Small Craft Advisory 234, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT TUE MAR 18 2014

.ANALYSIS AND UPPER LEVELS...
A FILLING UPPER-LOW IS MEANDERING OVER THE N TO NE GULF OF AK AND
DRIFTING EASTWARD. RESIDUAL SNOW SHOWERS ASSOCIATED WITH IT ARE
ENDING ACROSS COASTAL AREAS AS DRY OFF-SHORE FLOW INCREASES IN IT'S
WAKE. WINDS ARE INCREASING THROUGH THE TYPICAL GAPS OF PRINCE WILLIAM
SOUND AND THE KENAI PENINSULA AS THIS OCCURS. INCREASING OFF-SHORE
FLOW IS ALSO UNDERWAY OVER KODIAK ISLAND WITH CLOUDS BEGINNING TO
SCOUR OUT A BIT. AN UPPER-LVL RIDGE IS BUILDING NE THROUGH THE E
BERING AND AKPEN BEHIND THE GULF UPPER-LOW. THE LAST VESTIGES OF
SHORTWAVE ENERGY SUPPORTING SOME LIGHT SNOW OVER BRISTOL BAY IS
EJECTING SE AND WEAKENING AS THE UPPER RIDGE ADVANCES. FURTHER
WEST...A 983 MB LOW CENTERED 300 MI S OF ADAK IS MOVING EAST. AN
ASSOCIATED FRONT IS INCHING NORTHWARD SLOWLY THROUGH THE CENTRAL
CHAIN WITH SOME STORM FORCE WINDS AND A SLUG OF SNOW/RAIN. ANOTHER
LOW 200 MI NW OF ATTU IS MOVING NORTH WHILE CLIPPING THE FAR WESTERN
CHAIN WITH SOME LIGHT SNOW/RAIN. ALSO OF NOTE IS A LOW 1000 MI W OF
ATTU APPROACHING THE AOR.

.MODEL DISCUSSION...
MODELS CAPTURE THE MAIN WEATHER FEATURES AND RESULTANT SENSIBLE
WEATHER REASONABLY WELL WITH ADEQUATE AGREEMENT. THE UPPER-LOW/ENERGY
OVER THE NE GULF IS DEPICTED LURKING IN PLACE INTO THU. THE
UPPER-RIDGE BEHIND IT BUILDS NE TO ENCOMPASS MORE OF THE SW MAINLAND
WITH TIME...WITH AN UPPER-HIGH CENTER BEING PINCHED OFF IN THE
VICINITY OF NUNIVAK ISLAND WED NIGHT. THIS UPPER HIGH CENTER IS THEN
SHOWN POKING NORTH TO THE BERING STRAIT THROUGH FRI. THE PACIFIC LOW
S OF ADAK MOVES TO AROUND 250 MI S OF KODIAK ISLAND ON THU AND THEN
TO FAR SE REACHES OF THE GULF OF AK ON FRI. THIS FEATURE HELPS TO
PINCH OFF THAT UPPER HIGH BY UNDERCUTTING IT WHILE THE UPPER-LOW IN
THE GULF REMAINS SOMEWHAT STATIONARY...FORCING THE GENERAL RIDGE/HIGH
NORTHWARD. MODELS DO SHOW THAT SOME RESIDUAL ENERGY FROM THE NE GULF
UPPER-LOW WILL DEFLECT TO THE WEST TO FILL THE VOID LEFT BY THE HIGH
CENTER MOVING AWAY FROM THE AOR. THE ECMWF IS MOST AGGRESSIVE WITH
THIS DEVELOPMENT SHOWING A NEW UPPER-LOW FORMING IN THE VICINITY OF
KODIAK ISLAND ON THU THAT TRACKS TOWARDS THE E BERING SEA FRI.
FURTHER WEST...THE LOW WELL W OF ATTU IS DEPICTED MOVING TO AROUND
150 MI S OF SHEMYA IN THE MID 980S RANGE ON THU THEN BECOMING
INCREASINGLY ELONGATED AND COMPLEX AS IT MOVES TO AROUND 300 MI S OF
UNALASKA ON FRI.

.SHORT TERM FORECAST...
SOUTHCENTRAL/GULF...
RELATIVELY BENIGN AND DRY WEATHER ANTICIPATED FOR THE SOUTHERN
MAINLAND IN THE COMING DAYS DUE TO THE ABSENCE OF ANY STRONG WEATHER
FEATURES BRINGING ANY SIGNIFICANT MOISTURE TO THE REGION. THERE IS A
LOW PROBABILITY THREAT OF SOME FOG DEVELOPMENT TONIGHT ACROSS UPPER
COOK INLET AREAS...BUT THE ATMOSPHERE IS STILL LEANING ON THE
UNSTABLE SIDE AND THE MORE LIKELY SCENARIO IS SOME PATCHY LOW CLOUDS
AT TIMES. OVERALL ANTICIPATING RESPECTABLE AMOUNTS OF SUNSHINE. THE
GAP WINDS ALONG THE NORTHERN GULF COAST WILL PEAK IN STRENGTH TONIGHT
THROUGH WED AS THE PRESSURE GRADIENT IS AT IT'S STRONGEST AND WINDS
WILL BE AIDED BY A SERIES OF SUBTLE DISTURBANCES ALOFT PINWHEELING
AROUND THE PARENT UPPER-LOW. THROUGH THOMPSON PASS...REDUCED
VISIBILITY AT TIMES IN BLOWING SNOW IS A THREAT DUE TO THE
AVAILABILITY OF LIGHTWEIGHT TRANSPORTABLE SNOW (EXCESS OF 1 FOOT).
WINDS WILL GRADUALLY WEAKEN ON THU...BUT NOT GO AWAY COMPLETELY AS
LONG AS THERE ARE HINTS OF A LOW IN THE GULF OF AK. KODIAK ISLAND
SHOULD REMAIN ON THE DRY SIDE AS WELL CHARACTERIZED BY DECREASED
CLOUDINESS IN THE OFF-SHORE FLOW THROUGH WED NIGHT. ON THU...SOME OF
THE RESIDUAL UPPER-LOW GULF ENERGY OVER THE N TO NE GULF WILL ADVANCE
AND BRING SOME MOISTURE AND LIFT WITH IT. THIS WILL ONCE AGAIN RESULT
IN CLOUDS AND PERIODS OF PRECIPITATION...ALBEIT ON THE LIGHT SIDE.

SOUTHWEST/AKPEN...
INCREASED ANTI-CYCLONIC FLOW ALOFT IN STORE FOR SW AK AS THE UPPER
RIDGE/HIGH RUN THEIR COURSE SUPPORTING SURFACE HIGH PRESSURE. SOME
LIGHT SNOWS ARE HANGING ON EARLY THIS EVENING OVER EASTERN BRISTOL
BAY...BUT THIS SHOULD BE ON THE WANE. LIKE SOUTHCENTRAL AK...
EXPECTING DRY WEATHER WITH APPRECIABLE SUNSHINE OVERALL IN THE COMING
DAYS. SOME PRECIPITATION FROM THE PACIFIC FRONT SLOWING THROUGH THE
CENTRAL CHAIN WILL BRUSH THE AKPEN LATE WED. THE PARENT LOW LARGELY
STAYS WELL SOUTH OF THE AKPEN HOWEVER...AND THE FRONT WILL BE IN
WEAKENING STAGES BY THE TIME IT ARRIVES SO CONDITIONS ARE NOT
EXPECTED TO DETERIORATE TOO MUCH.

BERING SEA/ALEUTIANS...
THE PACIFIC LOW HAS PEAKED IN INTENSITY EARLY THIS AFTERNOON AND IT
WILL BEGIN FILLING THE NEXT 24 HOURS AS IT TRACKS EAST AND UNDERNEATH
THE CHAIN DUE TO THE SUPPORTING UPPER JET WEAKENING AND PUSHING AWAY
FROM IT. THE FRONT WILL INCH NORTHWARD THROUGH WED...BUT ULTIMATELY
BE THWARTED BY THE STRONG RIDGE AND HIGH TO IT'S NORTHEAST. PRECIP
WILL BE HARD PRESSED TO EVEN REACH THE PRIBILOF ISLANDS. THE NEXT
SYSTEM BEGINS IMPACTING THE FAR WESTERN CHAIN LATE WED NIGHT INTO THU
WITH ANOTHER ROUND OF GALES AND SNOW/RAIN.

.LONG TERM FORECAST...
A BLOCKED UPPER-LVL PATTERN CHARACTERIZES THE LONG TERM FORECAST
PERIOD SAT TO EARLY NEXT WEEK THROUGH THE AOR. AN UPPER-HIGH STILL
SHOULD BE IN THE GENERAL VICINITY OF NW AK/BERING STRAIT THAT LOOKS
TO DOMINATE THE SOUTHERN MAINLAND WITH DRY AND SEASONABLE WEATHER
UNDER SURFACE HIGH PRESSURE. STORM TRACK TO GENERALLY BE SOUTH OF THE
AOR...WITH THE EASTERN HALF OF THE CHAIN TO THE GULF/KODIAK ISLAND ON
THE PERIPHERY OF STORM SYSTEMS. THE FAR WESTERN CHAIN/BERING SEA (AT
LEAST THROUGH THE WEEKEND) WILL HAVE IT'S SHARE OF JET STREAM ENERGY
MIGRATING THROUGH THE AREA ALLOWING FOR MORE ACTIVE WEATHER IN THOSE
PARTS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY FOR BLOWING SNOW...131
MARINE...STORM...172 173 174 176
         GALE...130 131 155 170 171 177 178 179 185 411 412 413 414
         HEAVY FREEZING SPRAY...126 127 130 150 160 180 185 412 414
FIRE WEATHER...NONE

JAM