Gale Warning 27, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
348 PM AKST SUN JAN 6 2013

.SHORT TERM...SATELLITE IMAGERY SHOWING A 968 MB LOW APPROACHING
KODIAK WITH THE ASSOCIATED OCCLUDED FRONT MOVING ACROSS THE
EASTERN GULF AND APPROACHING THE AK PANHANDLE. RIDGE OF HIGH
PRESSURE CURRENTLY OVER THE PANHANDLE IS EXITING TO THE EAST AS
THE FRONT APPROACHES. THE FRONT WILL MOVE OVER THE PANHANDLE
TONIGHT WEAKENING BY MONDAY AFTERNOON AS A RIDGE BUILDS OVER THE
PANHANDLE. MEANWHILE THE LOW WILL LINGER NEAR KODIAK WEAKENING TO
978 MB. PRECIPITATION WILL INCREASE THROUGH THE EARLY EVENING
WITH HIGHEST INTENSITY LATER TONIGHT. PRECIP WILL CHANGE TO
SHOWERS POST FRONTAL AS COLDER AIR MOVES IN ALOFT. SOME HIGHER
CAPE VALUES IN THE GULF FOR MONDAY INDICATING POSSIBILITY OF
THUNDERSTORMS BUT FOR NOW REGION POST FRONTAL DOES NOT LOOK
HIGHLY CONVECTIVE ON SATELLITE. THE RAIN SNOW LINE HAS BEEN
TRICKY TODAY AS THE SOUTHERLY WINDS INCREASED TEMPERATURES TO THE
MID TO UPPER 30S FOR RAIN WHILE DEW POINTS WERE STILL NEAR
30 ALLOWING A SNOW MIX. TEMPERATURES WILL FLUCTUATE OVERNIGHT BUT
OVERALL TREND WILL BE LOWERING TO THE UPPER 20S TO LOW
30S...RESULTING IN A TRANSITION TO SNOW. SNOW AMOUNTS FOR AREAS
NORTH OF FREDERICK SOUND ONLY EXPECTED TO BE 1 TO 2 INCHES
OVERNIGHT WITH 1 TO 3 INCHES FOR YAKUTAT AND HAINES. PRECIP WILL
TRANSITION BACK TO RAIN THROUGH MONDAY AS TEMPERATURES INCREASE
TO THE MID TO UPPER 30S.

 WITH THE APPROACHING FRONT WINDS SHOULD INCREASE RAPIDLY THIS
EVENING WITH GALES ALONG THE COASTAL WATERS. WINDS OVER THE
PANHANDLE WILL INCREASE WITH THE PASSING FRONT WITH SOME HIGHER
GUSTS LATER TONIGHT. BUT AS THE FRONT IS SHOWING SIGNS OF
SHEARING APART THESE GUSTS MAY NOT BE THAT STRONG. WITH THE
EXITING RIDGE WINDS OVER THE NORTHERN PANHANDLE MAY SEE A SHIFT
THIS EVENING BEFORE RETURNING TO THE SOUTH AS PRESSURE GRADIENT
BECOMES PARALLEL WITH THE FRONT THEN RETURNS TO A NORTH- SOUTH
GRADIENT WITH THE INCOMING RIDGE ON MONDAY.

 THERE WERE ENOUGH DIFFERENCES AMONG THE MODELS WITH THE TIMING
OF THE FRONT TO LOWER FORECAST CONFIDENCE. ECMWF WAS THE FASTEST
WITH THE FRONT WHILE THE GFS WAS THE SLOWEST. NAM LOOKED TO BE A
GOOD COMPROMISE FOR THE FRONTAL LOCATION...HOWEVER WAS FARTHER TO
THE EAST WITH THE POSITION OF THE KODIAK LOW THAN THE ECMWF OR
GFS. USED SOME NAM TO REFRESH GRIDS BUT OVERALL CHANGES WERE
MINOR. MAIN ISSUES WERE THE PRECIP TYPE AND TIMING OF INCREASING
WINDS THIS EVENING. FORECAST CONFIDENCE IS ABOVE AVERAGE.

 &&

.LONG TERM...A LOW VICINITY KODIAK ISLAND AT THE BEGINNING OF THE
EXTENDED RANGE FORECAST PERIOD WILL DRIFT TO THE SOUTHEAST ON
TUESDAY WHILE SLOWLY WEAKENING. A DEVELOPING WAVE WILL TRACK
RAPIDLY TO THE NORTHEAST WHILE DEEPENING AND IT LOOKS LIKE SOME OF
THE ENERGY FROM THE KODIAK LOW WILL BE TRANSFERRED TO THE
DEVELOPING WAVE. THIS WAVE IF FORECAST TO REMAIN WELL SOUTH OF THE
PANHANDLE AND MODELS ALL IN GOOD AGREEMENT ON THIS POINT, AS WELL
AS BUILDING IN AN INVERTED TROUGH AFTER THE KODIAK LOW HAS BEEN
ABSORBED INTO THE DEEPER WAVE CIRCULATION.

SURFACE RIDGING OVER THE EASTERN GULF AND WESTERN CANADA ON
THURSDAY WILL SHIFT EAST AND SLIGHTLY SOUTH IN ADVANCE OF A DEEP
LOW OVER THE NORTHERN GULF BY THURSDAY AFTERNOON. MODELS IN FAIR
AGREEMENT ON THE LOCATION OF THIS FEATURE THROUGH LATE WEEK, BUT
DIFFER SIGNIFICANTLY ON STRENGTH. OPTED TO TAKE ADVANTAGE OF HPC AND
THE ENSEMBLE MEANS INCLUDED IN THEIR GRIDS FOR THE LATTER PORTION
OF THE EXTENDED RANGE.

SHOWER ACTIVITY WILL BE DIMINISHING THROUGH THE DAY TUESDAY WITH
WEDNESDAY CURRENTLY LOOKING LIKE A DRY AND PARTLY CLOUDY DAY OVER
MOST, IF NOT ALL, OF SOUTHEAST ALASKA. A FRONT RE-ENTERS THE
PICTURE FROM THE WEST ON THURSDAY. LIMITED POPS TO LIKELY THROUGH
THIS TIME OWING TO THE UNCERTAINTY OF THE STRENGTH OF THE SYSTEM
TOUCHED ON IN THE PRECEDING PARAGRAPH. RESULTING TEMPS AND QPF
PRODUCED SNOW OVER MANY ZONES, BUT NO ADVISORY AMOUNTS.

MODEL GUIDANCE OFFERING SOME VERY LARGE CHANGES WITH REGARD TO
OVERNIGHT LOW TEMPS FOR THE UPCOMING WEEK WITH ALL OF THE DELTAS
BEING COLDER TEMPS BROUGHT TEMPS DOWN, BUT GENERALLY USED HALF OR
LESS OF THE MODEL DIFFERENCE IN ORDER TO KEEP THE FORECAST FROM
BECOMING TOO ABRUPT. CHANGES TO DAYTIME HIGHS A LITTLE MORE OF A
MIXED BAG OF BOTH WARMER AND COLDER AT DIFFERENT TIMES AND IN
DIFFERENT PLACES BUT MUCH SMALLER DELTAS.

USED A BLEND OF ECMWF AND GEM EARLY ON, THEN BLENDED IN MORE AND
MORE OF THE HPC FOR PRESSURE AND WINDS. POPS BLENDED FROM ECMWF,
GFS, AND GEM. QPF DERIVED FROM ECMWF. TEMPS ADJUSTED USING BIAS
CORRECTED MOS THROUGH DAY 5 AND GFS ENSEMBLE THEREAFTER. SNOW
LEVELS ADJUSTED WITH GFS40. FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ022-036-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ021-033>035-041-042.

&&

PRB/FRITSCH