Small Craft Advisory 58, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST THU JAN 20 2011

.MODEL DISCUSSION...00Z MODELS ALL DEPICT BASIC PATTERN REASONABLY
WELL...THE BROAD SWRLY FLOW UPPER FLOW FROM THE NPAC THAT EXTENDS
INTO THE GULF OF AK. WITH A WEAK UPPER RIDGE SEPARATING THAT FROM
THE CYCLONIC WRLY FLOW TO THE N OF THE AK RANGE IN A NRN BRANCH OF
THE JET. DIFFERENCES ARISE AS EARLY AS 30 HOURS OUT IN ALL OF THEM
THOUGH IN THE DETAILS OF SHORT WAVES ROTATING UP FROM THE BASE OF
LARGE DECAYING VERTICALLY STACKED LOW 500 NM SOUTH OF SHEMYA. FOR
THIS REASON...GFS WAS MAINLY USED...WITH A SMALL PORTION OF THE ECMWF
IN A BLEND FOR THE GRIDS.

.ANALYSIS AND UPPER LEVELS...THE BASIC PATTERN DESCRIBED ABOVE WILL
HOLD THROUGH SATURDAY. WEAK REMAINS OF ORIGINAL OCCLUSION FROM LARGE
NPAC LOW WILL DISSIPATE IN PLACE TODAY OVER SW MAINLAND...EAST ACROSS
S-CENTRAL AND COPPER RIVER BASIN. SHORT-WAVE S OF PACD AROUND 50N
WITH A 986 MB SURFACE LOW WILL MOVE NE OVER ERN ALEUTIANS AND AK PEN
TODAY. THEN OVER WRN GULF TONIGHT...AND NRN GULF FRI. ANOTHER WEAKER
ONE WILL FOLLOW THE SAME TRAJECTORY 12-18 HOURS LATER...ENDING UP
OVER FAR ERN GULF COAST SATURDAY AFTERNOON. A MUCH STRONGER LOW WITH
A WELL DEVELOPED OCCLUSION FORECAST BY ALL MODELS TO LIFT N OVER ERN
ALEUTIANS...AK PEN AND WRN GULF LATE SATURDAY THROUGH EARLY SUNDAY.

.SHORT TERM FORECAST...
SOUTH-CENTRAL/SOUTHWEST
WEAK REMAINS OF DISSIPATING OCCLUSION OVER-RUNNING ARCTIC AIR OVER
S-CENTRAL AND COPPER RIVER BASIN TODAY. GOOD FOR 1-3
INCHES...DIMINISHING IN AFTERNOON. RAIN MOVING NE FROM KODIAK
TONIGHT...BECOMING MIXED PRECIP. OVER GULF COAST/KENAI LATE TONIGHT
AND FRIDAY. NEXT WEAK SYSTEM WILL BRING RAIN TO KODIAK FRI
NIGHT...THEN MIXED PRECIP GULF COAST AND SNOW TO S-CENTRAL SATURDAY.
SNOW SHOWERS ENDING TODAY SW AS WEAK OCCLUSION REMAINS DISSIPATE.
MIXED PRECIP. MOVING N WITH NEXT SYSTEM LATER TODAY AND TONIGHT AK
PEN. AND ERN HALF OF 161. SOME -SN AHEAD OF FOLLOWING SYSTEM FRI INTO
SAT FOR SW INTERIOR...THOUGH ZONE 155 WILL BE ON THE EDGE.

BERING/ALEUTIANS
RAIN TODAY DIMINISHING TONIGHT ERN ALEUTIANS AS WEAK FRONT LIFTS N.
SCATTERED SHOWERS CENTRAL AND WRN ALEUTIANS THROUGH FRI...MIXED WITH
SNOW AT NIGHT. STRONG GALES AND MODERATE-HEAVY RAIN/SNOW CENTRAL AND
ERN ALEUTIANS SATURDAY AND SATURDAY NIGHT. SNOW SHOWERS DEVELOPING
SAT WRN ALEUTIANS AS COLDER AIR GETS PULLED DOWN DUE TO DEEP LOW
MOVING UP TOWARD ERN HALF. SCATTERED -RA/-SN SHOWERS TODAY
PRIBILOFS...INCREASING TONIGHT AND FRIDAY AS WEAK SHORT-WAVE LIFTS N.

.LONG TERM FORECAST...STRONG OCCLUSION FORECAST BY MODELS TO BE
RAPIDLY PUSHED N OVER GULF COAST AND S-CENTRAL SUN. SIGNICANT WARMER
AIR POSSIBLE WITH THIS COULD BRING -RA EVEN TO INLAND
S-CENTRAL...CERTAINLY A WARM CHINOOK EVENT AS ADVERTISED. COOLER AIR
BEHIND THE OCCLUSION AND WITH THE FOLLOWING SHORT-WAVE SHOULD CHANGE
PRECIP. BACK TO SNOW ALL AREAS IF THIS OCCURS. BROAD MILD S TO SW
FLOW WITH EMBEDDED LOWS/SHORT-WAVES FORECAST TO CONTINUE WELL AFTER
THIS BY BOTH ECMWF AND GFS...WHICH WOULD KEEP TEMPS. ABOVE AVERAGE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...
  GALES...351 352 411 412 132 185
FIRE WEATHER...NONE.

MAR JAN 11