Small Craft Advisory 995, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AST TUE NOV 27 2007

.ANALYSIS AND UPPER LEVELS...
TRANSIENT UPPER LEVEL RIDGE OVER SOUTHCENTRAL EARLY THIS MORNING
GIVING THE AREA A BRIEF BREAK. NEGATIVELY TILTED TROUGH OVER THE
CENTRAL AND EASTERN ALEUTIANS WITH A VERTICALLY STACKED 971 MB LOW
NEAR DUTCH HARBOR. A 980 MB TRIPLE POINT LOW IS RAPIDLY PUSHING NORTH
TOWARD THE AKPEN. THE PRESSURE GRADIENT BETWEEN THE LOWS OUT WEST AND
THE 1016 MB HIGH PRESSURE OVER THE COPPER RIVER BASIN IS STRONGEST
WEST OF KODIAK ISLAND JUST AHEAD OF THE FRONT RESULTING IN STORM
FORCE WINDS OVER THE COASTAL WATERS OF THE ALASKA PENINSULA.

.MODEL DISCUSSION...
ALL MODELS IN GOOD AGREEMENT THROUGH 48 HOURS...THEN DIVERGE ON
SOLUTIONS REGARDING PLACEMENT OF LARGE LOW OVER THE WESTERN
ALEUTIANS. GFS ENSEMBLE SHOWING LARGE VARIATIONS BETWEEN MEMBERS AND
RUN TO RUN CONSISTENCY IS NOT EXCELLENT. THIS FORECAST PACKAGE IS
BASED ON THE 00Z GFS. AGAIN...CONFIDENCE IS NOT HIGH OUT WEST
REGARDING THE EXACT LOCATION AND STRENGTH OF THE LOW IN THE WESTERN
BERING SEA LATER IN THE WEEK.

.SHORT TERM FORECAST...
SOUTHCENTRAL AND THE GULF...
TRANQUIL WEATHER EXPECTED OVER SOUTHCENTRAL TODAY BETWEEN SYSTEMS.
MOSTLY CLEAR SKIES ALLOWING RADIATIONAL COOLING AND THE CHILLIEST
START TO A DAY SINCE THE 20TH. NOTICING TEMPERATURES ON THE MESONET
DEPICTING A VERY STRONG INVERSION WITH HIGHER ELEVATIONS REPORTING
TEMPS IN THE MID TO UPPER 30S WHILE THE VALLEYS ARE IN THE TEENS TO
LOWER 20S.

THE NEXT SYSTEM IS RAPIDLY APPROACHING WITH RAIN ALREADY REPORTED
ACROSS KODIAK ISLAND. HIGH LEVEL CLOUDS WILL INCREASE LATE THIS
AFTERNOON OVER ANCHORAGE WITH RAIN AND SNOW RETURNING TO PRINCE
WILLIAM SOUND AND THE EASTERN KENAI PENINSULA BY THIS EVENING. GAP
WINDS WILL ALSO INCREASE ALTHOUGH THE FRONTAL BOUNDARY WILL BE
WEAKENING AS IT BECOMES FURTHER REMOVED FROM UPPER LEVEL SUPPORT.
ONLY EXPECTING A FEW FLURRIES AND SPRINKLES IN ANCHORAGE AND THE
MATSU VALLEY TONIGHT AS THE SYSTEM DIES A QUICK DEATH IN THE NORTHERN
GULF. ONE MORE RAPIDLY DISSIPATING FRONT WILL MOVE OVER SOUTHCENTRAL
WEDNESDAY BEFORE A HIGH AMPLITUDE UPPER RIDGE BUILDS OVER THE AREA.
ALTHOUGH THE TEMPERATURES ALOFT ARE RELATIVELY WARM FOR THIS TIME OF
YEAR...THINKING THE COLD DENSE AIR WILL BUILD AT THE SURFACE
RESULTING IN TEMPERATURES CLOSER TO AVERAGE FOR THIS TIME OF YEAR
ACCOMPANIED BY MOSTLY CLEAR SKIES.

SOME UNCERTAINTY IN THE EVOLUTION OF THIS RIDGE LATER IN THE WEEK AS
A VERY STRONG SYSTEM AFFECTS KODIAK AND THE ALASKA PENINSULA. A
SLIGHTLY WEAKER RIDGE WOULD ALLOW THE SYSTEM TO MOVE FAR ENOUGH EAST
TO SPREAD SOME CLOUDS AND WARMER AIR BACK INTO ANCHORAGE. BEST GUESS
AT THIS TIME IS THE RIDGE WILL HOLD THE SYSTEM TO OUR WEST AND ALSO
ALLOW SOME VERY COLD AIR TO BUILD IN WESTERN CANADA. EXTENDED MODELS
HAVE THIS EXTREME COLD SPILLING INTO OUR DOMAIN LATE THIS WEEKEND AND
THROUGH EARLY NEXT WEEK.

SOUTHWEST MAINLAND...
STRONG SYSTEM TODAY AFFECTING SOUTHWEST ALASKA INCLUDING BRISTOL BAY.
WINDS ALONG THE WESTERN CAPES HAVE INCREASED EARLY THIS MORNING AND
WILL CONTINUE THROUGH LATE THIS EVENING. MOST OF THE PRECIPITATION
WILL FALL ALONG THE COASTAL AREAS. THE INTERIOR WILL BE DOWNSLOPED
AND REMAIN RELATIVELY DRY. 12Z SOUNDING AT MCGRATH INDICATIVE OF A
FREEZING DRIZZLE SCENARIO WITH ENTIRE SOUNDING BELOW FREEZING AND DRY
AIR ABOVE A VERY MOIST COLUMN NEAR THE SURFACE...RESULTING IN
SUPERCOOLED DROPS. NOT EXPECTING THESE CONDITIONS TO LAST LONG AS
MOISTURE IS ON THE INCREASE AT THE MID AND UPPER LEVELS.

CONCERN FOR LATER THIS WEEK WITH A VERY STRONG SYSTEM SHAPING UP
THURSDAY THROUGH EARLY IN THE WEEKEND WHICH WILL OBTAIN ITS ENERGY
FROM THE REMNANTS OF TYPHOON MITAG. THIS IS STILL FAR OUT IN THE
FORECAST BUT WOULD NOT BE SURPRISED IF A HIGH WIND WATCH WILL BE
NECESSARY FOR THE ALASKA PENINSULA LATER THIS WEEK.

BERING/ALEUTIANS...
A VERTICALLY STACKED LOW IN THE WESTERN BERING WILL SERVE AS THE
ANCHOR FOR SYSTEMS TO DEVELOP SOUTH OF THE ALEUTIANS AND MOVE
NORTHWARD INTO THE CENTRAL AND EASTERN BERING. GALE AND STORM FORCE
WINDS WILL REMAIN PEPPERED THROUGHOUT THE COASTAL WATERS AS
CONDITIONS RAPIDLY CHANGE DURING THE WEEK. STRENGTH AND EXACT
LOCATION OF THE LOW AND ASSOCIATED FRONTAL BOUNDARIES REMAINS THE
BIGGEST FORECAST CHALLENGE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING 150 175 176.
       GALE WARNING 130 132 138 155 160 165 170 171 172 176 180 185.
FIRE WEATHER...NONE.

AB NOV 07