Blizzard in Alaska, March 21, 2008

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
150 PM ADT FRI MAR 21 2008

.ANALYSIS AND UPPER LEVELS...LARGE UPPER LEVEL ANCHOR LOW THAT WAS
OVER THE EASTERN BERING WEDNESDAY HAS NOW MOVED SOUTHWARD ACROSS THE
ALASKA PENINSULA...USHERING LOTS OF COLD AIR DOWN ACROSS THE BERING
AND ALEUTIANS INTO THE NORTH PACIFIC. SURFACE TEMPERATURES FROM THE
PRIBILOFS TO THE EASTERN ALEUTIANS AND ALASKA PENINSULA ARE IN THE
SINGLE DIGITS TO LOWER TEENS. COLD ADVECTION ACROSS THE OPEN BERING
SEA WATERS CONTINUES TO PRODUCE WIDESPREAD LAKE EFFECT SNOW
SHOWERS. THERE ARE SEVERAL UPPER WAVES/SURFACE LOWS EMBEDDED WITHIN
THE LARGE UPPER CIRCULATION...MAINLY DOWNSTREAM OF THE LOW CENTER
OVER THE NORTHEAST PACIFIC AND GULF OF ALASKA. SATELLITE IMAGERY
SHOWS ONE LOW (AROUND 993 MB) IS MOVING WESTWARD ACROSS THE NORTHERN
GULF. COLD CLOUD TOPS PLUS MIDDLETON ISLAND RADAR SHOW AN UNSTABLE
AIR MASS WITH IMPRESSIVE CONVECTION. MOST OF THE SHOWERS ARE OUT OVER
THE GULF WATERS...BUT HEADING TOWARD KODIAK ISLAND. THERE IS ALSO A
WEAK LOW EAST OF KODIAK ISLAND...BUT IT LOOKS LIKE IT IS MERGING WITH
THE APPROACHING LOW. A WARM OCCLUSION EXTENDING FROM THIS LOW MOVED
SOUTHWESTWARD ACROSS THE BRISTOL BAY LAND AREA THIS MORNING DROPPING
AN INCH OR TWO OF SNOW AND IS NOW HEADED ACROSS BRISTOL BAY TO THE
SOUTHERN ALASKA PENINSULA. DOWN SOUTH OF THE GULF THERE IS ANOTHER
LOW (AT AROUND 990 MB) AT 50N 146W TRACKING NORTH WITH A TRIPLE POINT
LOW OUT AHEAD OF IT NEAR 54N 145W.

.MODEL DISCUSSION...MODELS ARE ALL A BIT OF ON POSITIONS OF NORTHEAST
PACIFIC/GULF OF ALASKA LOWS AN SOLUTIONS CONTINUE TO DIFFER THROUGH
THE SHORT-TERM FORECAST. BOTTOM LINE...THERE WILL BE MULTIPLE LOWS
SWIRLING AROUND THE GULF THROUGH AT LEAST THE BEGINNING OF NEXT WEEK.
CURRENT FORECAST WAS BASED ON GFS AND WILL CONTINUE TO STICK CLOSE
TO THE GFS...WHICH SHOWED FAIRLY GOOD RUN-TO-RUN CONSISTENCY. THE
BIGGEST QUESTION IS WHETHER THE GFS IS CORRECT IN ROTATING A LOW
NORTHWARD ACROSS THE FAR EASTERN GULF SATURDAY NIGHT TO THE NORTHERN
GULF SUNDAY. FOR A WHILE THE GFS WAS THE ONLY MODEL DEPICTING THIS
LOW MOVING TO THE NORTHERN GULF. NOW OTHER MODELS ARE STARTING TO
HINT AT THIS...BUT NOT AS STRONG AND WELL DEFINED AS THE GFS. UNTIL
GAIN MORE CONFIDENCE GFS WIND FORECAST WILL BE TEMPERED A BIT.

.SHORT TERM FORECAST...THE WARM OCCLUSION OVER BRISTOL BAY WILL MOVE
DOWN ACROSS THE ALASKA PENINSULA TONIGHT THROUGH EARLY SATURDAY
MORNING. PRESSURE WILL DROP IN GULF AS NEXT LOW MOVES IN AND HIGH
PRESSURE WILL BUILD OVER WESTERN ALEUTIANS RESULTING IN A TIGHTENING
PRESSURE GRADIENT AND STRENGTHENING WINDS. THE STRONGER WINDS
COMBINED WITH STEADY SNOW IS EXPECTED TO RESULT IN BLIZZARD
CONDITIONS ACROSS THE SOUTHERN ALASKA PENINSULA TONIGHT THROUGH EARLY
SATURDAY. WINDS WILL REMAIN STRONG ON SATURDAY BUT CHARACTER OF SNOW
SHOULD CHANGE BACK TO SHOWERY SO THAT VISIBILITIES WILL MARGINALLY
IMPROVE. EASTERN ALEUTIANS TO PRIBILOFS SHOULD REMAIN SHOWERY SO THAT
IF VISIBILITIES DROP DOWN TO NEAR ZERO IT SHOULD BE BRIEF.

MULTIPLE LOWS WILL ROTATE AROUND THE GULF THE NEXT FEW DAYS. ALMOST
ALL SNOW IS EXPECTED TO REMAIN ALONG COASTAL AREAS WITH JUST A FEW
SHOWERS MAKING IT OVER THE COASTAL MOUNTAINS. IT LOOKS LIKE THE LOWS
WILL REMAIN PROGRESSIVE SO THAT AREAS OF PRECIPITATION WILL NOT SIT
IN ONE PLACE. THIS SHOULD KEEP ALL AREAS...INCLUDING KODIAK
ISLAND...BELOW SNOW ADVISORY CRITERIA. THE OTHER CONCERN WAS THE
POTENTIAL FOR BLIZZARD CONDITIONS ON KODIAK ISLAND...BUT A NORTHEAST
COMPONENT TO LOW LEVEL WINDS SHOULD KEEP AIR TEMPERATURES WARM ENOUGH
TO PREVENT REALLY LOW VISIBILITIES. SINCE THERE IS UNCERTAINTY IN
TRACKS OF THE LOWS WILL CONTINUE TO MONITOR AND RE-EVALUATE THIS
POTENTIAL.

.LONG TERM FORECAST...MEAN POSITION OF TROUGH WILL REMAIN OVER
MAINLAND ALASKA AND THE GULF. THEREFORE...SO NOT EXPECT ANY MAJOR
CHANGES FROM THE CURRENT WEATHER REGIME THROUGH THE EXTENDED PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 120 125 130 132 138 150 155 165 170 171 172.
         HEAVY FREEZING SPRAY WARNING 150 155 165 170 171.
FIRE WEATHER...NONE.

SEB MAR 08