Gale Warning 748, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKST SAT NOV 22 2008

.ANALYSIS AND UPPER LEVELS...
THE VERY ACTIVE PATTERN CONTINUES ACROSS ALASKA TODAY. A LARGE COLD
CORE UPPER LOW REMAINS ANCHORED OVER THE LOWER YUKON VALLEY WITH
MULTIPLE SHORTWAVES ROTATING AROUND ITS PERIPHERY. THE TWO MOST
SIGNIFICANT SHORTWAVES ARE LOCATED IN THE NORTHERN GULF AND A SECOND
MUCH STRONGER ONE CROSSING THE ALASKA PENINSULA NEAR COLD BAY.
ANOTHER LOW OVER THE WESTERN ALEUTIANS IS RAPIDLY DEVELOPING THIS
AFTERNOON AS IT CROSSES INTO THE CENTRAL BERING SEA.

AT THE SURFACE...A POTENT 989 MB LOW JUST WEST OF MIDDLETON ISLAND IS
RAPIDLY MOVING INTO WESTERN PRINCE WILLIAM SOUND. A BARRIER JET
FORMED ALONG THE COAST WITH WINDS GUSTING TO 45 KTS. HIGH PRESSURE AT
THE SURFACE DOMINATES THE SOUTHWEST INTERIOR WITH CLEAR AND COLD
CONDITIONS PERSISTING. FURTHER WEST...AN OCCLUDED FRONT ASSOCIATED
WITH THE RAPIDLY DEVELOPING LOW OVER THE WESTERN ALEUTIANS IS
APPROACHING ADAK EARLY THIS AFTERNOON.

.MODEL DISCUSSION...
AGAIN...MODELS DID NOT INITIALIZE WELL ON THE 12Z RUN AND QUICKLY
DIVERGE ON SOLUTIONS AT 48 HOURS. EVEN THOUGH THERE IS AGREEMENT
BETWEEN THE MODELS IN THE THE FIRST 48 HOURS...THE RUN TO RUN
CONSISTENCY IS VERY POOR. WITH SUCH AN ACTIVE WEATHER PATTERN ACROSS
OUR DOMAIN AND LOW CONFIDENCE IN THE MODEL SOLUTIONS...DECIDED TO
FOCUS ON THE SHORT TERM FORECAST AND MAKE VERY LITTLE CHANGES BEYOND
MONDAY.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
THE AFOREMENTIONED LOW HEADING TOWARD WESTERN PRINCE WILLIAM SOUND IS
MAKING FOR A CHALLENGING FORECAST THIS EVENING ACROSS SOUTHCENTRAL.
SO FAR...SNOWFALL AMOUNTS HAVE BEEN IN LINE WITH OUR THINKING ACROSS
MOST OF SOUTHCENTRAL. THE EXCEPTION IS THE SUSITNA VALLEY WHERE
REPORTS ARE COMING IN OF 2 TO 4 INCHES. THE UPSLOPE COMPONENT AND
WEAK OVERRIDING MOISTURE COUPLED WITH LOW DENSITY SNOW IS THE LIKELY
CAUSE OF THE HIGHER AMOUNTS. OVERALL THE SNOWFALL AMOUNTS HAVE BEEN
LIGHT AS A RESULT OF THE LACK OF UPPER LEVEL SUPPORT. AFTER A BRIEF
BREAK LATER THIS EVENING AS THE LOW MOVES INLAND...THE NEXT SHORTWAVE
AND WEAK SURFACE LOW WILL MOVE TOWARD THE SOUTHERN TIP OF THE KENAI
PENINSULA EARLY SUNDAY MORNING. SNOW WILL BEGIN FALLING AGAIN FROM
KACHEMAK BAY TO THE NORTHERN SUSITNA VALLEY BY MID MORNING. THIS NEXT
WAVE HAS A BIT MORE ENERGY ASSOCIATED WITH IT SO THE POTENTIAL FOR
GREATER SNOW AMOUNTS IS POSSIBLE ALONG THIS CORRIDOR. WINDS ALOFT
WILL REMAIN SOUTH TO SOUTHWESTERLY SO THERE WILL BE LITTLE IF ANY
DOWNSLOPE COMPONENT AS THE SNOW BEGINS TO FALL IN THE MORNING.

WHILE THE MODELS DISAGREE ON HOW THIS NEXT FEATURE ARRIVES IN THE
GULF...A STRONG FRONTAL BOUNDARY ASSOCIATED WITH A 970 MB LOW IN
BRISTOL BAY WILL MOVE ACROSS KODIAK ISLAND LATE SUNDAY AND TOWARD THE
NORTHERN GULF MONDAY MORNING. THE PRESSURE GRADIENT ALONG THIS
BOUNDARY WILL BE STRONG ENOUGH TO POTENTIALLY LEAD TO A HIGH WIND
WATCH/WARNING FOR PORTAGE VALLEY AND/OR TURNAGAIN ARM ON MONDAY. THE
STRONG SOUTHEASTERLY WINDS AHEAD OF THE FRONT WILL KEEP THE ANCHORAGE
BOWL DRY FOR THIS SYSTEM OUTSIDE OF A FEW FLURRIES.

SOUTHWEST ALASKA...
THE COLD UPPER LEVEL LOW AND CLEAR SKIES ARE ALLOWING TEMPERATURES TO
REMAIN WELL BELOW NORMAL THROUGHOUT THE SOUTHWEST INTERIOR. BETHEL
BROKE A RECORD LOW FOR THE FOURTH STRAIGHT DAY AND MCGRATH WILL
LIKELY BREAK A RECORD MIN HIGH TODAY AS TEMPERATURES FAILED TO GET
WARMER THAN -25 F. THE COLD CORE LOW WILL BEGIN TO FINALLY RETREAT
NORTH AND EAST AHEAD OF A STRONG FRONTAL BOUNDARY LATE SUNDAY NIGHT.
TEMPERATURES WILL REBOUND BACK TOWARD CLIMATOLOGICAL NORMS. AS THIS
FRONT APPROACHES...SNOW WILL SPREAD INLAND POSSIBLY MIXING WITH RAIN
OR FREEZING RAIN IN THE BRISTOL BAY ZONE. THERE IS AN OUTSIDE CHANCE
OF SOME LOCAL BLIZZARD CONDITIONS ALONG THE COAST BEGINNING SUNDAY
EVENING.

BERING SEA ALEUTIANS...
SEVERAL SYSTEMS ARE RESULTING IN ANOTHER CHALLENGING FORECAST OUT
WEST. A VERY POTENT LOW MOVED ACROSS THE ALASKA PENINSULA EARLIER
THIS AFTERNOON. ON THE BACK SIDE OF THIS LOW THERE WERE VERY STRONG
PRESSURE RISES AND SUBSIDENCE WHICH RESULTED IN NEAR HIGH WIND
WARNING CRITERIA AT DUTCH HARBOR. NORTHWESTERLY WINDS WILL REMAIN
GUSTY...ESPECIALLY THROUGH CHANNELED TERRAIN FOR THE NEXT SEVERAL
HOURS. THE STENGTHENING SYSTEM FURTHER WEST WILL BRING STORM FORCE
WINDS BACK TO MOST OF THE OFFSHORE WATERS BY SUNDAY AFTERNOON.

AT THIS TIME...WILL LIKELY ISSUE A BLIZZARD WARNING FOR THE PRIBILOF
ISLANDS BEGINNING AROUND MIDNIGHT. THERE IS ABUNDANT MOISTURE
ASSOCIATED WITH THIS FRONTAL BOUNDARY AND TEMPERATURES SHOULD REMAIN
JUST BELOW FREEZING AT ST PAUL...COUPLED WITH GALE FORCE WINDS...WILL
LIKELY RESULT IN 6 TO 12 HOURS OF BLIZZARD CONDITIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 195.
MARINE...STORM WARNING...172 175.
         GALE WARNING...125 130 132 150 155 160 165 170 171 172 175
            176 179 180 185.
         HEAVY FREEZING SPRAY...180 185.
FIRE WEATHER...NONE.

AB NOV 08