Freezing Rain Advisory 3, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SUN JAN 5 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS A LARGE UPPER LEVEL "STEERING" LOW SOUTH OF THE WESTERN
ALEUTIANS WITH A "LOBE" EXTENDING INTO THE BERING SEA THEN SOUTHEAST
ACROSS THE ALASKA PENINSULA INTO THE WESTERN GULF OF ALASKA. THERE
IS AN UPPER LEVEL BLOCKING RIDGE ALONG THE WEST COAST OF NORTH
AMERICA EXTENDING INTO THE YUKON. BETWEEN THE HIGH AND LOW IS MOIST
SOUTHERLY FLOW WITH A VERY LONG FETCH INTO THE SUBTROPICS. THERE ARE
A SERIES OF WEAK SHORT-WAVE TROUGHS ALONG THE UPPER LOW "LOBE"
MOVING INTO/TOWARD SOUTHERN ALASKA.

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE ONLY IN FAIR AGREEMENT TODAY. THE MAIN
DIFFERENCES EARLY ON INVOLVE THE LOCATION/TIMING OF SURFACE LOWS AND
THE WEAK UPPER TROUGHS IN THE SOUTHERLY FLOW. BEYOND ABOUT 48 HOURS
INTO THE FORECAST THE MODELS BEGIN TO DIVERGE SIGNIFICANTLY ON THE
LOCATION AND STRENGTH OF A DEVELOPING LOW OVER THE SOUTHERN/WESTERN
GULF. THE GFS...UKMET...AND GEM GLOBAL ARE STRONGER AND FURTHER
EAST/SLOWER WITH THIS LOW THAN THE ECMWF AND NAM. CONFIDENCE WITH
THE FORECAST FOR THIS SYSTEM IS THEREFORE LOW. AFTERNOON FORECASTS
LEAN TOWARD THE ECMWF SOLUTION FOR CONTINUITY REASONS. THE
EXPECTATION IS THAT THE FORECAST FOR THIS FEATURE WILL CHANGE OVER
THE NEXT COUPLE OF FORECAST PACKAGES AS THE MODELS (HOPEFULLY) GET A
BETTER GRASP ON THE SITUATION.

.SHORT TERM FORECAST...
MOIST SOUTHERLY FLOW ALOFT WILL CONTINUE OVER SOUTHERN ALASKA INTO
TUESDAY. A SERIES OF WEAK UPPER TROUGHS WILL PERIODICALLY ENHANCE
CHANCES FOR PRECIPITATION. A MIXTURE OF PRECIPITATION TYPES ARE
EXPECTED WITH RAIN...SNOW...SNOW/ICE PELLETS EXPECTED...AND EVEN
SOME FREEZING RAIN POSSIBLE (OVER THE KUSKOKWIM VALLEY AND DELTA
THIS EVENING). NONE OF THE SYSTEMS IS PARTICULARLY STRONG BY ALASKA
STANDARDS FOR WIND OR PRECIPITATION.

ON TUESDAY THE DEVELOPMENT OF THE A LOW IN THE GULF WILL BRING SOME
RIDGING INTO SOUTHERN ALASKA...BASICALLY AN EXTENSION OF THE NORTH
AMERICAN WEST COAST RIDGE. THE STRENGTH AND ORIENTATION OF THIS
RIDGE ARE STILL BIG QUESTION MARKS DUE TO THE MODEL UNCERTAINTY WITH
THE LOW (ADDRESSED ABOVE). BUT THERE SHOULD BE A BREAK IN THE
WEATHER AT SOME POINT...WITH A DRYING TREND ON TUESDAY THAT MAY (OR
MAY NOT) LAST INTO WEDNESDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 132 150 155 160 172 174 178 180 185.
         HEAVY FREEZING SPRAY 185.
FIRE WEATHER...NONE.

LUDWIG JAN 14