Brisk Wind Advisory 11, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
220 PM AKST THU JAN 31 2013

.ANALYSIS AND UPPER LEVELS...THERE IS A RATHER COMPLEX PATTERN IN THE
UPPER LEVEL FLOW OVER THE STATE TODAY. THERE ARE TWO LONG WAVE
FEATURES. THE FIRST IS A RIDGE RUNNING JUST OFF THE WEST COAST OF
NORTH AMERICA THAT BENDS NORTHWEST OVER THE GULF OF ALASKA AND
TERMINATES IN THE BRISTOL BAY REGION. THE SECOND IS A LONG WAVE
TROUGH EXTENDING OUT OF RUSSIA AND INTO THE WESTERN BERING SEA WHERE
A CUT OFF LOW HAS DEVELOPED. THERE IS A SECONDARY UPPER LEVEL LOW
SOUTH OF THE EASTERN ALEUTIANS THAT IS HELPING TO STEER THE MAIN JET
STREAM SOUTH OF THE REGION. THE RESULT IS BROAD SOUTHERLY FLOW OVER
THE BERING SEA REGION AND SOUTHERN GULF THAT TURNS ANTI-CYCLONIC TO
THE WEST-SOUTHWEST OVER THE MAINLAND PART OF THE STATE.
THE SURFACE MAP SHOWS A LOW SOUTH OF THE ALASKA PENINSULA WITH A
FRONT REACHING INTO THE SOUTHERN GULF OF ALASKA AND BENDING WESTWARD
OVER THE ALASKA PENINSULA AND EASTERN ALEUTIANS. ANOTHER NORTH
PACIFIC LOW IS MOVING SLOWLY NORTHWARD TOWARD KISKA. THE MAIN RIDGE
IS WELL OUT INTO THE ARCTIC OCEAN BUT THE ARCTIC FRONT HAS BEEN
PUSHED NORTHWARD KEEPING THE PRESSURE GRADIENT IN NORTHERN ALASKA.
THIS HAS LEFT SOUTHWEST AND SOUTH CENTRAL ALASKA UNDER RELATIVELY
WEAK FLOW AT THE SURFACE.

.MODEL DISCUSSION...MODELS ARE CONSISTENT THROUGH THE NEXT DAY BUT
THEN DIVERGE RAPIDLY BY FRIDAY NIGHT IN REGARDS TO THE LARGE LOW
MOVING OUT OF THE NORTH PACIFIC TOWARD THE CENTRAL ALEUTIAN ISLANDS.
BY SATURDAY NIGHT THERE IS A 500 MILE DIFFERENCE BETWEEN THE NAM
LOCATION AND THE ECMWF LOCATION. THE GFS IS SITTING RIGHT BETWEEN THE
OTHER SOLUTIONS AND THAT IS PART OF THE REASON THE GFS IS THE FAVORED
MODEL. THE ECMWF AND GFS THEN CONVERGE A BIT ON THEIR SOLUTIONS AFTER
THAT AND FOLLOW A SIMILAR SOLUTION INTO THE MIDDLE OF NEXT WEEK. THE
NAM MODEL IS THE ONE THAT IS STRUGGLING THE MOST ESPECIALLY IN THE
BERING SEA AND ALEUTIAN ISLAND AREAS.

.SHORT TERM FORECAST...A SERIES OF UPPER LEVEL WAVES HAS BEEN MOVING
FROM WEST TO EAST ACROSS SOUTH CENTRAL ALASKA TODAY BRINGING SOME
SNOW TO THE REGION. AS THE FINAL WAVE MOVED THROUGH THE COOK INLET
REGION THE WEAK RIDGE MOVING INTO THE AREA BEHIND IT TRAPPED THE LOW
LEVEL MOISTURE IN A STABLE LAYER AND HAS PRODUCED WIDESPREAD LOW
CLOUDS AND FOG. THIS FOG AND STRATUS WILL LIKELY PERSIST INTO
TOMORROW DUE TO THE LACK OF WINDS AT THE SURFACE AND THE STABLE LAYER
KEEPING ANY VERTICAL MIXING FROM DISSIPATING IT. CLOUD CEILINGS
SHOULD LIFT TOMORROW AS A FRONT APPROACHING THE NORTH GULF COAST
INCREASES THE SURFACE GRADIENT AND PULLS DRIER AIR FROM THE INTERIOR
OF THE STATE INTO THE REGION.
SOUTHWEST ALASKA IS IN A SIMILAR SITUATION AS SOUTH CENTRAL AS THE
RIDGE HAS TRAPPED THE MOIST AIR IN A STABLE LAYER PRODUCING
WIDESPREAD FOG. THIS FOG WILL PERSIST THROUGH THE NIGHT IN THE
BRISTOL BAY REGION. THE KUSKOKWIM DELTA WILL LIKELY SEE FOG LESSENING
OVERNIGHT AND NORTH TO NORTHEAST WINDS MOVE INTO THE AREA.

.LONG TERM FORECAST...SOUTHERLY FLOW ALOFT WILL KEEP MILD
TEMPERATURES OVER MOST OF SOUTHERN ALASKA THIS WEEKEND THROUGH EARLY
NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...DENSE FOG ADVISORY 101 111 121 145.
MARINE...GALE 130 132 150 155 170 172 175 176.
         HEAVY FREEZING SPRAY 179.
FIRE WEATHER...NONE.

JAN 13

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST THU JAN 31 2013

AKZ101-111-010105-