Brisk Wind Advisory 2, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
100 PM AKST TUE JAN 12 2010

.ANALYSIS AND UPPER LEVELS...LONG-WAVE TROUGH IS WELL ENTRENCHED
ACROSS THE REGION. THE SUBTROPICAL JET EXITS OUT OF CHINA AND
CURVES NORTHWARD TO JUST SOUTH OF KAMCHATKA BEFORE DIVING
SOUTHEASTWARD DOWN TO THE TROPICS AT AROUND 25 DEGREES NORTH
WHERE IT REMAINS FOR THE REST OF THE WAY ACROSS THE PACIFIC.
THE AMPLIFICATION OVER THE NORTHWEST PACIFIC HAS AIDED IN
DEVELOPMENT OF A STORM...WHICH WILL RAPIDLY INTENSIFY AS IT
TRACKS TOWARD THE ALEUTIANS THE NEXT COUPLE DAYS. AN UPPER
LOW EMBEDDED IN DEEP SHORT-WAVE TROUGH OVER MAINLAND ALASKA
IS DROPPING SOUTHWARD ACROSS KODIAK THIS MORNING...DRAGGING A
LITTLE BIT OF ARCTIC AIR ALONG WITH IT. UPPER WAVES ROTATING
AROUND THIS LOW AND ACROSS SOUTHCENTRAL ARE PRODUCING AREAS OF
SNOW AND RAIN...PRIMARILY ALONG THE COAST RIGHT NOW. STRONG WINDS
CONTINUE THROUGH THE GAPS...BUT ARE TRENDING DOWNWARD AS LOW LEVEL
NORTHEASTERLY FLOW BEGINS TO WEAKEN AND SHIFT TOWARD THE EAST AND
EVENTUALLY TOWARD THE SOUTH...ADVECTING WARMER GULF AIR BACK
ONSHORE. BLOCKING HIGH REMAINS OVER THE BERING SEA...ALTHOUGH AN
ARCTIC LOW/TROUGH DROPPING THROUGH THE CHUKCHI SEA IS BEGINNING
TO PUSH THE RIDGE SOUTHWARD.

.MODEL DISCUSSION...MODEL SOLUTIONS DIFFER ON EXACT POSITIONS
AND STRENGTHS OF THE LOW CENTERS...BUT ARE ALL GROUPED IN THE
SAME GENERAL AREA. THE ONE SIGNIFICANT MODEL DIFFERENCE IN THE
SHORT-TERM IS THE GFS SOLUTION OF DEEPENING A TRIPLE POINT LOW
AND TRACKING IT ACROSS THE SOUTHERN AKPENN LATE FRIDAY. NONE OF
THE OTHER MODELS ARE EVEN CLOSE TO WHAT THE GFS SHOWS AND THE
GFS ENSEMBLE MEMBERS DO NOT SUPPORT SUCH A STRONG FEATURE.
THEREFORE...WILL IGNORE THIS GFS SOLUTION AND STICK CLOSE TO
INHERITED FORECAST WHICH IS IN LINE WITH OTHER SOLUTIONS.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...WINDS ACROSS THE REGION WILL DROP OFF
SIGNIFICANTLY ACROSS MOST OF THE REGION LATE THIS AFTERNOON
THROUGH TONIGHT AS THE SURFACE PRESSURE GRADIENT WEAKENS AND
LOW LEVEL THERMAL ADVECTION BECOMES NEUTRAL TO WARM. THE
EXCEPTION TO THIS WOULD BE DIRECTLY IN THE OUTFLOW REGION OF
THE MORE SIGNIFICANT COASTAL RANGE GAPS (THOMPSON PASS/COPPER
RIVER DELTA) WHERE GUSTY WINDS WILL HANG ON A LITTLE
LONGER...PRIMARILY DUE TO THE LARGE DIFFERENCE IN TEMPERATURES
FROM INLAND TO THE COAST. WEAK UPPER WAVES AS WELL AS SOME
OVERUNNING WILL PRODUCE AREAS OF SNOW (AND RAIN ALONG THE
IMMEDIATE COAST). THE BULK OF THIS WILL FALL FROM THE NORTH GULF
COAST TO THE COPPER BASIN WITH JUST A CHANCE ELSEWHERE. MODELS
INDICATE ONE FINAL WAVE SPINNING OFF THE UPPER LOW WILL MOVE ACROSS
THURSDAY BRINGING A CHANCE OF SNOW TO THE MORE WESTERN AREAS...BUT
CONFIDENCE IN THE TRACK OF THIS FEATURE IS FAIRLY LOW AT THIS
POINT.

SOUTHWEST ALASKA...AS THE UPPER LOW OVER KODIAK CONTINUES TO DROP
SOUTHWARD INTO THE NORTH PACIFIC TONIGHT WEAK COLD ADVECTION WILL
PERSIST ACROSS SOUTHWEST ALASKA AND THE FAR EASTERN
BERING...RESULTING IN CONTINUED GUSTY WINDS ACROSS THE REGION.
WINDS WILL THEN DIMINISH WEDNESDAY AND WEDNESDAY NIGHT AS THE
THERMAL ADVECTION BECOMES NEUTRAL AND SURFACE PRESSURE GRADIENT
SLACKENS A BIT. HOWEVER...GRADIENT WILL BEGIN TO TIGHTEN BACK UP
WEDNESDAY NIGHT AND THURSDAY AS THE ALEUTIAN SYSTEM BEGINS TO
INFLUENCE THE WEATHER IN SOUTHWEST ALASKA.

BERING SEA/ALEUTIANS...THE NORTHWEST PACIFIC LOW WILL RAPIDLY
DEEPEN TONIGHT AND WEDNESDAY IN AN AREA OF STRONG UPPER LEVEL
DIVERGENCE...WITH MODELS INDICATING THE SURFACE PRESSURE
DROPPING DOWN INTO THE 940S WEDNESDAY AFTERNOON. THIS SYSTEM WILL
PUSH A STORM FORCE FRONT NORTH AND EASTWARD ACROSS THE ALEUTIANS
LATE WEDNESDAY THROUGH THURSDAY AS UPPER RIDGE CURRENTLY IN PLACE
RAPIDLY WEAKENS DUE TO PRESSURE FROM ALL SIDES. THIS WILL EVOLVE
INTO A LARGE LOW VORTEX ALONG THE ALEUTIANS BY WEEK'S END...WITH
MULTIPLE LOWS ROTATING AROUND THE MAIN CENTER. FORECASTING THE
DETAILS OF THESE LOWS IS NOT USUALLY HANDLED WELL BY THE MODELS...SO
CONFIDENCE FALLS OFF SIGNIFICANTLY AT WEEK'S END.

.LONG TERM FORECAST...MODELS INDICATE A SHORT-WAVE MOVING AROUND
THE SOUTHERN EDGE OF THE ALEUTIAN LOW WILL DEVELOP A STRONG LOW
AND MOVE IT INTO THE GULF THIS WEEKEND...BUT RUN-TO-RUN CONSISTENCY
ON THE TRACK IS NOT GREAT...BUT THERE IS GOOD POTENTIAL FOR A STORM
TO AFFECT SOUTHCENTRAL. THE ORIGINAL LOW ALONG THE ALEUTIANS WILL
SHIFT EASTWARD WITH TIME WITH WIDESPREAD COLD ADVECTION ENSUING
ACROSS THE BERING SEA...RESULTING IN THE USUAL GUSTY WINDS AND
SNOW SHOWERS. IT LOOKS LIKE THIS PATTERN WILL HOLD ACROSS THE
BERING THROUGH THE MIDDLE OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...172 175 176.
         GALE WARNING...127 128 180.
         HEAVY FREEZING SPRAY...127 128 140 141 160 165 185.
FIRE WEATHER...NONE.

SEB JAN 10