Heavy Snow in Alaska, March 4 to 5, 2007

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST SUN MAR 4 2007

.SYNOPSIS...
.SHORT RANGE...ANOTHER MAJOR SNOW EVENT IN STORE FOR THE NORTHERN
HALF OF THE PANHANDLE TONIGHT AND MONDAY. AN AREA OF LOW PRESSURE
NEAR 50N 140W WILL MOVE NORTHEAST INTO THE SOUTHEAST GULF
TONIGHT...THEN WEAKEN NEAR BARANOF ISLAND MONDAY AFTERNOON. HIGH
PRESSURE TO THE NORTH WILL KEEP THE ARCTIC AIR IN PLACE OVER THE
NORTHERN HALF OF THE PANHANDLE THROUGH MUCH OF MONDAY LEADING TO
A GOOD OVERRUNNING SNOW EVENT AS MOISTURE FROM THE LOW SPREADS
NORTH. A TIGHTENING PRESSURE GRADIENT BETWEEN THE LOW AND HIGH
WILL BRING VERY WINDY CONDITIONS TO THE NORTHERN HALF OF THE
PANHANDLE THROUGH MONDAY MORNING. AT 18Z...THE NAM IS
INITIALIZING BEST WITH THE LOW BASED ON SATELLITE IMAGERY AND
BUOY OBS WHICH PUTS THE LOW AROUND 998 MB. A BLEND OF THE NAM AND
GFS WILL BE USED THROUGH THE SHORT RANGE BUT WILL FAVOR THE NAM
EARLY IN THE PERIOD.

NORTHERN HALF...WARNINGS AND ADVISORIES IN PLACE LOOK GOOD. SNOW
WILL DEVELOP TONIGHT AND BECOME HEAVY AT TIMES LATE TONIGHT AND
MONDAY MORNING OVER ZONES 21 24 AND 25 WHERE THE POTENTIAL FOR
THE BEST LIFT WILL OCCUR. QPF AMOUNTS THROUGH MONDAY ARE AROUND
0.4 TO 0.6 WITH OVER 1 INCH IN SOME LOCATIONS ON THE 12Z NAM.
SNOW RATIOS WILL BE HIGH...SO 1 TO 2 FEET OF SNOW LOOKS GOOD.
ONLY CONCERN IS THAT THE 12Z RUNS DO EXTEND THE HEAVIER BAND OF
SNOW FURTHER WEST INTO ZONES 20 22 AND 23 ON MON WHERE A 12 HOUR
PERIOD OF WARNING SNOWFALL COULD OCCUR. MAY CONSIDERING UPGRADING
TO WARNINGS FOR THOSE THREE ZONES. WIND ADVISORIES AND GALES OVER
THE NORTHERN AND CENTRAL INNER CHANNELS LOOKS GOOD.

SOUTHERN HALF...PRECIPITATION WILL CONTINUE OVER THE SOUTHERN
HALF OF THE PANHANDLE THROUGH MONDAY. WARMER AIR MOVING NORTH HAS
CHANGED THE PRECIP TO MAINLY RAIN OVER THE SOUTHERN THIRD WHILE
SNOW OVER ZONE 26 WILL CONTINUE THROUGH THE AFTERNOON...SO THE
HEAVY SNOW WARNING IS LOOKING GOOD THERE. MODEL SOUNDINGS
INDICATE THAT AN ABOVE FREEZING LAYER AROUND 3000 FEET WILL
SPREAD INTO ZONE 26 TONIGHT AND CHANGE THE PRECIP TO
RAIN...HOWEVER CURRENT TEMPS ARE IN THE 20S AND CONCERNED THAT A
SHALLOW LAYER BELOW FREEZING MAY REMAIN IN SOME AREAS TO PRODUCE
FREEZING RAIN. QPF AMOUNTS FOR THIS REGION TONIGHT ARE 0.5 TO
0.8. WILL CHANGE THE HEAVY SNOW WARNING TO A WINTER STORM WARNING
WITH THIS AFTERNOONS PACKAGE AND ADD IN FREEZING RAIN. ONLY OTHER
CONCERN IS THE HYDER AREA. STILL SNOWING BASED ON CZST OBS. WILL
CONTINUE TO WATCH FOR A CHANGE OVER TO RAIN AND EVALUATE IT THIS
AFTERNOON. QPF AMOUNTS THERE ARE 1 TO 2 INCHES THROUGH TONIGHT.

NORTHEAST GULF COAST (YAKUTAT)...OFFSHORE FLOW WILL CONTINUE TO
BRING DRY WEATHER WITH ONLY MID AND UPPER LEVEL CLOUDS AFFECTING
THE REGION THROUGH MONDAY. FLOW THROUGH PASSES WILL INCREASE
TONIGHT AS THE GRADIENT INCREASES...SO THE WIND ADV LOOKS ON
TRACK.

.LONG RANGE...LITTLE OR NO BREAK FOR SOUTHEAST ALASKA AS THE NEXT
SYSTEM DEVELOPING OVER THE PACIFIC MOVES NORTHWARD INTO THE
SOUTHERN GULF MONDAY NIGHT.  AS THE MODELS CONTINUE THE SLIGHT
WESTWARD DRIFT OF THE TRACK OF THE LOW.  RIGHT NOW APPEARS AS IF
THE DEPTH OF THE LOW WILL BE IN THE LOWER TO MID 960S AS IT
TRACKS NORTHWARD ALONG 140W BEFORE PULLING BACK TOWARDS PRINCE
WILLIAM SOUND WEDNESDAY NIGHT EARLY THURSDAY.

THE ASSOCIATED FRONTAL BAND PRECIPITATION SHOULD BE SPREADING TO
THE SOUTHERN PANHANDLE MONDAY NIGHT AND THEN TO THE NORTHERN BY
MIDDAY TUESDAY.  THIS WILL CONTINUE THE WARM UP TREND FOR THE
NORTH CENTRAL PANHANDLE...WHILE INCREASING THE NORTH-NORTHEAST
WINDS AGAIN ACROSS THE REGION. RAIN SNOW LINE SHOULD BE MOVING
NORTH TO APPROXIMATELY THE ICY STRAIT-JUNEAU AREA BY TUESDAY
AFTERNOON.

EXPECT TO GET GOOD SNOWFALL ACCUMULATIONS OVER THE
HOONAH-JUNEAU-GUSTAVUS-HAINES-PELICAN/ELFIN COVE ZONES WITH A
LESSER AMOUNT TO THE ANGOON-SITKA ZONES AS THEY SHOULD BE
SWITCHING TO RAIN EARLIER THAN THE REST. SKAGWAY COULD SEE SOME
SIGNIFICANT ACCUMULATIONS AS WELL BUT A LITTLE TOUGHER NUT TO
CRACK AS THEY ALWAYS SEEM TO RECEIVE LESS. HAINES AND SKAGWAY
SNOW WILL START LATER BUT THEY SHOULD NOT CHANGE TO RAIN UNTIL
LATE WEDNESDAY...AND I HAVE CONCERNS THAT THEY MAY NOT CHANGE/MIX
EVEN THEN.

RIGHT NOW AM HESITANT TO BE ISSUING A WINTER STORM WATCH TO TACK
ON TO END OF THE WARNINGS OUT OVER THE NORTH FOR THE NORTHERN
HALF OF THE PANHANDLE...BUT IF THERE WAS NOT ANYTHING OUT THAT
WOULD BE THE GAME PLAN...MAY CHANGE MY MIND AND DO IT ANYWAY THIS
AFTERNOON.

WITH THE STRONG LOW MOVING NORTH OVER THE EASTERN GULF OF ALASKA
THE STRONG GUSTY OUT FLOW WINDS WILL INCREASE AGAIN FOR ZONES
17/18/19/20/25 AND WILL PROBABLY IMPACT 21 AND 22 AS WELL.  THE
SOUTHERN INNER PASSES WILL BE CLOSE BUT DONT THINK THAT THEY
WILL BE AS BAD.  EXPECT TO SEE BETWEEN 40 AND 60 MPH GUSTS MONDAY
NIGHT/TUESDAY OVER THE NORTHERN PORTIONS OF THE PANHANDLE...AND
WOULD NOT BE SURPRISED IF A FEW TOPPED 60.

FOR THE MARINE FORECASTS GALES...ACROSS MUCH OF THE FORECAST AREA
ANTICIPATED FOR THE MONDAY NIGHT-TUESDAY TIME FRAME. FREEZING
SPRAY SHOULD BEGIN A DOWNWARD TREND AS THE AIR TEMPERATURES
MODERATE THROUGH TUESDAY.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WINTER STORM WARNING...ZONES 19..21..25
      ...HEAVY SNOW WARNING...ZONES 24 AND 26
      ...SNOW ADVY...ZONES 18...20...22...23
      ...WIND ADVY...ZONES 17>20-022-025
      ...WIND CHILL ADVY...ZONE 18 KLONDIKE HIGHWAY

MARINE...GALE...PKZ011>013-021-022-031-032-051
      ...HEAVY FRZG SPRAY...PKZ011>013
      ...SCA...PKZ033>036-041>043-053

TAR - BMB