Winter Storm Watch 4, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
441 PM AKST THU JAN 19 2012

.SHORT TERM...COMPLEX 955 MB STORM FORCE LOW MOVING OUT OF THE
NORTH PACIFIC TO JUST WEST OF DIXON ENTRANCE WILL BRING A VARIETY
OF WINTER WEATHER THE PANHANDLE STARTING IN THE SHORT TERM.
INCREASING NORTHEAST WINDS THIS EVENING ACROSS THE AREA. CROSS
MOUNTAIN GRADIENTS REACH OVER 20 MB SO KEPT HHW/HHA IN PLACE
ALONG WITH USUAL STORM FORCE GAP FLOW ACROSS NORTHERN. THIS
ACCOMPANIED BY LOW TEMPS PRODUCING LOW WIND CHILLS AND HEAVY
FREEZING SPRAY. NE WIND A BIT LESS ACROSS SOUTHERN HALF BUT STILL
ENOUGH FOR A LOCALLY WIND NEAR INTERIOR PASSES/EXPOSED LOCATION.
DO HAVE A CRITICAL LEVEL NEAR JUNEAU AND STRONG CROSS BARRIER
FLOW SO KEPT HWW FOR TAKU WINDS TONIGHT AND FRIDAY.

 SNOW WILL SPREAD INTO SOUTHERN TONIGHT WITH HEAVIEST AMOUNTS
STARTING UP FRIDAY. EXPECT 1-3 INCHES LATE TONIGHT WITH ANOTHER
6 INCHES ON FRIDAY. FOR SOUTH CENTRAL THERE IS A TIMING ISSUE
BETWEEN MODELS SO LEFT IT AS A WATCH. GFS IS FASTER THAN NAM/EC.
18Z GFS EVEN A BIT FASTER LEAVING DOUBT. BROUGHT IN SNOW TO SOUTH
CENTRAL MID DAY FRIDAY WITH ABOUT 3 INCHES THROUGH THE AFTERNOON.

 FAR NORTH SHOULD JUST SEE INCREASING CLOUDS IN SHORT TERM.

 USED NAM 12 FOR PRES WIND IN GRIDS AND ALL IN AGREEMENT LESS A
SMALL TIMING DIFFERENCE SO OVERALL THERE WERE LITTLE CHANGES.

.LONG TERM...MODELS IN GOOD AGREEMENT ON THE LARGE SCALE PATTERN
THROUGH NEXT WEEK. STRONG UPPER HIGH OVER EASTERN RUSSIA WILL
SLOWLY WEAKEN THERE THROUGH EARLY NEXT WEEK. SOUTHERN STREAM UPPER
TROF WELL S OF THE AKPEN WILL MOVE SLOWLY EAST...AND THEN TURN NE
AS A STRONG TROF DEVELOPS OVER THE FAR WRN GULF OVER THE WEEKEND.
THE STRONG TROF WILL SLOWLY MIGRATE EWD ACROSS THE GULF NEXT WEEK.
THERE ARE SOME DIFFERENCES ON THE SMALLER SCALE WITH LOW PRESSURE
SYSTEMS MOVING INTO THE GULF THROUGH NEXT WEEK. THE GFS AND EC
WERE AT ODDS AS THE EC WAS TRACKING A LOW LIFTING OUT OF THE NORTH
PACIFIC AND SOUTH OF THE AREA NOW THE 12Z RUN TAKES THE LOW UP
ALONG THE COAST OF SE AK LIKE THE GFS. AFTER MON THEY BEGIN TO
DIVERGE. ENDED UP CHANGING THE FORECAST THAT MUCH TROUGH MON AS
THE OVERALL TREND LOOKED GOOD. DID REFRESH THE FORECAST WITH THE
NEW HPC FOR NEXT WEEK.

 BIG CONCERN WILL BE POTENTIAL SIGNIFICANT SNOWFALL AS WELL AS
HIGH WINDS. THE MAIN SNOW THREAT WILL BE OVER THE SRN AREA FRI
NIGHT INTO EARLY SAT AS STRONG OVERRUNNING OF THE ARCTIC AIRMASS
IN PLACE OCCURS AHEAD OF A COUPLE A COMPLEX LOW AND FRONTS MOVING
NE INTO THE SE GULF. A FRONT WILL MOVE OVER THE SOUTHERN HALF OF
SE AK THROUGH FRI NIGHT THROUGH SAT MORNING. THE FRONT WILL
CONTRIBUTE TO THE OVERALL LIFTING ENVIRONMENT AND OVERRUNNING
WILL CONTINUE THROUGH SAT AFTERNOON. GIVEN INTENSITY OF THE ARCTIC AIRMASS
THE LIFT WILL BE RATHER STRONG AS WARM AIR RIDES OVER THE
TOP...THUS POTENTIAL FOR SIGNIFICANT SNOWFALL OVER THE SRN AREA.
HAVE ISSUED WS WARNINGS FOR ZONES 27 THRU 29...AND WATCHES FOR
ZONES 26 AND 23(MAINLY FOR SOUTHERN BARANOF). THE WARNINGS WILL
LAST THROUGH SAT AFTERNOON WITH ZONE 27 AND SOME AREAS OF 28 MIXING
WITH RAIN IN THE AFTERNOON. ZONE 26 AND 23 WILL START A LITTLE
LATER THAN THE OTHER 3 ZONES BUT KEEP SNOW A BIT LONGER. SNOW
AMOUNTS WILL RANGE FROM 8 TO 24 INCHES WITH THE HIGHEST AMOUNTS
NEAR HYDER AND OVER ZONE 23 AND 26.

 FURTHER N...STRONG N-NE WINDS WILL BE THE MAIN ISSUE FRI NIGHT INTO
SAT BUT SNOW WILL GET INTO THE PICTURE LATER SAT INTO SUN
MORNING. THE PRESSURE GRADIENT BETWEEN THE ARCTIC HIGH TO THE N
AND THE LOW MOVING INTO THE SE GULF WILL STRENGTHEN FRI...AND
LOCALLY CONDITIONS WILL BE HIGHLY FAVORABLE FOR A TAKU WIND EVENT
FRI INTO EARLY SAT. HAVE KEPT THE HIGH WIND WATCH FOR ZONES 18
AND 19 FOR FRI MORNING INTO SAT AFTERNOON...AND KEPT HIGH WIND
WARNING GOING FOR ZONE 25 UNTIL EARLY SAT MORNING. AS THE WINDS
BEGIN TO WEAKEN SNOW WILL SPREAD IN FROM THE S LATER SAT INTO SAT
NIGHT. BEST ACCUMULATING SNOW THREAT FOR THE N-CENTRAL AREA WILL
BE SAT NIGHT INTO SUN MORNING AS LOW OVER SE GULF OPENS UP TO A
TROF AS IT MOVES N ACROSS THE PANHANDLE. POSSIBILITY OF HEAVY SNOW
DURING THIS TIME BUT IT IS FAIRLY FAR OUT IN THE FUTURE FOR
ISSUANCE OF ANY WWA THIS EARLY.

 BEYOND SUN...ONSHORE FLOW WILL BE THE RULE MOST OF THE TIME. TEMPS
WILL LIKELY COOL OFF SOME TUE ON OUT AS VERY COLD AIR MOVES IN
FROM THE WEST WITH THE TROF...AND SOME ARCTIC AIR TRIES TO MOVE IN
OVER THE FAR N. COULD LEAD TO MORE SIGNIFICANT SNOW TUE INTO THU
AT THE LEAST.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY
     MORNING FOR AKZ023-026.
         WINTER STORM WARNING FROM 3 AM FRIDAY TO 9 AM AKST SATURDAY FOR
     AKZ027-028.
         STRONG WIND FROM 9 PM AKST THIS EVENING THROUGH FRIDAY AFTERNOON
     FOR AKZ020>022-024.
         HIGH WIND WARNING UNTIL 5 AM AKST SATURDAY FOR AKZ025.
         WINTER STORM WARNING FROM 3 AM FRIDAY TO 4 PM AKST SATURDAY FOR
     AKZ029.
         HIGH WIND WATCH FROM LATE TONIGHT THROUGH SATURDAY AFTERNOON FOR
     AKZ018-019.
         WIND CHILL ADVISORY UNTIL 4 PM AKST SATURDAY FOR AKZ018.
         STRONG WIND FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON FOR
     AKZ017.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ021-034.
         HEAVY FREEZING SPRAY WARNING FOR PKZ022.
         HEAVY FREEZING SPRAY WARNING FOR PKZ011>013-031.
         HEAVY FREEZING SPRAY WARNING FOR PKZ032.
         STORM WARNING FOR PKZ012-013-022-043.
         GALE WARNING FOR PKZ011-021-031>036-041-042-051>053.

&&

MM/ABJ