Small Craft Advisory 242, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM ADT SUN MAR 11 2007

.DISCUSSION...

UPPER AIR...STABLE UPPER PATTERN WITH BLOCKING RIDGE OVER THE BERING
SEA AND A CLOSED LOW CENTERED ALONG THE NORTH GULF COAST. MODEL
EVOLUTION OF THIS PATTERN THE NEXT WEEK HAS BEEN VERY CONSISTENT.
CURRENT UPPER LOW WILL OPEN UP INTO TROUGH TONIGHT AND SHIFT EASTWARD
A BIT ALLOWING BERING RIDGE TO BUILD EASTWARD OVER THE EASTERN
BERING/AKPENN REGION. THIS WILL SHIFT AREA OF MAX COLD ADVECTION TO
INTERIOR SOUTHWEST ALASKA/THE WESTERN GULF/ AND WESTERN PORTION OF
SOUTHCENTRAL. ANOTHER DEEP CLOSED LOW WILL DROP DOWN ACROSS THE
STATE MONDAY NIGHT AND TUESDAY BRINGING ANOTHER SURGE OF COLD AIR.
PATTERN LOOKS LIKE IT WILL RETROGRADE AS WE HEAD TO NEXT WEEKEND.
THIS WILL LIKELY BRING MORE CLOUDS OVER THE SOUTHERN MAINLAND WITH
A CHANCE OF PRECIP AND ALLOW WEST PACIFIC SYSTEMS TO BEGIN
PENETRATING THE ALEUTIANS/SOUTHERN BERING. THIS POTENTIALLY COULD
BE THE START OF A MUCH MORE SIGNIFICANT PATTERN CHANGE AS WE HEAD
LOOK BEYOND 7 DAYS.

IN THE GULF THERE ARE AGAIN MULTIPLE LOWS EMBEDDED WITHIN THE LARGER
CYCLONIC CIRCULATION. TWO LOWS MOVING NORTHEASTWARD FROM THE CENTRAL
TO EASTERN GULF WILL HAVE NO IMPACT ON ANCHORAGE AOR. THE MAIN LOW
OF CONCERN IS CENTERED JUST EAST OF CORDOVA TRACKING WESTWARD AND
SPREADING SNOW/SNOW SHOWERS ACROSS THE COPPER RIVER BASIN INTO
EASTERN PRINCE WILLIAM SOUND. UPPER SHORTWAVES  DROPPING INTO THE
BACK SIDE OF THE TROUGH WILL STOP THIS SURFACE LOW FROM TRACKING MUCH
FURTHER WEST. SO A FEW SHOWERS WILL MAKE IT TO WESTERN PRINCE WILLIAM
SOUND LATE TONIGHT BUT NOT ANY FARTHER WEST THAN THAT. MEANWHILE COLD
AIR ADVECTION WILL CONTINUE ACROSS SOUTHWEST ALASKA INTO THE WESTERN
GULF AND WESTERN SUSITNA VALLEY RESULTING IN GUSTY WINDS...MAINLY
THROUGH CHANNELED AREAS. WIND CHILL READINGS WILL ONCE AGAIN APPROACH
-40 DEGREES ALONG THE ALASKA RANGE IN THE SUSITNA VALLEY SO AN
ADVISORY WILL BE CONSIDERED. COLD ADVECTION ASSOCIATED WITH NEXT
UPPER LOW DROPPING DOWN WILL BRING COLDER TEMPS TO THE SOUTHERN
MAINLAND BEGINNING MONDAY NIGHT AND CONTINUEING THROUGH TEH END OF
THE WEEK. WITH UPPER CENTER FORECAST TO BE OVERHEAD OF SOUTHCENTRAL
BEST SUPPORT FOR STRONG SURFACE WINDS WILL BE FROM THE SUSITNA VALLEY
SOUTHWARD ALONG THE ALASKA AND ALEUTIAN RANGES AND THE WESTERN GULF.
ALTHOUGH COLD ADVECTION OCCURS OVER SOUTHWEST ALASKA SURFACE GRADIENT
LOOKS TO BE QUITE WEAK...SO DO NOT EXPECT STRONG WINDS.

OVER THE EASTERN BERING SATELLITE IMAGERY SHOWS CLEARING ALONG MOST
OF THE ICE EDGE AND DIMINISHING SNOW SHOWERS/STRATO CU AS COLD
ADVECTION CUTS OFF FROM WEST TO EAST. SNOW SHOWERS AND BLOWING SNOW
WILL CONTINUE THROUGH THIS EVENING FROM THE EASTERN ALEUTIANS TO
AKPENN AND THEN GRADUALLY CUT OFF LATER TONIGHT AND MONDAY FROM
WEST TO EAST AS HIGH PRESSURE BUILDS EASTWARD. THIS SHOULD SLOW DOWN
THE SOUTHWARD PROGRESSION OF THE SEA ICE EDGE. HOWEVER...AS THE HIGH
RETROGRADES WESTWARD MID TO LATE WEEK COLD ADVECTION WILL BEGIN
AGAIN...ESPECIALLY ALONG THE SOUTHWEST COAST AND AKPENN SO ICE EDGE
WILL LIKELY PROGRESS FARTHER SOUTH AND WEST. THE FAR WESTERN
ALEUTIANS REMAIN JUST WEST OF THE HIGH AND ARE FEELING SOME EFFECTS
FROM THE SYSTEMS TO THE WEST. THIS LOOKS TO CONTINUE THROUGH MID
WEEK.

MODELS...NAM HAS VERIFIED EXTREMELY WELL WITH LOW POSITIONS IN THE
GULF AND CONTINUES TO BE THE PREFERRED MODEL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 121 129 130 150 155 176.
         HEAVY FREEZING SPRAY 121 129 130 132 138 141 150 155 165
                              170 171 179.
FIRE WEATHER...NONE.

SEB MAR 07