Small Craft Advisory 891, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM AKST TUE NOV 3 2009

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL TROUGH EXTENDS FROM EASTERN RUSSIA...ACROSS THE BERING
AND AKPEN TO JUST SOUTH OF THE GULF THIS MORNING. AN UPPER RIDGE IS
OVER THE CENTRAL ALEUTIANS AND SOUTHEAST AK. AT THE SURFACE...AN
ELONGATED LOW EXTENDS FROM KAMCHATKA TO COLD BAY AND INTO THE
NORTHERN PACIFIC SOUTH OF THE GULF...WITH CENTERS SOUTH OF THE GULF
AND IN THE EASTERN BERING. A DEVELOPING LOW IS SOUTHWEST OF SHEMYA. A
WEATHER FRONT IS MOVING INTO SOUTHWESTERN AK AND SLOWLY
DISSIPATING...WHILE A HIGH REMAINS OVER THE NORTHERN ALCAN.

.MODEL DISCUSSION...

MODELS ARE IN GENERAL AGREEMENT IN HANDLING THE MOVEMENT OF SPECIFIC
LOW CENTERS EMBEDDED WITHIN THE ELONGATED LOW. THE LOW SOUTH OF THE
GULF WILL MOVE INTO THE NORTHWESTERN GULF. THE LOW SOUTHWEST OF
KAMCHATKA WILL INTENSIFY AND RACE EAST...MERGING FIRST WITH THE
EASTERN BERING LOW AND THEN WITH THE GULF LOW. THE RESULT WILL BE A
DEEP LOW THAT SLOWLY WEAKENS OVER THE NORTHERN GULF. THE FORECAST
LEANS HEAVILY ON THE NAM SOLUTION INITIALLY TO CAPTURE DETAILS...AND
THEN BLENDS TOWARD THE GFS. THE EXTENDED SOLUTION IS A BLEND OF THE
GFS AND HPC GUIDANCE.

.SHORT TERM FORECAST...

IN THE WEST...DRY CONDITIONS OVER THE WESTERN ALEUTIANS WILL GIVE WAY
TO RAIN AND SNOW SHOWERS AS THE LOW SOUTHWEST OF SHEMYA RACES EAST
TODAY AND TONIGHT. STRONG NORTHWEST FLOW WILL KEEP SNOW
SHOWERS...GALES...AND SOME STORMS ACROSS THE AREA THROUGH WED NIGHT.
THESE WILL BE CUT OFF BY BRIEF RIDGING THU AND THEN AN APPROACHING
LOW AND FRONT WILL BRING ANOTHER ROUND OF RAIN AND SNOW FRI.

FOR SOUTHWEST AK...THE DECAYING WEATHER FRONT WILL BRING SNOW ONSHORE
TODAY WITH SOME FREEZING RAIN INTO THE BRISTOL BAY ZONE. THIS WILL
CHANGE TO RAIN LATER IN THE DAY...WHILE SNOW SHOWERS SHOULD CONTINUE
OVER 155 AND 152. PRECIPITATION WILL CHANGE TO RAIN WED AND FINALLY
DISSIPATE LATER THU AS ALL OF THE LOWS CONSOLIDATE OVER THE GULF AND
COLD DRY AIR MOVES INTO THE AREA.

SOUTH AND EAST OF THE AK AND ALEUTIAN RANGES...RAIN AND SNOW SHOWER
ACTIVITY WILL BE LIMITED TO COASTAL AREAS TODAY ON ONSHORE FLOW WHILE
COLDER AIR REMAINS ENTRENCHED INLAND. AS THE LOW OVER THE EASTERN
BERING MOVES TO BRISTOL BAY IT WILL CAUSES WINDS TO INCREASE ALONG
TURNAGAIN ARM AND PORTAGE VALLEY LATE TONIGHT INTO WEDNESDAY. PRECIP
WILL SLOWLY MOVE INLAND OVER MOUNTAIN RANGES ON WED...GRADUALLY
CHANGING OVER TO RAIN ON THU. AS THE LOW CONSOLIDATES IN THE NORTHERN
GULF FRI IT WILL BRING COLDER AIR AND SNOW SHOWERS BACK INTO THE
AREA.

.LONG TERM FORECAST...

IN THE WEST...A DRYING RIDGE MOVES ACROSS THE BERING SAT AND WILL BE
FOLLOWED BY A KAMCHATKA FRONT SPREADING RAIN ON SUN. SHOWERS WILL
AFFECT SOUTHWEST AK ON SAT WITH DRYING ON SUN. SOUTHEAST OF THE AK
RANGE WILL EXPERIENCE DIMINISHING SHOWERS OVER THE WEEKEND BENEATH
WEAK HIGH PRESSURE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH 101 125
MARINE...STORM 120 130 170
        GALE 125 129 132 138 140 141 155 165 171 172 175 176 179 180
FIRE WEATHER...NONE

DS NOV 09