIENT WILL INCREASE OVER THE NORTHERN PANHANDLE THROUGH THIS
EVENING...THEN EXTEND SOUTH TO THE EASTERN CENTRAL PANHANDLE
TONIGHT. ADVISORY LEVEL WINDS ARE EXPECTED OVER SKAGWAY...HAINES
AND JUNEAU AREAS WITH WIND CHILL AROUND 20 BELOW NEAR WHITE PASS
TONIGHT. COLD AIR OUTFLOW WILL CONTINUE TO GENERATE FREEZING
SPRAY FOR NORTHERN LYNN CANAL TONIGHT. ADVISORY LEVEL WINDS WILL
SPREAD SOUTH TO INCLUDE HYDER AREA LATE TONIGHT. GUSTY WINDS OUT
OF INTERIOR PASSES WILL CONTINUE ACROSS THE CENTRAL INSIDE
PASSAGES. THESE CONDITIONS WILL IMPROVE BY WEDNESDAY AFTERNOON.
MID TO HIGH CLOUDINESS WILL INCREASE ACROSS THE AREA TONIGHT.
HOWEVER...LIMITED MOISTURE FIELD UNDER THE RIDGE...EXPECT
CONTINUED DRY CONDITIONS TONIGHT AND WEDNESDAY.

 &&

.LONG TERM...LONG WAVE RIDGE OVER THE GULF CONTINUES TO ADVECT
EAST THROUGH THE WEEKEND AND THEN FLATTENS AS THE LONG WAVE
PATTERN TRANSITIONS. WITH THE TROUGH MOVING OVER THE ALEUTIANS
AND OVER THE PANHANDLE THROUGH THE WEEK. NEXT BAND OF PRECIP
ASSOCIATED WITH THE SURFACE LOW OVER THE ALEUTIANS MOVING INTO
THE N PANHANDLE WED AFTERNOON IN TO THURS MORNING IS THE
QUESTION. GRIDS HAVE THIS EVENT AS A SIGNIFICANT SNOW EVENT FOR
ZONES 17-21 AND 25. WITH THE COLD AIR CURRENTLY OVER THE REGION
EXPECTING PRECIP TO START AS SNOW, WITH THE WAA FROM THE SOUTH
SHOULD SEE A TRANSITION TO RAIN. WHEN THE TRANSITION OCCURS WILL
DETERMINE IF THIS GETS TO WARNING CRITERIA. AT THIS TIME PUTTING
OUT A WINTER WEATHER ADVISORY FOR ZONE 17 AND HOLDING OFF ON THE
REST DUE TO UNCERTAINTY WITH IN PERIOD 3. KEPT THE GRID SNOW
AMOUNTS THE SAME BUT WILL BACK OFF AMOUNTS IN THE TEXT. NAM AND
GFS BRINGING THE PRECIP A BIT SLOWER THE ECMWF. PAYA GFSBFR
SOUNDINGS KEEP TEMPERATURES BELOW FREEZING UNTIL 6 Z THURS WITH
PAGY TRANSITIONS AROUND 3 Z WED AND PAJN TRANSITION AROUND 18 Z
WED.

MODELS INITIALIZED FAIRLY WELL AND WERE IN GOOD AGREEMENT UP TO
DAY 3. USED A BLEND OF 12Z NAM12 UP TO DAY 4 AND THEN A BLEND OF
HPC GUIDANCE WITH GFS AND ECMWF OUT TO DAY 7. MODEL RUNS DIVERGED
BUT THERE WAS SOME AGREEMENT BETWEEN THE NEWER RUNS. HPC GUIDANCE
LEANED MORE TOWARD THE GFS WHICH WAS A CHANGE FROM PREVIOUS RUNS.
WITH THE NEW BLEND DAY 6 AND DAY 7 GRIDS WERE SIGNIFICANTLY
CHANGED FROM THE INHERITED BUT ARE NOW MORE IN LINE WITH LAST
MODELS. DO EXPECT DAY 7 TO CHANGE AGAIN.

FORECAST CONFIDENCE FOR MOST OF THE REGION OUT TO DAY 4 IS
AVERAGE, WITH BELOW AVERAGE CONFIDENCE REGARDING THE DURATION OF
THE SNOW EVENT. AFTER DAY 4 CONFIDENCE IS ALSO LOW DUE TO THE
CHANGES BETWEEN MODEL RUNS AND HPC GUIDANCE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 6 PM THIS EVENING TO 9 AM AKST
WEDNESDAY FOR AKZ025. WIND ADVISORY FROM 6 PM THIS EVENING TO
MIDNIGHT AKST TONIGHT FOR AKZ019. WIND ADVISORY FROM 6 PM THIS
EVENING TO 6 AM AKST WEDNESDAY FOR AKZ018. WIND ADVISORY FROM 3
AM TO 9 AM AKST WEDNESDAY FOR AKZ029. WINTER WEATHER ADVISORY
FROM 1 PM WEDNESDAY TO 1 AM THURSDAY FOR AKZ017
MARINE...GALE WARNING FOR PKZ012. SMALL CRAFT ADVISORY FOR
PKZ011-013-031-035-041>043-051-052.

&&

SJA/PRB