Small Craft Advisory 394, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 AM ADT SAT APR 29 2006

CORRECTED TIME STAMP ERROR

.DISCUSSION...

ANALYSIS...A COLD UPPER LOW REMAINS OVER THE GULF. WATER VAPOR
IMAGERY SHOWS THREE UPPER LOW CENTERS WITHIN THE LARGER
CIRCULATION...ONE JUST SOUTH OF YAKUTAT...ONE EAST OF KODIAK
ISLAND...AND ANOTHER SOUTH OF THE AKPENN. THE ONE SOUTH OF YAKUTAT
IS WELL DEFINED AND HAS AN ESTIMATED SURFACE PRESSURE OF 995 MB.
THIS LOW IS ROTATING NORTHWESTWARD ACROSS THE NORTHERN GULF. THE
ONE EAST OF KODIAK ISLAND HAS BEEN GRADUALLY DISSIPATING OVER THE
PAST SEVERAL HOURS BUT IS SPREADING SHOWERS WESTWARD TOWARD KODIAK
ISLAND. THE LOW SOUTH OF THE AKPENN IS AN UPPER LOW AND DOES NOT
EXTEND DOWN TO THE SURFACE. IT IS CURRENTLY DROPPING INTO THE BASE
OF THE UPPER TROUGH AND WILL HELP AMPLIFY AND REINFORCE THE TROUGH
OVER MAINLAND ALASKA/GULF OF ALASKA TODAY. WITH ALL OF THE ACTION TO
THE SOUTH SOUTHCENTRAL AND SOUTHWEST ALASKA ARE VERY QUIET TONIGHT
WITH PARTLY CLOUDY SKIES AND ISOLATED SHOWERS. THIS SHOULD LEAD TO
A FAIR NIGHT FOR RADIATIONAL COOLING SUCH THAT TEMPS WILL FALL TO
FREEZING OR BELOW BY MORNING MOST PLACES. COLD ADVECTION CONTINUES
ACROSS THE EASTERN BERING SEA BEHIND THE LOW SOUTH OF THE AKPENN.
GUSTY NORTHERLY WINDS...SNOW SHOWERS...AND COLD TEMPOS CONTINUE
ACROSS THIS REGION. A HIGH AMPLITUDE SHORT-WAVE RIDGE LIES FROM THE
CENTRAL ALEUTIANS TO EASTERN RUSSIA WITH ANOTHER CLOSED LOW OVER THE
SOUTHERN TIP OF KAMCHATKA. HIGH CLOUDS ARE ON THE INCREASE OVER THE
WESTERN ALEUTIANS/BERING AS A FRONT EXTENDING FROM THIS SYSTEM
APPROACHES. FINALLY THERE IS A DEVELOPING LOW LOCATED IN AN UPPER
JET COUPLET AROUND 40N/172E.

MODEL ANALYSIS...LOW SOUTH OF YAKUTAT IS NOT HANDLED WELL BY THE
MODELS. IT IS FURTHER NORTH AND EAST AND STRONGER THAN MODEL
SOLUTIONS. THEREFORE...WILL HAVE TO MAKE MENTAL MODIFICATIONS TO
MODEL SOLUTIONS. THIS LOW WILL ROTATE WESTWARD TODAY ALONG THE
NORTH GULF COAST AND THEN SHOULD DROP SOUTHWARD TONIGHT AS TROUGH
AMPLIFIES IN RESPONSE TO UPPER LOW CURRENTLY DROPPING INTO THE
BASE OF THE TROUGH. OUT WEST MODELS HAVE BEEN INCONSISTENT THE PAST
FEW RUNS WITH DEVELOPING LOW SOUTH OF THE WESTERN ALEUTIANS. A LOOK
AT THE GFS ENSEMBLE SHOWS A MAJORITY OF THE MEMBERS ARE IN LINE
WITH THE OPERATIONAL SOLUTION. THUS WE HAVE DECIDED TO USE THE GFS
SOLUTION FOR THE EVOLUTION OF THIS LOW.

AER SHORT-TERM FORECASTS...MOST OF THE SHOWERS ACTIVITY WILL REMAIN
ALONG THE NORTH GULF COAST TODAY AS LOW MOVES WESTWARD. INLAND EXPECT
AFTERNOON HEATING TO GENERATE A FEW AIR MASS SHOWERS...MAINLY FROM
THE COPPER RIVER BASIN OVER THE CHUGACH AND TALKEETNA MOUNTAINS TO
THE SUSITNA VALLEY. GULF LOW(S) AND UPPER TROUGH WILL VERY SLOWLY
DRIFT EASTWARD SUNDAY AND MONDAY AND SOUTHCENTRAL WILL BE DRIER
OVERALL. WITH AIR ALOFT STILL QUITE COLD ATMOSPHERE WILL REMAIN
UNSTABLE ENOUGH TO  PRODUCE ISOLATED AFTERNOON/EVENING SHOWERS.

ALU SHORT-TERM FORECASTS...WINDS WILL FINALLY DIMINISH BELOW SMALL
CRAFT ACROSS THE EASTERN BERING/AKPENN TODAY AS COLD ADVECTION ABATES
AND RIDGE OF HIGH PRESSURE OVER THE CENTRAL BERING SLIDES EASTWARD.
TEMPS WILL STILL BE QUITE COLD FOR THIS TIME OF YEAR FROM SOUTHWEST
ALASKA TO THE AKPENN/EASTERN ALEUTIANS/PRIBILOFS. WINDS AND MOISTURE
WILL BE ON THE INCREASE ACROSS THE CENTRAL ALEUTIANS TODAY AS LOW
APPROACHES. WITH HIGH PRESSURE OVER THE CENTRAL BERING THERE WILL BE
A TIGHT ENOUGH PRESSURE GRADIENT ACROSS THE ALEUTIANS TONIGHT TO
RESULT IN MINIMUM STORM FORCE WINDS. WINDS WILL DIMINISH AS LOW SINKS
SOUTHWARD LATE SUNDAY. THIS SYSTEM WILL BRING A WARM-UP TO THE
ALEUTIANS TODAY SPREADING TO THE AKPENN SUNDAY AND BRISTOL BAY
MONDAY. AIR IN PLACE IS SO COLD THAT WILL STILL SEE RAIN AND SNOW
AS THIS SYSTEM MOVES THROUGH. BY MONDAY BERING SEA IS BACK INTO THE
COLD ADVECTION ON THE BACK SIDE OF THE LOW.

EXTENDED FORECASTS...DO NOT SEE ANY MAJOR CHANGES IN STORE FOR THE
ANCHORAGE FORECAST AREA. ALEUTIAN LOW AND MERGES WITH THE EVER
PRESENT TROUGH OVER THE MAINLAND MONDAY NIGHT/TUESDAY TO FORM A NEW
LARGE COMPLEX CIRCULATION CENTERED OVER THE AKPENN TUESDAY. THIS WILL
BE SIMILAR TO THE CIRCULATION WE CURRENTLY HAVE OVER THE GULF WITH
MULTIPLE LOWS LIKELY TO FORM AND ROTATE AROUND THE MAIN CENTER. THIS
LOW WILL SLOWLY PROGRESS EASTWARD THROUGH THE EXTENDED LEADING TO
A SHOWERY REGIME FROM THE AKPENN TO THE SOUTHERN MAINLAND. ALTHOUGH
THE CENTRAL BERING WILL SEE SOME COLD ADVECTION THE AIR MASS AS A
WHOLE WILL NOT BE AS COLD AS THE CURRENT ONE. LOOKING OUT TO DAY 7
LOOKS LIKE DEJA VU...ANOTHER UPPER LOW MOVES ACROSS THE ALEUTIANS
AND SETS UP SHOP VICINITY OF THE AKPENN. SO WHILE WE WILL NOT BE AS
COLD WE ARE CERTAINLY NOT LOOKING AT ANY MAJOR WARM-UPS EITHER.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORMS 172 175. GALES 170 176.
FIRE WEATHER...NONE.

SEB APR 06