Heavy Snow in Alaska, December 28, 2002

SOUTHEAST ALASKA FORECAST DISCUSSION
245 AM AST SAT DEC 28 2002

.SYNOPSIS...
.SHORT RANGE...LATEST GOES IR SATELLITE IMAGERY LOOP SHOWS
NMRS CONVCTV CELLS OVR THE ERN GLFALSK WITH THE HVYST OF THESE
CELLS  CIRCULATING ARND A SML LOW MOVG ONSHR NR CAPE DECISION.
A SECOND SGFNT CONVCTV CLUSTER IS TRAINING FM THE NE GLFALSK
THRU PAYA BAY. OCNL SNOW SHWRS ARE OCCURRING OVR MOST SXNS.
EXTRM SRN SE AK IS THE ONLY RGN RPTG RAIN SHWRS.

MODELS ARE IN CLOSE AGREEMENT...SHOWING THE UPR TROF OVR THE
ERN GLFALSK MOVG SLOLY EWD AND BCMG MORE NEGATIVELY TILTED
AS IT ARRIVES OVR THE OUTER CST OF SE AK SAT AFTN.
AS A RSLT THE SNOW SHWR ACTIVITY WL INCRS AND BCM MORE
ORGANIZED AS THE VORTICITY MAX AHD OF THE TROF INCRSS DUE TO
THE NEG TILTING OF THE TROF. MESO ETA BEST SHOWS THE PCPN
PATTERN MORE UNIFORM AND APPEARING MORE LIKE AN ARCED FNTL
BNDRY MOVG OVR THE SE AK PNHDL AND ERN GLF CST SAT AFTN. MAY
CONSIDER ISSUING A SNOW ADVISORY FOR CNTRL AND SRN SE AK
SAT AFTN.

.LONG RANGE...THE UPPER LEVEL TROUGH OVER THE EASTERN GULF MOVES
ACROSS THE PANHANDLE SAT NIGHT WITH A RIDGE BUILDING OVER THE
GULF. THE SURFACE LOW OVER THE NORTHEAST GULF DISSIPATES AS IT
MOVES INTO THE NORTHERN PANHANDLE. THIS WILL RESULT IN SNOW
SHOWERS DISSIPATING ACROSS THE PANHANDLE SAT NIGHT INTO EARLY
SUN.

A LOW PRESSURE SYSTEM TRACKING ACROSS THE NORTHERN PACIFIC MOVES
INTO THE GULF EARLY SUNDAY WITH THE MAIN LOW BECOMING VERTICALLY
STACKED OVER THE SOUTHWEST GULF AND MOVING EAST OVER THE
SOUTHCENTRAL GULF MONDAY. A TRIPLE POINT LOW FORMS OVER THE
NORTHEAST PACIFIC AND BRINGS A 960MB LOW INTO THE CENTRAL GULF BY
EARLY MONDAY. DRY EASTERLY FLOW DEVELOPS ACROSS THE PANHANDLE
AHEAD OF THIS SYSTEM ON SUNDAY KEEPING CONDITIONS DRY IN ALL
ZONES. PRECIPITATION ASSOCIATED WITH THE OCCLUSION SPREADS INTO
THE SOUTHERN HALF OF THE PANHANDLE EARLY MONDAY AND MAY BRIEFLY
START OUT AS SNOW BEFORE CHANGING TO RAIN AS WARMER AIR MOVES UP
FROM THE SOUTH. THE EXCEPTION TO THIS WILL BE THE FAR EASTERN
AREAS WHERE WARMER AIR WILL BE SLOWER TO MOVE IN KEEPING A LONGER
PERIOD OF SNOW. THE OCCLUSION MOVES ACROSS THE NORTHERN PANHANDLE
MON AFTERNOON BUT EXPECT SNOW MIXED WITH RAIN TO BE LIGHT WITH
EASTERLY FLOW ACROSS THE AREA.

LOW BECOMES VERTICALLY STACKED AND FILLS AS IT MOVES SOUTH OF THE
PANHANDLE INTO TUESDAY. AN UPPER LEVEL RIDGE BUILDS NORTHWEST
FROM THE NORTHEAST PACIFIC ACROSS THE GULF WED WITH A SURFACE
HIGH BUILDING OVER NORTHERN BRITISH COLUMBIA. DRY EASTERLY FLOW
WILL BRING A DRYING TREND IN TOWARD MIDWEEK WITH AN UPPER LEVEL
TROUGH ON THU AND A LOW PRESSURE SYSTEM ON FRI BRINGING A CHANCE
OF PRECIPITATION TOWARD THE END OF THE WEEK.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...POSSIBLE SNOW ADVISORY SAT AFTERNOON FOR ZONES
         23..25..26..27..28..29
MARINE...NONE

DED/TAR