Small Craft Advisory 195, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
115 PM AKST SUN MAR 13 2011

.ANALYSIS AND UPPER LEVELS...NO MAJOR CHANGES FROM PREVIOUS FORECAST
DISCUSSIONS WITH A BLOCKING HIGH ENTRENCHED OVER THE BERING STRAIT
AND A DIFFUSE UPPER LEVEL LOW NEAR THE ALASKA PENINSULA. THE HIGH
PRESSURE EXTENDS SOUTH TOWARD THE WESTERN ALEUTIANS WHILE A WEAK
INVERTED TROUGH EXTENDS FROM THE AKPEN TOWARD SOUTHCENTRAL ALASKA.
ISOLATED TO SCATTERED SHOWERS PERSIST AROUND THE PERIPHERY OF THE
UPPER LEVEL LOW. STRATUS AND LIGHT PRECIPITATION IS PREVAILING UNDER
THE SURFACE HIGH PRESSURE OVER PORTIONS OF THE BERING SEA.

.MODEL DISCUSSION...SOME DISAGREEMENT BETWEEN THE MODELS AS THE
EVOLUTION OF THE BROAD TROUGH IS NOW NOT SO CERTAIN EARLY NEXT WEEK.
A FEW LOWS WILL DEVELOP AND MOVE TOWARD THE PANHANDLE THE NEXT 48
HOURS. THERE IS SIGNIFICANT DISAGREEMENT REGARDING THE SECOND LOW
DEVELOPING MONDAY NIGHT. THE NAM AND ECMWF ARE PICKING UP ON MULTIPLE
CENTERS WHILE THE GFS WANTS TO HOLD ON TO A SINGLE LOW. THE
OPERATIONAL RUN OF THE GFS IS SIGNIFICANTLY DIFFERENT FROM THE
MEAN...LEADING ME TO BELIEVE THAT A DUAL HEADED LOW IS THE MOST
LIKELY SCENARIO.

.SHORT TERM FORECAST...
THE FORECAST IMPACTS OF THE DUAL HEADED LOW EARLY NEXT WEEK WILL BE
INCREASED CLOUD COVERAGE OVER SOUTHCENTRAL. THE NORTHERN LOW WILL BE
CLOSE ENOUGH TO THE COAST TO ALLOW FOR MOISTURE TO SPILL
ONSHORE...ENDING THE NEARLY THREE WEEK STRETCH OF CLOUDLESS SKIES. BY
WEDNESDAY NIGHT...THE LARGE HIGH OVER THE BERING SEA AND NORTHERN
HALF OF THE STATE WILL OPEN UP INTO A RIDGE AND SHIFT OVER TO THE
EAST ONCE AGAIN CLEARING OUT SOUTHCENTRAL. BUT THIS COMES IN RESPONSE
TO A LARGE AREA OF LOW PRESSURE AND ASSOCIATED FRONTAL BOUNDARY THAT
WILL MARK THE END OF THIS DRY PATTERN.

.SOUTHWEST...HIGH AND DRY ACROSS THE SOUTHWEST CONTINUES. ONLY A FEW
MID AND UPPER LEVEL CLOUDS WILL STREAM OVER THE REGION UNTIL THE
STRONG FRONTAL BOUNDARY INVADES THURSDAY NIGHT INTO FRIDAY MORNING.

.BERING SEA/ALEUTIANS...THE STRATUS DECK IS BECOMING MORE WIDESPREAD
TODAY UNDER THE LARGE AREA OF HIGH PRESSURE. A WEAK SURFACE LOW WILL
DEVELOP NEAR THE ALASKA PENINSULA MONDAY AS THE DIFFUSE TROUGH SLOWLY
CREEPS NORTH TOWARD THE BLOCKING HIGH. LIGHT SHOWERS WILL PERSIST
AROUND THIS FEATURE. WEDNESDAY EVENING...A WARM FRONT CROSSES THE
WESTERN ALEUTIANS AND QUICKLY BECOMES OCCLUDED AS IT MOVES NORTH AND
EAST ACROSS THE BERING. THE ASSOCIATED LOW IS CURRENTLY FORECAST TO
REACH THE 940S AS IT BARRELS INTO THE WESTERN ALEUTIANS THURSDAY.
THIS IS THE DRIVING FORCE BEHIND THE PATTERN CHANGE THIS NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 127.
FIRE WEATHER...NONE.

AB MAR 11