Small Craft Advisory 187, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ANCHORAGE AK
845 PM AKST TUE MAR 4 2014

UPDATED SOUTHCENTRAL...
A TOUCH OF SE FLOW ALOFT STILL KEEPING PRECIP SHIELD AT BAY OVER THE
ANCHORAGE BOWL. HAVE TWEAKED SNOW ACCUMULATION FOR SLIGHTLY LESS
TONIGHT AND A BIT MORE FOR WED. STRONGEST LIFT STILL MAINLY OVER THE
SUSITNA VALLEY THOUGH THIS SHOULD BE MIGRATING SOUTH TO EAST
OVERNIGHT THROUGH WED MORNING.

UPDATED SOUTHCENTRAL...
HAVE UPDATED SNOW AMOUNTS FOR THE SUSITNA VALLEY THROUGH
WED...SPECIFICALLY FOR THIS EVENING AND OVERNIGHT. WHILE THE KENAI
RADAR IMAGERY REMAINS UNAVAILABLE...IR AND WV SATELLITE IMAGERY
SUGGESTING SOME DECENT MOISTURE PLUMING BECOMING LARGER IN SCOPE
ACROSS THE HEART OF THE SUSITNA VALLEY. AREA SURFACE OBSERVATION
VISIBILITIES ALSO TRENDING LOWER IN MODERATE SNOWFALL. A 500 MB JET
STREAK IS BECOMING STATIONARY OVERHEAD AS THE PARENT UPPER-LOW OVER
SW AK STALLS. THIS IS LIKELY SUPPORTING SOME STRONGER LIFT. WINTER
WEATHER ADVISORY FOR SNOW ISSUED...VALID THROUGH MID DAY WEDNESDAY.

UPDATE...JAM

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER MAINLAND ALASKA CENTERED JUST NORTH
OF MCGRATH. UPPER LEVEL HIGH PRESSURE IS OVER THE NORTHERN GULF OF
ALASKA AND OVER NORTHEAST RUSSIA...WITH A WEAK RIDGE ACROSS THE
BERING SEA CONNECTING THESE TWO HIGHS. AN NORTH PACIFIC UPPER LEVEL
LOW IS LOCATED TO THE SOUTH OF THE WESTERN ALEUTIANS.

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH 60 HOURS
(THURSDAY AFTERNOON) THEN BEGIN TO DIVERGE ON A LOW MOVING INTO THE
GULF OF ALASKA FROM THE SOUTH ON FRIDAY. THE GFS IS STRONGER AND
SLOWER WITH THIS LOW THAN THE OTHER MODELS. DUE TO LACK OF SUPPORT
FROM OTHER MODELS FOR THE GFS SOLUTION AND HIGHER CONFIDENCE IN THE
RECENT PERFORMANCE OF THE ECMWF...THE ECMWF WAS THE PREFERRED MODEL
FOR THE AFTERNOON PACKAGE.

.SHORT TERM FORECAST...
FOR SOUTH CENTRAL ALASKA...THE UPPER LOW WILL REMAIN NEARLY
STATIONARY THROUGH WEDNESDAY MORNING THEN BEGIN TO SLIDE TOWARD THE
SOUTHWEST. DYNAMICS WILL BECOME PROGRESSIVELY MORE FAVORABLE FOR
SNOWFALL THIS EVENING WITH SNOW EXPECTED OVER MUCH OF THE AREA.
SNOWFALL AMOUNTS ARE EXPECTED TO REMAIN FAIRLY MODERATE WITH THE
(RELATIVELY DRY) NORTHERLY SOURCE REGION OF THE LOW. THE LOW WILL
CONTINUE TO MOVE SOUTHWEST THROUGH THURSDAY WHEN IT WILL BE IN THE
BERING SEA. SOUTHWESTERLY FLOW ALOFT WILL CONTINUE TO KEEP CHANCES
OF SNOW THROUGH THURSDAY AFTERNOON...THEN THE HIGH PRESSURE OVER THE
GULF WILL PUSH INTO SOUTH CENTRAL ALASKA TO DRY THINGS OUT FOR
THURSDAY NIGHT AND FRIDAY.

FOR SOUTHWEST ALASKA...THE AREA NEVER REALLY GETS INTO THE
DYNAMICALLY FAVORABLE AREA OF THE LOW AND THUS WILL REMAIN FAIRLY
DRY THROUGH FRIDAY...WITH SOME LOW POPS AS THE UPPER LOW CROSSES THE
AREA AND MOVES INTO THE BERING SEA. THE EXCEPTION IS ALONG THE ALASKA
RANGE (AND POSSIBLY ALEUTIAN RANGE) WHERE UPSLOPE FLOW WILL GIVE A
BETTER CHANCE OF SQUEEZING OUT SOME SNOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 173 174 175 176 177 178 185.
         HEAVY FREEZING SPRAY 160 179 180 185.
FIRE WEATHER...NONE.

LUDWIG MAR 14