Small Craft Advisory 381, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
155 PM ADT TUE MAY 3 2005

.DISCUSSION...MODELS IN A BIT OF DISAGREEMENT. THE BIG DISAGREEMENT
IS THE SURFACE PRESSURE STRUCTURE OVER THE EASTERN BERING SEA
WEDNESDAY NIGHT INTO THURSDAY. FEEL WITH THE JET STRUCTURE ASSOCIATED
WITH THE LOW NEAR THE ALEUTIAN CHAIN AT THIS TIME...THAT THE NAM HAS
THE BETTER REPRESENTATION OF THE SURFACE PATTERN. MODELS START TO
DIFFER LATER AS WELL AND WILL DEFER TO NAM THERE AS WELL WITH THE
CUTOFF LOW IN THE SOUTHERN GULF OF ALASKA. IT ALL HAS TO DO WITH THE
POSITION OF THE UPPER LEVEL LOW OVER THE BERING SEA...AND DUE TO THE
FACT THE GFS ENSEMBLE MEAN MATCHES MORE CLOSELY WITH NAM.

WEAK UPPER LEVEL LOW MOVING INLAND OVER THE NORTHEASTERN GULF COAST
TODAY WITH A LOW IN THE BERING STRAIT AND ANOTHER OVER THE WESTERN
ALASKA PENINSULA. STRONG UPPER LEVEL LOW CROSSING THE DATELINE NEAR
45N AS WELL. PATTERN SHIFT IS ON THE WAY AS THE RIDGE IS WELL INTO
NORTHEAST RUSSIA. SOUTHWEST FLOW ESTABLISHING ITSELF OVER THE
MAINLAND WITH THE RIDGE AXIS ALONG THE WEST COAST OF CANADA. THE LOW
MOVING ONTO THE GULF COAST TO DISSIPATE OVER THE YUKON TONIGHT. THE
LOW NEAR THE ALASKA PENINSULA TO OPEN UP AND MOVE ACROSS THE MAINLAND
WEDNESDAY. VORT MAX MOVING SOUTH THROUGH THE BERING STRAIT TO WRAP
INTO THE LOW SOUTH OF THE ALEUTIAN CHAIN WEDNESDAY NIGHT. BY THIS
TIME...THE LOW SOUTH OF THE ALEUTIAN CHAIN SHOULD BE SOUTH OF DUTCH
HARBOR AND HEADING TOWARD THE ALASKA PENINSULA. IN ADDITION...A
SECOND VORT MAX/WAVE DROPS THROUGH THE BERING STRAIT AND INTO THE
CENTRAL BERING SEA BY FRIDAY. THIS LOW BECOMES THE DOMINANT LOW WITH
THE ALASKA PENINSULA LOW DISSIPATING AS IT WRAPS INTO THIS LOW.
HOWEVER...A PIECE OF THE ALASKA PENINSULA LOW WILL MOVE INTO THE
SOUTHEAST GULF AND DEVELOP INTO A CUTOFF LOW THIS WEEKEND. THE LOW
OVER THE BERING SEA DEVELOPS A DOUBLE CENTER STRUCTURE OVER THE
WEEKEND AS WELL.

SURFACE SOUTHCENTRAL...SLIGHTLY UNSTABLE AIR MASS OVER THE AREA WITH
CONVECTION EXPECTED OVER THE TERRAIN TO DRIFT INTO THE VALLEYS THIS
EVENING. KODIAK AND SOUTHERN KENAI PENINSULA BECOMING UNDER THE
INFLUENCE OF THE OPENING UP LOW OVER THE ALASKA PENINSULA. THIS WILL
INCREASE CLOUDS AND CHANCE OF PRECIP FARTHER NORTH OVERNIGHT AND OVER
ALL OF SOUTHCENTRAL TOMORROW. CONVECTIVE INSTABILITY WILL BE A BIT
LESS AS LOSE SOME SOLAR INFLUENCE. THIS UPPER LEVEL DISTURBANCE TO
PASS BY WEDNESDAY EVENING AND MUCH OF SOUTHCENTRAL WILL BE RELEGATED
TO ISOLATED SHOWERS OVER THE TERRAIN BY THURSDAY EXCEPT THE SOUTHERN
KENAI PENINSULA AND POINTS SOUTH. KODIAK AND THE WESTERN GULF START
TO BECOME UNDER THE INFLUENCE OF THE STRONG LOW SOUTH OF DUTCH
WEDNESDAY NIGHT INTO THURSDAY. WINDS WILL INCREASE FROM THE SOUTHEAST
AND WITH THE RIDGE BUILDING OVER THE EASTERN GULF...COULD SEE SOME
TURNAGAIN ARM WINDS AND TYPICAL CHANNELED FLOW IN THIS PATTERN DOWN
THE INLET AND SHELIKOFF STRAIT. THE LOW WILL PUSH INTO BRISTOL BAY BY
FRIDAY WITH CONTINUED STRONG SOUTHEAST FLOW. PRECIP WILL RESEMBLE A
DOWNSLOPE TYPE PATTERN WITH ANCHORAGE BOWL...NORTHWESTERN KENAI AND
MAT VALLEY REMAINING MOSTLY DRY BUT CLOUDY AND COASTAL LOCALES AND
WESTERN SUSITNA VALLEY WET.

SURFACE SOUTHWEST AND ALEUTIANS...OPENING LOW OVER THE ALASKA
PENINSULA AND SLIGHTLY UNSTABLE AIR MASS OVER SOUTHWEST ALASKA
FAVORABLE TO SHOWER ACITIVITY LATE THIS AFTERNOON. SHOWER ACTIVITY
BECOMING MORE WIDESPREAD AS THE DISTURBANCE WORKS ACROSS THE AREA
TONIGHT. REMNANT CLOUDS AND WEAKLY UNSTABLE AIR MASS TOMORROW WILL
BRING SCATTERED SHOWERS TO SOUTHWEST AGAIN. STRONG VORT MAX MOVING
SOUTH OUT OF THE BERING STRAIT SUPPORTING MODERATE TO STRONG
NORTHERLY WINDS OVER THE WESTERN BERING SEA THROUGH TONIGHT AS IT
RUNS SOUTH TO MERGE WITH THE LOW SOUTH OF THE ALEUTIAN CHAIN
TOMORROW. THE LOW SOUTH OF THE ALEUTIAN CHAIN WORKS NORTHEAST
TOMORROW NEARER THE ALEUTIAN CHAIN INCREASING WINDS OVER CENTRAL AND
EASTERN ALEUTIAN CHAIN. SURFACE HIGH RETREATS TO THE NORTHWEST WITH
THE LOW MOVING NORTH. THE LOW WORKS TO THE WESTERN ALASKA PENINSULA
BY THURSDAY NIGHT WITH PLENTY OF MOISTURE AND WIND WRAPPED AROUND
THIS LOW FROM THE CENTRAL BERING SEA TO SOUTHWEST ALASKA. THE LOW
BEGINS TO WEAKEN FRIDAY AND DEVELOPS A DOUBLE CENTER STRUCTURE AS IT
LOSES JET SUPPORT SINCE THE MAIN JET REMAINS SOUTH OF THE CHAIN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...ICE JAM FLOOD WARNING 151
MARINE...GALE 5B 12A 12B 13A 14
FIRE WEATHER...NONE

JN MAY 05