Small Craft Advisory 202, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
525 AM AKST FRI MAR 6 2015

.ANALYSIS AND UPPER LEVELS...

A LARGE PROGRESSIVE ZONAL FLOW RESIDES OVER OUR CORNER OF THE
HEMISPHERE THIS MORNING...EXTENDING FROM THE WESTERN BERING TO THE
CANADIAN ROCKIES. A RAPIDLY MOVING UPPER TROUGH HAS REACHED THE
ALCAN. A LARGE UPPER LOW IS OVER SIBERIA AND...IN CONJUNCTION WITH
A RIDGE EXTENDING FROM THE NORTH PACIFIC TO THE AKPEN...IS
RESULTING IN A 160 KT JET OVER THE WESTERN BERING. AT THE
SURFACE...REMNANTS OF A WEAK FRONT ARE MOVING ACROSS THE COPPER
RIVER BASIN INTO CANADA. WEAK RIDGING IS OVER SW AK WITH SOME
AREAS OF FOG. THE NEXT FRONT...ASSOCIATED WITH THE 160 KT JET...IS
RAPIDLY MOVING ONSHORE OVER WESTERN AK AND THE AKPEN WITH SOME
SNOW OVER THE MAINLAND...AS WELL AS DRAGGING ACROSS THE EASTERN
HALF OF THE ALEUTIANS WITH RAIN.

&&

.MODEL DISCUSSION...

POSITIONALLY THE MODELS ARE IN VERY GOOD AGREEMENT INTO SUN. THE
FRONT WILL MOVE ACROSS WESTERN AK TODAY AND INTO SOUTHCENTRAL
TONIGHT BEFORE EXITING THE STATE LATER ON SAT. COLDER AIR WILL
FOLLOW THE FRONT INTO WESTERN AK TONIGHT AND INTO SOUTHCENTRAL ON
SAT. THE MODEL DIFFERENCES ARE SUBTLE AND RELATE TO TEMPERATURE
PROFILES IN THE ATMOSPHERE ASSOCIATED WITH THE FRONT NOW ENTERING
AK. SOME ARE RUNNING COLD AND AND ARE INDICATING A SIGNIFICANT
SNOW EVENT FOR THE MAINLAND ZONES...WHILE OTHERS ARE A BIT WARMER
WITH SNOW BEING MORE LIMITED IN COVERAGE. MORNING TEMPERATURE
PROFILES ARE LEANING TOWARD THE SLIGHTLY WARMER SOLUTION AND THE
FORECASTS HAVE BEEN ADJUSTED TO THE WARMER GFS SOLUTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
LINGERING LOW LEVEL MOISTURE BEHIND THE DEPARTING SYSTEM WILL
PROMOTE SOME FOG DEVELOPMENT EARLY THIS MORNING BEFORE SOME
PARTIAL CLEARING IN THE AFTERNOON. LATE THIS EVENING ATTENTION
TURNS TO AN APPROACHING JET AND DISTURBANCE FROM THE SOUTHWEST
MAINLAND. THE FRONT WILL SPREAD PRECIPITATION FROM THE COOK INLET
REGION NORTHWARD TO THE ALASKA RANGE WITH HIGH
CONFIDENCE...HOWEVER WITH THIS SYSTEM LIKE THE
PREVIOUS...PRECIPITATION TYPE WILL BE A BIG QUESTION. THE BEST
CHANCES TO FOR PREDOMINANT SNOW WILL BE IN THE SUSITNA VALLEY.
SOUTHEASTERLY WIND COMING THROUGH TURNAGAIN ARM AND KNIK ARM WILL
BRING NEAR SURFACE TEMPERATURE INTO THE MID 30S INCREASING THE
POTENTIAL FOR RAIN AS THE PREDOMINANT PRECIPITATION TYPE...THOUGH
PRECIPITATION INTENSITY COULD DRAG DOWN COLDER AIR AND MIX WITH OR
CHANGE TO SNOW AT TIMES. ALONG THE HILLSIDE PRECIPITATION SHOULD
REMAIN ALL SNOW WHERE THE BEST CHANCES EXIST FOR DECENT
ACCUMULATIONS. COLD ADVECTION WILL KICK IN SATURDAY MORNING AND
CHANGE THE TYPE BACK TO SNOW FOR MOST LOCATIONS BEFORE TAPERING
OFF IN THE MORNING. SCATTERED SNOW SHOWERS WILL REMAIN POSSIBLE
AROUND COOK INLET AND THE SUSITNA VALLEY ON SATURDAY
AFTERNOON/EVENING AS THE UPPER TROUGH PUSHES THROUGH BEGINNING A
COLDER PATTERN.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
AREAS OF FOG WILL BE A CONCERN AGAIN TONIGHT UNDER THE FLAT RIDGE
SLIDING QUICKLY ACROSS SOUTHWEST ALASKA AHEAD OF THE INCOMING
FRONTAL SYSTEM. WITH RATHER STRONG WESTERLY 500 MB AND SSW 850 MB
JET SUPPORT ALL LOOKS GOOD FOR SOME RATHER SIGNIFICANT QPF AMOUNTS
AS THE FRONTAL SYSTEM PUSHES INLAND FRIDAY AND FRIDAY NIGHT.

BLOWING SNOW WILL BE THE PRIMARY CONCERN FOR THE KUSKOKWIM DELTA
AS STRONG SOUTH THEN SOUTHWEST WINDS SHOULD MAKE IT A WAYS
INLAND...HOWEVER SNOWFALL AMOUNTS WILL BE A BIT MORE MODEST WITH
THE FAST MOVING NATURE OF THE SYSTEM. FOR THE LOWER KUSKOKWIM
VALLEY AND NORTHERN BRISTOL BAY AREAS...SNOW AMOUNTS WILL BE
HIGHER ESPECIALLY IN AREAS UPSLOPE AREAS FAVORED BY THE SSW LOWER
LEVEL WINDS. BLOWING SNOW WILL ALSO BE A CONCERN IN THE NORTHERN
INLAND PORTIONS OF THE BRISTOL BAY ZONE WHERE S TO SW WINDS WILL
FUNNEL AND TEMPERATURES WILL REMAIN COOLER. FROM DILLINGHAM SOUTH
PRECIPITATION MAY BEGIN WITH A COUPLE INCHES OF HEAVY WET SNOW BUT
SHOULD CHANGE OVER TO A MIX OF RAIN AND SNOW FRIDAY EVENING OR ALL
RAIN FURTHER SOUTH.

A MUCH COOLER AND SHOWERY AIR MASS WILL BEGIN PUSHING INTO THE
AREA ON SATURDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A RATHER STRONG FRONTAL SYSTEM WILL CROSS THE AREA FROM WEST TO
EAST BRINGING WIDESPREAD GALES TO THE ALEUTIANS AND BERING AS
WELL AS AN AREA OF STORMS TO WEST AND CENTRAL BERING OFFSHORE
WATERS. A MUCH COLDER AIR MASS WILL PUSH OVER THE BERING FRIDAY
NIGHT AND SATURDAY WITH SURFACE HIGH PRESSURE BUILDING.

&&

.LONG TERM FORECAST (DAYS 4 THROUGH 7)...
THE UPPER LEVEL WAVE THAT IS EXPECTED TO BRING SIGNIFICANT
PRECIPITATION TO MUCH OF THE SOUTHERN MAINLAND ON SATURDAY WILL
CONTINUE TO BRING WIDESPREAD PRECIPITATION TO AREAS EAST OF
ANCHORAGE THROUGH SUNDAY MORNING. SHOWERS WILL STILL REMAIN IN THE
AREA INTO SUNDAY EVENING AS A BROAD UPPER LEVEL TROUGH SLOWLY
MOVES THROUGH THE MAINLAND.

ON MONDAY...THERE REMAINS VERY GOOD AGREEMENT THAT COLD AIR WILL
SPREAD THROUGHOUT THE SOUTHERN MAINLAND WITH CLEARING SKIES THAT
WILL CONTINUE AT LEAST INTO THE MIDDLE OF NEXT WEEK. PRECIPITATION
IN THIS PATTERN WILL BE CONFINED MAINLY TO THE GULF COAST AS A
SERIES OF WEAK LOWS MOVE THROUGH THE GULF...WHICH WILL ALSO HELP
CREATE GUSTY OUTFLOW WINDS THAT WILL PERSIST THROUGH THE MIDDLE OF
NEXT WEEK. OVER THE ALEUTIANS...THERE IS INCREASING CONFIDENCE
THAT A NORTH PACIFIC LOW WILL MOVE INTO THE WESTERN ALEUTIANS ON
SUNDAY EVENING...AND SLOWLY TRACK EASTWARD BEFORE RETREATING BACK
TO THE NORTH PACIFIC ON WEDNESDAY. THIS WILL KEEP THE BULK OF THE
PRECIPITATION AND WIND FROM THIS SYSTEM CONFINED TO THE ALEUTIAN
ISLANDS...WITH SHOWERS FOR THE REMAINDER OF THE BERING SEA AND
AKPEN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING 145.
WINTER WEATHER ADVISORY 101 111 141 152 155 161
MARINE...GALE 145 176 179 181.
HEAVY FREEZING SPRAY 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...MTL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC