049 FXAK62 PAFC 161259 AFDALU AREA FORECAST DISCUSSION SOUTHWEST ALASKA 500 AM AST WED MAR 16 2005 .DISCUSSION... .ANALYSIS...A VERY WEAK SURFACE FRONT LIES FROM KOTZEBUE SOUND SOUTHEASTWARD TO KODIAK ISLAND. MOST OF SOUTHWEST ALASKA EXPERIENCED A PERIOD OF LIGHT SNOW ACCOMPANIED BY LOW CEILINGS AND FOG LAST EVENING. LIGHT SNOW CONTINUES FOR PARTS OF THE KUSKOKWIM VALLEY AND INTERIOR BRISTOL BAY. ONSHORE FLOW BEHIND THE FRONT IS MAINTAINING FOG AND STRATUS ACROSS THE REGION. ON THE EAST SIDE OF THE ALASKA AND ALEUTIAN RANGES THE ONLY IMPACT HAS BEEN TO LOWER CEILINGS TO 5 TO 10 THOUSAND FEET. WATER VAPOR SHOWS A WELL DEFINED VORT MAX NEAR KODIAK ISLAND LAST EVENING QUICKLY ELONGATED AS IT MOVED TOWARD THE KENAI PENINSULA. THE ONLY OTHER SIGNIFICANT FEATURE ON THE SCOPE TONIGHT IS A LARGE CUT OFF LOW NEAR 44N/170W WITH AN ESTIMATED CENTRAL PRESSURE OF 985 MB. THIS LOW AND ASSOCIATED FRONTS ARE CURRENTLY TOO FAR SOUTH TO PROVIDE ANY PROBLEMS FOR THE ALEUTIAN CHAIN. MOST OF THE BERING REGION IS PARTLY CLOUDY WITH AREAS OF FOG AND ISOLATED SNOW SHOWERS. DAY 1 THROUGH 3 FORECAST...MODEL COMPARISON SHOWS ETA/UKMET/GFS IN FAIR AGREEMENT WITH SYNOPTIC SOLUTION. MAIN DIFFERENCES LIE WITH THE EVOLUTION OF THE LOW SOUTH OF THE ALEUTIANS AND THE PROGRESSION OF THE ACCOMPANYING FRONT THAT MOVES ACROSS THE ALEUTIANS. HAVE DECIDED TO GO WITH THE GFS BECAUSE IT HAS THE BEST HANDLE ON THE POSITION OF THE LOW. ALSO ECMWF MATCHES UP WELL WITH THE GFS SOLUTION. FRONT IN THE EAST WILL CONTINUE TO FALL APART THIS MORNING WITH SNOW ENDING ACROSS SOUTHWEST ALASKA AND NO MORE THAN FLURRIES EXPECTED ACROSS SOUTH CENTRAL ALASKA. HIGH PRESSURE RIDGE WILL BUILD BEHIND THE FRONT FROM SOUTHWEST ALASKA SOUTHEASTWARD ACROSS THE GULF OF ALASKA. AS THE HIGH BUILDS INLAND FLOW WILL BECOME OFFSHORE OVER SOUTHWEST ALASKA AND HELP TO SCOUR OUT FOG/STRATUS THIS AFTERNOON AND EVENING. UPPER RIDGE WILL BECOME CENTERED OVER SOUTHWEST ALASKA BY FRIDAY. THEREFORE EXPECT VERY NICE WEATHER ACROSS THE SOUTHERN MAINLAND THROUGH THE END OF THE WEEK. THE LOW SOUTH OF THE ALEUTIANS WILL WANDER EASTWARD AS RIDGE BUILDING AHEAD OF IT BLOCKS IT FROM ANY SIGNIFICANT MOTION. WARM FRONT WILL MOVE TO EASTERN ALEUTIANS THURSDAY MORNING AS BENT BACK OCCLUSION TRACKS WESTWARD ACROSS ALEUTIANS AND SOUTHERN BERING. EXPECT GALE FORCE WINDS AND RAIN TO OVERSPREAD THE REGION WEDNESDAY NIGHT AND THURSDAY AND THEN DISSIPATE FRIDAY AS BUILDING RIDGE PUSHES EVERYTHING WESTWARD A BIT. DAY 4 THROUGH 7 FORECAST...RIDGE RETROGRADES NORTHWESTWARD SATURDAY AND SHORTWAVE DROPS SOUTHWARD ACROSS MAINLAND ALASKA. THIS SCENARIO WOULD PROVIDE ACCESS TO ARCTIC AIR AND RESULT IN THE POTENTIAL FOR A MODERATE TO STRONG WIND EVENT OVER SOUTHCENTRAL/SOUTHWEST ALASKA SATURDAY NIGHT AND SUNDAY. THE EXACT POSITION OF THE RIDGE IS KEY TO TARGETING WHICH AREAS ARE AT MOST RISK FOR A WIND EVENT. THIS BEARS WATCHING CLOSELY OVER THE NEXT FEW DAYS. IN ANY CASE EXTENDED PERIOD LOOKS COOLER THAN THE PAST FEW WEEKS. OUT WEST A SHORTWAVE TROUGH MOVES OUT OF ASIA AND APPROACHES THE ALEUTIANS OVER THE WEEKEND. THIS WILL PUSH A SURFACE FRONT TO THE ALEUTIANS BEFORE THE RIDGE FORCES IT TO STALL. WITH RIDGE HOLDING OVER NORTHERN MAINLAND DAYS 6 AND 7 MOST OF THE ACTIVE WEATHER SHOULD REMAIN OVER THE BERING SEA REGION AND AWAY FROM THE MAINLAND. .AER/ALU...WATCH/WARNING SUMMARY PUBLIC...NONE. MARINE...GALES 5B 12A 12A1 12B. SEB MAR 05 |