Gale Warning 311, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
158 PM AKDT TUE OCT 27 2009

.SHORT TERM...A COLD UPPER LEVEL TROUGH MOVING ACROSS SOUTHEAST
ALASKA TODAY WILL CONTINUE TO PRODUCE SHOWERS ACROSS THE AREA
THAT ARE EXPECTED TO BECOME ISOLATED TO SCATTERED OVERNIGHT.
SHOWERS APPEAR TO BE MOST NUMEROUS ALONG COAST MOUNTAINS AND
NORTHERN. COLD POOL ASSOCIATED WITH COLD POOL ALOFT...AS LOW AS
-35 OVER GLACIER BAY...HAS ALLOWED SNOW LEVELS TO FALL TO AS LOW
AS 1500 FEET AND SUPPORTED AN ISOLATED LIGHTNING STRIKE ALONG
EAST SIDE OF SOUTHERN BARANOF ISLAND. BELIEVE THIS TO BE ISOLATED
AND DID PUT IN ZONES.

 STRONG BUT FLAT PACIFIC RIDGE BUILDING THROUGH NORTHEAST PACIFIC
THIS THROUGH THIS EVENING WILL STABILIZE ATMO TONIGHT AND SHOULD
DIMINISH SHOWER ACTIVITY. ONSHORE FLOW AND APPROACHING SYSTEM
WILL KEEP SKIES MOSTLY CLOUDY. RIDGE CONTINUES EAST WEDNESDAY
MORNING AND OVER WESTERN CANADA BY WEDNESDAY AFTERNOON.

 DEV LOPING STRONG GALE OVER CENTRAL PACIFIC FORECAST TO RACE
NORTHEAST AND BE IN SE GULF BY LATE WEDNESDAY AFTERNOON. CENTER
PRESSURE OF THIS LOW FORECAST TO DROP INTO MID 960S AS IT
APPROACHES SE GULF SO EXPECT SOLID E GALES IN NE QUAD OF LOW ON
WED.GUSTY ADVISORY LEVEL EAST WINDS SPREAD INTO SOUTHERN AND
COASTAL ZONES WEDNESDAY AFTERNOON. A SECOND ROUND OF WESTERLY
GALES IS JUST APPROACHING COASTAL WATERS AT END OF SHORT TERM.
MODELS DO DIFFER ON EXACTLY HOW FAR NORTH THE LOW MAKES IT AND
TIMING OF ITS EASTWARD PROGRESSION. I LIKED A SOLUTION THAT KEEP
A TROUGH OF LOWS ACROSS SOUTHEAST GULF WITH STRONGEST CENTER
PASSING OVER SOUTHERN PANHANDLE WED NIGHT.

 AS LOW APPROACHES WILL SEE INCREASE IN N OR NE GRADIENTS THROUGH
INNER CHANNELS BUT MAX STRENGTH NOT REALIZED IN SHOWER TERM BUT
WILL HAVE SMCR DEVELOPING. RAIN ASSOCIATED WITH WARM SECTOR OF
LOW WILL SPREAD ACROSS SOUTHERN AND SOUTH CENTRAL LATE TONIGHT
INTO EARLY WEDNESDAY. THIS RAIN COULD BE HEAVY AT TIMES FROM
FREDERICK SOUND SOUTH. STILL SOME CONCERN ON HOW FAR STEADY
PRECIP WILL MAKE IT AND WILL KEEP POPS IN CHANCE CATEGORY FOR
NORTHERN AREAS. WITH LOW SNOW LEVELS ALREADY IN PLACE AND
SIGNIFICANT PRECIP EXPECTED ACROSS AT LEAST SOUTHERN AND SOUTH
CENTRAL WOULD EXPECT SIGNIFICANT SNOW (1-2 FEET) FOR THE HIGHER
ELEVATIONS OF COAST MOUNTAINS ON WEDNESDAY AND CONSIDERING SPS
FOR EVENT. ENOUGH COOL AND DRY AIR OVER NORTHERN AREAS WHERE WET
BULB EFFECTS COULD LEAD TO FLURRIES.

&&

.LONG TERM...MID RANGE FORECAST IS STILL A BIT TRICKY TODAY AS THE
MODEL ARE HAVING A HARD TIME WITH THE SYSTEM COMING IN FOR
THURSDAY. TRACK IS RATHER GOOD BETWEEN THE MODELS BRINGING THE LOW
INTO PRINCE OF WALES ISLAND THURSDAY. THE KINKS COME IN FIGURING
OUT THE STRENGTH AND TIMING. NAM IS BY FAR THE SLOWEST BY ABOUT 6
HOURS. EC AND THE UKMET ARE IN BETWEEN AND THE GFS WAS THE
FASTEST. EC WAS ALSO THE STRONGEST BY A GOOD 10 MB COM PAIRED TO
THE OTHER MODELS. ELECTED TO GO WITH THE EC MIXED WITH THE UKMET
TO GET THE SLOWER SOLUTION AND BUOY UP THE CENTRAL PRESSURE TO A
MORE RESPECTABLE 972 MB FROM WHAT THE EC WAS SHOWING.

LONG TERM FORECAST MEANWHILE IS EXPERIENCING A PARADIGM SHIFT FOR THIS
WEEKEND. PREVIOUS MODEL RUNS HAVE KEPT A SYSTEM COMING OUT OF THE
NORTHERN PACIFIC WELL TO THE SOUTH OF THE AREA AND GIVEN US A
SOMEWHAT DRY FORECAST. THAT STARTED TO CHANGE OVER THE PAST 24
HOURS AS THE EC HAS BEEN BRINGING THE SYSTEM FARTHER NORTH AND
WITH THE 0Z RUN HAS A 975MB LOW COMING UP THE COAST FOR SATURDAY.
THE 12Z RUN HAS ALSO SETTLED ON THIS SOLUTION EXCEPT HAS THE LOW A
LITTLE FARTHER OFFSHORE. THE GFS ON THE 12Z RUN HAS SUDDENLY
JUMPED INTO THE SAME BOAT BRINGING A SIMILAR STRENGTH LOW UP INTO
CAPE DECISION AND CONTINUING NORTHEAST THROUGH THE NORTHERN
PANHANDLE. SPREAD BETWEEN THE MEMBERS OF THE GFS ENSEMBLE IS STILL
SOMEWHAT LARGE, BUT ARE STARTING TO CLUSTER AROUND THE SAME
SOLUTION. IN EITHER CASE, SATURDAY IS LOOKING WET AND CLOUDY WITH
SOME WIND FOR THE COASTAL WATERS AND SOUTHERN LAND ZONES AS THE
LOW PULLS UP THE COAST.

EC WAS THE MODEL OF CHOICE FOR THE LONG RANGE SWITCHING TO THE HPC
GUIDANCE AFTER DAY 4. FORECAST CONFIDENCE IS AVERAGE GIVEN THE
DIFFERENCES BETWEEN THE MODELS. YET THE DIFFERENCES ARE NOT TOO
DRASTIC AND CONSISTENCY BETWEEN RECENT MODEL RUNS DO NOT HAVE ME
DISCOUNTING THE RECENT CHANGE IN SOLUTIONS OVERALL.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY FROM NOON TO 6 AM AKDT THURSDAY FOR AKZ027.
WIND ADVISORY FROM 3 PM TO 6 AM AKDT THURSDAY FOR AKZ023-028.
MARINE...GALE WARNING FOR PKZ036-041>043-051. SMALL CRAFT ADVISORY
FOR PKZ011-013-021-022-031>035-052.

&&

MM/EAL