Heavy Snow in Alaska, January 29, 2004

SOUTHEAST ALASKA FORECAST DISCUSSION
1045 AM AST WED JAN 28 2004

.SYNOPSIS...
.SHORT RANGE...POLAR JET STORM TRACK STILL AIMED SOUTH OF
PANHANDLE. DENSE ARCTIC HI PRES STILL SOLID OVER Y-T. GLANCING
BLOW FROM YESTERDAYS WEAK UPPER WAVE OVER SOUTHERN ZONES HAS
MOVED EAST INTO BC. ANOTHER SYSTEM NOW MOVG EAST NR 53N 145W WILL
BRING MORE PCPN TNGT SOUTHERN ZONES. SAT DATA INDICATES PCPN RATE
UNDER ENHANCED CLDS ON NW SIDE OF CIRCULATION TO BE ONE TO TWO
TENTHS INCHES PER HR.  EXPECT THIS PCPN AREA TO BE SQUEEZED INTO
E-W BAND AS IT ENCOUNTERS ARCTIC HI NEAR LAND FALL. WILL NOT CHG
HVY SNOW WARNINGS SOUTHERN ZONES FOR LATE TNGT BUT BELIEVE PCPN
ACCUM WILL END UP WITH TIGHT N-S GRADIENTS AND NOT WIDESPREAD HVY
SNOW EVENT. ELSW ADVISORY LEVEL WIND SPEEDS PERSISTING MOST ZONES
WITH HIGHEST WINDS THRU GAPS IN TOPO. WIND SPEEDS WILL BE SLOW TO
SUBSIDE NEXT 36H AS APPROCHING LOW CENTER MAINTAINS EXISTING
GRADIENTS. AS THIS LOW MOVES INLAND MODELS HINT IT STARTS ERODING
COLD TEMP INTERIOR AND REDUCES STRENGTH OF OFFSHORE FLOW.

.LONG RANGE...A MILDER WEATHER PATTERN RETURNS FOR THE WEEKEND
INTO EARLY NEXT WEEK. LONG RANGE MODELS ARE IN GOOD AGREEMENT
WITH THE LONGWAVE PATTERN INTO EARLY NEXT WEEK. MAIN POLAR JET
EXTENDS ACROSS THE CENTRAL PACIFIC SOUTH OF 40N AND INTO THE
EASTERN PACIFIC SOUTH OF 50N. A WEAK UPPER LEVEL LOW MOVES INTO
THE YUKON FRI INTO EARLY SAT. AN UPPER LEVEL LOW MOVES EAST
ACROSS THE ALEUTIANS FRI INTO MON WHILE A STRONG UPPER LEVEL
RIDGE BEGINS BUILDING OVER THE CENTRAL GULF ON SAT THEN MOVES
SLOWLY EASTWARD INTO WESTERN CANADA INTO EARLY NEXT WEEK.

AN UPPER LEVEL SHORTWAVE WILL MOVE EAST ACROSS THE NORTHERN GULF
THU NIGHT AND ACROSS THE NORTHERN TWO THIRDS OF THE PANHANDLE
INTO FRI. THIS WILL GENERATE A WEAK SURFACE LOW OVER THE NORTHERN
GULF THU NIGHT WHILE LOW PRESSURE OVER THE SOUTHERN PANHANDLE
MOVES EASTWARD INTO B.C. A SURFACE RIDGE EXTENDING DOWN INTO THE
NORTHEAST PANHANDLE FROM THE HIGH OVER NORTHCENTRAL CANADA WILL
WEAKEN INTO FRI CAUSING THE STRONG NORTH WINDS TO FINALLY
DIMINISH OVER THE LYNN CANAL REGION. OFFSHORE FLOW WILL TURN INTO
ONSHORE FLOW INTO FRI AND HELP ERRODE THE ARCTIC AIRMASS OVER THE
NORTHERN PANHANDLE. THE SHORTWAVE MOVING ACROSS THE REGION WILL
BRING CHC TO LIKELY POPS FOR SNOW OVER THE NORTHWEST PANHANDLE
THU NIGHT AND OVER THE REMAINDER OF THE NORTHERN TWO THIRDS INTO
FRI.

A WARM FRONT ASSOCIATED WITH A SURFACE LOW OVER THE ALEUTIANS
MOVES ACROSS THE EASTERN GULF AND PANHANDLE SAT INTO EARLY SAT
NIGHT BRINGING LIKELY POPS TO SOUTHEAST ALASKA. A WARMER AIRMASS
WILL CONTINUE TO SPREAD INTO THE PANHANDLE WITH PRECIP MAINLY
RAIN ALONG THE COASTAL AREAS WITH A MIX OF RAIN AND SNOW
ELSEWHERE. THE EXCEPTION TO THIS WILL BE THE NORTHERN LYNN CANAL
REGION WHERE COLDER AIR MAY HOLD ON LONGER AND KEEP PRECIP ALL
SNOW. HIGH PRESSURE BUILDS UP OVER WESTERN CANADA SUN INTO MON
WITH HIGH PRESSURE ALOFT OVER THE PANHANDLE AT 850MB AND 700MB.
ONSHORE FLOW WILL TURN TO OFFSHORE OVER ALL BUT THE NORTHWEST
PANHANDLE. WILL DECREASE THE POPS INTO MON BUT KEEP LIKELY POPS
OVER THE NORTHWEST PANHANDLE.

AN UPPER LEVEL LOW MOVES INTO THE WESTERN GULF TUE INTO WED WITH
ANOTHER STRONG RIDGE BUILDING UP OVER THE GULF AND MOVING ACROSS
THE PANHANDLE INTO MID NEXT WEEK. A FRONTAL SYSTEM MOVES ACROSS
THE GULF BRINGING INCREASING CLOUDS WITH A CHANCE OF RAIN AS
EARLY AS WED.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...BLIZ WARNINGS...KLONDIKE HIGHWAY IN ZONE 18 THRU THU AND
      ZONE 29 TNGT/THU
      ...HEAVY SNOW WARNINGS...ZONES 27 AND 28 TNGT/THU MORNING
      ...WIND ADVYS...ALL ZONES EXCEPT 27/28 FOR VARIOUS TIMES.
      ZONE 19 ONLY ALONG COASTAL LYNN CANAL.

MARINE...GALE...PKZ012-013-021-022-031-033-036-041-042
      ...SCA...ALL REMAINING ZONES
      ...HEAVY FREEZING SPRAY WARNING...PKZ011>013-021-022-031
TA/TAR