Small Craft Advisory 161, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST FRI FEB 21 2014

.ANALYSIS AND UPPER LEVELS...
A STORM IN THE CENTRAL BERING IS USHERING IN A NEW LONGWAVE PATTERN.
A RIDGE IS AMPLIFYING AND MOVING INTO MAINLAND ALASKA FROM THE SOUTH.
AT THE SAME TIME...AN UPPER TROUGH IS DEEPENING OVER THE BERING SEA.
BETWEEN THESE FEATURES IS A 125 KT SOUTHERLY JET FEEDING SUBTROPICAL
MOISTURE TO A 964 MB LOW AND FRONTAL SYSTEM CURRENTLY IMPACTING THE
ALASKA PENINSULA AND SOUTHWEST ALASKA. SNOW IS CURRENTLY FALLING
THROUGHOUT BRISTOL BAY AND THE SOUTHERN KUSKOKWIM DELTA.
HOWEVER...WARM AIR IS SURGING NORTHWARD AND WILL BE CREATING AN
INCREASINGLY FAVORABLE THERMAL PROFILE FOR FREEZING RAIN ACROSS THESE
AREAS THIS EVENING. A TIGHT PRESSURE GRADIENT ASSOCIATED WITH THE
FRONT IS QUICKLY INCREASING WINDS ACROSS MUCH OF THE EASTERN BERING
SEA AND SOUTHWEST MAINLAND. MEANWHILE...SOUTHCENTRAL ALASKA IS
EXPERIENCING A SLOW INCREASE IN UPPER LEVEL CLOUDINESS AS THE BERING
SYSTEM EXPANDS NORTHWARD. KODIAK ISLAND AND THE SOUTHERN TIP OF THE
KENAI PENINSULA ARE THE ONLY LOCATIONS SEEING PRECIPITATION FROM THE
FRONT...WHICH WILL LIKELY CONTINUE AS THE FRONT STALLS THIS EVENING.

.MODEL DISCUSSION...
THE MODELS ARE IN GOOD OVERALL AGREEMENT ON THE LARGE-SCALE PATTERN
SHIFT. THE 12Z NAM HAD BEEN TOO AGGRESSIVE BRINGING REMNANT FRONTAL
PRECIPITATION INTO PRINCE WILLIAM SOUND AND UPPER COOK INLET THIS
EVENING...AND THE 18Z NAM HAS COME CLOSER INTO LINE WITH THE DRIER
ECMWF/GFS SOLUTIONS. AS THE FRONT REMAINS STALLED JUST OFF THE COAST
OF THE SOUTHWEST MAINLAND THIS WEEKEND THERE ARE SOME DIFFERENCES
WITH THE TIMING AND STRENGTH OF FAIRLY WEAK SURFACE CIRCULATIONS THAT
WILL MOVE NORTHWARD ALONG THE FRONT. THE MOST SIGNIFICANT IMPACT OF
THESE MODEL DIFFERENCES WILL BE IN HOW STRONG SOUTHEASTERLY WINDS ARE
ACROSS KODIAK ISLAND AND THE BRISTOL BAY AREA SUNDAY NIGHT AND
MONDAY. WEAK FEATURES IN FAST FLOW IS A COMMON SETUP FOR THE MODELS
TO STRUGGLE WITH...AND WILL OPT FOR A CONSENSUS-BASED APPROACH FOR
THE FORECAST WHICH WILL BE FAIRLY SIMILAR TO THE 12Z GFS.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE SOUTHERN MAINLAND WILL REMAIN LARGELY INSULATED
FROM THE EFFECTS OF THE ACTIVE WEATHER OUT WEST. AS MENTIONED
ABOVE...KODIAK ISLAND AND TO A LESSER EXTENT THE SOUTHERN END OF THE
KENAI PENINSULA WILL SEE SEVERAL ROUNDS OF PRECIPITATION OVER THE
COMING DAYS...WITH THE MOST SIGNIFICANT BEING A PROLONGED PERIOD OF
MODERATE TO HEAVY RAINFALL OVER KODIAK ISLAND ON SUNDAY. THE REST OF
THE AREA WILL SEE MORE SUNSHINE THAN RECENT DAYS AS WELL AS DAILY
INCREASES IN TEMPERATURES...EVENTUALLY BECOMING WARMER THAN NORMAL BY
THE START OF THE WEEK.

SOUTHWEST MAINLAND...THE BIG CHALLENGE IS PRECIPITATION TYPE
ASSOCIATED WITH THE FRONT MOVING ONSHORE THIS AFTERNOON. TEMPERATURES
ARE CURRENTLY COLD ENOUGH TO SUPPORT ALL-SNOW AS FAR SOUTH AS KING
SALMON...THOUGH THIS WILL ALL BE CHANGING AS WARM AIR SURGES
NORTHWARD THIS AFTERNOON. THE THERMAL PROFILE WILL EVENTUALLY SUPPORT
FREEZING RAIN AND THEN EVENTUALLY RAIN...BUT THE BIG QUESTION IS IF
THIS WILL HAPPEN IN TIME FOR APPRECIABLE AMOUNTS OF PRECIPITATION TO
FALL AND HAVE AN IMPACT. CURRENT THINKING IS THAT THERE WILL LIKELY
BE A SEVERAL HOUR PERIOD OF FREEZING RAIN NORTH AND WEST OF
DILLINGHAM LATE THIS AFTERNOON...TRANSITIONING UP INTO THE DELTA
DURING THE EVENING. WHILE CONDITIONS WILL IMPROVE TOWARD MORNING
STRONG SOUTHEAST WINDS WILL REMAIN AND CONTINUE THROUGHOUT MUCH OF
THE WEEKEND...ESPECIALLY ALONG THE COAST AND AT HIGHER ELEVATIONS IN
THE ALEUTIAN RANGE.

BERING SEA AND ALEUTIANS...TEMPERATURES HAVE WARMED INTO THE 40S OVER
THE EASTERN HALF OF THE ALEUTIANS AS DEEP MOISTURE TRANSPORT IS
LEADING TO HEAVY RAINFALL RATES OVER THE AREA. THE 964 MB LOW IN THE
SOUTHERN BERING WILL MOVE NORTHWEST TOWARD RUSSIA BY SUNDAY. THIS
WILL LEAVE MOST OF THE REGION IN A FAIRLY SHOWERY PATTERN WITH
COLDEST TEMPERATURES OVER THE WESTERN BERING AND WARMEST TEMPERATURES
IN THE EAST. A FAIRLY NARROW BAND OF STRONG WINDS AND RAINFALL WILL
PERSIST OVER THE EASTERN BERING AS THE RIDGE OVER THE MAINLAND HALTS
ANY PROGRESSION IN THE LONGWAVE PATTERN WELL INTO NEXT WEEK.

.LONG TERM FORECAST...
LONG RANGE MODELS SUGGEST THE NEW PATTERN WILL REMAIN IN PLACE
THROUGH THE END OF NEXT WEEK. THIS WILL KEEP THE MAINLAND IN ABOVE
NORMAL TEMPERATURES AND RELATIVELY DRY CONDITIONS INLAND...WHILE THE
EASTERN BERING AND KODIAK ISLAND REMAINS THE SCENE OF ACTIVE WEATHER.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY 155
         FREEZING RAIN ADVISORY 161
MARINE...STORM 185
         GALE 120 130 131 132 136 137 138 150 155 160 165 170 173 174
              175 176 178 179 180 181 185
FIRE WEATHER...NONE

AMD FEB 14