Small Craft Advisory 243, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1130 AM AST SUN MAR 20 2005

.DISCUSSION...
ANALYSIS - A STRONG HIGH OVER LOW BLOCKING PATTERN HAS SET UP ALONG
170W WHICH DRIVES A NORTH FLOW ALOFT OVER MUCH OF THE FORECAST AREA.
A SURFACE LOW HAS DEVELOPED IN THE CENTRAL GULF BELOW 999 MB BUT THE
CENTER IS HARD TO SEE ON GOES-10 VISIBLE SO FAR THIS MORNING. A
SURFACE HIGH CELL AT 1056 MB IS N OF BARROW AT 12Z. THE FRONT OVER
THE WESTERN ALEUTIANS CONTINUES TO WEAKEN AGAINST THE BLOCK AND A 994
MB LOW HAS DEVELOPED ON THE FRONT NEAR 43N 177E AS PER YESTERDAYS
MODELS. AT 250 MB THE JET UNDERCUTS THIS WHOLE SYSTEM ALONG 30N OR
SO. A NW BRANCH IS OVER THE BARREN ISLANDS THIS MORNING AT AROUND 100
KNOTS. STRONG SURFACE WINDS HAVE BEGUN ACROSS MOST OF THE AREA THIS
MORNING. GOES-10 VISIBLE DOES REVEAL A SECONDARY SURFACE LOW NEAR
ATKA AS OF 20Z BUT IT LOOKS VERY WEAK.

AER FORECASTS - THE 12Z ETA MODEL IS PREFERRED FOR THIS WIND EVENT
BECAUSE OF THE DETAIL IN PLACEMENT OF THE MAIN SURFACE LOW OFF KODIAK
BY 12Z MONDAY. THIS SETS UP MORE OF A LOW LEVEL JET DOWN COOK INLET
FROM WASILLA. TEMPERATURE ADVECTION IS COLD WITH UPPER LEVEL SUPPORT
AND DOWNWARD VERTICAL MOTION FOR A PRETTY GOOD WIND EVENT. DRY
CONDITIONS PLUS BLOWING DUST ARE ALSO CONCERNS. ALL MODELS SHOW
SURFACE PRESSURE GRADIENTS PERSISTING THROUGH 12Z TUE FOR CONTINUED
WIND. SERIOUS MODEL DISAGREEMENT OCCURS BEYOND 12Z TUE AS TO WHERE
THE SURFACE LOW CENTER ENDS UP BUT ALL IMPLY WESTWARD MOVEMENT OF THE
LOW FOR A SWITCH TO ONSHORE LOW LEVEL FLOW IN THE GULF.

ALU FORECASTS - OFFSHORE FLOW PERSISTS FOR MUCH OF SW ALASKA WITH
TEMPERATURES ON THE COLD SIDE EVEN WITH SUNSHINE. THE FRONT OVER THE
WESTERN BERING SEA WILL CONTINUE TO DISSIPATE AS PER ALL MODELS. THIS
ALLOWS A SURFACE RIDGE TO BUILD OVER THE CENTRAL AND WESTERN BERING
SEA AS THE LOW NEAR 43N 177E MOVES SE. THE MARINE CLOUDS OVER DUTCH
AND SAINT PAUL NOW SHOULD RETREAT S AS THIS RIDGE BUILDS. BY TUE THE
GULF LOW IS FORECASTED TO MOVE OVER COLD BAY BY THE GFS-190...BUT
COMPARISONS TO OTHER MODELS MAKES THIS FORECAST LOOK QUITE UNCERTAIN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 111 131 135.
         WIND ADVSRY 101 141 145 155 161.
MARINE...GALES 120 121 130 138 140. HVY FRZ SPRAY 121 140.
FIRE WEATHER...NONE.

JC MAR 05