Small Craft Advisory 94, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
105 PM AST TUE JAN 23 2007

.DISCUSSION...

UPPER LEVEL SUMMARY...LONG-WAVE TROUGH EXTENDS ACROSS THE ANCHORAGE
AOR WITH UPPER JET BETWEEN 30N AND 40N. A HIGH AMPLITUDE RIDGE IS
CENTERED OVER WESTERN NORTH AMERICA. EMBEDDED WITHIN THE LONG-WAVE
TROUGH IS A CLOSED LOW NEAR NOME WITH TROUGH AXIS EXTENDING
SOUTHEASTWARD INTO THE WESTERN GULF OF ALASKA. ANOTHER CLOSED LOW
IS CENTERED OVER THE WESTERN BERING SEA WITH TROUGH AXIS EXTENDING
SOUTHWARD TO A DEVELOPING LOW NEAR 40N 180.

AT THE SURFACE...THERE IS A WEAK LOW OVER THE NORTHERN GULF ABOUT
TO MOVE ONSHORE BETWEEN ICY CAPE AND CAPE SUCKLING. SURFACE TROUGH
EXTENDS WESTWARD TO THE SUSITNA VALLEY. BULK OF MOISTURE ASSOCIATED
WITH THIS SYSTEM IS MOVING OFF TO THE COPPER RIVER BASIN.
HOWEVER...COMBINATION OF LEFT-OVER MOISTURE/UPPER TROUGH POSITION/
LOW LEVEL COLD ADVECTION CONTINUES TO GENERATE LIGHT SNOW FROM
ANCHORAGE TO THE SUSITNA VALLEY. SNOW IS SLOWLY DIMINISHING AS THE
UPPER TROUGH SLOWLY PROGRESSES NORTHEASTWARD. ANOTHER LOW NEAR 51N
144W IS TRACKING NORTHWARD TOWARD THE GULF. OUT WEST...THERE IS A
SURFACE LOW NORTH OF SHEMYA AND A STATIONARY FRONT THAT EXTENDS FROM
KAMCHATKA SOUTHEASTWARD TO AROUND UMNAK ISLAND IN THE EASTERN
ALEUTIANS. SNOW/SNOW SHOWERS AND GUSTY WINDS CAN BE FOUND THROUGH
THIS REGION. THE BIG WEATHER MAKER FOR THE NEXT COUPLE DAYS IS A
RAPIDLY DEEPENING LOW NEAR 40N 180 WHICH IS TRACKING NORTHEASTWARD.
ESTIMATED CENTRAL PRESSURE IS 980 MB.

MODEL ANALYSIS...BASED ON LATEST SATELLITE IMAGERY MODELS ARE ALL
A BIT OFF ON POSITION OF GULF LOWS. HOWEVER THEY ARE CLOSE ENOUGH
THAT THERE WILL BE LITTLE IMPACT ON GULF WATERS/SOUTHCENTRAL
FORECAST. OTHERWISE...MODELS SOLUTIONS SHOW FAIR AGREEMENT THROUGH
72 HOURS WITH SYNOPTIC FEATURES AND DIVERGENCE BEYOND THAT. WILL
CONTINUE TO STICK CLOSE TO GFS SOLUTION.

SOUTHCENTRAL FORECAST...UPPER TROUGH IS VERY SLOW TO MOVE THROUGH
SOUTHCENTRAL ALASKA...SO LIGHT SNOW AND FLURRIES WILL HANG ON INTO
TOMORROW. SNOW HAS STOPPED ACROSS MUCH OF ANCHORAGE AND IS TRENDING
LIGHTER ACROSS THE MAT VALLEY. HOWEVER...AS COLD ADVECTION BEGINS IN
EARNEST TONIGHT EXPECT LIGHT SNOW OR FLURRIES TO START UP AGAIN AND
CONTINUE THROUGH EARLY TOMORROW MORNING WHEN UPPER TROUGH FINALLY
MOVES THROUGH. MOST SIGNIFICANT SNOWFALL WILL OCCUR ACROSS THE
EASTERN COPPER RIVER BASIN AS GULF SURFACE LOW MOVES TO THE YUKON.
AS UPPER TROUGH APPROACHES THE ALASKA RANGE WEDNESDAY AND FLOW
SHIFTS TO SOUTHWEST UPSLOPE AREAS WILL SEE ENHANCED SNOWFALL BEFORE
IT ENDS WEDNESDAY NIGHT. COLD ADVECTION BEHIND UPPER TROUGH WILL
BRING THE USUAL GUSTY WESTERLIES TO THE GULF WATERS TONIGHT THROUGH
WEDNESDAY. THERE WILL BE A BREAK IN PRECIP UNTIL FRONT ASSOCIATED
WITH PACIFIC LOW MOVES TO KODIAK ISLAND THURSDAY AND THE REST OF
SOUTHCENTRAL THURSDAY NIGHT.

BERING SEA/ALEUTIANS/SOUTHWEST ALASKA FORECAST...BLIZZARD WATCHES
CURRENTLY IN EFFECT FOR ZONES 181 185 187 195 WILL ALL BE UPGRADED
TO WARNINGS. ALONG AND HEAD OF FRONT TONIGHT THROUGH WEDNESDAY EXPECT
STORM FORCE TO HURRICANE FORCE WINDS COMBINED WITH SNOW. AS THE
FRONT MOVES ACROSS THE EASTERN ALEUTIANS AND AKPENN THURSDAY MORNING
ENOUGH WARM AIR SHOULD MAKE IT IN TO CHANGE PRECIP TO A MIX OF RAIN
AND SNOW OR ALL RAIN AND TEMPS SHOULD RISE TO FREEZING OR SLIGHTLY
ABOVE. WITH A LOW TRACK TO BRISTOL BAY THE CENTRAL ALEUTIANS AND
PRIBILOFS ARE SETTING UP FOR A LONG DURATION BLIZZARD CONDITIONS.
THEY WILL CERTAINLY STAY COLD ENOUGH. IN ADDITION...THERE IS A LOT
OF LOOSE SNOW ON THE PRIBILOFS SO IT WONT TAKE MUCH WIND TO PRODUCE
LOW VISIBILITIES...THUS EXPECT NEAR BLIZZARD CONDITIONS EVEN WITHOUT
NEW SNOW FALLING. POTENTIAL FOR BLIZZARD OR BLOWING SNOW CONDITIONS
FOR ZONE 155 AND 161 WILL NEED TO BE EVALUATED AS WE GET CLOSER TO
EVENT. RIGHT NOW...WINDS LOOK MARGINAL FOR PRODUCING BLIZZARD
CONDITIONS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WATCH 181 185 187 191.
MARINE...GALE WARNING 130 132 150 160 179.
         STORM WARNING 155 165 171 175.
         HURRICANE FORCE WIND WARNING 170 172.
         HEAVY FREEZING SPRAY WARNING 120 121 129 130 132 138 140
                                      141 150 160 165 179 185.

SEB JAN 07