Gale Warning 748, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT SUN OCT 1 2006

.DISCUSSION...

.ANALYSIS...IR SATELLITE IMAGERY SHOWS LARGE CYCLONIC CIRCULATION
OVER THE EASTERN BERING SEA. THERE ARE TWO CENTERS AT THE
SURFACE...THE OLD ONE JUST NORTH OF SAINT PAUL AND A NEWLY FORMED
ONE ABOUT HALF WAY BETWEEN COLD BAY AND CAPE NEWENHAM. A WEAKENING
OCCLUSION EXTENDS FROM THE OLD LOW CENTER NORTHEASTWARD TO THE
KUSKOKWIM DELTA AND SOUTHEASTWARD ACROSS THE KUSKOKWIM VALLEY AND
COOK INLET TO THE CENTRAL GULF. PRECIP ALONG THE FRONT IS LIGHT.
SNOW LEVELS ARE GENERALLY 2500 TO 3500 FEET. TIGHT PRESSURE GRADIENT
ALONG THE NORTH GULF COAST IS PRODUCING EASTERLY GAP WINDS IN THE
35 TO 50 KT RANGE AND KEEPING LEE SIDE OF KENAI AND CHUGACH MOUNTAINS
MOSTLY DRY. INLAND AREAS WILL LIKELY REMAIN DRY AS FRONT CONTINUES
TO FALL APART. AREAS OF STRATUS AND RAIN ASSOCIATED WITH NEW LOW
NORTH OF COLD BAY AS MOVING ACROSS AKPENN TO KODIAK ISLAND AND
BRISTOL BAY. THE WEST SIDE OF THE LOW COMPLEX INCLUDING THE SOUTHERN
AKPENN AND EASTERN ALEUTIANS ARE EXPERIENCING STRONG WINDS. RECENT
SHIP REPORTS INDICATE 40 KTS OF WIND WITH STRONGER GUSTS TO 55 KT
THROUGH CHANNELED AREAS. SEAS ON THE PACIFIC SIDE HAVE BUILT UP TO
20 FEET. ELSEWHERE...A COLD CORE LOW WITH MULTIPLE CENTERS HAS
DROPPED DOWN TO JUST WEST OF THE WESTERN ALEUTIANS AND A DEVELOPING
LOW IS NOTED A FEW HUNDRED MILES SOUTH OF AMCHITKA.

MODEL ANALYSIS...MODEL SOLUTIONS ARE ALL OVER THE PLACE TODAY.
IN THE NEAR-TERM SOLUTIONS ARE FAIRLY CLOSE WITH EASTERN BERING
LOW AND ASSOCIATED UPPER TROUGH. THERE IS A KEY DIFFERENCE IN
POSITION OF UPPER TROUGH AS IT SWINGS THROUGH SOUTHCENTRAL MONDAY.
NAM IS MUCH FURTHER EAST THAN GFS/UKMET AND WOULD RESULT IN A DRIER
FORECAST FOR ANCHORAGE AND VICINITY WITH CONTINUED STRONG SOUTHEAST
FLOW. PREFER THE WETTER GFS/UKMET IN KEEPING TROUGH FURTHER WEST AND
SOUTH TO SOUTHWEST FLOW ALOFT OVER SOUTHCENTRAL. NONE OF MODELS HAVE
A GREAT HANDLE ON COLD CORE LOW MOVING TOWARD WESTERN ALEUTIANS. IT
IS FARTHER SOUTH THAN ANY SOLUTIONS INDICATE AND FORECAST WILL BE
ADJUSTED TO ACCOUNT FOR THIS. THIS LOW WILL NOT BE A MAJOR FACTOR.
THE LOW TO WATCH IS THE DEVELOPING ONE OVER THE NORTH PACIFIC. AS
MENTIONED YESTERDAY THE GFS HAS TRENDED WESTWARD WITH THE TRACK OF
THIS LOW WITH EACH RUN AND CONTINUES TO DO SO. WITH AN AMPLIFYING
TROUGH...UPPER JET SUPPORT...AND DECENT COLD ADVECTION ON THE BACK
SIDE OF THE TROUGH...PREFER THE STRONGER AND FARTHER WEST SOLUTION
OF GFS.

.FORECAST...AREAS OF LIGHT RAIN (AND SNOW AT HIGHER ELEVATIONS)
WILL CONTINUE ACROSS SOUTHERN MAINLAND TONIGHT AS OCCLUSION WEAKENS.
STEADIER PRECIP ASSOCIATED WITH UPPER TROUGH WILL MOVE OVER KODIAK
AND SOUTHWEST ALASKA THIS EVENING AND PROGRESS NORTHWARD MONDAY.
TEMPERATURE ADVECTION AHEAD OF THIS TROUGH IS NEAR NEUTRAL SO SOME
AREAS OF NORTHERN SUSITNA VALLEY MAY SEE A LITTLE SNOW LATE
MONDAY...BUT DO NOT EXPECT ANYTHING SIGNIFICANT. WINDS ALONG
AKPENN AND EASTERN ALEUTIANS WILL DIE DOWN QUICKLY TONIGHT AS
EASTERN BERING LOW MOVES INLAND AND SHORT-WAVE RIDGE MOVES OVERHEAD
AHEAD OF NEXT SYSTEM. CONDITIONS WILL HEAD QUICKLY DOWNHILL EARLY
MONDAY MORNING AS DEPPENDING LOW MOVES TO THE EASTERN ALEUTIANS
AND THEN INTO THE EASTERN BERING. EXPECT STROM FORCE WINDS ALONG
THE EASTERN ALEUTIANS MONDAY AFTERNOON AS THE LOW MOVES INTO THE
BERING AND GALES MOST OTHER LOCATIONS. HIGHLY AMPLIFIED TROUGH WILL
ALLOW SYSTEM TO TAP INTO TROPICAL MOISTURE SO RAINFALL AMOUNTS WILL
BE HEAVY. MODERATE COLD ADVECTION OVER WESTERN TO CENTRAL BERING SEA
EARLY TO MID WEEK WILL COOL SURFACE TEMPS AND GENERATE THE FIRST
SNOW SHOWERS OF THE SEASON ACROSS MUCH OF THE BERING SEA REGION. THE
SOUTHERN MAINLAND WILL HAVE LITTLE BREAK BETWEEN UPPER TROUGH MONDAY
NIGHT AND EFFECTS OF BERING LOW. PRESSURE GRADIENT WILL LOOSEN MONDAY
AND THEN QUICKLY TIGHTEN BACK UP MONDAY NIGHT AND TUESDAY. EVEN WITH
THESE STRONG EASTERLY WINDS ABUNDANT DEEP MOISTURE AND SOUTHERLY FLOW
ALOFT WILL PROVIDE DECENT PERIOD OF RAIN FOR ANCHORAGE AND OTHER LEE
SIDE AREAS TUESDAY THROUGH TUESDAY NIGHT WHILE COASTAL AND UPSLOPE
AREAS WILL GET SOAKED. THERE WILL BE PLENTY OF WARM ADVECTION ACROSS
THE MAINLAND SO ALL PRECIP WILL FALL AS RAIN.

LOOKING TOWARD THE EXTENDED FORECAST PERIOD...MEAN TROUGH POSITION
REMAINS OVER BERING SEA SO LOOK FOR CURRENT STORM TRACK FROM PACIFIC
NORTHWARD INTO BERING SEA TO CONTINUE TO PROVIDE WET WEATHER TO THE
EASTERN BERING AND SOUTHERN MAINLAND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING 170.
         GALE WARNING 155 165 171 172 175 176 179 180 185.

SEB OCT 06