Small Craft Advisory 957, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
502 AM AKST TUE DEC 1 2015

.ANALYSIS AND UPPER LEVELS...
MUCH OF ALASKA REMAINS UNDER THE INFLUENCE OF A BROAD LONGWAVE
TROUGH THAT HAD BEEN CENTERED OVER THE EASTERN BERING OVER THE
WEEKEND THAT IS NOW CENTERED OVER THE EASTERN ALEUTIANS AND
EXTREME NORTH PACIFIC. NUMEROUS SHORTWAVES ALSO CONTINUE TO ROTATE
ALONG THE PERIPHERY OF THE TROUGH. THE MOST SIGNIFICANT OF WHICH
IS MOVING NORTHWARD THROUGH THE GULF AND WILL BRING YET ANOTHER
ROUND OF RAIN AND GUSTY WINDS TO THE GULF COAST TODAY. WELL TO THE
WEST OF THE AREA THE NEXT SYSTEM TO IMPACT THE ALEUTIANS IS
BEGINNING TO COME INTO TO PICTURE JUST SOUTH OF THE KAMCHATKA
PENINSULA. THIS SYSTEM WILL CONTINUE TRACKING TOWARDS THE WESTERN
ALEUTIANS WHERE IT WILL RAPIDLY INTENSIFY LATE TONIGHT. ANOTHER
NOTABLE FEATURE WELL OUTSIDE THE FORECAST AREA IS A DEVELOPING
WAVE NEAR 40N ASSOCIATED WITH HUNDREDS OF LIGHTNING STRIKES. THIS
WAVE WILL LIFT NORTHWARD TOWARDS THE GULF TODAY AS IT
INTENSIFIES...AND BE THE FOCUS FOR WEATHER THROUGHOUT THE GULF AND
SOUTH MAINLAND ON WEDNESDAY AND THURSDAY.

&&

.MODEL DISCUSSION...
SYNOPTIC MODEL AGREEMENT REMAINS GOOD IN THE EARLY TERM...BUT
THEN BEGINS TO BREAK DOWN ON WEDNESDAY AS TWO DEVELOPING SYSTEMS
MOVE INTO THE GULF AND WESTERN ALEUTIANS. THE MODELS HAVE COME
INTO MUCH BETTER AGREEMENT WITH A SLIGHTLY WEAKER LOW MOVING INTO
THE NORTH GULF THIS AFTERNOON...SO THERE IS NOW GOOD CONFIDENCE
THAT WINDS THROUGHOUT THE GULF WILL FALL BELOW GALE FORCE BY THIS
EVENING WITH BETTER AGREEMENT FROM THE HIGHER RESOLUTION MODELS.
THE OTHER CHALLENGE FROM THIS LOW COMES LATE TONIGHT AS THE LOW
MAKES LANDFALL IN PRINCE WILLIAM SOUND...BRINGING A BRIEF CHANCE
OF SNOW TO INLAND SOUTHCENTRAL. THE HIGHER RESOLUTION MODELS ALL
INDICATE THAT DOWNSLOPING WILL LIMIT SNOWFALL SOME SNOWFALL FROM
REACHING LOWER ELEVATIONS...BUT DISAGREE AS TO WHETHER THIS WILL
BE STRONG ENOUGH TO PREVENT LIGHT ACCUMULATION.

MODEL AGREEMENT HAS IMPROVED ENOUGH SINCE YESTERDAY WITH THE NEXT
SYSTEM TO MOVE INTO THE WESTERN ALEUTIANS ON WEDNESDAY
MORNING TO BRING STORM FORCE WINDS TO THE WESTERN
ALEUTIANS. THERE STILL HOWEVER REMAIN SMALL DIFFERENCES WITH
REGARDS TO BOTH TIMING AND INTENSITY...BUT WITH A SIGNIFICANT COLD
POOL AVAILABLE TO TAP INTO OVER EASTERN RUSSIA THE DEEPER EC/GFS
SOLUTIONS WERE PREFERRED FOR THE MORNING PACKAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LOW DEVELOPING ALONG THE FRONT THIS MORNING OVER THE NORTHEAST
GULF WILL MOVE TO THE NORTHWEST TODAY AND WILL SLIDE INLAND OVER
THE KENAI PENINSULA BY EARLY EVENING. PRECIPITATION WITH THIS
SYSTEM WILL SPREAD ACROSS THE AREA FROM THE EAST...WITH THE
HIGHEST CHANCES NEAR THE COAST AND LOWER CHANCES INLAND. AS THE
LOW/UPPER TROUGH CROSSES OVER ANCHORAGE TONIGHT THERE COULD BE A
SOME SNOWFALL...AND PROBABILITIES WERE RAISED TO "LIKELY". SNOW
AMOUNTS (IF ANY) IN THE ANCHORAGE THROUGH MATANUSKA AREAS WILL BE
FAIRLY LIGHT AS THE TROUGH MOVES QUICKLY WEST. AFTER THIS SYSTEM
PUSHES INTO THE SUSITNA VALLEY ON WEDNESDAY IT WILL FALL APART.
SOME LINGERING MOISTURE WILL BE OVER SOUTH CENTRAL ALASKA
WEDNESDAY AND WEDNESDAY NIGHT...BUT WITH VERY LITTLE DYNAMICAL
HELP THE CHANCES OF PRECIPITATION WILL BE LOW.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE MAINLAND LIES ON THE NORTHERN PERIPHERY OF THE CYCLONIC FLOW
ALOFT BRINGING SCATTERED RAIN AND SNOW SHOWERS TO THE GREATER
BRISTOL BAY AREA. THESE SHOWERS WILL DECREASE IN COVERAGE THROUGH
THE DAY AS THE MAIN UPPER LOW PRESSURE SHIFTS SOUTHWARD. OTHERWISE
DRY CONDITIONS WILL REMAIN UNTIL WEDNESDAY AFTERNOON WHEN AN UPPER
TROUGH AND COLD POOL ALOFT WILL BRING SNOW SHOWERS TO MAINLY
COASTAL AREAS OF THE KUSKOKWIM DELTA AREA. TEMPERATURES WILL BE ON
THE COOLER SIDE OF SEASONABLE WHILE WINDS WILL REMAIN LIGHT FROM
THE NORTH KEEPING COLD AIR FLOWING FROM THE INTERIOR.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE DEFORMATION ZONE FROM DUTCH HARBOR TO COLD BAY WILL SLOWLY
SHIFT EASTWARD AND WEAKEN TODAY. STEADY RAIN CAN BE EXPECTED IN
THESE AREAS...WITH THE POSSIBILITY OF SNOW MIXING IN AT TIMES.
BEHIND THAT FRONT...A COLD AIR MASS WILL BRING A SHOWERY REGIME TO
MUCH OF THE BERING SEA THROUGH THURSDAY. THE MORE IMPACTFUL
FEATURE IS A DEVELOPING LOW PRESSURE SYSTEM OFF OF THE WESTERN
ALEUTIANS. THIS SYSTEM WILL SWING A STORM FORCE FRONT OVER THE
WESTERN BERING BRINGING SNOW...CHANGING TO RAIN DURING THE DAY ON
WEDNESDAY. THIS FRONT WILL SLOWLY WEAKEN OVER THE CENTRAL AND
EASTERN BERING BY THURSDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

BEGINNING THE EXTENDED PERIOD ON THURSDAY...A LONGWAVE TROUGH
WILL EXIST OVER THE NORTH PACIFIC EXTENDING INTO THE SOUTHERN GULF
OF ALASKA WITH A DEEP WARM SECLUSION CYCLONE OVER THE FAR WESTERN
BERING SEA AND ALEUTIANS. SHORTWAVE RIDGING WILL EXIST OVER THE
EASTERN BERING WITH ANOTHER OVER SOUTHCENTRAL ALASKA. INLAND
SHOWERS ACROSS SOUTHCENTRAL WILL BE IN THE PROCESS OF DIMINISHING
WITH RAIN AND SNOW SHOWERS MAINLY IMPACTING THE COAST. WITH
TIME...THE DEEP BERING CYCLONE WILL MOVE EAST AND TAP THE NORTH
PACIFIC...WITH A DEEP LOW FORMING SOMEWHERE ACROSS THE CENTRAL OR
EASTERN GULF OF ALASKA. THERE IS MUCH UNCERTAINTY WITH THE TRACK
AND STRENGTH OF THIS LOW FRIDAY THROUGH SATURDAY...BUT MOST OF THE
IMPACTS WILL BE OVER THE MARINE WATERS AS STRONG EASTERLY FLOW
ALOFT AND OFFSHORE FLOW IN THE LOW LEVELS WILL KEEP INLAND
LOCATIONS LARGELY DRY. THEREAFTER...THE NORTH PACIFIC JET BECOMES
HIGHLY ACTIVE AND VOLATILE...WITH THE MAIN BRUNT OF ENERGY
IMPACTING THE BRITISH COLUMBIA COAST TO THE PANHANDLE OF
ALASKA...KEEPING SOUTHCENTRAL UNDER THE INFLUENCE OF WEAKER LOWS
EJECTING OF THE STRONG JET STREAM INTO THE GULF OF ALASKA. ONCE
AGAIN...THIS PATTERN TENDS TO FAVOR A GENERAL DOWNSLOPE FLOW
SIGNATURE WITH PRECIPITATION. HOWEVER...WITH A CONTINUED OFFSHORE
PRESSURE GRADIENT WITH THE STRONG ARCTIC HIGH TO THE
NORTH...TEMPERATURES SHOULD NOT MOVE TOO FAR AWAY FROM NORMAL EVEN
UNDER THE INFLUENCE OF STRONG CROSS BARRIER FLOW. BY EARLY TO MID
NEXT WEEK...THERE ARE HINTS THAT A SERIES OF TROUGHS WILL INTERACT
WITH THE COLD ARCTIC TROUGH OVER THE BERING SEA...ADVECTING COLDER
AIR INTO SOUTHCENTRAL BY MIDWEEK...AND POSSIBLY BRINGING INCREASED
SNOW CHANCES AS WELL. HOWEVER...FOR THE TIME BEING...STORMINESS
WILL REMAIN FAR TO THE SOUTH OF THE REGION...WITH THE GENERAL
PATTERN OF COASTAL SHOWERS AND LARGELY DRY CONDITIONS INLAND
LASTING INTO THE WEEKEND BEFORE UNCERTAINTY ARISES BY EARLY NEXT
WEEK.

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE
MARINE...STORM WARNING 178
 		 GALE WARNING 119 120 130 131 139 155 165 170 171 172
					  175 176 177 179

&&

SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL
LONG TERM...JA