Small Craft Advisory 214, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST FRI MAR 8 2013

.ANALYSIS AND UPPER LEVELS...THE POWERFUL LOW IN THE BERING SEA HAS
ELONGATED AS IT WEAKENS AND MOVES NORTHWARD. IT HAS DEVELOPED A
SECONDARY CENTER WITH THE STRONGER ONE NEAR THE BERING STRAIT AND
MOVING NORTHWARD AND A WEAKER ONE IN BRISTOL BAY...WHICH WILL MOVE
INTO THE NORTHERN GULF OF ALASKA TOMORROW.
THERE IS STILL A STRONG PRESSURE GRADIENT AROUND THE LOW IN BRISTOL
BAY. THIS LOW IS NOT MOVING MUCH AND WILL NEED TO BE WATCHED TO SEE
IF IT MOVES EASTWARD AS SOON AS THE MODELS PROJECT. THERE IS A GOOD
AROUND OF COLD AIR FEEDING INTO THE LOW FROM THE NORTHWEST AND THE
LOW MAY BE DELAYED IN ITS EASTWARD PROGRESSION DUE TO THIS.
AT THE UPPER LEVELS THERE IS STILL A GOOD AMOUNT OF DUE SOUTH FLOW
OVER SOUTH CENTRAL ALASKA WITH STILL WESTERLY FLOW IN THE WESTERN
BERING SEA. THE UPPER LEVEL LOW IS CENTERED OVER EASTERN RUSSIA WITH
THE TROUGH EXTENDING OVER MOST OF THE BERING SEA AND THEN OVER THE
ALASKA PENINSULA.

.MODEL DISCUSSION...MODELS HAVE A GOOD LOCK ON THE SYNOPTIC PATTERN
AND THERE IS LITTLE DIFFERENCE IN SOLUTIONS THROUGH MONDAY. THERE ARE
SOME SMALLER SCALE FEATURES THAT ARE DIFFERENT IN THE MODELS THAT
WILL HAVE SOME BERING ON THE FORECAST HOWEVER. THE FIRST IS THE
SECONDARY LOW IN BRISTOL BAY THIS AFTERNOON. THAT LOW IS BEST
RESOLVED BY THE NAM AND WHILE ALL MODELS MOVE IT INTO THE GULF
TOMORROW THE MORE NORTHERLY NAM SOLUTION APPEARS TO BE THE BEST ONE.
THE ECMWF IS LIKELY TOO FAR SOUTH WHILE THE GFS IS SMOOTHING OUT THE
DETAIL TOO MUCH. THE BIGGER ISSUE IS THE DETAILS WITH UN UPPER LEVEL
DISTURBANCE AND SURFACE LOW DEVELOPING AROUND COOK INLET ON SUNDAY.
THE GFS IS SHOWING A LIGHT DUSTING OF SNOW AROUND THE AREA WHILE THE
NAM SOLUTION WOULD LEAD TO A FEW INCHES OF ACCUMULATION OVER MOST OF
THE COOK INLET REGION INCLUDING ANCHORAGE AND THE MAT-SU. A
SIGNIFICANT DIFFERENCE IS THE WAY THE NAM DEVELOPS A WEAK SURFACE LOW
IN THE INLET AND THE GFS CONSOLIDATES THE PATTER INTO ONE LOW OVER
THE EASTERN KENAI PENINSULA. THE COLD ADVECTION PATTERN WOULD FAVOR
THE NAM SOLUTION OVER THE GFS. THE ECMWF OS OVERALL CLOSER TO THE NAM
SOLUTION BUT LACKS THE DETAIL DUE TO RESOLUTION.

.SHORT TERM FORECAST...THE MOST HAZARDOUS WEATHER IS AROUND THE
ALASKA PENINSULA WHERE THERE HAVE BEEN BLIZZARD CONDITIONS MOST OF
TEH DAY. FALSE PASS, COLD BAY, AND KING COVE HAVE BEEN GUSTING IN THE
50 TO 65 MPH RANGE IN WHITEOUT CONDITIONS IN THE COLD AIR ADVECTION
AROUND THE LOW IN BRISTOL BAY. THESE CONDITIONS WILL SLOWLY IMPROVE
THIS EVENING AS THE LOW WEAKENS AND DRIFTS EASTWARD. AS MENTIONED
EARLIER THIS LOW COULD BE SLOWER THAN EXPECTED IN ITS EASTWARD
MOVEMENT AND ITS PROGRESS SHOULD BE WATCHED THIS EVENING AND
OVERNIGHT FOR PERSONS IMPACTED BY THIS STORM.
THE BRISTOL BAY REGION FROM PORT HEIDEN TO NAKNEK WILL SEE SOME SNOW
AND BLOWING OR DRIFTING SNOW AS THIS LOW MOVES EASTWARD. HOWEVER IT
WILL BE WEAKENING SO BLIZZARD CONDITIONS ARE NOT EXPECTED EXCEPT FOR
WHERE THEY ARE OCCURRING THIS AFTERNOON.
THE AREA OF BRISTOL BAY WEST OF NAKNEK AND NORTHWARD TOWARD BETHEL
WILL SEE SNOWFALL AS THE FRONTAL ZONE EAST OF THE LOW IN BRISTOL BAY
AND THE ONE NEAR THE BERING STRAIT WILL KEEP MOISTURE AND LIFTING
OVER THE AREA. THIS SNOW WILL END FROM WEST TO EAST OVERNIGHT IN THE
KUSKOKWIM DELTA BUT WILL LINGER INTO SATURDAY FOR THE BRISTOL BAY
ZONE.
THERE IS A WEAKENING FRONT ALONG THE NORTH GULF COAST THAT HAS
BROUGHT RAIN AND SNOW TO THE NORTH GULF COAST TODAY. THIS WILL MOVE
EASTWARD OVERNIGHT BUT THERE IS A QUESTION ABOUT HOW LONG THE
PRECIPITATION WILL LINGER FROM EASTERN PRINCE WILLIAM SOUND AND
EASTWARD. WHILE THE BEST DYNAMIC LIFT WILL MOVE OUT OF THE ARE WITH
THE FRONT THE OROGRAPHIC LIFT FROM THE MOUNTAINS MAY KEEP
PRECIPITATION AROUND MOST OF THE NIGHT...ESPECIALLY IN VALDEZ THROUGH
THOMPSON PASS. SNOW WILL INCREASE AGAIN ALONG THE NORTH GULF COAST
TOMORROW AS THE LOW IN BRISTOL BAY MOVE INTO THE AREA.
GUSTY SOUTHEAST WINDS THOUGH TURNAGAIN ARM AND THE KNIK RIVER VALLEY
WILL DIMINISH BY MORNING AS THE PRESSURE GRADIENT DECREASES OVER
SOUTH CENTRAL ALASKA.

.LONG TERM FORECAST...THE MODELS CONTINUE TO BE IN VERY GOOD
AGREEMENT IN THE LONG TERM WITH THE DEVELOPMENT OF A LARGE SCALE
RIDGE EARLY NEXT WEEK FROM THE EASTERN BERING SEA INTO THE NORTHERN
INTERIOR. THIS SETUP WILL BRING CLEARING SKIES AND BELOW NORMAL
TEMPERATURES TO MUCH THE STATE AS AN ARCTIC HIGH DESCENDS INTO THE
EASTERN INTERIOR. THIS PATTERN WILL LIKELY HOLD THROUGH THE MAJORITY
OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING 181.
MARINE...GALE 175 176 180. STORM 179.
         HEAVY FREEZING SPRAY 160 179.
FIRE WEATHER...NONE.

MAR 13