Small Craft Advisory 682, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT FRI AUG 28 2009

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL PATTERN REMAINS UNCHANGED WITH A NEUTRALLY TILTED LONG
WAVE UPPER TROUGH LOCATED OVER CENTRAL ALASKA AND THE NORTHWESTERN
GULF. MAIN FEATURES OF INTEREST INCLUDE THE MULTIPLE STRONG SHORT
WAVES ROTATING AROUND THE BASE OF THE UPPER TROUGH IN THE GULF. UPPER
LEVEL RIDGE IS BUILDING OVER THE CENTRAL AND WESTERN BERING SEA WHILE
ANOTHER COLD CORE UPPER LEVEL LOW IS ROTATING ACROSS THE SEA OF
OKHOTSK...WEST OF THE KAMCHATKA PENINSULA.

AT THE SURFACE...
TWO SURFACE LOWS ARE MERGING SOUTH OF KODIAK THIS AFTERNOON AND WILL
BECOME ONE LARGE LOW THAT WILL MEANDER ABOUT THE GULF THROUGH THE
WEEKEND AS IT SLOWLY WEAKENS. HIGH PRESSURE IS BUILDING OVER THE
NORTHERN PACIFIC AND SPREADING ITS INFLUENCE INTO THE BERING SEA.
WIDESPREAD STRATUS AND FOG WILL REMAIN A THREAT ACROSS THIS REGION.

.MODEL DISCUSSION...MODELS ARE IN REASONABLE AGREEMENT CONCERNING THE
OVERALL PATTERN BUT DIFFER IN THE DETAILS. ALL MODELS SWING THE NEW
LOW TOWARD THE CENTRAL GULF SATURDAY AFTERNOON BEFORE WEAKENING IT
AND DROPPING IT SOUTHEAST OUT OF OUR DOMAIN BY EARLY MONDAY MORNING.
THE DIFFERENCES ARISE WITH THE STRENGTH OF THE LOW AND HOW FAR IT
MOVES NORTH BEFORE GETTING CAUGHT UP IN THE UPPER FLOW AND SHIFTING
SOUTHEAST. WE FEEL THAT THE STRONGER AND MORE NORTH SOLUTION
ADVERTISED BY THE NAM IS THE BEST AT THIS TIME. MAIN EDITS WILL BE
CONCERNING THE SHORT TERM EFFECTS OF THIS SLIGHT CHANGE FROM PREVIOUS
RUNS...WHILE MID AND LONG RANGE FORECAST WILL BE LEFT AS IS.

.SHORT TERM FORECAST...

.SOUTHCENTRAL ALASKA...WIDESPREAD RAIN ASSOCIATED WITH THE FIRST OF
TWO SHORTWAVES TO CROSS THE COAST TODAY. WINDS BEHIND THIS FIRST
OCCLUSION HAVE INCREASED TO MINIMUM GALES ACROSS MOST OF THE COASTAL
WATERS...AND INCREASED THE GAP WINDS TO STRONG WIND CRITERIA FOR
SEVERAL ZONES. A POSSIBLE BARRIER JET FORMED ALONG THE COAST NEAR
CORDOVA WHERE WINDS GUSTS IN EXCESS OF 65 MPH WERE REPORTED FOR 4
HOURS STRAIGHT. WINDS HAVE INCREASED THROUGH PORTAGE VALLEY AND ARE
LIKELY MOVING DOWN TURNAGAIN ARM EARLY THIS AFTERNOON. RAIN WILL
TAPER OFF INLAND BY MORNING AS FLOW ALOFT BECOMES MORE NORTHERLY IN
RESPONSE TO THE LOW SHIFTING FURTHER AWAY. COASTAL ZONES AND THE
COPPER RIVER BASIN WILL HOLD ON TO THE CLOUDS AND MOISTURE THE
LONGEST...BUT BY SUNDAY SHOULD SEE FAIR WEATHER AGAIN WITH SOME
BROKEN MID TO HIGH LEVEL CLOUDS.

A TRANSITORY RIDGE MOVES OVER SOUTHCENTRAL MONDAY AND THEN
SOUTHWESTERLY FLOW ALOFT QUICKLY MOVES IN BEHIND THE RIDGE BY MID
WEEK...BRINGING WITH IT MORE CLOUDS AND THE CHANCE FOR RAIN.

.SOUTHWEST ALASKA...
MOSTLY CLEAR SKIES AND SEASONAL TEMPERATURES PREVAILING FOR THE
SOUTHWEST INTERIOR TODAY. SOME CLOUDS AND FOG ARE BUTTING UP AGAINST
THE ALEUTIAN MOUNTAINS BUT OTHERWISE A BEAUTIFUL START TO THE WEEKEND
FOR MOST OF THE SOUTHWEST. WHILE THE INTERIOR SHOULD REMAIN CLEAR
THROUGH SATURDAY...ONSHORE FLOW WILL RETURN LOW CLOUDS AND FOG ALONG
THE COAST ESPECIALLY THE KUSKOKWIM DELTA AND ALASKA PENINSULA. HIGH
CLOUDS WILL RETURN TO THE KUSKOKWIM VALLEY TOMORROW NIGHT WITH SOME
SHOWERS POSSIBLE SUNDAY AS THE MOISTURE MOVES FURTHER INLAND. BY
EARLY NEXT WEEK...THE RIDGE WILL SHIFT EAST AND ANOTHER LONG WAVE
TROUGH WILL MOVE OVER THE CENTRAL BERING SEA RESULTING IN A LONG
FETCH OF MOISTURE FEEDING THE COASTAL ZONES. MOSTLY CLOUDY SKIES AND
NUMEROUS SHOWERS UNDER THE UPPER TROUGH SHOULD PREVAIL THROUGH THE
REMAINDER OF THE WEEK.

.BERING SEA/ALEUTIANS...
THE ACTIVE PATTERN ACROSS OUR DOMAIN WILL BRING PERIODS OF STRATUS
AND FOG...FOLLOWED BY A GALE FORCE FRONT AND THEN SHOWERS ON THE
BACKSIDE. THAT IS THE FORECAST FOR THE BERING SEA FOR THE NEXT 6 DAYS
IN A NUTSHELL. WIDESPREAD FOG AND STRATUS WILL PREVAIL UNTIL A FRONT
ASSOCIATED WITH THE SEA OF OKHOTSK LOW MOVES ACROSS THE WESTERN
ALEUTIANS DURING THE WEEKEND. THIS FRONT WILL WEAKEN AS IT MOVES
TOWARD THE CENTRAL AND EASTERN ALEUTIANS EARLY NEXT WEEK. THE MAIN
BAND OF MOISTURE MOVES INTO BRISTOL BAY AND SOUTHCENTRAL ALASKA
MIDWEEK WHILE WIDESPREAD SHOWERS DEVELOP ON THE BACKSIDE OF THE LOW
UNDER THE LARGE UPPER TROUGH.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WATCH ZONE 141.
MARINE...GALE WARNING 120 155 170 176 411 412.
FIRE WEATHER...NONE.

AB AUG 09