Gale Warning 147, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1121 AM AKDT SAT MAR 14 2009

.SHORT TERM...SATELLITE THIS MORNING REVEALS A VERY STRONG UPPER
LEVEL JET WELL SOUTH OF THE PANHANDLE WITH A MID LEVEL LOW NEAR
THE CHARLOTTES. THE ASSOCIATE SURFACE LOW IS WEST OF DIXON
ENTRANCE AND A WEAK FRONTAL BOUNDARY IS NOW ADVECTING NORTHWARD
ACROSS THE SOUTHERN PANHANDLE BRINGING PERIODS OF LIGHT SNOW AND
FLURRIES. THE REST OF THE PANHANDLE CONTINUES TO SEE MOSTLY
CLOUDY SKIES AS NORTHERLY WINDS INCREASE AT THE SURFACE TO 850 MB
WITH THE BUILDING SURFACE HIGH ACROSS INTERIOR ALASKA. LOCALLY
BREEZY CONDITIONS ARE LOCATED ACROSS THE SOUTHERN PANHANDLE AS A
40 KNOT 850 MB LLJ REMAINS THERE ASSOCIATED WITH THE WEAK FRONTAL
BOUNDARY. ELSEWHERE EAST-WEST ORIENTED CHANNELS ARE ALSO SEEING
LOCALLY BREEZY CONDITIONS AS THE PRESSURE GRADIENT INCREASES
BETWEEN THE 985 MB SURFACE LOW NEAR DIXON ENTRANCE AND THE
SURFACE HIGH LOCATED ACROSS THE NORTHWEST TERRITORIES.

FOR TONIGHT WILL CONTINUE TO SEE A MIX OF LIGHT SNOW AND RAIN
ACROSS THE SOUTHERN PANHANDLE AS THE WEAK FRONTAL BAND ADVECTS
NORTHWESTWARD AND DISSIPATES NORTH OF FREDERICK SOUND. SNOW
ACCUMULATION AMOUNTS ARE EXPECT TO BE LESS THAN AN INCH AS ALL THE
BEST UPPER LEVEL DYNAMICS REMAIN WELL SOUTH OF THE PANHANDLE
THROUGH THE SHORT TERM. WITH THE SOUTHEASTERLY PARCEL TRAJECTORIES
FROM 500 MB TO 850 MB AND NORTHERLY WINDS FROM 850 MB TO THE
SURFACE IT WILL BE DIFFICULT FOR PRECIP TO MAKE IT AS FAR NORTH AS
THE ICY STRAIT CORRIDOR...HOWEVER COULD SEE A FEW FLURRIES LATE
TONIGHT. DOWNSLOPE WINDS NEAR PAYA AND PAGY WILL KEEP THOSE AREAS
PARTLY TO MOSTLY CLOUDY TONIGHT. AS THE SURFACE PRESSURE GRADIENT
INCREASES TONIGHT WITH THE BUILDING SURFACE HIGH ACROSS INTERIOR
ALASKA EXPECT THE CROSS BARRIER FLOW TO INCREASE NEAR DOWNTOWN
JUNEAU. WITH THE INVERSION HEIGHT LOCATED IN A FAVORABLE LOCATION
THROUGH TOMORROW AFTERNOON EXPECT WIND ADVY GUSTS WITH TAKU WINDS
NEAR DOUGLAS. ALSO WITH THE STRENGTHENING NORTHERLY SURFACE
PRESSURE GRADIENT EXPECT LOCALLY WINDY CONDITIONS NEAR OUTFLOW
REGIONS WITH WIND ADVY GUSTS EAST OF YAKUTAT AND NEAR SKAGWAY WITH
GALES IN ASSOCIATED MARINE WATERS.

FOR TOMORROW ANOTHER WEAK FRONTAL BAND ATTEMPTS TO ADVECT
NORTHWARD ACROSS THE PANHANDLE ASSOCIATED WITH A WEAK DEFORMATION
FEATURE AT MID LEVELS. HOWEVER THIS WEAK FRONTAL BAND WILL ALSO
QUICKLY WEAKEN AS IT MOVES NORTH OF FREDERICK SOUND SO EXPECT THE
MAJORITY OF THE SNOW AND RAIN TO AGAIN BE LOCATED ACROSS THE
SOUTHERN PANHANDLE. THE HIGHEST SNOWFALL AMOUNTS TOMORROW WILL BE
ACROSS EASTERN BARANOF ISLAND WHERE THE LOW LEVEL UPSLOPE FLOW
COULD INCREASE SNOWFALL AMOUNTS. LOCALLY WINDY CONDITIONS WILL
CONTINUE NEAR OUTFLOW REGIONS WITH WIND ADVY GUSTS NEAR SKAGWAY,
EAST OF YAKUTAT, AND DOWNTOWN JUNEAU...AS THE TAKU WINDS WILL
CONTINUE. FORECAST CONFIDENCE REMAIN ABOVE AVERAGE THROUGH THE
SHORT TERM PERIOD.

.LONG TERM...MODELS IN GOOD LARGE SCALE AGREEMENT THROUGH
MIDWEEK...THEN BEGIN TO DIVERGE LATE NEXT WEEK. A FAIRLY SHARP
RIDGE WILL DOMINATE THE BERING SEA...WHILE A TROF WILL REMAIN OVER
THE GULF OF AK THROUGH MIDWEEK. MAIN CONCERN WILL BE TIMING
SHORTWAVES IN THIS FLOW...AND THERE ARE SOME MODEL DIFFERENCES
THERE. FOR SIMPLICITY...BASICALLY STUCK WITH THE CURRENT PRESSURE
GRIDS AS THEY WERE A GOOD COMPROMISE AMONGST THE MODEL CHOICES
THROUGH MIDWEEK. DID TWEAK POPS SOME BLENDING IN THE NEWER MODELS
WITH THE CURRENT GRIDS...WITH THE MAIN CHANGE BEING TO REDUCE
POPS OVER THE N. THE E-SE FLOW IS NOT FAVORABLE FOR MUCH OTHER
THAN FLURRIES/SPRINKLES OR INTERMITTENT LIGHT PRECIP OVER THE N.
PERSISTENT LOW PRESSURE OVER THE GULF WILL KEEP OUTFLOW WINDS GOING
THROUGH THE NE GULF COAST PASSES AND BAYS...AND ADDED THOSE WINDS
IN FOR SUN NIGHT THROUGH TUE. WILL BE EXTENDING THE SHORT TERM
WIND ADVYS FOR PAGY AND PAYA ZONES UNTIL 6 AM MONDAY...WITH
FURTHER EXTENSIONS LIKELY DURING LATER SHIFTS.

AS FOR THE LATE WEEK PERIOD...MODELS DID NOT SUPPORT THE STRONGER
LOW THAT WAS IN THE GRIDS BUT GIVEN THE MODEL DIVERGENCE THAT FAR
OUT...DECIDED AGAINST CHANGING THAT TIME FRAME. THIS WAS
COORDINATED WITH WFO PAFC WHO DID NOT CHANGE THEIR LONGER RANGE
PERIODS EITHER.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 10 PM THIS EVENING TO 3 PM AKDT SUNDAY FOR
     AKZ025.
         WIND ADVISORY FROM 3 AM SUNDAY TO 6 AM AKDT MONDAY FOR AKZ017-
     018.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ011-013-022-033-035-036-041>043-051.

PSS/RWT