Gale Warning 138, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
2 PM AKST WED FEB 8 2012

.SHORT TERM...SATELLITE IMAGERY THIS AFTERNOON SHOWS A 964 MB LOW
IN THE FAR WESTERN GULF TRACKING TOWARD THE AK PENINSULA. THE
ASSOCIATED WEATHER FRONT WILL TRACK NORTHWARD MOVING OVER THE
EASTERN AK GULF AND AK PANHANDLE TONIGHT. THIS FRONT IS FAIRLY
WEAK SO EXPECT RESULTING PRECIPITATION TO BE FAIRLY LIGHT AND
PERIODIC THROUGH THE EVENING BEFORE DIMINISHING LATE TONIGHT. AS
THERE IS SOME COLDER AIR MOVING UP WITH THE FRONT SOME REGIONS MAY
SEE TEMPERATURES DROP JUST ENOUGH TO SEE SOME SNOW MIX IN WITH THE
RAIN. HOWEVER AS PRECIP WILL BE ENDING BY THE TIME TEMPERATURES
BEGIN TO DROP EXPECT LITTLE TO NO SNOW ACCUMULATION. COASTAL WATER
WINDS WILL BE AT GALE FORCE THIS EVENING IN THE NORTHERN GULF THEN
DIMINISH AS THE FRONT EXITS THE REGION. WINDS OVER THE PANHANDLE
HAVE BEEN GENERALLY EASTERLY WITH SOME HIGHER OUTFLOW GUSTS DUE TO
THE EAST WEST PRESSURE GRADIENT WITH THE LOW TO THE WEST AND HIGH
PRESSURE OVER THE YUKON AND BRITISH COLUMBIA. SOME HIGHER GUSTS
MAY BE SEEN AS THE LOW MOVES NORTH, THEN WINDS SHOULD DIMINISH
OVERNIGHT. THE PROBLEM AREAS HAS BEEN SKAGWAY WITH WINDS REMAINING
A BIT HIGHER THAN EXPECTED TODAY. THESE WINDS SHOULD DIMINISH
TONIGHT AS NORTH-SOUTH GRADIENT WEAKENS.

THINGS WILL PICK UP AGAIN THROUGH THE DAY THURSDAY AS A 982 MB MAX
GALE FORCE LOW MOVES FROM THE NORTH PACIFIC INTO THE SOUTHEAST
GULF THURSDAY AFTERNOON THEN STRENGTHENS TO STORM FORCE THURSDAY
EVENING. WINDS OVER THE SOUTHERN COASTAL WATERS WILL PICK UP TO
GALE FORCE THROUGH THE DAY WITH STRONG WINDS DEVELOPING OVER THE
SOUTHERN PANHANDLE. OUTFLOW WINDS WILL INCREASE THROUGH THE
AFTERNOON OVER THE CENTRAL PANHANDLE AS THE PRESSURE GRADIENT
INCREASES. PRECIP WILL MOVE IN FROM THE SOUTH THEN TRACK OVER THE
NORTHERN PANHANDLE THROUGH THE DAY. WITH WARMER TEMPERATURES
MOVING IN EXPECT PRECIP TO BE ALL RAIN.

FOR TONIGHT DIFFERENCES BETWEEN MODELS WERE FAIRLY MINOR. SOME
TIMING DIFFERENCES WITH RESPECT TO PRECIP END TIME OVER THE
NORTHWESTERN PANHANDLE BUT OVER ALL THERE WAS LITTLE CHANGE FROM
INHERITED GRIDS. MODELS WERE STILL SHOWING SOME FAIR DIFFERENCES
WITHE THE TRACK AND STRENGTH OF THE THURSDAY LOW PRESSURE SYSTEM.
12Z GFS WAS STILL THE STRONGEST WITH 977 MB CENTER WHILE THE 00Z
ECMWF WAS AT 990 MB. LATER RUNS THE MODEL HAVE FALLEN MORE IN LINE
CLOSER TO A 980 MB LOW, WHICH IS A BIT DEEPER THAN THE 12Z DATA
AVAILABLE FOR THE AFTERNOON FORECAST. USED THE 12Z NAM THEN 12Z EC
TO UPDATE GRIDS. CHANGES FOR TONIGHT WERE MINOR BUT DID BUMP UP
WINDS SLIGHTLY FOR THURSDAY AFTERNOON. FORECAST CONFIDENCE IS
ABOUT AVERAGE.

&&

.LONG TERM...
DIFFICULT DIFFICULT DECISION TODAY AS TO DEVELOPING LOW CENTER WILL
BE OFF DIXON ENTRANCE THU AFTERNOON-EVENING. THE EVIL CHOICE IS THE
INTENSITY OF THIS DEVELOPING SYSTEM. 08/12Z AK-GFS IS THE DEEPEST
SOLUTION WITH 976 MB 200 NM WSW OF BUOY 46205 WHICH WOULD PRODUCE
STORM FORCE WIND FOR THE SOUTHERN OUTSIDE MARINE ZONES AND STRONG
WIND FOR PRINCE OF WALES AND BARANOF ISLAND INTO THU NITE. 09Z SREF
AND 08/12Z UKMET ARE MORE OF A COMPROMISE BUT NOT USED. 08/12Z NAM
IS WEAKEST BUT IS SHOWING GALE FORCE BUT CAME IN WITH STORM FORCE
ON 18Z RUN. TRIED TO PICK USING 300-500 MB RH VERSUS SATELLITE
WATER VAPOR TECHNIQUES BUT OPS MODELS ALL WERE INITIALIZED WELL.

ULTIMATELY USED THE 08/12Z HI-RES ECMWF AS BASIS. 08/18Z AK-GFS WAS
CONSISTENT WITH 12Z GFS RUN FOR STORM FORCE BUT AFTER LOOKING AT
THE 850 MB WIND IN THE SLIGHTLY WEAKER ECMWF DECIDED TO INDICATE
STORM FORCE THU EVENING FOR OUTER WATERS NEAR THE END OF THE SHIFT.

SOUTHERLY FLOW ALOFT STILL HAS GOOD FETCH OF MOISTURE IN MEDIUM
RANGE UNTIL A SHORTWAVE UPPER RIDGE MOVES ACROSS THE PANHANDLE SUN
NIGHT AND MON. HPC PROGS USED AGAIN DAY 5 AND BEYOND WITH UPPER
LEVEL ONSHORE FLOW PREDOMINANT. CONFIDENCE IN THIS FORECAST PACKAGE
ONLY MODERATE DUE TO CONCERNS ABOUT STRENGTH OF SURFACE LOW THU
NIGHT AND FRIDAY.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THURSDAY AFTERNOON FOR AKZ027.
         STRONG WIND THURSDAY AFTERNOON FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012-035-036-041-042-051-052.
         SMALL CRAFT ADV PKZ011-013-021-022-031-033-034-043.

&&