Small Craft Advisory 470, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT MON MAY 22 2006

.DISCUSSION...

ANALYSIS...SIGNIFICANT RIDGE EXTENDS FROM THE NORTH PACIFIC TO OVER
THE CENTRAL BERING.  A TROUGH IS CENTERED OVER THE KAMCHATKA
PENINSULA.  A CLOSED COLD CORE LOW CONTINUES TO DRIFT SOUTH OF THE
GULF OF ALASKA ALLEVIATING THE COASTAL RAIN AND CLOUDINESS OF
SOUTHCENTRAL ALASKA THE PAST COUPLE OF DAYS AS NORTHERLY FLOW SETS UP
ACROSS MUCH OF MAINLAND ALASKA.  A WEAK AREA OF LOW PRESSURE IS
LOCATED OVER EASTERN ALASKA BRINGING SCATTERED RAIN SHOWERS TO UPPER
YUKON VALLEY.  SATELLITE CONFIRMS THE PRESENCE OF A WIDE AREA OF
STRATUS AND FOG UNDER THE RIDGE OVER THE BERING.

MODEL ANALYSIS...MODELS INITIALIZED WELL AND SHOW GOOD CONSISTENCY
THROUGH THE SHORT TERM.  MODELS FINALLY IN AGREEMENT WITH BUILDING
THE RIDGE INTO THE INTERIOR BUT VARY WITH THE TIMING AND POSITION OF
THE SHORTWAVE MOVING OVER THE RIDGE WED/THU.

SHORT-TERM FORECAST...GENERAL TREND OF WARMER AND DRIER CONDITIONS
OVER THE SOUTHERN MAINLAND THROUGH MIDWEEK AS THE RIDGE SLOWLY BUILDS
IN FROM OVER THE BERING.  DOWNSLOPING NORTHERLY WINDS OFF THE ALASKA
RANGE AND TALKEETNA MOUNTAINS WILL CONTINUE TO USHER IN WARMER
TEMPERATURES FOR SOUTH CENTRAL ALASKA.  THESE SAME WINDS PRODUCED BY
THE NORTH-SOUTH PRESSURE GRADIENT BETWEEN THE RIDGE OVER THE INTERIOR
AND THE LOW SPINNING SOUTH OF THE GULF WILL BRING HOT AND DRY
CONDITIONS TO SOUTHCENTRAL ALASKA NECESSITATING THE CURRENT FIRE
WEATHER WATCH FOR ZONES 141 AND 145.  OUT WEST EXPECT FOG AND STRATUS
TO INCREASE UNDER THE RIDGE...CEILINGS HAVE BEEN MVFR OR LESS OVER
THE PRIBILOFS THE LAST 24 HOURS.  LOW CEILING LOOKS NOT TO MOVE
INLAND WITH SIGNIFICANT NORTHERLY FLOW OVER THE WESTERN COAST.  A
TIGHT PRESSURE GRADIENT OVER SOUTHWESTERN ALASKA TO INCLUDE THE
EASTERN ALEUTIANS AND THE AKPENN CAUSED BY A LOW IN THE GULF AND HIGH
PRESSURE OVER THE CENTRAL BERING WILL CONTINUE TO PRODUCE GUSTY NORTH
TO NORTHWEST WINDS.  GALE WARNINGS CONTINUE FOR THE MARINE ZONES IN
THIS AREA.  CONVECTION OVER WESTERN ALASKA SHOULD NOT BE AN ISSUE
THROUGH THE END OF THE WEEK WITH SUBSIDENCE OCCURRING UNDER THE
RIDGE.  HOWEVER HAVE NOT RULED OUT THE CHANCE OF CONVECTION OVER THE
MATSU VALLEY..ANCHORAGE BOWL..AND COPPER RIVER VALLEY ESPECIALLY
MIDWEEK WITH SHORTWAVE RIDING DOWN THE EASTERN SIDE OF THE RIDGE.
SURFACE INSTABILITY FROM LATE SPRING SUN ANGLE SHOULD BE AMPLE...BUT
DRYNESS REMAINS THE CONTENTIOUS VARIABLE.

EXTENDED FORECAST...WARMER AND DRY CONDITIONS GENERALLY THE RULE
THROUGH THE END OF THE WEEK FOR SOUTHCENTRAL ALASKA.  LATEST MODEL
RUNS HAVE THE POSITIVE-TILT TROUGH COMPLEX OVER THE GULF BEGINNING TO
LIFT NORTHEAST BY WEEKS END AS THE DOWNSTREAM RIDGE BREAKS DOWN OVER
THE INTERMOUNTAIN WEST.  THIS MAKES ROOM FOR A WEAK LOW TO ENTER THE
WESTERN GULF AND PULLS A LOW OVER THE KAMCHATKA PENINSULA INTO THE
WESTERN ALEUTIANS BY EARLY NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WARNING ZONE 155
MARINE...GALES 130 175 176
FIRE WEATHER...RED FLAG WARNING ZONE 111 141 AND 145 MON AFTN AND
EVE.

SDM/SB MAY 06