Gale Warning 1083, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
230 PM AKST FRI DEC 24 2010

.MODEL DISCUSSION...THE SYNOPTIC INITIALIZATIONS WERE REASONABLE THIS
MORNING...EVEN WITH THE TROUBLESOME LOW COMPLEX SE OF THE GULF OF
ALASKA. SYNOPTIC TRENDS ARE OVER WESTERN ALASKA/BERING SEA ARE IN
GOOD AGREEMENT. MODELS STILL STRUGGLE SOME IN THE PLACEMENT OF LOW
PRESSURE SYSTEMS IN THE GULF...HOWEVER THE MEAN TROUGH POSITIONS ARE
IN BETTER AGREEMENT. THE GFS/ECMWF APPEAR TO BE IN THE BEST AGREEMENT
AND THE MORE REASONABLE SOLUTIONS THAN THE NAM IN THE GULF AND
SOUTHCENTRAL ALASKA. THE GFS/ECMWF BRING THE SURFACE LOW PRESSURE
TROUGH MUCH FURTHER WEST THAN THE NAM IN THE SHORT TERM. THIS IS A
MORE REALISTIC SOLUTION AS ALL MODEL SOLUTIONS INDICATE THE UPPER
TROUGH BECOMING MORE NEGATIVELY TILTED WITH TIME. SO AFTERNOON
PACKAGES IN THE EAST AND WEST WILL CONTINUE TO BE INFLUENCED WITH THE
GFS MODEL.

.ANALYSIS
UPPER LEVELS...
LOW OVER SW ALASKA THIS MORNING DIGS SOUTH TO OVER THE NE PACIFIC
TONIGHT AND SAT. THE GENERAL TROUGH AXIS BECOMES RELATIVELY BROAD AND
ENCOMPASSES MUCH OF THE GULF OF ALASKA AND MAINLAND OVER THE WEEKEND.
THE TROUGH ALSO BECOMES SOMEWHAT NEGATIVELY TILTED OVER THE GULF SAT
NIGHT AND SUN. A NORTHERLY JET ON THE BACKSIDE OF THE TROUGH EXTENDS
ACROSS THE WESTERN AK PEN AND EASTERN ALEUTIANS TONIGHT AND SAT. THE
JET CORE WEAKENS SAT NIGHT/SUN AND SPREADS FURTHER WEST.

SURFACE...
DUAL 980S LOW PRESSURE SYSTEMS WHERE EVIDENT SE OF THE GULF OF
ALASKA. A SOME MOISTURE WITH SNOW SHOWERS ASSOCIATED WITH A WEAK
EASTERLY WAVE OCCURRED OVER THE NORTH CENTRAL GULF THIS MORNING.
PATCHY FOG WAS EVIDENT ACROSS THE ANCHORAGE BOWL. GUSTY GAP WINDS
CONTINUE ACROSS SOUTHCENTRAL ALASKA...ESPECIALLY ALONG THE THE NORTH
GULF COAST WHERE DEEP COLD AIR CONTINUES TO SPILL OUT OF THE COPPER
RIVER BASIN.

A WEAKENING FRONT AND TRAILING UPPER LOW PRODUCED SOME SNOW OVER THE
DELTA AND BRISTOL BAY THIS MORNING. BRISK NORTHERLY WINDS WERE
EVIDENT ACROSS MUCH OF THE AK PEN AND EASTERN ALEUTIANS. THE PINCH IN
THE PRESSURE GRADIENT BETWEEN A HIGH OVER THE BERING SEA AND A WEAK
FRONTAL SYSTEM SOUTH OF THE WESTERN ALEUTIANS PRODUCED EASTERLY GALES
ACROSS THE WESTERN ALEUTIAN ISLANDS.

.SHORT TERM FORECAST

.SOUTHCENTRAL ALASKA...
DETAILS ARE STILL A LITTLE IN DOUBT OVER THE GULF...HOWEVER THE MEAN
POSITION OF THE MAJOR FEATURES ARE MORE CERTAIN. BY SAT NIGHT AND SUN
THE MEAN POSITION OF TROUGH CURRENTLY OVER THE SE GULF SHIFTS TO THE
WESTERN GULF. THE NET RESULT WILL BE INCREASED MOISTURE INTRUSION
INTO SOUTHCENTRAL ALASKA AND WESTERN GULF. TEMPERATURES SHOULD BE
COLD ENOUGH OVER LAND AREAS FOR SNOW. HIGHER POPS WILL BE ALONG THE
COASTS AND KODIAK ISLAND AND TO A LESSER EXTENT INLAND OVER
SOUTHCENTRAL ALASKA. GAP WINDS...ESPECIALLY ACROSS THE NORTH GULF
WILL CONTINUE. MARINE ARES ACROSS THE NORTH GULF AND WESTERN GULF
WILL ALSO SEE SOME INCREASE SAT AND SUN AS PRESSURE GRADIENTS
INCREASE ACROSS THE AREA. FOG MAY BECOME A CONCERN FROM NORTHERN COOK
INLET TO THE MAT VALLEY LATE TONIGHT AND SAT AS WEAK WARM ADVECTION
ALOFT STRENGTHENS SURFACE INVERSIONS. FOG SHOULD BE LESS OF A CONCERN
ON SUN AS CLOUDS AND THE POSSIBILITY OF SNOW MOVES IN.

.SOUTHWEST ALASKA...WEAKENING FRONT AND UPPER LOW MOVE SOUTH ACROSS
THE AREA TODAY. BRISK NORTHERLY LOW AND COLD ADVECTION THEN SETS UP
OVER SOUTHWEST ALASKA THIS WEEKEND. WIND CHILL ADVISORIES ARE
EXPECTED OVER ZONES 155 AND 161. COLD AIR DAMNING WILL LIKELY KEEP
WINDS FROM REACHING THE SURFACE IN PORTIONS OF 161...HOWEVER THERE
WILL LIKELY BE AREAS WHERE WINDS WILL REACH THE SURFACE AND CAUSE
WIND CHILL ADVISORY CONDITIONS.

AK PEN...EASTERN BERING SEA...EAST ALEUTIANS...
STRONG NORTHERLY FLOW WITH SNOW SHOWERS WILL CONTINUE THROUGH THE
WEEKEND.

WESTERN AND CENTRAL ALEUTIANS...
STRONG EAST WINDS WITH FRONTAL BOUNDARY TO SOUTH WILL CONTINUE
THROUGH THE WEEKEND OVER THE WESTERN ALEUTIANS. THE CENTRAL ALEUTIANS
SHOULD NOT SEE MUCH WIND ABOVE SMALL CRAFT.

.LONG TERM FORECAST...
THE UPPER LEVEL BLOCKING PATTERN LOOKS TO BREAK DOWN EARLY NEXT WEEK
AS SEVERAL FAST-MOVING UPPER LEVEL DISTURBANCES UNDERCUT THE BLOCKING
RIDGE AND STREAM INTO THE GULF DURING THE COURSE OF THE WEEK. THE GFS
HINTS THAT A LOW PRESSURE SYSTEM COULD TRACK ACROSS THE ALEUTIANS BY
MID WEEK...BUT THIS SOLUTION IS NOT REFLECTED IN THE OTHER MODELS AT
THIS TIME.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WIND CHILL ADVISORY 155 AND 161.
MARINE...GALE WARNING...127 128 130 150 155 160 165 170 171 175 176
                        179 180 185
         HEAVY FREEZING SPRAY WARNING...121 126 127 128 129 130 140
                                        150 155 160 165 179 180 185.
FIRE WEATHER...NONE.

RMC DEC 10