Gale Warning 891, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
430 AM AKST MON NOV 8 2010

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT. AS USUAL...THE DIFFERENCES LIE ON THE
SMALL SCALE...OR MESOSCALE...LEVEL. A NAM/EC BLEND WAS PREFERRED ON
THE EAST SIDE AND THE NAM WAS LARGELY PREFERRED ON THE WEST. TOWARDS
MIDWEEK...MODELS ARE IN GOOD AGREEMENT WITH HPC GUIDANCE IN THE TRACK
OF ANOTHER STRONG LOW THAT MOVES INTO THE GULF OF ALASKA AND
EVENTUALLY TO THE GULF COAST BY LATE WEEK.

.ANALYSIS AND UPPER LEVELS...

AN BAND OF MODERATE SNOW IS SITUATED ACROSS THE KENAI
PENINSULA...SOUTH AND WEST PARTS OF ANCHORAGE...AND FAR SOUTHERN AND
WESTERN PARTS OF THE SUSITNA VALLEY ZONE THIS MORNING. THIS FEATURE
IS THE RESULT OF DEFORMATION ALOFT AS WELL AS AN UPPER LEVEL TROUGH
SITUATED JUST WEST OF THE AREA. THIS TROUGH/LOW WILL SLIDE SOUTH AND
EAST ACROSS THE KENAI PENINSULA TODAY AND WILL PIVOT AN INVERTED
SURFACE TROUGH FROM THE GULF LOW WESTWARD FROM PRINCE WILLIAM SOUND
INTO THE COOK INLET REGION LATER THIS MORNING INTO EARLY AFTERNOON.
SNOW WILL CONTINUE THROUGH THE MORNING HOURS FOR ANCHORAGE...THEN
LIKELY DIMINISH TO OCCASIONAL LIGHT SHOWERS AS THE BAND SLIDES JUST
SOUTH OVER THE KENAI PENINSULA...WITH SOUTH AND WEST ANCHORAGE
ACCUMULATING THE HIGHEST SNOW TOTALS. SEE THE LATEST MORNING FORECAST
PACKAGE FOR THE EXPECTED SNOW ACCUMULATIONS FOR EACH ZONE.

OTHERWISE...UPPER LEVEL RIDGING CONTINUES TO BUILD OVER THE SOUTHWEST
BRINGING MOSTLY DRY CONDITIONS AND PARTLY CLOUDY SKIES. A LARGE
CYCLONE IN THE BERING WILL SLOWLY MOVE EASTWARD OVER THE NEXT FEW
DAYS...WITH DISTURBANCES ROTATING AROUND THE PARENT LOW BRINGING
PERIODS OF RAIN AND SNOW. A WEATHER FRONT WILL MOVE EAST ACROSS THE
CENTRAL ALEUTIANS...THEN THE EASTERN ALEUTIANS AND ALASKA PENINSULA
TONIGHT INTO EARLY TUESDAY.

THE ONLY OTHER FEATURE OF NOTE IS ANOTHER CYCLONE MOVING ALONG THE
50TH PARALLEL. INTERACTION WITH THE LOW IN THE GULF IS INDIRECTLY
AIDING IN THE ENHANCED PRECIPITATION OVER SOUTHCENTRAL REGION THIS
MORNING.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

SNOW WILL DIMINISH FROM NORTH TO SOUTH ACROSS THE MATANUSKA-SUSITNA
VALLEY AND THEN THE ANCHORAGE BOWL LATER THIS MORNING AS THE NEARLY
STATIONARY TROUGH PROVIDING THE DYNAMICS ALOFT MOVES ACROSS THE KENAI
PENINSULA. SOUTH AND WEST ANCHORAGE WILL PICK UP THE HIGHEST AMOUNTS
WITH LESSER AMOUNTS NORTH AND EAST TOWARDS PALMER. A CHANCE OF A FEW
SNOW SHOWERS WILL CONTINUE ACROSS THE AREA AS THE TROUGH DEPARTS TO
THE NORTHERN GULF AND/OR PRINCE WILLIAM SOUND TONIGHT...HOWEVER IT
APPEARS A WEAK SURFACE TROUGH WILL BE LEFT BEHIND. THE HIGHER
RESOLUTION MODELS (SUCH AS THE 00Z AND 06Z NAM) ARE HINTING AT THE
DEVELOPMENT OF A MESOSCALE LOW IN NORTHERN COOK INLET WHICH COULD
HELP BRING ANOTHER SHOT AT LIGHT SNOW FOR THE ANCHORAGE BOWL...BUT
FORECASTING FOR SUCH A SMALL SCALE FEATURE IS RATHER PROBLEMATIC WHEN
MORE THAN 6 HOURS BEFORE THE EVENT BEGINS. IT WILL BE SOMETHING TO
KEEP AN EYE ON FOR TUESDAY MORNING. OTHERWISE...SURFACE RIDGING WILL
BUILD ACROSS THE GULF AND SOUTHEASTERN MAINLAND TUESDAY AND THEN
SLIDE EAST AHEAD OF THE NEXT LOW WHICH MOVES INTO THE GULF LATE
WEDNESDAY NIGHT.

SOUTHWEST MAINLAND...

OUTSIDE OF SCATTERED SNOW SHOWERS IN THE KUSKOKWIM VALLEY
ZONE...MOSTLY DRY WEATHER AND PARTLY CLOUDY SKIES ARE IN STORE FOR
THE REGION UNTIL TUESDAY MORNING. THE FIRST IN A SERIES OF
DISTURBANCES ROTATING AROUND THE PARENT LOW IN THE BERING WILL BEGIN
TO AFFECT THE BRISTOL BAY COAST BY TUESDAY AFTERNOON. MODELS THEN
HINT AT INTERACTING BETWEEN THE CYCLONE OVER THE BERING SEA AND AN
INTENSIFYING CYCLONE MOVING TOWARDS THE GULF TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT WHICH WILL BRING A GOOD CHANCE OF PRECIPITATION TO
MOST AREAS.

BERING SEA REGION...

LARGE PARENT CYCLONE WITH VARIOUS WEAK DISTURBANCES ROTATING AROUND
IT WILL KEEP RAIN AND SNOW IN THE FORECAST THROUGH WEDNESDAY FOR MOST
AREAS...WITH THIS FEATURE BEING ABSORBED INTO THE LARGER AND MORE
INTENSE NORTH PACIFIC CYCLONE MOVING NORTHEAST TOWARDS THE GULF AS
HIGH PRESSURE BUILDS OVER THE BERING ON WEDNESDAY.

.LONG TERM FORECAST...

AN ACTIVE WEATHER PATTERN REMAINS IN PLACE THROUGH NEXT WEEKEND AS
THE MAIN STORM TRACK WILL TAKE SYSTEMS FROM THE NORTH PACIFIC SOUTH
OF THE ALEUTIANS INTO THE GULF AND THEN ONSHORE ALONG THE SOUTHERN
MAINLAND COAST. WARMER THAN NORMAL TEMPERATURES AND NORMAL TO ABOVE
NORMAL PRECIPITATION APPEARS LIKELY FOR THE SOUTHCENTRAL REGION.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES...120 125 130 175 176.
FIRE WEATHER...NONE.

CC NOV 10