Small Craft Advisory 170, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST TUE FEB 25 2014

.ANALYSIS AND UPPER LEVELS...

LARGE SCALE TROUGHING PERSISTS FROM THE WESTERN ALEUTIANS SOUTH AND
EAST INTO THE PACIFIC WELL SOUTH OF MAINLAND ALASKA. HIGHLY AMPLIFIED
RIDGING PERSISTS FROM THE CANADIAN ROCKIES NORTH AND WEST INTO THE
ALCAN BORDER REGION. IN BETWEEN THE TWO...INCREASING SOUTHEAST FLOW
PERSISTS...STRONGEST FROM THE NORTHEAST PACIFIC EXTENDING NORTH AND
WEST INTO THE KODIAK ISLAND TO ALASKA PENINSULA REGION...WITH
SLIGHTLY WEAKER SOUTH-SOUTHERLY UPPER FLOW PUSHING THROUGH THE BERING
AND SOUTHWEST MAINLAND AND ALSO OVER SOUTHCENTRAL ALASKA CLOSER TO
THE RIDGE AXIS.

A 967 MB LOW IS OBSERVED WELL SOUTH OF 50N 150W MOVING NORTH AND WEST
TOWARD THE ALASKA PENINSULA...BUT AN ASSOCIATED FRONTAL BOUNDARY
EXTENDS WELL NORTH AND WEST OF THE LOW AND SHOULD BEGIN TO IMPACT
PARTS OF THE SOUTHWEST...SOUTHERN AND EASTERN BERING...AND WESTERN
GULF TODAY THROUGH THURSDAY AS THE SURFACE LOW WEAKENS AND MOVES INTO
THE CENTRAL BERING SEA.

.MODEL DISCUSSION...

MODELS ARE IN GOOD AGREEMENT THROUGH WEDNESDAY NIGHT...EXCEPT FOR THE
NAM WHICH IS A NORTHERLY OUTLIER WITH QPF ASSOCIATED WITH THE FRONT
IN THE GULF...AND THUS IS DISCOUNTED FOR NOW IN FAVOR OF THE GFS AND
EC SOLUTIONS. HOWEVER...IF THE NAM WERE TO BE CORRECT THE EASTERN
KENAI PENINSULA WOULD SEE MUCH HEAVIER PRECIPITATION AMOUNTS
ESPECIALLY FROM MOOSE PASS TO SEWARD...RESULTING IN THE POTENTIAL FOR
HEAVY WET SNOW FOR AN EXTENDED PERIOD WEDNESDAY INTO THURSDAY.

BY THURSDAY AND FRIDAY...MODELS REMAIN IN GOOD AGREEMENT WITH
PRINCIPAL CIRCULATION FEATURES...BUT DIFFER ON SPEED AND STRENGTH OF
SHORTWAVE DISTURBANCES MOVING NORTH AND WEST FROM THE NORTHEAST
PACIFIC INTO THE SOUTHERN MAINLAND. THIS PRIMARILY IMPACTS THE
FORECAST IN TIMING AND STRENGTH OF ASSOCIATED PRECIPITATION AS THIS
SYSTEM PASSES.

.SHORT TERM FORECAST...

SOUTHCENTRAL...

PATCHY FOG DEVELOPED THIS MORNING IN THE COPPER RIVER BASIN...WITH
SKIES BEGINNING TO CLEAR THERE THIS AFTERNOON. PERHAPS THE BIGGEST
QUESTION MARK FOR THE AFTERNOON FORECAST IS DETERMINING WHETHER THE
NAM HAS A GOOD HANDLE ON DEVELOPING AN IFR DECK OF OVERRUNNING
STRATUS WITH FLURRIES AS WEAK WARM ADVECTION BEGINS JUST ABOVE THE
COLD LOW-LEVEL INVERSION...WHICH COULD PERSIST FOR A FEW DAYS IF THIS
VERIFIES. WILL HEDGE IN THE DIRECTION OF THE STRATUS DEVELOPING LATER
THIS AFTERNOON WITH FLURRIES DEVELOPING MAINLY TONIGHT BUT PERHAPS
PERSISTING INTO TOMORROW AS WELL.

OTHERWISE...BIG CONCERN IS WITH THE FRONT MOVING NORTH THROUGH THE
GULF. EXPECTING LOCALLY HEAVY RAIN TONIGHT FOR KODIAK ISLAND...BUT
THERE SHOULD NOT BE ANY FLOODING/LANDSLIDE CONCERNS GIVEN THE BREVITY
OF HEAVY RAIN ON ANY ONE LOCATION. PRECIPITATION ALSO SPREADS NORTH
INTO THE SOUTHERN KENAI PENINSULA LATE TONIGHT AND PERSISTS INTO
THURSDAY. OUTSIDE OF SOME UPSLOPE FLOW PERHAPS GENERATING WET SNOW ON
THE EASTERN SIDE OF THE PENINSULA...PRECIPITATION SHOULD BE IN THE
LIQUID FORM AS VERY WARM AIR ALOFT CONTINUES TO MOVE TOWARD
SOUTHCENTRAL. THE TRICKY PART OF THE FORECAST WILL BE FIGURING OUT IF
ANY LOCALIZED COLD POCKETS OF BELOW-FREEZING TEMPERATURES REMAIN
ESPECIALLY LATE TONIGHT THROUGH THURSDAY WHERE RAIN MAY
RE-FREEZE...ESPECIALLY IN SHELTERED VALLEYS THROUGH THE KENAI RANGE
ALONG THE ROAD SYSTEM. ANCHORAGE AND POINTS NORTH WILL LIKELY REMAIN
DRY...BUT BEGINNING WEDNESDAY MORNING WE CAN NOT RULE OUT A PERIOD OF
LIGHT PRECIPITATION.

AS FOR WINDS...HAVE UPPED MARINE WINDS FOR THE INNER WATERS AREA FOR
LATE THIS AFTERNOON AND EVENING...WITH STORM FORCE WINDS EXPECTED FOR
THE BARREN ISLANDS AND KAMISHAK BAY REGIONS AS WELL AS SHELIKOF
STRAIT.

WILL CONTEMPLATE ISSUING A SPECIAL WEATHER STATEMENT FOR MUCH WARMER
TEMPERATURES CAUSING MELTING AND RE-FREEZING OF SIDE ROADS AROUND
ANCHORAGE BEGINNING WEDNESDAY AFTERNOON THROUGH FRIDAY GIVEN THE
EXPECTED RISE OF TEMPERATURES INTO THE 30S TO LOWER 40S. NIGHTTIME
LOWS SHOULD ALSO REMAIN NEAR OR ABOVE FREEZING BUT WITH COLD ROAD
TEMPERATURES ON SIDE STREETS THESE AREAS WILL LIKELY RE-FREEZE EACH
NIGHT WITH BLACK ICE.

SOUTHWEST...

PRECIPITATION WILL OVERSPREAD THE SOUTHWEST MAINLAND...WITH MUCH LESS
IF ANY MEASURABLE PRECIPITATION IN THE LEE OF THE ALEUTIAN RANGE.
STILL EXPECTING SOME SNOW INITIALLY TOWARD DILLINGHAM AND POINTS
NORTH AND WEST TONIGHT...THEN GRADUALLY CHANGING OVER TO RAIN...WITH
A CHANCE OF FREEZING RAIN IF TEMPERATURES ARE TOO SLOW TO WARM AS
MUCH WARMER AIR MOVES IN ALOFT. THE SAME CONCERN EXISTS FOR BETHEL
WITH WARM AIR MOVING OVERHEAD THERE AS WELL. THE TYPICALLY STRONG
EAST TO NORTHEAST WINDS ARE EXPECTED FOR THE SOUTHWEST MAINLAND UNTIL
THE LOW PASSES BY TO THE SOUTH AND WEST LATE THURSDAY.

BERING SEA/ALEUTIANS...

RAIN AND SNOW WILL GRADUALLY CHANGE OVER TO ALL RAIN AS TEMPERATURES
WARM FROM EAST TO WEST AS AN OCCLUDED FRONT MOVES WEST AHEAD OF THE
SURFACE LOW. EXPECT MINIMAL...IF ANY...SNOW ACCUMULATIONS. BY
THURSDAY THROUGH RAIN/SNOW LINE WILL BE NEAR OR WEST OF THE PRIBILOFS
AND DUTCH HARBOR. ISOLATED TO SCATTERED SNOW SHOWERS WILL PERSIST
ACROSS THE CENTRAL AND WESTERN ALEUTIANS THROUGH AT LEAST WEDNESDAY.

.LONG TERM FORECAST...

LITTLE CHANGE IN LONG TERM FORECAST THINKING. UPPER HIGH/RIDGE STILL
LOOKING DOMINANT NEAR THE ALCAN BORDER...ALBEIT SOME DEGREE OF
RETREAT IS POSSIBLE AS ENERGY WORKS AGAINST IT FROM THE WEST. DETAILS
ON HOW THIS OCCURS WILL BE AMONG THE FORECAST CHALLENGES IN THE
AOR...BUT SUFFICE TO SAY BLOCKED PATTERNS TEND TO TAKE LONGER TO
BREAK. PERIPHERAL EFFECTS FROM A DEEPENING SYSTEM MOVING AWAY FROM
JAPAN WILL BE EXPERIENCED OVER THE ALEUTIAN CHAIN LATE WEEK INTO THE
WEEKEND...AND POSSIBLY AS FAR EAST AS KODIAK ISLAND. THIS SYSTEM WILL
HAVE REACHED IT'S PEAK INTENSITY AND BE FILLING AS THIS OCCURS
THOUGH...AND FOLLOW UP LOWS/WAVES APPEAR TO BE CONSIDERABLY WEAKER
THAN THIS INITIAL ONE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES...120 136 137 139 150 155 160 165 180
         STORMS...130 131 132 138
         HVY FRZG SPRY...NONE.
FIRE WEATHER...NONE.

CC FEB 14

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
430 PM AKST TUE FEB 25 2014

AKZ101-111-121-145-261200-

...SIGNIFICANT WARM-UP EXPECTED WEDNESDAY THROUGH THE WEEKEND FOR
PARTS OF SOUTHCENTRAL ALASKA...

A SURGE OF WARM AIR FROM THE SOUTHEAST WILL HELP PUSH DAYTIME
TEMPERATURES INTO THE 30S TO LOWER 40S WEDNESDAY THROUGH THIS WEEKEND
ACROSS THE COOK INLET REGION. AS A RESULT...THERE WILL BE
CONSIDERABLE MELTING OF SNOW AND ICE EACH DAY. HOWEVER...THE GROUND
WILL REMAIN COLD ENOUGH THAT ANY WATER ON AREA ROADS WILL LIKELY
RE-FREEZE AT NIGHT.

PEDESTRIANS AND DRIVERS ARE ENCOURAGED TO TAKE EXTRA PRECAUTIONS ON
SIDEWALKS AND ROADS AS TO AVOID SLIPPING ON BLACK ICE THROUGH THE
WEEKEND.

CASSELL/DIXON