Small Craft Advisory 883, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 AM AKST SUN NOV 1 2009

.MODEL DISCUSSION...

MODELS ARE IN GREAT AGREEMENT THROUGH THE FIRST 48 HOURS...THEN
DIFFER A BIT WITH RESPECT TO THE ARRIVAL OF A LOW AND ASSOCIATED
FRONT THAT BEGINS TO AFFECT THE SOUTHWEST COAST AND THE GULF MONDAY
NIGHT INTO EARLY TUESDAY. THE GFS MODEL WAS PREFERRED FOR THIS
PACKAGE WITH RESPECT TO THIS FEATURE AND RESULTING TRIPLE POINT
CYCLOGENESIS NEAR KODIAK ISLAND TUESDAY MORNING OR AFTERNOON. NEAR
THE END OF THE SHORT TERM PERIOD TUESDAY NIGHT INTO
WEDNESDAY...MODELS ARE CONTINUING TO BE QUITE CONSISTENT IN A
FAST-MOVING LOW THAT STRENGTHENS SUBSTANTIALLY AS IT MOVES WEST TO
EAST UP THE ALEUTIAN CHAIN AND ENTERS THE SOUTHWEST GULF. SINCE THE
GFS AND EUROPEAN MODELS HAVE SHOWN REMARKABLE CONSISTENCY...AND WERE
NOT TOO FAR OFF ON THE STRENGTH OF THIS STRONG LOW IN THE GULF
WEDNESDAY INTO THURSDAY...WE USED A BLEND OF THE TWO MODELS IN THE
MIDDLE TO EXTENDED RANGE.

.ANALYSIS AND UPPER LEVELS...

A CLOSED UPPER LOW AND WEAK SURFACE LOW CONTINUE TO SPIN NEARLY
STATIONARY IN THE NORTHERN GULF OF ALASKA. ASSOCIATED DISTURBANCES
CONTINUE TO ROTATE AROUND THIS FEATURE...BRINGING OCCASIONAL ISOLATED
OR WIDELY SCATTERED SHOWERS TO THE EASTERN KENAI PENINSULA AND
SOUTHEASTERN PRINCE WILLIAM SOUND REGIONS. THESE LOWS WILL BEGIN TO
MOVE TOWARDS THE NORTHERN PANHANDLE AND THE YUKON TERRITORY DURING
THE DAY ON MONDAY AS THE UPPER RIDGE TO THE NORTHWEST OVER THE
NORTHERN COASTAL REGION CUTS OFF AND THE FLOW OVER SOUTHERN ALASKA
BECOMES MORE PROGRESSIVE. THIS WILL FINALLY ALLOW LOW PRESSURE
SYSTEMS TO WORK THEIR WAY EASTWARD TO AFFECT THE EASTERN
ALEUTIANS...THE ALASKA PENINSULA...AND THE SOUTHWESTERN MAINLAND OVER
THE NEXT FEW DAYS. THE FIRST LOW WILL MOVE FROM WEST OF ATTU ISLAND
TO NEAR NUNIVAK ISLAND OVER THE NEXT 48 HOURS WITH AN ASSOCIATED
FRONT TO ITS SOUTHEAST BRINGING GALE FORCE WINDS AND SNOW AND RAIN.
THE FOLLOWING SYSTEM ON ITS HEELS DEVELOPS NEAR THE WESTERN ALEUTIANS
MONDAY NIGHT AND THEN QUICKLY MOVES EASTWARD UP THE ALEUTIAN CHAIN TO
NEAR KODIAK ISLAND EARLY WEDNESDAY. THERE ARE STRONG INDICATIONS THAT
WILL LOW WILL BE OF SIGNIFICANT STRENGTH THAT WIDESPREAD STRONG GALES
TO STORM-FORCE WINDS WILL BE LIKELY FOR A PORTION OF WEDNESDAY INTO
FRIDAY FOR A GOOD PORTION OF THE GULF AND OUTSIDE COASTAL WATERS.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

IT IS A MUCH QUIETER MORNING THAN USUAL ACROSS THE SOUTHCENTRAL
REGION. WINDS CONTINUE TO SUBSIDE AS THE PRESSURE GRADIENT CONTINUES
TO RELAX BETWEEN HIGH PRESSURE TO THE NORTH AND WEAKENING LOW
PRESSURE IN THE GULF OF ALASKA. SOME GUSTY WINDS CONTINUE TO BLOW
THROUGH THE THOMPSON PASS AND VALDEZ AREAS ON OCCASION...BUT EVEN
THESE SHOULD STAY NEARLY STEADY FOR THE NEXT 24 HOURS BEFORE THE LOW
IN THE GULF MOVES OUT AND WEAKENS. AVERAGE TEMPERATURES WILL CONTINUE
TO BE BELOW NORMAL UNDER MOSTLY CLEAR SKIES ACROSS THE REGION...SAVE
FOR SOME SCATTERED CLOUDS ALONG THE EASTERN KENAI PENINSULA REGION
WITH A MINOR DISTURBANCE ROTATING AROUND THE WEAK GULF LOW. THIS
DISTURBANCE COULD LATER AFFECT THE EASTERN END OF KODIAK ISLAND THIS
AFTERNOON WITH ISOLATED OR SCATTERED SHOWERS AS IT MOVES TO THE
SOUTH.

SOUTHWEST ALASKA...

A WEAKENING NORTHEASTERLY JET OVER THE REGION THIS MORNING WILL
CONTINUE TO FILTER DOWN OCCASIONALLY GUSTY NORTHEASTERLY WINDS TO
AROUND 15 OR 20 KNOTS ACROSS MOST OF THE REGION IN THE CONTINUED COLD
ADVECTION REGIME. SKIES WILL BE MOSTLY CLEAR TODAY...THEN INCREASING
CLOUDS WILL MOVE WEST TO EAST ACROSS THE AREA AS A 972 MB LOW
APPROACHES THE DELTA REGION WITH A GALE-FORCE FRONT THAT MOVES ONTO
THE SOUTHWEST MAINLAND MONDAY EVENING INTO TUESDAY. AS WARM AIR MOVES
IN ALOFT AND COLD AIR GETS TRAPPED BENEATH AN INVERSION AT THE
SURFACE ON TUESDAY...THE POSSIBILITY OF SOME FREEZING RAIN IN
INTERIOR VALLEYS OF SOUTHWEST ALASKA IS CERTAINLY A POSSIBILITY AND
WILL NEED TO BE WATCHED. OTHERWISE...THERE SHOULD BE A MIX OF SNOW
AND RAIN GRADUALLY BECOMING MORE RAIN AS WARM MARITIME AIR MOVES ITS
WAY ONSHORE TUESDAY...BEFORE COLD ADVECTION SETS BACK IN ON THE BACK
SIDE OF THE LOW AND FRONT AND TURNS THE PRECIPITATION BACK TO SNOW
LATE TUESDAY NIGHT.

ALEUTIANS/BERING SEA/ALASKA PENINSULA...

THE BIG ISSUE OUTSIDE OF PRECIPITATION WITH ASSOCIATED FRONTS AND
LOWS WILL BE FORECASTING THE WINDS FOR MARINE ZONES AND FOR CHANNELED
TERRAIN IN THE PUBLIC ZONES AS THE FRONT MOVES ACROSS THE REGION. A
SECOND LOW THAT DEVELOPS JUST SOUTH OF THE WESTERN ALEUTIANS MONDAY
NIGHT WILL INTENSIFY RAPIDLY AS IT RACES ALONG OR JUST SOUTH OF THE
ISLAND CHAIN AND TOWARDS THE GULF BRINGING A PERIOD OF STRONG AND
GUSTY WINDS NEAR THE PATH OF THE LOW TUESDAY INTO TUESDAY NIGHT.

.LONG TERM FORECAST...

BY WEDNESDAY AFTERNOON...THE SYNOPTIC PATTERN WILL BE ALMOST A
COMPLETE OPPOSITE OF THAT EXPERIENCED THE LAST FEW DAYS. A LARGE LOW
WITH GALE TO STORM FORCE WINDS WILL ENCOMPASS MOST OF THE GULF OF
ALASKA WITH A STRONG UPPER LOW THAT WILL BRING WIDESPREAD
PRECIPITATION CHANCES TO ALL OF THE SOUTHERN PART OF THE STATE FROM
WEDNESDAY THROUGH SATURDAY OF NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING...120 172 175
         STORM WARNING...176
FIRE WEATHER...NONE.

CC NOV 09