Freezing Rain Advisory 2, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTH CENTRAL AND SOUTHWEST ALASKA
500 PM AST SUN DEC 3 2006

.DISCUSSION...

UPPER LEVELS...A MAJOR UPPER LOW IS CURRENTLY SITTING OVER THE
SEA OF OKHOTSK WITH A TROUGH AXIS EXTENDING EASTWARD ACROSS THE
NORTHERN BERING SEA. A SHORT-WAVE RIDGE IS SITTING OVER WESTERN
NORTH AMERICA WITH RIDGE AXIS EXTENDING FROM WASHINGTON STATE
NORTHWARD THROUGH BRITISH COLUMBIA AND THE YUKON AND ALL THE WAY
INTO THE NORTHERN HALF OF ALASKA. AN IMPRESSIVE 200 KT ZONAL JET
LIES ALONG 40N LATITUDE. THIS TYPE OF PATTERN DRIVES STORMS
EASTWARD ACROSS THE NORTH PACIFIC (SOUTH OF THE ALEUTIANS) AND
THEN NORTHWARD INTO THE GULF OF ALASKA. IT IS ALSO VERY COMMON
TO SEE A LOW TRAIN FORM OVER THE NORTH PACIFIC AS TRIPLE POINT
LOWS CONTINUALLY DEVELOP AND DEEPEN WITH UPPER SUPPORT AND COLD
AIR FEEDING INTO THEM WHILE OLDER LOWS WEAKEN. THE MODELS USUALLY
DONT HANDLE THIS PATTERN VERY WELL SO CONFIDENCE BEYOND DAY 2
IS LOW. BOTTOM LINE THOUGH IS THAT THIS IS A WARM AND WET PATTERN
FOR THE GULF COASTAL REGION.

AT THE SURFACE...THERE IS A 988 MB LOW JUST EAST OF KODIAK ISLAND
WITH OCCLUDED FRONT EXTENDING NORTHEASTWARD ACROSS THE NORTHERN
GULF. MAXIMUM GALE FORCE WINDS ALONG THE FRONT ARE SLOWLY
DIMINISHING. TIGHT PRESSURE GRADIENT IS ALSO PRODUCING GAP WINDS
ACROSS SOUTH CENTRAL INCLUDING THE MAT VALLEY/TURNAGAIN ARM/BROAD
PASS AND STRONG FLOW DOWN COOK INLET AND SHELIKOF STRAIT. ALL WINDS
WILL GRADUALLY DIMINISH TODAY AND TONIGHT AS THE SURFACE LOW WEAKENS.
LOTS OF MOISTURE IS OVERSPREADING THE SOUTHERN MAINLAND WITH SOME
DOWN SLOPING ON THE LEE SIDE OF MOUNTAINS. THE HEAVIEST SNOW HAS
FALLEN IN BRISTOL BAY WITH OVER 7 INCHES AT KING SALMON SINCE
PRECIPITATION BEGAN LAST NIGHT. LOOK FOR THIS TO CONTINUE AS THE
SURFACE LOW SITS NEAR KODIAK ISLAND FOR THE NEXT 12 TO 18 HOURS. 12
SOUNDINGS FOR ANCHORAGE AND KODIAK SHOW A SIGNIFICANT WARM-UP OVER
THE PAST 24 HOURS. THIS WARM AIR HAS TURNED PRECIPITATION TO RAIN
ALONG THE GULF COAST. IN FACT SOME TEMPS HAVE RISEN INTO THE 40S. AS
THE FRONT WEAKENS TEMPS WILL SLOWLY FALL AGAIN AND INLAND LOCATIONS
WILL ALL BE COLD ENOUGH TO SNOW.

SATELLITE IMAGERY SHOWS ANOTHER LOW OVER THE EASTERN GULF TRACKING
NORTHWESTWARD. NONE OF THE MODELS PICKED UP ON THIS LOW. FIRST PERIOD
OF FORECAST WILL BE ADJUSTED TO ACCOUNT FOR THIS LOW.

A 966 MB LOW ABOUT 450 MILES SOUTH OF THE ALEUTIANS IS TRACKING
EAST-NORTHEAST PUSHING THE OCCLUDED FRONT TOWARD THE ALEUTIANS.
STORM FORCE WINDS ALONG THE FRONT WILL GRADUALLY SPREAD NORTHWARD
TOWARD THE CENTRAL AND WESTERN ALEUTIANS.

MODELS...
GFS/AVN VERIFIES BETTER THAN NAM/ETA ON SURFACE LOW POSITIONS. ALSO
WITH A LOT OF THE ACTIVITY ON THE OUTER EDGE OF THE NAM/ETA DOMAIN
THINK GFS/AVN WILL CONTINUE TO HAVE A BETTER HANDLE ON THINGS.

FORECAST...
UPPER TROUGH FROM NORTHERN BERING TO SOUTH OF KODIAK
ISLAND WILL FALL APART AS IT LIFTS NORTHWARD THROUGH MONDAY. WITH
RIDGING TO THE NORTH KODIAK SURFACE LOW WILL REMAIN IN VICINITY
OF KODIAK ISLAND THROUGH MONDAY AS IT DISSIPATES. THIS WILL
MAINTAIN RAIN SHOWERS ALONG THE GULF COAST AND SNOW IN BRISTOL BAY.
INLAND LOCATIONS MAY SEE A FEW SHOWERS AS BANDS OF SHOWERS
ASSOCIATED WITH UPPER TROUGH MOVE ACROSS THE REGION. COLDER AIR
ALOFT WILL ADVECT ACROSS GULF TONIGHT FROM THE SOUTH SO TEMPS WILL
COOL OFF AND SOME COLDER COASTAL LOCATIONS MAY MIX WITH SNOW. THERE
WILL BE A DRYING TREND MONDAY AFTERNOON/EVENING BUT THE FRONT
ASSOCIATED WITH CURRENT LOW SOUTH OF WESTERN ALEUTIANS WILL TRACK
TOWARD GULF MONDAY NIGHT. THERE WILL BE MULTIPLE LOWS OVER THE NORTH
PACIFIC AT THIS TIME BUT AS MENTIONED EARLIER IT WILL BE DIFFICULT
TO FIGURE OUT WHICH WILL BECOME THE DOMINANT LOW. IN ANY CASE ANOTHER
ROUND OF PRECIPITATION AND WARMER TEMPS WILL BE IN STORE FOR THE
SOUTHERN MAINLAND EARLY TO MID WEEK. COASTAL LOCATION WILL PICK UP
SIGNIFICANT PRECIPITATION AND INLAND LOCATIONS WILL LIKELY SEE
LITTLE.

OUT WEST...ALEUTIANS AK PEN SOUTHERN BERING WILL SEE LOTS OF WINDS
AND RAIN AS STRONG FRONT MOVES OVERHEAD TONIGHT THROUGH TUESDAY. AS
SYSTEMS MOVE NORTHWARD TOWARD THE MAINLAND COLD AIR WILL BE PULLED
DOWN ACROSS THE BERING REGION MID TO LATE WEEK SO LOOK FOR A
SHOWERY AND GUSTY PATTERN TO DEVELOP.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 191. HIGH WIND WARNING 187.
MARINE...STORM 172 175. GALE 120 121 132 150 155 170 171 176 179 185
350 410.

SEB DEC 06