Gale Warning 144, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
219 PM AKST MON FEB 21 2011

.SHORT TERM...DEEPENING ARCTIC AIRMASS AS WELL AS INCREASING N
WINDS AT AND ABOVE THE BOUNDARY LAYER WILL RESULT IN AN
INTENSIFIED OUTFLOW BEGINNING TONIGHT.

LONG-WAVE RIDGE ALOFT OVER THE BERING IS GAINING AMPLITUDE
AND BY 18Z TUE WILL EXTEND N OVER PACD TO PAOT. TO THE EAST OF
THIS RIDGE IS A SERIES OF VORT MAXIMA ASSOCIATED WITH A TROUGH
ALOFT OVER THE CENTRAL INTERIOR THAT BY 18Z TUE WILL EXTEND SW FM
CYXY TO OVER PAYA AND FURTHER SW. THE TROUGH ALOFT IS A SLOWER TO
PROPAGATE THAN THE UPSTREAM LARGE-SCALE RIDGE. THE RESULT IS AN
INCREASE IN N WINDS ALOFT. BY TUE MORNING, MOST OF THE DEPTH OF
THE TROPOSPHERE ALL THE WAY DOWN TO THE LOWER BOUNDARY LAYER WILL
HAVE N FLOW. THE MODEL CONSENSUS FOR THIS UPPER LEVEL FLOW SCENARIO
IS GOOD.

ONLY SMALL CHANGES TO FORECAST PACKAGE FOR TONIGHT AND TUESDAY.
OVERNIGHT LOW TEMPERATURE FORECAST FOR THE VICINITY OF HAINES AND
SKAGWAY WERE LOWERED A FEW DEGREES. SMALL CHANGES WERE MADE TO THE
WINDS AND WIND CHILLS, BUT THESE ARE UPDATES FOR HOW THE MODELS
TEND TO PERFORM BETTER CLOSER TO THE EVENTS.

NO CHANGE TO THE FORECAST OF HEAVY FREEZING SPRAY BEGINNING IN
NORTHERN LYNN CANAL EARLY TUE. WATER TEMPERATURE AT THE SKAGWAY
TIDE STATION IS 3 DEG C, WITH THE AIR TEMPERATURE FALLS AND
INCREASING WINDS PROVIDING THE THE REMAINING INGREDIENTS FOR
THE WARNING.

THE MODEL CONSENSUS IS GOOD ESPECIALLY FOR THE OFFSHORE
CONDITIONS. THE PRIMARY GUIDANCE IS THE NAM, ALONG WITH LOCAL
MODELS THAT USE THE NAM FOR A NESTING.

&&

.LONG TERM...INVERTED TROUGH ALONG SOUTHEAST PANHANDLE FROM
BRITISH COLUMBIA COAST TOWARDS THE KENAI PENINSULA PERSISTING. THE
SURFACE RIDGE OVER THE WESTERN GULF INTO THE WESTERN PORTION OF
THE STATE HAS THE NORTHERN END BEING FORCED EAST WHILE THE
PRESSURE OVER THE INTERIOR OF AK AND THE YUKON INCREASE CREATING A
BUBBLE HIGH WITH A RATHER COLD POOL OF COLD AIR 850 MB
TEMPERATURES ARE AS COLD AS -28C AND SURFACE PRESSURES INTO THE
LOW TO MID 1050 VALUES.

THE TIGHT PRESSURE GRADIENT SEEMS TO LAST ONLY 24 TO 48 HOURS AS
THE HIGH IS FORECAST TO CONTINUE TO THE SOUTHEAST WITH THE COLD
AIR THROUGH BRITISH COLUMBIA. WILL NEED TO WATCH AND SEE IF THE
MODEL BIAS HAS HAPPENED AND THE HIGH DOES NOT DRIFT OFF AS
EXPECTED. IF NOT EXPECT A CONTINUED OUTFLOW OF COLD DRY AIR
THROUGH THE NORTH AND NORTHEAST INTERIOR PASSES THROUGH THE ST.
ELIAS MOUNTAINS AND OVER PANHANDLE INTO GLACIER BAY AND LYNN
CANAL. THE EXPECTATIONS AT THIS TIME IS FOR THE WINDS AND
TEMPERATURES TO MODERATE WEDNESDAY.

THROUGH FRIDAY THE UPPER LEVEL RIDGE IS BEING FORECAST AS AN UPPER
LEVEL LOW/TROUGH PATTERN MOVES FROM THE RUSSIAN FAR EAST ACROSS
THE BEAUFORT SEA THEN WESTERN CANADIAN ARCTIC ISLANDS BY FRIDAY
NIGHT. AS A RESULT A MORE WESTERLY FLOW WILL MOVE INTO THE
NORTHEAST GULF COAST FRIDAY AND INCREASED MOISTURE TO THE WESTERN
FORECAST AREA. PRECIPITATION SHOULD BE TRYING TO SPREAD INTO THE
PANHANDLE SATURDAY AND EARLY SUNDAY. IT IS EXPECTED THE HIGH OVER
NORTHWEST ALASKA WILL REBUILD WITH ANOTHER SOUTHWARD MOVING ARCTIC
FRONT FOR EARLY NEXT WEEK WITH CLEAR AND COOLING CONDITIONS.

FORECAST THROUGH THURSDAY WERE REFRESHED WITH THE 12Z NAM
SOLUTION, WHICH WAS USED BECAUSE OF THE PRESSURE PATTERN. LATER
PORTIONS OF THE FORECAST LOOKED GOOD SO MINOR IF ANY CHANGES MADE.
CONFIDENCE IS AVERAGE FOR THE FORECAST PERIOD.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM 3 AM TUESDAY TO 6 AM AKST WEDNESDAY FOR
     AKZ017.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011-012.
         GALE WARNING FOR PKZ011>013-022-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ021-031>033-035.

&&

JBT/BEZENEK