Gale Warning 9, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
1226 PM AKST THU JAN 15 2009

.SHORT TERM...FORECAST PACKAGE CHANGES AT LEAST THROUGH  DAYTIME
FRIDAY ARE SMALL.  THE PRIMARY CHANGE IS TO INCREASE THE EXTENT
OF RADIATIVE FOG TONIGHT AND LOWER THE POP FOR RAIN TONIGHT.  THE
ONSET OF RAIN FOR FRIDAY HAS BEEN KEPT WITH NO CHANGES.  THE
MODEL CONSENSUS IS USEFUL WITH THE NAM  AND WORKSTATION WRF
PREFERRED OVER THE GFS PRIMARILY FOR THE  GREATER DETAIL AND
BETTER ABILITY TO WORK WITH COMPLEX TERRAIN.

AN UNUSUALLY STRONG WARM FRONT IS MOVG E BYD THE PNHDL AT THIS
TIME. IT SHOWED UP CLEARLY AS A STRONG AND SHALLOW FRONTAL
INVERSION AT 570 MB ON 12Z YAKUTAT RAOB. THE GOES IR LOOP AS WELL
AS THE BIORKA RADAR DATA HAVE SHOWN THIS FEATURE WELL EXCEPT IT IS
HARDER TO IDENTIFY DEEP IN THE BOUNDARY LAYER. THIS WARM FRONT HAS
HELPED KEEP THE OVERCAST OVR THE PANHANDLE THIS MORNING, AND ALSO
LIMITING THE DRYING TODAY.

STRONG SUBSIDENCE INVERSIONS SHOWED UP ON BOTH THE ANNETTE ISLAND
AND YAKUTAT 12Z RAOBS. THESE INVERSIONS ARE CONSISTENT WITH THE
LARGE SCALE RIDGE ALOFT OVER THE PANHANDLE, INCLUDING THAT THE
RIDGE HAD ALREADY MOVED E BYD YAKUTAT.

PATCHY RADIATIVE FOG WILL BE FORECAST FOR NEARLY ALL ZONES FOR
TONIGHT.

THE POLAR FRONT ZONE IS MERIDIONALLY ORIENTED INTO THE WESTERN
GULF AT THIS TIME. THE FRONTAL WAVES AND THE FRONTS HAVE BEEN
WEAKENING AS THEY TURN TO THE NE AND TRACK TOWARD THE PANHANDLE,
AND, EXCEPT FOR WARM FRONTS, HAVE BEEN DISSIPATING BEFORE THEY CAN
REACH THE PANHANDLE. HOWEVER, THE FIRST OF THE OCCLUSIONS TO REACH
THE PANHANDLE FROM THE WEST SHOULD OCCUR FRIDAY. THE HIGH FREEZING
LEVELS WILL PERSIST SO THE PRECIP WILL SPREAD AS RAIN ACROSS THE
PANHANDLE FRI.

&&

.LONG TERM...BROAD SCALE BUT STRONG MID TO UPPER LEVEL RIDGE
CONTINUES ACROSS THE AREA THROUGH THE WEEKEND WITH MILD
CONDITIONS. AN UPPER LEVEL TROUGH MOVING ACROSS THE GULF WILL
ENTER THE EASTERN GULF EARLY NEXT WEEK THEN ACROSS THE PANHANDLE
THROUGH MID WEEK. MODELS ARE IN GENERAL AGREEMENT IN SYNOPTIC
SCALE THROUGH THE END OF FORECAST PERIOD WITH MINOR DIFFERENCES IN
TIMING AND INTENSITY OF THE TROUGH TOWARDS THE END OF THE FORECAST
PERIOD.

THE ECMWF STILL TRIES TO BREAK OFF THE BASE OF THE ELONGATED
TROUGH INTO A CUTOFF MID LEVEL LOW ON TUESDAY AND WEDNESDAY AND
SENDS THE MAIN ENERGY TOWARDS OREGON/CALIFORNIA COASTS. TO THE
NORTH OF THE CUTOFF LOW...NO MAJOR PROBLEMS TO MAKE A GOOD MODEL
CONSENSUS. THE INHERITED GRIDS LOOK GOOD ON TAKING A MIDDLE
POSITION IN BETWEEN THE ECMWF AND GFS. JUST A LITTLE COSMETIC
TOUCHES ARE NEEDED TO MAKE FINE TUNES WITH LATEST MODEL RUNS. THIS
YIELDS AN OVERALL AVERAGE FORECAST CONFIDENCE THROUGHOUT THE LONG
TERM PERIODS.

A SERIES OF WAVES WILL PUSH NORTH ACROSS THE SOUTHEAST ALASKA WITH
SUB-TROPICAL MOISTURE CONNECTED TO THE SOUTHWEST UNDER PERSISTING
ONSHORE FLOW. THE WAVE ENERGY ON FRIDAY NIGHT WILL FOCUS OVER THE
NORTHERN PANHANDLE THROUGH SATURDAY THEN SLOWLY MOVE OVER THE
CENTRAL PANHANDLE SUNDAY AND SUNDAY NIGHT BEFORE WEAKENS ON
MONDAY. MODERATE TO HEAVY RAIN IS EXPECTED WITH THE SYSTEM
ACCOMPANIED WITH BREEZY TO WINDY CONDITIONS ALONG THE COASTAL
ZONES. GALE FORCE WINDS ACROSS THE NORTHEAST GULF ARE EXPECTED AS
WELL.

THE UPPER RIDGE WILL GRADUALLY MOVE TO THE EAST AS A SHORTWAVE
TROUGH IN THE CENTRAL GULF MOVES INTO THE EASTERN GULF AND
SOUTHEAST ALASKA LATE MONDAY INTO TUESDAY. AN UPPER RIDGE WILL
BUILD BEHIND THE TROUGH ACROSS THE GULF AND A STRONG SURFACE HIGH
WILL REBUILD OVER THE YUKON BY THAT TIME WITH COLDER AIR MOVING
SOUTHWARD ACROSS THE PANHANDLE THROUGH THURSDAY AS THE HIGH SLIDES
SOUTHEAST ALONG THE COAST MOUNTAINS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
         SMALL CRAFT ADVISORY FOR PKZ041>043-051.

JBT/SJA