Small Craft Advisory 327, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT FRI APR 11 2008

.ANALYSIS AND UPPER LEVELS...
THE MAIN UPPER TROUGH REMAINS OVER CENTRAL ALASKA WITH JET STREAM
WELL TO OUR SOUTH. SEVERAL VORTICITY MAXIMA ARE MAKING THEIR WAY
AROUND THE MAIN TROUGH...THE MOST POTENT OF WHICH IS IN THE PRINCE
WILLIAM SOUND AREA. THIS PARTICULAR VORT MAX CONTINUES TO BRING SNOW
SHOWERS TO COASTAL AREAS AND INTO THE COPPER RIVER BASIN EARLY THIS
MORNING. THIS WILL TRACK NORTHEASTWARD TODAY AS THE MAIN TROUGH
SLOWLY PUSHES EAST. A RIDGE OF HIGH PRESSURE CURRENTLY OVER THE
CENTRAL ALEUTIANS WILL SLIDE EASTWARD KEEPING A GOOD PORTION OF
SOUTHCENTRAL AND SOUTHWEST ALASKA IN A DRY WEATHER PATTERN THROUGH
THE WEEKEND. A LOW WELL SOUTH OF OUR DOMAIN WILL MOVE NORTHWARD
TOWARDS THE EASTERN GULF OF ALASKA BY SATURDAY. OUT WEST...THERE ARE
TWO WEATHER SYSTEMS OF NOTE. ONE CURRENTLY JUST OFF THE COAST OF
RUSSIA WILL TRACK EASTWARD AND MOVE TO THE KUSKOKWIM DELTA BY FRIDAY
NIGHT. THE SECOND IS A LARGER SCALE SYSTEM CURRENTLY NEAR JAPAN THAT
WILL APPROACH THE WESTERN ALEUTIAN ISLANDS BY SATURDAY NIGHT WITH ITS
ASSOCIATED WEATHER FRONT JUST OFF THE SOUTHWEST MAINLAND BY THAT
TIME.

.MODEL DISCUSSION...
ALL MODELS HAVE INITIALIZED THE LOW WELL SOUTH OF OUR DOMAIN
POORLY...PLACING THE SURFACE LOW FURTHER NORTH THAN WHERE IT APPEARS
ON SATELLITE. NOT TERRIBLY SURPRISING CONSIDERING ITS HIGHLY
BAROCLINIC NATURE...BUT THE NUMERICAL MODELS HANDLE THE LOW SIMILARLY
AS IT MOVES INTO THE EASTERN GULF. THE NAM CONTINUES TO HANDLE
MESOSCALE FEATURES IN THE EASTERN PRINCE WILLIAM SOUND AREA THE BEST
AND IS USED AS GUIDANCE IN THE SHORT TERM. THE GFS IS THE MODEL OF
CHOICE IN THE MEDIUM RANGE AND OUT WEST BASED ON ITS HANDLING OF
SYNOPTIC FEATURES. ONE AREA OF CONCERN WILL BE THE SPEED OF THE
SYSTEM MOVING INTO THE BERING SEA BY SUNDAY. BOTH THE NAM AND GFS
HAVE BEEN TRENDING THE SYSTEM FASTER AND HAVE CAUGHT UP TO THE
ECMWF...WHICH HAS PROVEN TO BE THE MOST CONSISTENT MODEL.

.SHORT TERM FORECAST...
SOUTH AND EAST OF THE ALASKA RANGE...
SNOW SHOWERS WILL BEGIN TO TAPER OFF AROUND PRINCE WILLIAM SOUND AND
THE COPPER RIVER BASIN TODAY AND TONIGHT AS THE UPPER SHORTWAVE MOVES
NORTH AND EAST. RESIDUAL MOISTURE BEHIND THE STORM HOWEVER MAY KEEP A
LOW DECK OF STRATUS FOR ANOTHER DAY OR TWO. ELSEWHERE...A FAIRLY
CLEAR DAY IS IN STORE FOR THE SUSITNA VALLEY SOUTH TO THE KENAI
PENINSULA TODAY AND PROBABLY THROUGH THE WEEKEND. THIS MORNINGS
ANCHORAGE SOUNDING IS SHOWING 43 J/KG OF CAPE...WHILE NOT IMPRESSIVE
IT CERTAINLY IMPLIES THAT THE ATMOSPHERE IS SHOWING SIGNS OF
INSTABILITY. WITH MODEST RADIATIONAL HEATING AND THE LINGERING COLD
TROUGH ALOFT...THERE CERTAINLY IS POTENTIAL TO SEE SOME MINOR
CONVECTIVE DEVELOPMENT AND A POSSIBLE SHOWER OVER THE WEST FACING
MOUNTAIN SLOPES. THE PATTERN OF COOL NIGHTS AND RELATIVELY CLEAR DAYS
WILL PERSIST THROUGH THE WEEKEND...WHEN A WEATHER FRONT WILL APPROACH
FROM THE WEST AND BRING ANOTHER CHANCE FOR PRECIPITATION.

SOUTHWEST MAINLAND AND ALEUTIANS...
A RELATIVELY QUICK AND WEAK LOW PRESSURE SYSTEM NEAR RUSSIA WILL MOVE
ACROSS THE BERING SEA TODAY AND SKIRT THE WEST COAST TONIGHT BEFORE
DISSIPATING. THIS SYSTEM WILL BRING SNOW AND BLOWING SNOW TO THE
KUSKOKWIM DELTA AND THE PRIBILOFS AND A CHANCE FOR SNOW ALONG MOST OF
THE BRISTOL BAY COAST. FURTHER INLAND...THE TREND OF LARGE DIURNAL
TEMPERATURE RANGES WILL CONTINUE THROUGH THE WEEKEND UNDER MOSTLY
CLEAR SKIES. THE NEXT LOW PRESSURE SYSTEM IS FAIRLY WARM AND WILL
BEGIN IMPACTING THE WESTERN ALEUTIANS THIS AFTERNOON. BY THE END OF
THE WEEKEND...LOW PRESSURE WILL ENCOMPASS MOST OF THE BERING SEA AND
MOST LOCALES WILL HAVE A FAIR CHANCE AT PRECIPITATION.

.LONG TERM FORECAST...
FAIRLY PROGRESSIVE PATTERN WILL BE IN PLACE BY EARLY NEXT WEEK AS THE
CURRENT HIGH-AMPLITUDE RIDGE AND TROUGH COUPLET WILL BE REPLACED WITH
A SERIES OF QUICK MOVING LOWS AND HIGHS. THE CHANCE OF PRECIPITATION
WILL BE DIFFICULT TO PREDICT AT ANY GIVEN TIME...BUT THAT IS FAIRLY
NORMAL FOR THE TRANSITION PERIOD THAT WE ARE UNDERGOING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 121 129 130 132 172 175 176 351 352 411 412 413 414.
FIRE WEATHER...NONE.

DANG APR 08