Small Craft Advisory 676, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKDT SUN SEP 7 2008

.MODEL DISCUSSION...
THE MODELS ARE IN GOOD AGREEMENT THROUGH 72 HOURS OVER MAINLAND
ALASKA AND THE GULF OF ALASKA. A LOW PRESSURE SYSTEM MOVING OUT OF
EASTERN SIBERIA AND MERGING WITH A NPAC LOW IN THE WESTERN BERING SEA
MID WEEK IS THE CAUSE OF MUCH DISAGREEMENT. THE PREVIOUS SHIFT LEANED
HEAVILY TOWARD THE 00Z GFS AND BASED ON HPC GUIDANCE...FEEL THE BEST
COURSE OF ACTION IS TO LEAVE THE MID TO EXTENDED FORECASTS ALONE OUT
WEST UNTIL MODELS GET A BETTER HANDLE ON THIS LOW. IN THE SHORT
TERM...THE GFS HAS BEEN VERY CONSISTENT SO WE LARGELY BASED THIS
AFTERNOONS PACKAGE OFF OF THE LATEST RUN WHICH IS NOT ALL TOO
DIFFERENT FROM THE 00Z.

.ANALYSIS AND UPPER LEVELS...
VERTICALLY STACKED LOW CURRENTLY DISSIPATING NEAR THE ALASKA
PENINSULA. MULTIPLE SHORTWAVES EMBEDDED IN THE CYCLONIC CIRCULATION
EVIDENT ON THE WAVER VAPOR IMAGERY. AT THE SURFACE...THE REMNANTS OF
THE LOW PRESSURE SYSTEM IS OVER BRISTOL BAY AT 999 MB. THE OCCLUDED
FRONT ASSOCIATED WITH THIS LOW MOVED INLAND THIS MORNING AND IS NO
LONGER DISCERNABLE ACROSS THE FORECAST DOMAIN.

.SHORT TERM FORECAST...
SOUTH CENTRAL...WIDESPREAD SHOWER ACTIVITY PERSISTS ALONG THE NORTH
GULF COAST. SCATTERED SHOWERS ALREADY DEVELOPING EARLY THIS AFTERNOON
ON THE LEE SIDE OF THE MOUNTAIN RANGES. THIS ACTIVITY WILL INCREASE
OVERNIGHT AS ANOTHER SHORTWAVE PASSES THROUGH SOUTHCENTRAL TONIGHT
SWITCHING THE MEAN FLOW FROM SOUTHEAST TO SOUTHWEST.

A SHORT BREAK FOR SOUTHCENTRAL MONDAY BEFORE THE NEXT LOW MOVES OUT
OF THE NORTH PACIFIC AND FOLLOWS A SIMILAR TRACK TO THE ALASKA
PENINSULA MONDAY EVENING. SURFACE FLOW WILL TURN SOUTHEASTERLY IN
ADVANCE OF THIS SYSTEM. WHAT WILL BE DIFFERENT ABOUT THIS SYSTEM FROM
THE PREVIOUS IS THE LONG FETCH OF MOIST SOUTHWESTERLY FLOW ALOFT. THE
500 MB WINDS WILL REMAIN SOUTHWESTERLY THROUGH MID WEEK WHICH COULD
ALLOW FOR A MUCH MORE STEADY RAIN FROM THE WESTERN KENAI TO MATANUSKA
AND SUSITNA VALLEYS FROM MONDAY NIGHT THROUGH WEDNESDAY.

WEST OF THE ALASKA RANGE...
THE MEAN UPPER LEVEL PATTERN WITH A TROUGH AXIS OVER THE WESTERN
MAINLAND WILL BE VERY SLOW TO CHANGE. THIS PATTERN IS BRINGING DAILY
SHOWERS TO MOST AREAS. WHEN FLOW SHIFTS TO ONSHORE...FOG BECOMES A
PROBLEM ALONG THE COAST. THE UPPER LOW WILL NOT SHIFT FOR A WHILE SO
EXPECT TO SEE MUCH MORE OF THE SAME ACROSS SOUTHWEST MAINLAND ALASKA.

THE GFS IS HINTING AT A COOL SYSTEM DROPPING SOUTH LATE IN THE WEEK
THAT MAY HELP BRING SOME FAIR WEATHER.

BERING SEA AND ALEUTIANS...LOW PRESSURE SYSTEMS ARE SWINGING UP OUT
OF THE NORTH PACIFIC AND WEAKENING OVER THE ALASKA PENINSULA AND THEN
EVENTUALLY DISSIPATING IN THE EASTERN BERING SEA. HIGH PRESSURE
REMAINS IN CONTROL OF THE WESTERN BERING SEA FOR ANOTHER COUPLE OF
DAYS BEFORE THE POSSIBLE SHIFT IN THE PATTERN LATE IN THE WEEK.
WIDEPSPREAD FOG AND SHOWERS WILL CONTINUE UNTIL THIS POTENTIAL
PATTERN CHANGE.

...FLOOD ADVISORY WAS ALLOWED TO EXPIRE THIS MORNING. NUMEROUS
SHOWERS STILL DEVELOPING OVER THE ADVISED AREA ALTHOUGH RIVER GAUGES
REPORTING LEVELS WELL BELOW ACTION CRITERIA. WITH CONTINUOUS SHOWERS
EXPECTED OVER THE NEXT SEVERAL DAYS AND A ALREADY SATURATED
GROUND...BELIEVE WE MAY HAVE TO ISSUE MORE PRODUCTS FOR THE EASTERN
KENAI PENINSULA.

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

AB SEP 08