Heavy Snow in Alaska, January 27, 2006

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST THU JAN 26 2006

.SYNOPSIS...
.SHORT RANGE...PARENT LOW ALOFT OVER NORTON SOUND HAS LARGE
SCALE CYCLONIC FLOW INCLUDING TROUGH ALOFT THAT EXTENDS SEWD
FROM IT...OVER SEWARD...AND 200 NM OFFSHORE PNHDL.  THIS UPPER
LEVEL TROUGH IS THE SUPPORT FOR THE 994 MB LOW 200 NM SW OF
KETCHIKAN AT THIS TIME.  THE TROUGH ALOFT IS DRIFTING NE AND
WEAKENING...BOTH ARE ENHANCED BY THE WARM SECTOR RIDGE ALOFT
APPROACHING FROM THE SW THAT IS DISCUSSED IN THE NEXT
PARAGRAPH.  THE LOW WILL WEAKEN BELOW 998 MB AND DIFFCULT
TO LOCATE BEFORE A 12Z LANDFALL ON PRINCE OF WALES ISLAND.

THE PARENT LOW ALOFT OVER NORTON SOUND IS BEGINNING TO
PROVIDE UPPER LEVEL SUPPORT FOR 996 MB LOW 600 NM S OF
COLD BAY AT THIS TIME.  GFS SOLN ACCEPTED ON ZONAL TRACK
AND INTENSIFICATION TO 986 MB ABOUT 12Z TONIGHT.  THE
ASSOCIATED OCCLUSION ARCS EASTWARD AND THEN SOUTHEASTWARD
FROM THE LOW...AND HAS AN ASSOCIATED WARM SECTOR RIDGE MOVING
E ACROSS THE GULF OF ALASKA AND AT 500 MB SHOULD BE OVER 150W
BY 00Z.  SUBSIDENCE ASSOCIATED WITH THIS RIDGE ALOFT IS
ALREADY WEAKENING THE DEFORMATION FRONTAL BOUNDAY OVER
EASTERN GULF AND FILLING THE LOW 200 SW OF KETCHIKAN.

THE PARENT LOW ALOFT OVER NORTON SOUND IS ALSO PROIVDING
THE SHORT TRAJECTORY FOR THE ARCTIC AMS IN THE BERING TO
OVER THE GULF.  THIS STRONG COLD ADVECTION OVER THE
COMPARITIVELY WARM GULF WILL BE ENHANCED AS THE LOW ALOFT
MOVES SE OVER THE YUKON KUSKOKWIM DELTA TONIGHT...AND
PROVIDE ENHACEMENT TO THE 996 MB LOW ABOUT 100 NM SE OF
MIDDLETON ISLAND.  GFS FAVORED ON THESE ISSUES BUT NAM
WILL STILL BE CONSULTED FOR PRECIP DATA THROUGH FRI NIGHT
BECAUSE OF PRECIP SOLNS NEED TO DEPICT THE STRONG VERTICAL
MOISTURE FLUX OF SHALLOW UNSTABLE MARINE LAYER OVER GULF.

.LONG RANGE...AM NOT SEEING MUCH IN WAY OF CHANGES FROM CURRENT
THINKING. UPPER LEVEL TROUGH WITH A CLOSED LOW OVER THE NORTHERN
GULF THAT WILL PERSIST AND INTERACTING WITH THE SHORT WAVES IN
THE ZONAL FLOW GENERALLY BETWEEN 40 AND 50 NORTH. FIRST WAVE
MOVES INTO BRITISH COLUMBIA COAST ON SATURDAY...BUT PRECIPITATION
SHOULD BE SOUTH OF THE PANHANDLE. CONTINUED SHOWERS ABOUT THE LOW
OVER THE NORTHERN GULF WILL KEEP THE SHOWERS OVER THE NORTHERN
HALF TO TWO THIRDS OF THE PANHANDLE.

NEXT WAVE MOVING INTO THE SOUTHWEST GULF LATER SATURDAY WILL GET
CAUGHT UP IN THE UPPER LEVEL FLOW AND WILL TURN NORTHWARD INTO
THE NORTH CENTRAL GULF. THE ASSOCIATED FRONTAL BAND WILL SPREAD
INTO THE SOUTHERN PANHANDLE SUNDAY AND THROUGH THE NORTHERN
PANHANDLE SUNDAY NIGHT. PRECIPITATION SHOULD BE SNOW MIXING
WITH/CHANGING TO RAIN FOR THE SOUTHERN HALF OF THE PANHANDLE.
THROUGH TUESDAY EXPECT THE PRECIPITATION TO SHIFT BACK TO THE
MIXED OR ALL SNOW SHOWERS OVER THE SOUTHERN HALF.

THE REMAINS OF THE MAIN LOW WILL REPLACE THE LOW OVER THE
NORTHERN GULF. NEXT SYSTEM MOVING IN WILL ENHANCE THE UPPER
TROUGH OVER THE GULF AND THE RIDGE ALONG THE COASTAL MOUNTAINS.
EXPECT THIS SYSTEM TO CURVE INTO THE SOUTHEAST GULF AS WELL FOR
THE MID WEEK...BUT THEIR IS ENOUGH MODEL DISCREPANCY YET TO TO
JUMP ON ONE BANDWAGON SO THE LONG RANGE STUFF NOT GOING TO SEE
MUCH IN WAY OF CHANGES.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...ADVISORY FOR WIND CHILL AT ELEVATIONS ABOVE SKAGWAY...
ZONE 18.
MARINE...SMALL CRAFT ADVISORY...
          OUTSIDE WATERS...ALL
          INSIDE WATERS...ALL EXCEPT PKZ021 AND 53

JT - BMB