Brisk Wind Advisory 9, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
1230 PM AKST MON FEB 1 2010

.ANALYSIS AND UPPER LEVELS...A HIGH AMPLITUDE LOW WAVELENGTH
BLOCKING RIDGE EXTENDS FROM THE GULF OF ALASKA NORTHWESTWARD TO
SIBERIA. AN ARCTIC SHORT-WAVE TROUGH IS DROPPING DOWN THE EASTERN
SIDE OF THIS RIDGE ACROSS INTERIOR ALASKA TOWARD THE YUKON. VISIBLE
SATELLITE IMAGERY SHOWS MID LEVEL CLOUD DECK...WHICH SETTLED IN
OVER SOUTHCENTRAL THIS MORNING STARTING TO ERODE OVER THE NORTHERN
SUSITNA AND COPPER BASIN AS NORTHWEST FLOW ASSOCIATED WITH THIS
SHORT-WAVE INCREASES. THERE ARE ALSO SOME SHOWERS FALLING ACROSS
THE REGION...BUT THESE TOO SHALL DIMINISH ALONG WITH THE CLOUD
COVER AS WE HEAD THROUGH TODAY AND TONIGHT. WEST OF THE RIDGE...A
VERTICALLY STACKED LOW AND ASSOCIATED TROUGH ARE LIFTING OFF THE
NORTH-NORTHWEST WHILE THE REMNANTS OF AN OCCLUDED FRONT PUSH TOWARD
THE SOUTHWEST ALASKA COAST. WITH THE PARENT LOW MOVING THE OPPOSITE
DIRECTION THE REMNANTS OF THE FRONT CONTINUE TO STRETCH APART AND
WEAKEN FURTHER...SO THE CHALLENGE FOR THE DAY IS FIGURING OUT HOW
FAR NORTH AND EAST THE PRECIP WILL MAKE IT.

.MODEL DISCUSSION...MODELS ARE IN GOOD AGREEMENT THROUGH THE NEXT
FEW DAYS. THE LARGEST DIFFERENCES LIE WITH THE SYSTEMS OUT ALONG
THE ALEUTIANS...BUT THEY ARE NOT LARGE ENOUGH TO SIGNIFICANTLY
AFFECT THE FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...DRIER AIR WILL CONTINUE TO ADVECT SOUTHWARD
ACROSS SOUTHCENTRAL TONIGHT BEHIND THE UPPER LEVEL
SHORT-WAVE...LEADING TO CLEARING SKIES. THERE WILL BE A LITTLE
BIT OF WIND ALONG THE ALASKA RANGE AS COLDER AIR FILTERS THROUGH
THE GAPS...BUT FURTHER SOUTH WINDS WILL BE LIGHT OR CALM....AND
A SURFACE-BASED INVERSION IS CURRENTLY IN PLACE (AS PER THE 12Z
ANCHORAGE SOUNDING). THEREFORE...EXPECT AREAS OF FOG TO
FORM...ESPECIALLY IN THE MOISTER ENVIRONS OF COOK INLET AND
PRINCE WILLIAM SOUND. MEANWHILE...THE REMNANTS OF A FRONT MOVING
ALONG THE SOUTHERN ALASKA PENINSULA WILL MOVE TO KODIAK ISLAND
TONIGHT...SO RAIN AND FOG WILL CONTINUE. AS WE HEAD THROUGH THE
NEXT FEW DAYS THE NARROW UPPER RIDGE WILL BE PUSHED OFF TO THE
SOUTH AND WEST AS AN ARCTIC SHORT-WAVE DROPS SOUTHWARD ACROSS
THE STATE. THIS WILL RESULT IN A TIGHTENING PRESSURE GRADIENT AND
COLD ADVECTION...THUS CAUSING GUSTY GAP WINDS THROUGH THE ALASKA
RANGE AND COASTAL RANGE. HOWEVER...DON'T EXPECT THIS TO BE A MAJOR
EVENT DUE TO A LACK OF UPPER LEVEL SUPPORT. THE UPPER TROUGH WILL
DIG TOWARD SOUTHWEST ALASKA...SO THAT UPPER FLOW WILL BACK TO THE
WEST MID WEEK AND EVENTUALLY SOUTH BY THE END OF THE WEEK. WILL
HAVE TO WATCH FOR PLACEMENT OF LOW FORMATION OUT AHEAD OF THIS
AMPLIFYING TROUGH...WHICH WILL DETERMINE WHICH AREAS WILL SEE
SOME SNOW OUT OF THIS.

SOUTHWEST ALASKA...REMNANTS OF OCCLUDED FRONT WILL MOVE TO THE
IMMEDIATE SOUTHWEST COAST TONIGHT AND STALL DO TO RIDGING INLAND.
ANY PRECIP THAT DOES MAKE IT ONSHORE WILL BE LIGHT AND WILL TAPER
OFF TUESDAY AS SHORT-WAVE RIDGE BUILDS OVER THE EASTERN BERING AND
FLOW BECOMES ANTICYCLONIC. COLDER AND WINDIER CONDITIONS WILL THEN
MOVE IN MID TO LATE WEEK AS A DEEP ARCTIC TROUGH DIGS SOUTHWARD
ACROSS WESTERN ALASKA.

BERING SEA/ALEUTIANS...WEATHER WILL REMAIN RELATIVELY CALM ACROSS
THE REGION AS MAJOR STORMS CONTINUE TO TRACK SOUTH OF THE ALEUTIANS.

.LONG TERM FORECAST...ARCTIC OUTBREAK WILL BE FIRMLY IN PLACE ACROSS
MAINLAND ALASKA BY THE END OF THE WEEK. MEANWHILE...A RIDGE WILL
BUILD OVER THE WESTERN BERING...SO AREAS IN BETWEEN THIS RIDGE AND
THE MAINLAND ALASKA TROUGH WILL OBSERVE THE STRONGEST COLD ADVECTION.
RIGHT NOW THE PRIME AREA LOOKS TO BE THE EASTERN BERING INTO
SOUTHWEST ALASKA. MEDIUM RANGE MODELS ARE VERY INCONSISTENT WITH
EVOLUTION OF PATTERN THIS WEEKEND INTO EARLY NEXT WEEK...NAMELY
HOW FAST THE TROUGH WILL LIFT OUT OF MAINLAND ALASKA.
THEREFORE...FORECAST CONFIDENCE IS VERY LOW.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...127 185.
         HEAVY FREEZING SPRAY WARNING...185.
FIRE WEATHER...NONE.

SEB FEB 10