Small Craft Advisory 39, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST MON JAN 15 2007

.SYNOPSIS...
.SHORT RANGE...LATEST SATELLITE IMAGERY AND OBSERVATIONS INDICATE
A LOW AROUND 991 MB JUST OFF THE COAST OF SITKA AROUND 18Z. A DRY
SLOT IS EXTENDING OVER THE PANHANDLE AS FAR NORTH AS THE
NORTHEAST PANHANDLE (SKAGWAY AND HAINES AREA). A DEFORMATION BAND
NORTH AND WEST OF THE LOW EXTENDS FROM THE SOUTHWEST YUKON OVER
THE FAIRWEATHER REGION INTO THE NORTHEAST GULF. THE UKMET IS THE
MODEL OF CHOICE WITH THIS SYSTEM AND WEAKENS THE LOW AS IT MOVES
NORTHEAST INTO THE SOUTHERN YUKON BY 00Z.

WIND ADVISORY GUSTS OVER THE CENTRAL AND SOUTHERN PANHANDLE WILL
THEREFORE DIMINISH THIS AFTERNOON WHILE WIND ADVISORY GUSTS
DEVELOP OVER THE LYNN CANAL-SKAGWAY REGION AND CONTINUE THROUGH
THE EARLY OVERNIGHT HOURS AS THE LOW REMAINS TO THE NORTH. WINDS
IN THE CENTRAL TO SOUTHERN INNER CHANNELS WILL DIMINISH TO SMALL
CRAFT OR LESS WHILE GALES DEVELOP IN LYNN CANAL AND DIMINISH LATE
TONIGHT.

THE DEFORMATION BAND WILL WEAKEN AS IT MOVE ACROSS THE NORTHERN
PANHANDLE LATE THIS AFTERNOON AND EVENING. PRECIP TYPE IS GOING
TO BE TRICKY BECAUSE SOUTHERLY FLOW WILL DEVELOP AS THIS BAND
MOVES ACROSS AND WILL LIKELY KEEP PRECIP RAIN OR RAIN-SNOW MIX AT
AT TIMES AT SEA LEVEL. HOWEVER...WILL CONTINUE THE SNOW ADVISORY
FOR ZONE 19 (HAINES) TO TAKE INTO ACCOUNT THE SNOWFALL OVER THE
HIGHER ELEVATIONS AND ADD A SNOW ADVISORY FOR THE HIGHER
ELEVATIONS OF ZONE 18 (SKAGWAY). OTHER AREAS WILL SEE RAIN MIXING
WITH OR CHANGING TO SNOW INTO THE EVENING BUT DO NOT EXPECTED A
LOT OF ACCUMULATION. HYDER IN ZONE 29 WILL CONTINUE TO SEE SNOW
THIS MORNING BUT A SOUTHERLY PUSH DOES LOOK LIKELY THIS AFTERNOON
SO ENDING THE HEAVY SNOW WARNING THIS AFTERNOON LOOKS GOOD.

A COLDER AIRMASS MOVING IN BEHIND THIS SYSTEM AND WEST TO
SOUTHWEST FLOW AT ALL LEVELS LATE TONIGHT AND TUE WILL BRING
SCATTERED SNOW SHOWERS TO ALL AREAS. A FAIRLY STRONG UPPER LEVEL
TROUGH WITH GOOD PVA WILL MOVE ACROSS THE PANHANDLE LATE TONIGHT
AND EARLY TUE AND POSSIBLY ENHANCE THE SNOW SHOWER ACTIVITY. A
BRIEF RIDGE WILL BUILD OVER THE PANHANDLE LATE TOMORROW AFTERNOON
AND EVENING WITH SHOWERS TAPERING OFF. THE NEXT FRONT APPROACHES
LATE TUE NIGHT AND SPREADS RAIN AND SNOW ALONG THE COAST AND SNOW
INLAND. GALES WILL DEVELOP OVER THE NORTHERN GULF WITH SMALL
CRAFT WINDS OVER THE EASTERN GULF.

.LONG RANGE...LONG RANGE MODELS ARE IN GENERAL AGREEMENT WITH THE
OVERALL LONGWAVE PATTERN. THE UPPER LEVEL RIDGE IN THE EASTERN
GULF OF AK MOVES EAST OF THE PANHANDLE DURING THE DAY WED AND
PERSISTS IN THAT LOCATION INTO THE WEEKEND. MEANWHILE THE UPPER
LONGWAVE TROUGH OVER THE PACIFIC NEAR THE DATELINE DIGS DEEPER IN
THE LATER PART OF THE WEEK AND THEN PROGRESSES SLOWLY EASTWARD
OVER THE WEEKEND. THIS COMBINATION RESULTS IN A PERSISTENT
SOUTHWESTERLY FETCH OVER THE GULF OF AK WITH A NUMBER OF
SHORTWAVES THAT MOVE INTO THE GULF AND THOUGH SOUTHEAST ALASKA
FROM MID WEEK INTO EARLY NEXT WEEK.

ENSEMBLES SHOW CONSIDERABLE SPREAD WITH INDIVIDUAL SHORTWAVES SO
THE TIMING AND INTENSITY OF WIND EPISODES IN THE EXTENDED WILL
HAVE SOME UNCERTAINTY BUT ONSHORE FLOW ALOFT WILL KEEP A HIGH
LIKELYHOOD OF PRECIPITATION IN MOST SECTIONS THROUGH THE PERIOD.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...SNOW ADV 19 20 WND ADV 23 25 26-29 HVY SNOW 29
MARINE...GALES 31 33-36 41-43 SCA 12 13 21 22 51 52

TAR/CFD