Small Craft Advisory 183, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
300 PM AKST MON MAR 3 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL TROUGH OVER NORTHWEST ALASKA IS SLOWLY PUSHING TO THE
SOUTH AND EAST. WEAK LOW PRESSURE IS OVER THE NORTH GULF COAST
RESULTING IS SCATTERED SHOWERS IN THAT REGION. A LOW ABOUT 600 MILE
SOUTH OF THE ALASKA PENINSULA HAS SEVERAL EMBEDDED CIRCULATIONS THAT
ARE SPINNING AROUND THE MAIN CENTER. THIS IS PUSHING LOW CLOUDS
ACROSS THE ALEUTIANS AND MOST OF THE BERING SEA.

.MODEL DISCUSSION...
THE MODELS REMAIN IN GOOD AGREEMENT WITH THE MOVEMENT OF THE UPPER
TROUGH ACROSS THE ALASKA RANGE TO THE KENAI PENINSULA WHILE A SURFACE
LOW DEVELOPS BENEATH THIS UPPER TROUGH TUE. MODELS ARE IN GOOD
AGREEMENT WITH RESPECT TO THE STORM THAT WILL ROTATE TO ABOUT 300 NM
SOUTH OF THE WESTERN ALEUTIANS TUE AS IT INTENSIFIES THEN ROTATES
BACK TO THE WEST THEN SOUTH THROUGH WED NIGHT AS IT WEAKENS. TOWARD
THE END OF THE WEEK THE MODELS ARE GENERALLY HANDLING THE LOW SOUTH
OF THE ALEUTIANS SIMILARLY AND ARE IN AGREEMENT WITH A TROUGH
EXTENDING ACROSS THE GULF OF ALASKA. THE INTENSITY OF THE SUPPORTING
LOW CENTER IS IN GENERALLY GOOD AGREEMENT, THOUGH THE LOCATION OF THE
LOW CENTERS IS MORE VARIED. CONFIDENCE OF THE SOLUTION TO THE GULF OF
ALASKA IS MODERATE WHILE THE ALEUTIANS AND BERING SEA ARE IN GOOD
OVERALL AGREEMENT ABOUT A MODERATE PRESSURE GRADIENT BETWEEN HIGH
PRESSURE OVER THE RUSSIAN FAR EAST AND THE LOW SOUTH OF THE
ALEUTIANS.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
WE ARE STILL FOCUSED ON THE CHANGE FROM THE DRY CLEAR CONDITIONS TO
INCREASED CLOUD COVER AND THREAT FOR SNOW OVER THE SOUTH CENTRAL
REGION BEGINNING TUE. THIS TROUGH WILL BRING IN SOUTHWEST FLOW ALOFT
UP COOK INLET INTO THE SUSITNA VALLEY TUE MORNING AND WE ARE
EXPECTING THIS TO BE A LONGER DURATION SNOW EVENT WITH GENERALLY
LOWER RATES OF SNOW FALL. WE STILL ANTICIPATE ISSUING AN ADVISORY FOR
THE SUSITNA VALLEY. THE BIGGER CONCERN IS WHEN AND THEN HOW MUCH SNOW
WILL FALL OVER THE ANCHORAGE TO PALMER WASILLA AREA. AT THIS POINT IT
APPEARS THE SNOW FOR ANCHORAGE SHOULD START OVERNIGHT TUE NIGHT TO
WED MORNING CONTINUING THROUGH THU MORNING WITH LIGHT ACCUMULATION.

SOUTHWEST ALASKA...
EXPECT THE CLOUDS TO INCREASE BY TUESDAY NIGHT AS THE UPPER LEVEL
TROUGH DIGS TO THE SOUTHWEST INTO THE BERING SEA AND MOISTURE FLOWS
IN FROM THE WEST AND SOUTHWEST OFF THE BERING SEA. THE KUSKOKWIM
DELTA AND LOWER KUSKOKWIM VALLEY ARE EXPECTED TO REMAIN RELATIVELY
CLEAR. SOME CLOUDS SHOULD FORM ALONG THE ALEUTIAN MOUNTAINS WHILE THE
REMAINDER OF THE BRISTOL BAY ZONE STAYS ON THE CLEAR SIDE WED.

THE BERING SEA AND ALEUTIAN CHAIN...
THE ARCTIC FRONT EXTENDS EAST WEST ACROSS THE BERING SEA ALONG 57N
BETWEEN THE HIGH OVER THE RUSSIAN FAR EAST AND LOW PRESSURE SOUTH OF
THE ALEUTIANS. AS THE LOW MOVES TO SOUTH OF KISKA THROUGH TUE
EVENING, THE PRESSURE GRADIENT INCREASES AND WILL SUPPORT GALE FORCE
TO LOW END STORM FORCE WIND ALONG THE CENTRAL TO WESTERN ALEUTIANS
AND THE ADJACENT BERING SEA OFFSHORE WATERS WED. A LARGE SWATH OF
MOISTURE DEVELOPS ALONG THE FRONT THEN MOVES TO THE CENTRAL AND
WESTERN ALEUTIANS TUE EVENING. EXPECT THIS TO START AS RAIN THAT WILL
MIX WITH THEN CHANGE OVER TO SNOW WED NIGHT AND THU.

.LONG TERM FORECAST...
LOW PRESSURE WILL PERSIST SOUTH OF THE ALEUTIANS WHILE THE HIGH OVER
THE RUSSIAN FAR EAST ALSO PERSISTS INTO THE WEEKEND. EXPECT THE EAST
TO NORTH FLOW TO REMAIN BUT SLOWLY DIMINISH INTO THE WEEKEND. THE LOW
SOUTH OF THE ALEUTIANS WILL HAVE SOME WEAKER FRONTAL LOW FORM AND
ROTATE INTO THE GULF OF ALASKA FRI AND SAT. THE EXACT STRENGTH AND
POSITION OF THE LOW CENTERS IS A BIT UNCERTAIN AT THIS TIME DUE TO
POOR MODEL AGREEMENT. AT THIS POINT WE ARE EXPECTING THE STRONGER LOW
CENTER TO COME UP INTO THE EASTERN GULF OF ALASKA SAT THEN ROTATE
BACK TO THE WEST TOWARD KODIAK ISLAND SUN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE WARNING 175 176 177 178 411 412 413.

         HEAVY FREEZING SPRAY WARNING 160 180 185 412 414.
FIRE WEATHER...NONE.

SAM MAR 14

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
400 PM AKST MON MAR 3 2014

AKZ101-111-131-145-042100-

...LIGHT SNOW RETURNS TO THE SOUTHCENTRAL...

A LOW PRESSURE CENTER ALOFT WILL MOVE OVER THE WESTERN
INTERIOR/SOUTHWEST MAINLAND OVERNIGHT TONIGHT. IN RESPONSE TO
THIS...WINDS ALOFT WILL BECOME MORE UP-INLET (WHICH IS FAVORABLE FOR
MOISTURE TRANSPORT) AND CREATE A MODERATE DURATION LIGHT SNOWFALL
OVER A BROAD AREA. SNOW LOOKS TO DEVELOP BY LATE MORNING/EARLY
AFTERNOON OVER THE SUSITNA VALLEY AND THEN SLOWLY BUILD SOUTHWARD
OVER THE MATANUSKA VALLEY AND ANCHORAGE BOWL BY THE LATE
AFTERNOON/EVENING HOURS ON TUESDAY. SNOW LOOKS TO BEGIN ALONG THE
NORTH GULF COAST ON TUESDAY AFTERNOON AS WELL WITH HIGHER INTENSITY
THAN THE COOK INLET REGION. LIGHT SNOWFALL WILL CONTINUE THROUGH THE
DAY ON WEDNESDAY AND INTO EARLY THURSDAY MORNING BEFORE TAPERING OFF.

LAWSON