Issued by NWS Anchorage, AK
000 FXAK68 PAFC 151332 AFDAFC AREA FORECAST DISCUSSION SOUTHCENTRAL AND SOUTHWEST ALASKA 500 AM AKST SUN FEB 15 2009 .ANALYSIS AND UPPER LEVELS... AT THE SURFACE...THE MAIN FEATURE OF INTEREST IS A 980 MB LOW LOCATED JUST SOUTHEAST OF SAINT PAUL. A FRONT ASSOCIATED WITH THIS LOW STRETCHES OVER THE ALASKA PENINSULA AND INTO THE WESTERN GULF OF ALASKA. WEAK RIDGING IS LOCATED OVER THE EASTERN GULF OF ALASKA. A 985 MB NORTH PACIFIC LOW IS LOCATED NEAR 47N 163E. IN THE UPPER LEVELS...AN ARCTIC VORTEX IS LOCATED OVER EASTERN SIBERIA WITH A TROUGH EXTENDING THROUGH THE BERING SEA AND EASTERN ALEUTIANS. RIDGING IS LOCATED OVER THE ALASKA MAINLAND AND THROUGH THE EASTERN GULF OF ALASKA. A ROBUST SHORTWAVE IS LOCATED OVER THE WESTERN ALEUTIANS. DUE TO THE POSITIONING OF THESE SYSTEMS...SOUTHWESTERLY FLOW CONTINUES ACROSS THE AREA. .MODEL DISCUSSION... MODELS INITIALIZED WELL THIS MORNING WITH GOOD AGREEMENT THROUGH 00Z WEDNESDAY. ONE EXCEPTION PERTAINS TO A TRIPLE POINT LOW EXPECTED TO DEVELOP NEAR KODIAK ISLAND MONDAY MORNING. THE NAM AND GFS SOLUTIONS ARE OUTLIERS...WHEREAS THE ECMWF/UKMET SOLUTIONS PROVIDE A GOOD MEAN SOLUTION. ACCORDINGLY...THE MORNING FORECAST WAS CONSTRUCTED USING THE ECMWF SOLUTION THROUGH WEDNESDAY. .SHORT TERM FORECAST... .SOUTHCENTRAL... THE AFOREMENTIONED FRONT IS MAKING ITS WAY NORTHWARD THIS MORNING...CONSTITUTING THE MAIN FORECAST PROBLEM ACROSS SOUTHCENTRAL IN THE SHORT TERM. PRECIPITATION ASSOCIATED WITH THIS FRONT HAS OVERSPREAD THE MAJORITY OF THE AREA...WITH A SNOW RAIN MIX FALLING ALONG COASTAL AREAS AND SNOW FURTHER INLAND. DEEP SOUTHERLY FLOW ACCOMPANYING THE FRONT IS LEADING TO UPSLOPE SNOW ALONG THE ALASKA RANGE...ALTHOUGH EXPECT ACCUMULATIONS TO REMAIN BELOW CRITERIA LEVELS AT THIS POINT. ACROSS THE ANCHORAGE BOWL...EXPECT DOWNSLOPING TO LIMIT PRECIPITATION TO NOTHING MORE THAN A FEW FLURRIES. ONE FINAL CONCERN IS THE WIND FORECAST FOR ANCHORAGE. AT THIS TIME THE PRESSURE GRADIENT IS EXPECTED TO REMAIN HIGHEST FROM ANCHORAGE SOUTH...MEANING GUSTY TURNAGAIN ARM WINDS WILL LIKELY REMAIN OVER THE INLET. ANY GUSTY WINDS THAT MAKE IT INTO TOWN HAVE THE POTENTIAL TO MIX DOWN MUCH WARMER AIR THAN WOULD OTHERWISE MAKE IT TO THE SURFACE. WINDS WILL BE DECREASING THROUGH CHANNELED TERRAIN AND HIGHER ELEVATIONS TONIGHT...AS THE FRONT DISSIPATES AND THE PRESSURE GRADIENT BEGINS RELAXING. .SOUTHWEST... AS THE LOW CONTINUES TO MOVE INLAND TODAY STRONG WIND AND SNOW WILL LEAD TO BLIZZARD CONDITIONS OVER PORTIONS OF BRISTOL BAY AND THE KUSKOKWIM DELTA. GUSTY WINDS AND SNOW WILL CONTINUE OVER THE REMAINDER OF SOUTHWEST TODAY...BUT CONDITIONS SHOULD BE IMPROVING AS WE HEAD INTO THIS AFTERNOON. WARM AIR AHEAD OF THE LOW WILL CREATE A RAIN AND SNOW MIX ACROSS THE ALASKA PENINSULA...BUT SHOULD CHANGE BACK TO ALL SNOW BY TONIGHT ONCE COLD AIR WRAPS BACK INTO THE AREA. CONDITIONS ACROSS SOUTHWEST WILL BE IMPROVING THROUGH THE DAY ON MONDAY...WITH LIGHTER WINDS AND SCATTERED SNOW SHOWERS THROUGH TUESDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. .BERING SEA AND ALEUTIANS... STRONG NORTHERLY WINDS ON THE BACKSIDE OF THE LOW CONTINUE TO CREATE PROBLEMS ACROSS THE PRIBILOFS...WITH BLIZZARD CONDITIONS CONTINUING THROUGH TODAY. STRONG NORTHERLY FLOW ACROSS THE EASTERN ALEUTIANS WILL BE SWITCHING PRECIPITATION BACK TO SNOW...WITH BLOWING SNOW POSSIBLE THIS AFTERNOON INTO TONIGHT. ELSEWHERE...EXPECT SCATTERED RAIN AND SNOW SHOWERS TO PERSIST THROUGH TODAY. AS THE LOW SOUTHWEST OF SHEMYA MOVES ALONG THE CHAIN ON MONDAY...RAIN AND SNOW WILL BE ON THE INCREASE ACCOMPANIED BY GUSTY SOUTHERLY FLOW. .LONG TERM FORECAST... AS PREVIOUSLY MENTIONED...MODELS CONTINUE TO HINT AT A MORE AMPLIFIED PATTERN IN THE EXTENDED. A RIDGE IS EXPECTED TO BUILD OVER MAINLAND ALASKA BY MIDWEEK WITH FAST SOUTHWEST TO NORTHEAST FLOW DEVELOPING. AS A RESULT...A PROGRESSIVE WEATHER PATTERN IS EXPECTED TO CONTINUE ACROSS THE AREA. .AER/ALU...WATCH/WARNING SUMMARY PUBLIC...BLIZZARD WARNING...155 161 195 MARINE...GALE WARNING...120 130 132 155 170 172 176 179 352 412 413 414 HEAVY FREEZING SPRAY WARNING...165 179 412 414 FIRE WEATHER...NONE NRH FEB 09