Small Craft Advisory 718, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
415 AM AKDT THU SEP 18 2008

.ANALYSIS AND UPPER LEVELS...
A STRONG 983 MB LOW OVER THE WEST END OF KODIAK ISLAND EARLY THIS
MORNING IS THE BIG WEATHER PLAYER TODAY. A STRONG FRONT NEARING THE
NORTH GULF COAST IS BRINGING SOME VERY STRONG WINDS. THE STRONGEST
WINDS ARE OVER PORTAGE VALLEY...TURNAGAIN ARM...AND THE HIGHER
ELEVATIONS OF ANCHORAGE WHERE A HIGH WIND WARNING IS IN EFFECT
THROUGH AFTERNOON. HEAVY RAIN SURROUNDS THE LOW...BUT WITH A STRONG
DOWNSLOPE HOLE OF LITTLE OR NO PRECIPITATION IN THE COOK INLET
REGION TO THE LEE OF THE CHUGACH AND KENAI MOUNTAINS. HIGH PRESSURE
EXISTS THIS MORNING OVER THE WESTERN BERING/ALEUTIANS.

.MODEL DISCUSSION...
MODELS GENERALLY AGREE ON STALLING THE KODIAK LOW OVER KAMISHAK BAY
LATER TODAY AND INTO TONIGHT...WITH THE LOW SHEARING APART AND
ANOTHER LOW FORMING IN THE KUSKOKWIM VALLEY. SOME MODEL DISAGREEMENT
AND RUN TO RUN INCONSISTENCY ON WHAT HAPPENS NEXT. WE ARE KEEPING
CLOSE TO THE PREVIOUS FORECAST AND TAKING A MUCH WEAKER VERSION OF
THE LOW EAST ACROSS THE FAR NORTHERN GULF FROM KAMISHAK BAY TONIGHT
TO AROUND MONTAGUE ISLAND FRIDAY NIGHT. 0Z NAM IS A DEFINITE OUTLIER
IN KEEPING THE LOW FURTHER WEST. FROM THE WEEKEND AND BEYOND...MADE
ONLY SMALL CHANGES TO THE PREVIOUS FORECAST WHICH REFLECTS MOST
CLOSELY THE ECMWF.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
LOW PRESSURE OVER THE WEST END OF KODIAK ISLAND WILL MOVE INTO
KAMISHAK BAY THIS AFTERNOON AND STALL OUT AND BEGIN TO WEAKEN. HIGH
WINDS WARNINGS ARE OUT FOR TURNAGAIN ARM...PORTAGE VALLEY...AND
HIGHER ELEVATIONS OF ANCHORAGE BUT THIS WILL NOT BE THE ONLY AREAS
AFFECTED BY SIGNIFICANT WINDS. THE STRONGEST WINDS WITH THE LOW ARE
JUST AHEAD OF A FRONT APPROACHING THE SOUTHCENTRAL COAST EARLY THIS
MORNING. WHEN THIS FRONT MOVES INLAND THIS AFTERNOON...WINDS WILL
DECREASE SOMEWHAT OVER MOST BUT NOT ALL AREAS. RAIN WILL REMAIN
QUITE HEAVY TODAY ESPECIALLY OVER THE EASTERN KENAI...AND WE WILL
HAVE TO KEEP AN EYE ON RIVER LEVELS THERE. MOST AREAS FROM KENAI TO
ANCHORAGE TO PALMER TO TALKEETNA...AND IN THE COPPER RIVER
BASIN...WILL REMAIN DOWNSLOPED AND SEE LITTLE RAIN FROM THIS SYSTEM.
THE LOW WILL MIGRATE FROM KAMISHAK BAY TONIGHT TO AROUND MONTAGUE
ISLAND FRIDAY NIGHT...THOUGH WINDS WILL NOT BE NEARLY AS STRONG AND
RAINS NOT AS HEAVY AS THEY WILL HAVE BEEN TODAY. RATHER GLOOMY
WEATHER HOWEVER WILL PERSIST OVER MOST OF SOUTHCENTRAL INTO
SATURDAY.

SOUTHWEST MAINLAND...
RAIN HAS EASILY SPILLED OVER THE ALEUTIAN RANGE AND INTO BRISTOL BAY
FROM THE KODIAK LOW...ALONG WITH SOME GUSTY NORTHERLY WINDS.
TODAY...THE RAIN WILL SPREAD NORTH INTO MOST OF THE KUSKOKWIM VALLEY
WHILE A SURFACE LOW PRESSURE DEVELOPS NEAR SLEETMUTE ALONG A TROUGH
AXIS. AS THIS LOW MOVES NORTHEAST AND OUT OF THE AREA ON
FRIDAY...COOL AND SHOWERY WESTERLY FLOW WILL SET IN OVER THE
SOUTHWEST MAINLAND FRIDAY INTO THE WEEKEND. THE AIRMASS MAY BE COOL
ENOUGH FOR SOME SNOW TO MIX IN FOR THE KUSKOKWIM DELTA AREA.

BERING SEA/ALEUTIANS...
FAIRLY STRONG NORTHWEST FLOW OVER THE EASTERN BERING AND HIGH
PRESSURE OVER THE WESTERN BERING WILL GRADUALLY GIVE WAY TO FLAT
ZONAL FLOW OVER THE NEXT FEW DAYS.

.LONG TERM FORECAST...
MODELS ARE IN POOR AGREEMENT IN THE LONG TERM ESPECIALLY OUT IN THE
BERING. HOWEVER...THEY HAVE BEEN INDICATING A PATTERN CHANGE EARLY
NEXT WEEK FOR THE MAINLAND...WITH HIGH PRESSURE AND DRY OFFSHORE
FLOW DEVELOPING MONDAY THROUGH WEDNESDAY PARTICULARLY OVER
SOUTHCENTRAL. WILL BE ANXIOUS TO SEE IF THIS PANS OUT...BUT IF IT
DOES IT WILL MEAN A COUPLE OF TRANQUIL DAYS AND POSSIBLY THE FIRST
FREEZE OF THE SEASON FOR MANY AREAS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING ZONES 101 AND 125.
MARINE...GALE WARNING ZONES 120 125 129 130 132 140 351 352.
FIRE WEATHER...NONE.

FOISY SEP 08