Heavy Snow in Alaska, December 31, 2002

SOUTHEAST ALASKA FORECAST DISCUSSION
245 AM AST TUE DEC 31 2002

.SYNOPSIS...
.SHORT RANGE...MAIN ISSUE FOR TODAY WILL BE WHERE SFC LOW TRACKS
ACROSS THE AREA. AREAS JUST TO THE LEFT OF THE TRACK WILL LIKELY
SEE LIGHT N WINDS AND A SIGNIFICANT SNOWFALL...ON THE ORDER OF
3-5 INCHES...WHILE AREAS TO THE RIGHT WILL BE RAIN WITH BRISK SE
WINDS. LATEST SFC ANALYSIS SHOWS LOW A TAD TO THE SE OF THE MODEL
POSITION...AND PRESSURE FALL ANALYSIS SHOWS LOW TRACKING TOWARD
SOUTHERN BARANOF ISLAND...JUST S PASI. LOOKING LIKE IT WILL CROSS
THRU ZONE 25 JUST S PAJN LATER THIS AFTERNOON...SETTING UP THE
PAJN-PAOH CORRIDOR WITH A POTENTIALLY DECENT SNOW EVENT. AM
CONSIDERING SNOW AVDY NRN ZONE 25 AND FAR SRN ZONES 21 AND 24 FOR
TODAY. WILL KEEP AN EYE ON THE LOW TRACK OVER THE NEXT FEW HOURS
AND MAKE FINAL DECISION CLOSER TO FORECAST TIME.

TO THE S...WILL GO WITH RAINY AND WINDY CONDS AS THE LOW MOVES
ONSHORE N OF THEM. WILL LIKELY NEED WIND ADVYS FOR THE SRN HALF
OF THE AREA. TO THE NW...AREAS WILL BE BETWEEN THE LOW TO THE SE
AND UPPER TROF TO THE W...WITH MINIMAL FORCING FOR UVV... EXCEPT
OVER ZONE 22...WHERE BANDS OF RAIN OR SNOW SHOWERS ARE MOVING
ONSHORE EAST OF UPPER TROF OVER S-CENTRAL AK. WITH SFC LOW TO THE
SE EXPECTED FURTHER AWAY FROM ZONE 22 THAN PROGGED... STRONGER
OFFSHORE FLOW SHOULD REMAIN SE OF THERE. WILL GO WITH LIKELY POPS
FOR RAIN AND/OR SNOW SHOWERS THERE. WILL TAKE LOOK AT 12Z PAYA
SOUNDING TO MAKE FINAL DETERMINATION ON PTYPE.

FOR THE MARINE...WILL GO WITH GALES AREA 1B...AND SRN AREA 1A3.
WILL GO WITH SCA CENTRAL 1A3...1A2 AND 2A...AND 20 KT OR LESS
ELSEWHERE.

.LONG RANGE...THE SURFACE LOW AND UPPER LEVEL TROUGH MOVE EAST OF
THE PANHANDLE EARLY TUE EVENING WITH SOUTHWEST FLOW DEVELOPING
BEHIND THIS SYSTEM. THIS WILL KEEP RAIN SHOWERS GOING ACROSS THE
SOUTHERN HALF OF THE PANHANDLE INTO EARLY WED MORNING. A MIX OF
RAIN AND SNOW SHOWERS WILL OCCUR OVER THE NORTHERN HALF WITH
MAINLY SNOW OVER THE NORTHWEST PANHANDLE AND NORTHERN LYNN CANAL
AREA.

A 978 MB LOW MOVES NORTHEAST FROM THE NORTHEAST PACIFIC INTO THE
SOUTHEAST GULF EARLY WED AND WEAKENS AS IT MOVES ACROSS THE
CENTRAL PANHANDLE WED NIGHT. RAIN AND WINDY CONDITIONS WILL
SPREAD INTO THE SOUTHERN ZONES BY DAY BREAK AND SPREAD NORTHWARD
DURING THE DAY INTO THE REMAINDER OF THE PANHANDLE EXCEPT THE
NORTHWEST AREAS. EXPECT PRECIPITATION TO BE A MIX OF RAIN AND
SNOW OVER THE NORTHERN THIRD. AN UPPER LEVEL TROUGH DIGGING
SOUTHWARD FROM CENTRAL ALASKA WILL CAUSE WEAK WAVES TO FORM ON
THE ARCTIC BOUNDARY OVER THE NORTHERN GULF AND KEEP THE POTENTIAL
FOR SNOW SHOWERS OVER THE NORTHWEST AREAS.

DRYING TREND INTO THU STILL LOOKS GOOD WITH AN UPPER LEVEL RIDGE
BUILDING OVER THE EASTERN GULF AND OFFSHORE FLOW IN THE LOW
LEVELS STRENGTHENING DURING THE DAY AS THE NEXT LOW MOVES INTO
THE SOUTHEAST GULF. THIS NEXT SYSTEM MOVES NORTH ALONG THE
EASTERN GULF COAST AND INTO THE NORTHERN GULF BY FRIDAY NIGHT.
THIS SYSTEM BRINGS A MUCH WARMER AIRMASS INTO ALL OF THE
PANHANDLE WITH FRONTAL RAIN CHANGING TO SHOWERS EXPECTED IN ALL
ZONES EXCEPT THE NORTHWEST PANHANDLE WHERE PRECIP MAY BEGIN AS
SNOW BEFORE CHANGING TO RAIN.

FOR THE EXTENDED PERIOD, SOUTHERLY FLOW ALOFT OVER THE NORTHEAST
PACIFIC INTO THE EASTERN GULF WILL CONTINUE TO BRING FRONTAL
SYSTEMS UP FROM THE SOUTH INTO THE PANHANDLE. AIRMASS REMAINS
FAIRLY MILD THROUGH THE WEEKEND TO SUPPORT MAINLY RAIN OVER
SOUTHEAST ALASKA WITH TEMPERATURES COOLING INTO EARLY NEXT WEEK.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...MAY NEED SNOW ADVY NRN ZONE 25 AND SRN ZONES 21 AND 24
         FOR TODAY.
      ...WIND ADVYS ZONES 26..27..28 AND 29 TODAY.

MARINE...GALE...AREA 1B...SOUTHERN 1A3.
      ...SCA...AREA 2A...1A2...CENTRAL 1A3.

RWT/TAR
FXAK67 PAJK 311128
SOUTHEAST ALASKA FORECAST DISCUSSION
245 AM AST TUE DEC 31 2002

.SYNOPSIS...
.SHORT RANGE...MAIN ISSUE FOR TODAY WILL BE WHERE SFC LOW TRACKS
ACROSS THE AREA. AREAS JUST TO THE LEFT OF THE TRACK WILL LIKELY
SEE LIGHT N WINDS AND A SIGNIFICANT SNOWFALL...ON THE ORDER OF
3-5 INCHES...WHILE AREAS TO THE RIGHT WILL BE RAIN WITH BRISK SE
WINDS. LATEST SFC ANALYSIS SHOWS LOW A TAD TO THE SE OF THE MODEL
POSITION...AND PRESSURE FALL ANALYSIS SHOWS LOW TRACKING TOWARD
SOUTHERN BARANOF ISLAND...JUST S PASI. LOOKING LIKE IT WILL CROSS
THRU ZONE 25 JUST S PAJN LATER THIS AFTERNOON...SETTING UP THE
PAJN-PAOH CORRIDOR WITH A POTENTIALLY DECENT SNOW EVENT. AM
CONSIDERING SNOW AVDY NRN ZONE 25 AND FAR SRN ZONES 21 AND 24 FOR
TODAY. WILL KEEP AN EYE ON THE LOW TRACK OVER THE NEXT FEW HOURS
AND MAKE FINAL DECISION CLOSER TO FORECAST TIME.

TO THE S...WILL GO WITH RAINY AND WINDY CONDS AS THE LOW MOVES
ONSHORE N OF THEM. WILL LIKELY NEED WIND ADVYS FOR THE SRN HALF
OF THE AREA. TO THE NW...AREAS WILL BE BETWEEN THE LOW TO THE SE
AND UPPER TROF TO THE W...WITH MINIMAL FORCING FOR UVV... EXCEPT
OVER ZONE 22...WHERE BANDS OF RAIN OR SNOW SHOWERS ARE MOVING
ONSHORE EAST OF UPPER TROF OVER S-CENTRAL AK. WITH SFC LOW TO THE
SE EXPECTED FURTHER AWAY FROM ZONE 22 THAN PROGGED... STRONGER
OFFSHORE FLOW SHOULD REMAIN SE OF THERE. WILL GO WITH LIKELY POPS
FOR RAIN AND/OR SNOW SHOWERS THERE. WILL TAKE LOOK AT 12Z PAYA
SOUNDING TO MAKE FINAL DETERMINATION ON PTYPE.

FOR THE MARINE...WILL GO WITH GALES AREA 1B...AND SRN AREA 1A3.
WILL GO WITH SCA CENTRAL 1A3...1A2 AND 2A...AND 20 KT OR LESS
ELSEWHERE.

.LONG RANGE...THE SURFACE LOW AND UPPER LEVEL TROUGH MOVE EAST OF
THE PANHANDLE EARLY TUE EVENING WITH SOUTHWEST FLOW DEVELOPING
BEHIND THIS SYSTEM. THIS WILL KEEP RAIN SHOWERS GOING ACROSS THE
SOUTHERN HALF OF THE PANHANDLE INTO EARLY WED MORNING. A MIX OF
RAIN AND SNOW SHOWERS WILL OCCUR OVER THE NORTHERN HALF WITH
MAINLY SNOW OVER THE NORTHWEST PANHANDLE AND NORTHERN LYNN CANAL
AREA.

A 978 MB LOW MOVES NORTHEAST FROM THE NORTHEAST PACIFIC INTO THE
SOUTHEAST GULF EARLY WED AND WEAKENS AS IT MOVES ACROSS THE
CENTRAL PANHANDLE WED NIGHT. RAIN AND WINDY CONDITIONS WILL
SPREAD INTO THE SOUTHERN ZONES BY DAY BREAK AND SPREAD NORTHWARD
DURING THE DAY INTO THE REMAINDER OF THE PANHANDLE EXCEPT THE
NORTHWEST AREAS. EXPECT PRECIPITATION TO BE A MIX OF RAIN AND
SNOW OVER THE NORTHERN THIRD. AN UPPER LEVEL TROUGH DIGGING
SOUTHWARD FROM CENTRAL ALASKA WILL CAUSE WEAK WAVES TO FORM ON
THE ARCTIC BOUNDARY OVER THE NORTHERN GULF AND KEEP THE POTENTIAL
FOR SNOW SHOWERS OVER THE NORTHWEST AREAS.

DRYING TREND INTO THU STILL LOOKS GOOD WITH AN UPPER LEVEL RIDGE
BUILDING OVER THE EASTERN GULF AND OFFSHORE FLOW IN THE LOW
LEVELS STRENGTHENING DURING THE DAY AS THE NEXT LOW MOVES INTO
THE SOUTHEAST GULF. THIS NEXT SYSTEM MOVES NORTH ALONG THE
EASTERN GULF COAST AND INTO THE NORTHERN GULF BY FRIDAY NIGHT.
THIS SYSTEM BRINGS A MUCH WARMER AIRMASS INTO ALL OF THE
PANHANDLE WITH FRONTAL RAIN CHANGING TO SHOWERS EXPECTED IN ALL
ZONES EXCEPT THE NORTHWEST PANHANDLE WHERE PRECIP MAY BEGIN AS
SNOW BEFORE CHANGING TO RAIN.

FOR THE EXTENDED PERIOD, SOUTHERLY FLOW ALOFT OVER THE NORTHEAST
PACIFIC INTO THE EASTERN GULF WILL CONTINUE TO BRING FRONTAL
SYSTEMS UP FROM THE SOUTH INTO THE PANHANDLE. AIRMASS REMAINS
FAIRLY MILD THROUGH THE WEEKEND TO SUPPORT MAINLY RAIN OVER
SOUTHEAST ALASKA WITH TEMPERATURES COOLING INTO EARLY NEXT WEEK.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...MAY NEED SNOW ADVY NRN ZONE 25 AND SRN ZONES 21 AND 24
         FOR TODAY.
      ...WIND ADVYS ZONES 26..27..28 AND 29 TODAY.

MARINE...GALE...AREA 1B...SOUTHERN 1A3.
      ...SCA...AREA 2A...1A2...CENTRAL 1A3.

RWT/TAR