Small Craft Advisory 49, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
1140 AM AST FRI JAN 19 2007

.SYNOPSIS...
.SHORT RANGE...AT 18Z ONE SFC LOW IS FILLING OVER WRANGELL MTNS
AND MOVG N OUT OF THE FCST AREA. ANOTHER LOW CENTER /1001 MB/ IS
LOCATED 250 NM WEST OF DIXON ENTRANCE NEAR 54N 139W. A WEAK SFC
RIDGE LIES E-W ACROSS THE NORTHERN ZONES IN BETWEEN THE LOWS. SFC
PRESSURE OBS AT 18Z ARE A TAD LOWER THAN AUTOMATED ANALYSIS TOOL
AND 6H MODEL PROGS. PRESSURES ARE FALLING OVER SOUTHERN ZONES
AHEAD OF LOW W OF DIX ENTR BUT BELIEVE THIS SYSTEM WILL WEAKEN
AND MOVE ONLY SLIGHTLY NWD THROUGH TONIGHT. SYSTEM WINDING UP AT
40N 165W WILL BE A BIGGER PLAYER FOR SE AK SAT NIGHT.

AMS QUITE MOIST ACROSS THE PANHANDLE TODAY. MVFR CONDS PREVAIL...
GIGS/VSBYS HIGHER IN THE NORTH UNDER WEAK RIDGE. HI POPS TODAY
EVERYWHERE BUT GENERALLY LIGHT AMTS. MODELS MAINTAIN GREATEST
UPWARD MOTION OVER CENTRAL 1/3 OF PANHANDLE ON NE SIDE OF
DIFLUENT AND NEGATIVELY TILTED TROF. WINDS DROPPING OFF TODAY BUT
WILL TAKE UNTIL THIS AFTN FOR SIGFNT DROP OFF IN LYNN CANAL.
CURRENTLY NO PUBLIC ADVISORIES IN EFFECT.

TWO MAIN FCST PROBLEMS ARE SOMEWHAT RELATED: DIFFERNTIATING
BETWEEN LIQUID AND FROZEN PRECIP AND THE EXACT TRACK OF GALE
DEVELOPING OUT AT 40N 165W. BELIEVE THERE WILL BE A TREND TOWARD
DRAINAGE WINDS OUT OF INTERIOR AS LOWS APPROACH FROM THE S AND W.
THIS SHOULD PULL IN COOL ENOUGH TEMPS FOR WET LOW LEVEL SNOWS
THROUGH SAT. STG WARM AIR ADVECTION IS FCST SAT NIGHT INTO SUN
MORNING AHEAD OF DEVELOPING SYSTEM. SNOW LEVEL MAY RISE ABV 4K FT
SOUTHERN ZONES AND UP TO ABOUT 2K FT IN THE N. CONSIDERABLE
SPREAD OF MODEL SOLUTIONS FOR SFC LOW TRACK. ENSEMBLE MEAN
DEPICTS 982MB CENTER MAKING LANDFALL SUN MORNING NEAR OR WEST OF
YAKUTAT BAY. SOME INDIV ENSEMBLE MEMBERS 8 MB DEEPER AND FARTHER
WEST. AFTER COORD WITH ANC WE WILL LEAN TWD DEEPER SOLUTIONS OF
GFS-40 AND NAM. WILL LOWER SFC PRESSURES A BIT IN CURRENT GRID
FCSTS AND MAINTAIN LOW TRACK TWD YAK BAY. BOTTOM LINE IMPACT WILL
BE GALES AND WIND ADVISORIES FOR SAT NIGHT AND SUN MORNING. WILL
HOLD OFF A LITTLE LONGER ON ISSUING ADV STATEMENTS SINCE EVENT IS
STILL 36H AWAY AND TRUST FUTURE MODEL RUNS WILL BETTER DEFINE
SPECIFIC ZONES NEEDING ADVISORIES.

.LONG RANGE...MOST OF THE MODELS APPEAR TO BE IN FAIR AGREEMENT
WITH THE GENERAL SYNOPTIC EVOLUTION OVER THE NEXT FEW DAYS...
ALTHOUGH THERE ARE SOME DISAGREEMENT WITH THE DETAILS. SURFACE
LOW WILL ENTER THE SOUTH CENTRAL GULF LATE SATURDAY...THEN
MIGRATE NORTHWARD THROUGH SUNDAY AND WILL LIKELY REACH THE GULF
COAST IN THE VICINITY OF YAKUTAT LATE SUNDAY NIGHT OR EARLY
MONDAY MORNING. THERE IS SOME DIFFERENCE IN THE DEPTH OF THE LOW.
THE GFS IS THE DEEPEST AND THE ETA IS THE WEAKEST. WILL LIKELY
TAKE A COMPROMISE OF THE TWO SOLUTIONS WITH THE INTENSITY WHICH
WOULD LOWER THE SURFACE PRESSURES A LITTLE BIT FROM WHAT IS
CURRENTLY IN THE GRIDS.

AFTER THIS LOW GOES INLAND...HIGH PRESSURE...BOTH AT THE SURFACE
AND ALOFT...BUILD ACROSS SOUTHEAST ALASKA THROUGH THE FIRST HALF
OF NEXT WEEK. THIS WILL CREATE AN OFFSHORE FLOW OVER A LARGE PART
OF SOUTHEAST...WITH THE EXCEPTION OF THE FAR NORTHERN PART AND
NORTHEAST GULF COAST. POPS WILL BE ON THE DECREASE OVER THE
CENTRAL AND SOUTH...AND REMAIN THAT WAY THROUGH MID WEEK.

MID LEVEL RIDGE BEGINS TO SHIFT EASTWARD DURING THE DAY WEDNESDAY
AND SURFACE LOW DEVELOPS OVER THE CENTRAL GULF. ONSHORE FLOW
RESUMES AREAWIDE EARLY WEDNESDAY AND POPS WILL ONCE AGAIN BE ON
THE INCREASE.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...NONE
MARINE...SCA THROUGH FRI NIGHT ALG OUTER COAST. SCA THROUGH THIS
         AFTN LYNN CANAL/CROSS SND.