Small Craft Advisory 227, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
315 PM AKDT TUE MAR 27 2012

.SHORT TERM...THE LATEST SATELLITE IMAGERY SHOWS THE PANHANDLE
UNDER MOSTLY CLOUDY SKIES BUT THERE ARE SIGNIFICANT SUNNY BREAKS
OVER THE NORTHEAST GULF COAST ALONG WITH OVER THE NORTH CENTRAL
INNER CHANNELS. THERE IS SOME PERIODS LIGHT RAIN FALLING OVER THE
FAR SOUTHERN AREA AS A WEAKENING WEATHER FRONT LIFTS NORTH. THIS
FRONT WILL CONTINUE TO DRIFT NORTH BUT WILL FALL PART THROUGH
TONIGHT. THE WINDS ARE ON THE LIGHT SIDE WITH THE MARINE WINDS OF
20 TO 15 KT FROM THE NORTH WITH SOME STRONGER WINDS OVER THE SE
GULF.

 BEHIND THE FRONT OVER THE SOUTHERN AREAS ATTM ANOTHER WEAK
SYSTEM WILL DRIFT NORTH THROUGH WED AFTERNOON TO BE OVER THE
SOUTHERN AREAS BY LATE WED MORNING. THIS SYSTEM IS ASSOCIATED
WITH A STRONGER UPPER LEVEL TROF AND THAT WILL RESULT IN RAIN
BEING LIKELY FOR THE FAR SOUTHERN AREAS WITH CHANGES OVER THE
CENTRAL AREAS THROUGH WED. THE NORTHERN AREAS WILL REMAIN ON THE
DRY SIDE WITH ESE FLOW A LOFT AND WILL BE PARTLY SUNNY WITH JUST
SOME HIGH THIN CLOUDS MOVING OVER THE AREA THROUGH WED. THE WINDS
WILL ALSO BE ON THE LIGHTER SIDE BUT THE WINDS WILL REMAIN IN THE
15-20 KT FROM THE NORTH OVER THE INSIDE WATERS AND SOME SMALL
CRAFT WINDS OVER THE GULF FROM THE EAST.

 USED A BLEND OF THE PREVIOUS FORECAST AND THE 12Z EC. THERE WAS
NOT MUCH CHANGE TO THE FORECAST AND THERE IS ABOUT AVERAGE
FORECASTER CONFIDENCE FOR THE NEXT 24HRS.

&&

.LONG TERM...SPRING LIKE PATTERN HAS SHOWN LITTLE CHANGE FROM
PREVIOUS FORECASTS. COMPLEX AREA OF LOW PRESSURE CENTERS FROM
BRISTOL BAY AREA TO HAIDA GWAII WILL CONSOLIDATE TO A SINGLE LARGE
LOW OVER TH AK GULF THROUGH THURSDAY. NEXT SURFACE LOW WILL TRACK
EASTWARD ACROSS THE SOUTHERN AK GULF SWINGING INTO THE SOUTHEAST
GULF BY THURSDAY AFTERNOON INTO THURSDAY EVENING. AS THIS
NEGATIVELY TILTED UPPER TROUGH SHIFTS INTO A MORE VERTICALLY
STACKED LOW EXPECTING LIKELY TO CATEGORICAL PRECIP FOR THE
SOUTHERN PANHANDLE THURSDAY INTO FRIDAY. THINK THE FRONT WILL
SHEAR APART AS UPPER LEVEL DYNAMIC SUPPORT WEAKEN OVER THE
NORTHERN PANHANDLE SO HAVE KEEP POPS TO CHANCE OR LOWER OVER THE
CENTRAL AND NORTHERN AREAS. PRECIP TYPE BY THU INTO FRI MAY BE
MORE OF A MIX OF RAIN AND SNOW COLDER 850 AIR MASS MOVES IN. WINDS
IN THE COASTAL WATERS PICKUP TO MAX SMALL CRAFT AS THE LOW IN THE
SOUTHEAST GULF MOVES IN THEN PUSHES NORTH. FOR NORTHERN INNER
CHANNELS INCREASED NORTH-SOUTH PRESSURE GRADIENT WILL INCREASE
NORTHERLY WINDS TO SMALL CRAFT LEVEL. FOR FRIDAY DO SEE WEAK RIDGE
BUILD OVER THE PANHANDLE WHICH WILL SHIFT WINDS TO THE SOUTH FOR A
BRIEF PERIOD.

OVERALL PATTERN WITH JET MAX TO THE SOUTH OF THE AREAS AND MID
LEVEL LOW PRESSURE SYSTEMS FORM BRISTOL BAY EXTENDING
SOUTHEASTWARD REMAINS THROUGH THE WEEKEND WITH MODELS DIVERGING ON
DETAILS OF SURFACE FEATURES. HIGHEST CHANCE OF PRECIP WILL BE OVER
THE SOUTHERN PANHANDLE. NEXT PATTERN CHANGE IS A RIDGE BUILDING
OVER THE N PACIFIC AND INTO BRISTOL BAY AREA WITH A DEEPENING
TROUGH IN THE AK GULF. SOME TIMING ISSUES WITH THIS FEATURE
BETWEEN MODELS AND FROM RUN TO RUN SO FAIR AMOUNT OF UNCERTAINTY.

MODELS WERE IN GOOD AGREEMENT AT THE START OF THE LONG TERM. ECMWF
HAS BEEN MOST CONSISTENT RUN TO RUN. LEANED TOWARD A BLEND OF THE
12Z EC WITH SOME 12Z GFS. THIS PATTERN WAS VERY SIMILAR TO
INHERITED GRIDS SO OVERALL CHANGES WERE VERY MINOR TO THE
FORECAST. FROM DAY FOUR ONWARD USED NEW HPC GUID WHICH CONTINUED
TO BE MOSTLY ECMWF / ECMWF ENSEMBLES AND WAS ALSO VERY CLOSE TO
INHERITED FORECAST PACKAGE. FORECAST CONFIDENCE BEGINS ABOVE
AVERAGE THEN DROPS BY THE END OF THE WEEKEND.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ033-035-036-041>043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-052.

&&

ABJ/PRB