Gale Warning 146, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM ADT FRI APR 25 2008

.SYNOPSIS...
.SHORT RANGE...CONDS TODAY IN A RANGE FM FROM THE STEADY LIGHT
RAIN AT YAKUTAT TO SUNNY IN THE PNHDL FM FREDERICK SOUND S.
THE STRONG AND LARGE SCALE RIDGE ALOFT THAT HAS BEEN THE SOURCE
OF DRYING IS MOVING EAST PAST THE PNHDL TODAY.  THIS RIDGE
IS EXTENDING N ALG THE PNHDL AT 500MB AT THIS TIME,  AND SHOULD
BE OVR CNTRL B.C. ABT 12Z SAT, WITH THE LAST OF THE ANTICYCLONIC
FLOW OVR THE PNHDL ENDING BY 00Z SUN AS THE RIDGE MOVES FARTHER
TO THE E.  ONSET STEADY RAIN IN PNHDLE WILL BE ASSOCD WITH AN
OCCLUSION AND PCPN BANDS SENT AHEAD OF A CMPLX LOW THAT IS
CURRENTLY 800 NM S OF CORDOVA. THE ONSET OF RAIN FOR THE OUTER
COAST S OF SITKA SHOULD BEGIN ABT 12Z TONIGHT, AND SPREAD NE
REACHING THE REMAINDER OF THE PNHDL BY ABT 00Z SUN.

GOES VIS SHOWS A LOW LVL CLOUD SHEET THAT MOVED SE TO COVER A
JUNEAU TO ANGOON LINE THIS MORNING.  THIS LOW LVL SC DECK
IS NOW BURNING OFF TO THE NW AND SHOULD CEASE TO BE A CIG ALL
THE WAY TO THE ERN GLFALSK THIS AFTERNOON.  SEA BREEZE EFFECTS
WILL CONT TO BE MINOR HWVR TO THE EXTENSIVE SNOW COVER.

GFS AND NAM ARE BOTH PROPERLY REPRESENTING THE CLOUD COVER FM
925 MB TO 850 MB THIS MORNING.  GFS IS GIVEN SLIGHT PREFERENCE
FOR THE SFC PRES FIELD IN THE GLFALSK BASED ON OBS AND GOES
IR LOOP INTERPRETATION, BUT BOTH WILL BE APPLIED.

THE CMPLX LOW ROUGHLY 800 NM S OF CORDOVA ALSO SEEMS BEST
HANDLED BY A HYBRID OF NAM AND GFS, SPCLY SINCE A QUICKSCAT
PASS AT 1530Z SEEMS TO SHOW A VARIETY OF SUBSYNOPTIC SCALE
FEATURES FM BOTH MODELS.  THIS LOW CMPLX WILL SEND AN OCCLUSION
THAT AT 12Z TONIGHT SHOULD BE 300 NM SW OF A LINE FM SITKA TO
KETCHIKAN.  NOTE GALES IN OUTSIDE WATERS. THE FRONTAL ORIENTATION
WILL HELP PROVIDE A AN OUTFLOW PRESSURE GRAD IN THE PNHDL.
THIS OUTFLOW WILL ALSO BE ENHANCED BY A HIGH PRES RIDGE EXTDNG
TO THE NW ALONG THE COAST MTN RANGE THIS AFTERNOON.

.LONG RANGE...MODELS ARE IN GENERAL AGREEMENT WITH DEVELOPMENT OF
AN UPPER LOW IN THE GULF OF ALASKA BY LATE SUN. THE LOW MOVES
SOUTHEASTWARD AND SLOWLY FILLS AS A WEAK RIDGE REPLACES IT IN THE
NORTHEAST PACIFIC. GFS ENSEMBLE SPREAD GROWS WITH MEMBER
DIFFERENCES IN THE DEPTH AND MOVEMENT OF THE UPPER LOW BUT MEAN
SOLUTION STILL RETAINS A LOW OF MODERATE STRENGTH THAT MOVES OVER
THE PACIFIC NW COAST. TIMING IS A LITTLE SLOWER THAN THE
OPERATIONAL GFS. ANOTHER TROUGH APPROACHES THE GULF OF ALASKA BY
THE MIDDLE OF NEXT WEEK ALTHOUGH MODELS INDICATE IT WILL BE
SOMEWHAT WEAKER THAN THE FIRST.

RAIN AND WIND OVER THE LATER PART OF THE THE WEEKEND WILL
DIMINISH SUN NIGHT AS THE UPPER LOW BEGIN TO MIGRATE
SOUTHEASTWARD. WITH THE LOW PASSING TO OUR SOUTH...FLOW ALOFT
BECOMES MORE EASTERLY BY TUE AND ALTHOUGH SOME MID AND HIGH
CLOUDS MAY PERSIST PRECIPITATION SHOULD BECOME FAIRLY ISOLATED.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...NONE.
MARINE...GALE ALL OUTSIDE 41>52.  SCA ALL INSIDE XCP LYNN CANAL
AND GLACIER BAY.

JBT/CFD