Gale Warning 890, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKST SUN NOV 7 2010

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT WITH LARGE SCALE FEATURES...BUT NOT SO
GOOD WITH RESPECT TO THE MESOSCALE FEATURES. GFS SEEMS TO BE AN
OUTLIER WITH RESPECT TO THE TROUGH OR WEAK LOW IN THE GULF OF ALASKA
BEGINNING TOMORROW NIGHT...SO THE NAM WAS PREFERRED THERE. IN THE
BERING...DIFFICULTY LIES IN TRYING TO FIGURE OUT TIMING AND STRENGTH
OF THE MANY SHORTWAVE DISTURBANCES ROTATING AROUND THE LARGE CYCLONE
MOVING FROM THE WEST INTO THE BERING SEA OVER THE NEXT 48 HOURS. THE
GFS WAS LARGELY PREFERRED OUT WEST FOR THIS PACKAGE.

.ANALYSIS AND UPPER LEVELS...

LARGE MID LEVEL CYCLONE WITH MULTIPLE DISTURBANCES CONTINUES ROTATING
IN THE GULF. ONE OF THESE LOWS IS FORECAST TO MOVE INTO THE
NORTHWEST GULF NEAR THE SOUTHEAST KENAI PENINSULA TODAY INTO SUNDAY
NIGHT. AT THE SAME TIME AN UPPER LEVEL TROUGH/LOW OVER SOUTHWEST
ALASKA WILL BEGIN TO MOVE EAST AND THEN NORTH ACROSS THE NORTHERN
COOK INLET REGION AND THE SUSITNA VALLEY. WEAK DEFORMATION IS LIKELY
TO INITIATE LIGHT SNOW ACROSS THE UPPER COOK INLET REGION INTO THE
SUSITNA VALLEY OVER THE NEXT DAY OR SO...LIKELY RESULTING IN LIGHT
ACCUMULATIONS OF SNOW.

OUT WEST...MID LEVEL RIDGING OVER THE CENTRAL BERING MOVES NORTH AND
EAST AHEAD OF A PAIR OF CYCLONES. ONE CYCLONE STAYS SOUTH OF THE
ALEUTIANS AND RACES UNDERNEATH THE RIDGE ALONG 50N TOWARDS THE WEST
COAST...STAYING SOUTH OF THE GULF THROUGH MONDAY. THE SECOND AND
LARGER CYCLONE MOVES INTO THE FAR WESTERN BERING TODAY AND THEN
BECOMES STATIONARY BY MONDAY IN THE CENTRAL BERING. TIMING AND
STRENGTH OF THESE DISTURBANCES ROTATING AROUND THE LARGER PARENT
CYCLONE ARE VERY PROBLEMATIC...SO THE FORECAST HAS HIGHER UNCERTAINTY
THAN NORMAL ON THE MESOSCALE LEVEL THROUGH THE SHORT TERM PAST SUNDAY
EVENING.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

LOW PRESSURE SYSTEM IN THE GULF WILL CONTINUE TO ROTATE IN THE GULF
THROUGH EARLY MONDAY. THE UPPER LEVEL LOW OVER THE SOUTHWEST ALASKA
MAINLAND WILL MOVE NORTH AND EAST AND WILL BRING ENOUGH DYNAMICS
TODAY TO INCREASE THE SNOW COVERAGE OVER THE KENAI PENINSULA THIS
MORNING THROUGH THIS AFTERNOON. MODELS EVEN HINT THAT THERE COULD BE
A WEAK DEFORMATION ZONE BETWEEN THE LOW IN THE GULF AND THE UPPER
LEVEL TROUGH. SNOW APPEARS LIKELY BEGINNING VERY LATE THIS AFTERNOON
OR EARLY THIS EVENING FOR THE ANCHORAGE BOWL...AND THOUGH SNOW WILL
BE LIGHT...UP TO 2 INCHES COULD FALL ACROSS THE AREA BEFORE THE
TROUGH MOVES THROUGH LATE TONIGHT. MOST OF THE AREA DRIES OUT FOR
EARLY IN THE WEEK...WITH EASTERLY UPSLOPE BRINGING SNOW SHOWERS TO
THE EASTERN KENAI PENINSULA. OTHERWISE...THE BEGINNING OF THE WEEK
EXCEPT FOR EARLY MONDAY MORNING WILL BE ON THE DRY SIDE.

SOUTHWEST ALASKA...

HIGH PRESSURE AT THE SURFACE AND A SUBSEQUENT BUILDING OF A MID LEVEL
RIDGE OVER THE AREA TONIGHT AND MONDAY WILL RESULT IN MAINLY DRY
WEATHER...WITH FOG A CONCERN WHERE WINDS ARE ABLE TO DECOUPLE AT
NIGHT. A WEAK FRONT MAY SKIRT THE COASTAL AREAS OF THE KUSKOKWIM
DELTA AND BRING SOME ISOLATED SHOWERS.

BERING SEA REGION...

IMPRESSIVE LOW PRESSURE SYSTEM ON SATELLITE A FEW HUNDRED MILES SOUTH
OF THE ALEUTIANS IS SPREADING AN IMPRESSIVE CIRRUS SHIELD OVER THE
ISLAND CHAIN INTO THE CENTRAL BERING SEA. THIS SYSTEM WILL BRING
STEADY PRECIPITATION MAINLY IN THE FORM OF RAIN (AND SOME SNOW) AS IT
MOVES SWIFTLY TO THE EAST ALONG THE 50TH PARALLEL. THE NEXT SYSTEM
WILL MOVE INTO THE WESTERN BERING TODAY AND WILL SLOWLY MOVE EAST
OVER THE COMING DAYS. DISTURBANCES OF VARYING INTENSITIES WILL ROTATE
AROUND THIS CYCLONE AND KEEP UNSETTLED WEATHER IN THE FORECAST
THROUGH THE SHORT TERM.

.LONG TERM FORECAST...

LARGE CYCLONIC FLOW IS FORECAST BY MODELS TO REMAIN OVER THE NORTHERN
BERING SEA. THE MAIN STORM TRACK APPEARS TO SET UP BEGINNING EARLY IN
THE WEEK FROM SOUTH OF THE ALEUTIANS IN THE NORTH PACIFIC NORTH AND
EAST INTO THE GULF OF ALASKA. DETAILS OF INDIVIDUAL LOW PRESSURE
SYSTEMS WILL HOPEFULLY BECOME MORE CLEAR AS MIDWEEK APPROACHES. THERE
IS SOME POTENTIAL FOR A WARMER AND STORMIER WEATHER PATTERN TO RESUME
LATE IN THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES...120 132 150 155 176 185
         STORMS...130
FIRE WEATHER...NONE.

CC NOV 10