Small Craft Advisory 683, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
422 PM AKDT SAT SEP 7 2013

CORRECTED TYPO

.MODEL DISCUSSION...
MODELS ARE IN RELATIVELY GOOD SYNOPTIC AGREEMENT THROUGH THE SHORT
TERM. THE GFS THOUGH IS A LITTLE MORE AGGRESSIVE ON THE PRESSURE WITH
THE LOW CENTER HEADING TO THE E GULF TONIGHT. SATELLITE IMAGERY WOULD
SUPPORT THE MORE AGGRESSIVE GFS SOLUTION. MODELS ARE IN GENERAL
AGREEMENT IN THE QPF PRECIPITATION PATTERN...THOUGH THE ECMWF/GFS
"BROAD BRUSH" THE VALUES ACROSS SOUTHCENTRAL WITH THE LOW APPROACHING
THE EASTERN GULF COAST TONIGHT.

.ANALYSIS AND UPPER LEVELS...

UPPER LEVELS...THIS MORNINGS WATER VAPOR IMAGERY INDICATES THAT THE
DEEP SOUTHERLY FETCH OF MOISTURE HAS SHIFTED TO THE EASTERN GULF. THE
LOW OVER THE COOK INLET REGION OVERNIGHT IS MOVING NORTH AND
WEAKENING. A DEVELOPING LOW SOUTH OF THE GULF IS MOVING RAPIDLY
NORTH. A WEAK CENTER IS LOCATED OVER BRISTOL BAY WITH A MORE
PROMINENT LOW CENTER NEAR THE WESTERN ALEUTIANS.

THE WAVE SOUTH OF THE GULF WILL MOVE RAPIDLY NORTH TONIGHT TO OVER
THE YUKON TERRITORY SUN AFTERNOON. THE BRUNT OF THE ENERGY IMPACTS SE
ALASKA AND THE EASTERN GULF COAST...AND TO A LESSER EXTENT THE
WESTERN GULF AND COPPER RIVER BASIN. THE UPPER CENTER OVER BRISTOL
BAY WILL DRIFT NE THROUGH SUN AND UNDERGO LITTLE CHANGE IN
INTENSITY. THE CENTER NEAR THE WESTERN ALEUTIANS MOVES RAPIDLY EAST
TO SOUTH OF THE AK PEN LATE SUN SETTING UP BROAD SOUTHERLY TO SE
FLOW OVER THE GULF/SOUTHCENTRAL. A HIGH AMPLITUDE RIDGE BUILDS
ACROSS THE BERING SEA IN THE WAKE OF THIS CENTER.

SURFACE...RAIN HAS TAPERED OFF ACROSS MUCH OF THE NORTH GULF COAST
AND SOUTHCENTRAL ALASKA THIS AFTERNOON. ANOTHER BATCH OF
RAIN...THOUGH NOT NEARLY AS HEAVY...IS EXPECTED TO SPREAD TO THE
GULF COAST LATER TODAY AND INTO THE COPPER RIVER BASIN OVERNIGHT. A
WEAK LOW OVER THE COPPER RIVER BASIN WEAKENS AND WILL DRIFT SLOWLY
NW THROUGH SUNDAY. A 980S LOW SOUTH OF THE WESTERN ALEUTIANS MOVES
EAST UNDER THE UPPER CENTER TO SOUTH OF THE AK PEN SUN NIGHT AND
MONDAY AND WEAKENS.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...A DEVELOPING LOW SOUTH OF THE GULF MOVES TO
THE EASTERN GULF TONIGHT AND INTO THE YUKON TERRITORY SUN. THIS
CENTER WILL BRING RENEWED RAINS TO THE NORTH GULF AND A FRESH BATCH
TO THE COPPER RIVER BASIN TONIGHT AND SUN. RAIN SHOULD DIMINISH
ACROSS THE NORTH GULF ON SUN AFTERNOON AND OVER THE COPPER RIVER
BASIN SUN EVENING AS THE LOW CONTINUES TO TRACK NORTH. A LOW MOVING
SOUTH OF THE AK PEN WILL BRING GALES TO THE WESTERN GULF SUN NIGHT.
GALES WILL LIKELY SPREAD ACROSS THE GULF THROUGH MON. STRONG GAP
FLOWS ARE EXPECTED TO DEVELOP ACROSS SOUTHCENTRAL...ESPECIALLY ALONG
TURNAGAIN ARM AND HIGHER ELEVATIONS OF ANCHORAGE.

SOUTHWEST ALASKA...A FEW AREAS OF INSTABILITY REMAIN OVER SOUTHWEST
ALASKA WHICH CONTINUES TO BRING SHOWERS TO THE AREA THROUGHOUT THE
DAY TODAY AND INTO THE WEEKEND. A NEW LOW PUSHES INTO THE ALASKA
PENINSULA SUNDAY AFTERNOON AND WILL BRING STEADIER PRECIPITATION AND
GUSTY GAP WINDS THROUGH MONDAY AFTERNOON.

BERING SEA AND ALEUTIANS...LOW PRESSURE TRACKING SOUTH OF THE
ALEUTIAN CHAIN CONTINUES TO DEEPEN TODAY AND PRODUCE STRONG WINDS AND
STEADY PRECIPITATION FOR THE CENTRAL AND EASTERN ALEUTIANS THROUGH
SUNDAY AFTERNOON. WINDS WILL BEGIN TO DIMINISH AS THE LOW WEAKENS AND
TRACKS INTO THE ALASKA PENINSULA MONDAY AFTERNOON. HIGH PRESSURE WILL
THEN BEGIN TO BUILD OVER THE WESTERN ALEUTIANS LATE SUNDAY NIGHT.

.LONG TERM FORECAST...
LATE IN THE WEEK THE PATTERN WILL BECOME MORE AMPLIFIED WITH RIDGING
BUILDING IN OVER THE BERING AND ALEUTIANS. OVER MAINLAND ALASKA A
BROAD UPPER LEVEL LOW WILL MOVE ACROSS THE STATE FROM NORTH TO SOUTH
BRINGING AREAS OF PRECIPITATION WITH IT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 130 138 150 155 172 170 175.
FIRE WEATHER...NONE.

RMC/TP SEP 13