Small Craft Advisory 165, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AST THU FEB 15 2007

.DISCUSSION...

ANALYSIS...WEAK FLOW CONTINUES ALOFT WITH A RIDGE EXTENDING FROM
THE ARCTIC NORTH OF RUSSIA TO MAINLAND ALASKA AND THREE UPPER
LOWS...A WEAK ONE SOUTH OF THE AKPENN...ANOTHER WEAK ONE OVER
SOUTHWEST ALASKA...AND A DEEPER LOW OVER THE WESTERN BERING SEA.
THE SURFACE WEATHER ASSOCIATED WITH THESE LOWS IS QUITE TAME WITH
SOME LIGHT SHOWERS/PRECIP AND GENERALLY LIGHT WINDS. THESE LOWS
ARE SITTING NEARLY STATIONARY WAITING FOR SOME FEATURE STRONG
ENOUGH TO CREATE SOME MOVEMENT. A DEEPENING SURFACE LOW NEAR
43N 165E (AS OF 20Z) WILL BE THE KICKER. THIS SYSTEM HAS CAUSED
UPPER JET TO BUCKLE AND THE JET IS NOW STEERING THE LOW TOWARD
THE WESTERN ALEUTIANS/BERING SEA. WHEN THIS REACHES THE BERING
SEA THE UPPER JET WILL SET UP FARTHER NORTH AND THE PATTERN WILL
BECOME MUCH MORE ACTIVE THAN IT HAS BEEN THE LAST COUPLE WEEKS.
THE LAST FEATURE OF NOTE ON SATELLITE IMAGERY THIS MORNING IS A
DEVELOPING LOW NEAR 41N 159W. THIS LOW IS ALSO CAUSING THE UPPER
JET TO BUCKLE AND THIS WILL FORCE THE LOW NORTHEASTWARD TOWARD
SOUTHEAST ALASKA. THE NOTICEABLE EFFECTS OF THIS LOW IN THE
ANCHORAGE AOR WILL BE LIMITED TO THE GULF OFFSHORE.

MODELS...THE MODELS SHOW FAIR RUN-TO-RUN CONTINUITY WITH THE
DEVELOPING LOW OUT WEST. THE DETAILS OF THE SYSTEM CONTINUE TO
FLUCTUATE BUT THE BASIC OUTLOOK (AND RESULTING FORECAST) LOOK
SIMILAR. THE GFS CONTINUES TO BE THE DEEPEST WITH THIS LOW
BOTTOMING OUT AT 964 MB. HOWEVER...THE UKMET HAS TRENDED DEEPER
AND NOW SHOWS A MINIMUM PRESSURE OF 965 MB. ALSO...THE GFS
ENSEMBLE MEAN IS ONLY A COUPLE MILLIBARS WEAKER THAN THE OPERATIONAL
RUN. THEREFORE...NOW HAVE HIGHER CONFIDENCE IN THE GFS
SOLUTION...WHICH IS THE SOLUTION THAT HAS BEEN FAVORED THE PAST
COUPLE DAYS AND CONTINUES TO BE THE MODEL OF CHOICE. YESTERDAY
AFTERNOONS MODEL RUNS DEPICTED A SHORT-WAVE ROUNDING THE BOTTOM
OF THE UPPER TROUGH AND FORMING ANOTHER SURFACE LOW FRIDAY NIGHT
AND SATURDAY...BUT THE LATEST RUNS HAVE BACKED OFF A TAD ON THIS.
WITH LOTS OF ARCTIC AIR FEEDING INTO THE SYSTEM THINK THERE WILL
AT LEAST BE WEAK LOW DEVELOPMENT WITH THIS SHORT-WAVE.
HOWEVER...IMPACT ON THE OVERALL FORECAST WILL BE MINIMAL. THE
MODEL SOLUTIONS DIVERGE SIGNIFICANTLY WITH THE LOW HEADING TOWARD
SOUTHEAST ALASKA. HAVE COORDINATED WITH JUNEAU WFO AND WILL LEAN
TOWARD A SLIGHTLY FASTER GFS SOLUTION FOR THE FIRST 42 HOURS OR SO.
THIS WILL BRING GALE FORCE WINDS TO THE SOUTHEASTERN PORTION OF
THE WESTERN GULF OFFSHORE.

BERING SEA/ALEUTIANS/AKPENN FORECAST...NO MAJOR CHANGES FROM
CURRENT FORECASTS. EXPECT DEVELOPING LWO TO BEGIN IMPACTING THE
WESTERN ALEUTIANS LATE TONIGHT INTO FRIDAY MORNING AND SPREAD
EASTWARD TO THE AKPENN BY SATURDAY. AS HS BEEN ADVERTISED...LOOK
FOR WIDESPREAD MAX GALES IN THE VICINITY OF THE LOW AND ALONG THE
FRONT AS IT PROGRESSES EASTWARD. SIGNIFICANT WARM AIR ADVECTION
AHEAD OF THE SYSTEM WILL RESULT IN MAINLY RAIN. HOWEVER...SIGNIFICANT
COLD ADVECTION ON THE BACK SIDE OF THE LOW WILL RESULT IN SNOW FOR
THE FAR WESTERN ALEUTIANS. SURFACE TEMPS LOOK LIKE THEY WILL BE
WARM ENOUGH THAT VISIBILITIES WILL REMAIN ABOVE BLIZZARD CRITERIA.
HOWEVER...AS HEAD INTO THE WEEKEND AND LOW MOVES A BIT FARTHER NORTH
COLD AIR WILL MOVE EASTWARD ACROSS THE ALEUTIANS AND THERE WILL BE
POTENTIAL FOR STORM FORCE WINDS AND BLIZZARD CONDITIONS. THIS WILL
NEED TO BE REEVALUATED AS WE GET CLOSER IN TIME.

SOUTHERN MAINLAND FORECAST...UPPER LOW AND ASSOCIATED UPPER TROUGH
AXIS OVER SOUTHWEST ALASKA WILL VERY SLOWLY DRIFT NORTHWARD INTO
THE INTERIOR TONIGHT THROUGH FRIDAY NIGHT. MEANWHILE...UPPER LOW
SOUTH OF AKPENN WILL DISSIPATE AND TROUGH AXIS WILL LIFT NORTHWARD
TOWARD SOUTHCENTRAL. THE END RESULT WILL BE A FEW FLURRIES INLAND
AND SHOWERS ALONG THE GULF COAST. BY SATURDAY SOUTHERN MAINLAND
SHOULD BE ALMOST COMPLETELY DRY. FRONT FROM WESTERN LOW WILL MOVE
ONSHORE SOUTHWEST ALASKA LATE SATURDAY AND TO SOUTHCENTRAL ON SUNDAY.
IT APPEARS THE FRONT WILL HAVE WEAKENED TO THE POINT THAT DOWNSLOPING
WINDS WILL NOT BE FACTOR. ALSO FLOW ALOFT WILL BE OUT OF THE
SOUTHWEST. SO ALL AREAS HAVE A SHOT AT A PRECIP.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 170 171 172 175 176 179 185.
         HEAVY FREEZING SPRAY 185.

SEB FEB 07