Small Craft Advisory 139, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
527 AM AKDT SAT OCT 13 2012

.DISCUSSION...
ALOFT...LONG WAVE TROUGH BEGINNING A SHIFT WEST FROM EASTERN AK
TO THE CHUKCHI AND EASTERN BERING SEAS. A 494 DM LOW OVER THE HIGH
ARCTIC WILL DRIFT SOUTH TO 480 MILES NORTHWEST OF BARROW 10 AM
SUN THEN DRIFT NORTHWEST AND WEAKEN SLOWLY. SHORT WAVE TROUGH
FROM INUVIK CANADA TO BETHEL WILL SPLIT TO FORM A LOW OVER BRISTOL
BAY 4PM SAT WHICH WILL MOVE SOUTH AND CAUSE EXISTING LOWS IN THE
GULF OF ALASKA TO MOVE NORTH OVER THE EASTERN INTERIOR AS
WEAKENING SHORT WAVES SAT PM THROUGH MON.

SURFACE...983 MB LOW NEAR 80N 170E MOVING TO 480 MILES NORTHWEST
OF BARROW 10 AM SUN AT 976 MB...THEN FILLING SLOWLY AND DRIFTING
NORTHWEST. A WEAK WARM FRONT ASSOCIATED WITH IT WILL MOVE OVER THE
WESTERN NORTH SLOPE AND SOUTHERN CHUKCHI SEA TONIGHT AND EARLY
SUNDAY WHILE THE COLD FRONT SWEEPS IN LATE SUNDAY AND SUNDAY
NIGHT MOVING SOUTH OVER THE CHUKCHI SEA AND NORTH BERING SEA.
RIDGE OF HIGH PRESSURE ACROSS BROOKS RANGE WEAKENING WHILE MAIN
RIDGE OVER EASTERN RUSSIA SPREADS SOUTH OVER THE BERING SEA.
SEVERAL 978 MB LOWS IN THE GULF OF ALASKA WILL CONSOLIDATE THROUGH
THE WEEKEND AND DEEPEN TO 971 MB 4AM MON WITH A 981 MB LOW EAST OF
NORTHWAY WHICH WILL DRIFT NORTH ALONG THE BORDER.

MODELS...IN SHORT TERM AGREE WELL ON LOW IN HIGH ARCTIC AND
PATTERNS ALOFT. NAM TREATS SHORT WAVES..AND RESULTANT SNOW MOVING
NORTHWEST OVER EASTERN INTERIOR DIFFERENT THAN GFS AND ECMWF. FOR
NOW WILL FAVOR GFS AND ECMWF...WHICH HAS VERY LITTLE MOVING NORTH
SAT NIGHT...BUT RATHER HAS THE MAIN OVERRUNNING PRECIP BREAKING
OUT SUN NIGHT AND MON AM WITH THE SECOND SHORT WAVE. IN MEDIUM
TERM GFS AND ECMWF ARE SIMILAR THROUGH DAY 5 THEN BEGIN TO DIVERGE
WITH THE ECMWF WANTING TO BUILD A STRONGER RIDGE ALOFT EAST ACROSS
THE NORTH SLOPE.

NORTH SLOPE...PERSISTENT ONSHORE OR ALONGSHORE FLOW WILL KEEP SNOW
SHOWERS OCCURRING AT LEAST INTERMITTENTLY...SNOW SHOWERS SHOULD
PICK UP TONIGHT OVER ZONES 201 AND 202 AS WARM FRONT MOVES
THROUGH...AND SPREAD OVER 205 SUN.

WESTERN ALASKA...SNOW SHOWERS WILL OCCUR IN THE NORTHERLY FLOW
OVER THE OUTER COASTAL AREAS...ZONES 207 AND 213. AS THE COLD
FRONT MOVES SOUTH OVER THE AREA A FEW SNOW SHOWERS ARE EXPECTED
SUN NIGHT INTO MONDAY OVER COASTAL ZONES FARTHER EAST.

CENTRAL AND EASTERN INTERIOR...A WEAK OCCLUSION OVER THE EASTERN
GULF OF ALASKA IS MOVING NORTHEAST INTO CANADA AND WILL BRING
A FEW SNOW SHOWERS TO THE SOUTHEAST INTERIOR TODAY. A TROUGH OR
DISSIPATING UPPER LOW WILL MOVE NORTH SUN NIGHT AND MON...AND
SPREAD SNOW NORTHWEST. EXPECT AMOUNTS TO BE SMALL MOST AREAS AS
THERE IS ONLY WEAK OVERRUNNING OF THE COLD AIR MASS.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...THERE IS POTENTIAL FOR
HIGH SURF AT SHISHMAREF SUN EVE THROUGH MON AM IF WIND SPEEDS ARE
STRONG ENOUGH. LATER MONDAY WINDS BECOME NORTH THUS TRANSPORTING
SURF SLIGHTLY AWAY FROM SHORE.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ200-PKZ210-PKZ225-PKZ230-PKZ235-
PKZ245.
&&

JL OCT 12