Small Craft Advisory 378, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
130 PM ADT MON MAY 2 2005

.DISCUSSION...MODELS IS GOOD AGREEMENT ON PATTERN SHIFT TO HAPPEN
OVER THE NEXT 48 HOURS.

UPPER LEVELS...HIGH PRESSURE WEAKENING OVER THE INTERIOR AND SQUEEZED
WEST AS A TROUGH FROM THE MAJOR LOW NORTH OF HUDSON BAY DROPS INTO
ALASKA TODAY. WEAK UPPER LOW LIFTING NORTH AND EAST OVER THE GULF
HELPING AS WELL. THIS LOW TO MOVE INLAND TONIGHT AND WEAKEN. WITH IT
BRINGS SOME INSTABILITY FOR TOMORROWS INITIATION OF CONVECTIVE
ELEMENTS OVER SOUTHCENTRAL ALASKA FOR THE HIGHER TERRAIN. UPPER LEVEL
LOW JUST SOUTH OF DUTCH HARBOR WEAKENING OVER THE NEXT DAY AND LIFTS
NORTHEAST TUESDAY NIGHT AND OVER SOUTHCENTRAL WEDNESDAY AS A STRONG
LOW CROSSES THE DATELINE SOUTH OF ALEUTIAN CHAIN. THIS TO RAISE THE
LEVEL OF INSTABILITY AND INCREASE MOISTURE OVER THE MAINLAND. IN THE
MEANTIME...A STRONG VORT MAX DROPS INTO THE CHUKCHI SEA.
THEREFORE...THE PATTERN SHIFTS FROM EASTERLIES OVER THE MAINLAND TO
WESTERLIES BY TUESDAY NIGHT WITH A TROUGH ALONG 170W FROM THE POLE TO
40N AND A RIDGE OVER THE GULF. UPPER LEVEL LOW IN THE CHUKCHI SEA TO
DROP SOUTHWEST WEDNESDAY INTO FRIDAY OVER THE CENTRAL BERING WHILE
THE LOW SOUTH OF THE ALEUTIAN CHAIN DRIVES NORTHEAST TO THE ALASKA
PENINSULA. THE LOWS BEGIN TO CONSOLIDATE OVER THE WEEKEND WITH A
TROUGH EXTENDING SOUTHEAST FROM THE BERING SEA THROUGH THE SOUTHERN
GULF OF ALASKA AND A RIDGE ALONG THE CANADIAN ROCKIES.

SURFACE SOUTHCENTRAL...WEAK LOW IN THE GULF WORKING EAST TO KODIAK
ISLAND. OVERALL EASTERLY FLOW OVER THE GULF PUSHING MOISTURE TO THE
KODIAK ISLAND AREA. INSTABILITY FROM UPPER LEVEL LOW TO MOVE INLAND
BY TOMORROW TO INITIATE A FEW SHOWERS OVER THE HIGHER TERRAIN. WEAK
TROUGH MOVING NORTH INTO SOUTHCENTRAL WEDNESDAY TO BRING INCREASE IN
MOISTURE AND SHOWER ACTIVITY. THIS IS THE PATTERN SHIFT. THE MOIST
SOUTHWEST FLOW TO REMAIN INTO THURSDAY MORNING. A STRONG LOW MOVING
OUT OF THE NORTH PACIFIC TO APPROACH THE ALASKA PENINSULA THURSDAY.
THIS WILL INCREASE WINDS AND TURN THEM TO THE SOUTHEAST WITH SOME
DOWNSLOPING TO OCCUR IN THE USUAL LOCATIONS IN SOUTHCENTRAL ALASKA AT
THIS TIME. THE LOW WORKS ITS WAY INTO THE EASTERN BERING SEA WITH
STRONG SOUTHEAST FLOW REMAINING OVER MUCH OF SOUTHCENTRAL ALASKA INTO
THE EARLY WEEKEND.

SURFACE SOUTHWEST AND ALEUTIANS...WEAK SURFACE LOW JUST SOUTH OF THE
ALEUTIANS NEAR DUTCH HARBOR BRINGING SCATTERED SHOWERS TO THE EASTERN
ALEUTIANS AND ALASKA PENINSULA. UPPER LEVEL JET STREAK OVER THE
MAINLAND BROUGHT SHOWERS TO SOUTHWEST ALASKA LAST NIGHT WHICH ARE
WANING THIS AFTERNOON. EXPECT THE HEAT OF THE DAY TO INITIATE MORE
SHOWERS THOUGH. JET LEAVES THE AREA TONIGHT. HIGH PRESSURE OVER MUCH
OF THE BERING SEA AT THE SURFACE WITH STRATUS WEST OF THE PRIBILOFS
TO THE REMAINDER OF THE ALEUTIAN CHAIN AND BERING SEA. AS THE SURFACE
HIGH RE-CENTERS OVER SIBERIA...THE STRATUS MOVES FARTHER WEST. THE
LOW NEAR DUTCH TO OPEN UP AND MOVE INTO SOUTHWEST ALASKA TOMORROW AND
OVER SOUTHCENTRAL WEDNESDAY. THIS FEATURE TO INCREASE INSTABILITY IN
THESE AREAS. MAJOR LOW MOVING ACROSS THE DATELINE SOUTH OF THE
ALEUTIANS TONIGHT AND WILL HEAD TOWARD THE ALASKA PENINSULA
WEDNESDAY. WINDS AND PRECIP TO INCREASE OVER THE CENTRAL ALEUTIAN
CHAIN WEDNESDAY AFTERNOON THEN SPREAD TO THE ALASKA PENINSULA
WEDNESDAY NIGHT. THE LOW WILL MOVE INTO THE ALASKA PENINSULA THURSDAY
EVENING WITH RAIN SPREADING OVER SOUTHWEST ALASKA BACK TO THE CENTRAL
ALEUTIAN CHAIN. THE LOW WILL ROTATE BACK INTO THE BERING SEA INTO
SATURDAY WITH RAIN AND MODERATE TO STRONG WINDS AROUND THE LOW FROM
THE CENTRAL BERING SEA INTO SOUTHCENTRAL ALASKA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...ICE JAM FLOOD WATCH ZONE 151
MARINE...NONE
FIRE WEATHER...NONE

JN MAY 05