Small Craft Advisory 1016, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
348 PM AKST THU DEC 18 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE GULF OF ALASKA WITH A FRONT
STRETCHED EAST TO WEST ACROSS THE NORTHERN GULF. THERE IS ANOTHER
LOW SOUTH OF THE WESTERN ALEUTIANS WITH A LEADING FRONT OVER THE
CENTRAL ALEUTIANS. HIGH PRESSURE SITS OVER CENTRAL ALASKA.

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.MODEL DISCUSSION...
THE NUMERICAL MODELS CONTINUE TO STRUGGLE WITH THE LOCATIONS OF
VARIOUS SURFACE LOWS...ESPECIALLY BETWEEN FORECAST HOURS 24 AND 42
AS THE TWO MAIN UPPER LOWS MERGE. BY 84 HOURS (SUNDAY AFTERNOON)
THE MODELS ARE ACTUALLY IN DECENT AGREEMENT...BUT THAT IS MAINLY
DUE TO THE LARGER SCALE OF WEATHER FEATURES AT THAT TIME.

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.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 THROUGH 3)...
THE GENERAL PATTERN THROUGH SUNDAY CONSISTS OF A LOW (USUALLY A
COMPLEX LOW...THAT IS MULTIPLE CENTERS) IN THE GULF WITH WEAK HIGH
PRESSURE INLAND. THUS IT WILL BE MAINLY DRY INLAND WITH SURGES OF
PRECIPITATION IN THE COASTAL AREAS. THE FIRST OF THESE "SURGES"
WILL PUSH TO THE NORTH GULF COAST LATE TONIGHT INTO FRIDAY MORNING
WITH THE NEXT ONE DUE FRIDAY NIGHT. BY THE TIME THE THIRD ONE
PUSHES NORTH ON SUNDAY...THE TWO UPPER LOWS WILL BE MERGING. THIS
WILL SEND THE MAIN UPPER LEVEL GULF LOW NORTHWARD...WHICH WILL
COMBINE WITH AN EASTWARD MOVING TROUGH THAT IS OVER WESTERN ALASKA
ON SUNDAY.

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.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
GENERAL EASTERLY OR SOUTHEASTERLY FLOW WILL CONTINUE ACROSS THE
AREA THROUGH THE SHORT TERM (84 HR) FORECAST PERIOD. TWO WEAK
SHORTWAVES WILL MOVE THROUGH THE REGION...THE FIRST TONIGHT AND
THE SECOND ON SATURDAY OR SATURDAY NIGHT...BUT BOTH WILL BE WEAK
WITH ONLY A DUSTING OF SNOW (AT MOST) FOR MUCH OF THE AREA.
TEMPERATURES WILL REMAIN FAIRLY STEADY THROUGH THE START OF THE
WEEKEND BEFORE A MORE PRONOUNCED COOLING TREND SETS IN STARTING
SUNDAY.

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.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE VERY STRONG ZONAL JET COMING OUT OF EASTERN ASIA WILL KEEP A
SERIES OF FAIRLY WEAK DISTURBANCES MOVING EASTWARD ALONG OR JUST
SOUTH OF THE CHAIN OVER THE NEXT FEW DAYS. STARTING THIS
WEEKEND...WINDS WILL BECOME MORE PREVAILING OUT OF THE NORTH AS
SEASONABLY COOL AIR STARTS TO FILTER DOWN MORE SIGNIFICANTLY FROM
THE BERING STRAIT. AS COOL AIR INCREASINGLY SPREADS ACROSS THE
RELATIVELY WARM OCEAN WATERS THE ATMOSPHERE WILL CONTINUE TO
SLOWLY DESTABILIZE AND SHOULD RESULT IN AN INCREASE IN SHOWER
ACTIVITY ACROSS MUCH OF THE AREA BY THE END OF THE WEEKEND.

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.LONG TERM FORECAST (DAYS 4 THROUGH 7)...
A PATTERN CHANGE WILL OCCUR MONDAY AND TUESDAY. A LARGE UPPER LOW
WILL SET UP OVER THE WESTERN BERING SEA AND WESTERLY/SOUTHWESTERLY
FLOW ALOFT WILL DEVELOP ACROSS THE BERING/ALEUTIANS AND SOUTHERN
ALASKA. THE WPC USED A BLEND THAT CONSISTS OF 50 PERCENT 00Z ECMWF
AND ECMWF ENSEMBLE MEAN...WITH THE OTHER 50 PERCENT CONSISTING OF
THE 06Z GFS/PARALLEL GFS AND ENSEMBLE MEAN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...119 120 127 130-132 138 177 178
 		 HEAVY FREEZING SPRAY...180 181.
FIRE WEATHER...NONE.

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