Small Craft Advisory 62, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
255 PM AKST SUN JAN 22 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS A LOW PRESSURE
SYSTEM LIFTING NNE THROUGH HECATE STRAIT. THIS FEATURE WILL
CONTINUE TO TRACK NNE BUT DRIFT INTO BC THIS EVENING. THERE IS A
BROAD AREA OF LOW PRESSURE OVER THE NORTHWEST GULF WITH SHOWERS
ROTATING AROUND THE GULF AND OVER THE NORTHERN HALF OF THE
PANHANDLE. MOST OF THE SNOW SHOWER OVER THE INNER CHANNELS WILL
CONTINUE TO DIMINISH LATE THIS AFTERNOON INTO THE EVENING HOURS
AS THE STEERING FLOW BACKS AROUND DRIFT THE SHOWERS ALONG THE
COASTLINE AND ALONG WITH INCREASING OFFSHORE FLOW AS THE LOW OVER
THE SOUTHERN AREAS LIFTS NORTH.

 THERE IS SOME STRONGER SHOWERS OVER THE FAR NORTHERN INNER
CHANNELS ATTM BUT AS THE UPPER LEVEL DYNAMICS LIFTS NORTH THE
SHOWERS SHOULD DISSIPATE EARLY THIS EVENING. SNOW ACCUMULATIONS
OVER THE NORTHERN HALF OF THE PANHANDLE WILL RANGE FROM 1 TO
3 INCHES BUT WITH PAYA IN A BETTER TRAJECTORY FOR THE SHOWERS
THEY COULD SEE 2 TO 4 INCHES THROUGH TONIGHT. THE SOUTHERN AREAS
WILL SEE RAIN OVER THE FAR SOUTHERN AREAS AS THEY FEEL THE
EFFECTS OF THE LOW MOVING THROUGH HECATE STRAIT. THE WINDS ACROSS
THE AREA ARE MOSTLY FROM THE SOUTH BUT THEY WILL BACK AROUND TO
THE NORTH THIS EVENING TO BE AROUND 15 KT LATE TONIGHT. THE FAR
NORTHERN AREAS WILL SEE THE WINDS COME UP TO 20 KT AS THE PRESSURE
GRADIENT TIGHTENS.

 A TROF OF LOW PRESSURE WILL ROTATE AROUND THE PARENT LOW AND
DRIFT INTO THE EASTERN GULF LATE TONIGHT AND THROUGH MON. THIS
WILL INCREASE THE EASTERLY WINDS IN E/W CHANNELS WITH SMALL CRAFT
WINDS NEAR CROSS SOUND AND OVER THE NORTHERN GULF. SHOWERS WILL
INCREASE FROM SOUTH TO NORTH THROUGH THE DAY WITH THE FAR
SOUTHERN AREAS MIXING WITH SNOW AND RAIN AT TIMES WITH THE
NORTHERN TWO THIRDS SEEING FROZEN PRECIP. SNOW AMOUNTS WILL BE
NOT BE THAT MUCH BUT THE INNER CHANNELS COULD SEE 1-3 INCHES TO A
BIT MORE OVER THE NORTHERN GULF WITH 2-4 THROUGH THE DAY.

 THERE IS ABOUT AVERAGE FORECASTER CONFIDENCE AND USED A BLEND OF
THE 12Z GFS/EC FOR THE SHORT TERM FORECAST.

&&

.LONG TERM...LONG RANGE MODELS ARE IN GOOD AGREEMENT LOOKING FOR
STORMY WEATHER PATTERN FOR THE MOST OF THIS WEEK ACROSS THE
EASTERN GULF AND SOUTHEAST ALASKA. THE OVERNIGHT RUN OF ECMWF HAS
SHOWN A BETTER AGREEMENT WITH THE GFS FOR THE STORM TRACKS
ALTHOUGH THE ECMWF STILL KEEPS A STRONGER INTENSITY AT THIS TIME.
BLENDED THE FORECAST PACKAGE WITH THE GFS AND ECMWF THROUGH LATE
WEDNESDAY. WITH A MEAN UPPER TROUGH AND LOW IN THE GULF...A SERIES
OF SURFACE LOWS AND TROUGHS WILL SWING ACROSS THE EASTERN GULF AND
THE PANHANDLE. ONE OF THE STRONGER STORM IS EXPECTED TO ONSET FOR
SIGNIFICANT SNOWFALL TUESDAY NIGHT INTO EARLY WEDNESDAY OVER THE
NORTHERN AND CENTRAL PANHANDLE ALONG WITH A STRONG WINDS ACROSS
THE SOUTHERN COASTAL SECTIONS.

 MODELS STAY IN GOOD AGREEMENT THROUGH THURSDAY WITH A WEAKENING
LOW IN THE NORTHERN GULF COAST AND A HIGH PRESSURE AREA FAR SOUTH
IN THE EASTERN PACIFIC. THEN NOTICEABLE MODEL DIFFERENCES ARE
GROWING WITH A STORM MOVING NORTHEASTWARD ACROSS THE WESTERN GULF.
THE ECMWF STILL HOLDS A STRONG RIDGE OVER THE EASTERN PACIFIC BUT
THIS TREND BECOMES MORE IN LINE WITH THE PREVIOUS RUNS OF THE GFS.
FROM THURSDAY ONWARD...USED THE HPC OUTPUTS. A SERIES OF WEAKER
LOWS AND TROUGHS WILL CONTINUE MOVE ACROSS THE FORECAST DOMAIN
THROUGH LATE THURSDAY AS A LOW IN THE NORTHWESTERN GULF WEAKENS.
WITH A LOW PREDICTABILITY...ANOTHER STORM WILL MOVE NORTH ACROSS
THE EASTERN GULF THROUGH EARLY SATURDAY MORNING. THIS SYNOPTIC
SETUP WILL BRING ANOTHER SIGNIFICANT SNOWFALL SCENARIO ACROSS THE
NORTHERN PANHANDLE FOR FRIDAY INTO FRIDAY NIGHT.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING UNTIL 4 PM AKST THIS AFTERNOON FOR
     AKZ017>019.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-035-036-043-051-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

ABJ/AHN