Small Craft Advisory 703, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT SAT OCT 1 2011

.MODEL DISCUSSION...
MODEL INITIALIZATIONS WERE FAIR. FORECAST TRENDS LOOK THE BEST USING
THE 12Z GFS/OOZ ECMWF OUT WEST AND THE 12Z ECMWF IN THE EAST. STRONG
WESTERLY JET OVER THE NORTH PACIFIC AND WAVE MOVING NORTH ALONG A
BAROCLINIC ZONE IN THE DATA SPARSE NE PACIFIC WILL BE THE MAIN
FORECAST CHALLENGES.

.ANALYSIS AND UPPER LEVELS...

.UPPER LEVELS...A BROAD TROUGH REGION ENCOMPASSES MAINLAND ALASKA
FROM THE GULF TO THE ARCTIC OCEAN. WITHIN THIS TROUGH...AN UPPER
LEVEL LOW CENTERED SOUTH OF KODIAK ISLAND COVERS MUCH OF THE GULF OF
ALASKA. TO THE WEST...A RIDGE COVERS MUCH OF THE WESTERN AND CENTRAL
BERING SEA. AN UPPER LEVEL LOW IS DEVELOPING RAPIDLY OVER THE
KAMCHATKA PENINSULA. ITS ASSOCIATED JET IS CURRENTLY AT 150 KT AND
EXPECTED TO INCREASE TO 180 KT DURING THE DAY TODAY. THIS RAPIDLY
DEVELOPING LOW WILL IMPACT MUCH OF THE BERING THIS WEEKEND.

.SHORT TERM FORECAST...

.SOUTHCENTRAL...THE MAIN FORECAST CHALLENGE OVER THE NEXT 24 HRS IS
THE HANDLING OF A WAVE DEVELOPING ALONG THE N/S BAROCLINIC ZONE OVER
THE NE PACIFIC/GULF OF ALASKA. THE ECMWF SOLUTION OF BRINGING THE
WAVE TO NEAR THE BARREN ISLANDS WITH A PRESSURE IN THE UPPER 980S TO
LOWER 990S SUN AFTERNOON APPEARS TO BE THE MOST REASONABLE SOLUTION
IN LIGHT OF STRONG STEERING FLOW ALOFT AND DYNAMICS. THE TIMING OF
THE DIMINISHING OF THE WINDS WILL BE A CHALLENGE AND LIKELY WILL
REQUIRE SOME TWEEKING AS TIMING OF WAVE IS STILL SOMEWHAT IN
QUESTION. FOR NOW EXPECT GALE TO STORM FORCE WINDS OVER MUCH OF THE
NORTH GULF THROUGH SUN AFTERNOON...THEN DIMINISHING SUN NIGHT.
PRESSURE DRIVEN GAP FLOWS ACROSS SOUTHCENTRAL (ESPECIALLY TURNAGAIN
ARM/EASTERN KENAI) WILL INCREASE OVERNIGHT AND REACH THERE MAXIMUM ON
SUN...BEFORE DIMINISHING LATE SUN. RAIN OVER SOME INLAND AREAS THIS
AFTERNOON/EVENING WILL LARGELY BE CONFINED TO THE COASTS OVERNIGHT
WITH THE ONSET OF STRONG SE WINDS ALOFT. RAIN WILL LIKELY SPREAD TO
INLAND AREAS SUN AS LOW MOVES THROUGH COOK INLET.

.SOUTHWEST MAINLAND...GENERALLY NORTHERLY OFFSHORE FLOW WILL WEAKEN
THROUGH THIS AFTERNOON. MOISTURE WILL SPREAD IN FROM THE GULF
OVERNIGHT BRINGING A CHANCE OF SHOWERS...MAINLY THE EAST HALF OF THE
REGION. RAIN ASSOCIATED WITH THE FRONT MOVING EAST ACROSS THE BERING
SEA BRINGS IN RAIN TO THE DELTA AND BRISTOL BAY SUN NIGHT.

.ALEUTIANS/BERING SEA...A STORM FORCE LOW CENTER OVER THE WESTERN
BERING SEA SLOWLY WEAKENS AS IT MOVES EAST ACROSS THE BERING SUN AND
MON. STRONG WINDS ITS SOUTHERN PERIPHERY ARE SUPPORTED BY STRONG
SURFACE GRADIENTS AND DOWNWARD MOMENTUM TRANSPORT WITH UPPER
JET...AND WEAK COLD ADVECTION. THE NET RESULT WILL BE WESTERLY
GALE/STORM FORCE WINDS SPREADING ACROSS THE ALEUTIANS TONIGHT AND
SUN. BY MON AFTERNOON...THE ONLY GALES EXPECTED WILL BE ACROSS THE
FAR EAST ALEUTIANS.

.LONG TERM...THE JET STREAM WILL REMAIN IN THE NORTH PACIFIC OVER THE
NEXT WEEK. AS A RESULT...AN ACTIVE PATTERN WILL CONTINUE AS A SERIES
OF TROUGHS AND RIDGES PROGRESS ACROSS THE AREA.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...
MARINE...STORMS...120 175 176
         GALES...125 129 155 185 170 172
FIRE WEATHER...

RMC OCT 11