Small Craft Advisory 229, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
303 PM AKDT WED MAR 28 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS A WEAKENING
WEATHER SYSTEM LIFTING OVER SE AK THIS AFTERNOON. THIS SYSTEM IS
PRODUCING PERIODS OF RAIN OVER THE SOUTHERN HALF OF THE FORECAST
AREA. THE SURFACE LOW IS PRODUCING A FAIRLY TIGHT PRESSURE
GRADIENT AND IS INDUCING GUSTY WINDS TO 35 MPH OVER THE FAR
SOUTHERN AND CENTRAL AREAS. THE NORTHERN HALF IS UNDER CLOUDY
SKIES BUT AS THE WEAKENING FRONT MOVES OVER THE AREA THIS EVENING
THERE WILL BE A CHANCE OF SOME LIGHT PRECIP. THE WINDS OVER THE
NORTHERN HALF ARE ON THE LIGHT SIDE WITH 15 TO 20 KT OVER THE
MARINE WATERS. THE LOW IS PRODUCING A SMALL AREA OF GALE FORCE
WINDS OVER THE FAR SE GULF WITH GENERALLY 25KT FROM ESE OVER THE
REST OF THE GULF.

 THE THREAT OF PRECIP OVER THE SOUTHERN AREAS WILL REMAIN HIGH
THROUGH TONIGHT. THE CENTRAL AND NORTHERN AREAS WILL SEE THE
THREAT OF PRECIP DECREASE AS THE UPPER LEVEL SUPPORT FROM THE
SYSTEM CURRENTLY OVER THE AREA WEAKEN AND MOVE OFFSHORE.

 A STRONGER SURFACE LOW WILL MOVE OUT OF THE NORTH PACIFIC LATE
TONIGHT AND INTO THE SOUTHERN GULF THROUGH THURSDAY. THIS LOW
WILL SEND ANOTHER WEATHER FRONT OVER THE SOUTHERN HALF OF THE
FORECAST AREA. SO THE STEADY PRECIP WILL FALL THROUGH THURSDAY
OVER THE FAR SOUTHERN AREAS WITH DEVELOPING PRECIP OVER THE
CENTRAL AREAS. THERE WILL BE JUST A CHANCE FOR THE NORTHERN HALF
DUE TO STRONGER OFFSHORE FLOW FROM THE EAST. THE WINDS WILL
REMAIN ON THE WINDY SIDE OVER THE SOUTHERN AREAS WITH GUSTS TO
35 MPH THROUGH THE DAY. THE WINDS OVER THE INNER CHANNELS WILL
SLOWLY DECREASE FROM THE NORTH AS THE LOW OVER THE FAR SE GULF
SLIDES TO THE WEST AND THE GRADIENT RELAXES. THERE WILL SOME
HIGHER GUSTS FROM INTERIOR PASSES IN THE MORNING ALONG THE COAST
MOUNTAINS BUT SHOULD NOT BE MORE THAN 35KT.

 THERE IS AVERAGE FORECASTER CONFIDENCE FOR THE NEXT 24HRS AND
USED A BLEND OF THE PREVIOUS FORECAST AND THE 12Z EC.

 &&

 .LONG TERM...SPRING WEATHER PATTERN CONTINUES THROUGH THE LONG
RANGE TIME FRAME WITH JET AXIS TO THE SOUTH OF OUR AREA. AT MID
LEVELS WIDE LOW PRESSURE AREAS WILL CONSOLIDATE OVER THE AK GULF
AND REMAIN THERE THROUGH THE WEEKEND. BY THE START OF NEXT WEEK
PATTERN RETURNS TO A MORE COMPLEX SET UP WITH LOW OVER THE BERING
SEA EXTENDING SOUTHEAST TOWARD HAIDA GWAII. AT THE SURFACE 976 MB
LOW IN THE CENTRAL GULF WILL PULL OFF TO THE NORTHWEST AS FRONTAL
BAND MOVING OVER THE PANHANDLE WILL SHEAR APART AS MID AND UPPER
LEVEL DYNAMICS WEAKEN. WEAK RIDGE WILL BUILD OVER THE PANHANDLE
SATURDAY BEFORE MOVING OFF TO THE EAST. THE SURFACE LOW WILL
WEAKEN THROUGH THE WEEKEND WHICH WILL RESULT IN VARIABLE
CLOUDINESS FOR SATURDAY AND SUNDAY WITH PERIODS OF RAIN OR SHOWER
ACTIVITY MAINLY OVER THE SOUTHERN PANHANDLE AND SPOTTIER AREAS OF
PRECIP TO THE NORTH. COLDER 850 TEMPERATURES ARE ADVECTING IN
WITH OVERNIGHT LOWS AT OR BELOW FREEZING, THUS EXPECT A RAIN SNOW
MIX TO RESULT. AT THIS TIME EXPECTING LITTLE TO NO SNOW
ACCUMULATION.

 TO THE WEST OF THE AREA A HIGH PRESSURE RIDGE BEGINS TO BUILD
OVER THE NORTH PACIFIC EXTENDING INTO BRISTOL BAY BY THE END OF
THE WEEKEND. DEEPENING TROUGH OVER THE AK GULF WILL RESULT BUT
STILL SOME UNCERTAINTY WITH FEATURES DOWN STREAM OF THE RIDGE.
HAVE SEEN INDICATIONS OF THE STRONG LOW MOVING UP FROM THE
PACIFIC TOWARDS HAIDA GWAII BUT EXACT TRACK AND STRENGTH OF THE
LOW IS NOT WELL ESTABLISHED YET. EITHER WAY FOR NEXT WEEK STILL
LOOKING AT HIGHEST PROBABILITY OF PRECIP OVER THE SOUTHERN
REGIONS.

 MODELS WERE IN GOOD AGREEMENT FOR THE START OF THE LONG RANGE
WITH MOST INITIALIZING WELL. MODEL SPREAD BEGINS TO INCREASE AS
NORTH PACIFIC - BRISTOL BAY RIDGE DEVELOPS, MAINLY WITH DOWN
STREAM FEATURES. ECMWF HAS REMAINED MOST CONSISTENT MODEL RUN TO
RUN BUT DOES KEEP HIGHER POPS THROUGH THE WEEKEND FOR THE
NORTHERN AND NORTHWESTERN PANHANDLE. USED A BLEND OF 12Z ECMWF
WITH INHERITED GRIDS THROUGH DAY 4 THEN TRANSITIONED TO NEW HPC,
WHICH CONTINUED TO MAINLY USE ECMWF - EC ENSEMBLE. FORECAST
CONFIDENCE BEGINS ABOVE AVERAGE BUT THEN DROPS BELOW AVERAGE BY
NEXT WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041.
         SMALL CRAFT ADVISORY FOR PKZ012-021-022-033-035-036-042-043-051-
     052.

&&

ABJ/PRB