Small Craft Advisory 858, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
512 AM AKDT THU OCT 30 2014

.ANALYSIS AND UPPER LEVELS...
MOSTLY CLOUDY SKIES PREVAIL ACROSS THE SOUTHERN HALF OF THE
MAINLAND THIS MORNING BENEATH CYCLONIC FLOW ALOFT WITHIN A
LONGWAVE TROUGH THAT EXTENDS FROM THE ARCTIC INTO THE NORTHEAST
PACIFIC. A WEAK UPPER WAVE ROTATING NORTHWESTWARD THROUGH THE GULF
IS BRINGING SNOW SHOWERS TO PORTIONS OF THE GULF COAST AND THE
COPPER RIVER BASIN...WITH SOME RAIN MIXING IN NEAR CORDOVA. OUT
WEST...A WEAKENING FRONT POSITIONED OVER THE EASTERN BERING
SEA IS SPREADING RAIN AND GUSTY SOUTHEASTERLY WINDS FROM DUTCH
HARBOR AND THE PRIBILOFS TO THE ALASKA PENINSULA. A DEVELOPING
NORTH PACIFIC LOW WELL SOUTH OF THE WESTERN ALEUTIANS IS POISED
TO RAPIDLY STRENGTHEN TODAY BENEATH THE LEFT EXIT REGION OF A 130
KNOT JET STREAK AS IT TRACKS NORTHWARD INTO THE BERING....BRINGING
MORE RAIN AND A WIDE SWATH OF STORM FORCE WINDS TO MUCH OF THE
ALEUTIAN CHAIN.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO STRUGGLE WITH THE HANDLING OF THE RAPIDLY
DEEPENING LOW AS IT TRACKS INTO THE BERING SEA TODAY...WITH
SIGNIFICANT DISCREPANCIES ON THE ORDER OF APPROXIMATELY 400 MILES
EMERGING IN THE POSITION OF THE LOW BY THE 36 HOUR MARK IN THE
FORECAST. THE EC AND GFS HAVE ESSENTIALLY TRADED POSITIONS OVER
THE PAST 24 HOURS...WITH THE GFS NOW FARTHER TO THE EAST AND THE
EC REPRESENTING THE WESTERNMOST SOLUTION AND CONTINUING TO TREND
IN THAT DIRECTION WITH THE 12Z RUN THIS MORNING. THE NAM IS
CONSIDERED AN OUTLIER AS IT IS MUCH FARTHER EAST THAN ANY OF THE
OTHER GUIDANCE. THEREFORE...ENDED UP MAINLY UTILIZING THE GEM FOR
THE SHORT TERM FORECAST AS IT DEPICTS A MORE ELONGATED LOW WHICH
SERVES AS SOMEWHAT OF A MIDDLE GROUND SOLUTION BETWEEN THE EC AND
GFS. THE GEM HAS ALSO DISPLAYED A SUPERIOR HANDLING OF PRESSURE
GRADIENTS OVER THE EASTERN HALF OF THE FORECAST DOMAIN FOR THE
PAST SEVERAL DAYS.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
RELATIVELY BENIGN CONDITIONS WILL PERSIST THROUGH THE END OF THE
WORK WEEK AS TROUGHING OVER THE NORTHERN GULF KEEPS A FEW RAIN
AND SNOW SHOWERS CONFINED MAINLY TO THE GULF COAST AND EASTERN
COPPER BASIN WITH CLEARING SKIES INLAND. GUSTY OUTFLOW WINDS WILL
ONCE AGAIN BEGIN TO STRENGTHEN TODAY IN RESPONSE TO THE INCREASING
PRESSURE GRADIENT. A GREATER CHANCE FOR MORE WIDESPREAD PRECIPITATION
WILL RETURN FRIDAY NIGHT INTO SATURDAY AS THE FRONT ASSOCIATED
WITH THE BERING LOW REACHES THE GULF COAST...ALTHOUGH IT APPEARS
DOWNSLOPING OFF THE CHUGACH RANGE MAY KEEP ANCHORAGE AND THE
MATANUSKA VALLEY MOSTLY DRY THROUGH THE WEEKEND.

SOUTHWEST ALASKA...
DRY NORTHERLY FLOW WILL YIELD PREDOMINANTLY CLEAR SKIES OVER THE
SOUTHWEST MAINLAND INTO THE DAY ON FRIDAY BEFORE THE FRONT ARRIVES
ALONG THE COAST...BRINGING A CHANCE OF SNOW TO PORTIONS OF BRISTOL
BAY IN THE AFTERNOON BEFORE SPREADING INLAND OVERNIGHT AND INTO
THE WEEKEND.

BERING SEA/ALEUTIANS...
THE DOMINANT FEATURE IN THE BERING FOR THE NEXT SEVERAL DAYS WILL
BE THE POWERFUL LOW WHICH WILL PASS WEST OF ADAK LATER THIS
AFTERNOON AS IT RAPIDLY INTENSIFIES INTO THE MID 960 MB RANGE.
THIS SYSTEM WILL BRING ABUNDANT RAINFALL TO A LARGE PORTION OF THE
BERING...BUT THE MAIN CONCERN OVER THE COMING DAYS WILL BE STRONG
WINDS ALONG THE ALEUTIAN CHAIN AND INTO THE PRIBILOF ISLANDS.
DESPITE THE SIGNIFICANT MODEL DISAGREEMENT MENTIONED PREVIOUSLY
WITH REGARD TO THE POSITION OF THE LOW...IT APPEARS THAT THE LOW
WILL REMAIN FAR ENOUGH NORTH OF THE CHAIN THAT THE ISLANDS WILL
NOT BE DIRECTLY IMPACTED BY THE STRONGEST WINDS DEVELOPING ON THE
SOUTHERN FLANK OF THE SYSTEM. ADDITIONALLY...THE LACK OF COLD AIR
ADVECTION SHOULD HELP TO LIMIT THE POTENTIAL FOR THE STRONGEST
WINDS TO MIX DOWN TO THE SURFACE. THEREFORE...THE HIGH WIND WATCH
FOR THE CENTRAL AND WESTERN ALEUTIANS HAS BEEN CANCELLED AND THERE
IS INCREASED CONFIDENCE THAT WINDS OVER THE SURROUNDING COASTAL
ZONES WILL NOT REACH HURRICANE FORCE. REGARDLESS...MUCH OF THE
CHAIN WILL STILL BE IMPACTED BY STRONG WESTERLY WINDS THROUGH
FRIDAY AS THE LOW TRACKS EASTWARD TOWARDS THE AKPEN...WITH A LARGE
SWATH OF STORM FORCE WINDS COVERING THE CENTRAL ALEUTIANS/BERING
AND GALE FORCE WINDS ENCOMPASSING MUCH OF THE REST OF THE AREA.

&&

.LONG TERM FORECAST...
THE BERING LOW IS NOW EXPECTED TO ENTER THE GULF EARLY NEXT WEEK
AND BECOME NEARLY STATIONARY THROUGH MID WEEK. THIS SETUP WOULD
KEEP A CHANCE OF PRECIPITATION AND OUTFLOW WINDS FOR THE GULF
COAST WITH GENERALLY A GENERALLY DRY CONDITIONS AND OFFSHORE FLOW
FOR SOUTHCENTRAL.

ONCE THE SYSTEM IN THE GULF BEGINS TO DISSIPATE EARLY NEXT
WEEK...THE LONG TERM FORECAST QUICKLY SHIFTS TO A FRONT ASSOCIATED
WITH A SIBERIAN LOW MOVING INTO THE WESTERN ALEUTIANS EARLY NEXT
WEEK. AN ENSEMBLE BLEND WAS USED AGAIN FOR THIS SYSTEM...THOUGH
THERE IS REASONABLY GOOD AGREEMENT FROM THE OPERATIONAL MODELS
WITH MINOR TIMING DIFFERENCES. THE SIBERIAN LOW IS STILL PROJECTED
TO SPREAD INTO THE BERING OVER THE COURSE OF THE NEXT
WEEK...DOMINATING THE WEATHER OVER THE BERING SEA AND ALEUTIANS
NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE
MARINE...STORM WARNING 173 174 175 176 177 412 413
         GALE WARNING 130 131 150 155 165 170 172 178 179 180 181
			  	      185 411 414
FIRE WEATHER...NONE

&&

CB/DEK OCT 14