Small Craft Advisory 579, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKDT FRI AUG 2 2013

.ANALYSIS AND UPPER LEVELS...
SOUTHERN ALASKA CONTINUES TO FEEL MORE AND MORE INFLUENCE FROM THE
UPPER TROUGH OVER THE BERING AND NORTHERN PACIFIC. THE POTENT
SHORTWAVE THAT ROUNDED THE BASE OF THE LONG-WAVE YESTERDAY IS NOW
BECOMING THE MAIN UPPER LOW CENTER APPROACHING THE ALASKA PENINSULA.
WATER VAPOR IMAGERY SUGGESTS A MATURE OCCLUDED SYSTEM IN THE 980 MB
RANGE. THE SOUTHWEST MAINLAND IS CURRENTLY SEEING SHOWERY
PRECIPITATION WITHIN THE CYCLONIC FLOW ALOFT BUT THE BULK OF THE
ACTIVITY IS CONFINED TO THE ALASKA PENINSULA AND SOUTHWARD...CLOSER TO
THE SURFACE LOW. TOWARD THE EASTERN DOMAIN...THE FRONT ASSOCIATED WITH
THE LOW IS APPROACHING KODIAK ISLAND. HIGH PRESSURE OVER THE EASTERN
GULF AND NORTH GULF COAST CONTINUES TO BUILD THE SURFACE PRESSURE
GRADIENT OVER WESTERN PRINCE WILLIAM SOUND LEADING TO A TURNAGAIN ARM
WIND WITH STRONGEST VALUES IN THE WESTERN PORTION OF THE ARM NEAR BIRD
POINT AND MCHUGH CREEK...ALREADY BLOWING 25 TO 35 MPH THIS AFTERNOON.

.MODEL DISCUSSION...
GUIDANCE CONTINUES TO STRUGGLE WITH THE EXACT NATURE OF THE
APPROACHING SURFACE LOW...HOWEVER ALL GUIDANCE BRINGS THE LOW JUST
WEST OF KODIAK ISLAND TONIGHT THEN PAST INTERIOR BRISTOL BAY/KUSKOKWIM
DELTA AREA TOMORROW INTO SUNDAY. BOTH DOMAINS PREFER THE NAM SOLUTION
FOR DETAILS.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...SHOWERY PRECIPITATION WILL CONTINUE WITH THE
ONSHORE FLOW AHEAD OF THE APPROACHING FRONT NEAR KODIAK ISLAND THIS
AFTERNOON. THE FRONT WILL MOVE OVERHEAD THE MAINLAND THIS EVENING INTO
SATURDAY MORNING. TURNAGAIN ARM/HIGHER ELEVATION WIND WILL BE THE MAIN
CONCERN THROUGH THE WEEKEND WITH VALUES PEAKING TOMORROW AFTERNOON
UPWARDS OF 60 MPH. COASTAL AREAS WILL SEE THE BRUNT OF FRONTAL
PRECIPITATION WITH THE SYSTEM WHILE THE MATANUSKA VALLEY THROUGH THE
WESTERN KENAI PENINSULA SHOULD STAY DOWN-SLOPED AND MAINLY DRY THOUGH
PERIODS OF LIGHT RAIN OR SPRINKLES WILL BE POSSIBLE. GUSTY WINDS OFF
OF THE ARM WILL ALSO BEGIN TO AFFECT SOUTH AND WEST ANCHORAGE TOMORROW
AFTERNOON WITH THE NORTHWARD PROGRESSION OF THE SURFACE LOW. ONCE THE
FRONT PASSES TOMORROW PRECIPITATION WILL MAINLY BE CONTAINED TO
COASTAL AREAS AND THE WESTERN SUSITNA VALLEY BUT WITH THE UPPER TROUGH
STAYING OVERHEAD THROUGH THE SHORT TERM THE CHANCE FOR RAIN STAYS IN
THE FORECAST.

SOUTHWEST ALASKA...SPOTTY SHOWERS WILL GIVE WAY TO STEADIER RAIN IN
THE BRISTOL BAY AREA THIS AFTERNOON AS THE OCCLUDED FRONT PUSHES
OVERHEAD AND THE AREA BECOMES MORE UNDER THE INFLUENCE OF THE LOW
PRESSURE SYSTEM. GUSTY EASTERLY WINDS...ESPECIALLY THROUGH GAPS ALONG
THE ALEUTIAN RANGE WILL INCREASE TONIGHT. THE STOUT SOUTHEASTERLY
WINDS WILL CONTINUE THROUGH TOMORROW AFTERNOON BEFORE BEGINNING TO
SUBSIDE. STEADY RAIN WILL PERSIST THROUGH LATE SATURDAY NIGHT BEFORE
BECOMING MORE SHOWERY.

BERING SEA AND ALEUTIANS...WIDESPREAD LOW STRATUS ENCOMPASSES MOST OF
THE BERING. ISOLATED SHOWERS ARE POSSIBLE OVER MOST OF THE BERING WITH
MORE WIDESPREAD RAIN CLOSER TO BRISTOL BAY ASSOCIATED WITH THE ALASKA
PENINSULA LOW. GUSTY CHANNELED TERRAIN WINDS ARE POSSIBLE FOR A SHORT
PERIOD THIS EVENING THROUGH THE OVERNIGHT MAINLY FOR THE SOUTH SIDE OF
THE ALASKA PENINSULA.

.LONG TERM FORECAST...
THE EXTENDED FORECAST LOOKS VERY SIMILAR TO THE CURRENT STATE OF THE
ATMOSPHERE. GENERAL TROUGHING OVER THE SOUTHWEST/BERING/AKPEN WILL
KEEP THE ACTIVE WEATHER PATTERN GOING WITH PERIODIC FRONTAL PASSAGES
AND DISTURBANCES ALOFT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 120 130 132 136 137 138 150
FIRE WEATHER...NONE

MTL AUG 13