Gale Warning 20, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST FRI JAN 5 2007

.SYNOPSIS...
.SHORT RANGE...GOES IR SHOWS EXTENSIVE CONVECTIVE ENVIRONMENT
OVER ENTIRE FORECAST DOMAIN...EXCEPT NEAR CAPE FAIRWEATHER
WHERE FILLING REMAINS OF 980 MB LOW INCLUDES CIRCULATION
THAT SHOULD HAVE LAST OF WARM LAYER ALOFT AND ANY FRONTAL
INVERSIONS.  SHOWERS MAY BE GLIDING UP A FRONTAL BOUNDARY
OVER HAINES VICINITY...AND IS LIKELY A REASON FOR THE
CONVECTIVE ENHANCEMENT THAT IS SHOWNING UP AT HAINES AS
HEAVY SNOW AT THIS TIME.

MODEL CONSENSUS IS THAT THE REMAINS OF THE LOW MAKING LANDFALL
NEAR CAPE FAIRWEATHER WILL MOVE EAST BEYOND THE NORTHERN
PANHANDLE ABOUT 03Z.  SNOW ADVISORY IS BEING PREPARED FOR
HAINES BUT HEAVY SNOW SHOWERS SHOULD SHUTOFF ABOUT 03Z-06Z
THIS EVENING.

LIFTING OF CONVECTIVE CELLS SHOULD WEAKEN OVER ALL PNHDL
AND EASTERN GULF COAST BY 06Z AS LAST OF BROAD TROUGHS
ALOFT WILL BE MOVING EAST PAST THE FORECAST DOMAIN.

AFTER THE WEAKENING OF CONVECTION...THE NEXT IMPORTANT
CHANGES ARE ASSOCIATED WITH A LOW THAT IS CURRENLY DEVELOPING
ABOUT 600 NM S OF ADAK.  GFS190 12Z RUN USED FOR THE LOW
TRACK ONSHORE THE SOUTHERN PANHANDLE SAT NIGHT.  THIS GFS190
RUN WILL ALSO BE EMPHASISED FOR SENSIBLE WEATHER FIELDS.
CONFIDENCE IN THIS SOLUTION IS ONLY FAIR AS A VARIETY OF
SOLUTIONS ARE AVAILABLE.  SHORT RANGE ENSEMBLE FORECAST
DEPICTS AN UNUSUALLY WIDE SPREAD OF SURFACE PRESSURE OVER
MOST OF PANHANDLE FOR 12Z SUN.  THE TWO MAIN REASONS FOR
USING THE 12Z GFS190 ARE...FIRST...SIMILARITY TO SREF MEAN.
SECOND IS THAT THE POLAR FRONT ZONE CONFIGURATION IS
RELATIVELY SIMPLE AND THE GFS TENDS TO VERIF WELL IN
SUCH CASES.

.LONG RANGE...
AFTER LANDFALL OF THE SURFACE LOW OVER SOUTHERN SE AK SAT NIGHT A
COLD VERTICALLY STACKED LOW SETTLES INTO THE NORTH CENTRAL GULF
OF AK BY EARLY MON. THE UPPER LOW DRIFTS SOUTHEASTWARD AS HIGH
PRESSURE BUILDS OVER THE GULF AND INTERIOR AK BEHIND IT. ENSEMBLE
MEAN IS SIMILAR TO THE OPERATIONAL GFS IN THE DEPTH AND POSITION
OF THE UPPER LOW BUT SHOWS CONSIDERABLE SPREAD WITH THE
ASSOCIATED LONGWAVE TROUGH SOUTH OF 50N IN THE STRONG BAROCLINIC
REGION.  THIS LEAVES SOME UNCERTAINTY AS TO THE NATURE OF A
SECOND SURFACE LOW DEVELOPMENT IN THAT REGION. BEST SOLUTION IS
THE ENSEMBLE MEAN THAT MOVES A WEAK SURFACE LOW OVER DIXON
ENTRANCE BY EARLY TUE WHILE THE LOW IN THE NORTHEAST GULF SLOWLY
WEAKENS.

SNOW SHOWERS ARE EXPECTED TO CONTINUE INTO THE BEGINNING OF THE
WEEK BUT SOUTHERN AND COASTAL SECTIONS OF THE PANHANDLE MAY
RECEIVE SOME ENHANCED SNOWFALL ON TUE.

THE UPPER RIDGE MOVES SLOWLY EASTWARD REACHING THE EASTERN GULF
AND YUKON TERRITORY BY EARLY THU. SURFACE HIGH PRESSURE SHOULD
INTENSIFY IN THE YUKON BY MID WEEK WITH COLD AND DRY CONDITIONS
PERSISTING WED THROUGH EARLY THU.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...NOTE AMD BEING PREPARED THAT WILL GIVE SNOW
ADVISORY FOR ZONE 19 INCLUDING HAINES.
MARINE...GALE 22 41-51
         SMCR ELSEWHERE XCP 11 AND 12

JT/CFD